Comparing AERONET integrated water vapor with GNSS over the Arctic in the context of former comparisons with radiosondes and reanalyses

Abstract. The Integrated Water Vapor (IWV) determination in the Arctic is very important for atmospheric-climate studies. Different measurements and techniques are used for this purpose, having in general low spatial and temporal resolutions, except the Global Navigation Satellite Systems (GNSS), especially in the Arctic due to extreme weather conditions. In this work, the comparison of IWV measured by sun photometers (SP) from AERONET (IWVSP) and IWV measured by GNSS (IWVGNSS) at Arctic sites, is carried out. Taking coincident hourly averaged data IWVSP from 13 AERONET and 35 IWVGNSS sites were selected, covering the period 1997 to 2023. The comparison IWVGNSS versus IWVSP presents very good statistic indicators with the range of absolute and relative Mean Bias Error MBE (rMBE) of 0.007(0.8%)–0.091(15.4%) cm and standard deviation STD (rSTD) of 0.047(6.5%)–0.123(14.4%) cm. The positive bias at all sites detects a dry bias of SP respect to GNSS. Linear regression slopes are greater than 1 at nine sites, and lower at four. Those slopes lower than 1 appears related to higher frequency of IWV lower values (very dry conditions). All sites present Pearson correlation coefficients higher than 0.96, showing a low data dispersion. Results show that for IWV low values, less than 1.5 cm, SP predominates over GNSS, and the opposite when IWV values increase. This work complements two previous ones, where IWV from radiosondes and reanalysis were compared with IWVSP. Although the different data-bases, for coincident hourly, the highest values of IWV are given by GNSS, radiosonde, SP and reanalysis in this order.