Equation (1) in Sec. 3.1.1 indicates that many parameters were included in the Klemen method to depict the influence of various factors, such as radiation, season, vegetation, and topography. The air temperature derived on the basis of this method shows sufficient spatial distribution details, and the spatial pattern of the air temperature depending on the underlying surface conditions is more reasonable (see Sec. 5.3). The Klemen method was proposed by Zakšek24 using observations (from May to December 2005) from dozens of meteorological stations in Slovenia, Germany, and France. Due to the warm and humid climate in Europe, most of the observations from these stations in 2005 fell into the temperature span above 0°C. Thus, Eq. (1), which is based on these observations, may be innately more suitable for use at high temperatures. The simulated instantaneous air temperature and daily average air temperature validated using HOBO observations [Figs. 5 and 6(c)] have high accuracy and may profit from the field observation time between August and September, when the temperature is high. The climate conditions in the study area are different from where Eq. (1) was established; the temperature span is wider and more low temperatures () appear, which may make the regional LST and NDVI in the study area no longer fit the relationship calibrated in Europe at low temperatures.