湿地近地面水热交换对陆面过程乃至天气气候变化有着显著影响, 准确量化湿地与大气间的水热交换通量具有重要意义。本文利用中国科学院西北生态环境与资源研究院若尔盖花湖湿地陆面过程与气候变化观测场（下称花湖观测场）2017年3月至2018年3月涡动相关系统的观测数据, 各季节选取3个典型晴天, 分析了若尔盖湿地近地面的感热通量和潜热通量日变化特征, 并与鄂陵湖和玛曲草原的观测值进行对比, 同时计算了湿地下垫面的能量闭合率。结果表明: 若尔盖高寒湿地-大气间的水热交换过程存在着明显的日变化特征。感热通量和潜热通量的日变化过程都为单峰型, 在14:00（北京时, 下同） -15:00达到最大值, 感热通量最大值可达101.7 W·m-2。潜热通量最大值可达412.6 W·m-2。寒冷干燥季节的感热通量日平均值比温暖湿润季节大18.0%; 而温暖潮湿季节潜热通量日平均值比寒冷干燥季节高68.7%。本文还将湿地水热交换过程与玛曲草原以及鄂陵湖湖面的观测数据进行了对比发现: 夏季, 若尔盖湿地近地面与鄂陵湖湖面向大气输送的感热和潜热总量相当, 但湿地日变化幅度远大于湖面, 通常为湖面的4~7倍。玛曲草原夏季感热通量日变幅约为若尔盖湿地的1.5倍, 而湿地夏季潜热通量总量约为草原的1.2倍。在地表向上的通量中, 能量不平衡所占的比例: 春季27.7%, 夏季22.7%, 秋季15.7%, 冬季19.4%。湿地全年主要以潜热的形式向大气输送能量, 夏季潜热通量占有效能量的比例可达58.0%。
The water & heat exchange fluxes between wetland and atmosphere have significant impact on the land surface process and even the weather and climate change.It is of great significance to accurately quantify the water & heat exchange fluxes between the wetland and the atmosphere.By using the observation data of the eddy-covariance system in the Zoige alpine wetland Land Surface Process and Climate Change Observatory (hereinafter referred to as “Flower Lake Observatory”) of the Northwest Institute of Eco-Environment and Resources, Chinese Academy of Sciences, from March 2017 to March 2018.The diurnal cycle characteristics of the sensible heat flux and latent heat flux in the Zoige wetland were analyzed by selecting three fully cloud-free days each season, and inter-compared to the observed values of Ngoring lake and Maqu grassland.The energy closure ratio over the Zoige alpine wetland was calculated.The results show that there are evident diurnal cycles in the water & heat exchange fluxes between the Zoige alpine wetland and the atmosphere.The diurnal variation cycle of sensible heat flux and latent heat flux are unimodal, reaching a maximum at 14:00 to 15:00 (Beijing time).The daily average of sensible heat flux in the cold and dry season is 18.0% larger than that in the warm and humid season; While the daily average of latent heat flux in the warm and humid season is 68.7% higher than that in the cold and dry season.The observed sensible heat flux and latent heat flux are also compared to the ones of the Maqu grassland and the Ngoring lake surface.It is found that the sensible heat and latent heat transported to the atmosphere from the surface of Zoige wetland is similar to that from the surface of Ngoring lake in summer.The diurnal cycle of the wetlands is much larger than that of the lake surface, which is around 4 to 7 times that of the lake surface.The diurnal cycle of sensible heat flux in the Maqu grassland is about 1.5 times of that in the Zoige wetland, while the total latent heat flux of the wetland in summer is about 1.2 times that of the grassland.Among the energy transported upwards from the surface, the proportion of energy imbalance is 27.7% in spring, 22.7% in summer, 15.7% in autumn, and 19.4% in winter.The wetland mainly transfers energy to the atmosphere in the form of latent heat throughout the whole year.The proportion of latent heat flux to the effective energy reaches 58.0% in summer.
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