Detecting shifts in tropical moisture imbalances with satellite-derived isotope ratios in water vapor
Detecting shifts in tropical moisture imbalances with satellite-derived isotope ratios in water vapor
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DOI：
10.1002/2016jd026222
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发表时间：
2017-06-16
影响因子：
4.4
通讯作者：
Wood, R.
中科院分区：
文献类型：
--
作者：
Bailey, A.;Blossey, P. N.;Wood, R.
随着全球气温的上升，蒸发（E）和降水（P）的区域差异可能会变得更加不同，导致热带地区以E为主的干燥地区变得干燥，而以P为主的潮湿地区变得更加潮湿。模型表明，这种强化的水循环应该已经发生，但是，定量验证这些变化是复杂的固有困难，在测量E和P具有足够的空间覆盖范围和分辨率。本文提出了一种新的度量方法，用于跟踪区域水分不平衡的变化（例如，E-P），并利用遥感反演和热带气候模式模拟评估其有效性。通过相对于水蒸气浓度归一化同位素比，D-q分离出与E-和P-主导制度之间的转变最密切相关的同位素变异性的部分。厄尔尼诺-南方涛动（ENSO）冷、暖位相之间D-q的复合差异证实，当大尺度对流重组发生时，D-q有效地跟踪水文循环的变化。模拟的D-q还表明，在大多数热带地区的E-P的短期变化的敏感性。由于E-P同位素信号在自由对流层水汽转移到降水的同位素比，水汽和降水同位素比的多年观测应该提供关键的证据，在区域水分不平衡的变化，现在和将来。
As global temperatures rise, regional differences in evaporation (E) and precipitation (P) are likely to become more disparate, causing the drier E-dominated regions of the tropics to become drier and the wetter P-dominated regions to become wetter. Models suggest that such intensification of the water cycle should already be taking place; however, quantitatively verifying these changes is complicated by inherent difficulties in measuring E and P with sufficient spatial coverage and resolution. This paper presents a new metric for tracking changes in regional moisture imbalances (e.g., E-P) by defining D(q)the isotope ratio normalized to a reference water vapor concentration of 4mmolmol(-1)and evaluates its efficacy using both remote sensing retrievals and climate model simulations in the tropics. By normalizing the isotope ratio with respect to water vapor concentration, D-q isolates the portion of isotopic variability most closely associated with shifts between E- and P-dominated regimes. Composite differences in D-q between cold and warm phases of El Nino-Southern Oscillation (ENSO) verify that D-q effectively tracks changes in the hydrological cycle when large-scale convective reorganization takes place. Simulated D-q also demonstrates sensitivity to shorter-term variability in E-P at most tropical locations. Since the isotopic signal of E-P in free tropospheric water vapor transfers to the isotope ratios of precipitation, multidecadal observations of both water vapor and precipitation isotope ratios should provide key evidence of changes in regional moisture imbalances now and in the future.