GNSS troposphere tomography based on two-step reconstructions using GPS observations and COSMIC profiles

Xia, Pengfei; Cai, Changqun; Liu, Zhizhao

doi:10.5194/angeo-31-1805-2013

Cited by 49 publications

(58 citation statements)

References 33 publications

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“…Traditionally, there are two ways to divide the grid. One is uniform division (Flores et al, 2000;Xia et al, 2013) and the other is non-uniform division (Perler et al, 2011;Rohm, 2012Rohm, , 2013Jiang et al, 2014). Considering the actual distribution characteristics of water vapor density that is sparse in high layers and dense in low layers, we use nonuniform division in this study.…”

Section: Tomography Grid Divisionmentioning

confidence: 99%

Optimization of GPS water vapor tomography technique with radiosonde and COSMIC historical data

Xia

Cai

2016

Ann. Geophys.

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Abstract. The near-real-time high spatial resolution of atmospheric water vapor distribution is vital in numerical weather prediction. GPS tomography technique has been proved effectively for three-dimensional water vapor reconstruction. In this study, the tomography processing is optimized in a few aspects by the aid of radiosonde and COSMIC historical data. Firstly, regional tropospheric zenith hydrostatic delay (ZHD) models are improved and thus the zenith wet delay (ZWD) can be obtained at a higher accuracy. Secondly, the regional conversion factor of converting the ZWD to the precipitable water vapor (PWV) is refined. Next, we develop a new method for dividing the tomography grid with an uneven voxel height and a varied water vapor layer top. Finally, we propose a Gaussian exponential vertical interpolation method which can better reflect the vertical variation characteristic of water vapor. GPS datasets collected in Hong Kong in February 2014 are employed to evaluate the optimized tomographic method by contrast with the conventional method. The radiosonde-derived and COSMICderived water vapor densities are utilized as references to evaluate the tomographic results. Using radiosonde products as references, the test results obtained from our optimized method indicate that the water vapor density accuracy is improved by 15 and 12 % compared to those derived from the conventional method below the height of 3.75 km and above the height of 3.75 km, respectively. Using the COSMIC products as references, the results indicate that the water vapor density accuracy is improved by 15 and 19 % below 3.75 km and above 3.75 km, respectively.

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Section: Tomography Grid Divisionmentioning

confidence: 99%

Optimization of GPS water vapor tomography technique with radiosonde and COSMIC historical data

Xia

Cai

2016

Ann. Geophys.

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“…(7) provides an initial state to the MART algorithm to converge, which will produce a more accurate wet refractivity filed. The advantages of this combined reconstruction algorithm have been demonstrated in several studies (Notarpietro et al, 2011;Wen et al, 2008;Xia et al, 2013). In this study, tomographic model is discretized using the method developed in Chen and Liu (2014).…”

Section: Water Vapor Tomography With Multi-source Datamentioning

confidence: 99%

“…Comparisons of water vapor profiles between tomography and numerical weather models showed that the root mean square error (RMSE) can reach an order of better than 10 mm km −1 . Xia et al (2013) presented a study for water vapor tomography using GPS observations and radio occultation profiles. An overall accuracy of 6.3 mm km −1 of tomographic results is achieved for a 10-day test.…”

Section: Introductionmentioning

confidence: 99%

“…This problem can be resolved by adding inter-voxel constraints and especially by introducing non-GNSS measurements (Bender and Raabe, 2007;Bevis et al, 1992). Several studies have shown that GNSS tropospheric tomography has improved after assimilating other observations, such as by radiosondes (Bi et al, 2006;Skone and Hoyle, 2005), numerical weather prediction (NWP) (Notarpietro et al, 2011) and radio occultation (Xia et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

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Assessing the performance of troposphere tomographic modeling using multi-source water vapor data during Hong Kong's rainy season from May to October 2013

Chen

Liu

2016

Atmos. Meas. Tech.

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Abstract. Acquiring accurate atmospheric water vapor spatial information remains one of the most challenging tasks in meteorology. The tomographic technique is a powerful tool for modeling atmospheric water vapor and monitoring the water vapor spatial and temporal distribution/variation information. This paper presents a study on the monitoring of water vapor variations using tomographic techniques based on multi-source water vapor data, including GPS (Global Positioning System), radiosonde, WVR (water vapor radiometer), NWP (numerical weather prediction), AERONET (AErosol RObotic NETwork) sun photometer and synoptic station measurements. An extensive investigation has been carried out using multi-source data collected from May to October 2013 in Hong Kong. With the use of radiosonde observed profiles, five different vertical a priori information schemes were designed and examined. Analysis results revealed that the best vertical constraint is to employ the average radiosonde profiles over the 3 days prior to the tomographic time and that the assimilation of multi-source data can increase the tomography modeling accuracy. Based on the best vertical a priori information scheme, comparisons of slant wet delay (SWD) measurements between GPS data and multi-observational tomography showed that the root mean square error (RMSE) of their differences is 10.85 mm. Multi-observational tomography achieved an accuracy of 7.13 mm km −1 when compared with radiosonde wet refractivity observations. The vertical layer tomographic modeling accuracy was also assessed using radiosonde water vapor profiles. An accuracy of 11.44 mm km −1 at the lowest layer (0-0.4 km) and an RMSE of 3.30 mm km −1 at the uppermost layer (7.5-8.5 km) were yielded. At last, a test of the tomographic modeling in a torrential storm occurring on 21-22 May 2013 in Hong Kong demonstrated that the tomographic modeling is very robust, even during severe precipitation conditions.

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“…Recently, some external information was exploited which tries to improve the initial fields used in tomographic modelling. The initial water vapour fields calculated from COSMIC radio occultation data were used as initial values to enhance the accuracy of iterative algorithms (Xia et al, 2013). Several studies also verified that the performance of tomographic results has been improved by superimposing the 2-D images of integrated water vapour (IWV) derived from interferometric synthetic aperture radar (InSAR) (Heublein et al, 2015;Benevides et al, 2015); however, only the observed signal rays penetrating from the top boundary of the area of interest were used to build the observation equation in previous studies for the most previous studies.…”

Section: Introductionmentioning

confidence: 99%

An improved troposphere tomographic approach considering the signals coming from the side face of the tomographic area

Zhao¹,

Yao²

2017

Ann. Geophys.

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Abstract. The spatio-temporal distribution of atmospheric water vapour information plays a crucial role in the establishment of modern numerical weather forecast models and description of the different weather variations. A troposphere tomographic method has been proposed considering the signal rays penetrating from the side of the area of interest to solve the problem of the low utilisation rate of global navigation satellite system (GNSS) observations. Given the method above needs the establishment of a unit scale factor model using the radiosonde data at only one location in the research area, an improved approach is proposed by considering the reasonability of modelling data and the diversity of the modelling parameters for building a more accurate unit scale factor model. The new established model is established using grid point data derived from the European Centre for Medium-Range Weather Forecasts (ECMWF) and evenly distributed in the tomographic area, which can enhance the number of calculated initial water vapour density values with high accuracy. We validated the improved method with respect to the previous methods, as well as the result from a radiosonde using data from 12 stations from the Hong Kong Satellite Positioning Reference Station Network. The obtained result shows that the number of initial values estimated by the new model is increased by 6.83 %, while the internal and external accuracies are 0.08 and 0.24 g m −3 , respectively. Integrated water vapour (IWV) and water vapour density profile comparisons show that the improved method is superior to previous studies in terms of RMS, MAE, and bias, which suggests higher accuracy and reliability.

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GNSS troposphere tomography based on two-step reconstructions using GPS observations and COSMIC profiles

Cited by 49 publications

References 33 publications

Optimization of GPS water vapor tomography technique with radiosonde and COSMIC historical data

Optimization of GPS water vapor tomography technique with radiosonde and COSMIC historical data

Assessing the performance of troposphere tomographic modeling using multi-source water vapor data during Hong Kong's rainy season from May to October 2013

An improved troposphere tomographic approach considering the signals coming from the side face of the tomographic area

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