Controls on evapotranspiration in a west Siberian bog
Controls on evapotranspiration in a west Siberian bog
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DOI：
10.1029/2003jd004114
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发表时间：
2004-04
影响因子：
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通讯作者：
K. Shimoyama;T. Hiyama;Y. Fukushima;G. Inoue
中科院分区：
文献类型：
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作者：
K. Shimoyama;T. Hiyama;Y. Fukushima;G. Inoue
[1] 本研究从地表限制因素限制了可用于大气蒸散需求的蒸散量（E）这一角度，分析了西西伯利亚沼泽的蒸散控制因素。E与潜在蒸散量（EP）的比率在0.2到0.9之间，并且与由潜热总体传输系数CE（=βCH，其中β是地表水分可利用性，CH是显热总体传输系数）所代表的地表限制因素的变化明显相关。EP和平衡蒸发量（EEQ）都显示出相似的季节趋势，这表明辐射对EP的季节变化很重要。大气干燥力（Ea）是EP中的一个次要因素，并且在生长季的大部分时间里季节变化较小。然而，由天气尺度平流造成的干燥气团的存在（1999年5月最为常见）显著增强了Ea；因此，EP的季节最大值比EEQ的季节最大值出现得更早。CH的值（0.004 - 0.011）除了泥炭藓（LAIg）外随叶面积指数增加，这表明植被生长通过冠层高度变化对沼泽粗糙度的改变有贡献。β值随着地下水位（zwt）的下降而逐渐降低；泥炭藓的开阔水面面积和含水量取决于zwt。此外，β与物候之间没有显著关系，这意味着蒸发的变化对E的变化的贡献大于蒸腾的变化。因此，植被生长和地表湿度造成的粗糙度变化使蒸散量限制在小于潜在蒸散量的水平。
[1] This study analyzed controls on evapotranspiration (E) from a western Siberian bog, from a perspective that surface constraints limit the E available for atmospheric evapotranspiration demands. Ratios of E to potential evapotranspiration (EP) ranged from 0.2 to 0.9, and were clearly related to changes in surface constraints represented by the bulk transfer coefficient for latent heat CE (= βCH where β is the surface moisture availability and CH is the bulk transfer coefficient for sensible heat). Both EP and equilibrium evaporation (EEQ) showed similar seasonal trends, suggesting the importance of radiation to the seasonal variation of EP. The atmospheric drying power (Ea) was a minor factor in EP and showed less seasonal change during most of the growing season. However, the presence of a dry air mass caused by synoptic scale advection (most frequently observed in May 1999) significantly enhanced Ea; consequently, the seasonal maximum of EP occurred earlier than the seasonal maximum of EEQ. Values for CH (0.004–0.011) increased with leaf area index except Sphagnum moss (LAIg), indicating that vegetation growth contributes to changes in bog roughness through canopy height changes. The β value gradually decreased with decreases in the water table position (zwt); the open water surface area and water content of Sphagnum moss depended on zwt. Furthermore, the absence of a significant relationship between β and phenology implies that changes in evaporation contribute to variations in E more than changes in transpiration. Hence roughness change created by vegetation growth and surface wetness limit evapotranspiration to less than the potential evapotranspiration.