中国南方地区层状云的形成和日变化特征分析  

THE FORMATION AND DIURNAL CHANGES OF STRATIFORM CLOUDS IN SOUTHERN CHINA

作　　者：李昀英[1] 宇如聪[1] 徐幼平[1] 张学洪[1] 

机构地区：[1]中国科学院大气物理研究所

出　　处：《测绘科技动态》2003年第6期733-743,共11页

基　　金：中国科学院创新项目 (ZKCX2 SW 2 10 );国家自然科学基金项目 (4 0 2 3 3 0 3 1和 40 0 2 3 0 0 1)

摘　　要：文中利用中国地区卫星和地面观测云的量、状、高等资料及空中规定等压面和特性层探空资料 ,分析了中国南方地区 (2 0～ 35°N ,10 3～ 12 0°E)层状中、低云的形成背景和日变化特征并初步解释了日变化的原因。层状云的伸展高度是受空中逆温层限制的 ,华南沿海地区的层积云与海洋性层积云具有较相似的性质 ,是水汽在边界层逆温下凝结、堆积的结果 ,其云量日变化与边界层日变化有密切联系 ,白天减少 ,夜间增多。高原以东地区层状中云的形成是青藏高原大地形动力作用的产物 ,是冬春季水汽在高原以东大尺度低高层辐合、中层辐散所伴随的下沉运动形成的逆温层下堆积的结果 ,其日变率较小。Stratiform clouds have thicker optical depths, which affect the local climate seriously. Southern China(20-35°N,103-120°E) is the unique region where stratiform cloud amount is very high in the mid and low latitude, but little attention has been focused on stratiform clouds in this region. Based on the monthly and hourly data from surface observations and radiosonde, the circulation condition and diurnal changes of stratiform clouds in southern China are illustrated and interpreted. The main conclusions are as follows: 1. The low stratiform clouds mainly occur along the southeast coast of Chinese mainland, where prevailing cloud type is Stratocumulus. The diurnal change of Stratocumulus is related to diurnal change of the height of boundary layer. The cloud fraction increases in the day and decreases in the night, its maximum occurs at 05 o'clock and minimum occurs at 14 o'clock. The diurnal change of Stratocumulus is also affected by the diurnal change of the difference between temperature and dew point (relative humidity). The relative humidity reaches maximum at 05 o'clock and minimum at 14 o'clock, which is coincide well with the variation of the Stratocumulus. 2. The medium stratiform clouds dominate eastern China and are the result of dynamic effect of the Tibetan Plateau. In cold seasons, the westerlies in the lower layer move around the plateau from the north and the south and converge in eastern China, especially in Sichuan, Hubei provinces and Chongqing city. These areas are also the larger relative humidity regions in China in cold seasons. The abundance vapor and large scale ascending motion provide the basic condition for the formation of stratiform clouds. How high can ascending motion reach, is affected by circulation in the air. The surface friction of the Tibetan Plateau makes the divergence in the middle of the troposphere and convergences in the lower and higher troposphere. The inversion layer occurs between 500-600 hPa because temperature decreases with lower air ascending and increases wit

关 键 词：中国 南方地区 层状云变化 日变化特征 日变率 层积云 日变化曲线 

分 类 号：P426.53[天文地球—大气科学及气象学]