INVESTIGATING THE TEMPORAL CHANGES IN PRECIPITATION AND THE SPATIAL EXTENT OF CONSEQUENT FLOODING IN PAKISTAN

Abstract

Climate is changing on both temporal and spatial scales in many parts of the world. Especially, changes in the climate has impacted many natural phenomena including distribution and intensity of rainfall. Pakistan is no exception when it comes to the harmful impacts of climate change in the form of changing precipitation pattern, flooding, and droughts. Monsoon rainfall is the principle source of water in the Indian Subcontinent. For Pakistan, development and management of water resources is of great importance as rainfall is a seasonal phenomenon in the country. This study is primarily designed to analyze the extent of precipitation change, and the precipitation trends in Monsoon and Post Monsoon seasons in Pakistan over the monsoon belt. Furthermore, emphasis is made on linkage of monsoon rainfall and the consequent flooding extent using the satellite and ground base observations. The gridded rainfall data from Tropical Rainfall Measuring Mission (TRMM) along with rainfall data of 12 stations from Pakistan Meteorological Department (PMD) located in the northern monsoon belt of Pakistan were used to identify the spatial and temporal shift in monsoon pattern over Pakistan. However, spatial extent of the consequent floods was calculated by using the Moderate Resolution Image Spectroradiometer (MODIS) data. The results have shown that there is a slight decrease in monsoon rainfall with a sharp decrease in the number of rainy days. This trend depict that the intensity of rain is increasing but frequency is decreasing causing a higher probability of flash floods. Moreover, temperature is increasing over Pakistan’s monsoon belt in monsoon and decreasing in post monsoon season. Most stations show a decrease in rainfall with rise in temperature. Therefore, lesser rainfall in monsoon and more rainfall in post monsoon season is observed. This illustrates a kind of temporal shift in the monsoon rainfall in Pakistan. However, monsoon pattern seems to be shifted south-eastward spatially. The spatial extent of floods in the country is found to be dependable on total rainfall in monsoon catchment area in northern region (monsoon belt) each year. The year 2010 with 29% more rainfall above average have shown maximum spatial extent of floods (country wide) followed by the year 2015.