Arid Zone Research ›› 2023, Vol. 40 ›› Issue (1): 30-38.doi: 10.13866/j.azr.2023.01.04

• Weather and Climate • Previous Articles     Next Articles

Quantify the impacts of four land cover types on surface temperature in the Heihe River Basin

LI Erchen1(),ZHANG Yu1,YUAN Guanghui1,2()   

  1. 1. Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing 210044, Jiangsu, China
    2. Nanjing Xinda Institute of Safety and Emergency Management, Nanjing 210044, Jiangsu, China
  • Received:2022-06-01 Revised:2022-07-11 Online:2023-01-15 Published:2023-02-24

Abstract:

Micrometeorological observations at four sites in the Heihe River basin from June to September 2012 are used to evaluate the direct decomposed temperature metric (DTM) theory and the intrinsic biophysical mechanism (IBPM), as well as to investigate the biophysical effects of land use and land cover change on surface temperature. Through the Heihe Watershed Allied Telemetry Experimental Research (HiWATER) project, the four sites were outfitted with Eddy Covariance Systems and other conventional weather instruments. The desert has the highest land surface temperature both daytime and nighttime. Compared to the desert site, the non-desert sites have average surface cooling effects of -17.8 K and -1.8 K during daytime and nighttime. Both the DTM and IBPM theories are founded on the surface energy balance equation; however, the energy balance ratios at the four sites range between 80% and 90% during the day and less than 30% at night. To revise the two theories, we distribute the imbalance term to the sensible and latent heat fluxes in proportion to the Bowen ratio. The biophysical effects of different types of land on surface temperature are then investigated by comparing the quantitative results of the two revised theories. The calculated surface temperature of DTM theory and IBPM theory agrees well with the observed results after forcing the energy balance closure to the fluxes, especially at night. The revised IBPM theory matches the observed results better than the revised DTM theory. The revised IBPM results show that the non-radiative effect related to the partitioning of available energy plays a significant role in the daytime cooling effect of non-desert sites. Changes in aerodynamic roughness (mean -4.97 K) and Bowen ratio (mean -2.43 K) both contribute a cooling signal during the day, and these cooling effects even outweigh the warming effects of the radiation term (mean +5.21 K). At night, the direct biophysical effects are weaker than during the day, and the indirect effects of the atmospheric background can even offset the direct biophysical effects.

Key words: underlying surface type, biophysical effects, quantitative evaluation method, energy closure correction