A comparative study of zenith tropospheric delay and precipitable water vapor estimates using scientific GPS processing software and web based automated PPP service

Pikridas, Christos; Katsougiannopoulos, S.; Zinas, Nicholas

doi:10.1007/s40328-014-0047-7

Cited by 13 publications

(10 citation statements)

References 15 publications

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“…Four out of the 90 GNSS stations are included in the EUREF (European reference frame; [54]) permanent network (EPN). The GNSS-QC group has contributed to the E-GVAP project since 2014, providing NRT ZTD estimates to the European NWP centers [55][56][57].…”

Section: Ztd Observationsmentioning

confidence: 99%

Assessing the Impact of GNSS ZTD Data Assimilation into the WRF Modeling System during High-Impact Rainfall Events over Greece

et al. 2020

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The derivation of global navigation satellite systems (GNSSs) tropospheric products is nowadays a state-of-the-art technique that serves both research and operational needs in a broad range of applications in meteorology. In particular, GNSS zenith tropospheric delay (ZTD) data assimilation is widely applied in Europe to enhance numerical weather predictions (NWPs). The current study presents the first attempt at introducing assimilation of ZTDs, derived from more than 48 stations of the Hellenic GNSS network, into the operational NWP system of the National Observatory of Athens (NOA) in Greece, which is based on the mesoscale Weather Research and Forecasting (WRF) model. WRF was applied during seven high-impact precipitation events covering the dry and wet season of 2018. The simulation employing the ZTD data assimilation reproduces more accurately, compared to the control experiment, the observed heavy rainfall (especially for high precipitation events, exceeding 20 mm in 24h) during both dry and wet periods. Assimilating ZTDs also improves the simulation of intense (>20 mm) convective precipitation during the time window of its occurrence in the dry season, and provides a beneficial influence during synoptic-scale events in the wet period. The above results, which are statistically significant, highlight an important positive impact of ZTD assimilation on the model's precipitation forecast skill over Greece. Overall, the modelling system's configuration, including the assimilation of ZTD observations, satisfactorily captures the spatial and temporal distribution of the observed rainfall and can therefore be used as the basis for examining further improvements in the future. meteorological applications, including nowcasting and numerical weather prediction (NWP) [8][9][10][11], as well as weather monitoring, including extreme events [12][13][14]. Special meteorological interest derives from the near-real time (NRT) ZTDs, which are estimated based on raw GNSS observations. The ZTD is a standard GNSS product expressing the total signal delay in the zenith direction above a receiver [6,15]. This vertical lag contains information on the total columnar amount of water vapor [16].In Europe, collaborative scientific efforts over the past two decades substantially contributed to the development of networks and analysis centers collecting and processing, respectively, GNSS data to compute tropospheric delays. The establishment of the European GNSS water vapor program (E-GVAP; [17]) in 2005 allowed for the operational distribution of NRT ZTD estimates to the meteorological community [6]. This service encouraged the implementation of precipitation forecast impact studies involving the assimilation of NRT ZTD observations into NWP models. Poli et al. [18] found an improvement in the prediction of precipitation patterns over France during spring and summer when assimilating ZTD data into a global four-dimensional variational (4D-var) assimilation and forecasting system. Positive impacts of ZTD data assimilation on precipita...

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Section: Ztd Observationsmentioning

confidence: 99%

Assessing the Impact of GNSS ZTD Data Assimilation into the WRF Modeling System during High-Impact Rainfall Events over Greece

et al. 2020

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“…In this study, GNSS data from two permanent stations from Greece and Cyprus were used. The first is the Elassona station, named ELAS, located at Elassona in Thessaly,Central Greece (39.53 • N,22.12 • E, 303 m) managed by the GNSS_QC team of the Aristotle University of Thessaloniki (Fotiou and Pikridas, 2012;Pikridas et al, 2014). The second is the Nicosia station located at Athalassa to the southeast of Nicosia, named NICO (35.08 • N,33.23 • E, 162 m) that belongs to the Cyprus Department of Meteorology; this station participates in the EPN/EUREF network (Bruyninx, 2004).…”

Section: Gnss and Meteorological Datasetsmentioning

confidence: 99%

“…where, P is the atmospheric pressure, is the station latitude and h the station's orthometric height. Subsequently, we compute the ZWD and finally the quantity IWV (Pikridas et al, 2014). The second calculation scenario was based on the estimation of the same parameters but instead of GPT2w values, we used the ground (real) meteorological records obtained from Vaisala sensors collocated to the respective GNSS receivers at Nicosia and Elassona sites.…”

Section: Retrieval Of Iwv From Gnss Ground Receivers -mentioning

confidence: 99%

“…Lately, a considerable number of studies have been conducted aiming to evaluate the capability of GPT2w model to retrieve precipitable water from GNSS measurements. Rahimi et al (2017) assessed the effect of several tropospheric models including GPT2w on derived precipitable water over southeast Asia, while Olalekan et al (2015) estimated the accuracies of the GPT2w and UNB3m (that is a new version of UNB3, where m stands for "modified") tropospheric correction models over Africa by using global IGS (International GNSS Service) network's GNSS observational tropospheric zenith delay time series. However, to the best of our knowledge, no study has been reported so far assessing the tropospheric delay performance for GNSS integrated water vapor estimation over the south-eastern European region where surface observations and radiosonde information are rare, both spatially and temporally.…”

Section: Introductionmentioning

confidence: 99%

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Tropospheric delay performance for GNSS integrated water vapor estimation by using GPT2w model, ECMWF's IFS operational model and in situ meteorological data

et al. 2018

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Abstract. Tropospheric delay comprises one of the most important error sources in satellite navigation and is caused when radio signals broadcasted by GPS satellites propagate into the atmosphere. It is usually projected onto zenith direction by using mapping functions named as Zenith Tropospheric Delay (ZTD). ZTD is described as the sum of the Zenith Hydrostatic Delay (ZHD) and the Zenith Wet Delay (ZWD) and with the aid of surface pressure and temperature the integrated water vapor can be estimated. The main objective of this study is to evaluate the tropospheric delay performance for GNSS integrated water vapor estimation by using GPT2w model, ECMWF's IFS (ECMWF stands for the European Centre for Medium-Range Weather Forecasts) reanalysis model and ground meteorological data from two stations of the permanent network of Cyprus and Greece. The period from 27 May to 3 June 2018 is characterized by two different synoptic conditions: high pressure with fair weather in central Mediterranean (Greece), on the one hand, and high instability over the upper levels of the atmosphere that resulted in thunderstorms inland and mountainous areas during midday over the Eastern Mediterranean (Cyprus), on the other hand. In general, the results show that both the empirical blind model GPT2w and the ECMWF (IFS) operational model perform well in particular over Nicosia when used for the retrieval of Integrated Water Vapor (IWV) from GNSS measurements, although appreciable deviations were observed between ECMWF (IFS)-retrieved IWV and the one retrieved from GNSS observations by using meteorological measurements. A sharp increase of IWV prior to the abrupt rainfall events during noon on 30 and 31 May over Nicosia was also found.

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“…Water vapor is also the most abundant and a critical component of the greenhouse gases driving global weather and climate changes [4][5][6]. Integrated precipitable water vapor (IPWV, or PW for short) is the total water vapor contained in an air column from the Earth's surface to the top of the atmosphere.…”

Section: Introductionmentioning

confidence: 99%

Metrology Assessment of the Accuracy of Precipitable Water Vapor Estimates from GPS Data Acquisition in Tropical Areas: The Tahiti Case

Zhang

Barriot

et al. 2018

Remote Sensing

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High precision Global Positioning System (GPS) receivers, with the advantages of all-weather work and low cost, are now widely used to routinely monitor precipitable water (PW) vapor. They are so successful that the progressive phasing out of the costly and sparse in situ radio soundings (RS) is now a certainty. Nevertheless, the sub-daily to annual monitoring of high levels of the PW by GPS receivers in the tropics and the equatorial area still needs to be asserted in terms of metrology accuracy. This is the subject of this paper, which focuses on a tropical site located in mid-ocean (Tahiti). The metrology assessment was divided into two steps. Firstly, a GPS internal assessment, with an in-house processing based on the Bernese GNSS Software Version 5.2 and a comparison with the Center for Orbit Determination in Europe (CODE) products. Secondly, an external assessment, with a comparison with RS PW estimates. In contrast with previous works that only used PW estimates from the Integrated Global Radiosonde Archive (IGRA) website, we estimated the RS PW from the balloon raw data. This is especially important in tropical areas, where IGRA estimates only consider balloon measurements taken below approximately 5500 m. We show that, in our case, this threshold is one of the main sources of bias between GPS and RS estimates, and that the formula used to translate the GPS zenith wet delays (ZWD) to PW estimates also needs to be revisited for high level water vapor contents in the atmosphere.

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A comparative study of zenith tropospheric delay and precipitable water vapor estimates using scientific GPS processing software and web based automated PPP service

Cited by 13 publications

References 15 publications

Assessing the Impact of GNSS ZTD Data Assimilation into the WRF Modeling System during High-Impact Rainfall Events over Greece

Assessing the Impact of GNSS ZTD Data Assimilation into the WRF Modeling System during High-Impact Rainfall Events over Greece

Tropospheric delay performance for GNSS integrated water vapor estimation by using GPT2w model, ECMWF's IFS operational model and in situ meteorological data

Metrology Assessment of the Accuracy of Precipitable Water Vapor Estimates from GPS Data Acquisition in Tropical Areas: The Tahiti Case

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