2つの積雲対流パラメタリゼーションのGCMによる感応実験

Abstract

To examine the sensitivity of the simulated large-scale structures to the Betts-Miller and the Arakawa-Schubert cumulus parameterizations, a series of 6-month integrations are performed using the CCSR/NIES atmospheric general circulation model with a horizontal triangular resolution of 21 and 20 vertical levels. The model results are time-averaged for the last three months, that is, June-July-August mean. Comparisons between the simulations using the Betts-Miller scheme and the Arakawa-Schubert scheme indicate that although the simulated large-scale structures are generally similar to each other, there are some noticeable differences. These include the temperatures in the middle and upper troposphere at mid-latitudes in the northern hemisphere, the location of the maximum convective heating in the tropical deep connective region, the convective heating/cooling in the boundary layer, the precipitation distribution pattern over the tropical western Pacific and the vertical profile of the vertical turbulent heat transport. Sensitivity experiments with different adjustment parameters in the Betts-Miller scheme show that the precipitation distribution pattern over the tropical western Pacific is very sensitive to the adjustment time scale and stability weight as well as the saturation pressure departure. It is also shown that the partition between the convective precipitation and the large-scale precipitation is most sensitive to the saturation pressure departure.