Impact of Horizontal Resolution of Topography on Asian Monsoon Water Cycle Simulated by MRI 60-km-mesh Global Atmospheric Model

Abstract:

We use a 60-km-mesh global atmospheric model (MRI-AGCM3.2) to investigate the impact of horizontal resolution of topography given on Asian Monsoon water cycle. We change horizontal resolution of topography from 60-km mesh (T_L319) to 560-km mesh (T_L31). It is found that JJA precipitation over South India, Arabian Sea, and Bay of Bengal between 10°N and 20°N becomes larger as the horizontal resolution of topography becomes coarser. In response to precipitation changes, vertically integrated water vapor flux also increases. Moreover, upper tropospheric temperatures over northwestern Tibetan Plateau become warmer. In addition to changes of the mean state, the timing of northward rain belt shift from Equatorial region becomes earlier as horizontal resolution of topography becomes coarser. It is also found that the time when Meridional Thermal Gradient, defined as the difference of temperature at 300hPa between 20°N-40°N and Eq.-20°N, changes from negative to positive becomes earlier. These changes seem to be related to different snow accumulation and meting process in different topography realizations, thus implying an importance of resolution and topography in the Asian monsoon simulations.