【作者】 范士杰；

【导师】 刘焱雄； 许才军；

【作者基本信息】 武汉大学 ， 大地测量学与测量工程， 2013， 博士

【摘要】 海洋是水、汽交换的主要场所,大气中86%的水汽来源于海洋。连续、实时、高精度地获取海洋水汽信息,对准确地掌握天气系统的演化非常重要。我国东临太平洋,太平洋暖湿气流为我国的东部地区带来了大量的水汽及降水,也造成了沿海地区海洋灾害的频繁发生。因此,加强海洋水汽信息的监测方法和应用研究,是有效应对全球气候变化的重要手段,也是海洋防灾减灾的关键措施。GPS气象学(GPS Meteorology,简称GPS/MET)研究为海洋水汽信息反演提供了新的途径。近20年来,地基GPS气象学快速发展和深入应用,国内外出现了大量的地基GPS气象的研究成果和应用系统,针对陆地稳固GPS站的GPS可降水汽(precipitable water vapor, GPS/PWV)反演方法基本成熟和完善,也为海上动态环境的GPS水汽监测提供了基础和借鉴。海上缺乏密集、稳固的GPS安装平台,只能以海洋浮标或航行船舶为载体。国外多位学者分别利用船载或浮标GPS数据,对近海乃至开阔海域上空GPS/PWV信息的反演方法进行了一些探索性研究,取得了令人鼓舞的结果,从而将地基GPS气象学的研究与应用由陆地推向海洋。GPS海洋水汽遥感一直缺乏系统性研究,海上动态GPS斜路径水汽(slant-path water vapor, GPS/SWV)信息提取及海洋上空三维水汽层析是GPS海洋水汽信息反演的重点和难点,国内外尚无相关专题研究。因此,海上动态GPS水汽信息反演研究已成为地基GPS气象学研究的薄弱环节。本文以渤海为研究区域,对GPS海洋水汽信息反演和三维水汽层析展开研究,形成了一套基于动态GPS的海洋水汽信息反演技术和方法,研制了相关数据处理软件,验证了本文提出的所有方法及其结果。利用本文的研究成果,借助海面浮体上的GPS设备,可以实现海洋水汽信息的连续和高精度监测,以弥补星载或机载微波遥感、海上探空气球等方式的不足,为海气交换研究提供基础性数据,也为灾害性海洋天气的预报和预警服务。本文主要研究内容和相关结论如下：(1)精密单点定位(precise point positioning, PPP)软件研制和精度分析基于序贯最小二乘估计方法,利用IGS等提供的精密卫星星历和钟差产品,作者与香港理工大学等联合研制了精密单点定位软件UNIP。相对于高精度事后差分处理软件GrafNavTM解算得到的双差固定解,在航行状态下,UNIP软件得到的海上船载动态PPP解在X,Y,Z三个方向的RMS均在±2cm以内。因此,基于PPP技术和UNIP软件可以实现海上移动平台的厘米级动态精密定位,为海上高精度动态GPS水汽探测提供了良好的平台。(2)海上动态GPS大气可降水汽(PWV)估计系统、深入地研究了海上动态GPS/PWV信息提取方法,导出了其函数模型和随机模型。结合海洋动态观测环境和海上水汽信息的时空变化,引入随机游走过程估计方法,动态模拟船载GPS接收机天顶对流层湿延迟(zenith wet delay, ZWD)在时间和空间尺度上的随机变化,在滤波处理时附加ZWD参数的动态噪声约束；并对不同噪声约束及卫星截止高度角对海上动态GPS/PWV信息提取精度的影响进行了讨论和分析。基于UNIP软件平台,开发了’GPS/PWV信息提取模块。利用渤海船载动态GPS测量和同步气象观测数据,进行了海上动态GPS/PWV信息提取和精度验证。结果表明：海上船载动态GPS/PWVMM5模式积分水汽基本一致;以后者为参考值,GPS/PWV的偏差在3mm以内,RMS优于1.2mm,这一结果明显好于国外现有研究结果。(3)海上动态GPS斜路径水汽含量(SWV)估计在海上动态GPS/PWV信息提取的基础上,本文进一步对海上动态GPS/SWV信息提取进行了深入研究。在现有计算方法的基础上,对海上动态GPS/SWV的提取算法进行改进,提出了顾及星间单差残差的GPS/SWV提取方法。利用渤海船载动态GPS测量和同步气象观测数据,提取了海上动态GPS/SWV信息,并对改进算法进行了数据验证和精度分析。结果表明：海上动态GPS/SWV的估算精度可以达到mm量级,与地基GPS/SWV的估算精度相当。相对于MM5模式积分水汽结果,采用本文提出的SWV提取方法,海上动态GPS/SWV的偏差在±3.5mm以内,其RMS为1.2mm,相比传统的“非差残差法”,精度提高1mm左右,改善效果较为明显。(4) GPS三维水汽层析的算法研究和软件研制本文对附加约束条件的水汽层析算法进行了系统和深入的研究。以附加约束条件的水汽层析方法为基础,采用序贯逐次滤波的数据处理手段,引入随机游走过程估计方法,在分时段逐次滤波处理中兼顾水汽层析参数随时间变化的特性；同时,针对海洋水汽资料相对匮乏的客观实际,提出和设计了无先验信息约束的水汽层析处理模式,使其史加适用于海洋三维水汽场的构建。基于上述算法,作者研制了GPS三维水汽层析软件3DTom,分别利用香港CORS参考站网数据和无线电探空数据、渤海船载动态GPS观测数据和MM5模式数据进行了算法验证和精度分析。结果表明：①附加低精度先验信息约束的处理方案的水汽层析结果相对较差,在水汽分布的主要高度层(1-4km)上均出现了较大的偏差；而附加高精度先验信息约束的处理方案的水汽层析结果在三种方案中相对最优,与探空结果最为接近。该结果进一步验证了先验信息的精度对GPS水汽层析的不同影响,高精度的先验信息可进一步改善GPS水汽层析结果。②无先验信息约束的处理方案的水汽层析结果同样优于低精度先验信息约束方案,与高精度先验信息约束方案的解算结果基本一致。在先验信息精度较低或缺少先验信息的情况下,本文提出的无先验信息约束的GPS水汽层析处理模式同样取得了较为理想的结果,具有更大的应用价值。(5)渤海三维水汽场的构建方法研究以渤海为研究区域,本文对渤海上空GPS三维水汽场的构建思路和方法进行了深入地探讨。利用沿岸地基GPS固定站和海上船载或浮标动态GPS移动观测平台,实现对渤海上空水汽的连续监测。以沿岸地基GPS观测为基础,利用船载动态GPS观测进行加密,组建“动态GPS气象监测网”,同时结合HY-2扫描微波辐射计获取的柱状水汽产品,提出了陆、海、空联合探测渤海上空水汽空问分布的研究思路和设计方案。首次对渤海上空GPS水汽信息反演和三维水汽层析进行了系统研究。以渤海局域上空(东经120.75。-122.0。,北纬37.5。～38.25。)为试验区域,利用沿岸地基GPS观测和海上船载动态GPS测量数据,借助研制的UNIP和3DTom软件,构建了渤海局域上空大气湿折射率的空间分布。以MM5模式数据为参考值,对GPS三维水汽层析结果进行了精度分析。结果表明：GPS三维水汽层析结果与MM5估算结果基本一致,各分层网格单元的均方根差(RMS)均优于10mm/km,所有层析网格单元(voxel)大气湿折射率的RMS优于5mm/km,在渤海局域上空稀疏水汽资料条件下,取得了较为理想的结果。以环黄渤海沿岸地基GPS/PWV为参考值,首次对HY-2扫描微波辐射计获取的柱状水汽产品进行了验证和精度分析。HY-2柱状水汽产品与地基GPS/PWV结果具有良好的一致性,可作为GPS海洋三维水汽层析的一种新的数据源。更多还原

【Abstract】 Ocean is the main place of water-vapor exchange, and86%of water vapor in the atmosphere comes from the ocean. Continuous, real-time and high-precision acquisition of oceanic water vapor is very important to accurately grasp the evolution of weather systems. China is an oceanic disaster-prone country. The Pacific has brought a lot of water vapor and precipitation for our country’s eastern region, also contributed to the frequent marine disasters for the coastal areas. Strengthening the monitoring of oceanic water vapor information is an important means of effective response to global climate change, also a key to the marine disaster prevention and mitigation measures.GPS meteorology provides a new ways for oceanic water vapor retrieval. Over the past20years, ground-based GPS meteorology obtained the rapid development and further application. GPS water vapor inversion method has been basically mature and perfect. All of these provide the basis and reference for marine GPS water vapor monitoring. Lacking of dense and solid GPS observation platforms at sea, there is only a buoy or ship as a carrier where the GPS receivers are set up. In the past decade, foreign professionals carried out exploratory research on GPS/PWV information retrieval using GPS data from ship or buoy which is offshore or over the open sea, and achieved some encouraging results. Thus the research and application of ground-based GPS meteorology has trended towards sea. Marine GPS water vapor remote sensing has been a lack of systematic research. GPS slant-path water vapor (SWV) information extraction and three-dimensional water vapor tomography is the research emphasis and difficulties on marine GPS water vapor retrieval. There are no relevant research results on the field at home and abroad. Therefore, oceanic GPS water vapor retrieval has become the weaknesses in GPS meteorology.GPS marine water vapor retrieval and three-dimensional water vapor tomography is researched in this thesis. A set of GPS marine water vapor retrieval technology and method is gained, and relevant data processing software is developed. Based on the research results of this thesis, continuous and high precision monitoring of oceanic water vapor information is achieved by means of GPS devices on the sea floats. It can compensate for satellite or airborne microwave remote sensing and sea sounding balloon, and provide a basis data for air-sea exchange research, forecasting and warning services for disaster ocean weather. Main contents and conclusions are as follows:(1) Precise point positioning (PPP) software development and its precision analysisBased on sequential least squares estimation method, the author develops precise point positioning software named as UNIP in cooperation with Hong Kong Polytechnic University, taking advantage of IGS precise satellite ephemeris and clock products. In the dynamic mode, relative to the high-precision double difference fixed solutions from GrafNavTM software, RMS of sailing ship-borne PPP solutions in X, Y, Z coordinates are within±2cm. Therefore, precise point positioning (PPP) technology based on dynamic mobile platform at sea can achieve centimeter-level positioning precision, and provide a good platform for high-precision oceanic GPS water vapor remote sensing.(2) Oceanic dynamic GPS precipitable water vapor (PWV) in the atmosphere estimateThis paper carries out in-depth research on oceanic dynamic GPS/PWV information extraction method, and gives out its function model and random model. Combining marine dynamic observation environment and temporal and spatial variation of oceanic water vapor information, random walk process is introduced as dynamic noise constraint of ZWD parameter, which simulates random changes of ship-borne GPS zenith wet delayed (ZWD). Then the influences of PWV retrieval precision for different random process noise constraint and cut-off elevation angle are analyzed.Based on UNIP software, the GPS/PWV information extraction module is developed. With Bohai ship-borne dynamic GPS measurements and synchronous meteorological observations, oceanic GPS/PWV information is extracted and accuracy validation of that is carried out relative to MM5model integral water vapor. Results show that oceanic ship-borne GPS/PWV is basically the same as MM5model. Using MM5mode as reference, the deviation of GPS/PWV is in3mm, and RMS is less than1.2mm.(3) Oceanic dynamic GPS slant-path water vapor (SWV) estimatesThe marine dynamic GPS/SWV retrieval is further researched on the basis of oceanic GPS/PWV extraction. This article has improved the existing oceanic GPS/SWV extraction algorithm, and proposed a new oceanic GPS/SWV extraction method of taking into account single-difference residual between satellites. With ship-borne dynamic GPS measurements and synchronous meteorological observations in the Bohai Sea, the oceanic GPS/SWV information is extracted and validation of improved algorithms and accuracy analysis of GPS/SWV are carried out. Results showed that the precision of oceanic dynamic GPS/SWV can achieve in millimeter range, and is basically the same as that of ground-based GPS/SWV estimation. With the proposed oceanic GPS/SWV extraction method, the deviation of GPS/SWV is in3.5millimeter relative to the MM5model integral water vapor, and accordingly its RMS is1.2millimeter. Compared with traditional "non-difference residual method", the accuracy of GPS/SWV extraction can improve about1millimeter.(4) Algorithm research and software development of three-dimensional GPS water vapor tomographyThis paper has carried out a systematic research on GPS water vapor tomography algorithm with constraint condition. Using sequential least squares estimation and successive filtering processing with time interval, random walk process estimation method is introuduced to take into account the characteristics of water vapor change over time. In view of the lack of marine water vapor, this paper puts forward and designs the solution without prior information, which is more suitable for the construction of marine three dimensional water vapor field.Based on the above algorithms, the author developed a three-dimensional GPS water vapor tomography software named as3DTom. Algorithm validation and accuracy analysis of3DTom software is carried out using Hong Kong CORS network and radiosonde data, Bohai ship-borne dynamic GPS observation and MM5data. Results showed that:①the water vapor tomography result of the2nd solution with low-precision priori information constraints is relatively poor, and appears the larger deviations in the main levels of water vapor distribution (1～4km). However the1st solution with high-precision priori information constraints is relatively optimal in three solutions, with the closest the sounding results. The results further validate the differential impact of the precision of priori information on GPS water vapor tomography. High-precision priori information can further improve the precision of GPS water vapor tomography results.②the result of3rd solution without priori information constraints is basically the same as1st solution with high-precision priori information constraints, and superior to2nd solution with low-precision priori information constraints. In the absence of priori information such as radiosonde and numerical weather model data, the designed solution without priori information by author can also get a more ideal result, and has more application value.(5) Research on the method of constructing three dimensional water vapor fields in Bohai SeaFor the study area in the Bohai Sea, this paper explores the ideas and methods on the construction of three-dimensional GPS water vapor fields over the sea. The coastal ground-based GPS stations and oceanic dynamic ship-borne or buoy observation platforms were used to realize the continuous monitoring of water vapor over the Bohai Sea. On the basis of ground-based GPS stations along the coast, the dynamic GPS meteorological monitoring networks were formed with marine dynamic ship-borne GPS observations and HY-2column water vapor products from scanning microwave radiometer. This paper proposed a research idea on joint land, marine and air exploration of water vapor spatial distribution over the Bohai Sea. Then the technique route and schematic design are provided.The local region (120.75°E～122.0°E,37.5°N～38.25°N) in the Bohai Sea was used for test area. With the help of developed UNIP and3DTom software, GPS three dimensional water vapor tomography test was first carried out by using marine ship-borne GPS observations and coastal ground-based GPS stations. The space distribution of atmospheric wet refraction over the study area is obtained. Using MM5mode as reference, the precision analysis of GPS three dimensional water vapor tomography results has been carried out. Results indicate that GPS three dimensional water vapor tomography results are basic consistent with MM5estimates, and RMS of atmospheric wet refraction in each layer is superior lOmm/km, then RMS of atmospheric wet refraction in all layers is less than5mm/km. In the sparse water vapor conditions over the local region in the Bohai Sea, this paper achieved more ideal results.Using coastal ground-based GPS/PWV as reference, the precision analysis of HY-2column water vapor products from scanning microwave radiometer has been carried out for the first time in domestic. HY-2column water vapor products have good consistency with ground-based GPS/PWV, and can be used as a new source for GPS marine three dimensional water vapor tomography.更多还原