آشکارسازی و به ‌روز رسانی تغییر اقلیم در ایستگاه‌های کشور (دوره 2017-1958)

این پروژه،تخمین جدیدی ازروندتغییرات اقلیمی درایران می باشد که در آن روند تغییر پذیری عناصر اقلیمی پس از کشف و تعدیل ناهمگنی های غیر اقلیمی بررسی گردیدند.داده ها متغیرهای دما، بارش، رطوبت، تابش، ابرناکی، باد و ساعت آفتابی 27ایستگاه همدیدی کشورمی باشند که دوره2017 1958 میلادی (60 سال) را پوشش می دهند. به دلیل نواقص موجود، متغیر ساعت آفتابی، در دوره 2017-1992 بررسی شد. نتایج نشان دادند که میانگین دمای هوا، میانگین دمای بیشینه و دمای کمینه سالانه کشور در 60 سال اخیر به ترتیب(0.7±) 17.5، (0.8±) 24.9، و (0.8±)10.1 درجه سلسیوس و در 30 سال آخر منتهی به 2017 به ترتیب(0.7±) 17.9، (0.8±)25.2 و (0.7±) 10.6 درجه سلسیوس می باشد. در 60 سال اخیر،کشورایران بادارابودن اقلیم های متفاوت،شاهد روندافزایشی میانگین دما، دمای بیشینه و کمینه سالانه به ترتیب بانرخ های (0.35، 0.19) 0.27، (0.3، 0.08) 0.2 و (0.41، 0.28) 0.34 درجه سلسیوس بر دهه بوده است که این مقادیر در دوره 30 سال آخر به ترتیب(0.63، 0.25) 0.55 ،(0.75، 0.18) 0.57 و(0.6، 0.25)0.53 درجه سلسیوس بر دهه بوده است. علی رغم عدم وجود روند در میانگین بارش،به طورمتوسط بارش ایران دردوره 60 ساله منتهی به سال 2017، حدود (2.2، 11.6) 4.7 و در 30 سال 1988تا 2017 میلادی (4.1، 37.2)20 میلیمتر بر دهه کاهش می یابد که این روند کاهشی (30 ساله) در سطح احتمالاتی 0.05 معنی دار می باشد.میانگین سرعت باد در مقیاس سالانه در بسیاری از نقاط کشور، علاوه بر نوسانات شدید دارای روند افزایشی بوده است که در غرب و شمال کشور این افزایش معنی دار می باشد. تعداد ساعات آفتابی در اغلب نقاط کشور با شیب 4.65 ساعت برسال طی دوره (2017-1992) افزایش یافته است که افزایش در شمال شرق و شمال و مرکز کشور معنی دار می باشد. میانگین رطوبت نسبی و روزهای تمام ابری (به استثناء گرگان) در اکثر مناطق کاهش داشته که بیشترین کاهش روزهای تمام ابری در غرب دریای خزر و نیمه غربی کشور می باشد که با کاهش رطوبت دراین مناطق نیز مطابقت دارد.

Climate change detection update over Iran during 1958-2017

IntroductionThis project is an updated estimate of the climate change trend in Iran. The time series of monthly and annually mean, maximum and minimum temperature (°C), relative humidity (%) at 2 m height, wind speed (m.s) at 10 m height, sun hours (h), precipitation (mm), radiation (Mj.m2day1) and cloudiness data at 27 weather stations over Iran are collected from IRIMO for the period 19582017. Quality control, detection and modification of nonclimate heterogeneity of data was performed. Due to missing data, the Sun hours trend was calculated for the period 19922017. Methodology and dataAmong all stations of Iran, 27 stations have 60yearly data in the period of 19582017. In this research the changes in temperature, precipitation, humidity, radiation, cloudiness and wind during the period of 20171958 (for sunshine the period was 19922017) were investigated. At first, the data were checked for quality controlling. Then their nonclimatic heterogeneities were fixed. The slope of the trend was determined using the least squares method and the slope estimator and their significance was assessed using nonparametric ManKendal test and regression.ResultsTemperature: The results showed that all stations in the country face a significant increase in the annual minimum temperature. The minimum temperature increasing rate per decade calculated to be between 0.2 and 0.4  degree of Celsius in BandarAbbas and Tehran, alternatively. In general, minimum temperatures rise were detected at all stations and in all seasons, especially in autumn and winter. The annual maximum temperature trend is also increasing, but the rate of increase in maximum temperature is less than the minimum temperature. The increasing rate per decade calculated to be between 0.08 and 0.3  degree of Celsius in Zanjan and Ahwaz, alternativelyPrecipitation: The 60, 30, and 10years averaged annual precipitation of Iran calculated to be 230.8, 222.4 and 199.3 mm, respectively. The results showed that during the 60year period, the average rainfall of the Iran decreases, with a rate of 0.43 mm per year (4.3 mm per decade), although the precipitation decline is not significant at 95% level.However, during the last 30 years (20171988), the average precipitation of the country has dropped by 2.2 millimeter per year (22 mm per decade), which is significant in 95% confidence level; meaning that precipitation reduction in the most recent 30 years is about four times higher than that of past 60 years.In Figures 2 and 3, the allcountry time series of rainfall and temperature changes are shown in the 60 and 30yearly basis.The country’s declining precipitation for the most recent 30 years is about four times faster than the decline of most recent 60 years. The rapid decline in country precipitation over the past 30 years, which is significant   in 95% level, is consistent with the intensification of global warming in the most recent 30 years period.Other parameters: The average wind speed in many parts of the country has increasing trend, which is significant in many stations located in the west, center, and northern part of the country. Average relative humidity has decreased in many regions of the country. The most decreasing trend was observed in southwest and west of the country. Of course, in a few cases such as Gorgan and Rasht, there was an increase, which was not statistically significant. Sunny hours trend was calculated in the period of 19921992, and interestingly, seasonal and annual trends at most stations indicate an increase in the number of sunny hours. The total number of days with sky overcast in the west of the Caspian Sea, western part of the country, and stations such as Kerman, Sabzevar and Shahrood has decreased significantly..