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
Article

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 

Abbreviations

AC

Advection-condensation

AIRS

Atmospheric Infrared Sounder

AR4

Fourth Assessment Report

BLH

Boundary Layer relative Humidity

BT

Brightness temperature

DJF

December, January and February

ECMWF

European Centre for Medium-Range Weather Forecasts

ERA-Interim

ECMWF ReAnalyses-interim

ERA-40

ECMWF ReAnalyses-40

FIR

Far infrared

FTH

Free tropospheric humidity

IPSL

Institut Pierre-Simon Laplace

ITCZ

Inter Tropical Convergence Zone

JJA

June, July and August

NCEP

National Center for Environmental Prediction

OLR

Outgoing Long wave Radiation

PDF

probability distribution function

RH

Relative Humidity

TS

Temperature of the surface

TOA

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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