Thermodynamical and radiative impact of the correction of sounding humidity bias in the tropics

Abstract : Accurate measurements of atmospheric water vapor are crucial to many aspects of climate research and atmospheric science. This paper discusses some of the meteorological implications of a bias discovered in the measurement of water vapor in widely deployed radiosonde systems. This problem apparently arose in the early 1990s and a correction scheme has been recently developed that intends to remove the bias. The correction scheme also includes improvements in the humidity measurements in the upper troposphere and near the surface. This scheme has been applied to data taken during the Tropical Ocean and Global Atmosphere Coupled Ocean­Atmosphere Response Experiment (TOGA COARE). The impact of the bias on the general stability of the tropical atmosphere to deep convection, as measured by the convective available potential energy (CAPE) and the convective inhibition (CIN), is quite large. On the basis of the uncorrected data set, one might erroneously conclude that it is difficult to trigger deep convection over the region. When the correction is taken into account, the atmosphere over the tropical western Pacific becomes typically unstable to deep convection, with convective instability similar to that measured from aircraft in the vicinity of active convective sytems. Radiative fluxes are also significantly modified. For clear sky conditions, it is found that, on average, the net surface radiative flux increases by 4 W m-2 due to the humidity correction. Under more realistic cloudy conditions, the differences are weaker, but still significant. Changes in radiative fluxes are explained at first order by the the precipitable water increase.
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Journal articles
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https://hal-meteofrance.archives-ouvertes.fr/meteo-00340111
Contributor : Francoise Guichard <>
Submitted on : Wednesday, November 19, 2008 - 10:58:19 PM
Last modification on : Friday, April 5, 2019 - 8:14:08 PM

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  • HAL Id : meteo-00340111, version 1

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Françoise M. Guichard, D. Parsons, E. Miller. Thermodynamical and radiative impact of the correction of sounding humidity bias in the tropics. Journal of Climate, American Meteorological Society, 2000, 13, pp.3611-3624. ⟨meteo-00340111⟩

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