太平洋上空“射线状”云的观测分析  

Observation Analysis of“Actinoform Clouds”over the Pacific Ocean

作　　者：王忠石 傅刚 孙维康[1] Wang Zhongshi;Fu Gang;Sun Weikang(Department of Marine Meteorology,College of Oceanic and Atmospheric Sciences,Ocean University of China,Qingdao 266100,China;The Key Laboratory of Physical Oceanography,Ministry of Education,Ocean University of China,Qingdao 266100,China)

机构地区：[1]中国海洋大学海洋与大气学院海洋气象学系,山东青岛266100 [2]中国海洋大学物理海洋教育部重点实验室,山东青岛266100

出　　处：《中国海洋大学学报（自然科学版）》2024年第5期10-22,共13页Periodical of Ocean University of China

基　　金：国家重点研究发展计划项目(2022YFC3004200);国家自然科学基金项目(42275001)资助。

摘　　要：本文研究太平洋上“射线状”云——一种尚未纳入现行云分类体系的云的基本特征及分布规律。利用中分辨率成像光谱仪(MODIS)可见光卫星云图、NOAA-20和Suomi NPP可见光和红外卫星云图,对2017—2021年发生在太平洋上空257个“射线状”云个例进行了统计分析。结果表明,“射线状”云呈近似圆形或椭圆形,有明显的云系中心和清晰的带状径向云臂由中心向四周延伸,多数个例发生在中低纬度的东南太平洋和东北太平洋上空,全年除4月份外各月份均有“射线状”云发生,高频月份为6、7和8月,中频月份为5、9、10和11月,低频月份为1、2、3、4和12月。部分“射线状”云个例的云系有旋转态势,北半球呈逆时针旋转,南半球呈顺时针旋转。“射线状”云云顶之上有逆温层存在,“射线状”云内部的运动特征为:云系低层以水平运动为主,低层辐合;云系中层以上升运动为主,水平方向辐合辐散较弱;云系顶层受稳定逆温层的阻碍无法继续向上发展,垂直气压速度(p-速度)近乎消失,转化为水平方向上的强辐散。本文的研究结果可为进一步研究“射线状”云形成的物理机制打下基础。This paper aims to investigate the fundamental features and geographical distribution of actinoform clouds over the Pacific Oceans,which have not been included in the current cloud classification system.Total of 257 actinoform clouds over the Pacific Ocean from 2017 to 2021 were statistically analyzed by using satellite visible cloud imagery provided by MODIS sensors carried on Aqua and Terra,and satellite visible and infrared cloud imagery from NOAA-20 and Suomi NPP.The results show that the shapes of actinoform clouds are approximately circular or elliptical,with obvious centers of cloud systems and clear“banded radial cloud arm”extending from the center to outside.Most of actinoform clouds occur over the mid-and low-latitude regions of the Southeastern Pacific and the Northeastern Pacific.In the whole year,actinoform clouds occur in all months except for April.Their high occurrence frequency months are June,July and August,middle occurrence frequency months are May,September,October and November,and low occurrence frequency months are January,March,April and December.Some actinoform clouds have rotation patterns,with counterclockwise rotation over Northern Hemisphere and clockwise rotation over Southern Hemisphere.There usually exists inversion layer in the top of actinoform clouds.Their motion characteristics are summarized as follows:in the lower-level the atmosphere mainly moves horizontally,and the lower atmosphere is convergent.In the mid-level,the upward motions are dominant,and the horizontal convergence and divergence are weak.In the top of cloud system the atmospheric motions are blocked by stable inversion layer,so that the vertical velocities are almost zero.

关 键 词：“射线状”云 带状云臂 太平洋 统计分析 大气逆温层 

分 类 号：P426.52[天文地球—大气科学及气象学]