Paired stable isotopologues in precipitation and vapor: A case study of the amount effect within western tropical Pacific storms

Jessica L. Conroy, David Noone, Kim M. Cobb, Jessica W. Moerman, Bronwen L. Konecky

Research output: Contribution to journalArticle

Abstract

Understanding controls on the stable isotopic composition of precipitation and vapor in the West Pacific Warm Pool is vital for accurate representation of convective processes in models and correct interpretation of isotope-based paleoclimate proxies, yet a lack of direct observational evidence precludes the utility of these isotopic tracers. Results from a measurement campaign at Manus Island, Papua New Guinea from 28 April to 8 May 2013 demonstrate variability in the stable isotopic composition (δD and δ18O) of precipitation and vapor in individual precipitation events and over a 10 day period. Isotope ratios in water vapor and precipitation progressively increased throughout the period of measurement, coincident with a transition from high to low regional convective activity. Vapor isotope ratios approached equilibrium with seawater during the quiescent period and likely reflected downwind advection of distilled vapor and re-evaporation of rainfall during the period of regional convection. On a 5min timescale across individual storms, isotope ratios in precipitation were strongly correlated with isotope ratios in surface vapor. However, individual precipitation isotope ratios were not strongly correlated with surface meteorological data, including precipitation rate, in all storms. Yet across all events, precipitation deuterium excess was negatively correlated with surface temperature, sea level pressure, and cloud base height and positively correlated with precipitation rate and relative humidity. Paired surface precipitation and vapor isotope ratios indicate condensation at boundary layer temperatures. The ratio of these paired values decreased with increasing precipitation rate during some precipitation events, suggesting rain re-evaporation and precipitation in equilibrium with an isotopically distinct upper level moisture source. Results from the short campaign support the interpretation that isotope ratios in precipitation and vapor in the western tropical Pacific are indicators of regional convective intensity at the timescale of days to weeks. However, a nonstationary relationship between rain rate and stable isotope ratios in precipitation during individual convective events suggests that condensation, rain evaporation, moisture recycling, and regional moisture convergence do not always yield an amount effect relationship on intraevent timescales.

Original languageEnglish (US)
Pages (from-to)3290-3303
Number of pages14
JournalJournal of Geophysical Research
Volume121
Issue number7
DOIs
StatePublished - Jan 1 2016

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Precipitation (meteorology)
vapors
Isotopes
isotopes
Vapors
isotope
case studies
isotope ratios
Rain
rain
evaporation
moisture
timescale
Evaporation
Moisture
condensation
isotopic composition
Condensation
warm pool
effect

ASJC Scopus subject areas

  • Geophysics
  • Oceanography
  • Forestry
  • Ecology
  • Aquatic Science
  • Water Science and Technology
  • Soil Science
  • Geochemistry and Petrology
  • Earth-Surface Processes
  • Atmospheric Science
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Palaeontology

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Paired stable isotopologues in precipitation and vapor : A case study of the amount effect within western tropical Pacific storms. / Conroy, Jessica L.; Noone, David; Cobb, Kim M.; Moerman, Jessica W.; Konecky, Bronwen L.

In: Journal of Geophysical Research, Vol. 121, No. 7, 01.01.2016, p. 3290-3303.

Research output: Contribution to journalArticle

Conroy, Jessica L. ; Noone, David ; Cobb, Kim M. ; Moerman, Jessica W. ; Konecky, Bronwen L. / Paired stable isotopologues in precipitation and vapor : A case study of the amount effect within western tropical Pacific storms. In: Journal of Geophysical Research. 2016 ; Vol. 121, No. 7. pp. 3290-3303.
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