Quasi‐2‐Day and Diurnal Cloud Variation Timescales Over Convectively Active Regions
Quasi‐2‐Day and Diurnal Cloud Variation Timescales Over Convectively Active Regions
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DOI：
10.1029/2021jd035426
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发表时间：
2021-10
期刊：
影响因子：
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通讯作者：
Hungjui Yu;K. Rasmussen;H. Kuo
中科院分区：
文献类型：
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作者：
Hungjui Yu;K. Rasmussen;H. Kuo
利用1998年1月至2019年12月的高分辨率卫星红外亮温（IRBT）观测资料，研究了准2日（Q2 D）和日变（DC）时间尺度上云变率的气候特征。Q2 D和DC信号的分布之间明显的陆地-海洋对比是明显的。逐日驱动的云活动主要发生在陆地和山区，Q2 D时间尺度在热带海洋盆地和通常观察到有组织对流的陆地上更为突出，例如温暖季节的刚果和亚马逊雨林，美国和南美洲亚热带地区。Q2 D变率和海表温度（SST）之间的长期关系表明，在较高的SST环境中，云在Q2 D时间尺度上更加活跃。Q2 D变率与1998年至2019年的印度洋偶极子（IOD）和厄尔尼诺/南方涛动（ENSO）有很好的相关性。云变率与对流可用位能（CAPE）值的范围进行了分析。在陆地上的结果表明，增加Q2 D云变率出现更高的CAPE，这表明Q2 D和有组织的对流的重合，特别是考虑到这种效果是最强的地区与频繁的中尺度对流系统（MCS）在世界各地。云变率和Q2 D时间尺度分析为理解中尺度对流系统的全球特征提供了另一种视角。总的来说，这项研究客观地考察了与日周期和较长寿命的对流系统相关的对流时间尺度的全球变化，以更好地了解全球对流人口在空间和时间上的变化。
Climatological features of the cloud variability on quasi‐2‐day (Q2D) and diurnal cycle (DC) timescales are investigated by utilizing the high‐resolution satellite infrared brightness temperature (IRBT) observations from January 1998 to December 2019. A distinct land‐sea contrast between the distributions of Q2D and DC signals is evident. Diurnally driven cloud activity mainly occurs over land and mountainous regions, and the Q2D timescale is more prominent over tropical ocean basins and land where organized convection is usually observed, for example, Congo and Amazon Rainforests, the United States and subtropical South America during warm seasons. The long‐term relationship between the Q2D variability and sea surface temperature (SST) shows that the clouds are more active on Q2D timescales over higher SST environments. The Q2D variability correlates well with both the Indian Ocean Dipole (IOD) and El Niño/Southern Oscillation (ENSO) from 1998 to 2019. The cloud variability associated with a range of convective available potential energy (CAPE) values is analyzed. The result over land shows that increased Q2D cloud variability emerges with higher CAPE, suggesting the coincidence of Q2D and organized convection, particularly given that this effect is strongest over regions with frequent mesoscale convective systems (MCSs) around the world. The cloud variability and the Q2D timescale analyses provide an alternative perspective to understand the global features of mesoscale convective systems. Overall, this study objectively examines the global variability of convective timescales related to the diurnal cycle and longer‐lived convective systems to provide a greater understanding of how the global convection population varies in space and time.