【作者】 万蓉；

【导师】 郑国光；

【作者基本信息】 南京信息工程大学 ， 大气物理与大气环境， 2012， 博士

【摘要】 GPS气象学为GPS探测大气水汽奠定了理论基础,地基GPS大气水汽监测网和GPS综合应用网正在为获取高空水汽资料提供了绝好的条件,当前的GPS气象学正从技术研究阶段步入业务化应用阶段。研究的目标是提出和改进基于高密度GPS资料获取高精度的水汽产品的技术,并将资料有效应用于暴雨预报和其他气象服务。研究内容包括：改进与本地化GPS水汽可降水总量反演技术、提出新的基于探空和地面观测约束的GPS三维水析层析算法、开发与建立准实时地基GPS大气水汽自动解算系统、发挥GPS大气水汽探测资料在临近预报、同化和区域气候分析中的应用。方法与结果如下：1.结合两年探空和微波辐射计资料,通过回归建模,建立了适合于长江中游地区的静力延迟模型,修订后的三种静力模型皆对PWV (Precipitable Water Vapor)反演精度有提高,GPS/PWV与探空观测的偏差减小了4-8mm。利用9个探空站数据回归建模,建立了长江中游地区的大气加权平均温度本地化模型。经双重优化后PWV与探空观测的偏差减小了6-10mrn。2.针对层析算法中方程个数少于未知量个数(即缺秩)问题,提出并实现了高斯水平约束、探空观测作为垂直约束的三维层析算法、和低层观测楔入法。基于各种观测的约束条件的层析算法不仅可以较好地给出区域水汽湿折射度的空间三维分布,并能给出区域水汽密度的三维空间分布。水汽密度平均偏差-0.63g/m3,标准偏差1.22g/m3,与探空相关系数为0.98。通过低层观测楔入法加入低层的水汽观测后,对整个区域、甚至是区域低层和区域边缘的三维水汽密度的层析精度都有改进。3.基于上述技术,研发出准实时地基GPS大气水汽自动解算系统。实现每30分钟更新一次高精度水汽解算图像产品和数据。具备定时启动、下载快速IGS星历、GPS跟踪站网数据和气象数据功能,提供产品包括湖北省境内59个单站的天顶可降水汽总量时间序列和单站的斜路径水汽分布；提供鄂东22个GPS站加密网0.5-10km高度的三维水汽分布。4.GPS资料在LAPS系统同化实验证明：新型的GPS水汽观测资料对改善降水区域和降水强度预报有正作用,同化后的湿度场中心区域和地面降水实际发生区域有很好的一致性；GPS水汽的同化改善了对流层中高层500hPa以上的温度场及湿度场,对暴雨以及以上量级的强降水预报有好的表现。5.统计2006-2008年多站点GPS水汽观测资料,发现大气可降水总量PWV变化不仅与单站雨量变化,也与面雨量变化有较好的一致性；PWV的变化对梅雨的开始有指示意义；初步得出长江中游地区不同季节产生降水和强降水的PWV阈值,其中初夏(梅雨期前期)降水的GPS/PWV阈值为35mm,强降水的GPS/PWV阈值为50mm；梅雨期降水的GPS/PWV阈值为48mm,强降水的GPS/PWV阈值为55mm；盛夏期间降水的阈值与强降水阈值接近。经检验强降水阈值0—-24小时预警临界成功指数CSI平均为22.7%,已略高于目前的暴雨预报准确率20%,该阈值对于江淮梅雨期的暴雨预报具有较好的参考价值。6.基于三峡库区GPS观测网2000-2004年资料,对比分析了库区蓄水前后区域水汽变化,特征如下：在2003年蓄水后PWV的峰值比蓄水前提高3-5mm,在2003年冬季和2004年春季(1-4月)PWV变化出现异常；日变化显示蓄水后水汽变化较以前稳定,变化起伏小。但蓄水后PWV平均比蓄水前PWV值高出6mm。数值模式模拟也反映出下垫面水体的扩大对区域的水汽增长,降水增强有促进作用。更多还原

【Abstract】 GPS meteorology theory has made it possible to detect the atmospheric water vapor by the Gorund based GPS, whose network provides the good conditions for the high-altitude atmospheric observations. GPS meteorology is stepping into the operational application stage from the research. The purpose of this paper is to provide the new methods and improve the methods to obtain the high-precision water vapor products by the high resolution GPS observations and use them effectively in the rainstorm forecasting and other meteorological services. The study is composed of the GPS PWV (Precipitable Water Vapor) retrieval technique improvement and localization, one new tomography algorithm of the GPS3D water vapor by the oberservations constraint, the quasi-real-time ground-based GPS atmospheric water vapor automatic calculation system development and the application of GPS observations in nowcasting, assimilation and regional climate analysis. The methods and results follow:1. The hydrostatic delay calculation models suiting for the PWV calculated in the middle reaches of the Yangtze River area is improved from the three traditional hydrostatic delay models with the regression algorithm based on radiosonde, microwave radiometer data in2years. The PWV bias between by GPS and radiosonde (RS) decreased4-8mm. The atmospheric weighted mean temperature in this area has been localized by9radiosonde stations data with the regression algorithm too. The PWV bias between GPS and RS decased6-10mm by using the above optimization methods.2. Gaussian horizontal restriction and sounding vertical restriction are used in the tomography algorithm as well as the observations at the ground to increase the condtions for solving the lack rank equations of3D water vapor. Not only the wet refraction but the regional water vapor density can be retrieved by the above algorithms. The density average bias of water vapor by GPS is-0.63g/m3and the standard bias1.22g/m3, and the correlation coefficient0.98in comparison to that by RS. With the the observation at the ground, the three-dimensional water vapor density accuracy has been improved in the total space, even in the lower layer and the edge area.3. Based on the above algorithms, the quasi-real-time automatic calculation system for the ground-based GPS atmospheric water vapor has been established and can output the products per30minutes. System functions contains the timing start, the downloading data including rapid IGS ephemeris, GPS network data and meteorological data, providing the products of precipitable water vapor, slant water vapor in Hubei province with59GPS stations and three-dimensional water vapor distribution in easten Hubei area with22GPS stations. 4. The tests of GPS data assimilation in LAPS system show that GPS water vapor observations improve the precipitation forecast quality of precipitation area and intensity. The humidity central area of precipitation is agreed with the actual rain area by the GPS assimilation. GPS water vapor assimilation improves the troposphere moisture and temperature field above the500hPa, and has a good performance on the heavy rain forecast.5. According to the statistics of the GPS water vapor observations in2006-2008, the characteristics of PWV varations are in approximate agreement with that of site’s rainfall but also the reginal ones. PWV threshold in the middle reaches of the Yangtze River for rain and heavy rain has been provided, such as that the precipitation PWV threshold is35mm, heavy precipitation PWV threshold50mm before the Meiyu season, precipitation threshold48mm, heavy precipitation55mm in the Meiyu season. The threshold values of precipitation are closer to the heavy precipitation thresholds in summer than in winter. Tests show that the threshold values is useful to rainfall prediction, the average critical success index of thresholds in24hours precipitation forecasting, which is22.7%, is even better than the index of comprehensive forecasting22%.6. Based on the observations in2000-2004by GPS network in the Three Gorges Reservoir, the regional water vapor changes before and after impoundment of reservoir follow:PWV peak in2003after the impoundment is more than that before impoundment with3-5mm, the PWV changes abnormally in the winter of2003and spring (January-April2004); diurnal variation shows that the water vapor changes become more stable than before. After the impoundment, PWV average is6mm more than the value before impoundment. The numerical model simulations also show that the growth of the underlying surface water bodies enhanced the regional water vapor and precipitation.更多还原