Chinese Journal of Agrometeorology ›› 2020, Vol. 41 ›› Issue (05): 288-298.doi: 10.3969/j.issn.1000-6362.2020.05.003

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 Mechanistic and Characteristics of Near-surface Energy Balance in Frozen/Non- frozen Soil Period of the Three-River Headwater Region

 ZHANG Gong, HAN Hui-bang, SUN Shou-jia, ZHANG Jin-song, ZHENG Ning   

  1.  1. Anhui Academy of Forestry/Anhui Huangshan Forest Ecosystem National Positioning Observation Station, Hefei 239500, China; 2. Qinghai Province Weather Modification Office, Xining 810001; 3. Research Institute of Forestry, Chinese Academy of Forestry/Key Laboratory of Tree Breeding and Cultivation of State Forestry Administration, Beijing 100091
  • Online:2020-05-20 Published:2020-05-14
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Abstract:  The exchanging of Energy and water between land and atmosphere over Qinghai-Tibet Plateau play an important role in climate system in China and eastern Asia. As the core area of the Qinghai-Tibet Plateau, the Three-River headwater region is an important water conservation area in China, and the heating and energy exchange over there is significantly. However, there is not any observation about interaction between land and atmosphere in the Three-River headwater region due to the formidable natural conditions. To get more information about the heating effect and energy exchange in this region, measurement has been carried out at location of 33°12′N, 96°30′E, with an altitude of 4167m, based on eddy covariance system (CAST3 and Li-7500A) from January to December. The data observed from eddy covariance system in frozen soil period (from January to April and December) and non-frozen soil period (from May to November) were used to analyze the distribution of each energy component, energy balance closure rate and influence factors of the energy balance closure rate in this area, respectively. The results showed that trends of sensible heat, latent heat, and soil heat flux were consistent with net radiation. Each of them had typical unimodal changes on both annual and daily scales. However, there is time lagging between the maximum of latent and soil heat flux. Total daily net radiation and sensible heat flux increased from March and got the maximum at mid-June, with values of 15.03MJ·m-2·d-1 and 7.81MJ·m-2·d-1, respectively. The proportion of sensible heat during non-frozen soil period was 0.38, latent heat was 0.37, and the proportion of soil heat consumption was 0.10, while during the period of frozen soil, the proportion of the above item is 0.54 and 0.19, -0.01, respectively. The annual energy balance closure of the Three-River headwater region was 0.69, energy balance closure rate in frozen / non-frozen soil period was 0.63 and 0.74, respectively. It can be concluded that sensible heat was the main energy budget item during the frozen soil period, and turbulent forcing is the key factor that affects the energy balance closure rate in the Three-Rivers headwater region, while both latent and sensible heat were the ways of energy consumption, and the dominated factors affected energy balance closure rate were thermal and kinetic factors during the non-frozen soil period.

Key words:  Eddy covariance system, Energy balance, Atmospheric stability, Friction velocity, Thermal turbulence

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