Articles | Volume 23, issue 3
Research article
27 May 2016
Research article |  | 27 May 2016

An improved global zenith tropospheric delay model GZTD2 considering diurnal variations

Yibin Yao, Yufeng Hu, Chen Yu, Bao Zhang, and Jianjian Guo

Abstract. The zenith tropospheric delay (ZTD) is an important atmospheric parameter in the wide application of global navigation satellite systems (GNSS) technology in geoscience. Given that the temporal resolution of the current global zenith tropospheric delay model (GZTD) is only 24 h, an improved model, GZTD2, has been developed by taking the diurnal variations into consideration and modifying the model expansion function. The data set used to establish this model is the global ZTD grid data provided by Global Geodetic Observing System (GGOS) Atmosphere spanning from 2002 to 2009. We validated the proposed model with respect to ZTD grid data from GGOS Atmosphere, which was not involved in modeling, as well as International GNSS Service (IGS) tropospheric product. The obtained results of ZTD grid data show that the global average bias and root mean square (rms) for the GZTD2 model are 0.2 and 3.8 cm, respectively. The global average bias is comparable to that of the GZTD model, but the global average rms is improved by 3 mm. The bias and rms are far better than the EGNOS model and the UNB series models. The testing results from global IGS tropospheric product show the bias and rms (−0.3 and 3.9 cm) of the GZTD2 model are superior to that of GZTD (−0.3 and 4.2 cm), suggesting higher accuracy and reliability compared to the EGNOS model, as well as the UNB series models.

Short summary
By considering the diurnal variations in zenith tropospheric delay (ZTD) and modifying the model expansion function, we developed an improved global empirical ZTD model GZTD2 with higher temporal and spatial resolutions compared to our previous GZTD model. The external validation testing with IGS ZTD data shows the bias and rms for GZTD2 are −0.3 and 3.9 cm respectively, indicating higher accuracy and reliability for geodesy technology compared to GZTD and other commonly used ZTD models.