@article { author = {Shabanian, Amir and Nasr-Esfahany, MohammadAli and Arkian, Frozan}, title = {Factors Affecting the summer rainfall in a region with complex topography (Case Study: Golestan Province)}, journal = {Journal of the Earth and Space Physics}, volume = {41}, number = {3}, pages = {565-577}, year = {2015}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2015.53694}, abstract = {Iran is a vast land of geographically specific features and the climate is quite different. Each year a number of times, short intense rains caused flooding in various parts of the southern coast of the Caspian Sea and river flood malicious conduct is falling. The rainfall intensity is greater and more destructive floods caused heavy damage. Severe flooding during the brutal summer precipitation in the region, notably Iran, which sometimes lead to large losses of life and property. Having the proper depth of the Caspian Sea and the north-south strain and temperature is relatively constant during the period of two to three days, thus having the potential to heat and high humidity, high impact weather system is feeding. Another factor influencing the occurrence of floods in Golestan province Alborz mountain range and its effect on the flow of the atmosphere and therefore the issue is complex. Factors such as height and width roughness, and the interaction of the Alborz mountains to heavy rainfall in the region and how the agent is effective. Here a summer torrential rainfall in Golestan province is simulated using the WRF model toinvestigate the effective factors. 30 vertical sigma levels are used in the network. To run the model horizontal resolution of 3 nesting range of 90, 30 and 10 km in length and latitude is used. During geographically considered the center latitude 54,15 and 35,51 respectively. Model of internal networks and the highest point is 27 × 27, 31 × 43 and 34 × 45 grid points are. Depending on the selected physical model microphysics scheme WSM5, longwave radiation scheme RRTM, shortwave radiation scheme Dudhia, cumulus parameterization scheme and Kian-Fritsch are YUS boundary layer.To investigate the role of vertical surface fluxes and effects of the Alborz mountains on rainfall intensity in the selected system, four experiments were conducted to test the model simulation with control (CTL), the physical model was used. In a second experiment was to delete the Elburz Mountains (NTO), in the third experiment, the vertical flux of moisture and temperature of the Caspian Sea has been removed (NFL) and the fourth test of the Elburz Mountains and vertical flux of moisture and temperature simultaneously removed the Caspian Sea (BOT) and the results of the first experiment (control) were compared. Using the output of the model, some parameters such as the effective rainfall floods the advection of temperature, convective available potential energy, vorticity advection in the simulations were calculated and analyzed. The results show that the mechanisms of rainfall in the Golestan province depend to position of phenomena. So that the horizontal convergence of heat and humidity fluxes are the main causes of rainfall along the coastline of the Caspian Seawhile the rainfall over Northern part of Alborz mountains range is caused by the forcing ascent over the mountain. The heavy rains in the South East of the Caspian Sea occurred due to the horizontal convergence of heat flux, intense upward vertical flux and significant amount of CAPE.Convective instability in this area is due to the warm advection in surface and cold advection in middle troposphere. Upward motion and precipitation start with positive vorticity advection in 500-hPa level which is affected by Alborz Mountain strongly.}, keywords = {Torrential rain,golestan,Caspian Sea,simulation,topography,heat and moisture fluxes}, title_fa = {بررسی عوامل مؤثر بر بارش‌های تابستانی در یک ناحیه با توپوگرافی پیچیده (مطالعة موردی: سیل استان گلستان 8 تیر 1391)}, abstract_fa = {در این مطالعه عوامل مؤثر بر بارش‌های شدید و سیل‌آسا در استان گلستان با استفاده از مدل WRF بررسی شده است. برای شناسایی نقش عوامل طبیعی در رخداد این بارش‌ها، سه آزمایش مختلف طراحی شد. این آزمایش‌ها شامل حذف اثر توپوگرافی رشته‌کوه البرز، شارهای گرمایی و رطوبتی دریای خزر و حذف همزمان این دو برای سامانة منتخب بوده است. سپس برخی کمیت‌های هواشناختی مهم و مؤثر بر بارش از قبیل فرارفت دما و تاوایی، شار قائم و افقی گرمایی و رطوبتی و انرژی پتانسیل در دسترس همرفتی (CAPE) محاسبه و تحلیل شدند. نتایج نشان داد که بارش‌ها در مناطق مختلف استان گلستان ساز و کار متفاوتی دارند. به این صورت که بارش‌ها در دامنه‌های شمالی البرز در اثر صعود واداشتی هوا بر دامنه‌های رشته‌کوه البرز رخ داده است. بارش‌های شدید در جنوب شرق دریای خزر که منشأ سیل بوده‌، به سبب همگرایی شار گرمایی افقی، شار قائم فراسو و ناپایداری همرفتی در منتهاالیه جنوب شرقی دریای خزر بوده است. ناپایداری همرفتی ناشی از فرارفت هوای گرم در ترازهای پایین جو و فرارفت هوای سرد در میانة وردسپهر است. شروع حرکت‌های فراسو و بارش‌ها به دلیل فرارفت تاوایی مثبت در تراز 500 هکتوپاسکال بوده که به‌شدت متأثر از رشته‌کوه البرز است.}, keywords_fa = {Torrential rain,golestan,Caspian Sea,simulation,topography,heat and moisture fluxes}, url = {https://jesphys.ut.ac.ir/article_53694.html}, eprint = {https://jesphys.ut.ac.ir/article_53694_66b92342819a57c2f80dc9269ef3e444.pdf} }