A Sensitivity Study of Regional Climate Simulation to Convective Parameterization Schemes for the 1998 East Asian Summer Monsoon

Abstract

A sensitivity study of regional climate simulations over East Asia to three convective parameterization schemes (CPSs), the Grell, Kain-Fritsch, and Anthes-Kuo schemes, was conducted using a regional climate model, SNURCM with a 60 km horizontal resolution. Nesting experiments with a 20 km horizontal resolution were also performed in order to investigate the sensitivity of CPSs to horizontal resolution.

In all runs with 60 km horizontal resolution, seasonal mean precipitation, low- and upper-level wind, and temporal and spatial variation of monsoon fronts over East Asia were simulated with a certain difference between CPSs. With higher horizontal resolution, all the schemes were likely to increase slightly the total precipitation amount and the precipitation intensity due to the increase of convective rain, but differences in the spatial distribution of precipitation between CPSs were relatively small. There were prominent differences in vertical profiles of wind, temperature, water vapor, and atmospheric hydrometeors amongst CPSs, although the vertical structures of those in GR and KF runs were similar to each other. Sensitivities of the vertical structure of most atmospheric variables to horizontal resolution were relatively smaller than they were to CPSs except for cloud water. Surface energy fluxes, in particular incoming solar radiation and latent heat between CPSs were different to each other because of differences in the vertical structure of atmospheric hydrometeors. Diurnal variation of precipitation was also sensitive to not only CPSs but also horizontal resolution.

In this study, the AK scheme reproduced the East Asian Summer precipitation properly because of intrinsic triggering assumptions and the spectral nudging technique. The GR scheme was on the whole suitable to simulate the general features of East Asian summer monsoon in 1998 such as heavy precipitation, atmospheric vertical structure, and temporal evolution of the East Asian Summer monsoon. The KF scheme had the worst statistics in precipitation simulation due to large convective precipitation portion. Consequently, the AK and GR schemes simulated more reasonably the 1998 summer flood over East Asia which was affected by anomalous large-scale conditions.

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