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Study of Space and Time Distribution of Precipitation in Tropics by Doppler Radars

多普勒雷达研究热带降水时空分布

基本信息

批准号：
11440141
负责人：
SATOMURA Takehiko
金额：
$ 7.23万
依托单位：
KYOTO UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2001
项目状态：
已结题

项目摘要

Using Chiang Mai Radar of TMD and Om Koi Radar of BRRAA in Thailand, radar echo intensity in monsoon rainy seasons in 1998-2000 was analyzed. It was shown that the total echo area observed by both radars had a significant diurnal variation: it rapidly increased before noon, reached its maximum at 15-16 LT and slowly decreased through the night In May-July, almost all echoes moved from south or southwest as the lower tropospheric wind. In the early October, the both direction of echo movement and wind reversed. By dividing radar observation area of Om Koi into 11 stripes parallel to the main mountain range, the diurnal variation in the each stripe was investigated. The results showed that in May-July the diurnal variation in stripes in the lee-side of mountains had clear trends towards later maxima leeward (eastward) from the mountainous region. In the early October, the diurnal variation in stripes in the leeside (western side) of the mountains showed the same leeward phase shifts.Using a numerical cloud-resolving model, it was concluded that eastward movement of squall lines governed the diurnal variation of precipitation over the Indo-China Peninsula. Above results by radar data analysis proved this conclusion by he numerical.By using a regional climate model, effects of deforestation in northeastern part of Thailand were evaluated. It was shown that monthly averaged precipitation decreased in September over the deforested area, because the monsoon wind and thus the horizontal vapor transport were week in September.Using rain gages and IR data of GMS, the diurnal variation of precipitation over Bangladesh and whole Indo-China Peninsula was studied in detail. It was shown by the analysis that not only the difference of the diurnal variation of precipitation between the land and the sea but the difference between plain areas and mountainous areas were clearly indicated.

利用泰国TMD公司的清迈雷达和BRRAA公司的Om Koi雷达，对1998-2000年季风雨季的雷达回波强度进行了分析。结果表明，两台雷达观测到的回波总面积都有明显的日变化，中午前迅速增大，在15-16 LT时达到最大值，夜间逐渐减小。10月上旬，回波运动和风的方向都发生了逆转。将锦鲤雷达观测区划分为11条平行于主山脉的条带，研究了各条带的日变化规律。结果表明，5 - 7月，山区背风面条纹日变化有明显的向东（背风面）最大值晚的趋势。在10月上旬，山脉背风面（西侧）的条纹日变化也表现出同样的背风位相变化，利用数值云分辨模式分析，结果表明，印度支那半岛降水的日变化受飑线东移的控制。上述雷达资料分析结果从数值上证实了这一结论，并利用区域气候模式对泰国东北部森林砍伐的影响进行了评估。结果表明，由于9月季风减弱，水汽水平输送减弱，森林砍伐区9月平均降水量减少。利用GMS卫星的红外和雨量计资料，详细研究了孟加拉国和整个中南半岛半岛降水的日变化。分析表明，降水日变化不仅在陆地和海洋之间有明显的差异，而且在平原和山区之间也有明显的差异。