基于探空观测的多源掩星折射率质量控制及对比

Refractive Index Quality Control and Comparative Analysis of Multi-source Occultation Based on Sounding Observation

根据我国不同气候区特点对2017年9月1日-2018年8月31日的COSMIC,Metop-A和FY-3C掩星折射率进行质量控制,结果表明:3种掩星折射率的双权重平均值和标准差较接近,整体均随高度呈递减变化;4个气候区的双权重平均值和标准差有差异,亚热带季风气候区相比其他3个气候区偏大。COSMIC相对探空观测在5 km以下为负偏差,亚热带季风气候区偏差较大,FY-3C亚热带季风气候区2 km以下为正偏差,2~6 km为负偏差,6 km以上为正偏差,整体在2 N以内。利用不同气候区的质量控制标准筛选出错误数据和可疑数据,经统计确定掩星与探空折射率的相关系数阈值为0.44。1 km以下掩星自适应质量控制中错误数据占比为5%~10%,1 km以上在5%以内,3种掩星较为接近。引入探空观测参考后,Metop-A掩星在高原山地气候区的错误数据较多,其他约为6%。质量控制前,掩星折射率与探空的相关系数相对较小,质量控制后,相关系数得到提高,多在0.9以上,效果较好,掩星数据质量得到了改善。

Three occultation refractive index data of COSMIC,Metop-A and FY-3 C from 1 September 2017 to 31 August 2018 are divided into four climate zones according to climate characteristics,so that the dataset is more consistent with the normal distribution.Occultation refractive index data and the deviation from the sounding are statistically analyzed.According to statistical results,the occultation refractive index data are quality controlled.Results show that the double-weighted mean and the double-weight standard deviation of three occultations refractive index are relatively close,and the overall trends are gradually decreasing with height.There are differences between the double-weighted mean and the double-weighted standard deviation in four climate zones.The subtropical monsoon climate zone is rich in water vapor in the lower troposphere,so its double weight mean and standard deviation are larger than those in other three climate zones.In the statistical calculation of the deviation from the sounding,the COSMIC is negative below5 km,the subtropical monsoon climate zone has large deviation.The deviation of FY-3 C in subtropical monsoon climate zone is positive below 2 km,negative between 2-6 km,positive again above 6 km,and the overall deviation is within 2 N.According to different statistical characteristics of deviations in four climate zones,different quality control standards are formulated,and error data and suspicious data are screened out.The threshold value of the correlation coefficient between the occultation and the sounding refractive index determined by statistical calculation is 0.44,and suspiciousness smaller than 0.44 is taken as wrong data.Below 1 km,the proportion of error data in quality control of occultation itself is 5%-10%.Above 1 km,within 5%,three occultations are relatively close.After importing the sounding observation reference,quality control data of Metop-A occultation in the plateau mountain climate area are increasing,while the others are about 6%.Comparing the correlation coefficient between occultations and the sounding before and after quality control,the value is smaller before the quality control.After error data being eliminated,the correlation between the occultations and the sounding refractive index is improved,mostly above 0.9.The control is effective,and the quality of the occultation data is improved.