The Role of Precipitation in Controlling the Transition from Stratocumulus to Cumulus Clouds in a Northern Hemisphere Cold-Air Outbreak
The Role of Precipitation in Controlling the Transition from Stratocumulus to Cumulus Clouds in a Northern Hemisphere Cold-Air Outbreak
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DOI：
10.1175/jas-d-16-0362.1
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发表时间：
2017-04
影响因子：
3.1
通讯作者：
S. Abel;I. Boutle;K. Waite;S. Fox;P. Brown;R. Cotton;G. Lloyd;Tom Choularton;K. Bower
中科院分区：
文献类型：
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作者：
S. Abel;I. Boutle;K. Waite;S. Fox;P. Brown;R. Cotton;G. Lloyd;Tom Choularton;K. Bower
摘要利用英国北部一次冷空气爆发的飞机观测，研究了阴天混合相层积云层中的边界层和云特性，以及过渡到更多破裂的开放蜂窝对流的过程。层积云主要由含有少量冰粒的液滴组成，在顺风向浅的积云中，有一种转变为更冰化的条件。云形态的快速变化伴随着降水的增加，次级冰过程变得活跃，云下层的热力梯度更大。测量还显示，边界层积聚模式气溶胶通过过渡过程中的降水过程被移除，这与在亚热带地区观察到的开放气团口袋中的过程类似。使用允许对流(网格间距1.5公里)的气象局统一模式的区域版本进行的模拟能够再现许多显著的特征.
AbstractAircraft observations in a cold-air outbreak to the north of the United Kingdom are used to examine the boundary layer and cloud properties in an overcast mixed-phase stratocumulus cloud layer and across the transition to more broken open-cellular convection. The stratocumulus cloud is primarily composed of liquid drops with small concentrations of ice particles and there is a switch to more glaciated conditions in the shallow cumulus clouds downwind. The rapid change in cloud morphology is accompanied by enhanced precipitation with secondary ice processes becoming active and greater thermodynamic gradients in the subcloud layer. The measurements also show a removal of boundary layer accumulation mode aerosols via precipitation processes across the transition that are similar to those observed in the subtropics in pockets of open cells. Simulations using a convection-permitting (1.5-km grid spacing) regional version of the Met Office Unified Model were able to reproduce many of the salient feature...