Comparison of Integrated Water Vapor from Sun-Photometer and Microwave Radiometer with Gnss Stations in Portugal.

This work presents a comparison of microwave radiometer (MWR) and sun-photometer integrated water vapor (IWV) data using global navigation satellite system (GNSS) IWV as reference in Portugal (2003-2021). A very high correlation is obtained for both instruments, although MWR shows a wet bias and sun-photometers, a dry one. In addition, a dependence of mean bias error (MBE) and standard deviation (SD) on IWV has been observed, increasing as IWV increases.