FY-2E分裂窗晴空沙尘区导风初步研究

Wind fields in dust storm clear sky region from the FY-2E split window channels

干旱半干旱沙尘爆发区风场信息作为沙尘监测的一个重要组成部分,能够为沙尘移向预报提供宝贵的资料。结合目前日趋成熟的红外分裂窗差值监测沙尘及卫星导风技术,针对FY-2E气象卫星,首先利用MODTRAN辐射传输模式对沙尘晴空区特征进行敏感性分析,再将经过图像掩膜及线性处理后的分裂窗差值图像代入导风计算程序计算,获得了传统卫星导风所无法得到的水汽含量低值区风场信息。实际个例分析表明,得到的沙尘区风场与NCEP再分析资料850hPa风场有很好的一致性,能够为监测沙尘移动提供良好的风场信息。

In this paper, the split window technique and the atmospheric motion vectors technique are combined to retrieve the wind vectors from the 11μm and 12 μm channels on the VISSR onboard the FY-2E geostationary satellite. The sensitivity analysis for at-sensor radiance under different atmosphere conditions indicate that it is possible to treat sand aerosol as tracer of difference images to achieve wind vectors in the low-level moisture fields of the dust outbreak region. On difference image, the gray value of the sand tracer is too small to be used by the Cloud-motion Wind Inferring System （CWIS）, so the linear equation is used to amplify the difference. Finally, a comparison between the wind field over dust storm outbreak area extracted from the difference images using this technique and that obtained from the NCEP reanalysis data shows a good relative accuracy. As a result, the VISSR split window could be used to retrieve wind vectors in the low-level moisture fields over relatively cloud-free areas of the dust outbreak regions.