Assessing the changes in hydrological budget including anthropogenic effect estimated by the reanalyses and rain-gauge based precipitation data over Asia

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With the benefit of the reanalysis datasets, the 25-50 years change in atmospheric hydrological budget should be clarified, and increase in evapotranspiration (Et) caused by the increase in agricultural water use may be identified. Analyses have been done on the interannual change of hydrological budget over Asia, by using meteorological reanalyses data and a rain-gauge based grid precipitation dataset developed by the APHRODITE project (Yatagai et al., 2009), in which more than 4 times rain-gauge data available through the global telecommunication system (GTS) network is used and orographic precipitation is taken into account. As for the reanalysis, we used ERA40 data compiled by the European Centre for Medium Range Weather Forecast (ECMWF) and JRA25 compiled by Japan Meteological Agency. As a result, increase in evapotranspiration (Et) estimated as a residual between moisture convergence and precipitation is found at the semi-arid regions of China, Central Asia, Turkey and India etc, where the progress of desertification is reported. For some of these regions, these facts derived from the reanalysis and precipitation are consistent with the local reports that agricultural water use (irrigation by using river water, ground water, dam water) has been increased.