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2009 .

(3 publications)

V. Eymet, R. Fournier, J.-L. Dufresne, S. Lebonnois, F. Hourdin, and M. A. Bullock. Net exchange parameterization of thermal infrared radiative transfer in Venus' atmosphere. Journal of Geophysical Research (Planets), 114:11008, November 2009. [ bib | DOI | ADS link ]

Thermal radiation within Venus atmosphere is analyzed in close details. Prominent features are identified, which are then used to design a parameterization (a highly simplified and yet accurate enough model) to be used in General Circulation Models. The analysis is based on a net exchange formulation, using a set of gaseous and cloud optical data chosen among available referenced data. The accuracy of the proposed parameterization methodology is controlled against Monte Carlo simulations, assuming that the optical data are exact. Then, the accuracy level corresponding to our present optical data choice is discussed by comparison with available observations, concentrating on the most unknown aspects of Venus thermal radiation, namely the deep atmosphere opacity and the cloud composition and structure.

C. Rio, F. Hourdin, J.-Y. Grandpeix, and J.-P. Lafore. Shifting the diurnal cycle of parameterized deep convection over land. Geophysical Research Letters, 36:7809, April 2009. [ bib | DOI | ADS link ]

In most atmospheric circulation models used for climate projections, cloud and convective processes are not explicitly resolved but parameterized. Such models are known to produce a diurnal cycle of continental thunderstorms in phase with insolation, while observed precipitation peaks in late afternoon. We propose a new approach which corrects this long standing bias of parameterized convection. In this approach, deep convection triggering and intensity are controlled by sub-cloud processes: here boundary layer thermals and gust fronts, and potentially orography or surface heterogeneities. The representation of the diurnal cycle of deep convection is greatly improved in 1D mode, with rainfall maximum delayed from midday to late afternoon, provided parameterizations account for the key role played by shallow cumulus in preconditioning deep convection and by gust fronts in the self-sustaining of thunderstorms in the afternoon.

S. Lebonnois, P. Rannou, and F. Hourdin. The coupling of winds, aerosols and chemistry in Titan's atmosphere. Royal Society of London Philosophical Transactions Series A, 367:665-682, February 2009. [ bib | DOI | ADS link ]

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