［ 2017年03月02日 ］
RIKEN International Symposium on Data Assimilation 2017
"The Impact of the Radiosonde Observations of Cold Surge over the Philippine Sea in December 2012"
An East Asian northerly cold surge greatly affects convective activity in the tropics. In this study, the impact of the radiosonde observations of cold surge over the Philippine Sea during the R/V Hakuho Maru cruise KH-12-6 in December 2012 has been investigated by performing observing system experiments (OSE) using the local ensemble transform Kalman filter (LETKF) and the atmospheric general circiulation model for the Earth Simulator (AFES).
After the assimilation, the modified surface winds of the cold surge were generally stronger than those before the assimilation. For the developing tropical cyclones in the northern and southern hemispheres, their cyclonic rotations are mostly intensified. The impact of the additional radiosonde observations in the cold surge propagated immediately up to the updraft area near the equator and the downdraft areas in the mid-latitudes through the local Hadley circulation. After the spreading impact in the lower troposphere, large impacts were deepened around the typhoons and tropical depressions.
The propagating process of the additional observation impact over the Philippine Sea suggested that the cold surge could affect a large-scale circulation, including the tropical cyclones and depressions in the tropics and the mid-latitudes.