Geographical Research

Unusual periods of heavy rainfall in Iran with climatic variation in each part of the country are very important.The heavy rainfall always have been one of the hazards of climate That the destruction and irreparable damages life and property is involved. Therefore, understanding the factors and parameters that create the climate system precipitation in any place and at any time of the year, especially transitional period is necessary. Rainfall phenomenon is very complex and nonlinear that the great variability over time and space and a variety of conditions that have important role in the occurrence can be divided into two categories: Synoptic Patterns and local conditions. Weather is largely controlled by the passage of Synoptic Patterns. On the other hand the occurrence of any weather's particular pattern is to a large extend determined by the distributions of land masses, sea surface temperature gradients,Characteristics and type of land cover (biosphere), topography and the orientation of baroclinic zones. The objective in this paper is analysis of synoptic patterns and vertical profiles of air in local heavy rainfall in South East of Iran including Sistan and Baluchestan, Kerman, Hormozgan and South Khorasan provinces. In the summer, synoptic patterns of seasonal rains in South East of Iran often Due of the spread of monsoon air mass. In winter, westerly winds extend towards lower latitudes including the study area; the seasonal rainfall pattern in the region brings.

In this study, the main question is that the synoptic patterns of rainfall during the transitional period (spring and summer) how do they arise? And what are the characteristics?
Data and Methodology: The purpose of this research is analysis of synoptic patterns and vertical profiles of air in local heavy rainfall in South East of Iran. Meteorological stations studied in this article are located in four provinces including Sistan and Baluchestan province, Kerman province, Hormozgan province and South Khorasan province. Review of daily precipitation data of 31 meteorological stations during (1981-2013) showed that heavy rainfall occurred in October 1390 in South East of Iran, one of the heaviest rain falls during transitional period is local function and the amount of rainfall is greater in most of the stations to compared whit the normal monthly rainfall. To investigate the Characteristics of meteorological parameters in rainyday and the days before rainyday, initially thermodynamic diagrams were analyzed. To determine the synoptic pattern, Weather maps up to 250 hPa Geopotential were examined. Thermodynamic diagrams in rainy days as compared to the days before rainy days showed that the temperature and air pressure has dropped; Relative humidity and dew point temperature has increased. Thermodynamic diagrams in rainy days as compared to the days before rainy days showed that the temperature and air pressure has dropped; Relative humidity and dew point temperature has increased.
Results and discussion: The results of the plot Ski-T, height of FCL and LCL, altitude difference Cloud top relative to the FCL and the amount of Dynamic indices: KINX, SHOW, CAPE, was Show prepared for the unstable Weather conditions. Calculation of instability indices showed that the convection factor was a supporting role in the occurrence of such precipitation, because when convective precipitation is the main factor the Convection is enough intensity and provide the instability needed to create precipitation. Synoptic pattern analysis suggests the establishment of Cut off low. The cut-off low is a cold low (depression) in mid-latitudes (occasionally almost in subtropical latitudes) where air of polar origin is cut off from the main subpolar belt of low pressure and cold air, the normal track of depressions. Cyclonicity around the the core of Cut off low and South wind flow on the eastern edge of Cut off low, arrangements for air convection is unstable in South East of Iran. Cut off low activity from this point is very important, which complements the summer rainfall caused by the monsoon system and winter precipitation caused by western cyclones can play a significant role for autumn rains transitional period In South East of Iran. Calculation of instability indices showed that the convection factor was a supporting role in the occurrence of such precipitation, because when convective precipitation is the main factor the Convection is enough intensity and provide the instability needed to create precipitation. Synoptic pattern analysis suggests the establishment of Cut off low. The cut-off low is a cold low (depression) in mid-latitudes (occasionally almost in subtropical latitudes) where air of polar origin is cut off from the main subpolar belt of low pressure and cold air, the normal track of depressions. Cyclonicity around the the core of Cut off low and South wind flow on the eastern edge of Cut off low, arrangements for air convection is unstable in South East of Iran. Cut off low activity from this point is very important, which complements the summer rainfall caused by the monsoon system and winter precipitation caused by western cyclones can play a significant role for autumn rains transitional period In South East of Iran.