Comparison of Weighted Mean Temperature in Greenland Calculated by Four Reanalysis Data

Abstract

The weighted mean temperature ( (Formula presented.) ) is a critical parameter for precipitable water vapor (PWV) retrieval in global navigation satellite system (GNSS) meteorology. Reanalysis data are an important data source for (Formula presented.) calculation and (Formula presented.) empirical model establishment. This study uses radiosonde data to evaluate the accuracy and the spatiotemporal variation of (Formula presented.) that is derived from four reanalysis data, namely, the release of the fifth-generation accurate global atmospheric reanalysis (ERA5), the modern-era retrospective analysis for research and applications version 2 (MERRA-2), the NCEP/DOE, and the NCEP/NCAR, from 2005 to 2019 in Greenland, due to the paucity of research on the performance of (Formula presented.) in the polar region that is derived from reanalysis data, particularly on a long temporal scale. The results were as follows: (1) The 15-year mean bias errors (MBEs) and root mean square errors (RMSEs) of (Formula presented.) that were obtained from the four reanalysis data are 0.267 and 0.691 K for the ERA5, −0.247 and 0.962 K for the MERRA-2, 0.192 and 1.148 K for the NCEP/DOE, and −0.069 and 1.37 K for the NCEP/NCAR. The (Formula presented.) that was derived from the ERA5 (ERA5 (Formula presented.) ) has the highest accuracy, followed by the MERRA-2 (Formula presented.), the NCEP/DOE (Formula presented.), and the NCEP/NCAR (Formula presented.). (2) In the inter-annual stability of the (Formula presented.) precision compared with the radiosonde data, the results of the ERA5 are the most stable, followed by the NCEP/DOE (Formula presented.), the NCEP/NCAR (Formula presented.), and the MERRA-2 (Formula presented.). The ERA5 (Formula presented.) have improved from 2005 to 2019. (3) The (Formula presented.) accuracy that was computed by the four reanalysis data exhibits significant seasonal variation characteristics in Greenland, as follows: the summer and the autumn accuracy is higher than that in the winter and the spring, which may be related to the variation of the surface temperature (Ts) accuracy. (4) The (Formula presented.) that was estimated from the four reanalysis data exhibits a consistent spatial distribution, as follows: the (Formula presented.) is smaller in the middle region of Greenland and is greater at the island’s edge. The comparative study of (Formula presented.) that is obtained from the four reanalysis data can serve as a reference for future research on (Formula presented.) model development and water vapor retrieval in polar regions by utilizing reanalysis data.