Climate Change Research

Climate Change Research

Analysis of Variability of Individual Seasonal Index and Rainfall Regime Patterns, Case Study: Khorramabad

Document Type : Original Article

Author
Taghi Tavousi
Professor, Geography Department, University of Sistan and Baluchestan, Zahedan, Iran
10.30488/ccr.2024.462888.1227
Abstract
The purpose of the current study is the analysis of variability of seasonal index (SI) and patterns of rainfall regime in Khorramabad city. In this regard, the monthly rainfall data of 70 years, during (1951-2020) have been selected from Khorramabad meteorological station. In order to identify the variability of seasonal patterns of precipitation, the studied statistical period was divided into two halves and also into seven decades. At first, the general characteristics of monthly, seasonal and annual rainfall were analyzed using drawing techniques. Then, precipitation concentration index (PCI) and individual seasonal index (SIi) have been estimated and the trend of these indices has been investigated. The length of the months with maximum rainfall and the variation range of the individual seasonal index (SIi) were evaluated using the ratio between the average seasonal index (S̅I̅) and the mean individual seasonal index (S̅I̅i) for each decade. The results showed that the rainfall regime of Khorramabad is winter (cold half of the year), and the average seasonal index (S̅I̅) showed that the local rainfall regime is seasonal (a dry period and a wet period). Regression analysis of the individual seasonal index (SIi) with the total annual precipitation shows a statistical inverse linear correlation. The time series trend of the (SIi) was examined to verify that no significant change in the seasonal rainfall regime occurred. However, the interannual changes of individual seasonal index (SIi) have caused four different seasonal patterns in the rainfall regime of Khorramabad. In general, it can be said that the patterns of the seasonal regime in Khorramabad have fluctuating behavior, intermittently decreasing or increasing the period of rainfall.
Keywords
Precipitation Concentration Index
Rainfall Distribution
Rainy period
Climate
Periodic

Subjects

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