Article

Surveys in Geophysics

, Volume 33, Issue 3, pp 565-583

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

  • Rémy RocaAffiliated withLaboratoire de Météorologie Dynamique, Université Pierre et Marie Curie Email author 
  • , Rodrigo GuzmanAffiliated withLaboratoire de Météorologie Dynamique, Université Pierre et Marie Curie
  • , Julien LemondAffiliated withLaboratoire de Météorologie Dynamique, Université Pierre et Marie Curie
  • , Joke MeijerAffiliated withLaboratoire de Météorologie Dynamique, Université Pierre et Marie Curie
  • , Laurence PiconAffiliated withLaboratoire de Météorologie Dynamique, Université Pierre et Marie Curie
  • , Hélène BrogniezAffiliated withLaboratoire Atmosphères, Milieux, Observations Spatiales

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Abstract

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.

Keywords

Free troposphere Humidity Satellite OLR Advection–condensation paradigm