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1- , soheila_shirmohamady@yahoo.com
Abstract:   (3208 Views)
understanding the behavior of extreme events is one of the main aspects of climate change.
In this research, we used network data from interpolation daily rainfall observation of 823 meteorology stations from January 1st up to December 31st, 2016 by using Kriging interpolation method and by separating 6×6 km spatial. The results formed matrix interpolation process by dimension of 18993×6410. This matrix has the rain status of 6410 points of west of Iran for every day rainfall(18993). Extreme rain falls are identified in terms of threshold of 95 percentile in each point and each day of year. for studying extreme rain fall portion in total yearly rainfall, the total of equal rainfalls and more than 95 percentile is calculated for each year and each of pixel and, it is divided to total of the same pixel rainfalls in that year. We used the least squarely error for understanding temporal- spatial behavior of regression. By increasing geographical latitude in Iran's western provinces, it is decreased both of total extreme rainfalls and portion of such rainfall out of total yearly rainfall. Total extreme rainfall trend shows a frequency in a domain with 16 mm in each year. The negative trend of total rainfall with the area of 74.72 percent consists of three quarters of Iran's west. The narrow strip of the west of Kurdistan and south-west of west Azerbaijan have the highest amount of positive trend which is meaningful in certainty level of 95 percent. The study of process showed the ratio of extreme rainfalls portion to total yearly rainfall, which is increasing about 60.7 percent of west area of  this country extreme rainfalls in total yearly rainfall and the greatest part of this area is located in southern half of the studied area. The negative trend also is located in northern half and they have consisted of 39.29 percent of studied area of these, only in 29.81 percent of region, the trend ratio of extreme rainfalls to total yearly rainfalls are meaningful in certainty level of 95 percent.

Received: 2019/12/1 | Accepted: 2019/12/28

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