副热带高压中心区域内云和降水气候特征研究回顾与展望

Review and prospect of climate characteristics of cloud and precipitation in subtropical high center

囿于副热带高压(简称副高)中心区域下沉运动不利于成云致雨的传统认识,迄今有关副高中心区域内云和降水过程的研究甚少。基于此,回顾了目前利用卫星遥感观测结果而开展的与之相关的研究成果。对这些研究的主要结论归纳如下:(1)副高中心区域内总云量可达30%以上,夏季副高中心区域以层积云为主(云量14.92%),高层云和卷层云的平均云量均不及5%,卷云的平均云量为12.13%;(2)副高中心区域内云的短波辐射强迫(82.19 W·m^(-2))加热地气,长波辐射强迫(22.28 W·m^(-2))冷却地气;(3)副高中心区域内四季均存在上升运动及降水,西太平洋副高中心区域内冬、春两季日均降水量为1.5 mm·d^(-1),夏季达2.0 mm·d^(-1),夏季北美南部至大西洋、北非的副高中心区域内日均降水量达3.0 mm·d^(-1)以上,其对局地降水的贡献率超过或接近50%;(4)副高中心区域内降水频次与上升运动频次有着准线性对应关系。

Since the subtropical highs are considered to be dominated by downward motion,the researches on the cloud and precipitation in these areas are limited so far.In order to understand the cloud and precipitation features under the subtropical high conditions,this paper reviews and prospects those related studies that are based on the satellite remote sensing observations.As exposed by previous studies,the total cloud amounts within the subtropical highs can reach over 30%.In summer,the subtropical high is dominated by stratocumulus clouds(14.92%),followed by cirrus(12.13%),and then altostratus and cirrostratus(less than 5%).Additionally,the cloud shortwave radiation forcing heats earth-atmosphere system by 82.19 W·m^(-2),while the long-wave radiation forcing cools the system by 22.28 W·m^(-2).Furthermore,there are upward motions and precipitation in the subtropical high center for all four seasons.For the western Pacific subtropical high,the daily mean rainfall reaches 1.5 mm/d during winter and spring seasons and 2 mm/d in summer.From south of the North America via Atlantic to North Africa,the daily rainfall in these subtropical highs reaches over 3 mm/d,with approaching or exceeding 50% of the contribution to local rainfall.Moreover,there is a quasi-linear relationship between the frequencies of precipitation and the upward movement in the subtropical high.These results indicate that more thorough studies of the cloud and precipitation processes in the subtropical high are needed to understand the characteristics and thermodynamic mechanisms of subtropical high.