Changes effective components in peak rainfall Iran

Changes effective components in peak rainfall Iran. Introduction Since the spatial and temporal distribution of rainfall in Iran is influenced by the distribution of global circulation systems, the slightest change in its pattern is the severe weather abnormalities. Therefore, spatial and temporal abnormalities of rainfall and extreme changes in rainfall intensity and differences in precipitation types are one of the main characteristics of Iranian rainfall. Climate change is one of the problems of human society and is a threat to the planet Earth. The increase in the temperature of the earth has caused profound and extensive changes in the Earth's climate, causing changes in the time and place of precipitation, which has caused a lot of damage, especially in the last decade. The purpose of this study was to identify and study the changes in the heavy rainfall component of Iran in relation to changes in the systems middle tropospheric. Materials and methods First, the daily rainfall data of 53 synoptic stations were received from the country's Meteorological Organization from 1984 to 2013. The cluster analysis and zoning were done using Euclidean distance method and Ward's method was used. For zoning based on cluster analysis, seven variables of rainy day (one day, two consecutive days, three consecutive days, four consecutive days, five consecutive days, six consecutive days and seven days of continuous rainfall) were used. The final result was the division of the country into 3 regions according to the number of days. In the following, data from the upper atmosphere levels were used to investigate changes in the mechanisms of rainfall formation. Includes discovery data of geopotential heights, u wind, v wind, omega, level, 500 hpa, and specific humidity level 700 at daily average and 1 * 1 degrees from the European Center for Medium Term Forecast ( ECMWF) received. The statistical period of study was divided into two periods of 15 years (first study period 1984-1998 and second study period 1999-2013), The peak days for each area were determined in each of the two time periods. And for each time period The peak of rainfall was 5 days. Then, the synoptic parameters were analyzed and compared in each study period. Discussion In area 1 in the second study period, the range of trough decreased and the depth of trough increased. The central core of geo potential heights in the first time period is greater than the second period of study, in other words, the core in the first period is 5400 geo potential meters, which in the second interval decreased to 5350 geo potential meters. In area 2, in the second period of studies, the high elevation in the convergence region of the Arabian Sea is more shallow and in a more inappropriate position than the first pattern. In area 3, in the second study period, northwest of Iran is located behind the trough, and cold weather is falling and the rainfall in this part of the area is low. In 3 areas, in the second period of studies, the amount of moisture has decreased and caused the rainfall of the second interval to decrease compared to the first interval. Conclusions In the second period of studies (1999-2013), the range of trough has decreased and the depth of trough has increased. The Omega component study showed that in the second study period, the mean omega-negative peak of the peak days of the target area was reduced. The Omega component study showed that in the second study period, the mean omega-negative in the target area was reduced. It was also found that the direction of the wind streams in the second period was reduced due to the flow Linear more of the amount of precipitation. The amount of moisture in the second period of study has also decreased and has caused the second period rainfall to decrease over the first period. In the study of the synoptic components of area two, it was found that in the second period of studies (1999-2013), located on the convergence area of the Arabian Sea, is more shallow and in a more inappropriate position than the first pattern. And caused the maximum moisture content to fall to 5 grams per kilogram. In the study of the synoptic components of the third region, it was found that in the second study period, the study area, especially the northeast of the country, is somewhat ahead of the trough, and the average annual precipitation in this part of the area is increasing in the second period. And the northwest of Iran is located behind the trough and the cold weather has fallen. The rainfall in this part of the area has decreased. Keywords: Zoning, mechanism of precipitation. Middle troposphere, Iran.