Journal
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
Volume 122, Issue 11, Pages 5763-5779Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2016JD026222
Keywords
water isotope; ENSO; TES; water cycle; intensification; amount effect
Categories
Funding
- Joint Institute for the Study of the Atmosphere and Ocean for a postdoctoral research fellowship
- NASA Modeling, Analysis and Prediction Program [NNX13AN47G]
- NSF Paleoclimate program [AGS-1049104]
- Climate and Large Scale Dynamics program as part of a Faculty Early Career Development award [AGS-0955841]
- National Science Foundation
- NASA [467684, NNX13AN47G] Funding Source: Federal RePORTER
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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.
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