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Space-time variations of equatorial Kelvin wave activity around the tropical tropopause region

热带对流层顶区域赤道开尔文波活动的时空变化

基本信息

批准号：
16540398
负责人：
SHIOTANI Masato
金额：
$ 2.24万
依托单位：
Kyoto University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2005
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16540398/
关键词：
Ozone Water vapor Tropical atmosphere Equatorial waves Stratosphere-troposphere exchange Tropopause

项目摘要

Space-time variations of the temperature and the zonal wind around the tropical tropopause region are examined using the European Centre for Medium-Range Weather Forecasts (ECMWF) Re-Analysis data set (ERA-40). The spectral analysis is performed to calculate power spectra in the zonal wavenumber and frequency domain for the zonal wind data. Two spectral peaks are found : one is in a region with frequency 0.035-0.25[1/day] and zonal wavenumber 1-10 for the Kelvin wave, and the other in a region with frequency 0.011-0.035[1/day] and zonal wavenumber 1-10 for the Intraseasonal Oscillation (ISO). On the basis of these frequency-wavenumber domains the grid data are reconstructed to represent Kelvin wave and the ISO activities, and the variances are calculated from the gridded data to see space-time variations of the Kelvin wave and the ISO. The ISO activity is clearly related to the eastward propagating convections, though the Kelvin wave activity is organized around 60゜E (the western Indian Ocean) throughout the year. We selected Kelvin wave events from the reconstructed zonal wind data with a threshold of -2.938 [m/s] to see the life cycle of the Kelvin waves. Kelvin waves with high activity around 60゜E begin mostly around 30゜W to 60゜E and disappear around 60゜E to 150゜E. By performing the composite analysis for the Kelvin wave events we found that the Kelvin wave generation is closely coupled with the convective event, though the area of the Kelvin wave generation does not correspond to the active convective area such as in the western Pacific.

利用欧洲中期天气预报中心再分析资料集（ERA-40）研究了热带对流层顶区域温度和纬向风的时空变化。对纬向风资料进行了谱分析，计算了纬向波数和频域的功率谱。发现两个谱峰：一个在Kelvin波频率0.035-0.25[1/天]、纬向波数1-10的区域;另一个在季节内振荡（ISO）频率0.011-0.035[1/天]、纬向波数1-10的区域。在这些频率-波数域的基础上，重建网格数据来表示Kelvin波和ISO活动，并从网格数据计算方差来查看Kelvin波和ISO的时空变化。ISO活动明显与东向传播的对流有关，尽管开尔文波活动全年都在60 ° E（西印度洋）附近组织。我们从重建的纬向风数据中选择Kelvin波事件，阈值为-2.938 [m/s]，以查看Kelvin波的生命周期。Kelvin波在东经60度附近活动强烈，开始主要在西经30度到东经60度之间，在东经60度到东经150度之间消失。通过对Kelvin波事件的合成分析，我们发现Kelvin波的产生与对流事件密切耦合，尽管Kelvin波产生的区域并不对应于西太平洋等对流活跃区。