Quality assessment of COSMIC/FORMOSAT-3 GPS radio occultation data derived from single- and double-difference atmospheric excess phase processing
Quality assessment of COSMIC/FORMOSAT-3 GPS radio occultation data derived from single- and double-difference atmospheric excess phase processing
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DOI：
10.1007/s10291-009-0132-5
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发表时间：
2010
期刊：
影响因子：
4.9
通讯作者：
W. Schreiner;C. Rocken;S. Sokolovskiy;D. Hunt
中科院分区：
文献类型：
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作者：
W. Schreiner;C. Rocken;S. Sokolovskiy;D. Hunt
本研究评估GPS无线电掩星（RO）大气多余相位数据的质量与单，双差处理算法。1秒GPS时钟估计的频谱分析表明，1秒的采样间隔是必要的，以充分消除GPS时钟误差与单差处理。一周（2009年5月2日至8日）的COSMIC/FORMOSAT-3数据进行了分析后处理模式与四种不同的处理策略：（1）用1秒GPS地面数据进行双差，（2）用30秒GPS时钟估计进行单差（标准COSMIC数据分析和存档中心产品），（3）5s GPS时钟单差，（4）1 s GPS时钟单差。对5,596个RO剖面的分析表明，用1 s GPS时钟进行单差处理得到的中性大气弯曲角和反射活动是最高质量的。在60到80公里高度之间，中性大气弯曲角的随机噪声在单差情况下约为1.50 e −6 rad，在双差情况下约为1.74 e −6 rad。对同位探测的分析还表明，弯曲角来自单差与1秒的GPS时钟比其他处理策略更一致。此外，RO和高分辨率的欧洲中期天气预报中心（ECMWF）在30公里的高度上的活动轮廓之间的差异的标准偏差是0.60%的单差与1和5秒的GPS时钟，0.68%的单差与30秒的时钟，和0.66%的双差。单差和零差处理需要1秒或更短的GPS时钟采样间隔，以获得RO应用的最高质量过量大气相位数据。
This study evaluates the quality of GPS radio occultation (RO) atmospheric excess phase data derived with single- and double-difference processing algorithms. A spectral analysis of 1 s GPS clock estimates indicates that a sampling interval of 1 s is necessary to adequately remove the GPS clock error with single-difference processing. One week (May 2–8, 2009) of COSMIC/FORMOSAT-3 data are analyzed in a post-processed mode with four different processing strategies: (1) double-differencing with 1 s GPS ground data, (2) single-differencing with 30 s GPS clock estimates (standard COSMIC Data Analysis and Archival Center product), (3) single-differencing with 5 s GPS clocks, and (4) single-differencing with 1 s GPS clocks. Analyses of a common set of 5,596 RO profiles show that the neutral atmospheric bending angles and refractivities derived from single-difference processing with 1 s GPS clocks are the highest quality. The random noise of neutral atmospheric bending angles between 60 and 80 km heights is about 1.50e−6 rad for the single-difference cases and 1.74e−6 rad for double-differencing. An analysis of pairs of collocated soundings also shows that bending angles derived from single-differencing with 1 s GPS clocks are more consistent than with the other processing strategies. Additionally, the standard deviation of the differences between RO and high-resolution European Center for Medium range Weather Forecasting (ECMWF) refractivity profiles at 30 km height is 0.60% for single-differencing with 1 and 5 s GPS clocks, 0.68% for single-differencing with 30 s clocks, and 0.66% for double-differencing. A GPS clock-sampling interval of 1 s or less is required for single- and zero-difference processing to achieve the highest quality excess atmospheric phase data for RO applications.