| A compensation scheme on shallow convection clouds including both cloud cover and hydrometeor has been designed and tested in the GRAPES-Meso model on the basis of the improved shallow convection parameterization scheme by Wan Z W et al.(2015), to improve the deficiencies on the low level cloud cover and on the cloud radiation effects of shallow convection. Results of this study show that :1) The introduced diagnostic method on shallow convective cloud cover performs reasonably well; there is corresponding cloud cover in the triggering areas of shallow convections, and the deviation from model simulated cloud cover to satellite observed one could be reduced by the improved scheme. 2) The compensations of the cloud cover and the hydrometeor exist in the shallow layer of 0.5-4 km above the ground, corresponding to the active layer of shallow convection; the maximum of cloud compensations at the height of 1-1.5 km, and the proportion of compensated cloud hydrometeor(the sum of cloud water content and rain water content) to the total is about 20-55%. 3) There is a reasonable response of cloud optical depth to the compensations of the cloud hydrometeor in lower troposphere; the vertical profile of the cloud optical depth’s increments and its variation trend with integration time are very similar to those of the cloud hydrometeor compensation, and the variation of the cloud optical depth depends much more on the change of cloud water content than that of rain water.4) In the daytime, the cloud radiation effects from the shallow cloud compensation relevant to the shallow convection are clear in reducing the surface total solar radiation and the 2 meter temperature, therefore, decreasing the biases of model simulated those values. The positive effect of this improved scheme, on minimizing forecast bias of cloud cover、the surface total solar radiation and the 2 meter temperature of the GRAPES-Meso, is corroborated by verification results of one-month forecast experiment. |
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