Analyzing the trend and extent of Sudan low pressure and its impact on precipitation in western and southwestern Iran

Abstract

The goal of the study is to analyze the trend and extent of Sudan low pressure with respect to climate change and its relation to the upper atmosphere levels and the influences of the variation on precipitation in October, November, December, January, February, and March during the period from 1951 to 2018. This period was divided into seven 10-year periods for a deeper analysis. It was found that the average geopotential height (hgt) in the two studied levels (1000 and 500 hPa) and all the periods, except for the first (1951 to 1960), had an increasing rate, which points to the weakening of the Sudan low pressure. The mean hgt at 1000 hPa increased with a slope of 0.9, 2.64, and 3.2 hgt for October, November, and December, and 3.6, 1.8, and 1.3 hgt for January, February, and March, respectively. The results showed that December and January had the highest rate of increase in pressure at 1000 hPa. The coefficients of variation (CV) had a significant trend of − 1.4, − 1.4, 0.08, − 0.19, − 0.36, and − 1.8% per decade for October, November, December, January, February, and March, respectively. The minimum and maximum hgt showed a noticeable increasing trend in the levels. The low-pressure extend showed a significant decreasing trend of 62,8347.3 and 62,440.8 km2 in December and January, respectively, which was significant at 0.01. There was a negative and significant correlation between hgt at 1000 hPa and precipitation of western and southwestern Iran in winter regardless of periods, whereas there was a significant negative correlation in Ahvaz taking the periods into account.