Rainfall characteristics and variations in the tropics

在目前的研究中，作者旨在利用降雨和卫星获得的云数据揭示热带地区在不同时间尺度上的降雨特征和变化。我们获得了来自马来西亚和越南的每小时降雨量数据，来自印度尼西亚、尼泊尔、马来西亚、孟加拉国、越南和中国的日降雨量数据，以及来自美国CDIAC和NCAR的月降雨量数据。因此，利用马来西亚和日本的10年平均每小时降雨量数据揭示了沿海和内陆地区以及热带和中纬度地区之间的区域差异。马来西亚的日变化与风场的关系也得到了揭示。在日尺度上，对记录的最大日降水量的全球分布进行了分析，结果表明，包括日本在内的热带和亚热带北太平洋西部地区是世界上降雨量最大的地区。在季节尺度上，我们分析了OLR和5天平均降雨量数据，发现热带北太平洋西部地区虽然位于海洋区域，但使用12年平均数据显示其表现为季风气候。从海气相互作用的角度揭示了季风气候的形成机制。此外，还分析了日本白鹤、蜀林等地的季节内气候变化，并指出了季节内气候变化与季节变化的关系。在长期时间尺度上，泰国的降雨变化与东太平洋的海温有关，热带非洲和印度的降雨变化与印度洋的海温密切相关。最后将整个热带地区的降水变化与盆地尺度海表温度的变化进行了比较，证实了这两个参数在区域和季节变化上的密切联系。总体上强调了海温变化对热带降水的强烈影响。物理过程有待进一步研究。

In the present study, the authors aimed to reveal rainfall characteristics and variations in the tropics in various time-scales using both rainfall and satellite deerived cloud data. We obrained hourly rainfall data from Malaysia and Vietnam, daily data from Indonesia, Nepal, Malaysia, Bangladesh, Vietnam, China, and monthly data from CDIAC and NCAR in USA.As a result, regional differences between coastal and inland area, and between tropics and mid-latitudes are revealed using 10-year mean hourly rainfall data in Malaysia and Japan. The relationship between diurnal variations in rainfall and wind field is also revealed in Malaysia. On a daily-scale, global distribution of recorded maximum daily precipitation is analyzed and the tropical and sub-tropical western North Pacific region including Japan in shown to bein the heaviest rainfall region of the world. On a seasonal-scale, we analyzed OLR and 5-day mean rainfall data and revealed that the tropical western North Pacific region exhibits a monsoonal climate using 12-year mean data, though it is located in a oceanic area. Also revealed is the mechanism of such monsoonal climate from a view point of air-sea interactions. Furthermore, climatological intraseasonal variations are analyzed and relationship between these variations and seasonal changes of Japan, such as Baiu and Shurin is pointed out. On a long-term time-scale, rainfall variations in Thailand are shown to be related to the SST over the eastern Pacific, those of tropical Africa and india are closely related to the SST in the lndian Ocean. Finally the rainfall variations in a entire tropics are compared with those in the basin-scale SST and close connection in regional and seasonal variations between these two parameters are confirmed. As a whole, strong influence of SST variations on tropical rainfall are emphasized. Further study is needed on the physical processes.