GPS掩星气压的评估及质量控制

Assessment and quality control of GPS occultation pressure

摘要:

以探空数据为参考，将2014年1月1日—12月31日的COSMIC掩星气压作为GPS掩星试验样本，将中国区域划分为4个气候区，从双权重平均值、双权重标准差及相关系数角度对GPS掩星气压进行评估，并根据其统计结果进行质量控制。结果显示：双权重平均值和双权重标准差相较传统方法统计出的平均值和标准差更不易受异常数据的影响，评估结果更加准确。4个气候区之间气压的双权重平均值差异较小；双权重标准差在亚热带季风气候区的数值较小（小于6 hPa）、在温带季风气候区较大（最大可达15 hPa）。以探空数据为参考，气压偏差的统计表明，亚热带季风气候区从低层到高层都为正偏差（0.8 hPa左右），其他三个气候区在6 km以下多为负偏差、6 km以上为正偏差（0.5 hPa左右）。根据相关系数的统计，将相关系数确定为0.80，并根据各气候区不同的统计结果划分阈值区间；质量控制结果显示，错误点大多分布在GPS掩星气压与探空气压相差较大的区域，两步质量控制的错误数据百分比大部分在5％以内；对比质量控制前后GPS掩星气压与探空气压之间的相关系数表明，质量控制后两者的相关性得到明显改善。

Abstract:

Using the sounding data as a reference, taking the COSMIC occultation pressure from 1 January to 31 December 2014 as a GPS test sample, China was divided into four climate zones.The GPS occultation pressure was evaluated from the perspectives of double weight average, double weight standard deviation and correlation coefficient, and the quality control was carried out according to the statistical results.Results show that compared with the traditional method, the double weight average and the double weight standard deviation are less susceptible to abnormal data, and the evaluation resultsare more accurate.The differences of double weight average values of atmospheric pressure among the four climate zones are small.The doubleweight standard deviation is smaller in the subtropical monsoon climate zone (less than 6 hPa) and larger in the temperate monsoon climate zone (up to 15 hPa).With the sounding data as a reference, the statistics of atmospheric pressure deviation show that there is a positive deviation from the lower troposphereto the upper troposphere in the subtropical monsoon climate zone(about 0.8 hPa), and there are mostly negative deviation below 6 km and a positive deviation above 6 km in the other three climate zones (about 0.5 hPa).According to the statistics of correlation coefficient, the correlation coefficient is determined to be 0.80.According to the different statistical results in each climate zone, the threshold interval is divided.Quality control results show that the error points are mostly distributed in the areas where there is a big difference between GPS occultation pressure and sounding pressure.The percentage of error data produced by the two-step quality control is mostly less than 5%.Comparing the correlation coefficients between GPS occultation pressure and sounding pressure before and after quality control, it shows that the correlation between them is significantly improved after quality control.