Variability in the Characteristics of Precipitation Systems in the Tropical Pacific. Part I: Spatial Structure
Variability in the Characteristics of Precipitation Systems in the Tropical Pacific. Part I: Spatial Structure
复制标题
DOI：
10.1175/jcli-3304.1
复制
发表时间：
2005-03
影响因子：
4.9
通讯作者：
H. Masunaga;T. L’Ecuyer;C. Kummerow
中科院分区：
文献类型：
--
作者：
H. Masunaga;T. L’Ecuyer;C. Kummerow
利用热带降雨测量使命（TRMM）卫星上的降水雷达（PR）和可见光和红外扫描仪（VIRS）研究了热带降水云垂直和水平特征的区域和时间变化。本研究的重点是三个大洋区（西，中，东太平洋）连同两个大陆区的比较和两个单独的时间段（1998年2月和2000年2月）在不同阶段的厄尔尼诺-南方涛动（ENSO），以检查区域和ENSO相关的变化。利用雷达回波顶高和红外亮温研究了风暴的高度谱。谱的变化明显地与大尺度环流及其ENSO相关的变化相关。根据高度谱，将暴雨系统分为浅层、密集积云、深层层状和深层对流四类。深层状和深对流类别，这两个都有非常冷的云顶，区分雷达回波顶的高度，使深对流系统伴随着大量的大冻结粒子高空。虽然浅层事件在相对寒冷的海洋上发生的概率中占主导地位，但深对流系统在温暖的海面温度（SST）中占据了一席之地。除2000年西太平洋深对流系统占主导地位外，其余各海区和各年份的海温转换均发生在28°-29 ° C的海温阈值。引入雨相关尺度长度（RCSL）和云相关尺度长度（CCSL）作为风暴水平尺度的统计指标。虽然RCSL是8-18公里的浅和积云密集型云没有显着的区域和时间变化，RCSL和CCSL与深层状和深对流系统始终超过100公里，并表现出系统的变化。特别是中太平洋和东太平洋的RCSL和CCSL在厄尔尼诺年显著增加。
Regional and temporal variability in the vertical and horizontal characteristics of tropical precipitating clouds are investigated using the Precipitation Radar (PR) and the Visible and Infrared Scanner (VIRS) on board the Tropical Rainfall Measuring Mission (TRMM) satellite. The present study focuses on the three oceanic regions (west, central, and east Pacific) together with two continental regions for comparison and the two separate time periods (February 1998 and February 2000) under different phases of the El Nino– Southern Oscillation (ENSO) in order to examine regional and ENSO-related variations. The height spectrums of storms are investigated in terms of radar echo-top height and infrared brightness temperature. The variability in the spectrum clearly correlates with the large-scale circulation and its ENSO-related change. On the basis of the height spectrum, storm systems are classified into the four categories of shallow, cumulus congestus, deep stratiform, and deep convective. The deep stratiform and deep convective categories, both of which have very cold cloud tops, are differentiated by radar echo-top heights so that deep convective systems are accompanied with an appreciable amount of large frozen particles aloft. While shallow events are dominant in the probability of occurrence over relatively cold oceans, deep convective systems take their place for warmer sea surface temperatures (SSTs). The turnover occurs at the SST threshold of 28°–29°C for all the oceanic regions and years investigated except the west Pacific in 2000, for which deep convective systems prevail over the entire range of SST. Rain correlation-scale length (RCSL) and cloud correlation-scale length (CCSL) are introduced as statistical indicators of the horizontal scale of storms. While the RCSL is 8–18 km for shallow- and cumulus congestus–type clouds without significant regional and temporal variations, the RCSL and CCSL associated with deep stratiform and deep convective systems consistently exceed 100 km and exhibit a systematic variability. The RCSL and CCSL in the central and east Pacific, particularly, increase significantly in the El Nino year.