Spatial Distribution of Daily and Monthly Rainfall Concentration Indicators in Rain Gauge Stations of West Azerbaijan Province

Rainfall as a meteorological variable is studied in daily, quarterly, monthly and annual time scale, therefore understanding the changes in rainfall over different time periods is important to assess the risk of flooding and water resources managemnet. Occurance of a high percentage of rainfall in a short rainy day can increase the risk of flooding and soil erosion. Therefore, in this study, the spatial pattern of rainfall concentration was evaluated using daily rainfall concentration index (CI) and monthly rainfall concentration index (PCI) on an annual and seasonal scale in 26 rainfall stations of West Azerbaijan province for 41 years (1397-1356). Then, the zoning map of the concentration index on annual and seasonal scales were prepared using the Co-Kriging method and elevation data. According to the annual CI index, Alasgal station in the southeast of the province and primitive stations, Siah Cheshmeh and Razi in the west of the province had a uniform rainfall concentration, but according to PCI index, the northern and northwestern parts of West Azerbaijan province have more uniform distribution of monthly rainfall than the other study areas. The CIs at other stations had relatively similar values and did not differ much, indicating a positive correlation between the CI and PCI. The results also showed that annual changes in CI values are most associated with the percentage of annual rainfall that occurs during 15% of rainy days. Therefore, the daily heterogeneity of rainfall during a year is related to the best percentage of rainfall of 15% of rainy days in the study area, and the seasonal distribution of rainfall over a year can be justified to some extent by the heterogeneity of daily rainfall.