The Lifecycle of Anvil Clouds and the Top-Of-Atmosphere Radiation Balance over the Tropical West Pacific

[摘要] Observations from a geostationary satellite are used to describe the lifecycle of mesoscale convective systems (MCS), their associated anvil clouds, and their effects on the radiation balance over the warm pool of the tropical west Pacific Ocean. In their developing stages, MCS primarily consist of clouds that are optically thick and have a negative net cloud radiative effect (CRE). As MCS age, ice crystals in the anvil become larger, the cloud top lowers somewhat, and clouds with neutral and positive net CRE become more common. Shading from anvils causes cool anomalies in the underlying sea surface temperature (SST) of up to -0.6 °C. MCS often occur in clusters that are embedded within large westward-propagating disturbances, so shading from anvils can cool SSTs over regions spanning hundreds of kilometers. Triggering of convection is more likely to follow a warm SST anomaly than a cold SST anomaly on timescales of several days. This information is used to test hypotheses on why, over the warm pool, the average shortwave and longwave CRE are individually large but nearly cancel. The results are consistent with the hypothesis that the cancelation in CRE is caused by feedbacks between cloud albedo, large-scale circulation, and SST.

[发布日期] 2018-11-28

[学科分类] 大气科学

[关键词] ANOMALIES;ANVIL CLOUDS;ANVILS;ATMOSPHERIC RADIATION;CONVECTION;CRYSTALS;EMBEDDING;ENERGY BUDGETS;FEEDBACK;GEOSYNCHRONOUS ORBITS;HYPOTHESES;MESOSCALE PHENOMENA;PACIFIC OCEAN;SEA SURFACE TEMPERATURE;TROPICAL REGIONS