Deuterium excess in precipitation of Alpine regions - moisture recycling
Deuterium excess in precipitation of Alpine regions - moisture recycling
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DOI：
10.1080/10256010801887208
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发表时间：
2008-01-01
影响因子：
1.3
通讯作者：
Stichler, Willibald
中科院分区：
文献类型：
--
作者：
Froehlich, Klaus;Kralik, Martin;Stichler, Willibald
本文评估了长期的季节变化的氘过剩（d-过剩=三角洲H-2 -8.delta O-18）在降水站位于北部和南部的奥地利阿尔卑斯山的主脊。它表明，云下蒸发在降水和大陆水分再循环是本地的，分别控制这些变化的区域过程。一般来说，云下蒸发减少，水分再循环增加d-过剩。因此，本文的主要目的是从水分再循环的角度评估d-过量变化，包括确定云下蒸发的影响。由于云下蒸发是由饱和赤字和云底与地面之间的距离，它对d-过量的影响，预计在山区比在低地/山谷站低。为了定量地确定这种差异，我们研究了长期的季节性d-多余的变化，在三个选定的山区和相邻的山谷站测量。山区和山谷站之间的海拔差为470至1665米。适应斯图尔特的“下落水滴”模型[J. Geophys.结果：80（9），1133-1146（1975）.]，我们估计，在选定的山区站（海拔约1600至2250 m.a.s.l.），小于沉淀的1%，并导致d过量减少小于2。对于选定的山谷站，相应的蒸发分数是在最大的7%和d-过量范围的差异高达8。估计的d-过量差异已被用于校正在选定的站点测量的长期d-过量值。最后，估算了通过地表水（包括土壤水）蒸发而再循环的相应水蒸气比例。对于位于阿尔卑斯山主脊以北的两个山区站Patscherkofel和Feuerkogel，经校正的d-过量（7月/8月）的最大季节变化估计在5和6之间，相应的再循环分数在当地降水的2.5-3%之间。据发现，估计的回收分数是在很好的协议与其他方法得到的值。
The paper evaluates long-term seasonal variations of the deuterium excess (d-excess = delta H-2 - 8.delta O-18) in precipitation of stations located north and south of the main ridge of the Austrian Alps. It demonstrates that sub-cloud evaporation during precipitation and continental moisture recycling are local, respectively, regional processes controlling these variations. In general, sub-cloud evaporation decreases and moisture recycling increases the d-excess. Therefore, evaluation of d-excess variations in terms of moisture recycling, the main aim of this paper, includes determination of the effect of sub-cloud evaporation. Since sub-cloud evaporation is governed by saturation deficit and distance between cloud base and the ground, its effect on the d-excess is expected to be lower at mountain than at lowland/valley stations. To determine quantitatively this difference, we examined long-term seasonal d-excess variations measured at three selected mountain and adjoining valley stations. The altitude differences between mountain and valley stations ranged from 470 to 1665 m. Adapting the 'falling water drop' model by Stewart [J. Geophys. Res., 80(9), 1133-1146 (1975).], we estimated that the long-term average of sub-cloud evaporation at the selected mountain stations (altitudes between about 1600 and 2250 m.a.s.l.) is less than 1% of the precipitation and causes a decrease of the d-excess of less than 2. For the selected valley stations, the corresponding evaporated fraction is at maximum 7% and the difference in d-excess ranges up to 8. The estimated d-excess differences have been used to correct the measured long-term d-excess values at the selected stations. Finally, the corresponding fraction of water vapour has been estimated that recycled by evaporation of surface water including soil water from the ground. For the two mountain stations Patscherkofel and Feuerkogel, which are located north of the main ridge of the Alps, the maximum seasonal change of the corrected d-excess (July/August) has been estimated to be between 5 and 6, and the corresponding recycled fraction between 2.5-3% of the local precipitation. It has been found that the estimated recycled fractions are in good agreement with values derived from other approaches.