基于GPS掩星平均弯曲角的折射率反演研究

Study of Refractivity Retrievals Based on GPS Radio Occultation Mean Bending Angles

利用Abel积分变换通过掩星弯曲角计算折射率需要对高层弯曲角进行统计优化.目前由于所使用的背景场资料和具体反演方法不同,导致所发布的掩星大气数据气候统计值存在一定差异.本文使用2008年1,4,7,10月共4个月的COSMIC大气掩星附加相位数据,从纬圈平均弯曲角廓线反演相应月平均折射率,并对反演结果进行比较分析.研究表明,利用掩星折射数据进行气候研究时无需逐一对掩星探测廓线进行统计优化,在40 km以下高度基于平均弯曲角的反演方法与传统统计相比能够获得几乎一致的月平均折射率,在50 km以上高度基于平均弯曲角的反演结果更加接近ECMWF资料统计.

The retrieval step from bending angle to refractivity requires background information.Retrieval schemes in different GNSS-RO processing centers use different types of background data, which is the source of inconsistency of the generated radio occultation climatologies. In this paper, the COSMIC excess-phase data during Jan., Apr., Jul. and Oct. of 2008 was used to study the retrieving of monthly mean refractivity from monthly zonal mean bending angles. The comparison results show that： it is not necessary to apply statistical optimization to individual bending angles, since the approach based on mean bending angles and the standard method produce nearly identical mean refractivity below 40kin; and above 50km. The approach based on mean bending angles is better than the standard method when compared with mean refractivity generated from ECMWF data.