Mean Climate States and Their Resolution Dependences in a 20-km-mesh Global Atmospheric Climate SimulationsPrimary Author: Mizuta, Ryo
Additional Authors: Kazuyoshi OOUCHI, Hiromasa YOSHIMURA, Shoji KUSUNOKI, and Akira NODA
Mean Climate States and Their Resolution Dependences
in a 20-km-mesh Global Atmospheric Climate Simulations
Ryo MIZUTA (1,2), Kazuyoshi OOUCHI (1,2)
Hiromasa YOSHIMURA (2), Shoji KUSUNOKI (2), and Akira NODA (2)
(1) Advanced Earth Science and Technology Organization, Japan
(2) Meteorological Research Institute, Japan
A global atmospheric general circulation model with the horizontal grid size of about 20 km has been developed, making use of the Earth Simulator, one of the fastest computers available for meteorological applications. We examine the model's performance of simulating the present day climate from small scale through global scale by time integrations of over 20 years using a climatological sea surface temperature as a boundary condition.
Global distributions of the seasonal mean precipitation, surface air temperature, geopotential height, zonal-mean wind and zonal-mean temperature agree well with the observations. By increasing horizontal resolution, the model improves the representation of regional-scale phenomena, such as tropical cyclones and Baiu fronts, and that of local climate and extreme events, due to better representation of topographical effects and physical processes.
Although most characteristics of global climate do not depend on resolution, the amount of precipitation in the tropics increases, corresponding to a warm bias in the tropical upper troposphere. The increase is seen in precipitation from grid-scale condensation, but it is not balanced with the decrease of precipitation from convective parameterization scheme. Dependence on horizontal resolution is also seen in a meridional contrast of specific humidity between tropical upper troposphere and polar lower stratosphere. Difference in water vapor transport by synoptic disturbances can cause the resolution dependence.
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