پيش‌بيني بارش پاييزه و زمستانه نيمه غربي ايران، با استفاده از SST مديترانه در فصول تابستان و پاييز

Forecast of Autumn and Winter Precipitation of West Iran by Use from Summer and Autumn Mediterranean Sea Surface Temperature

كشور ما به دليل واقع شدن در همسايگي منابع رطوبتي فراوان درياي مديترانه در غرب، خليج‌فارس و درياي عمان در جنوب، درياي خزر در شمال، درياي سياه و اقيانوس هند تاثيرپذيري نسبتاً زيادي از SST مناطق رطوبتي ياد شده دارد. لذا بررسي و مطالعه اين تاثيرها بر مقدار بارش‌هاي كشور، نقش اساسي در شناخت نوسان‌هاي بارش و پيش‌بيني مقادير بارش آن دارد. از آنجا كه خشكسالي و سيل خسارات زيادي به جوامع و بخش‌هاي مختلف اقتصادي در ايران وارد مي‌كند، لذا پيش‌بيني بارش داراي نقش اساسي در مديريت بهينه منابع آب و خاك، و نيز جايگزيني مديريت ريسك به جاي مديريت بحران و توسعه پايدار كشور است. در اين پژوهش ميزان تاثير فصلي دماي سطح آب درياي مديترانه (Mediterranean SST) بر بارش‌هاي فصلي نيمه غربي ايران بررسي شده است. ابتدا دوره‌هاي گرم و سرد و پايه (شرايط معمولي دماي سطح آب مديترانه) تعريف شد و سپس ميانه آماري بارش در هر دوره با عناوين به ترتيب Rw، Rc، Rb محاسبه گرديد و از مقادير نسبت‌هاي Rb/Rw، Rb/Rc، Rc/Rw و Rw/Rc به‌منظور ارزيابي ميزان تاثير اين شرايط بر بارش استفاده شد. نتايج نشان داد زماني كه در فصل پاييز MedSST سردتر از معمول باشد، بارش زمستانه منطقه مورد مطالعه افزايش مي‌يابد ولي دماي گرم‌تر از معمول آن در فصل تابستان باعث افزايش بارش پاييزه مي‌شود. همچنين بين نوسانات MedSST در فصل پاييز و بارش زمستانه ايستگاه‌هاي مورد مطالعه، همبستگي معني‌دار منفي وجود دارد، ولي بين نوسانات MedSST در فصل تابستان و بارش پاييزه ايستگاه‌‌هاي مورد مطالعه همبستگي معني‌دار مشاهده نشد؛ اما تمايل نسبتاً مشخصي بين افزايش بارش پاييزه با دماي گرم مديترانه ملاحظه مي‌شود.

Introduction Our country because of locating in neighborhood great watery sources of Mediterranean sea in west, Persian gulf and Oman sea in south, Caspian sea in north, Black sea and Indian ocean has been effected from sea surface temperature of these watery surfaces mostly. Therefore studying these effects on amount of country precipitation plays the main role in understanding of oscillations of precipitation and forecast of amount of precipitation in our country. In the recent years relation among agents of climate in ocean, atmosphere and land has been noticed by meteorologists and climatologist. Results of researches have indicated that changes temperature in surfaces of water can effect on changes of precipitation in the land confidently. Anomalies of sea surface temperature effect not only on seaside but also on far regions from sea. Mediterranean Sea is in limitation of geography 32 to 46 degrees latitude of north and 3 degrees altitude of west to 35 degrees altitude of east. This sea expands about 2.5 million km2. Changes of climate in this watery great surface can effect on west climate of Iran confidently. West winds make three troughs on U.S., East Asia and Mediterranean Sea in winter. This trough (Trough of Mediterranean Sea( is replaced on limitation of Mediterranean Sea that permit entering West wind and its system to limitation of west of Iran. Therefore in this research precipitation of autumn and winter seasons of west Iran has been forecasted by using summer and autumn Mediterranean Sea surface temperature. Drought and flood enter most costs for economic different parts For this purpose forecast of precipitation has main role in management of water sources and soil, replacement of management of risk to replace management of crisis and stable development in the country. In this research, precipitation of autumn and winter seasons in western parts of Iran has been forecast by using summer and autumn Mediterranean Sea surface temperature. Materials and Methods In this research two series of data have been used; first: seasonal data of Mediterranean Sea surface temperature in statistic period (1970-2005(, and secondly seasonal data of precipitation of west Iran in statistic period (1970-2005). For this purpose the periods such as warm, cold, base ones were determined for dates of MEDSST (Mediterranean Sea Surface Temperature) in statistics period of 1970 – 2005 for each season. Then statistical Medians of precipitation in every season and every period were determined so as (Rw, RC and Rb.( Theses Medians in every season and every period are compared together to clear amount of influence of theses condition. Also the authors have used correlation method between MedSST data in summer and autumn seasons and precipitation data in autumn and winter season by using Minitab software. From Regression method used for estimation of statistic trend of confident correlation. Results and Discussion Results indicated that when MEDSST in summer season is warmer than normal, autumn precipitation of West region of Iran is increased but when MEDSST of colder than normal in autumn season is caused increase of precipitation in the winter season. There is negative and confident correlation between MEDSST anomalies in autumn season and precipitation anomalies of West of Iran in winter season and there is not confident correlation between summer MEDSST anomalies and autumn precipitation in west region but intention of certain fairly is between increase of autumn precipitation the west region of Iran and warmer than normal MedSST of summer season. Climatic Oscillations have main effect on soil, cover of vegetation, watery sources and land use. Conclusion Climate and its factors certainly precipitation and its problematic changes play important role in environment of human life in lengths of time. Climatic Oscillations have the main effect on soil, cover of vegetation, watery sources and land use. Knowledge of this changes can provides correct usage of nature and management of watery and soil sources that cause planning better consequently.