GRAPES-Meso模式浅对流云辐射效应的改进试验

在万子为等（2015）对GRAPES-Meso模式浅对流参数化改进的基础上，进一步引入了浅对流云量诊断计算，并设计旨在完善浅对流云辐射效应的浅云云量和云中水凝物的补偿方案，以改进模式低层云量偏少和浅对流云辐射效应不足的问题。通过对数值试验结果的诊断和对比分析以及与观测的比较，重点考察了浅对流云量计算与浅对流激发的协调性、浅对流云对低云补偿后所产生的辐射效应以及对模式地面要素预报的影响等，验证了改进方案的合理性与有效性。结果表明:（1）浅对流云量诊断计算合理，其云覆盖区与浅对流激发区相吻合，引入浅对流云量的计算可减小模式云量的计算偏差、使其向观测结果靠近；（2）改进方案在浅对流发生区低层0.5-4 km高度范围内，对影响模式云辐射过程的浅云云量和云中水凝物形成有效补偿，最明显的浅云补偿在1-1.5 km高度处，浅对流活跃时期浅对流过程对浅云水凝物（云水和雨水之和）的补偿量可达20%-55%；（3）云光学厚度对浅云水凝物的补偿响应合理，即水凝物的补偿引起云光学厚度增大，两者的变化特征在时空分布上十分相似，且云光学厚度之变化受云水补偿的影响比受雨水补偿的影响更明显；（4）在白天时段，浅云补偿所产生的辐射效应使模式地表太阳总辐射有所下降，缩小了与观测的偏差，进而使地表温度和地面2 m气温模拟偏差减小。改进方案在缓解模式云量偏少、地表太阳总辐射偏强和地面2 m气温偏高等方面的作用，在批量试验中得到了验证。 

An improvement on the radiation effects of shallow convective clouds in GRAPES-Meso model

A compensation scheme on shallow convection clouds including both cloud cover and hydrometeors has been designed and tested in the GRAPES-Meso model on the basis of the shallow convection parameterization scheme modified by Wan, et al (2015). The purpose of this work is to improve simulation deficiencies on the low-level cloud cover and cloud radiation effects of shallow convection. Results of this study showed that:(1) The introduced diagnostic method performs reasonably on the simulation of shallow convective cloud cover; there is corresponding cloud cover in the triggering areas of shallow convection, and the deviation of the model simulated cloud cover from satellite observation is reduced by the improved scheme. (2) Compensations of cloud cover and cloud hydrometeors exist in a shallow layer that is about 0.5-4 km above the ground, corresponding to the active layer of shallow convection; the maximum of cloud compensations occurs at the height of 1-1.5 km, and the proportion of compensated cloud hydrometeors (the sum of cloud water content and rain water content) to the total is about 20%-55%. (3) There is a reasonable response of the cloud optical depth to the compensations of cloud hydrometeors in the lower troposphere; the vertical profile of the increment in the cloud optical depth 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 more on the change in cloud water content than on the change in rain water. (4) In the daytime, the cloud radiation effects from the shallow cloud compensation relevant to shallow convection are clearly reflected by decreases in surface total solar radiation and 2 meter air temperature. As a result biases of these variables in the model simulation decrease. The positive effect of this improved scheme on reducing biases of the GRAPES-Meso simulation of cloud cover, surface total solar radiation,and 2 meter air temperature has been confirmed by verification results of a 1-month forecast experiment.