Effects of the Soil Heat Flux Estimates on Surface Energy BalanceClosure over a Semi-Arid Grassland

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  • Funds:

    Supported by the National Basic Research Program of China (2012CB955304), National Natural Science Foundation of China(40830957 and 40175008), and China Postdoctoral Scientific Research Fund (20110490854)

  • doi: 10.1007/s13351-011-0608-4

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  • Soil heat flux is important for surface energy balance (SEB), and inaccurate estimation of soil heat flux often leads to surface energy imbalance. In this paper, by using observations of surface radiation fluxes and soil temperature gradients at a semi-arid grassland in Xilingguole, Inner Mongolia, China from June to September 2008, the characters of the SEB for the semi-arid grassland were analyzed. Firstly, monthly averaged diurnal variations of SEB components were revealed. A 30-min forward phase displacement of soil heat flux (G) observed by a fluxplate at the depth of 5-cm below the soil surface was conducted and its effect on the SEB was studied. Secondly, the surface soil heat flux (Gs) was computed by using harmonic analysis and the effect of the soil heat storage between the surface and the fluxplate on the SEB was examined. The results show that with the 30-min forward phase displacement of observed G, the slope of the ordinary linear regression (OLR) of turbulent fluxes (H+LE) against available energy (Rn–G) increased from 0.835 to 0.842, i.e., the closure ratio of SEB increased by 0.7%, yet energy imclosure of 15.8% still existed in the SEB. When Gs, instead of G was used in the SEB equation, the slope of corresponding OLR of (H+LE) against (Rn–Gs) reached 0.979, thereby the imclosure ratio of SEB was reduced to only 2.1%.
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    沈阳化工大学材料科学与工程学院 沈阳 110142

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Effects of the Soil Heat Flux Estimates on Surface Energy BalanceClosure over a Semi-Arid Grassland

  • 1. Key Laboratory of Arid Climatic Change and Disaster Reduction of Gansu Province, Institute of Arid Meteorology,China Meteorological Administration,Lanzhou 730020 Zhangye National Climatological Observatory,Zhangye 734000;
    Key Laboratory of Arid Climatic Change and Disaster Reduction of Gansu Province, Institute of Arid Meteorology,China Meteorological Administration,Lanzhou 730020;
    Nanjing University of Information Science & Technology,Nanjing 210044;
    Zhangye National Climatological Observatory,Zhangye 734000;
    Zhangye National Climatological Observatory,Zhangye 734000
Funds: Supported by the National Basic Research Program of China (2012CB955304), National Natural Science Foundation of China(40830957 and 40175008), and China Postdoctoral Scientific Research Fund (20110490854)

Abstract: Soil heat flux is important for surface energy balance (SEB), and inaccurate estimation of soil heat flux often leads to surface energy imbalance. In this paper, by using observations of surface radiation fluxes and soil temperature gradients at a semi-arid grassland in Xilingguole, Inner Mongolia, China from June to September 2008, the characters of the SEB for the semi-arid grassland were analyzed. Firstly, monthly averaged diurnal variations of SEB components were revealed. A 30-min forward phase displacement of soil heat flux (G) observed by a fluxplate at the depth of 5-cm below the soil surface was conducted and its effect on the SEB was studied. Secondly, the surface soil heat flux (Gs) was computed by using harmonic analysis and the effect of the soil heat storage between the surface and the fluxplate on the SEB was examined. The results show that with the 30-min forward phase displacement of observed G, the slope of the ordinary linear regression (OLR) of turbulent fluxes (H+LE) against available energy (Rn–G) increased from 0.835 to 0.842, i.e., the closure ratio of SEB increased by 0.7%, yet energy imclosure of 15.8% still existed in the SEB. When Gs, instead of G was used in the SEB equation, the slope of corresponding OLR of (H+LE) against (Rn–Gs) reached 0.979, thereby the imclosure ratio of SEB was reduced to only 2.1%.

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