Performance and Applicability of Satellite Rainfall Estimation in Nepal

摘要

@@ 1. Introduction Owing to t he monsoon precipitation, diverse geological settings and r ugged terrain, Nepal is prone to flood and Iandslides. Ma ny lives and properties worth m illions of dollars are destroy ed. The monsoon season in Nepal occurs between Jun e and Septem ber; monsoon is the dominant rainfall season, with 80% of the annual rainfall occurring in that period. Based on 20 years of data (1980-2000), Nepal is found to have high vulnerability of flood disasters as reported in the UNDP global report on reducing disaster risk (UNDP 2004). Between 1983 and 2005, on average 309 people lost their lives in Nepal, due to floods and landslides that accounting for over 60% of those who died due to different types of disasters in the country. (Khanal et al, 2007) The high level of poverty and rate of po pulation gr owth has furt her increased the vul nerability to flood and landslides. Reliable weather forecasting systems are one of the most effective way s to m inimize the loss of life property. Accurate r ainfall esti mations are e ssential for reliable and timely wea ther forecasting and waming. In many countries weather forecasting has been relied upon by a dense network of rain gauge or ground based rainfall measuring radars that report in real time. In Nepal, like many other developing countries, the hydrom eteorological station networks are sparse and rainfall data are available only after a significan t delay . According to t he Department of Hydrology and Meteorology (DHM) of Nepal, the country average density is one gauge for about 33 I km2 and is especially very sparse in mountainous areas. Owing to the limited spatial coverage of ground base gauges, unavailability of real-ti me rainfall data and constraint in technical and financial resources operational flood forecasting is y et to be initiated. Precipitation is highly variable in both space and tim e and i s an im portant input in r ainfall-runoffm odeling. The availability of global coverage of satellite da to o ffers effectiv e and economical means of calculating areal rainfall estimates in sp arsely gauged areas (Artan et al., 2007b). Thus, satellite rainfall estimates (RFEs) may be one of the best and appropriate approaches for Nepal to p redict and forecast rainfall-induced runoff that may produce flooding.