利用稳定同位素大气水平衡模式模拟降水中δ^18O的分布

Simulations of δ^(18)O in precipitation using isotopic atmospheric water balance model

利用稳定同位素大气水平衡模式,模拟了2012年全球大气水汽和降水中δ18O的空间分布和时间变化以及降水中δ18O与降水量、温度之间的关系.其目的在于检验稳定同位素大气水平衡模式模拟水稳定同位素循环的能力,揭示稳定同位素效应产生的主要原因,改善对水循环中稳定同位素效应的理解和认识.模拟结果很好地再现了全球降水中δ18O的纬度效应、大陆效应和季节差异.在水循环过程中,引起降水中稳定同位素空间变化和时间变化的原因与蒸发对水汽同位素的富集作用、降水对水汽同位素的贫化作用、凝结温度对水汽同位素贫化程度的影响有关.模拟的降水量效应主要出现在中低纬度海洋和季风区,这种分布形势与δ18O季节差和降水量季节差的分布相对应;模拟的温度效应主要出现在中高纬度陆地,这种分布形势与降水中δ18O季节差的分布形势相对应.在一些低纬度地区,伴随强降水量效应的出现,温度效应也同时出现.

Using the isotope Atmospheric Water Balance Model（ iAWBM）,the spatial distribution and the temporal variations of δ^18O in atmospheric vapor and in precipitation,and the correlations between δ^18O in precipitation and precipitation amount and temperature in 2012 are simulated,in order to examine the capability of iAWBM simulating the water isotope cycle,to deal with the main causes of isotope effects and to improve the understanding of isotope effects in the water cycle. The simulated results reproduce well the latitude effect,continent effect and seasonality of δ^18O in global precipitation. In the water cycle,the causes of producing the spatial and temporal variations of stable isotopes in precipitation are related to the isotopic enrichment in vapor due to evaporation,the isotopic depletion in vapor due to precipitation and isotopic depleted degree in vapor due to condensation temperature. The simulated precipitation amount effect,corresponding to the distributions of the seasonality of δ^18O in precipitation and precipitation amount,occurs mainly in low-mid latitude oceans and monsoon areas. The simulated temperature effect,corresponding to the distribution of the seasonality of δ^18O in precipitation,occurs mainly in mid-high-latitudes continents. However,along with strong amount effect,temperature effect also occurs in some low-latitude areas.