The application of elevation corrected MERRA2 reanalysis ground surface temperature in a permafrost model on the Qinghai-Tibet Plateau

There is an urgent need to evaluate the accuracy of reanalysis datasets to improve the reliability of climate research, hydrology, ecology, engineering work, and so on. The ground surface temperature (GST) is also regarded as a significant upper boundary condition when simulating permafrost distribution. In this study, the newest Modern-Era Retrospective Analysis for the Research and Applications Version 2 (MERRA2) reanalysis GST from the National Aeronautics and Space Administration's (NASA) Global Modeling and Assimilation Office (GMAO) is compared with GST data from 69 meteorological stations over the Qinghai-Tibet Plateau (QTP). Then, elevation correction of the MERRA2 GST was performed for different altitudes on seasonal scales. The correction indicates that the accuracy of raw MERRA2 GST data has been greatly improved after the elevation calibration. The decreased proportions of root mean square error (RMSE) for calibrated GST in winter, autumn, summer, and spring are 88.4, 92.8, 95.7, and 92.8%, respectively. The improvements in the mean bias error (MBE) in winter, autumn, summer, and spring are 88.4, 92.8, 95.7, and 92.8%, respectively. Most of the QTP presents a statistically increasing tendency of 0.2 to 0.5 degrees C/10a for GST at a significance level of 0.01 from 1980 to 2013. Then, the elevation corrected MERRA2 GST was applied in the surface frost number semi-physical permafrost model. The simulated results show that the permafrost area on the QTP is approximately 1.02 x 10(6) km(2) in the early 21st century, excluding lakes and glaciers. The permafrost degradation was characterized by the disappearance of permafrost which mainly occurred in the eastern QTP.