Vertical adjustment of water vapor in the lower troposphere by assimilating GNSS tropospheric gradients

Global Navigation Satellite System (GNSS) tropospheric gradients provide critical insights into atmospheric moisture distribution, whereas zenith total delays (ZTD) quantify the integrated moisture content along the zenith direction. Integrating both observation types enables more effective adjustment of moisture fields and correction of their dynamics within numerical models. Clearly, in areas with limited station coverage, assimilating tropospheric gradients alongside ZTD observations enhances model performance. This study investigates improvements to the lower-tropospheric water vapor correction, with particular attention to increasing station density in the GNSS network. A two-month regional simulation is conducted to support this analysis.

Our research will transition from the regional Weather Research and Forecasting model to a global-scale assimilating advanced GNSS observations using the Model for Prediction Across Scales (MPAS), which includes both ground- and satellite-based GNSS observations. This effort is undertaken through the new DFG (German Research Foundation) funded project titled “Assimilation of advanced GNSS atmospheric remote sensing observations into the MPAS system.”

 

Reference:

Thundathil, R., Zus, F., Dick, G. and Wickert, J., 2025. Assimilation of global navigation satellite system (GNSS) zenith delays and tropospheric gradients: a sensitivity study utilizing sparse and dense station networks. Atmospheric Measurement Techniques, 18(19), pp.4907-4922. https://doi.org/10.5194/amt-18-4907-2025