تاثير نوسانات ماهانه دماي آب درياي مديترانه بر نوسان ماهانه بارش هاي شمال غرب ايران

the impact of monthly fluctuations Mediterranean sea surface temperature in the fluctuations of monthly precipitation northwest Iran

تاثير دماي سطح آب دريا (SST) بر مقدار بارش محدود به ساحل نبوده و نواحي دور از دريا را نيز تحت تاثير قرار مي دهد. تشخيص همبستگي بين SST و بارش نقش موثري در پيش بيني خشكسالي و ترسالي مناطقي كه تحت تاثير نوسانات دماي آب قرار مي گيرند خواهد داشت. در پژوهش حاضر به منظور شناخت بهتر از شرايط بارشي، ارتباط نوسان ماهانه SST مديترانه با بارش شمال غرب ايران بررسي مي گردد. پس از مشخص كردن دوره هاي سرد و گرم دماي ماهانه سطح آب درياي مديترانه نسبت به دماي ميانگين آن در دوره آماري (2014-1982) ، ميزان همبستگي بين SST و بارش در سطح منطقه محاسبه گرديد. نتايج نشان داد تاثير SST بر نوسان بارش منطقه از نظر زماني و مكاني متفاوت است و بارش ماه هاي مارس، اوريل و مي بيشترين همبستگي (در سطح اطمينان 95 و 99 درصد) را با دماي آب دارد. گرم بودن SST در تمام سطح درياي مديترانه در ماه سپتامبر با كاهش بارش در ماه نوامبر و سرد بودن SST غرب دريا در ماه نوامبر و دسامبر با كاهش بارش اين دو ماه همبستگي نشان داد. بين سرد بودن SST غرب دريا در فوريه و كاهش بارش ماه آوريل، هم چنين سرد بودن SST شرق دريا در ماه مارس و كاهش بارش ماه مارس و ماه مي ارتباط معني داري وجود دارد. هم چنين ارتباط معني داري (در سطح اطمينان 95 تا 99 درصد) بين گرم بودن SST تمام دريا و افزايش بارش ماه آوريل در منطقه شمال غرب مشاهده شد. بطور كلي نتايج اين تحقيق نشان داد هرچند براساس رابطه همبستگي بين SST و بارش، شناخت كلي از شرايط بارش امكان پذير مي باشد، معذالك بررسي شرايط سينوپتيك-ترموديناميكي جو چگونگي اين ارتباط را توجيه خواهد كرد.

Due to the high heat capacity of the seas، there is a significant effect on land areas climate fluctuations. The impact of sea surface temperature (SST) on the amount of rainfall was not limited to the coasts and also affect regions far from the sea. So recognize the correlation between SST and precipitation will have a significant role in predicting drought and wet areas that are affected by fluctuations in SST. In this study، Relationship monthly fluctuations Mediterranean sea surface temperature With fluctuations monthly precipitation northwest Iran(Includes six provinces، West Azerbaijan، East Azerbaijan، Kurdistan، Zanjan، Kermanshah، Hamedan) were studied. For this purpose، after determine the Colder and warmer periods Monthly temperature of the water level of the Mediterranean Compared to normal temperature، during the 33-year-old(1982-2014)، The correlation coefficient between Monthly temperature water level and monthly precipitation was obtained in each province. In periods when there was a significant relationship between water temperature and precipitation، The rate of increase / decrease in precipitation under the influence of temperature fluctuations were studied. The results showed the effect of water temperature on regional precipitation variation، Is different in time and location and the precipitation spring show the highest correlation with water temperature. In the months of autumn، the sea water temperature was colder than usual and precipitation and water temperature has a significant relationship، precipitation is reduced. But was not observed Significant relationship between warmer than usual water temperatures and fluctuating precipitation. in winter In most cases، the water temperature was colder than usual and Have a high correlation with precipitation، Increased rainfall has caused and In no previous period there was no Significant relationship between the warmer than normal water temperatures and Fluctuation of precipitation this season. Also there is a significant Relationship between cooler than normal water temperatures in the winter months and Reducing precipitation in the spring. In the spring only in april warmer than usual water temperatures On the whole the sea with a significant level of more than 96%، increased precipitation caused In the entire study area and in other cases، warmer than usual water temperatures with decreasing precipitation and it is colder than usual Has been associated with increased precipitation. it should be noted results of this study show a causal relationship and To justify this relationship need to examine atmosphere is dynamic and synoptic.