Validation of atmospheric water vapor derived from ship-borne GPS measurements in the Chinese Bohai Sea

Atmospheric water vapor (AWV) was investigated for the first time in the Chinese Bohai Sea using a GPS receiver aboard a lightweight (300-ton) ship. An experiment was conducted to retrieve the AWV using the state-of-the-art GPS precise point positioning (PPP) technique. The effects of atmospheric weighted mean temperature model and zenith wet delay constraint of random walk process on GPS AWV estimates were discussed in the PPP estimation system. The GPS-derived precipitable water vapor (PWV) and slant-path water vapor (SWV) were assessed by comparing with those derived from the Fifth Generation NCAR/Penn State Mesoscale Model (MM5) model. Results showed the PWV and SWV differences between those derived from both GPS and MM5 are 1.5 mm RMS with a bias of 0.2 mm and 3.9 mm RMS with a bias of -0.7 mm respectively. These good agreements indicate that the GPS-derived AWV in dynamic environments has a comparable accuracy with that of the MM5 model. This suggests that high accuracy and high spatio-temporal resolution humidity fields can be obtained using GPS in the Chinese Bohai Sea, which offers a significant potential for meteorological applications and climate studies in this region.