عنوان مقاله [English]
One of the most important consequences of climate change is the increase in the frequency of climate hazards such as floods, droughts, rising sea levels, tropical cyclones, heat and cold waves, heavy rainfall, dust storms, etc.; The most common of them in Iran are floods and droughts. The aim of this study was to investigate the spatio-temporal variations of drought intensity in the Caspian basin. In this study, the GPCC global precipitation database was used with a spatial resolution of 0.5° × 0.5° from 1951 to 2013. One of the highlights of this study is the use of network data in the long term scale to investigate spatio-temporal variations of drought intensity in the Caspian basin. Then, by coding in Matlab software, the data required to estimate the RAI drought index in the basin during the statistical period were converted into a matrix. Then the amount of rainfall anomaly index (RAI) in monthly, seasonal and annual timescales was estimated to investigate the spatio-temporal variations of drought intensity. To analyze the precipitation temporal trend, averages of annual, seasonal and monthly were prepared from the data obtained from this database and non-parametric Mann-Kendall test was performed on monthly, seasonal and annual timescales. The results showed that in terms of the temporal observed drought of mild, moderate, severe and extreme occurred during the statistical period and in terms of spatial drought with mild intensity in all months, seasons and annual scale in most areas of the Caspian basin. At the same time, in May, moderate drought is evident in the southeastern heights of the Sefidrood sub-basin. Analysis of the Caspian basin rainfall trend in monthly time series also shows a significant decreasing trend in March and the annual scale in this basin.