Retrieving high‐resolution tropospheric gradients from multiconstellation GNSS observations

Li, Xingxing; Zus, Florian; Lu, Cuixian; Ning, Tong; Dick, Galina; Ge, Maorong; Wickert, Jens; Schuh, Harald

doi:10.1002/2015gl063856

Cited by 47 publications

(34 citation statements)

References 22 publications

(33 reference statements)

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“…Nevertheless, they suggest that there is scope for significantly improving the use of PWV maps produced by the GNSS systems in meteorological nowcasting. For example, the use of accurate high-resolution tropospheric gradients from multi-GNSS processing could allow us to identify more clearly strong humidity gradients in severe weather situations (Li et al, 2015b). Work on PWV tomography from GPS data (Champollion et al, 2009;Adams et al, 2011;Van Baelen et al, 2011) suggests that one may also look at the time evolution of 3-D water vapour fields, directly addressing the impact of deep convection in those fields, or the relevance of surface fluxes in the moistening of the atmospheric boundary layer in specific storms (Iwasaki and Miki, 2001;Champollion et al, 2004;Brenot et al, 2014).…”

Section: Resultsmentioning

confidence: 99%

On the inclusion of GPS precipitable water vapour in the nowcasting of rainfall

Benevides

Catalão

Miranda

2015

Nat. Hazards Earth Syst. Sci.

131

122

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Abstract. The temporal behaviour of precipitable water vapour (PWV) retrieved from GPS delay data is analysed in a number of case studies of intense precipitation in the Lisbon area, in the period 2010-2012 and in a continuous annual cycle of 2012 observations. Such behaviour is found to correlate positively with the probability of precipitation, especially in cases of severe rainfall. The evolution of the GPS PWV in a few stations is analysed by a least-squares fitting of a broken line tendency, made by a temporal sequence of ascents and descents over the data. It is found that most severe rainfall events occur in descending trends after a long ascending period and that the most intense events occur after steep ascents in PWV. A simple algorithm, forecasting rain in the 6 h after a steep ascent of the GPS PWV in a single station, is found to produce reasonable forecasts of the occurrence of precipitation in the nearby region, without significant misses in what concerns larger rain events, but with a substantial amount of false alarms. It is suggested that this method could be improved by the analysis of 2-D or 3-D time-varying GPS PWV fields or by its joint use with other meteorological data relevant to nowcast precipitation.

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Section: Resultsmentioning

confidence: 99%

On the inclusion of GPS precipitable water vapour in the nowcasting of rainfall

Benevides

Catalão

Miranda

2015

Nat. Hazards Earth Syst. Sci.

131

122

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“…The former is mostly due to horizontal asymmetry in atmospheric pressure, and the latter is due to asymmetry in the water vapour content. The latter is thus more variable in time and space than the former (Li et al, 2015). Regardless, mean gradients should be close to zero, whereas dry gradients may tend to point slightly more to the equator, corresponding to latitudinal changes in atmosphere thickness (Meindl et al, 2004).…”

Section: Quality Of the Observations And Impact On Tropospheric Gradimentioning

confidence: 98%

Tropospheric products of the second GOP European GNSS reprocessing (1996–2014)

2017

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Abstract. In this paper, we present results of the second reprocessing of all data from 1996 to 2014 from all stations in International Association of Geodesy (IAG) Reference Frame Sub-Commission for Europe (EUREF) Permanent Network (EPN) as performed at the Geodetic Observatory Pecný (GOP). While the original goal of this research was to ultimately contribute to the realization of a new European Terrestrial Reference System (ETRS), we also aim to provide a new set of GNSS (Global Navigation Satellite System) tropospheric parameter time series with possible applications to climate research. To achieve these goals, we improved a strategy to guarantee the continuity of these tropospheric parameters and we prepared several variants of troposphere modelling. We then assessed all solutions in terms of the repeatability of coordinates as an internal evaluation of applied models and strategies and in terms of zenith tropospheric delays (ZTDs) and horizontal gradients with those of the ERA-Interim numerical weather model (NWM) reanalysis. When compared to the GOP Repro1 (first EUREF reprocessing) solution, the results of the GOP Repro2 (second EU-REF reprocessing) yielded improvements of approximately 50 and 25 % in the repeatability of the horizontal and vertical components, respectively, and of approximately 9 % in tropospheric parameters. Vertical repeatability was reduced from 4.14 to 3.73 mm when using the VMF1 mapping function, a priori ZHD (zenith hydrostatic delay), and non-tidal atmospheric loading corrections from actual weather data. Raising the elevation cut-off angle from 3 to 7 • and then to 10 • increased RMS from coordinates' repeatability, which was then confirmed by independently comparing GNSS tropospheric parameters with the NWM reanalysis. The assessment of tropospheric horizontal gradients with respect to the ERA-Interim revealed a strong sensitivity of estimated gradients to the quality of GNSS antenna tracking performance. This impact was demonstrated at the Mallorca station, where gradients systematically grew up to 5 mm during the period between 2003 and 2008, before this behaviour disappeared when the antenna at the station was changed. The impact of processing variants on long-term ZTD trend estimates was assessed at 172 EUREF stations with time series longer than 10 years. The most significant site-specific impact was due to the non-tidal atmospheric loading followed by the impact of changing the elevation cut-off angle from 3 to 10 • . The other processing strategy had a very small or negligible impact on estimated trends.

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“…In order to convert accurately SIWV to STDs, we took into account the influence of the hydrostatic horizontal gradients (see e.g. Li et al, 2015b). We used the hydrostatic horizontal gradients derived from the NCEP-GFS for that purpose.…”

Section: Water Vapour Radiometer Measurementsmentioning

confidence: 99%

Inter-technique validation of tropospheric slant total delays

et al. 2017

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Abstract. An extensive validation of line-of-sight tropospheric slant total delays (STD) from Global Navigation Satellite Systems (GNSS), ray tracing in numerical weather prediction model (NWM) fields and microwave water vapour radiometer (WVR) is presented. Ten GNSS reference stations, including collocated sites, and almost 2 months of data from 2013, including severe weather events were used for comparison. Seven institutions delivered their STDs based on GNSS observations processed using 5 software programs and 11 strategies enabling to compare rather different solutions and to assess the impact of several aspects of the processing strategy. STDs from NWM ray tracing came from three institutions using three different NWMs and ray-tracing software. Inter-techniques evaluations demonstrated a good mutual agreement of various GNSS STD solutions compared to NWM and WVR STDs. The mean bias among GNSS solutions not considering post-fit residuals in STDs was −0.6 mm for STDs scaled in the zenith direction and the mean standard deviation was 3.7 mm. Standard deviations of comparisons between GNSS and NWM ray-tracing solutions were typically 10 mm ± 2 mm (scaled in the zenith direction), depending on the NWM model and the GNSS station. Comparing GNSS versus WVR STDs reached standard deviations of 12 mm ± 2 mm also scaled in the zenith direction. Impacts of raw GNSS post-fit residuals and cleaned residuals on optimal reconstructing of GNSS STDs were evaluated at intertechnique comparison and for GNSS at collocated sites. The use of raw post-fit residuals is not generally recommended as they might contain strong systematic effects, as demonstrated in the case of station LDB0. Simplified STDs reconstructed only from estimated GNSS tropospheric parameters, i.e. without applying post-fit residuals, performed the best in all the comparisons; however, it obviously missed part of tropospheric signals due to non-linear temporal and spatial variations in the troposphere. Although the post-fit residuals cleaned of visible systematic errors generally showed a slightly worse performance, they contained significant tropospheric signal on top of the simplified model. They are thus recommended for the reconstruction of STDs, particularly during high variability in the troposphere. Cleaned residuals also showed a stable performance during ordinary days while containing promising information about the troposphere at low-elevation angles.

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Retrieving high‐resolution tropospheric gradients from multiconstellation GNSS observations

Cited by 47 publications

References 22 publications

On the inclusion of GPS precipitable water vapour in the nowcasting of rainfall

On the inclusion of GPS precipitable water vapour in the nowcasting of rainfall

Tropospheric products of the second GOP European GNSS reprocessing (1996–2014)

Inter-technique validation of tropospheric slant total delays

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