Diurnal-to-seasonal characteristics of surface energy balance and temperature in East Asian summer monsoon simulations

摘要

We used regional climate model simulations of the East Asian Summer Monsoon (EASM) to study diurnal-to-seasonal characteristics of the surface energy balance and temperature, and their relationships to clouds and surface soil moisture. Simulations were performed for the period May through September 1988 and 1989, 2 years with significant differences in observed surface air temperature, radiation, and clouds over the Yangtze-Huai River Valley (YHRV), which are realistically reproduced by the model. Differences in daytime evolutions of the YHRV surface net radiation, heat fluxes, and surface air temperature between 2-year summers result mainly from fluctuation of shortwave cloud radiative forcing. Clouds dominate daily variability of the YHRV surface net solar radiation, surface net radiation, and latent heat, generally accounting for above 80% of the total variances. Consequently, they are more effective in damping the diurnal temperature range by reducing daytime maximum temperature as compared to surface soil moisture. Both clouds and soil moisture exhibit small effects on nighttime minimum temperature, which is largely controlled by the greenhouse effect of the atmospheric water vapor. Surface energy balance components and temperature evolve with the march of EASM, which is quite different between 2 years. The comparative analyses of observations and other available data can generally validate the major conclusions from the simulations.