Rainfall estimation using satellites comes to South Asia

A five-day workshop on ‘Application of Satellite Rainfall Estimation in the Hindu Kush-Himalayan (HKH) region’ concluded recently in Kathmandu, Nepal. Technical experts from national hydrological and meteorological services and academic institutions in Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, and Pakistan were joined by experts from the US National Oceanic and Atmospheric Administration (NOAA), U.S. Geological Survey (USGS) and Japan, to develop the application of satellite rainfall estimation methods in the countries of the Hindu Kush-Himalayan region. The workshop was a step towards improved forecasting of floods and monitoring of droughts by improving estimation of rainfall using advanced remote sensing tools. At present, rainfall measurements in the mountain regions of the extended Himalayan change are very limited as large parts of the region are poorly accessible and have limited infrastructure, and there are very few ground-based monitoring stations. But it is this rainfall that is mainly responsible for the downstream floods in South Asia.

Sponsored by the US Agency for International Development’s Office of U.S. Foreign Disaster Assistance (USAID/OFDA) through a Subaward with the University Corporation of Atmospheric Research (UCAR), and organised by the International Centre for Integrated Mountain Development (ICIMOD) in Kathmandu, the workshop held from 15-19 December 2008 was a part of the second phase of a project on Application of Satellite Rainfall Estimation (SRE) in the HKH region which will run from December 2008 to June 2010. The Phase 2 project builds upon the outcomes of, and seeks to address the gaps identified in the first phase. The aim is to conduct rigorous validation of the satellite rainfall estimates developed by the NOAA Climate Prediction Centre for various rainfall regimes, and to improve the satellite-based rainfall estimates and apply them to the stream-flow model developed by USGS to simulate the flooding in the greater Himalayan region. The five-day workshop reviewed the achievements of the first phase on validation of rainfall estimates and testing of the USGS stream-flow model in pilot catchments. The workshop contributed substantially to strengthening the capability of member countries to work with satellite rainfall estimates, and furthered the training in and transfer of the NOAA/USGS technology to the partners. The hydrologists and meteorologists of the Himalayan region were able to discuss and clarify difficulties in validation of satellite rainfall estimates in their respective countries and come up with practical applications for drought and flood monitoring in partnership with ICIMOD, NOAA, and USGS.

Accurate estimates of rainfall are needed to forecast floods and droughts, and minimise their impacts. Until recently, the main method used to estimate rainfall in an area was interpolation of measurements from a network of hydro-meteorological stations. The closer the spacing between stations, the more accurate the total rainfall estimate. In mountainous areas, however, measuring stations are often few and far between, and the available rainfall information is inadequate for forecasting floods with any certainty. The Himalayan satellite rainfall estimation projects will help countries in the region to estimate rainfall better using satellite observations, and will assist the countries to build and enhance their capacity in rainfall estimation and applications. It is hoped that the improved rainfall estimates will contribute to enabling reliable and timely flood forecasts and warning, and contribute to minimising loss of life and property in the region.