ZTD_RS time series (2000-2023) calculated from radiosonde profile data, used for the validation of SIRGAS ZTD estimates

Abstract

ZTD values were computed from radiosonde (RS) profile data. Radiosondes located within a maximum distance of 35 km from the GNSS station under validation were selected. The RS profiles were downloaded from the Wyoming Weather Web - University of Wyoming (http://weather.uwyo.edu/upperair/sounding.html). The ZTDRS values were calculated as the sum of the Zenith Hydrostatic Delay (ZHDRS) at the site and the corresponding Zenith Wet Delay (ZWDRS). ZHDRS was computed following Davis et al. (1985), using the atmospheric pressure estimated at the GNSS station height (PGNSS). The calculations were performed based on a classification of the stations (A, B or C) according to their height differences (Δh) between the GNSS station and the corresponding RS station being compared. The ZWDRS was computed following Askne and Nordius (1987), using the refractivity constants of Rüeger (2002), together with the Integrated Water Vapor (IWVacc.) and the mean temperature (Tm). Both variables were obtained by integrating the different levels (k) of the radiosonde profile, from the highest available level (K) down to the height corresponding to the GNSS station (hGNSS)