Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Importance of rain evaporation and continental convection in the tropical water cycle


Atmospheric moisture cycling is an important aspect of the Earth’s climate system, yet the processes determining atmospheric humidity are poorly understood1,2,3,4. For example, direct evaporation of rain contributes significantly to the heat and moisture budgets of clouds5, but few observations of these processes are available6. Similarly, the relative contributions to atmospheric moisture over land from local evaporation and humidity from oceanic sources are uncertain3,7. Lighter isotopes of water vapour preferentially evaporate whereas heavier isotopes preferentially condense8,9,10 and the isotopic composition of ocean water is known. Here we use this information combined with global measurements of the isotopic composition of tropospheric water vapour from the Tropospheric Emission Spectrometer (TES) aboard the Aura spacecraft11,12, to investigate aspects of the atmospheric hydrological cycle that are not well constrained by observations of precipitation or atmospheric vapour content. Our measurements of the isotopic composition of water vapour near tropical clouds suggest that rainfall evaporation contributes significantly to lower troposphere humidity, with typically 20% and up to 50% of rainfall evaporating near convective clouds. Over the tropical continents the isotopic signature of tropospheric water vapour differs significantly from that of precipitation8,10,13, suggesting that convection of vapour from both oceanic sources and evapotranspiration are the dominant moisture sources. Our measurements allow an assessment of the intensity of the present hydrological cycle and will help identify any future changes as they occur.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Figure 1: Global distribution of TES observations averaged vertically between 550 and 800 hPa.
Figure 2: Scatter plots of δD versus q H 2 O reveal underlying hydrologic processes.
Figure 3: Contrast between cloudy and clear sky ocean, and continental observations.


  1. Trenberth, K. E. Changes in tropical clouds and radiation. Science 296, 2095 (2002)

    Article  Google Scholar 

  2. Trenberth, K. E., Dai, A. G., Rasmussen, R. M. & Parsons, D. B. The changing character of precipitation. Bull. Am. Meteorol. Soc. 84, 1205–1217 (2003)

    ADS  Article  Google Scholar 

  3. Roderick, M. L. & Farquhar, G. D. The cause of decreased pan evaporation over the past 50 years. Science 298, 1410–1411 (2002)

    ADS  CAS  Google Scholar 

  4. Bosilovich, M. G., Schubert, S. D. & Walker, G. K. Global changes of the water cycle intensity. J. Clim. 18, 1591–1608 (2005)

    ADS  Article  Google Scholar 

  5. Emanuel, K. A., Neelin, J. D. & Bretherton, C. S. On large-scale circulations in convecting atmospheres. Q. J. R. Meteorol. Soc. 120, 1111–1143 (1994)

    ADS  Article  Google Scholar 

  6. Gamache, J. F., Houze, R. A. & Marks, F. D. Dual-aircraft investigation of the inner-core of hurricane Norbert. 3. Water-budget. J. Atmos. Sci. 50, 3221–3243 (1993)

    Article  Google Scholar 

  7. Xue, Y. et al. Role of land surface processes in South American monsoon development. J. Clim. 19, 741–762 (2006)

    ADS  Article  Google Scholar 

  8. Dansgaard, W. Stable isotopes in precipitation. Tellus 16, 436–468 (1964)

    ADS  Article  Google Scholar 

  9. Gat, J. R. Oxygen and hydrogen isotopes in the hydrologic cycle. Annu. Rev. Earth Planet. Sci. 24, 225–262 (1996)

    ADS  CAS  Article  Google Scholar 

  10. Araguas-Araguas, L., Froehlich, K. & Rozanski, K. Deuterium and oxygen-18 isotope composition of precipitation and atmospheric moisture. Hydrol. Process. 14, 1341–1355 (2000)

    ADS  Article  Google Scholar 

  11. Beer, R., Glavich, T. A. & Rider, D. M. Tropospheric Emission Spectrometer. Appl. Opt. 40, 2356–2367 (2001)

    ADS  CAS  Article  Google Scholar 

  12. Worden, J., Bowman, K. & Noone, D. TES observations of the tropospheric HDO/H2O ratio: retrieval approach and characterization. J. Geophys. Res. 111 D16309 doi: 10.1029/2005JD006606 (2006)

    ADS  CAS  Article  Google Scholar 

  13. Gat, J. R. & Matsui, E. Atmospheric water balance in the Amazon basin: an isotopic evapotranspiration model. J. Geophys. Res. 96, 13179–13188 (1991)

    ADS  Article  Google Scholar 

  14. Worden, J. et al. Predicted errors of tropospheric emission spectrometer nadir retrievals from spectral window selection. J. Geophys. Res. Atmos. 109 D09308 doi: 10.1029/2004JD004522 (2004)

    ADS  CAS  Article  Google Scholar 

  15. Hendricks, M. B., DePaolo, D. J. & Cohen, R. C. Space and time variation of δ18O and δD in precipitation: Can paleotemperature be estimated from ice cores?. Glob. Biogeochem. Cycles 14, 851–861 (2000)

    ADS  CAS  Article  Google Scholar 

  16. Schmidt, G. A., Hoffmann, G., Shindell, D. T. & Hu, Y. Modelling atmospheric stable water isotopes and the potential for constraining cloud processes and stratosphere-troposphere water exchange. J. Geophys. Res. 110 D21314 doi: 10.1029/2005JD005790 (2005)

    ADS  CAS  Article  Google Scholar 

  17. Lawrence, J. R. et al. Stable isotopic composition of water vapor in the tropics. J. Geophys. Res. Atmos. 109 D06115 doi: 10.1029/2003JD004046 (2004)

    ADS  CAS  Article  Google Scholar 

  18. Zhang, G. J. Convective quasi-equilibrium in midlatitude continental environment and its effect on convective parameterization. J. Geophys. Res. Atmos. 107 4220 doi: 10.1029/2001JD001005 (2002)

    ADS  Article  Google Scholar 

  19. Arakawa, A. & Schubert, W. H. Interaction of a cumulus cloud ensemble with large-scale environment. 1. J. Atmos. Sci. 31, 674–701 (1974)

    ADS  Article  Google Scholar 

  20. Rosenfeld, D. & Mintz, Y. Evaporation of rain falling from convective clouds as derived from radar measurements. J. Appl. Meteorol. 27, 209–215 (1988)

    ADS  Article  Google Scholar 

  21. Boville, B. A., Rasch, P. J., Hack, J. J. & McCaa, J. R. Representation of clouds and precipitation processes in the Community Atmosphere Model version 3 (CAM3). J. Clim. 19, 2184–2198 (2006)

    ADS  Article  Google Scholar 

  22. Gat, J. R. Atmospheric water balance—the isotopic perspective. Hydrol. Process. 14, 1357–1369 (2000)

    ADS  Article  Google Scholar 

  23. Ehhalt, D. H. Vertical Profiles of HTO, HDO and H2O in the Troposphere. NCAR-TN/STR-100 (National Center for Atmospheric Research, Boulder, 1974)

    Google Scholar 

  24. Taylor, A. B. The Vertical Variations of the Isotopic Concentrations of Tropospheric Water Vapour Over Continental Europe and their Relationship to Tropospheric Structure. Report INS-R-107 (New Zealand Department of Scientific and Industrial Research, Institute of Nuclear Science, Lower Hutt, 1972)

    Google Scholar 

  25. Flanagan, L. B., Comstock, J. P. & Ehleringer, J. R. Comparison of modeled and observed environmental influences on the stable oxygen and hydrogen isotope composition of leaf water in Phaseolus vulgaris L. Plant Physiol. 96, 588–596 (1991)

    CAS  Article  Google Scholar 

Download references


We thank W. Read, D. Waliser, H. Su, F. Li, E. Fetzer and B. Kahn for discussions on this work, and C. Still, J. Rial and W. Riley for comments on earlier versions of this manuscript. The research described in this paper was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration, and at the University of Colorado.

Author Contributions J.W. and K.B. were responsible for the spectroscopic retrievals of the HDO and H2O profiles and data quality assurance. D.N. developed the isotopic models and led interpretation of the data. The TES team (see below) helped with the development, analysis and validation of the TES data.

Author information

Authors and Affiliations



Corresponding author

Correspondence to David Noone.

Ethics declarations

Competing interests

Reprints and permissions information is available at The authors declare no competing financial interests.

Supplementary information

Supplementary Information

This file contains Supplementary Notes, Supplementary Figures 1-2 and additional references. (PDF 1598 kb)

Rights and permissions

Reprints and Permissions

About this article

Cite this article

Worden, J., Noone, D., Bowman, K. et al. Importance of rain evaporation and continental convection in the tropical water cycle. Nature 445, 528–532 (2007).

Download citation

  • Received:

  • Accepted:

  • Issue Date:

  • DOI:

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing