Meteorological Drought and Flood Assessment Using the Comparative SPI Approach in Asia Under Climate Change

The standardized precipitation index (SPI) has been used to monitor and analyze meteorological droughts using long-term monthly precipitation from national meteorological and hydrological services on multiple timescales. Instead of evaluating climatic impacts with separately-computed SPI for present and future climates, we introduced the comparative SPI (cSPI) computed using target (future) datasets on the basis of a reference (present) dataset. The cSPI approach evaluates standardized precipitation change in one dataset for different periods and for different datasets in a common period. Using 12-month cSPI, we investigate the change in central conditions and in the probabilities of dry and wet conditions between present and future climates. Meteorological drought and flood hazards in Asia are examined with MRI-AGCM3.2S, a 20-km mesh global atmospheric model, time-slice experiments of the present (1979-2003) and future (20752099) with four different sea surface temperature patterns. As one result indicates, the median of the 12-month cSPI shifts to severely dry around the Mediterranean Sea to the Persian Gulf, and to extremely wet in the Tibetan Plateau, North and South India, and around the Yellow Sea. Therefore, we conclude that the cSPI approach is a useful way to characterize both future drought and flood hazards under climate change.