Abstract

One of the study approaches in climatolog  is to investigate the  relationship of climatological elements. Various methods have been used.  One of these methods is using probability rule to find this relations. This paper attempts to find and investigate the relationship of daily precipitation and temperature status in Iran based on conditional probability method . In order to achieve the aim of the paper, Esfazari database, version one, with daily time resolution of 1961/3/21 up to 2004/12/31 which collected based on 1436 synoptic  climatic and precipitation stations and by using Kriking interpolation method with time resolution of 15×15 km and 7187 cells , have been used. stations   has been used. This database has been established using 1436 stations over Iran Based on probability distribution related to the temperature of each cell, Probability distributions of every pixel and their 25 and 75 percentiles of temperature have been estimated. At each cell, the days with daily temperature of less than 25, was the cold day and the days with percentile equal or more than 75 was considered as hot days  and the daily temperature between 25 and 75 percents is considered as a day with optimum temperature. so that seasonal specification of  temperature has been shown in this definition. Accordingly the cold, moderate and hot days have been defined as well as the no precipitation, low precipitation and high precipitation days based on mean of probability distribution in every pixel. So that, the lack, shortage and high precipitation has been recognized. At the next step, the frequency together with temperature and precipitation events of each day was presented in a matrix. Then the matrix of the probability of each precipitation – temperature events in relation with any status of precipitation was calculated. On this basis, the probability of occurrence of each precipitation classes at each three  seasons of warm and cold and transition for each pixel of Iran’s map have been estimated. Finally the conditional probability of each temperature occurrences with precipitation status for each pixel have been calculated and the relevant analysis and maps of each status has been presented. This feature shows the precipitation status for each season. The current research, while indicating the climatic facts, also has approved and showed the findings of Iranian’s climatologists as quantitative and probability.  Maximum precipitation in cold season in 36% of Iran with probability of 30%-40% and the days with no precipitation covers about 43% of Iran. In warm season, about 97% of Iran has no precipitation in 50-90 percent of days and 3% of country experienced this situation about 20-50 percents of the days. Meanwhile about 17% of country 40-60 percents of days and 56% of country 30-40 percents of days have low precipitation amounts. During fall and spring about 78% of Iran area has 60-90 percents of days without precipitation, 10-30 percents with heavy precipitation and 20-30 percents with low precipitation.    کلیدواژگان [English] اProbability, Conditional Probability, Temperature and Precipitation Attitude, No-Precipitation day, High-Precipitation day