Probability of the effect of climate change on the graph of the intensity and frequency of effective precipitation in the regions of the northwest of Iran



Extended abstract
1- Introduction
Assessing the climatic characteristics and identifying the climatic elements and parameters of a region, can have a major role in programming and the welfare of that region. Effective Precipitation, as one of the most important climatic elements in the regions of the northwest of Iran with considerable temporal-spatial variations, has a major role in the way environmental, energy, and economic potentials are used. Therefore, predicting natural phenomena like flood and drought and the necessity of correctly recognizing atmospheric conditions and consequently presenting an appropriate solution for fighting natural hazards, has made programmers draw the effective precipitation clusters of this region.

In this research, for comparing the basic period (past) with the simulated data, first the statistics of the daily effective precipitation of the six stations of Ardebil, Ghazvin, Hamedan, Kermanshah, Sanandaj, and Tabriz, have been provided for a 30-year period (1961-1990) and on the other hand, have been compared with the simulated data of 2021 to 2050 that have been generated using the general atmosphere circulation model HADCM3 and the A1 scenario and been downscaled using the LARS-WG model. The method for comparing effective precipitations in different clusters was done based on the clustering in the form of 5 clusters for all the stations and study periods.

One of the results of this research is the greater concentration of effective precipitation for the cold periods of the year (winter and fall) and the increase of annual precipitation by the amount of 20.62 millimeters for the average of the period 2021-2050 compared to the basic period. Also, the results indicate the increase in the intensity of effective precipitation thresholds for the stations of Ardebil, Kermanshah, and Tabriz in future decades compared to the basic period 1961-1990 and the decrease in the number of days in which rain has fallen for Kermanshah, Sanandaj, and Tabriz for future decades. Then, for evaluating the two coordinates of precipitation percentage and cluster frequency percentage compared to a normal line (on each spot of this line the intensity of effective precipitations and the frequency of days are equal) their diagram was drawn.

The outputs of this section demonstrate that the effective precipitations of cluster 3 which have the features of light rain with average intensity, fall on this normal line for most of the stations and study periods. But the precipitations of cluster 1, are very heavy and intense, which in most cases have the most distance to the normal line. Therefore, the precipitations of the third cluster need optimal exploitation management and the precipitations of the first cluster need risk management and in some cases crisis management.