@article { author = {Sahraei, Hamideh and Alavi, seyed Ahmad and Ehteshami Moinabadi, Mohsen}, title = {Induced seismicity assessment in Salman-Farsi Dam (Ghir), Iran}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {409-426}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.284698.1007137}, abstract = {Nowadays investigating the reservoir induced seismicity phenomenon (RIS) is one of the important subjects because of the extension of dammings in Iran and the potential hazards that they may cause. The phenomenon of dam-triggered earthquakes is known as reservoir-induced seismicity (IRS). It has been expressed through earthquakes with magnitudes ranging from 3 to 6.3 on the Richter scale. For the last 70 years, over 80 cases of RIS have been reported such as Lake Mead, USA, Kremasta, Greece, Oued Fodda in the world and Lar, Latian, Shirin dare, Masjed Soleiman, Karkheh and Karun dams in Iran. Salman-Farsi (Ghir) dam is a two arched gravity concrete dam that is located at 30 km from northeast of Ghir town in Fars province. Geographically, the dam is located at 28° 30ʹ N latitude and 53°15ʹ E longitude. It is situated in Zagros fold-thrust belt zone. This zone is active in the view of seismology and tectonic activates. The lithology of the site dam is mostly limestone with fracture zones in it. The impounding of Salman-Farsi dam started from April 2009 (1st day of Ordibehesht 1388) which has experienced 9 water years after filling up to now. The maximum and minimum entrance annual water amounts are 347 and 125 million m3 belongs to the 1396 and 1392, respectively. We used earthquakes data from Iranian seismological centre (ISC) and dam’s data to study the impoundment effects in 9 years period before and after the filling from 2000 to 2018. The studied region is a circle with 30 km radius from the dam where it is in the centre. The area of this circle is 2826 km2 include 134 earthquakes from 2000 to 2018. There is one historical earthquake with magnitude 7.1 which belongs to 1440 in this region. Statistical results present an increase in seismicity rate change, number of earthquakes, and reduction in the depths and magnitudes of them. The Number of earthquakes after the filing period is 4.7 times more than before it. There are earthquakes with magnitudes ranging from 3 to more than 3 in all stages of loading and unloading. The average depth of earthquakes is 15 km before the reservoir impounding that is reduced to 10 km after it. The growth of seismicity rate changes 7 times more than that before. Comparison of seismic data and reservoir water level fluctuations indicates that between the water level and changes of seismic activity of the area, there is a correlation. Some of the earthquakes have occurred a few days after the reservoir impounding and others have occurred after a monthly period from its first filly time. Based on the evaluation of seismicity in the dam site, most earthquakes have occurred in the vicinity of the reservoir dam and seismic response has been rather fast. Furthermore, we suggest that the occurred earthquakes have an induced seismicity nature. In fact, the reservoir impounding has changed the seismic behaviour of the dam site so that the region experiences more earthquakes with smaller magnitudes. This dam does not have the immigrant behaviour in earthquake locations as some other dams in this region such as Masjed Soleiman, have shown.}, keywords = {Salman-Farsi,Induced Seismicity,Seismic Response,dam,Zagros}, title_fa = {ارزیابی لرزه‌خیزی القایی در سد سلمان فارسی (قیر)، ایران}, abstract_fa = {امروزه لرزه‌خیزی القایی مخزن با توجه به گسترش سدسازی در کشور مورد توجه بسیاری از محققین است. سد سلمان فارسی (قیر) سد بتنی قوسی وزنی در ۳۰ کیلومتری شمال‌شرقی شهرستان قیر استان فارس در ایالت ساختاری زاگرس واقع شده است. در این مطالعه با استفاده از داده‌های زمین‌لرزه‌ای مؤسسه ژئوفیزیک و داده‌های سد، رفتار زمین‌لرزه‌های منطقه در بازة زمانی ۹‌ ساله قبل و ۹‌ساله بعد از آبگیری مورد بررسی قرار گرفته است. نتایج آماری بیانگر افزایش تغییرات آهنگ لرزه‌‌خیزی، افزایش در تعداد و کاهش عمق و بزرگای زلزله‌ها بعد از آبگیری سد می‌باشد. مقایسه داده‌های لرزه‌ای و نوسانات سطح آب مخزن نشان می‌دهد که بین تغییرات سطح آب و فعالیت لرزه‌ای منطقه همبستگی وجود دارد. اغلب لرزه‌خیزی در اطراف محدودة مخزن سد اتفاق افتاده‌است و پاسخ لرزه‌ای از نوع سریع است. بر این اساس ماهیت القایی زمین‌لرزه‌های رخداده در منطقه ساختگاه سد پیشنهاد می‌شود.}, keywords_fa = {Salman-Farsi,Induced Seismicity,Seismic Response,dam,Zagros}, url = {https://jesphys.ut.ac.ir/article_78078.html}, eprint = {https://jesphys.ut.ac.ir/article_78078_aec4c1b7c202392092364e2bf24a30a1.pdf} } @article { author = {Fouladi, Ehsan and Oveisy Moakhar, Mohsen}, title = {Application of 2D Gabor filter in analysis of the aeromagnetic data at Khoram Abad and ground magnetic data at Kashmar regions}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {427-443}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.292361.1007176}, abstract = {Image processing techniques have been used in processing of potential fields data in order to delineate the edges of the anomalous sources. In this research, firstly the 2D Gabor filter was introduced. Then its operation was investigated on the three magnetized prisms which were at the three different depths and orientations. The effects of body wavelength, standard deviation and body orientation in the Gabor filter on the detection of edge bodies were studied. Investigations showed that the Gabor filter is a low pass filter. Afterwards, the Gabor filter was applied on the aeromagnetic data of Khoram Abad region in the southwest and ground magnetic data from Kashmar region in the northeast of Iran. The results show that the trend of geological structures is NW-SE which is in concordance to those obtained from other filters as well as geological map of the region. 1 2D Gabor filter The boundary of the geological structures can be determined by processing of potential field spectrums .Most filters which have been used for edge detection are based on the different degree of derivatives. The derivatives cause noises and signals amplify together which decrease resolution of edges. Therefore, using filters without any derivative terms is a prime objective. The Gabor filter has not any derivative terms in its mathematical structure. Denis Gabor first introduced the filter for image processing. This filter is linear and has been used for analyzing details of an image or its texture. The characteristics of the Gabor filter is to obtain special frequencies in a certain point or a region. Mostly this filter has been used for analyzing human vision system. The Gabor filter has two parts, real and imaginary in exponential forms which are multiplied with a Gaussian function. The real part has been used for data filtering. The Gabor filter response in spatial domain is defined by convolution of data in the Gabor matrix. The Gabor filter is a low pass filter which attenuates noises while it detects the edges of the deep anomalies in a certain direction. The Gabor filter in mathematics is in the group of filter transformation. On this basis, this filter can process images in different directions and frequencies. The Gabor filter has many applications in image processing such as texture analysis, fingerprint detection, edge detection, document processing and so on. The 2D Gabor filter was also used for identification of the edges of the geological structures and faults. For determination of the geological trends and faults, we must apply the Gabor filter in different directions and frequencies and standard deviations. In this article, we first introduce the Gabor filter and its characteristics. Afterwards this filter is applied on the aeromagnetic data from Khoram Abad and ground magnetic from an iron mine at Kashmar regions in the the southwest and northeast of Iran respectively.  2 The real data We prepared the following maps from the real data in Khoram Abad region: the map of the total magnetic intensity, the reduction to the pole of aeromagnetic map and the map resulted from the application of the Gabor filter on the residual aeromagnetic map of the region. From the latter map, the trend and edges of the geological structures were identified. The other trends may be detected by changing the various parameters of the filter specially its direction. The trend of the geological structures which is revealed by the Gabor filter is northwest- southeast. If the Gabor filter is applied with the other edge filters such as derivative of tilt angle, analytic signal filters, we can identify the boundaries better. The Gabor filter on the data from Kashmar region, delineates the boundary of the iron ore body at the studied area.}, keywords = {Gabor filter,Potential Field,Khoram abad,aeromagnetic,low pass filters,Edge detection}, title_fa = {کاربرد صافی گابور دوبعدی در تحلیل داده‌های مغناطیس هوابرد منطقة خرم‌آباد و مغناطیس زمینی در منطقة کاشمر}, abstract_fa = {روش‌های پردازش تصویر در پردازش داده‌های میدان پتانسیل به‌منظور آشکارسازی لبه‌های توده‌های بی‌هنجار مورد استفاده قرار می‌گیرند. در این تحقیق ابتدا صافی گابور دوبعدی معرفی می‌شود. سپس عملکرد صافی گابور بر داده‌های به‌دست آمده از سه منشور مغناطیده که در سه عمق و جهت مختلف قرار گرفته‌اند مورد بررسی قرار می‌گیرد. سپس اثرات تغییر طول‌موج، انحراف‌معیار و جهت‌گیری توده‌ها در عملکرد صافی گابور بر روی داده‌های حاصل از مدل‌های مصنوعی مورد بررسی قرار گرفته‌اند. بررسی‌ها نشان می‌دهند که صافی گابور یک صافی پایین‌گذر بوده و می‌تواند لبة بی‌هنجاری‌های را آشکارسازی کند. در نهایت صافی گابور بر داده‌های مغناطیس هوابرد منطقة خرم‌آباد در جنوب‌غرب ایران اعمال شده است. نتایج نشان می‌دهند که روند ساختارهای زمین‌شناسی در منطقة خرم‌آباد عمدتاً شمال‌غربی-جنوب‌شرقی می‌باشند که در تطابق با نتایجی است که از سایر صافی‌ها به‌دست آمده است. همچنین صافی گابور بر داده‌های زمینی یک تودة معدنی در منطقه کاشمر اعمال و لبة توده بی‌هنجار در این منطقه هم توسط صافی گابور تعیین شد.}, keywords_fa = {Gabor filter,Potential Field,Khoram abad,aeromagnetic,low pass filters,Edge detection}, url = {https://jesphys.ut.ac.ir/article_77990.html}, eprint = {https://jesphys.ut.ac.ir/article_77990_2113f612ad73e399f801f4cd57c44cb4.pdf} } @article { author = {Negahban, Saeed and Ganjaeian, Hamid and Saeedi, Shahla and Ghasemi, Afshan}, title = {Study of vertical displacement caused by 2019 Turkmanchay earthquake based on InSAR method}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {445-456}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.295046.1007182}, abstract = {Large earthquakes are one of the most devastating natural disasters, often resulting in extensive casualties and high mortality, which are considered to be the most significant effects of earthquakes. But earthquakes, in addition to their tangible effects, also have intangible effects that may have long-term effects. In fact, high-power earthquakes cause vertical displacement of the earth by subsidence and uplift, which can adversely affect the residential areas and facilities as well as geomorphological landforms. One of the most recent earthquakes in Iran was the 5.9 earthquake on 2019/11/07 in the Turkmanchay, which caused considerable damage to the settlements in the region and was accompanied by significant vertical displacement. Vertical displacement of the area, in addition to its effects on habitat areas, has a significant impact on groundwater fluctuation, causing problems in groundwater calculations and slope ruptures. For this reason, calculating the vertical displacement rate can be very important. Different methods are used to evaluate the vertical displacement of each area that the radar interferometry is among the best methods. Therefore, the purpose of this study is to evaluate the vertical displacement caused by the Turkmanchay earthquake on surrounding cities using the radar interferometry method. This research is based on analytical-descriptive and software methods. Research data include Sentinel-1 radar images, DEM 30m, and statistical information related to the Turkmanchay earthquake. The software used in the research also includes SNAP (pre-processing and mapping displacement rates), Snaphu (Phase Unwrapping), and ArcGIS (preparing output maps). In this research, the radar interferometry method is used to assess the displacement rate of the study area. Radar interferometry is one of the most powerful tools for monitoring the subsidence phenomenon. This method, by comparing the phases of two radar images of the region taken at two different times, can determine the changes in the surface of the earth at that time interval. The phase taken from a feature on the Earth's surface is proportional to its distance to the radar sensor. Therefore, the change in this distance affects the measured phase. In this research, Sentinel-1 images are used for radar interferometry. The Turkmanchay earthquake occurred on 2019/11/07 near the city of Turkmanchay in Azerbaijan province. The magnitude of the earthquake was reported by various authorities from 5.8 to 6 and its depths up to 10 km. The earthquake also had 610 aftershocks, with the largest one being 4.8, and the closest cities to its hypocenter are Turkmanchay, Mianeh, Turk, Sarab, and Hashtrud. The Turkmanchay earthquake has had many tangible and intangible effects. Due to its magnitude, the earthquake has caused a lot of damage to residential areas including rural areas. One of the tangible effects of the Turkmanchay earthquake was the destruction of residential areas and facilities. The earthquake also caused considerable vertical displacement in the region, given the final map, with a range of 13 to 96 mm. Evaluation of the displacement map of the region indicates that most displacements occurred at the margin of the earthquake hypocenter and, in a general trend, the western areas of the area have experienced subsidence, with a decreasing trend toward the eastern regions and some areas were experiencing uplift. The Turkmanchay earthquake has left many tangible and intangible effects. Among the tangible effects were the destruction of residential areas, with approximately 370 home experienced destruction of between 5 and 100 percent. Also, according to the statistics, 5 people were killed and more than 300 were injured. Among its intangible effects has been the vertical displacement of the area. The results of the evaluation of vertical displacement in urban areas indicate that the city of Sarab with a 41 mm subsidence has the highest vertical displacement. The cities of Turkmanchay, Mianeh, Hashtrud, Turk, Aghkand, and Nair experienced subsidence rates of 30, 3, 28, 18, 14 and 32 mm respectively. In addition to residential areas, geomorphological units have also witnessed a displacement, which can be very important. One of the units where the vertical displacement is very important is the lowland area where the final map shows that the Turkmanchay, Sarab, Hashtrud and Nair plains have been subsided and the Mianeh plain has been uplifted. The vertical displacement in the plains of the area can be effective in fluctuating groundwater and making it difficult to calculate various parameters including the groundwater level drop. Another effect of vertical displacement is the impact on slopes. Given that much of the area is covered by the mountain unit, this displacement can  intensify slope movements in the coming years.}, keywords = {earthquake,vertical displacement,Radar interferometry,Turkmanchay}, title_fa = {مطالعه جابه‌جایی قائم حاصل از زمین‏لرزه 17/8/98 ترکمانچای با استفاده از روش InSAR}, abstract_fa = {زلزله به‌عنوان یکی انواع مخاطرات محیطی محسوب می­شود که با آثار محسوس و نامحسوسی همراه است. یکی از آثار نامحسوس زلزله­ها، جابه‌جایی قائم زمین است که با توجه به تأثیراتی که بر شهرها و لندفرم­های منطقه دارد، ارزیابی آنها می­تواند بسیار حائز اهمیت باشد. با توجه به اهمیت موضوع، در این تحقیق به ارزیابی میزان جابه‌جایی قائم زمین ناشی از زلزله 17 آبان 1398 ترکمانچای به روش تداخل‏سنجی راداری پرداخته شده است. در این تحقیق از ۲ تصویر ماهواره سنتینل ۱ مربوط به یک دورة زمانی ۱۲روزه قبل و بعد از زلزله (۲۸/۱۰/۲۰۱۹ و ۰۹/۱۱/۲۰۱۹) و همچنین روش تداخل‌سنجی راداری استفاده شده است. نرم­افزارهای مورداستفاده در تحقیق نیز شامل SNAP (انجام پیش‌پردازش­های لازم و تهیه نقشه میزان جابه‌جایی)، Snaphu (باز کردن فازها) و ARCGIS‌ (تهیه نقشه­های خروجی) می­باشد. نتایج تحقیق بیانگر این است که تحت‌تأثیر زلزله ترکمانچای، محدوده مطالعاتی با ۱۳+ و ۹۶- میلی­متر جابه‌جایی همراه بوده است. نتیجة ارزیابی جابه‌جایی در نقاط شهری محدودة مطالعاتی بیانگر این است که شهر سراب با ۴۱، ترکمانچای با ۳۰، میانه با ۳، هشترود با ۲۸، ترک با ۱۸، آقکند با ۱۴ و نیر با ۳۲ میلی­متر فرونشست همراه بوده­اند. همچنین نتایج ارزیابی جابه‌جایی در واحدهای ژئومورفولوژی نیز بیانگر این است که جابه‌جایی قائم صورت‌گرفته در دشت­های منطقه می­تواند در نوسان آب­های زیرزمینی و جابه‌جایی صورت‌گرفته در دامنه­ها، می­تواند در تشدید حرکات دامنه­ای در سال­های آتی مؤثر باشند.}, keywords_fa = {earthquake,vertical displacement,Radar interferometry,Turkmanchay}, url = {https://jesphys.ut.ac.ir/article_77999.html}, eprint = {https://jesphys.ut.ac.ir/article_77999_fd9ef9e7e99a854f837e08e7a97891bf.pdf} } @article { author = {Serajamani, Masoud and Nikrouz, Ramin and Kadkhodaie, Ali}, title = {Estimation of Brittleness Index Using Post-Stack Inversion of Seismic Data: Example from Perth Basin in Western Australia}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {457-471}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.295601.1007188}, abstract = {Brittleness is one of the most important properties of the rock. Brittleness is a function of strength and indicates rock strength to deformation in the elastic modules. However, there is no direct and standard method for brittleness measurement but it can be done indirectly by using rock properties such as different ratios of compressive strength and tensile strength of rock to determine the concept of brittleness. The purpose of this study is to investigate the concepts of brittleness which are presented by the researchers and to use seismic inversion, multi-attribute analysis and neural network in the Whicher-Range field in Perth, Western Australia to estimate brittleness. The Perth sedimentary basin stretches about 100,000 square kilometers in the north-south direction of the western Australian margin. About half of this sedimentary basin is located 1 km deep in the sea. Whicher-Range gas field is 22 km south of Baselton and 200 km south of Perth. Two wells and one seismic section of Whicher-Range field are selected in this research. The lowest brittleness indexes in the first and second wells drilled 1 km apart, are 1.69 and 1.67 MPa using criteria. The highest values of the brittleness are 39.78 and 48.15 MPa, respectively, which are difficult for drilling. The starting point of the inversion process is to have post-stack seismic data, velocity model, well logs, and seismic horizons. The product of the density log and sonic velocity is equal to the impedance. Then the current impedance is converted from depth to time using the appropriate depth to time relation. As a result, the convolution of a suitable wavelet and reflectivity over time will produce the synthetic seismic trace. Adaptation rate between synthetic seismic trace and composite field seismic trace yields an acceptable result. Next, the initial modeling is performed using wavelet, geological model, and a model-based algorithm. Next, the acoustic impedance of the inversion process along with other attributes is used to construct the optimal combination of attributes to estimate the brittleness index. First, an attribute is selected that has the highest correlation with the target log and the least estimation error in the training step. Then the second attribute, which makes the best combination with the first attribute, has the lowest estimation error. Then each attribute step is added to its previous step combination until the resulting combination results in the lowest estimation error. The results based on this method are obtained by increasing the number of attributes and decreasing the estimation error, while the error in the validation stage until the optimal attribute combination, is ascending. In the next step, three types of neural network algorithm including probabilistic method, multi-layer feed forward and radial basis function are used to estimate the target parameter, with optimal combination of available attributes and the use of neural network algorithm training from the optimal attributes using the Hampson-Russell software. In the last step, multi-attribute analysis is compared with three neural network algorithms. The results indicate a higher correlation coefficient for probabilistic neural network than that of multi-attribute analysis for determination of the brittleness index.}, keywords = {Brittleness Index,compressive strength,inversion,seismic attributes,neural network,Perth Australia}, title_fa = {تخمین شاخص شکنندگی با استفاده از وارون‌سازی پس از برانبارش داده‌های لرزه‌ای با مثالی از حوضة پرت واقع در استرالیای غربی}, abstract_fa = {شکنندگی یکی از مهم‌ترین خصوصیات سنگ می­باشد. تاکنون روشی مستقیم و استاندارد برای به‌دست آوردن شاخص شکنندگی ارائه نشده است. از شاخص شکنندگی بر اساس پارامترهای مقاومت فشارشی تک‌محوره و مقاومت کششی جهت ارزیابی شکنندگی استفاده می­شود. هدف از این مطالعه بررسی مفاهیم شکنندگی ارائه‌شده توسط محققین و استفاده از روش وارون‌سازی لرزه­ای، آنالیز چندنشانگری و شبکة عصبی در میدان ویچررنج (Whicher-Range) واقع در حوضة پرت (Perth Basin) استرالیای غربی می‌باشد. به این منظور دو چاه و یک مقطع لرزه­ای از میدان ویچررنج مورداستفاده قرار گرفت. کمترین شاخص شکنندگی در چاه اول و دوم که با فاصله 1 کیلومتری از هم حفاری شدند، به‌ترتیب با استفاده از مفهوم  برابر 69/1 و 67/1 مگاپاسکال که بیانگر شکنندگی کم و بیشترین مقدار آن برابر 78/39 و 15/48 مگاپاسکال که بیانگر شکنندگی زیاد و از نظر حفاری در رتبة حفاری بسیار سخت می­باشد. در مرحلة بعد با استفاده از استخراج موجک و رسم مدل زمین‌شناسی، مدل‌سازی اولیه انجام و سپس امپدانس صوتی حاصل از فرایند وارون‌سازی در کنار دیگر نشانگرها در راستای ساخت ترکیب بهینه از نشانگرها جهت تخمین شاخص شکنندگی استفاده شد. از سه نوع الگوریتم شبکة عصبی جهت تخمین پارامتر هدف از ترکیب بهینه نشانگرهای موجود استفاده می­شود که به‌کمک نرم‌افزار همپسون–راسل و نشانگرهای بهینه­ای، الگوریتم شبکة عصبی تهیه و در نهایت آنالیز چند نشانگری با سه الگوریتم شبکة عصبی مقایسه می‌شود و نتایج بیانگر ضریب همبستگی بیشتر شبکة عصبی احتمالی نسبت به آنالیز چند نشانگری جهت تعیین شاخص شکنندگی است.}, keywords_fa = {Brittleness Index,compressive strength,inversion,seismic attributes,neural network,Perth Australia}, url = {https://jesphys.ut.ac.ir/article_77986.html}, eprint = {https://jesphys.ut.ac.ir/article_77986_853a4a10e86f84d90a8843bab98a939b.pdf} } @article { author = {Farzaneh, Saeed and Sharifi, Mohammad Ali and Naderi, Kosar}, title = {Time-series analysis of GPS measurements for modeling and estimating bridge movements using Neural Network model: Case study, Tabiat Bridge}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {473-495}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.299519.1007200}, abstract = {One of the parameters that can be used to predict different types' behavior of civil structures is the displacement components, extracted from structures. Bridges and their health monitoring system are important parts of the land transportation system because of their safety and durability. This study aims to evaluate the safety behavior of the Tabiat pavement bridge using a high-rate geodetic monitoring of the Global Positioning System (GPS). Accurate orbital information (SP3) is also used to process the collected observations as well as the Double Difference Bernese software. Firstly, the data are processed kinematically, using the coordinate conversion system, into the local coordinates of the bridge (N, E, and H). At the beginning, the raw data is pre-processed using the Kalman filter to reduce noise. The time series of GPS observations are estimated with 0.0013 m accuracy by applying the Kalman filter with CWPA method. Afterwards, the MA filter, mean time zone and Median filter are used to estimate the semi-static, static and dynamic components of bridge movements, respectively. The results obtained by applying the MA filter indicate that the semi-static component is extracted with 0.005 m accuracy in the North, 0.003 m in the East and 0.01 m in the Height directions. The Median filter also estimates the dynamic component with precision of 0.0007, 0.0006 and 0.001 m in three directions N, E and H, respectively. In this study, considering the sampling rate of observations, the average of 5 minutes of semi-static movement is considered as a static behavior of each point. In order to extract the dominant frequencies of the bridge, the least squares harmonic estimation (LSHE) method is used. Finally the Artificial Neural Network model (ANN) with 5 hidden layers and 5 delays is used to predict bridge deformation based on data mining. The frequencies at points on the bridge are approximately similar, which shows the similarity of the periodogram to the high hardness of the bridge. In addition, the frequencies in both North and East directions, relative to Height direction, indicate the GPS sensitivity to load effects. The prediction model using the artificial neural network is then fitted to dynamic component, with accuracy of approximately 6×10-5m and 4×10-5m to the dynamic and semi-static components of the bridge motion, respectively. Both the least squares harmonic estimation method and the ANN model are considered as suitable techniques for estimating the performance changes of GPS measurements in the frequency and time domains during the monitoring time period. The results indicate that the bridge behavior safety design range the minimum changes using GPS measurements in the time and frequency domains. Besides, the frequency analysis of the bridge movement time series and the neural network model, can be used to detect significant frequency changes and study the bridge performance rigidity, respectively. These results show that high-frequency satellite geodetic data which properly processed can also be useful for measuring the dynamic displacements of tall buildings, cable-stayed bridges, flexible and rigid civil structures. Also they would be the bases of bridge safety monitoring system primary warning.}, keywords = {Movement of Bridge,Structural Health Monitoring,GPS,LSHE method,Deformation prediction,ANN model}, title_fa = {آنالیز سری زمانی مشاهدات GPS جهت برآورد و مدل‌سازی حرکت پل مطالعه موردی: پل طبیعت}, abstract_fa = {مؤلفه­های جابه­جایی استخراج شده از سازه­ها، یکی از پارامترهای مهم پایش سلامت ساختاری است که می­توان از آنها جهت پیش‌بینی رفتار انواع مختلف سازه­های بشری از جمله پل­ها استفاده کرد. این مطالعه با هدف ارزیابی رفتار ایمنی پل پیاده‌رو طبیعت، با استفاده از پایش ژئودتیکی با نرخ 30 ثانیه از سیستم GPS انجام شده­است. به‌منظور ارزیابی حرکت پل از پالایه کالمن، پالایه MA، میانگین زمانی و پالایه Median به‌ترتیب جهت کاهش نوفه مشاهدات، برآورد مؤلفه­های نیمه­استاتیک، استاتیک و دینامیک حرکت پل استفاده شده­است. نتایج به‌دست‌آمده از اعمال پالایه MA نشان می­دهد که مؤلفة نیمه­استاتیک با دقتی برابر با 005/0 متر در راستای North، 003/0 متر در راستای East و 01/0 متر در راستای Height استخراج شده­است. همچنین RMSE بین مؤلفة دینامیک به‌دست‌آمده و مؤلفة پریودکوتاه نیز برابر با 0007/0، 0006/0 و 001/0 متر به‌ترتیب در سه جهت N، E و H می­باشد. فرکانس­های غالب حرکت پل، با استفاده از روش LSHE برآورد شده­اند و در نهایت مدل شبکه عصبی مصنوعی با تعداد 5 لایه پنهان و 5 تأخیر، جهت پیش­بینی تغییرشکل پل، بر اساس داده­های استخراج شده و ارزیابی دقیق مؤلفه­های متغیر با زمان ارائه شده‌است. نتایج حاصل بیانگر آن است که رفتار پل در محدودة ایمنی طراحی آن، دارای حداقل تغییرات مشاهده شده برای اندازه‌گیری­های GPS در حوزه­های زمان و فرکانس می­باشد. همچنین آنالیز فرکانسی سری زمانی حرکت پل و مدل شبکه عصبی به‌ترتیب می­توانند برای تشخیص وکشف تغییرات قابل‌توجه فرکانس و پیش­بینی رفتار پل، جهت بررسی استحکام آن مورد استفاده قرار گیرند.}, keywords_fa = {Movement of Bridge,Structural Health Monitoring,GPS,LSHE method,Deformation prediction,ANN model}, url = {https://jesphys.ut.ac.ir/article_77991.html}, eprint = {https://jesphys.ut.ac.ir/article_77991_6103ecf71420877a7218ad39bb981e36.pdf} } @article { author = {Farzaneh, Saeed and Sharifi, Mohammad Ali and Akbarzadeh, Atefeh}, title = {Investigation of short-term atmospheric mass variations and their effects on geoid height using meteorological data}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {497-515}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.299685.1007203}, abstract = {Modern missions such as CHAMP, GRACE and GOCE which derive the Earth’s static and time-variable gravity field with unprecedented accuracy with monthly or even sub-monthly resolution, are also sensitive to short-term (weekly or shorter) non-tidal mass variations due to mass transports and mass redistribution phenomena in the atmosphere, the oceans and the continental water storage. GRACE derived gravity solutions contain errors mostly due to instrument noise, anisotropic spatial sampling and temporal aliasing caused by incomplete reduction of short-term mass variations in models. Improving the quality of satellite gravimetry observations, in term of using more sensitive sensors and increasing the spatial isotropy, has been discussed in the context of the designed scenarios of GRACE-Follow On (GRACE-FO) mission. Temporal aliasing is still a factor that affects the quality of the gravity field. For GRACE data processing only the short-term variations are of importance, because with the monthly Grace gravity field solutions it is planned to provide data for determination of the seasonal variations. Short-term mass variations cannot be measured adequately by GRACE. Therefore they are removed from measurements beforehand using geophysical models (de-aliasing). This paper specifically focuses on the atmosphere of Earth and its mass variations using the ITG-3D method. In this paper, various type of data such as the atmospheric pressure parameter, the multilevel geopotential, temperature and humidity parameters from European Center for Medium-Range Weather Forecasts (ECMWF) have been used to perform three-dimensional integral solution. ERA-Interim and ERA5 reanalysis are considered as the datasets. In the procedure of calculations, the shape of earth is approximated as an ellipse. As a first step in calculation procedure, it is necessary to remove the effect of long-term variations. In order to eliminate this effect; the mean variations of atmospheric mass over a specific period should be subtracted from the mass variation. Atmospheric de-aliasing products can be illustrated as sets of spherical harmonic coefficients, which are estimated using atmospheric mass variations. Then, the effect of atmospheric mass changes on geoid height and vertical deformation were calculated. In the computation, the ECMWF data on 1 January 2015 at 00:00h were used, while the mean atmospheric mass variations were derived from the means of the years 2015 and 2016. The results of the comparison between two datasets demonstrated that the maximum differences in parameters are located in Asia and Antarctic. The results indicate that the mean of difference between atmospheric mass variations from ERA-Interim and ERA5 is 0.23 kgm-2. The results show that the difference between the coefficients is about one percent of their values. In addition, the geoid height from ERA5 changes on average of -0.16 cm whereas this parameter varies on average -0.17 cm using ERA-Interim data due to atmospheric mass variations. The difference of vertical deformation from two datasets is -0.002 cm on average. The atmospheric mass variations calculated by the two data sets (ERA-Interim and ERA5) is not significantly different. The validation results of the vertical deformation of the two data also show a high correlation with the GPS time series.}, keywords = {atmospheric mass variations,ERA-Interim,ERA5,Aliasing,de-aliasing}, title_fa = {مقایسة مجموعه داده‌های ERA5 و ERA-Interim در محاسبة تغییرات جرم کوتاه‌مدت جوی و اثرات آن بر ارتفاع ژئویید}, abstract_fa = {میدان گرانی حاصل از مشاهدات گرانی‌سنجی ماهواره‌ای مانند GRACE شامل خطاهایی ناشی از نوفة دستگاهی، نمونه‌برداری مکانی ناهم‌سانگرد (anisotropic) و خطای تداخل سیگنال (aliasing) و زمانی ناشی از نقص مدل‌سازی تغییرات جرم کوتاه‌مدت زمین است. کیفیت مشاهدات GRACE در مأموریت GRACE-FO بهبود یافت، اما خطای تداخل سیگنال زمانی همچنان یک عامل تأثیرگذار بر گرانی محاسباتی از مشاهدات می‌باشد. به همین دلیل محاسبه تغییرات جرم کوتاه‌مدت و تصحیح اثر این تغییرات بر مشاهدات جرم ماهواره‌ای و به بیان دیگر تصحیح خطای تداخل سیگنال (de-aliasing) ضروری می‌باشد. این پژوهش بر بخش جو زمین تمرکز کرده و تنها تغییرات جرم جوی فرکانس بالا را با راه‌حل انتگرال‌گیری سه‌بعدی، با در نظرگرفتن جو سه‌بعدی و پارامترهای جوی سطحی و چند سطحی حاصل از مدل عملیاتی ECMWF و مجموعة داده‌های دوباره آنالیز شده ERA-Interim و ERA5 با پوشش جهانی محاسبه می‌کند. همچنین ضرایب هارمونیک کروی تحت‌اثر این تغییرات محاسبه و اثر تغییرات جرم جوی بر تغییرات ارتفاع ژئویید و تغییرشکل قائم زمین بررسی شد. مقایسة تغییرات جرم حاصل از دو داده بیانگر اختلاف کم و نزدیک به صفر بین دو داده می‌باشد. همچنین اثر این تغییرات جرم بر نوسان ژئویید و تغییرشکل قائم زمین بسیار ناچیز است. بیشینة ضریب همبستگی 70 درصد بین تغییر شکل حاصل از سری زمانی GPS و تغییر شکل حاصل از دو مجموعه داده بیانگر اعتبار نتایج به‌دست آمده می‌باشد.}, keywords_fa = {atmospheric mass variations,ERA-Interim,ERA5,Aliasing,de-aliasing}, url = {https://jesphys.ut.ac.ir/article_77992.html}, eprint = {https://jesphys.ut.ac.ir/article_77992_085a855984cbd9a5c939b42cc1e74bac.pdf} } @article { author = {Ramouz, Sabah and Safari, Abdolreza}, title = {Assessment of the Improved Covariance in Local Geoid Modeling Using Least Squares Collocation-Case study: Tehran Province}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {517-535}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.303845.1007221}, abstract = {The idea of using Improved covariance (I_COV) through Least Squares Collocation (LSC) was first introduced and assessed on gravity anomalies (Ramouz et al, 2020) and geoid heights (Heydarizadeh et al, 2020) modeling over four regions with different data distribution and topography patterns in Iran. The results of these two researches showed that using I_COV could enhance gravity field modeling, specifically the medium to short wave-lengths of the signal which are embedded in the local and near-surface masses and surface density anomalies. For instance, implementing I_COV on a region with rough topography is more effective than classic covariance, in comparison with regions with smooth topography. The gravity and GNSS/Leveling networks of Iran suffer from the lack of sufficient and well distributed observations. Moreover, existence of Alborz and Zagros mountain chains and the rough topography in the North, South and West of Iran, make regional gravity modeling that cover the whole country a difficult task. On the other hand, thanks to the development in satellite gravity technology and observations that have improved the accuracy of long-wavelength modeling of the Earth gravity field. So, quality processing and densifying terrestrial observations, incorporating high resolution Digital Elevation Models (DEM)s and improving geodetic boundary value problems are the available solutions to extract the medium to short-wavelength of the gravity signal to improve the gravity modeling. In this way, investigation of the effect of area size selection of the terrestrial observations, data density and distribution and topography roughness is classified in the spatial localization of the gravity field modeling. The goal of this research is to analysis the contribution of the observations’ area size, density and distribution parameters on the accuracy of the local geoid height modeling and assess the possibility of model enhancement through execution I_COV procedure via LSC algorithm. As input, EIGEN-6C4 Global Gravity Model (GGM) up to degree/order 360, terrestrial gravimetric observations inside and around Tehran Province (measured by National Cartographic Center of Iran) and SRTM-1arc-min DEM are used via Remote-Compute-Restore technique. To determine the analytical covariance function in order to applying LSC, first, an empirical covariance is computed from the terrestrial observations. Then, the Tscherning-Rapp 1974 (TR1974) covariance function is fitted to the empirical one and its three parameters are estimated to calculate the auto and cross-covariance of the LSC modeling formula. After LSC, the systematic parts of the signal i.e. global and topographic effects are restored. To implement the I_COV idea in gravity field localization, the value selection of TR1974 parameters are entered in iterative process to enhance the covariance model and improve the accuracy of the local model. Assessment of the computed local model with the 141 GNSS/Leveling control points (measured by NCC) illustrates that STD of the model is about 8.9 cm inside the case study. Furthermore, if the comparison is limited to 40 control points inside Tehran City, STD of the model will be about 6.1 cm. To draw a comparative picture, the accuracy of this local model is 49% and 51% higher than EGM 2008 model (which has been the most accurate GGM in the region so far) over the same control points.}, keywords = {Least Squares Collocation,Earth gravity field localization,Geoid height,Remove-Compute-Restore,EGM2008}, title_fa = {ارزیابی تابع کووریانس بهبودیافته در مدل‌سازی ژئوئید محلی به‌روش کالوکیشن کمترین مربعات- منطقه مطالعاتی: استان تهران}, abstract_fa = {در پژوهش پیش ‌رو، جهت رفع محدودیت‌های ناشی از عدم‌وجود شبکه گرانی متراکم و پراکندگی نامناسب مشاهدات گرانی‌سنجی زمینی در محدودة ایران و افزایش دقت مدل‌سازی محلی ژئوئید صرفاً گرانی، از مشاهدات GNSS/Leveling در فرایند بهینه‌‌سازی پارامترهای تابع کووریانس استفاده شد. در این‌ مقاله، علاوه بر پیاده‌سازی ایده کووریانس بهبودیافته، تأثیر پارامترهای وسعت محدوده، تراکم و کیفیت پراکندگی مشاهدات بر مدل‌سازی محلی ارتفاع ژئوئید بررسی شد و ارزیابی نتایج آن حاکی از افزایش دقت مدل‌سازی محلی ژئوئید به زیر 9 سانتی‌متر در محدودة استان تهران و در شهر تهران بزرگ به ۶ سانتی‌متر در مقایسه با نقاط کنترلی و به‌ترتیب، متناظر با ۴۹ و ۵۱ درصد بهبود در مقایسه با مدل جهانی EGM2008 می‌باشد. در این مطالعه، مشخص شد که استفاده از کووریانس بهبودیافته موجب کاهش حساسیت دقت مدل به‌ پارامتر وسعت و وضعیت پراکندگی مشاهدات زمینی گشته که به‌ویژه برای مناطقی مانند ایران-به‌دلیل محدودیت در کیفیت پراکندگی و تراکم مشاهدات-که انتخاب محدوده مناسب برای مدل‌سازی محلی میدان گرانی امر چالش‌برانگیزی‌ست، می‌تواند کاربرد داشته باشد.}, keywords_fa = {Least Squares Collocation,Earth gravity field localization,Geoid height,Remove-Compute-Restore,EGM2008}, url = {https://jesphys.ut.ac.ir/article_78381.html}, eprint = {https://jesphys.ut.ac.ir/article_78381_dadd3def3082b49fc0860cf836b81e9c.pdf} } @article { author = {Mirzayi Hasanlo, Ayub and Abghari, Hirad and Erfanian, Mahdi}, title = {The effect of teleconnection patterns on rainfall and drought in the Urmia Lake basin}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {537-559}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.292304.1007175}, abstract = {Rainfall is one of the most important meteorological quantities, and a decrease in its mean natural value over a period of time causes drought. Therefore, understanding the annual and intra-decade changes is important to improve water resources planning and management. One of the main approaches for preventing climate crises is to analyze the causes and factors that cause such climate variations and be aware of and anticipate the occurrence of climate hazards. Climate patterns are defined as the simultaneous relationship between the oscillations of the climatic elements of a place with changes in pressure patterns and sea surface temperature at other geographical locations. The aim of this study is to investigate rainfall and drought identification of Urmia Lake basin and the effect of some teleconnections patterns (NAO, EA, SOI) on climatic conditions and climatic factors such as rainfall and SPEI drought using wavelet correlation. In this study, 8 synoptic stations of Urmia Lake basin are selected in a period of 29 years, then the trends of rainfall and drought are determined using non-parametric tests. Then the effects of teleconnection patterns (NAO, EA, SOI) on rainfall and drought in Urmia Lake basin are determined using wavelet correlation. The results showed that in the studied stations, the highest rainfall is in spring, winter, autumn and summer, respectively. The annual drought study using the SPEI index in the studied stations showed that the most severe droughts occurred in 1990, 2017, 2008 and 2010 and the most severe droughts occurred in 1993, 1994 and 1995 at the basin level. The results of trend analysis showed that transpiration evaporation in all stations except Takab station has an upward and significant trend at the level of 95% and Mahabad and Tabriz stations have an increasing slope and significant compared to other stations. Also, the trend of rainfall showed that rainfall only in Tabriz, Urmia and Takab stations had an upward trend and in other stations there were downward trends that in none of the stations a significant upward and downward trend was observed. An examination of the SPEI annual drought trend showed that the drought in Urmia and Ahar stations has been on an upward trend and in other stations it has been declining. The correlation between rainfall and index (EA) in the studied stations showed that there was a negative correlation in all the studied stations on an annual scale. In the negative phases of EA, the monthly rainfall showed positive values and the EA index has changed the rainfall. Also, the results of the correlation between rainfall and NAO in the studied stations showed that there was a positive correlation in all stations. Also, for Urmia, Tabriz, Takab, Saqez, Sahand and Mahabad stations correlations were significant at 99%, and Ahar station is significant at 95%. The results showed that the NAO time series has affected the changes in the rainfall time series. The results of the correlation between rainfall and SOI showed that there was a negative correlation between the indicators, which was significant at Mahabad station at 95%. These indicate that SOI has affected the changes of rainfalls. The correlation results between SPEI drought index and teleconnection patterns showed that NAO index had positive and significant correlation and EA and SOI index had negative correlation with monthly drought values. Due to the fact that the Urmia Lake basin is semi-arid in terms of climate, determining the relationship between rainfall and drought with the patterns of distant links plays an important role in planning water resources, especially droughts for preventing damage. In this study, the results of rain wavelet correlation with NAO, SOI, EA bonding patterns of stations studied on an annual scale indicate that NAO index has a positive and significant correlation in which rainfall decreases in its negative phase and with decreasing values of NAO index. Also in the negative phase of NAO, the high-pressure centers of Siberia and Azores and the low pressure of Iceland are weakened, which causes less pressure of the Siberian high-pressure extention to wards the basin, and consequently the amount of precipitation decreases significantly. However, the two indicators of SOI and EA have negative correlations, which have increased the negative phase of rainfall, and the changes of the two indicators are effective on the changes of rainfall. The results showed that the impact of NAO on rainfall and drought on the surface of the basin was higher than SOI and EA. Due to the fact that rainfall and drought in the Urmia Lake basin have been correlated with some of these teleconnections identifying the factors affecting rainfall and drought and predicting their total amount or trend has a significant role in planning and developing water resources.}, keywords = {Telecommunication patterns,Continuous wavelet transform,cross wavelet transform,Drought,Lake Urmia}, title_fa = {تأثیر الگوهای دورپیوند بر بارش و خشکسالی حوضة دریاچة ارومیه}, abstract_fa = {داشتن شناخت لازم از اثر الگوهای دورپیوند و پیش‌بینی آنها خصوصاً در دوره‌های خشکسالی، کمک به‌سزایی در جهت برنامه‌ریزی دقیق‌تر در حوضة آبخیز خواهد داشت. هدف تحقیق حاضر، تأثیر الگوهای دورپیوند بر خشکسالی و بارش ایستگاه‌های همدیدی حوضة دریاچة ارومیه می‌باشد. در این پژوهش تغییرات بارندگی، تبخیر تعرق و خشکسالی هواشناسی با استفاده از روش‌های ناپارامتریک من کندال و شیب سن مورد بررسی قرار گرفت. مطالعة داده‌های 8 ایستگاه همدیدی حوضة دریاچة ارومیه نشان داد که تبخیر تعرق همواره روند صعودی و معنی‌داری (به‌جز تکاب) دارند؛ اما بارندگی و خشکسالی رفتاری متفاوت در ایستگاه‌ها دارند به‌طوری‌که بارندگی در ایستگاه‌های تبریز، ارومیه و تکاب روند صعودی و در سایر ایستگاه‌ها روند نزولی و غیرمعنی‌داری داشته است.با استفاده از تحلیل همبستگی موجکی، حرکت دوبه‌دوی بین الگوهای دور پیوند (SOI، NAO، EA) با بارندگی و خشکسالی SPEI برای بازة زمانی1990 تا 2018 با دورة ماهانه مورد بررسی قرار گرفت. نتایج این بررسی‌ها نشان داد که شاخص NAO داری بیشترین همبستگی مثبت با بارش بوده، و بیشترین تأثیر بر بارش و خشکسالی حوضة دریاچة ارومیه داشته که در فاز مثبت بارندگی زیاد شده است. همچنین دو شاخص EA،SOI  داری همبستگی منفی و معکوس با بارش و خشکسالی SPEI بوده است، بنابراین نتایج نشان داد تغییرات الگوهای دور پیوند بر تغییرات سری زمانی بارش و خشکسالی مؤثر بوده است. این یافته‌ها از تغییرات و تأثیر الگو‌های دور پیوند بر بارش و خشکسالی می‌تواند در مدیریت ریسک خشکسالی و برنامه‌ریزی برای کاهش خسارات خشکسالی به مدیران اجرایی مفید باشد.}, keywords_fa = {Telecommunication patterns,Continuous wavelet transform,cross wavelet transform,Drought,Lake Urmia}, url = {https://jesphys.ut.ac.ir/article_77985.html}, eprint = {https://jesphys.ut.ac.ir/article_77985_cd9e2d87bb9a3e77ac4a582f91a08144.pdf} } @article { author = {Pahlavan, Razieh and Moradi, Mohammad and Tajbakhsh, Sahar and Azadi, Majid and Rahnama, Mehdi}, title = {Numerical prediction of several radiation and CBL fog events over Iran using the WRF model for late December 2015}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {561-582}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.299678.1007202}, abstract = {In this study it has been attempted to simulate the occurrence of radiation and CBL fog during late December 2015 in Orumiyeh, Arak, Bushehr, Zahedan, Hamedan and Shahrekord airports, using the mesoscale WRF model. To simulate radiation and CBL fogs, the output of the WRF model with five different configurations as presented in table 1 was used, and then four visibility calculation algorithms were applied to the output of the model to find the best configuration and visibility calculation algorithm for the prediction of the considered fog events. The WRF model version 3.9.1 with Lambert conformal projection, using two nested domains with 16-km and 4-km grid spacing was used for the simulation. Based on the results of some previous studies (e.g. Lin et al., 2017; Van der Velde et al., 2010; Roman-Casc´on et al., 2012), because of the sensitivity of the fog prediction to cloud microphysics, planetary boundary layer and long-wave radiation schemes, five different configurations of the WRF model with varying physical parametrization schemes were implemented. In the first series of experiments, the five mentioned configurations of the model were run using 28 vertical levels. Then four horizontal visibility calculation algorithms including SW99 (Stoelinga and Warner,1999), FSL (Doran et al., 2009), G2009 (Gultepe et al., 2009) and RUC (Benjamin et al., 2004) were applied on the model output to calculate the horizontal visibility separately for each model output and for six synoptic stations in the domain. It is seen that, since the amount of liquid water content (LWC) of the cloud with all model configurations is zero or nearly zero, the calculated horizontal visibility was much greater than 10 km for all stations. In general, the model showed poor results for the simulation of relative humidity in the boundary layer and thus the occurrence of fog. Since some previous studies (e.g. Yang and Gao, 2016; Philip et al., 2016; Tardif, 2007) have emphasized the importance of high vertical resolution to resolve the main fog formation processes, in the next series of experiments the number of vertical levels in the model was increased from 28 to 32, such that 11 vertical levels were considered from the ground level up to 200 m above ground. The model was then implemented with the same five configurations as in the first experiments. Examining the results revealed that the model found the skill of recognizing moisture and fog in most cases, and predicted 5 out of 6 cases of CBL and 2 out of 4 cases of radiation fogs. For the verification the outputs for the predictions of fog events the calculated visibilities were compared with the verifying observational data and hit rate and equitable threat score were calculated. The evaluation indicated that the configuration 2 with 32 vertical levels combined with SW99 and G2009 algorithms performed better for the prediction of visibility for stations considered here. It can also be said that increasing the number of vertical levels close to the surface is of great importance in improving the quality of fog forecasting, because high vertical resolution is required to realistically represent the vertical structure and magnitude of the radiative cooling in the first few meters of the atmosphere, and thus obtain more accurate forecasts of radiation fog. Using high vertical resolution in simulations, results in an acceptable increase of liquid water content (LWC) and thus improves the accuracy of fog prediction. The results also show that the model's skill to predict CBL fog is higher than that of radiation fog in this case study. By comparing the simulated and observational two meter temperature values, it was observed that the simulated air temperature is overestimated, especially for the radiation fog. Previous researches have also shown a positive bias in predicted air temperature at two-meter height in radiation fog conditions, which is probably due to the inability of the model to simulate the actual radiative cooling associated with fog conditions in the first few meters of the atmosphere (Roman-Casc´on et al., 2019).}, keywords = {Numerical Prediction,Radiation fog,CBL fog,WRF model,Vertical levels}, title_fa = {پیش‌بینی عددی چند رخداد مه تابشی و CBL با استفاده از مدل WRF روی برخی مناطق ایران: مطالعه موردی، 27 تا 31 دسامبر سال 2015}, abstract_fa = {در این مطالعه رخدادهای مه تابشی و مه ناشی از کاهش ارتفاع کف ابر موسوم به مه CBL‌ (Cloud-Base Lowering) از 27 تا 31 دسامبر 2015 که در ایستگاه‌های هواشناسی فرودگاه‌های ارومیه، اراک، بوشهر، زاهدان، همدان و شهرکرد ثبت شده است، با استفاده از مدل میان مقیاس WRF شبیه‌سازی شده است. برای این منظور، مدل میان مقیاس WRF با 5 پیکربندی متفاوت و 28 تراز قائم اجرا شد. سپس با به‌کارگیری چهار الگوریتم محاسبه دید افقی شامل SW99، FSL، G2009 و RUC روی برونداد مدل، دید افقی محاسبه شد. بررسی نتایج نشان داد که مدل نمی‌تواند مقدار نم نسبی لایه مرزی و در نتیجه رخداد مه را شبیه‌سازی کند. با افزایش تعداد ترازهای قائم مدل در لایه 200 متری مجاور سطح زمین، دیده شد که مهارت مدل در پیش‌بینی رخداد مه افزایش یافت و از 6 مورد مه CBL و 4 مورد مه تابشی به‌ترتیب 5 و 2 مورد رخداد مه پیش‌بینی شد. آزمایش‌های مختلف اهمیت تعداد ترازهای قائم در مجاورت سطح زمین و نقش آن در کیفیت پیش‌بینی مه را مشخص کرد. همچنین نتایج کلی نشان داد که کاریی مدل در پیش‌بینی مه CBL نسبت به مه تابشی بیشتر ‌است.}, keywords_fa = {Numerical Prediction,Radiation fog,CBL fog,WRF model,Vertical levels}, url = {https://jesphys.ut.ac.ir/article_77993.html}, eprint = {https://jesphys.ut.ac.ir/article_77993_3496aec0e62fc7d2110c1e89fe851050.pdf} } @article { author = {Zarrin, Azar and Dadashi Roudbari, Abbas Ali}, title = {Projection the Long-Term Outlook Iran Future Temperature Based on the Output of The coupled model intercomparison project phase 6 (CMIP6)}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {583-602}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.304870.1007226}, abstract = {The Intergovernmental Panel on Climate Change (IPCC) has stated that climate change is undoubtedly real and greenhouse gas emissions continue to heat up all components of the climate system (IPCC, 2013). In this study, we have addressed two main concerns:  First, we assessed the performance of temperature simulations of the available CMIP6 and next, we projected future temperature in Iran by underlying socioeconomic scenarios by the late 21th century. In this study, the average annual temperature data of 43 synoptic stations were obtained for the period of 1980-2018. Also, the latest Coupled Model Intercomparison Project phase 6 (CMIP6) dataset was analyzed to examine the projected changes in temperature over Iran during the twenty-first century. Three available CMIP6 models used in this study including BCC-CSM2-MR, CAMS-CSM1-0, and MRI-ESM2-0. To project the temperature anomaly and the monthly temperature trend of Iran to the end of 21st century, data from the CMIP6 model set under two SSP2.4-5 scenarios (Consistent with the RCP4.5 scenario of the CMIP5 modes) and SSP5.8-5 (Consistent with RCP8.5 scenario of the CMIP5 modes) was used for the period (2020-2100) with a horizontal resolution of 100 km. The Delta change factor (DCF) method was used to correct the bias of the data and to test the trend analysis in the long-term data series of the Man-Kendall nonparametric test (MK). Sen’s Slope Estimator nonparametric method was also used to estimate the actual slope of the trend in the time series. The minimum monthly temperature in Iran was investigated based on observational data with 5.64 degrees Celsius in January and the maximum temperature of 29.21 degrees Celsius in July. The same is true for future data; the minimum monthly temperature of Iran during the projected future (2020-2100) under the scenario of SSP245 is 7.14 degrees Celsius and under the scenario of SSP585 is 33.8. The maximum temperature, like the observational period in the future projected period in July, for SSP2.4-5 and SSP5.8-5 scenarios, 31.38 and 32.76 degrees Celsius was calculated, respectively. The average temperature anomaly, according to the SSP2.4-5 scenario, is more than 2 degrees Celsius in 9 months of the year, and less than 2 degrees Celsius in January, November and December, which are considered the coldest months of the year. Investigating the temperature trends for over 80 years, it is found that the overall trend of increase in the amount of the increase in intensity in the scenario of SSP5.8-5 under the 0.1 level in all months is significant. The maximum trend intensity was calculated with a Z score of 10.60 in September and the minimum trend intensity was calculated as 2.77 in January. The average temperature trend based on the non-parametric Man-Kendall (M-K) test in Iran is increasing in all months in both of the studied scenarios. This value is statistically significant at the alpha level of 0.1. The trend slope was also measured using the nonparametric Sen’s Slope Estimator (SSE); Under the SSP2.4-5 scenario, the average annual Celsius will be 0.02 year-1 degrees Celsius, and according to the SSP5.8-5 scenario, the average -0.05 year-1 degrees Celsius will increase. Locally, the maximum monthly temperature variability was observed in the mountainous areas of the Zagros and Alborz highlands, respectively. In other words, the highest monthly temperature change rate was observed in the cold period of the year in the mountainous regions. One of the reasons for this high variability can be due to the existence of different weather conditions in the cold season of the year to Iran.}, keywords = {CMIP6 Models,SSP Scenarios,DCF,Temperature trend,Iran}, title_fa = {پیش‌نگری چشم‌انداز بلندمدت دمای آینده ایران مبتنی بر برونداد پروژة مقایسة مدل‌های جفت‌شدة فاز ششم (CMIP6)}, abstract_fa = {در این پژوهش برونداد سه مدل از مدل‌های فاز ششمCMIP6  (Coupled Model Intercomparison Project phase 6) برای درستی‌سنجی انتخاب و چشم‌انداز بلندمدت دمای آیندة کشور پیش‌نگری شد. بنابراین از دو دسته داده شامل دمای 43 ایستگاه­ همدید و برونداد سه مدل BCC-CSM2-MR، CAMS-CSM1-0 و MRI-ESM2-0 از مجموعه مدل­های CMIP6 برای دو دوره (2009-۱۹۹۰ و 2100-2020) با تفکیک افقی ۱۰۰ کیلومتر و سنجه­های متداول آماری شامل MAE (Mean Absolute Error)، MBE (Mean Bias Error)،  RMSE(Root Mean Square Error)، t-Jacovids برای اختلاف دمای ایستگاه و مدل­ها استفاده شد. مقایسة سنجه­های آماری محاسبه‌شده نشان‌دهندة عملکرد بهتر مدل MRI-ESM2-0 در بین سه مدل یاد‌شده می‌باشد. بنابراین مدل MRI-ESM2-0 به‌عنوان مدل منتخب جهت پیش‌نگری دمای آتی کشور تحت دو سناریوی SSP2-4.5 و SSP5-8.5 انتخاب شد. برای حذف اریبی مدلMRI-ESM2-0  از روش تغییر عامل دلتا DCF (Delta Change Factor) و برای مطالعة روند و شیب روند از آزمون‌های من-کندال و سنس استفاده شد. به‌طورکلی نتایج بیانگر بی­هنجاری مثبت دما (متوسط سالانة کل کشور برای سناریو SSP2-4.5، 15/2 و SSP5-8.5، 34/3 oC) در ایران در تمام ماه­های سال تا پایان قرن بیست‌ویکم است. شدت بی­هنجاری در ماه‌های گرم سال بیشتر از ماه­های سرد سال است. متوسط روند دما در تمامی ماه­ها و سناریوها افزایشی و این مقدار از نظر آماری در سطح 1/0 معنی­دار است. متوسط شیب روند بین سالانه در سناریوی SSP2-4.5، year-1 02/0 و بر اساس سناریوی SSP5-8.5، year-1 05/0 درجة سلسیوس محاسبه شد. پیش‌نگری دما در چشم‌انداز بلندمدت نشان داد بیشینة بی­هنجاری دمای ایران در مناطق مرتفع و کمینة بی­هنجاری در سواحل شمالی، شمال­شرق و سواحلی جنوبی خواهد بود.}, keywords_fa = {CMIP6 Models,SSP Scenarios,DCF,Temperature trend,Iran}, url = {https://jesphys.ut.ac.ir/article_77988.html}, eprint = {https://jesphys.ut.ac.ir/article_77988_687ae3eca55adc807ae16871e73faf94.pdf} } @article { author = {Moradi, Mohammad}, title = {Evolution of polar stratospheric vortex during major sudden stratospheric warming in 1979-2019}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {603-620}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.305319.1007232}, abstract = {A major sudden stratospheric warmings (SSWs) represent large-scale perturbations of the polar winter stratosphere, which substantively influence the temperature and circulation of the middle atmosphere and contents of atmospheric species. There are two types of sudden stratospheric warmings: minor warmings and major warmings. In a minor (major) warming the temperature gradient reverses over a range of altitude at or below 010hPa and zonal wind at 010hPa weakens but does not change its direction (reverse direction). Moreover, SSWs have been classified into vortex displacement events and vortex splitting events based on the shape and continuity of the polar vortex. When a major sudden stratospheric warmings events occur, the zonal mean temperature at 10hPa around the polar cap for latitudes north of 60°N suddenly rises and increases by the 25K over period of several days and zonal-mean zonal wind reverses at 10hPa and 60oN during winter from November to March. In this paper, we consider just the major sudden stratospheric warming effect with displacement or split of the polar vortex toward mid latitudes in 1979-2019. We have used the daily mean data from the MERRA2 assimilated data and NCEP-NCAR reanalysis data. From the MERRA2 data, zonal mean zonal wind and zonal mean temperature were obtained at 010hPa from 01 January 1979 to 04 June 2020.The temperature is averaged around the polar cap for latitudes north of 60°N and zonal wind is averaged for 60°N. From the NCEP–NCAR data, geopotential height is presented by a horizontal resolution of 2.5° ×2.5° at 10hPa from 1 January 1949 to 31 December 2019. We first examined the time evolution of zonally averaged temperature and zonal wind at 60°N and 010hPa to identify the warmings onset day, zero day and decay day for the trace of SSWs and its relation with displacement or splitting of the polar vortex. Then we determined three periods: before and after the zero day and the time of recovery for warming event. Also we determined the threshold center latitude for investigating the polar vertex in 1949-2019. Finally, we determine the most probable directions of the polar stratospheric vortex displacement or splitting as a result of major SSWs. Investigation of the zonal mean temperature and zonal-mean zonal wind at 10hPa detected 19 and 13 major and minor SSWs events respectively. From the total number of major SSWs (19), 11(58%) were classified as warmings with splitting of the stratospheric vortex and 8(44%) as warmings with displacement of the vortex. The mentioned 8 cases show that the polar vortex is displaced to the south and weakened after shifting and the other 11 cases show that the polar vortex is split into two cells. Of these 11 cases, 8 cases are of the complete splitting type and 3 cases are of the incomplete splitting type. The SSWs events of 11 February 2001 (displacement type), 8 December 1987, 15 December 1998, 15 January 2004 (incomplete split type), 21 February 1989, 26 February 1999 and 24 January 2009 (complete split type) were selected to represent displacement, incomplete split and complete split type, respectively. During vortex displacements the polar vortex is shifted off the pole and during vortex splits the polar vortex is split into two pieces of comparable size.}, keywords = {Major sudden stratospheric warming,Polar stratospheric vortex,Displacement,Complete split type,Incomplete split type}, title_fa = {ارتباط گرمایش ناگهانی پوشن‌سپهر نوع اصلی با تغییرات تاوه قطبی در دوره آماری 2019-1979}, abstract_fa = {گرمایش ناگهانی پوشن‌سپهر نوع اصلی زمانی رخ می‌دهد، که دمای مناطق نزدیک قطب به‌طور ناگهانی در مدت چند روز، بیش از بیست‌وپنج کلوین افزایش یابد و بادهای غربی پوشن‌سپهر قطبی به شرقی تغییر کند. در این پژوهش، با استفاده از داده‌های بازتحلیلی MERR2، نوزده گرمایش ناگهانی پوشن‌سپهر در طول دورة آماری 2019-1979 آشکار و ارتباط آنها با تاوه قطبی بررسی شد. برای تعیین جابه‌جایی و تقسیم هستة تاوه، ابتدا روز تولد، روز صفر، روز مرگ و مدار آستانه تعریف شد و سپس، دوره‌های قبل و بعد از تغییر و دوره بازسازی در نظر گرفته شد و با به‌کارگیری داده‌های روزانه ارتفاع ژئوپتانسیلی تراز ده هکتوپاسکال در این دوره‌ها، جابه‌جایی و نحوة تقسیم تاوه بررسی شد. بررسی‌ها، نشان داد که، در 42 درصد، هسته تاوه قطبی به‌سوی جنوب جابه‌جا شده است و مرکز هسته پس از جابه‌جایی تضعیف شده است. در 58 درصد، هسته تاوه به دو سلول تبدیل شده است. از این مقدار 8/15 درصد از نوع تقسیم ناقص است، که در آن هسته ثانوی کمتر از دو پربند بسته با فاصله100 ژئوپتانسیل‌متر دارد و از طریق ناوه ارتفاع به هسته اولیه وابسته است. 2/42 درصد نیز از نوع تقسیم کامل است، که از این مقدار، در 8/15 درصد هسته ثانوی از هسته مادر به‌طور کامل جدا شده است و در 4/26 درصد با وجودی‌که هسته ثانوی به‌طور کامل شکل گرفته است و بیش از دو پربند بسته با فاصله 100 واحدی دارند، ولی این هسته از طریق ناوه ارتفاع به هسته مادر وابسته است.}, keywords_fa = {Major sudden stratospheric warming,Polar stratospheric vortex,Displacement,Complete split type,Incomplete split type}, url = {https://jesphys.ut.ac.ir/article_78294.html}, eprint = {https://jesphys.ut.ac.ir/article_78294_a3a2df16c1e87b1899a1508647ca5f42.pdf} } @article { author = {Khodadi, Mohammad Mehdi and Azadi, Majid and Moradi, Mohammad and Ranjbar Saadat Abadi, Abbas}, title = {Effect of Quasi-Biennial Oscillation (QBO) on the Rossby wave breaking over Europe and West Asia: wave activity aspects}, journal = {Journal of the Earth and Space Physics}, volume = {46}, number = {3}, pages = {621-642}, year = {2020}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2020.308378.1007239}, abstract = {In the present study, using the ERA-INTERIM reanalysis data for daily mean of geopotential height, temperature, horizontal wind speed and relative vorticity at 300, 200, 150, 100 and 50 hPa levels, the wave activity and wave activity flux for cyclonic and anticyclonic Rossby wave breaking events that occurred during the easterly and westerly phase of QBO, over Europe for the winter time 1979-2018, were calculated and analyzed. Results showed that during wave breaking events at latitudes around 20-50N are affected by QBO with easterly and westerly phases. As such, the wave breaking events over the Atlantics (east of the Meditranian and west of Asia) during QBOe are weaker (stronger) compared to those during QBOw. The amplitude of the troughs is larger (smaller) during QBOe compared to QBOw and mridional wave activity flux associated with the wave breaking events during the QBOe is smaller (larger) compared to QBOw. While the wave breaking events over the west of the Meditraniean (0-30 N), affected from the tropical jet stream associated with QBO, is different for anticyclonic and cyclonic wave breakings and is described briefly in the following. During the anticyclonic wave breaking events in QBOe, the subtropical jet is shifted over north east of Africa and north of the Arabian Peninsuls and a jet stream is formed at mid latitudes over the south east of Europe. While, in QBOw the subtropical jet stream is intensified over northwest of Africa and is merged with the mid latitude jet stream over southeast of Europe (White et al., 2015). Therefore, in the QBOw, over the Meditranean and west of Europe, the slope of the trough is increased and penetrates to lower altitudes. Consequently, the equatorward wave activity flux caused by anticyclonic wave breaking is increased and the anticyclonic wave breaking is stronger during QBOw compared to QBOe. During the anticyclonic wave breaking events in QBOe, the thermal wind balance is valid near the tropical jet stream associated with QBO over the west of the Indian Ocean and south east of Africa, as secondary circulation is formed that causes the intensification of the subtropical jet stream over north of the Arabian Peninsula and Iran, downstream of the trough. Along with the intensification of the tropical jet stream associated with QBOe over the Atlantics, the subtropical jet stream is shifted to higher latitudes and is intensified. Unlike the trough the altitude of the ridge over the east of the Atlantics is decreased and the zonal wind speed upstream of the trough over the north west of Europe and east of the Atlantics is increased. The Equtorward wave activity flux during the anticyclonic wave breaking events in QBOe is weakened. During the anticyclonic wave beaking events in QBOw, the equatorward shift of the mid latitude jet stream and its merge with the subtropical jet stream downstream of the trough is accompanied with the intensification of the trough over north west of Africa and east of the Mediterranean. Intensification of the jet stream associated with QBOw over the Atalantics causes the subtropical to be shifted equator ward and thus the subtropical jet stream over the east of the Atlantics and north of Africa is intensified and is tilted in the direction NW-SE. During QBOw, along with the penetration of the trough to lower altitudes over Europe, the ridge over the north east of the Atlantics and north of Europe is intensified. Intensification of troughs and ridges causes the intensification of upstream meridional flow and thus the equator ward of wave activity flux associated with anticyclonic wave breakings is increased.  During the cyclonic wave breaking events in QBOe, the subtropical jet is shifted over north east of Africa and north of the Arabian Peninsula and a jet stream is formed at mid latitudes over the Europe in the upstream of the trough. While, in QBOw the midlatitude jet stream is shifted equatorward and is merged with the subtrupical jet stream over northwest of Africa. Therefore, in the QBOe, the slope of the trough is increased and penetrates to lower altitudes, over the Meditranean and East of Europe. Consequently, the poleward wave activity flux caused by the cyclonic wave breaking is increased and the cyclonic wave breaking is stronger during QBOe compared to QBOw. During the cyclonic Wave beaking events in QBOe, intensification of the tropical jet stream associated with QBOe over the Atalantics and south of Africa causes the subtropical jet to be shifted poleward and thus the subtropical jet stream over the west of the Mediterranean and southwest of Europe is intensified.}, keywords = {Anticyclonic Wave Break,Cyclonic Wave Break,Wave Activity Flux,Quasi-Biennial Oscillation,polar vortex}, title_fa = {اثر نوسان شبه‌دوسالانه بر شکست امواج راسبی روی اروپا و ‌غرب آسیا از دیدگاه فعالیت موج}, abstract_fa = {دراین مطالعه با استفاده از میانگین روزانه داده­های بازتحلیلERA-Interim  برای ارتفاع ژئوپتانسیلی، دما، تاوایی نسبی و سرعت باد در ترازهای 300، 200، 150، 100 و50 هکتوپاسکال، کمیت­های فعالیت موج و شارفعالیت موج در شکست‌های واچرخندی و چرخندی امواج درفازهای شرقی وغربی نوسان شبه‌دوسالانه QBO (Quasi Biennial Oscillation) در زمستان دوره 2018-1979محاسبه و بررسی شده­اند. نتایج نشان داد که در شکست واچرخندی و فاز غربی QBO، تقویت جت­حاره غربی وابسته به QBO روی اقیانوس اطلس، موجب جابه‌جایی استواسوی جت­ جنب‌حاره به عرض‌های پایین­تر می­شود. بدین‌ترتیب جت جنب­حاره درپایین­دست ناوه (شمال­شرقی-جنوب­غربی) روی شمال­غرب آفریقا با جت عرض­میانی ترکیب می­شود و ناوه در عرض­پایین­تری روی غرب دریای مدیترانه تقویت و شیب محورشمال­شرقی-­جنوب­غربی آن نسبت به فاز شرقی بیشتر می­شود. درنتیجه شار استواسوی فعالیت موج ناشی از شکست واچرخندی ناوه، در فاز غربی قوی­تر از فاز شرقی QBO است. در شکست چرخندی امواج روی اروپا جت­­حاره شرقی وابسته به QBO، روی جنوب اقیانوس اطلس تا جنوب­آفریقا تقویت می­شود. در شکست چرخندی امواج و فاز شرقی QBO، ناوه روی شرق دریای مدیترانه در عرض‌های بالاتری تقویت و شیب محور شمال­غربی-جنوب­شرقی ناوه نسبت به فاز غربی بیشتر می­شود. بدین‌ترتیب شار قطب­سوی فعالیت موج ناشی از شکست چرخندی نسبت به فاز غربی بیشتر است. درنتیجه علاوه براینکه تعداد شکست­ امواج روی اروپا درفازشرقی تقریباً نصف تعداد آن در فازغربی QBO است، شکست­ واچرخندی (چرخندی) امواج روی اروپا در فازشرقی QBO، ضعیف­تر (قوی­تر) از فازغربی QBO است.}, keywords_fa = {Anticyclonic Wave Break,Cyclonic Wave Break,Wave Activity Flux,Quasi-Biennial Oscillation,polar vortex}, url = {https://jesphys.ut.ac.ir/article_78382.html}, eprint = {https://jesphys.ut.ac.ir/article_78382_c28b850996e4004a0ecc82e4614b4f7c.pdf} }