An investigation of the sensitivity of the clear-sky outgoing longwave radiation to atmospheric temperature and water vapor

Yi Huang, V. Ramaswamy, Brian J Soden

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

The rate at which the outgoing longwave radiation (OLR) responds to perturbations in temperature and moisture plays a fundamental role in determining climate sensitivity. This study examines the clear-sky OLR sensitivities to temperature and water vapor, as quantified by its partial derivatives (radiative Jacobians). The Jacobians, as computed by the Geophysical Fluid Dynamics Laboratory (GFDL)'s line-by-line (LBL) radiative transfer model are used to verify the results from the parameterized GFDL GCM (general circulation model) radiation code. The results show that the (1) Jacobians of OLR due to incremental changes in temperature and water vapor are insensitive to different formulations of water vapor continuum absorption and (2) Jacobians of OLR are properly captured by the GCM longwave band approximation. Simulations with the GCM demonstrate that uncertainties in the formulation of continuum absorption have little impact on the climate model simulation of clear-sky OLR changes in response to prescribed sea surface temperature (SST) perturbation. The numerically computed Jacobians of OLR are used to reconstruct the tropical annual mean OLR from the variations of temperature and water vapor over the period 1980-1999. The reconstructed OLR anomaly time series agrees well with that computed explicitly by the GCM. On the basis of this result, it becomes possible to separate out the temperature and water vapor contributions to the OLR variation. The results show that the temperature contribution dominates the water vapor contribution in the lower and middle troposphere, while in the upper troposphere the two contributions largely offset each other.

Original languageEnglish (US)
Article numberD05104
JournalJournal of Geophysical Research C: Oceans
Volume112
Issue number5
DOIs
StatePublished - Mar 16 2007

Fingerprint

Atmospheric temperature
atmospheric temperature
Steam
longwave radiation
clear sky
water vapor
sky
air temperature
vapors
Radiation
sensitivity
radiation
general circulation model
geophysical fluids
temperature
Troposphere
fluid dynamics
Temperature
Fluid dynamics
troposphere

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science
  • Atmospheric Science
  • Astronomy and Astrophysics
  • Oceanography

Cite this

An investigation of the sensitivity of the clear-sky outgoing longwave radiation to atmospheric temperature and water vapor. / Huang, Yi; Ramaswamy, V.; Soden, Brian J.

In: Journal of Geophysical Research C: Oceans, Vol. 112, No. 5, D05104, 16.03.2007.

Research output: Contribution to journalArticle

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