当前位置: X-MOL 学术Atmos. Res. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
A shift in the diurnal timing and intensity of deep convection over the Congo Basin during the past 40 years
Atmospheric Research ( IF 5.5 ) Pub Date : 2021-09-25 , DOI: 10.1016/j.atmosres.2021.105869
Kathrin Alber 1 , Liming Zhou 1 , Ajay Raghavendra 1, 2
Affiliation  

The Congo Basin, one of the three most convective regions in the world, has recently experienced a large-scale drying trend accompanied by an increase in thunderstorm activity. This study analyzes changes in the diurnal variations of cloudiness and deep convection from 1979 to 2019 over the Congo, evaluates their associations with trends in precipitation efficiency, and explores their possible connections to the observed decrease in precipitation. Analyses of GridSat-B1 and MODIS satellite datasets in conjunction with ERA5 reanalysis data show that cloud cover has decreased, and brightness temperature (Tb) has increased during the morning hours, while convective activity has increased and Tb has decreased during the afternoon hours, possibly due to the observed warming and drying trend over the Congo. The combined effects of decreasing clouds during the morning and the subsequent increasing convection during the afternoon have led to an amplification of the diurnal amplitude in Tb over the Congo. Our results also indicate a decrease in precipitation efficiency and an increase in cloud base height. Such changes may be attributable to the Congo drought as increased surface temperatures and decreased surface relative humidity would raise the lifted condensation level, and thus increase the cloud base height and decrease the precipitation efficiency. This positive-feedback mechanism may ultimately result in the observed decrease of precipitation at the surface, further accelerating the drying trend over the Congo.



中文翻译:

过去 40 年刚果盆地深对流的昼夜时间和强度的变化

刚果盆地是世界上对流最强的三个地区之一,最近经历了大规模的干燥趋势,伴随着雷暴活动的增加。本研究分析了 1979 年至 2019 年刚果多云和深对流日变化的变化,评估了它们与降水效率趋势的关联,并探讨了它们与观测到的降水减少之间的可能联系。GridSat-B1 和 MODIS 卫星数据集结合 ERA5 再分析数据的分析表明,云量减少,亮度温度(T b)在早晨增加,而对流活动增加,T b下午时间减少,可能是由于观察到刚果上空的变暖和干燥趋势。上午云层减少和随后下午对流增加的综合影响导致 T b的昼夜振幅放大在刚果。我们的结果还表明降水效率降低和云底高度增加。这种变化可能归因于刚果干旱,因为地表温度升高和地表相对湿度降低会提高抬升的凝结水平,从而增加云底高度并降低降水效率。这种正反馈机制可能最终导致观测到的地表降水减少,进一步加速刚果上空的干燥趋势。

更新日期:2021-10-01
down
wechat
bug