Climatology
Mohammad Reza Azizzadeyya Varzegan; khadijeh javan
Volume 23, Issue 70 , March 2020, , Pages 227-246
Abstract
One of the most important effects of climate change is increasing in extreme climate events. Change in the frequency or intensity of extreme events can have significant impacts on natural environments and human societies so their analysis is very important. The aim of this study is to identify the trend ...
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One of the most important effects of climate change is increasing in extreme climate events. Change in the frequency or intensity of extreme events can have significant impacts on natural environments and human societies so their analysis is very important. The aim of this study is to identify the trend of precipitation extremes in Lake Urmia basin and to investigate their relation with Teleconnection patterns. For this purpose, daily precipitation data of 7 synoptic stations in the basin during 1987-2014 was used. 11 extreme precipitation indices were extracted using the RClimDex and their trends were calculated by non-parametric Mann-Kendall test. Then the relationship between these indices with Teleconnection patterns was determined by the Pearson correlation coefficient. The results of time series analysis showed that all extreme precipitation indices in Lake Urmia basin have decreasing trend exept consecutive dry days (CDD). The spatial distribution of trend in extreme indices showed almost all indices have a significant trend at the 5% significance level in basin. There is no significant trend in consecutive dry days (CDD). The changes in extreme precipitation could be affected by the El Niño-Southern Oscillation (ENSO), Southern Oscillation Index (SOI), East Pacific-North Pacific (EP-NP), Madden and Julian Oscillation (MJO) and Pacific Decadal Oscillation (PDO).
Majid Rezayee Banafshe; Fatemeh Sarafroozeh; Tahereh Jalali
Volume 16, Issue 38 , February 2012, , Pages 43-74
Abstract
For investigation of variability of climatic elements of UrmiaLake basin, maximum and minimum daily temperature and daily precipitation data over period of 1984-2006 were analyzed. In this paper, 6 indices for analysis of temperature variability and 8 indices for analysis of precipitation variability ...
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For investigation of variability of climatic elements of UrmiaLake basin, maximum and minimum daily temperature and daily precipitation data over period of 1984-2006 were analyzed. In this paper, 6 indices for analysis of temperature variability and 8 indices for analysis of precipitation variability were used. The trends of these indices were specified using least square approach and for identifying their significance nonparametric, Man-Kendal test was used. Results indicate that over the study period climatic conditions have changed. The number of summer days and warm nights significantly increased with the number of cold days and cold nights reduction. Also total annual precipitation, number of precipitation days (above 2 mm) and number of heavy precipitation days (equal or above 10 mm) have significant reduction. Moreover, in the study period the number of consecutive wet days has significant reduction, but increasing of consecutive dry days is not significant.
