Atmospheric Convection
Atmospheric Convection
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DOI：
10.1080/07055900.2022.2082915
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发表时间：
2022-08-08
期刊：
影响因子：
1.2
通讯作者：
Han, Jongil
中科院分区：
文献类型：
--
作者：
Lin, Jialin;Qian, Taotao;Han, Jongil
对流参数化是全球气候模拟的长期瓶颈，也是大气科学中最困难的问题之一。对流参数化的不确定性是IPCC全球变暖预测中普遍存在的气候敏感性的主要原因。本文回顾了大气对流的观测和参数化，着重讨论了云结构、体积效应和闭合假设。介绍了ECMWF对流方案、NCEP模式和WRF模式中的Grell方案、NCAR和DOE模式中的Zhang-MacFarlane方案以及浅层湿对流的参数化方案。观测到的对流具有自抑制机制，对流上升气流的卷吸，不饱和对流下降气流产生的地面冷池，和温暖和干燥的对流层低层由中尺度下降气流。对流后的环境通常以“钻石探测”为特征，表明过度稳定而不是勉强回到中性状态。对流前环境的特点是地面水汽辐合等机制触发对流层低层缓慢增湿。过稳定和缓慢增湿使对流事件具有幕式特征，对流层中高层与边界层解耦，使得状态型准平衡假设失效。目前，大多数对流方案中缺少不饱和对流下降气流，特别是中尺度下降气流，而一些方案使用未稀释的对流上升气流，所有这些方案都有利于与双ITCZ（热带辐合区），过于弱的MJO（Madden-Julian Oscillation）和早熟的日降水最大值相关的对流。我们提出了一个新的战略对流方案的发展使用再分析驱动的模式实验，如同化运行在天气预报中心和气候模拟中心的年代际预测运行，辅助卫星模拟器评估的关键特征，如对流云顶分布和层状降水分数的生命周期。
Convective parameterization is the long-lasting bottleneck of global climate modelling and one of the most difficult problems in atmospheric sciences. Uncertainty in convective parameterization is the leading cause of the widespread climate sensitivity in IPCC global warming projections. This paper reviews the observations and parameterizations of atmospheric convection with emphasis on the cloud structure, bulk effects, and closure assumption. The representative state-of-the-art convection schemes are presented, including the ECMWF convection scheme, the Grell scheme used in NCEP model and WRF model, the Zhang-MacFarlane scheme used in NCAR and DOE models, and parameterizations of shallow moist convection. The observed convection has self-suppression mechanisms caused by entrainment in convective updrafts, surface cold pool generated by unsaturated convective downdrafts, and warm and dry lower troposphere created by mesoscale downdrafts. The post-convection environment is often characterized by "diamond sounding" suggesting an over-stabilization rather than barely returning to neutral state. Then the pre-convection environment is characterized by slow moistening of lower troposphere triggered by surface moisture convergence and other mechanisms. The over-stabilization and slow moistening make the convection events episodic and decouple the middle/upper troposphere from the boundary layer, making the state-type quasi-equilibrium hypothesis invalid. Right now, unsaturated convective downdrafts and especially mesoscale downdrafts are missing in most convection schemes, while some schemes are using undiluted convective updrafts, all of which favour easily turned-on convection linked to double-ITCZ (inter-tropical convergence zone), overly weak MJO (Madden-Julian Oscillation) and precocious diurnal precipitation maximum. We propose a new strategy for convection scheme development using reanalysis-driven model experiments such as the assimilation runs in weather prediction centres and the decadal prediction runs in climate modelling centres, aided by satellite simulators evaluating key characteristics such as the lifecycle of convective cloud-top distribution and stratiform precipitation fraction.