一种新的高精度全球对流层天顶延迟模型

对流层延迟是影响高精度卫星导航定位的关键因素，也是大气科学研究的重要数据.针对已有全球对流层延迟模型的模型方程未同时顾及高程、纬度和季节变化以及模型构建时仅使用单一格网点数据等问题，本文提出了一种对流层天顶延迟（ZTD）全球模型构建的新方法，即引入滑动窗口算法将全球剖分为大小一致的规则窗口，利用2008—2015年全球大地观测系统（GGOS）大气格网产品构建每个窗口同时顾及高程、纬度和季节因子的全球ZTD新模型（GGZTD模型）.联合未参与建模的2016年全球GGOS格网产品和2016年全球316个IGS站精密ZTD产品，检验了GGZTD模型的精度和适用性.结果表明：以GGOS大气格网ZTD产品和IGS站ZTD产品为参考值，GGZTD模型在全球的精度分别为3.58 cm和3.62 cm，相对于UNB3m模型和目前标称精度最优的GPT2w模型计算的ZTD信息，GGZTD模型在全球表现出了最优的精度和稳定性，其精度相对于UNB3m模型具有显著的提升（精度提高了30%以上），相对于GPT2w模型仍具有一定的改善；在ZTD计算时GGZTD模型相对于GPT2w模型显著地减少了模型参数，尤其相对于GPT2w-1（减少了99%）.GGZTD模型只需输入位置与时间和依赖相对较少的模型参数则能在全球获得高精度和稳定的ZTD信息，极大地提升了模型的计算效率.

A new high-precision global model for calculating zenith tropospheric delay

Radio signals transmitted from the satellite will be affected by atmospheric refraction when it passes through the atmosphere,which commonly known as tropospheric delay in data processing of Global Navigation Satellite System.Tropospheric delay is one of the dominant errors in high-precision satellite navigation and positioning as well as the fundamental data in atmospheric science.The empirical tropospheric model is a commonly used approach for calculating tropospheric delay.Due to the drawbacks of the current global tropospheric delay models are still existed,such as the model equations do not take altitude,latitude and seasonal variations into account simultaneously,as well as only single gridded data is used for modeling.To address those of shortages,a new approach,the sliding window algorithm,is proposed to develop a global zenith tropospheric delay(ZTD)model.Then,the sliding window algorithm is used to divide the global into regular windows with the same size.For each window over globe,the ZTD model that considering altitude,latitude and seasonal variations simultaneously is developed using GGOS Atmosphere gridded products.Finally,a new high-precision global ZTD model is developed,named as GGZTD model.Both GGOS Atmosphere gridded ZTD products that were not involved in modeling in 2016 and precise ZTD products from 316 globally distributed IGS sites in 2016 are treated as reference values to assess the performance of GGZTD model.The results are:(1)GGZTD model has the best performance relative to GPT2w and UNB3m models,which shows precision of 3.58 cm and 3.62 cm against GGOS Atmosphere gridded ZTD products and IGS ZTD data over globe,respectively.In terms of RMS error,GGZTD model has significantly improved by 30%against UNB3m model,which still shows improvement against GPT2w model.(2)The model parameters of GGZTD model have been significantly reduced against GPT2w model in terms of ZTD estimation,especially compared to GPT2w-1(with reduction of 99 percent).GGZTD model,fed only by the day of year and the station coordinates as well as relatively few model parameters are needed,could provide a high-precision and stable ZTD value on a global scale,and the calculation efficiency of the model could be greatly improved.