地基GPS准实时反演三峡地区大气可降水量的研究

探讨了利用地基GPS气象学原理反演大气可降水量（precipitable water vapor,PWV）及其变化的可行性。从理论上分析了在缺少地面气象资料时用模型估计气象元素对反演PWV的影响,分析了用IGS超快速星历代替IGS最终精密星历准实时计算PWV的可行性。利用三峡地区13个监测点连续48 h以上的跟踪数据联合国内的几个IGS站,使用GAMIT软件进行了数据处理。     

中国区域ZTD、ZWD高程缩放因子的时空特性分析

考虑到当前已有的ZTD、ZWD垂直剖面模型时空分辨率低等不足,以NASA提供的2014~2016年气象再分析资料MERRA-2为基础,分析中国区域ZTD、ZWD高程缩放因子的时空分布特性。结果表明,ZTD、ZWD高程缩放因子均具有明显的年周期和半年周期变化,与经度、纬度相关性显著,且两者时空分布特性具有明显差异。     

GPS可降水汽与MODIS可降水汽回归性分析

地基GPS可反演大气可降水汽,为气象预报提供高精度的大气水汽数据。然而GPS观测仅可以提供离散点的水汽值,MODIS却可以提供空间连续变化的水汽值,但MODIS水汽反演误差的存在使其不能满足气象预报的精度要求,因此两种遥感水汽的融合研究尤为必要。基于此,该文利用西安2006年7月-2009年7月7期GPS观测数据、地面气象实测数据和对应的MODIS数据,研究了GPS与MODIS两种遥感水汽间的回归关系,在考虑水汽的季节性变化的基础上建立了两者的回归模型,并由此建立了直接对MODIS反演水汽值的校正模型。根据多个经验模型,确定了西安GPS湿延迟与GPS可降水汽的比值:夏季取6.00、冬季取6.52。     

An investigation into the correlations among GNSS observations and their impact on height and zenith wet delay estimation for medium and long baselines

Most stochastic modelling techniques neglect the correlations among the raw un-differenced observations when forming the variance–covariance matrix of the Global Navigation Satellite System (GNSS) observations. Some methods were developed to model these correlations. One such method is the Minimum Norm Quadratic Unbiased Estimator (MINQUE). Studies have shown that MINQUE improves ambiguity resolution, and ultimately, the positioning solution in short baselines. However, its effect in cases of processing with longer baselines and on the estimation of zenith wet delay (ZWD) is somewhat unknown. In this paper, a comparison between the impact of neglecting the correlations among the observations using an elevation-angle-dependent model (EADM) and modelling the correlations using MINQUE on height determination and ZWD for medium and long baselines is carried out. The initial testing was carried out across two Australian GNSS stations with a medium-length baseline throughout a three-week campaign. The results showed that using MINQUE did not resolve the coordinate, height and wet delay components as accurately as the EADM. The results were further verified with two long-baseline campaigns whereby EADM was also able to provide better wet delay estimates. The coordinate results were, however, mixed. Overall, the study concluded that the inclusion of the correlations among the observations, in general, do not improve the resolution of the coordinate and wet delay estimates.     

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从GPS推算大气水汽的误差分析

讨论了从GPS观测数据推算大气水汽值的各种误差，分析了这些误差对大气水汽值的影响。     

利用GPS观测反演三峡地区对流层湿延迟的分布及变化

利用三峡地区 8个监测点连续三天的监测数据 ,联合 3个IGS站在此期间的观测 ,反演了各监测点对流层上空的天顶总延迟ZTD ,利用外推的地表气压资料由模型分离出其中的静力学延迟ZHD ,得到天顶湿延迟ZWD含量 ,并对湿延迟变化趋势线进行了分析。通过对该区域短时间内每间隔两小时湿延迟分布图的分析 ,探讨了利用地基GPS气象原理在短时间内观测大气水汽分布及其变化的可行性     

在高海拔地区Saastamoinen与Hopfield模型推算水汽含量差异的研究

详细分析了在高海拔地区利用Saastamoinen和Hopfield两种模型推算水汽含量时产生差异的原因，并通过对高程不同的测站上实测数据的分析和研究，给出了Hopfield模型的修正项。