Diurnal variations of ground-based GPS-PWV under different solar radiation intensity in the Chengdu Plain

Abstract

The estimated zenith total delays (ZTD) in Chengdu are calculated from the ground-based GPS data using the GPS analytic software package. The 30-min interval precipitable water vapor (PWV) derived from GPS is calculated based on meteorological data observed at automatic weather stations (AWS). Combining the daily global solar radiation and sunshine data, characteristics of GPS-PWV in both strong and weak solar radiation days are analyzed. The relationship between GPS-PWV and surface temperature is also investigated. The results show that the GPS-PWV under weak radiation is larger than that under strong radiation. dPWV (the difference between PWV under the weak and strong radiation days) and dQ (the difference of global radiation) are positively correlated. Without precipitation, dPWV is distinct in the daytime. During the daytime with strong radiation (sunny day), GPS-PWV is negatively correlated with temperature. The GPS-PWV declines mainly after sunrise. While temperature reaches its daily maximum, the GPS-PWV reaches its minimum. During the daytime of weak radiation (cloudy day), GPS-PWV and temperature are positively correlated. Accompanying the temperature rise after sunshine, GPS-PWV increases gradually. However, variation of GPS-PWV is lagged to the variation of temperature due to the greenhouse effect of water vapor.