基于跨平台红外高光谱观测的对流层三维风场测量

Tropospheric 3D Winds Measurement Based on Cross-Platform Infrared Hyperspectral Observation

精确的风场数据对提高数值天气预报准确性具有重要意义,对流层风是改进天气预报的要素之一。虽然利用气象卫星成像仪对连续云图追踪特征目标进行导风是一种有效的风场观测方法,且在区域和全球尺度上改善了数值天气预报,但仍存在风场高度分配模糊问题而产生误差。星基红外高光谱探测仪具备大气温湿度廓线垂直探测能力,通过分析各个垂直分层内的大气参数运动得到三维风场,能够提升风场垂直高度的准确性,改进风场高度分配模糊问题。提出了利用跨平台极轨气象卫星FY-3D星红外高光谱大气探测仪HIRAS和NOAA-20星跨轨红外探测仪CrIS交叉观测对流层三维风场的创新方法,根据两仪器近重叠轨道星下点交叉观测辐射数据匹配水汽通道图像,通过稠密光流法分析目标运动变化并计算风场,对风矢量进行质量控制后同ERA-Interim再分析资料作定量化比较,分析风速均值绝对偏差、均方根误差和风向均值绝对偏差。分别对2019年2月20日UTC世界时00:00,06:00,12:00的HIRAS和CrIS交叉数据计算200,300,400,600,650和1000 hPa六组垂直高度风场,结果表明,风速范围的变化趋势与再分析资料表现一致,风速范围随高度降低而减小,高层对20 m·s^(-1)以上风速更敏感,地表附近测得风速集中在10 m·s^(-1)以内。风速均值绝对偏差多数小于3 m·s^(-1),最大不超过4 m·s^(-1),风速均方根误差多数小于3.5 m·s^(-1),最大不超过4.5 m·s^(-1),风向均值绝对偏差多数小于30°,最大不超过40°。风场误差主要来自仪器自身设计参数不同引入辐射数据的观测偏差,以及因数据空间分辨率不同导致在图像重投影处理过程中引入的定位偏差。

Precise wind field data is essential for improving the accuracy of the numerical weather forecast,and tropospheric winds are not satisfied with the requirements as one of the key measurement objectives for improving weather forecasts.Although meteorological satellite-based imager derived winds by tracking the motion of characteristic targets in continuous cloud field images is an effective observation method that has improved numerical weather prediction forecasts on both regional and global scales,an error still exists in the ambiguity of the vector height assignment.Satellite-based infrared hyperspectral sounder has the capability of atmospheric vertical detection of temperature and humidity profiles,which can provide more accurate vector height assignment of wind field by analyzing atmospheric motion vectors among multiple vertical layers,improving the ambiguity of the vector height assignment.We proposed a method of tropospheric 3D winds measurement on cross-platform polar meteorological satellite-based infrared hyperspectral sounders of FY-3D/HIRAS and NOAA-20/CrIS,collocated vapor channel images through nadir overpass observations of both instruments,derived wind field by calculating the motion of dense optical flow field,combined ERA-Interim reanalysis data to verify the mean absolute deviation(MAE)and root mean square error(RMSE)of wind speed and the MAE of wind direction after quality control.The vertical wind fields of 200,300,400,600,650 and 1000 hPa are calculated through observations of HIRAS and CrIS at 00:00,06:00 and 12:00 UTC on February 20,2019,the results show that,the trend of the variation of wind speed range is consistent with ERA-Interim reanalysis data,the wind speed range decreases as the height decreases,the upper layers are more sensitive to wind speeds above 20 m·s^(-1),while wind speeds measured near the surface are concentrated within 10 m·s^(-1).The MAE of wind speed is mostly less than 3 m·s^(-1)while the maximum value is less than 4 m·s^(-1),the RMSE of wind speed is mostly less than 3.5 m·s^(-1)while the maximum value is less than 4.5 m·s^(-1),the MAE of wind direction is mostly less than 30°while the maximum value is less than 40°.The wind field error mainly comes from the observation deviation of radiation data due to different instrument parameters,along with the positioning deviation of data image re-projection due to different spatial resolution.