The use of ground-based GNSS for atmospheric water vapour variation study in Papua New Guinea and its response to ENSO events

Abstract. The spatial and temporal variability distribution of atmospheric water vapour in Papua New Guinea region is investigated using three ground-based GNSS station datasets and are compared with radiosonde data and the ERA-Interim reanalysis to generate the atmospheric precipitable water vapour (PWV) products over PNG from 2000 to 2019. From this product, PWV variations on multiple timescales are studied, with the water vapour products of GNSS and ERA-Interim in good agreement with their large-scale changes, which is reflective of the large-scale water vapour transport. At daily periods, the diurnal amplitudes of GNSS is larger at the mainland station (3.5 mm) than the two island stations (1–1.8 mm). The ERA-Interim amplitudes are smaller than GNSS on a daily basis, and do not capture the diurnal phases correctly. The estimated long-term PWV linear trends are predominantly positive and statistically significant which is in agreement in sign to the increase in moisture expected by the Clausius-Clapeyron equation under the background of global temperature rise. In addition, the regional impact of PWV in PNG in response to the El Niño- Southern Oscillation events are analysed using a correlation analysis, focusing on the dynamic influence of the large-scale nature of the 2010–2012 Bimodal La Niña and 2015–2016 El Niño events. The sea surface temperature anomaly in the Niño 3.4 and Niño 4 regions are selected to describe these two events. Both events portray overall negative correlation characteristics at the three GNSS stations with stations PNGM and RVO_ showing the strongest correlation during the 2010–2011 La Niña event significant at a 99 % confidence level.