A model for obtaining ground temperature from air temperature in permafrost regions on the Qinghai-Tibetan Plateau.

• Analysis the hysteresis characteristic of ground temperature with depth increasing. • Develop models to obtain ground temperatures from air temperature. • Compare the models used to estimate ground temperature at different depths. • Evaluate the applicability of these models in the permafrost regions on the QTP. Air and ground temperatures are important factors contributing to land and atmosphere processes as well as ecosystem dynamics. This paper presents a simple model for simulating ground temperature from air temperature in the permafrost regions on the Qinghai-Tibetan Plateau (QTP). The model takes hysteresis between daily air temperature and ground temperature into consideration as well as exponential and linear functions for annual average ground temperatures at different depths. Results indicate an evident hysteresis in ground temperature with increasing depth. By taking hysteresis into account, the developed model provides improved daily ground temperature estimates compared to those obtain from the original linear regression, at Xidatan (site QT09) and Kunlun Pass (site CN06) in the permafrost regions on the QTP, with an average root mean square error (RMSE), normalized standard error (NSEE), and mean absolute error (MAE) of 1.12 °C, 0.41, and 0.84 °C for QT09, and 1.41 °C, 0.29 and 1.10 °C for CN06, respectively, at all depths. The results indicate that the model that takes hysteresis into account provides monthly ground temperatures that are closest to field observations, with an average RMSE, NSEE, and MAE of 0.63 °C, 0.24, and 0.50 °C, respectively, at QT09 site and 0.92 °C, 0.18 and 0.63 °C, respectively, at CN06 site. In addition, the simulation accuracy of the average annual ground temperature is significantly improved by using the combined exponential and linear model, and this is particularly relevant when drilling boreholes at great depths in permafrost regions. Therefore, these models provide a useful and simple method for simulating ground temperature and modeling permafrost changes under global warming conditions. [ABSTRACT FROM AUTHOR]