资源环境科技发展态势分析平台

Cloud populations were evaluated in four phases corresponding to positive or negative T′ and dT′/dz. We find that 57 % of TTL clouds are found where T′ and dT′/dz are both negative. Regions of frequent convection are associated with higher cloud populations in the warm phase T′>0. The partitioning of cloud population among wave phases shows some dependence on the background relative humidity estimated using Aura Microwave Limb Sounder water vapor retrievals. Using effective radius (r_e) retrievals from the CloudSat/CALIPSO 2C-ICE product, we find that r_e is distributed similarly among all wave phases but a smaller mode is found in the r_e distribution from the phase T′<0 and dT′/dz<0.

It is shown that the strongest mean negative T′ anomaly is centered on the cloud top, resulting in positive dT′/dz above the cloud top and negative dT′/dz below. This negative T′ anomaly propagates downward with time consistent with upward propagating gravity waves. Negative (positive) T′ anomalies are associated with increased (decreased) probability of being occupied by clouds. The magnitude of T′ correlates with the increase or decrease in cloud occurrence, giving evidence that the wave amplitude influences the probability of cloud occurrence. While the decrease of cloud occurrence in the warm phase is centered on the altitude of T′ maxima, we show that the increase of cloud occurrence around T′ minima occurs below the minima in height, indicating that cloud formation or maintenance is facilitated mainly inside negative dT′/dz. Together with existing studies, our results suggest that the cold phase of gravity waves favor TTL clouds mainly through the region of wave anomalies where dT′/dz is negative.