Performance of ERA5 data in retrieving Precipitable Water Vapour over East African tropical region

Richard Cliffe Ssenyunzi*, Bosco Oruru, Florence Mutonyi D'ujanga, Eugenio Realini, Stefano Barindelli, Giulio Tagliaferro, Axel von Engeln, Nick van de Giesen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

27 Citations (Scopus)
92 Downloads (Pure)


The accuracy of surface meteorological measurements is vital to derive accurate Global Positioning System (GPS) Precipitable Water Vapour (PWV) data. However, in absence of surface meteorological data, data from Numerical Weather Prediction Models (NWP) are used. The accuracy of these models varies depending on the model, region, season and other climatic conditions. In this study, GPS data for derivation of PWV is collected from 13 geodetic permanent stations for the years 2013 to 2016. Five out of 13 GPS stations are equipped with meteorological sensors. The interpolated European Centre for Medium-Range Weather Forecasts (ECMWF) 5th Re-Analysis (ERA5) dataset at these locations is first validated using the meteorological data from these sensors. The assessment shows that the average root mean square errors (RMSE) of surface pressure and temperature values are about 0.72 hPa and 1.04 K respectively. PWV determined also requires information on the weighted mean temperature (Tm); the Tm at the 13 GPS stations was also evaluated using three methods: the temperature and humidity profiles from ERA5 (ERA5 Tm), as well as the Tm derived from Bevis and Yao Tm - Ts relationships. The Tm derived from ERA5 was used as a reference to assess the errors of the Bevis and Yao Tm. The comparisons show that the average RMSE values of Tm derived from the two methods are 2.05 K and 2.02 K respectively. The GPS PWVs calculated using the ERA5 interpolated data (GPS ERA5 PWV) were compared to GPS PWV calculated using the sensor meteorological data (GPS MET PWV) at the 5 stations. The GPS ERA5 PWV values were used as the reference. The RMSE values of the two PWV datasets are in the range of 0.19 mm to 0.90 mm with overall average value of 0.44 mm. Also the computed ERA5 PWV data are compared to GPS ERA5 PWV at the 13 stations. ERA5 PWV values were used as the reference and the RMS errors of the two PWV values are in the range 1.35 mm to 2.25 mm with the overall average value of 1.66 mm. Regarding the seasonal variations, the stations between latitudes 4 °S and 4 °N and latitudes 12 °S to 4 °S have the highest PWV values in spring and summer while the lowest values occur in summer and winter respectively.

Original languageEnglish
Pages (from-to)1877-1893
Number of pages17
JournalAdvances in Space Research
Issue number8
Publication statusPublished - 2020


  • ERA5
  • GNSS
  • NWP
  • PWV


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