Comparison of Integrated Precipitable Water Derived from Cosmic Occultation Data and Ground GPS Measurements

摘要

The integrated Precipitable Water (PW) derived from ground IGS stations is considered as reference because of its high accuracy and long-term stability to validate the PW derived from COSMIC RO sounding data. The one-year comparisons show that both PW are quite consistent for PW below 20 mm, and the PW derived from COSMIC has systemic low bias than ground-GPS PW for PW >40 mm. In general, the rms of PW difference between COSMIC and IGS is about 1.5-3.0mm, and the mean difference is less than 0.5mm, which is acceptable. In addition, the variations of PW difference in the southern hemisphere are obviously fluctuant due to fewer IGS stations over this region, while the mean PW difference is more stable and smaller around 0.5 mm for latitude higher than 25°N and the standard deviation of PW difference is gradually decreases with higher latitude in the northern hemisphere.