天顶静力延迟模型对GPS可降水量反演的影响分析及改进

利用地基GPS遥感大气可降水量(PWV,precipitable water vapor)过程中,天顶静力延迟(ZHD,zenith hydrostatic delay)模型精度直接影响PWV反演精度。文中将常用天顶静力延迟模型(Black模型、Hopfield模型和Saastamoinen模型)计算所得ZHD与基于湖南省2016-04-01—2017-03-31高空气象探测秒级数据计算所得探空ZHD进行对比,发现模型存在较明显系统偏差,其中Black模型ZHD平均偏低40mm以上。利用探空实测ZHD对天顶静力延迟模型进行回归建模,订正模型系数后可明显减小模型系统偏差和均方误差。改进后的ZHD模型可明显减小GPSPWV反演的系统偏差,并略微降低均方误差,其中采用改进后SA模型反演所得GPSPWV与探空PWV相比,平均偏低不超过0.230 7mm,反演准确性有较显著改善。     

Estimation and evaluation of real-time precipitable water vapor from GLONASS and GPS

The revitalized Russian GLONASS system provides new potential for real-time retrieval of zenith tropospheric delays (ZTD) and precipitable water vapor (PWV) in order to support time-critical meteorological applications such as nowcasting or severe weather event monitoring. In this study, we develop a method of real-time ZTD/PWV retrieval based on GLONASS and/or GPS observations. The performance of ZTD and PWV derived from GLONASS data using real-time precise point positioning (PPP) technique is carefully investigated and evaluated. The potential of combining GLONASS and GPS data for ZTD/PWV retrieving is assessed as well. The GLONASS and GPS observations of about half a year for 80 globally distributed stations from the IGS (International GNSS Service) network are processed. The results show that the real-time GLONASS ZTD series agree quite well with the GPS ZTD series in general: the RMS of ZTD differences is about 8 mm (about 1.2 mm in PWV). Furthermore, for an inter-technique validation, the real-time ZTD estimated from GLONASS-only, GPS-only, and the GPS/GLONASS combined solutions are compared with those derived from very long baseline interferometry (VLBI) at colocated GNSS/VLBI stations. The comparison shows that GLONASS can contribute to real-time meteorological applications, with almost the same accuracy as GPS. More accurate and reliable water vapor values, about 1.5–2.3 mm in PWV, can be achieved when GLONASS observations are combined with the GPS ones in the real-time PPP data processing. The comparison with radiosonde data further confirms the performance of GLONASS-derived real-time PWV and the benefit of adding GLONASS to stand-alone GPS processing.     

GPS反演的可降水量与降水的对比分析研究

本文以秦皇岛为例,分析GPS可降水量与降水实况的关系。2007年5月~8月期间发生16次降水过程,每次水汽的增加,都对应着一次降水过程和降水峰值的出现;16次降水事件中,GPS可降水量序列峰值超前降水发生时间1h和2h分别各为6次,两者占到总降水次数的75%,也就是说GPS可降水量序列峰值超前降水发生时间约为1~2h;降水出现的时间一般发生在大气可降水量迅速增加之后,在2h或3h的大气可降水量的增幅迅速增加达到5mm后,2h内出现降水占68.75%,3~4h出现降水占18.75%,5~6 h出现降水占6.25%;而大气可降水量迅速增加前2h内出现降水的仅占6.25%,即GPS可降水量迅速增加后4h内出现降水的比率占到87.5%。GPS可降水量可作为降水短期预报的指标之一。     

利用GPS可降水量校正MODIS近红外水汽数据

针对MODIS近红外水汽产品精度不足以及地基GPS技术解算的大气可降水量地理分布不连续的问题,提出一种利用地基GPS可降水量来校正MODIS水汽产品从而得到区域性连续分布的高精度可降水量的方法。利用GAMIT软件和地基GPS数据解算出IGS站点的大气水含量,建立GPS可降水量与MODIS近红外水汽产品的回归分析模型得到最终的校正结果。通过与实测气象站数据对比分析可知,所提方法有效地结合了MODIS和地基GPS两种遥感水汽技术的优点,能够得到高精度、地理分布连续的大气可降水量,研究结果可为实时天气预报、气候监测等工作提供参考。     

GPS天顶对流层延迟与可降水量的相关性

针对水汽含量在短时间内变化快、影响因素多,目前精确测定其含量仍是一个难点的现状,该文采用GAMIT软件,利用两次暴雨发生过程中香港地区6个连续运行参考站系统参考站数据,计算天顶对流层总延迟(ZTD)和大气可降水量(PWV),并与实际降雨量进行对比。研究结果表明,暴雨发生前后的1~2h或者更长时间内,天顶对流层延迟、大气可降水量和实际降水量一直保持着较好的对应关系,天顶对流层延迟和大气可降水量会出现骤增和骤降现象,而且天顶对流层延迟和可降水量的变化速度越快,说明大气环境越不稳定,降水概率也就越高。     

利用地基GPS资料分析成都地区大气可降水量

利用成都地区GPS地震监测网的观测资料,通过Bernese软件求解获得CHDU、JYAN、PIXI、QLAI、RENS、ZHJI测站的天顶总延迟和湿延迟,运用湿延迟与大气可降水量之间的转换关系得到各测站大气可降水量,与站点地面实际降雨量及SONDE大气可降水量进行了比较分析。结果表明：地基GPS监测大气可降水量变化与地面实际降雨量有很强的相关性,与SONDE大气可降水量的平均差值为0．43mm,均方偏差为2．56mm。多站点GPS监测大气可降水量联合分析,对于研究区域大气可降水量的变化有一定的意义。     

Experiment on driving precipitable water vapor from ground-based GPS network in Chengdu Plain

The estimates of total zenith delay are derived using Bernese GPS Software V4. 2 based on GPS data every 30 s from the first measurement experiment of a ground-based GPS network in Chengdu Plain of Southwest China during the period from July to September 2004. Then the estimates of 0.5 hourly precipitable water vapor (PWV) derived from global positioning system (GPS) are obtained using meteorological data from automatic weather stations (AWS). The comparison of PWV derived from GPS and those from radiosonde observations is given for the Chengdu station, with RMS (root mean square) differences of 3.09m. The consistency of precipitable water vapor derived from GPS to those from radiosonde is good. It is concluded that Bevis’ empirical formula for estimating the weighted atmospheric mean temperature can be applicable in Chengdu area because the relationship of GPS PWV with Bevis’ formula and GPS PWV with radiosonde method shows a high correlation. The result of this GPS measurement experiment is helpful both for accumulating the study of precipitable water vapor derived from GPS in Chengdu areas located at the eastern side of the Tibetan Plateau and for studying spatial-temporal variations of regional atmospheric water vapor through many disciplines cooperatively.     

Experiment on Driving Precipitable Water Vapor from Ground-Based GPS Network in Chengdu Plain

The estimates of total zenith delay are derived using Bernese GPS Software V4. 2 based on GPS data every 30 s from the first measurement experiment of a ground-based GPS network in Chengdu Plain of Southwest China during the period from July to September 2004. Then the estimates of 0.5 hourly precipitable water vapor (PWV) derived from global positioning system (GPS) are obtained using meteorological data from automatic weather stations (AWS). The comparison of PWV derived from GPS and those from radiosonde observations is given for the Chengdu station, with RMS (root mean square) differences of 3.09m. The consis- tency of precipitable water vapor derived from GPS to those from radiosonde is good. It is concluded that Bevis’ empirical formula for estimating the weighted atmospheric mean temperature can be applicable in Chengdu area because the relationship of GPS PWV with Bevis’ formula and GPS PWV with radiosonde method shows a high correlation. The result of this GPS measurement experiment is helpful both for accumu- lating the study of precipitable water vapor derived from GPS in Chengdu areas located at the eastern side of the Tibetan Plateau and for studying spatial-temporal variations of regional atmospheric water vapor through many disciplines cooperatively.     

Retrieval of the Change of Precipitable Water Vapor by GPS Technique

The feasibility of GPS precipitable water vapor (PWV) is discussed based on the comparison of Radiosonde and GPS PWV where the correlation coefficient is 0.94 and the RMS is 4.0 mm. PWV change in the C...     

First comparisons of precipitable water vapor estimation using GPS and water vapor radiometers at the Royal Observatory of Belgium

We compare precipitable water vapor (PWV) time series measured by water vapor radiometers (WVRs) to PWV time series estimated using global positioning system (GPS) observations in a regional network of stations in western Europe. Inside this network, we focus on the baseline Brussels – Wettzell which presents the advantage to have the collocation of a GPS receiver and a WVR at both endpoints. The comparison between our GPS and WVR estimations of precipitable water vapor shows an agreement at the millimeter level. In addition, we show that the zenith total delay (ZTD) estimations computed with our GPS processing strategy agrees with the GPS estimations of ZTD done by the CODE analysis center at the millimeter level. Electronic Publication     

GPS反演大气综合水汽含量的影响因素分析

目前地基GPS遥感大气综合水汽含量的可行性已经被众多实验所验证,为进一步改善地基GPS遥感大气综合水汽含量的精度,本文对2004年6月哈尔滨GPS跟踪站的观测数据进行了解算,并结合探空资料计算的水汽结果对各项误差进行了分析。结果表明:广播星历不能用于高精度GPS水汽遥感;5cm的测站坐标误差将引起3mm的水汽误差,截止高度角的不同以及通用模型均会对水汽结果造成不同程度的影响。     

基于GPS的MODIS近红外可降水量季节性模型建立

在考虑可降水量季节性变化的基础上,提出利用GPS数据建立MODIS近红外可降水量季节性模型。首先对比分析2014年北京房山(BJFS)站的GPS可降水量和相应时间的MODIS近红外可降水量数据,发现两者之间的变化趋势基本一致,存在显著线性相关性;然后以GPS可降水量为标准值,利用回归分析建立GPS和MODIS可降水量之间的季节和全年校正模型。经检验,GPS可降水量与四个季节模型校正的MODIS近红外可降水量的均方根误差均小于3mm,最大误差不超过6mm,季节校正模型的精度都要高于全年校正模型。     

GPT／2模型用于 GPS 大气可降水汽反演的精度分析

气象参数(温度T、气压P)是GPS大气可降水汽(PWV)反演中必不可少的数据,也是PWV反演的重要误差源之一。文中主要对GPT/2(GPT、GPT2)模型用于PWV反演的精度进行验证和分析。基于非差精密单点定位(PPP)技术,选取SuomiNet网9个测站的观测数据,借助研制的PPP软件,分别采用GPT模型、改进的GPT2模型以及测站实测气象数据进行大气可降水汽(PWV)反演。以实测气象数据处理结果为参考,对两种模型解算的PWV进行了对比和精度分析。结果表明:改进的GPT2模型优于GPT模型,尤其是当测站的高程较大时,GPT2模型的稳定性更优、适用性更广;采用GPT2模型解算的PWV偏差均值小于±1.0mm,精度(RMS)优于±1.5mm。在缺少实测气象数据的情况下,利用GPT2模型数据仍然能够取得较为理想的PWV反演结果。     

无气象要素的GPS对流层延迟推算可降水量的研究

本文针对武汉地区GPS气象网资料,进行了GPS对流层延迟直接推算可降水量的研究。在武汉东湖站GPS对流层延迟与无线电探空可降水量的比较中,两者具有很好的相关性,相关系数达到了0.93;推导了对流层延迟直接推算可降水量的模型,对模型结果进行了检验,在武汉东湖站的对流层延迟转换的可降水量与无线电探空可降水量的比较中,均方根为7.8mm,相关性为0.91,这说明了在没有气象数据的地区对流层延迟直接推算的可降水量可以作为气象短期预报的参考。     

利用珠海CORS监测大气可降水量

依托珠海城市连续运行参考站（continuously operating reference stations,CORS）系统,采用地基全球导航卫星系统（global navigation satellite system,GNSS）反演大气可降水量（precipitable water vapor,PWV）,展开大气可降水量监测系统的应用研究。系统采用精密单点定位（Precise Point Positioning,PPP）技术与IGS(International GNSS Service)轨道、钟差产品实时或事后估计CORS站点上的大气可降水量,可实时更新发布水汽监测数据。通过对监测系统的内符合精度与外符合精度的测试,表明本大气可降水量监测系统对PWV的估计精度优于2 mm,能实现对珠海北斗CORS(ZHBDCORS)网中站点间小区域的水汽监测,区分各站之间的水汽变化,能满足实时对流层水汽监测及其他气象应用需求,有效地拓展ZHBDCORS系统的服务领域。     

利用GPS/BDS/GLONASS/Galileo组合PPP反演大气可降水量

为进一步改善精密单点定位（PPP）探测大气可降水量（PWV）的性能,本文提出采用GPS/BDS/GLONASS/Galileo组合PPP进行PWV反演的方法,并利用国内3个MGEX（multi-GNSS experiment）观测站的实测数据,对GPS/BDS/GLONASS/Galileo组合PPP在大气水汽探测方面的性能进行了评估。试验结果表明：相较于GPS PPP、GPS/BDS组合PPP和GPS/GLONASS组合PPP,GPS/BDS/GLONASS/Galileo组合PPP估计天顶对流层延迟（ZTD）的初始化时间分别缩短了33%、26%、20%,且能获得更高精度的ZTD估值和PWV信息,在大气水汽探测方面的性能更优。     

应用数值模型提高GPS可降水量反演精度的研究

利用建立在长江三角洲地区GPS观测网的资料,以上海宝山探空观测为例,进行了应用数值模式提高GPS可降水量反演精度的试验。研究结果表明:大气平均温度的估计误差直接影响大气可降水量的反演精度,用MM5中尺度数值预报模式预报估计的大气平均温度可减小大气平均温度的估计误差,从而提高大气可降水量的反演精度。     

利用北斗CORS反演大气可降水量的精度分析

为探究BDS反演大气可降水量(PWV)的精度,该文采用辽宁省连续运行参考站的BDS/GPS观测数据,选择辽宁省中部地区4个代表站,通过GAMIT软件进行单系统解算,并以ECMWF再分析资料为参考的真值进行了分析比对.研究表明,BDS解算的PWV平均误差、均方根误差在4 mm以内,比GPS反演结果精度稍低;而PWV因其与实际降水有较好的相关性,可作为短期临近天气预报的参考:当PWV开始累积超过6h时,降水的可能性较大,大规模的降雨一般伴随着迅速的水汽聚集与释放.     

GPS遥感大气综合水汽含量局部区域模型与通用模型结果的比较分析

为进一步提高利用GPS遥感大气综合水汽含量的精度,部分学者提出了利用当地探空气象资料建立局部区域模型,以改善采用通用模型计算综合水汽含量结果的观点。为此本文就局部区域模型和通用模型反演的水汽结果进行了比较分析,得出了一些重要的结论。