@article { author = {Pegahfar, Nafiseh}, title = {Verification of potential intensity relations for the northwest Indian Ocean tropical cyclones during 1990-2019}, journal = {Journal of the Earth and Space Physics}, volume = {47}, number = {2}, pages = {371-386}, year = {2021}, publisher = {Institute of Geophysics, University of Tehran}, issn = {2538-371X}, eissn = {2538-3906}, doi = {10.22059/jesphys.2021.316954.1007279}, abstract = {Prediction of tropical cyclone (TC) intensity has been considered in numerous research studies, due to TC destructive effects. Hence, various parameters were combined in potential intensity relations to show the maximum probable intensity that a TC can achieve. The relations of potential intensity are different, since each relation has been suggested based on various factors affecting TC intensity. In this research, the validity of five potential intensity relations, defined by other researchers for the other basins, was verified for all TCs formed over the northwest of the Indian Ocean from 1990 to 2019. In this duration, sixteen cyclonic storms, nine sever cyclonic storms, ten very sever cyclonic storms and ten extremely severe cyclonic storms occurred. In this research, two sets of data reported by India Meteorological Department (IMD) and reanalysis data from the fifth generation of the European Center for Medium Range Weather Forecast (ECMWF, ERA5) with the horizontal resolution of 0.25 degrees were used. The IMD data included position (latitude/longitude) of the TC’s eye and maximum wind speed. The reanalysis data consisted of meteorological parameters from sea level to the tropopause level, including relative and specific humidity, temperature, pressure, dew point temperature and horizontal wind vector. The first relation for the potential intensity is based on the difference between convective available potential energy values at the radius of maximum wind using saturated and unsaturated air mass. The second one considers the difference between saturated entropy at sea level and environmental value of entropy. The third relation consists of the ratio of difference between upper-level and lower-level temperature to the outflow temperature and also the discrepancy between saturated and unsaturated enthalpy. The fourth relation includs difference of saturated and unsaturated values of equivalent potential temperature at the radius of maximum wind. The last relation not only uses the ratio of temperature of inflow and outflow and discrepancy between surface and boundary layer entropy, but also emphasizs on surface temperature. The ratio of the enthalpy and drag coefficients is used in the all relations, while thermodynamic efficiency is included in some recent relations. The potential intensity values achieved using the empirical relations, were evaluated using the maximum wind speed reported by IMD. The comparison was done based on some statistical indexes and the Taylor diagrams. The statistical indices include (I) index of agreement (IOA), (II) standard deviation, (III) root mean square deviation and (IV) correlation coefficient. For the intensity of depression and deep depression states, the minimum value of IOA was achieved using the first relation, while the other relations produced the close values of around 0.7. For the CS-Category intensity, the first two relations produced the lowest IOA values. For the SCS- Category the last two relations did the best performance, while for VSCS- and ESCS-Categories, the second relation produced the most consistent results. The results from IOA showed that the fifth relation produced the highest agreement with the IMD data. This showed that the discrepancy between sea surface temperature and tropopause temperature and the difference between environmental entropy and inner-core entropy played the most important role in intensification for the first four categories of intensity. However, for the last two categories of intensity the discrepancy between the saturated entropy at surface and entropy of boundary layer produced IOA of 0.73 and 0.75, respectively. It is notable that the difference between saturated equivalent potential temperature and potential temperature of boundary layer, and also difference between temperature of inflow and outflow produced the same results for the beginning state. The other statistical indices were analyzed based on the Taylor diagram focusing on all considered tropical cyclones that were intensified to the various intensities. Conclusions demonstrated that the last and the second potential intensity relations produced the best performance in the all categories for the TCs formed over the northwest of the Indian Ocean during 2019-1990. }, keywords = {Potential Intensity,Entropy,Enthalpy,empirical relations,Tropical cyclone,Northwest of the Indian Ocean}, title_fa = {اعتبارسنجی روابط پارامتری محاسبه شدت پتانسیلی برای چرخندهای حاره‌ای شمال‌غرب اقیانوس هند در بازه اقلیمی 2019-1990}, abstract_fa = {شاخص تجربی شدت پتانسیلی، نشان‌دهنده بیشینه شدت محتمل یک چرخند حاره­ای است. در این پژوهش اعتبار 5 رابطه شدت پتانسیلی پیشنهاد شده توسط سایر محققین برای سایر حوزه­ها، برای تمام چرخندهای حاره­ای شکل گرفته (45 مورد) در شمال­غرب اقیانوس هند در بازه زمانی 1991-2019 ارزیابی می­شود. این روابط با ترکیب پارامترهایی از قبیل انرژی پتانسیل همرفتی دسترس‌پذیر، آنتروپی، آنتالپی، دمای پتانسیلی، دما در سطح دریا و وردایست و برخی ثابت­ها به‌دست آمده‌اند. بدین منظور از داده‌های مرجع اداره هواشناسی هند و داده­های بازتحلیل نسل پنجم از مرکز اروپایی پیش­بینی میان­مدت جو استفاده شد. پارامترهای مورد نیاز در منطقه هسته درونی چرخند و محیط اطراف آن محاسبه شدند. شاخص‌های آماری اعم از سازگاری، انحراف معیار، ضریب همبستگی و خطای جذر میانگین مربعات برای تمام چرخندهای حاره­ای با ­شدت­های متفاوت محاسبه شدند. نتایج نشان داد که در منطقه موردمطالعه رابطه پنجم که شامل اختلاف دما بین سطح دریا و وردایست و اختلاف آنتروپی بین محیط و هسته درونی چرخند بود، در 4 دسته شدت اولیه به‌ترتیب با شاخص­های سازگاری 74/0، 74/0، 73/0، 70/0 بالاترین کارایی را برای پیش­بینی شدت داشته است. برای شدت‌های قوی‌تر، رابطه دوم که حاوی اختلاف آنتروپی اشباع در سطح و آنتروپی لایه مرزی بود، به‌ترتیب شاخص‌های سازگاری 73/0 و 75/0 را تولید کرد. رابطه مبتنی بر اختلاف دمای پتانسیلی هم­ارز اشباع با دمای پتانیسیل لایه مرزی و اختلاف دمای برون­شارش با دمای درون­شارش نیز برای دو دسته شدت ابتدایی و میانی، نتیجه­ای مشابه تولید کرد. نهایتاً روابط پنجم و دوم دقیق­ترین نتایج را تولید کردند. }, keywords_fa = {Potential Intensity,Entropy,Enthalpy,empirical relations,Tropical cyclone,Northwest of the Indian Ocean}, url = {https://jesphys.ut.ac.ir/article_81521.html}, eprint = {https://jesphys.ut.ac.ir/article_81521_78ba813b9fb41cc036e5a010d207187b.pdf} }