Surveys in Geophysics

, Volume 33, Issue 3–4, pp 565–583 | Cite as

Tropical and Extra-Tropical Influences on the Distribution of Free Tropospheric Humidity Over the Intertropical Belt

  • Rémy Roca
  • Rodrigo Guzman
  • Julien Lemond
  • Joke Meijer
  • Laurence Picon
  • Hélène Brogniez


Free tropospheric humidity (FTH) is a key parameter of the radiation budget of the Earth. In particular, its distribution over the intertropical belt has been identified as an important contributor to the water vapour feedback. Idealized radiative transfer computations are performed to underscore the need to consider the whole probability distribution function (PDF) rather than the arithmetical mean of the FTH. The analysis confirmed the overwhelming role of the dry end of the PDF in the radiative perturbation of the top of atmosphere longwave budget. The physical and dynamical processes responsible for the maintenance of this dry part of the FTH distribution are reviewed, and the lateral mixing between the tropics and the extra-tropics is revealed as a major element of the dry air dynamics. The evolution of this lateral mixing in the framework of the global warming is discussed, and perspectives of work are listed as a mean of a conclusion.


Free troposphere Humidity Satellite OLR Advection–condensation paradigm 





Atmospheric Infrared Sounder


Fourth Assessment Report


Boundary Layer relative Humidity


Brightness temperature


December, January and February


European Centre for Medium-Range Weather Forecasts


ECMWF ReAnalyses-interim


ECMWF ReAnalyses-40


Far infrared


Free tropospheric humidity


Institut Pierre-Simon Laplace


Inter Tropical Convergence Zone


June, July and August


National Center for Environmental Prediction


Outgoing Long wave Radiation


probability distribution function


Relative Humidity


Temperature of the surface


Top of atmosphere


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Copyright information

© Springer Science+Business Media B.V. 2012

Authors and Affiliations

  • Rémy Roca
    • 1
  • Rodrigo Guzman
    • 1
  • Julien Lemond
    • 1
  • Joke Meijer
    • 1
  • Laurence Picon
    • 1
  • Hélène Brogniez
    • 2
  1. 1.Laboratoire de Météorologie DynamiqueUniversité Pierre et Marie CurieParisFrance
  2. 2.Laboratoire Atmosphères, Milieux, Observations SpatialesParisFrance

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