Rainfall is the most critical and key variable both in atmospheric and hydrological cycle. Its patterns usually have spatial and temporal variability. These variabilities affect agricultural production, food security, water supply, transportation, environment and urban planning, thus, the entire economy of a country, and the existence of its people. Rainfall variability is assumed to be the main cause for the frequently occurring climate extreme events such as drought and flood. It is already imposing a significant challenge so far worldwide. Awareness about the characteristics of the...