بررسی روند و پیش نگری تغییرات فرین های دمایی با استفاده از مدل های cmip6 در شمال غرب ایران

بررسی تغییرات فرین‌های دمایی به دلیل گرمایش جهانی، خشکسالی و رخداد سرما و یخبندان دارای اهمیت زیادی است. لذا در این پژوهش به بررسی روند و پیش‌نگری تغییرات فرین های دمایی در شمال غرب ایران در دوره پایه (2014-1985) و سه دوره آینده نزدیک(2050- 2021)، آینده متوسط(2081 2050) و آینده دور(2100 2081) پرداخته شد. بدین منظور از 2 شاخص‌ حدی دمایی شامل روزهای یخبندان (fd) و روزهای یخی (id) و آزمون روند من کندال (maan kendall) جهت بررسی تغییرات استفاده شد. جهت پیش‌نگری تغییرات در دوره آینده نیز از بهترین مدل پس از ارزیابی 7 مدل‌ گردش عمومی جو (gcms) از سری مدل‌های گزارش ششم (cmip6) تحت سه سناریوی واداشت اجتماعی اقتصادی شامل ssp1 2.6, ssp3 7.0 و ssp5 8.5 بهره گرفته شد. توزیع فضایی روند تغییرات حدی‌های دمایی در دوره پایه نشان داد که با حرکت از شمال به جنوب و از غرب به شرق منطقه روزهای یخبندان افزایش می‌یابد. هسته بیشینه روزهای یخی نیز تقریبا در جنوب منطقه مورد مطالعه قرار گرفته است. ارزیابی مدل‌های مختلف با شاخص‌های خطاسنجی مختلف نشان داد که مدل‌های mri esm2 0 و mpi esm1 2 l بهترین عملکرد را در شبیه سازی فرین های دمایی در منطقه مورد مطالعه دارند. توزیع روند تغییرات در دوره آینده نیز نشان داد که روندها مشابه با دوره پایه است به طوری که روندهای کاهشی در شاخص‌های مورد بررسی به ویژه بر اساس سناریوی ssp5 8.5 در هر دوره تشدید خواهد شد. بدین صورت که روزهای یخبندان و روزهای یخی در انتهای قرن 21 نسبت به دوره پایه به ترتیب 45 و 13 روز، کاهش داشته است که بیشترین کاهش آنها نیز مربوط به ایستگاه‌های سردسیر منطقه است که نشان می‌دهد با افزایش دما، شاخص‌های یخبندان و روزهای یخی کاهش پیدا خواهد کرد.

investigating the trend and predecting changes in temperature extremes using cmip6 models in northwest of iran

investigating of extreme temperature changes due to global warming, drought and the occurrence of cold and frost is very important. therefore, in this research, the trend and projection of changes in temperature extremes in northwest iran in the base period (1985 2014) and three periods of the near future (2021 2050), the medium future (2051 2080) and the far future (2081 2100) was paid. for this purpose, two extreme temperature indices including frost days (fd) and ice days (id) and the maan kendall trend test were used to check the changes. in order to anticipate the changes in the future period, the best model after evaluating 7 general circulation models (gcms) from the coupled model intercomparison project phase 6 (cmip6) under three the shared socioeconomic pathway including ssp1 2.6, ssp3 7.0 and ssp5 8.5 was used. spatial distribution of the trend of changes in extreme temperature in the base period showed that by moving from north to south and from west to east, the ice days increase. the core of the maximum ice days has also been studied almost in the south of the region. according to the results, the average frost days and ice days in the base period are 101 and 19 days per year, respectively, and the maximum and minimum frost days are 146 and 52 days, respectively, for sarab and parsabad stations, and the maximum and minimum frost days are also, with 42.32 and 1.23 days, it is related to zarineh and parsabad stations. also, the trend of changes in frost days and ice days in the base period in most stations is a decrease, which is significant at the 0.05 level. the evaluation of different models with different error measurement indices showed that mri esm2 0 and mpi esm1 2 l models have the best performance in simulating extreme temperature in the study area. the evaluation of the trend of changes in frozen days and ice days using the mann kendall test in the basic period showed that the trend of changes in most stations is significant at the 1% level. the distribution of changes in the future period also showed that the trends are similar to the base period, so that the decreasing trends in the studied indicators will intensify in each period, especially based on the ssp5 8.5 scenario. thus, at the end of the 21st century, frost days and ice days have decreased by 45 and 13 days, respectively, and the largest decrease is related to the cold stations of the region, which shows that with the increase in temperature, the index frosts and icy days will decrease.investigating of extreme temperature changes due to global warming, drought and the occurrence of cold and frost is very important. therefore, in this research, the trend and projection of changes in temperature extremes in northwest iran in the base period (1985 2014) and three periods of the near future (2021 2050), the medium future (2051 2080) and the far future (2081 2100) was paid. for this purpose, two extreme temperature indices including frost days (fd) and ice days (id) and the maan kendall trend test were used to check the changes. in order to anticipate the changes in the future period, the best model after evaluating 7 general circulation models (gcms) from the coupled model intercomparison project phase 6 (cmip6) under three the shared socioeconomic pathway including ssp1 2.6, ssp3 7.0 and ssp5 8.5 was used. spatial distribution of the trend of changes in extreme temperature in the base period showed that by moving from north to south and from west to east, the ice days increase. the core of the maximum ice days has also been studied almost in the south of the region. according to the results, the average frost days and ice days in the base period are 101 and 19 days per year, respectively, and the maximum and minimum frost days are 146 and 52 days, respectively, for sarab and parsabad stations, and the maximum and minimum frost days are also, with 42.32 and 1.23 days, it is related to zarineh and parsabad stations. also, the trend of changes in frost days and ice days in the base period in most stations is a decrease, which is significant at the 0.05 level. the evaluation of different models with different error measurement indices showed that mri esm2 0 and mpi esm1 2 l models have the best performance in simulating extreme temperature in the study area. the evaluation of the trend of changes in frozen days and ice days using the mann kendall test in the basic period showed that the trend of changes in most stations is significant at the 1% level. the distribution of changes in the future period also showed that the trends are similar to the base period, so that the decreasing trends in the studied indicators will intensify in each period, especially based on the ssp5 8.5 scenario. thus, at the end of the 21st century, frost days and ice days have decreased by 45 and 13 days, respectively, and the largest decrease is related to the cold stations of the region, which shows that with the increase in temperature, the index frosts and icy days will decrease.