Effects of land use/land cover on diurnal temperature range in the temperate grassland region of China.

As a fragile ecological zone, the temperate grassland region of China has experienced dramatic land use/land cover (LULC) changes due to human disturbances. So far, the impacts of LULC change on climate especially the diurnal temperature range (DTR) in this region are still not well understood. Based on the OMR (observation minus reanalysis) method, this study investigated the effects of LULC on DTR in the temperate grassland region of China. Considering the possible uncertainty of the results due to spatial resolution of the reanalysis dataset, two reanalysis datasets with different spatial resolutions were utilized. Results showed that LULC generally contributed to the decline of DTR in the temperate grassland region of China during 1980 to 2005. Due to different warming effects on monthly maximum temperature (Tmax) and minimum temperature (Tmin), grassland and forest tend to slightly decrease monthly DTR (approximately -0.053 to -0.050°C/decade and approximately -0.059 to -0.055°C/decade, respectively), while bare land has a slightly positive effect on DTR (approximately 0.018-0.021°C/decade). By contrast, cropland and urban tend to slightly decrease Tmax, obviously increase Tmin and thus result in a rapid decline of DTR (approximately -0.556 to -0.503°C/decade and approximately -0.617 to -0.612°C/decade, respectively). In the temperate grassland region of China, grassland vegetation changes due to human disturbances can have some effects on DTR mainly by changing the Tmax. Conversion from grassland to cropland could decrease the DTR by slowing down the increase of Tmax. But the conversion from grassland to bare land, as well as the reduction of grassland vegetation cover will increase Tmax, and consequently the DTR. The results suggest that grassland degradation is likely to result in daylight warming and increased DTR in the temperate grassland region of China.