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Abstract
GPS Radio Occultation (RO) is a space-based technique for sounding the Earth's atmosphere. This technique has demonstrated great potential for improving numerical weather prediction and climate monitoring. This investigation utilises FORMOSAT-3/COSMIC RO data to identify the differences between the results obtained using two different data processing packages – the Radio Occultation Processing Package (ROPP) and the COSMIC Data Analysis and Archive Center (CDAAC) software package. The introduced RO measurements for two software packages are all obtained from CDAAC dataset. This study analyses 20,210 events located in the Australian region in the year 2010. The results of this study show a negative bias between the two software packages in the bending angle at heights below approximately 5 km. The refractivity also shows a negative bias, which is consistent with previous results from the Global Navigation Satellite System Receiver for Atmospheric Sounding Satellite Application Facilities (GRAS SAF) report. A negative bias between the two processing software packages also appears for the pressure parameter at all heights and for dry temperatures from 5 to 16 km in height. The height intervals showing differences less than 1% in the bending angle, refractivity, pressure and dry temperatures are 0–25 km, 0–16 km, 0–16 km and 6–23 km, respectively. In general, the differences between the ROPP and CDAAC processing methods in the bending angle, refractivity, and pressure increase with altitude but are always less than 3%. The difference in dry temperature is also less than 3% at heights greater than 5 km, but it is larger at heights below 5 km.
GPS无线电掩星（RO）是探测地球大气圈的以空间为基础的技术。这种技术在改善数值天气预报和气候监控上已经表现出极大的潜力。本次调查采用FORMOSAT-36 COSMIC RO数据来识别使用两个不同的数据处理软件程式-无线电掩星处理方式（ROPP）和COSMIC数据分析和存档中心（CDAAC）软件程式-获得的结果之间的差异。为两个软件程式而引进的RO测量都得自CDAAC数据库。本项研究分析了2010年发现于澳大利亚地区的20210次事件。 这项研究结果显示了在高度约5公里之内以弯曲角度的两种软件程式之间的负偏值。折射率也显示负偏值，这与以前的从专为大气探测卫星应用设备（GRAS SAF）的全球导航卫星系统接收器的报告得出的结果一致。这两种处理软件程式之间的负偏值对于压力参数还出现于所有高度，在干燥温度条件下出现于为5〜16公里的高度范围。在弯曲角度、折射率、压力和干燥温度上显示差异小于1％的高度间隔分别为0-25公里、0-16公里、0-16公里和6-23公里。一般来说，对于弯曲角度、折射率和压力上ROPP和CDAAC处理方法之间的差异，随着海拔压力增加，但总是低于3％。干燥温度下的差异在高度大于5公里处也小于3％，但是高度在5公里以下之处差异却更大。
ACKNOWLEDGEMENTS
The ROPP software was obtained from the Radio Occultation Meteorology SAF (ROM SAF) Project. The UCAR CDAAC and Taiwan TACC (Taiwan Analysis Center for COSMIC) provided the FORMOSAT-3/COSMIC RO data. This research is supported by a grant from the National Science Council (NSC) of Taiwan (NSC 102-2811-M-305-001 and NSC 99-2111-M-305-001-MY3) and the Australian Space Research Program (ASRP).