Effects of land cover type conversion on water exchange and climate change in the source area of the Yellow River

The surface radiation and energy flux in the source area of the Yellow River are estimated by using the Moderate Resolution Imaging Spectroradiometer products from 2000 to 2019 and verified through the in situ observed data. The changes in land cover type and its effect on water exchange and climate are analyzed. Results show that the latent heat estimated by Priestley-Taylor formula in the energy limited area is close to the measured value, and the root mean square error is 17.8 W m −2 . From 2000 to 2019, the daytime land surface temperature (LST) in the source area of the Yellow River mainly shows a negative change trend and decreases significantly in some areas, about − 0.2 °C/a. The nighttime LST shows a positive change trend, and the trend is mainly concentrated at 0–0.15 °C/a. The trend of average land surface temperature calculated from daytime and nighttime LST is mainly concentrated between ± 0.05 °C/a, with a weak warming trend. The LST difference between day and night decreases significantly, and the variation values are mainly concentrated in the range of 0–0.3 °C/a. The albedo in the study area mainly shows a positive trend, and the change value is mainly concentrated between − 0.002 and 0.004/a. The net radiation ( Rn ) decreases, and the sensible heat ( Hs ) and latent heat ( LE ) show a negative trend. The change in land cover type in the source area of the Yellow River mainly occurred in 2016 and 2017. The conversion between grasslands and barren accounts for 70% of the total conversion times. The conversion between grasslands and croplands accounts for 11%. The conversion between water body and barren accounts for 5.9%. The conversion between grasslands and water body accounts for 5.1%, and the other thirty conversions of land cover type account for 8% of the total conversion times. In the dominant land cover conversion type, the mutual conversion between grasslands and barren amplifies the reduction of daytime LST, decelerates the increase in average land surface temperature, and inhibits the water exchange between land and atmosphere because the cooling effect caused by the conversion from barren to grasslands is significantly stronger than the warming effect caused by the conversion from grasslands to barren. Grassland protection is still an important task of ecological protection in the source area of the Yellow River.