Numerical Study of the Impacts of Land Use/Cover Changes Between 1700 and 1850 on the Seasonal Hydroclimate in Monsoon Asia

This study investigated the impacts of historical land use/cover changes (LUCC), from forest to cultivated land, on the seasonal cycle of the hydroclimate over the Indian subcontinent and southern China. The mechanism of these impacts was studied by conducting numerical experiments using an atmospheric general circulation model MIROC3.2 coupled with the land surface scheme MATSIRO and historical global land use/cover changes between 1700 and 1850. A previous study found a decrease in summer (JJA) precipitation over the Indian subcontinent and southern China induced by extended cultivation between 1700 and 1850. We further found that evapotranspiration in the Indian subcontinent notably decreased, particularly in the spring, while that in southern China discernibly decreased throughout the year. The difference in the changes in evapotranspiration in the spring over both regions could be explained by the amount of precipitation during the dry season. In the Indian subcontinent, the marked decrease in evapotranspiration in May due to LUCC caused the decrease in precipitation during the same season. However, in southern China, the decrease of precipitation from March to April was contributed rather by the decrease of water vapor flux convergence due to atmospheric circulation changes than by the decrease of evapotranspiration.