Sensitivity of GNSS Occultation Profiles to Horizontal Variability in the Troposphere: A Simulation Study
Sensitivity of GNSS Occultation Profiles to Horizontal Variability in the Troposphere: A Simulation Study
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GNSS 掩星剖面对对流层水平变化的敏感性：模拟研究
DOI：
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发表时间：
2004
期刊：
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通讯作者：
G. Kirchengast
中科院分区：
文献类型：
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作者：
U. Foelsche;G. Kirchengast
研究了全球导航卫星系统（GNSS）无线电掩星观测资料反演的大气廓线对大气水平变率误差的敏感性。首先，在一个准现实的水平变化的大气中的误差相对于在球对称的大气中的误差进行了量化的基础上约300掩星事件的集合。这项调查是基于模拟数据，使用一个有代表性的欧洲中期天气预报中心（ECMWF）T511 L 60分析领域的水平变化和不。在球对称假设下，20公里以下的偏差和标准差明显小于具有水平变化的大气中的相应误差。差异在~7 km高度以下最为明显。其次，我们评估了在平均事件位置（通常做法）垂直假设“真实”剖面或沿实际3D切点轨迹沿着假设“真实”剖面的相关性。如果数据沿着切点轨迹被利用，则标准偏差和偏差误差显著减小。第三，基于三个不同入射角类别（0-10度，20-30度，40-50度;每个类别约100个事件的集合）的事件的相同集合，分析了检索产品对相对于接收天线（与低地球轨道卫星的轨道平面对准）的掩星射线入射角的敏感性。低于约7公里，大多数误差被发现增加与增加的入射角。7公里和20公里之间的干温度偏差没有表现出相关的增加与入射角，这是有利的气候监测数据的效用。
We investigated the sensitivity of atmospheric profiles retrieved from Global Navigation Satellite System (GNSS) radio occultation data to atmospheric horizontal variability errors. First, the errors in a quasi-realistic horizontally variable atmosphere relative to errors in a spherically symmetric atmosphere were quantified based on an ensemble of about 300 occultation events. This investigation was based on simulated data using a representative European Centre for Medium-Range Weather Forecasts (ECMWF) T511L60 analysis field with and without horizontal variability. Biases and standard deviations are, below 20 km, significantly smaller under a spherical symmetry assumption than corresponding errors in an atmosphere with horizontal variability. The differences are most pronounced below ~7 km height. Second, we assessed the relevance of either assuming the “true” profile vertically at a mean event location (the common practice) or along the actual 3D tangent point trajectory. Standard deviation and bias errors decrease significantly if the data are exploited along the tangent point trajectory. Third, the sensitivity of retrieval products to the angle-of-incidence of occultation rays relative to the boresight direction of the receiving antenna (aligned with the orbit plane of the Low Earth Orbit satellite) was analyzed based on the same ensemble of events for three different angle-of-incidence classes (0–10 deg, 20–30 deg, 40–50 deg; ensembles of about 100 events in each class). Below about 7 km, most errors were found to increase with increasing angle of incidence. Dry temperature biases between 7 km and 20 km exhibit no relevant increase with increasing angle of incidence, which is favorable regarding the climate monitoring utility of the data.