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利用NCEP气象数据建立模型来追踪青藏高原南部降水的水汽输送过程,并与实测降水中氧稳定同位素数据进行对比分析,讨论了青藏高原南部降水中δ~(18)O波动与水汽输送过程的关系.研究发现降水中极低的δ~(18)O都与低层洋面蒸发水汽输送有关,远距离水汽输送时,水汽输送过程中的降水使得稳定同位素的贫化作用加强,结果实测降水中δ~(18)O很低;降水中低的δ~(18)O值往往伴随着厚层水汽输送,而且高层大气水汽的凝结作用强烈,这一过程也加剧了稳定同位素的贫化,使得实测降水中δ~(18)O很低.而降水中高的δ~(18)O值无论是在季风降雨期的前后还是在季风活动阶段,水汽输送都与高原面上蒸发的水汽有关,而缺乏低海拔洋面蒸发的水汽输送,并且水汽主要来源于北方或西方.模型计算结果与稳定同位素的分馏机理相一致.
The model of NCEP meteorological data was used to track the process of water vapor transport in the southern Qinghai-Tibet Plateau, and compared with the measured oxygen stable isotope data. The relationship between the δ 18 O O precipitation and the water vapor transport process in the southern Qinghai-Tibet Plateau was discussed It is found that the extremely low δ 18 O in the precipitation is related to the evaporation of low level ocean surface water vapor. When the long distance water vapor is transported, the precipitation during the water vapor transport makes the stable isotope depletion stronger. As a result, δ (18) O is very low. The low δ 18 O value in precipitation is often accompanied by thick water vapor transport, and the condensation of high-level atmospheric water vapor is strong. This process also exacerbated the depletion of stable isotope, making the measured Δ 18 O in precipitation is very low, while the δ 18 O values in the middle and high precipitation are both related to the evaporation of water vapor on the plateau surface, both before and after the monsoon rainfall period and during the monsoon period. However, Low-level ocean surface evaporation of water vapor transport, and water vapor mainly comes from the north or the west.Model results are consistent with the stable isotope fractionation mechanism.