热带风暴“Bilis”(0604)暴雨增幅前后的水汽输送轨迹路径模拟

采用水平分辨率1°×1°的NCEP 再分析资料、1°×1°的NCEP GDAS资料和2.5°×2.5°的NOAA大气环流资料, 结合NOAA HYSPLIT v4.8轨迹模式对0604号热带风暴“Bilis”整个生命史的水汽输送特征进行模拟分析, 并分析了“Bilis”暴雨增幅前和增幅后的水汽输送轨迹及不同来源的水汽贡献。结果表明, “Bilis”整个活动过程中主要有四支水汽输送通道, 分别是源自索马里、孟加拉湾、120°E 越赤道气流和东太平洋的水汽, 其中源自索马里和孟加拉湾的西南水汽输送(偏南水汽通道)占主导地位, 120°E 越赤道气流和东太平洋的水汽是西南水汽随着“Bilis”环流逆时针旋转, 自环流中心东北侧进入雨区(东北水汽通道), 是低压环流与偏南风相互作用的结果。其中, 偏南通道水汽大部分输送到850 hPa以下的低层, 自环流北侧输入的水汽则主要输送到暴雨区上空850 hPa以上。对比暴雨增幅前后各通道的水汽贡献率发现, 孟加拉湾西南气流输送的低纬水汽对此次暴雨增幅的形成、发展起重要作用。

Simulation of Water Vapor Transport Paths before and after Increased Rainstorms from Tropical Storm Bilis (0604)

Using the HYSPLIT v4.8 model and the NOAA atmospheric circulation (2.5°×2.5°) and NCEP GDAS (1.0°×1.0°) data, the authors investigated variations in water vapor transportation features and the contribution of water vapor to their major pathways from Tropical Storm Bilis (0604).The authors classified the data into two phases:pre-rainstorm and post-rainstorm.The results indicate that the entire Bilis life cycle has four major water channels:Somalia, the Bay of Bengal, a cross-equatorial flow at 120°E, and the eastern Pacific water vapor.The data was then further classified into two reversed categories:the first is the southward water vapor transported from Somalia and the Bay of Bengal, which plays a key role in moisture transportation; the second is the cross-equatorial airflow at 120°E and the flow from the eastern Pacific, which results from the interaction between the cyclone and the southwest monsoon and enters a rain belt northeast of the circulation center.The southern water vapor channel from the Somali jet and the Bay of Bengal is related to the southwest monsoon and transports moisture up to levels of 850 hPa.The South China Sea and the western Pacific transports moisture to levels greater than 850 hPa.Comparing the water vapor contribution rate of each channel before and after increased rainstorms, it is observed that the low latitude water vapor, formed due to increased rainstorms in the Bay of Bengal, plays a significant role in the formation and development of the increased moisture during torrential rain.