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DOI | 10.5194/acp-2020-325 |
Influence of gravity wave temperature anomaly and its verticalgradient on cirrus clouds in the tropical tropopause layer - asatellite-based view | |
Kai-Wei Chang and Tristan L'Ecuyer | |
2020-05-05 | |
发表期刊 | Atmospheric Chemistry and Physics
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出版年 | 2020 |
英文摘要 | Negative temperature perturbations (T′) from gravity waves are known to favor tropical tropopause layer (TTL) clouds, and recent studies have further suggested a possible role of dT′/dz on facilitating TTL cloud formation and maintenance. With a focus on exploring the influence of dT′/dz on TTL clouds, this study utilizes radio occultation temperature retrievals and cloud detection from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) to understand how gravity wave perturbations modulate cloud occurrence. 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 (re) retrievals from the CloudSat/CALIPSO 2C-ICE product, we find that re is distributed similarly among all wave phases but a smaller mode is found in the re 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. |
领域 | 地球科学 |
URL | 查看原文 |
引用统计 | |
文献类型 | 期刊论文 |
条目标识符 | http://119.78.100.173/C666/handle/2XK7JSWQ/248828 |
专题 | 地球科学 |
推荐引用方式 GB/T 7714 | Kai-Wei Chang and Tristan L'Ecuyer. Influence of gravity wave temperature anomaly and its verticalgradient on cirrus clouds in the tropical tropopause layer - asatellite-based view[J]. Atmospheric Chemistry and Physics,2020. |
APA | Kai-Wei Chang and Tristan L'Ecuyer.(2020).Influence of gravity wave temperature anomaly and its verticalgradient on cirrus clouds in the tropical tropopause layer – asatellite-based view.Atmospheric Chemistry and Physics. |
MLA | Kai-Wei Chang and Tristan L'Ecuyer."Influence of gravity wave temperature anomaly and its verticalgradient on cirrus clouds in the tropical tropopause layer – asatellite-based view".Atmospheric Chemistry and Physics (2020). |
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