Evaluation of the ZWD/ZTD Values Derived from MERRA-2 Global Reanalysis Products Using GNSS Observations and Radiosonde Data.

Liangke Huang,Lijie Guo,Shaofeng Xie,Lilong Liu,Jun Chen,Hua Chen

doi:10.3390/s20226440

Abstract

Tropospheric delay is one of the main errors affecting high-precision positioning and navigation and is a key parameter of water vapor detection in the Global Navigation Satellite System (GNSS). The second Modern-Era Retrospective analysis for Research and Applications (MERRA-2) is the latest generation of reanalysis data collected by the National Aeronautics and Space Administration (NASA), which can be used to calculate tropospheric delay products with high spatial and temporal resolution. However, there is no report analyzing the accuracy of the zenith tropospheric delay (ZTD) and zenith wet delay (ZWD) calculated from MERRA-2 data. This paper evaluates the performance of the ZTD and ZWD values derived from global MERRA-2 data using global radiosonde data and International GNSS Service (IGS) precise ZTD products. The results are as follows: (1) Taking the precision ZTD products of 316 IGS stations from around the world from 2015 to 2017 as the reference, the average root mean square (RMS) of the ZTD values calculated from the MERRA-2 data is better than 1.35 cm, and the accuracy difference between different years is small. The bias and RMS of the ZTD values show certain seasonal variations, with a higher accuracy in winter and a lower accuracy in summer, and the RMS decreases from the equator to the poles. However, those of the ZTD values do not show obvious variations according to elevation. (2) Relative to the radiosonde data, the RMS of the ZWD and ZTD values calculated from the MERRA-2 data are better than 1.37 cm and 1.45 cm, respectively. Furthermore, the bias and RMS of the ZWD and ZTD values also show some temporal and spatial characteristics, which are similar to the test results of the IGS stations. It is suggested that MERRA-2 data can be used for global tropospheric vertical profile model construction because of their high accuracy and good stability in the global calculation of the ZWD and ZTD.

Highlights

Tropospheric delay is a key factor affecting high-precision spatial positioning, such as the GlobalNavigation Satellite System (GNSS), very long baseline interferometry (VLBI) and satellite laser ranging (SLR), which are the basic data in atmospheric scientific exploration [1,2,3,4]
The results show that the MERRA-2 data have high accuracy and stability in calculating the zenith tropospheric delay (ZTD) information globally, which is better than the accuracy of the Global Geodetic Observing System (GGOS) atmospheric grid ZTD products, and the global root mean square (RMS) is approximately 1.73 cm [24]
In view of the fact that there is no report evaluating the accuracy of the zenith wet delay (ZWD) and ZTD values calculated from the MERRA-2 data in the world, in this paper, the accuracy of the integration calculation of the ZWD and ZTD values from

Summary

Introduction

Tropospheric delay is a key factor affecting high-precision spatial positioning, such as the GlobalNavigation Satellite System (GNSS), very long baseline interferometry (VLBI) and satellite laser ranging (SLR), which are the basic data in atmospheric scientific exploration [1,2,3,4]. Tropospheric delay is a key factor affecting high-precision spatial positioning, such as the Global. With the continuous improvement in the GNSS positioning algorithm, the ZTD information from regional or global GNSS stations with high precision and high time resolution can be obtained through GNSS precision data processing. Service (IGS) and Crustal Movement Observation Network of China (CMONOC) provide global users with precise ZTD information for free, which in turn can provide important data support for high-precision GNSS applications. It is obvious that the precise ZTD information provided by the global GNSS reference station is not the optimal choice in the selection of data sources for the construction of a global high-precision and high-resolution tropospheric delay model. Atmospheric reanalysis data, such as National Centers for Environmental Prediction (NCEP) reanalysis data and European Center for Medium-Range Weather

Methods

Results

Conclusion