References of "Gérard, Jean-Claude"
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See detailObservations ultraviolettes des planètes géantes et de leurs satellites à l'aide du Télescope Spatial Hubble
Gérard, Jean-Claude ULg; Dols, Vincent

in Nouvelles de la Science et des Technologies (1991)

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See detailThe latitudinal gradient of the NO peak density
Fesen, C. G.; Rusch, D. W.; Gérard, Jean-Claude ULg

in Journal of Geophysical Research (1990), 95

Results are presented from SME observations of the latitudinal gradients of peak NO densities at about 110-km altitude during the solstice and equinox periods from 1982 through 1985. It is shown that the ... [more ▼]

Results are presented from SME observations of the latitudinal gradients of peak NO densities at about 110-km altitude during the solstice and equinox periods from 1982 through 1985. It is shown that the response of the peak NO densities to the declining level of solar activity varies with latitude, with the polar regions exhibiting low sensitivity and the low-latitude regions responding strongly. The SME data also revealed marked asymmetries in the latitudinal structure of the two hemispheres for each season and considerable day-to-day variations in the NO densities. The solar cycle minimum data for June were simulated using a two-dimensional model; results of sensitivity studies performed with varied quenching rate and eddy diffusion coefficient are presented. [less ▲]

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See detailThe warm Cretaceous climate - Role of the long-term carbon cycle
Gérard, Jean-Claude ULg; Dols, Vincent

in Geophysical Research Letters (1990), 17

An annual energy-balance model is coupled to a steady state formulation of the long-term CO2 cycle to investigate the possible sources of global warming of the Cretaceous period. It is found that ... [more ▼]

An annual energy-balance model is coupled to a steady state formulation of the long-term CO2 cycle to investigate the possible sources of global warming of the Cretaceous period. It is found that paleogeography solely is an insufficient factor but that the different latitudinal distribution of continental masses 100 My ago influenced the CO2 cycle and favored a larger content of the atmospheric CO2 level. A larger rate of tectonic activity and the possible influence of the vegetation in a CO2 richer atmosphere provide further sources of atmospheric carbon dioxide increase. The combination of these factors, together with a more vigorous poleward heat transport, provides CO2 levels 5 to 15 times larger than today and a global surface warming within the 6-1 C estimated from paleoindicators. [less ▲]

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See detailSolar cycle variation of thermospheric nitric oxide at solstice
Gérard, Jean-Claude ULg; Fesen, C. G.; Rusch, D. W.

in Journal of Geophysical Research (1990), 95

A coupled, two-dimensional, chemical-diffusive model of the thermosphere is used to study the role of solar activity in the global distribution of nitric oxide. The model calculates self-consistently the ... [more ▼]

A coupled, two-dimensional, chemical-diffusive model of the thermosphere is used to study the role of solar activity in the global distribution of nitric oxide. The model calculates self-consistently the zonally averaged temperature, circulation, and composition for solstice under solar maximum and solar minimum conditions. A decrease of the NO density by a factor of three to four in the E region is predicted from solar maximum to solar minimum. It is found that the main features of the overall morphology and the changes induced by the solar cycle are well reproduced in the model, although some details are not satisfactorily predicted. The sensitivity of the NO distribution to eddy transport and to the quenching of metastable N(2D) atoms by atomic oxygen is also described. [less ▲]

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See detailThe Venus nitric oxide night airglow - Model calculations based on the Venus Thermospheric General Circulation Model
Bougher, S. W.; Gérard, Jean-Claude ULg; Stewart, A. I. F. et al

in Journal of Geophysical Research (1990), 95

The mechanism responsible for the Venus nitric oxide (0,1) delta band nightglow observed in the Pioneer Venus Orbiter UV spectrometer (OUVS) images was investigated using the Venus Thermospheric General ... [more ▼]

The mechanism responsible for the Venus nitric oxide (0,1) delta band nightglow observed in the Pioneer Venus Orbiter UV spectrometer (OUVS) images was investigated using the Venus Thermospheric General Circulation Model (Dickinson et al., 1984), modified to include simple odd nitrogen chemistry. Results obtained for the solar maximum conditions indicate that the recently revised dark-disk average NO intensity at 198.0 nm, based on statistically averaged OUVS measurements, can be reproduced with minor modifications in chemical rate coefficients. The results imply a nightside hemispheric downward N flux of (2.5-3) x 10 to the 9th/sq cm sec, corresponding to the dayside net production of N atoms needed for transport. [less ▲]

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See detailModelling the Climatic Response to Solar Variability: Discussion
Pecker, J*-C; Gérard, Jean-Claude ULg

in Royal Society of London Philosophical Transactions Series A (1990), 330

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See detailModelling the Climatic Response to Solar Variability
Gérard, Jean-Claude ULg

in Royal Society of London Philosophical Transactions Series A (1990), 330

The Sun, the primary energy source driving the climate system, is known to vary in time both in total irradiance and in spectral composition in the ultraviolet. According to solar interior evolution ... [more ▼]

The Sun, the primary energy source driving the climate system, is known to vary in time both in total irradiance and in spectral composition in the ultraviolet. According to solar interior evolution models, the solar luminosity has increased steadily by 25-30% over the past 4 × 10[SUP]9[/SUP] years. Periodic variations are also suspected with characteristic timescales of 11 or 22 years, 80-90 years and possibly longer periods. The ultraviolet radiation below 300 nm also exhibits significant changes over the 27-day solar rotation period as well as the 11-year solar cycle. Variations in the solar constant are expected to produce both direct and indirect (feedback) perturbations in the global surface temperature. A hierarchy of zero- to three-dimensional models have been used to study the complex couplings involved by such effects. The response of a zonally averaged model to possible total irradiance changes associated with the Gleissberg cycle is investigated and compared with measurements of the sea-surface temperature made since 1860. Changes in the solar ultraviolet irradiance modulate the amount and distribution of atmospheric ozone, which is predicted to change by several percent in the stratosphere. These perturbations directly affect the middle atmospheric thermal structure, but may also generate indirect effects that could possibly account for some short-term geophysical signatures of solar activity. The cycle-modulated energetic particle interaction with the middle atmosphere is also a possible source of global climatic perturbations. [less ▲]

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See detailObservation ultraviolette des planètes géantes et de leurs satellites à l'aide du téléescope spatial Hubble
Gérard, Jean-Claude ULg; Dols, V.

in Nouvelles de la Science et des Technologies (1990), 8(3-4), 43-46

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See detailPOSSIBLE COMPOSITION AND CLIMATIC CHANGES DUE TO PAST INTENSE ENERGETIC PARTICLE-PRECIPITATION
Hauglustaine, Didier A.; Gérard, Jean-Claude ULg

in Annales Geophysicae [= ANGEO] (1990), 8(2), 87-96

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See detailModelling the climatic response to solar variability.
Gérard, Jean-Claude ULg

in The Earth's Climate and Variability of the Sun over Recent Millennia: Geophysical, Astronomical and Archaeological Aspects (1990)

The author summarizes the available evidence for intrinsic solar variability and describes the climatic consequences of such variations as predicted by current models. He presents model calculations of ... [more ▼]

The author summarizes the available evidence for intrinsic solar variability and describes the climatic consequences of such variations as predicted by current models. He presents model calculations of the possible temperature signature of the Gleissberg solar cycle and climatic effects of ultraviolet irradiance variations and intense solar charged particle interaction with the Earth's atmosphere. [less ▲]

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See detailTHE MAXIMUM-ENTROPY PRODUCTION PRINCIPLE IN CLIMATE MODELS - APPLICATION TO THE FAINT YOUNG SUN PARADOX
Gérard, Jean-Claude ULg; DELCOURT, D.; François, Louis ULg

in Quarterly Journal Of The Royal Meteorological Society (1990), 116(495), 1123-1132

Current theories of stellar evolution imply that the solar luminosity was 25-30% less than at present during early phases of the Earth's history. The response of the global annual climate to changes of ... [more ▼]

Current theories of stellar evolution imply that the solar luminosity was 25-30% less than at present during early phases of the Earth's history. The response of the global annual climate to changes of the solar input is examined using the maximum entropy production (MEP) principle and a zonal energy balance model including ice-albedo feedback. It is shown that this formulation reproduces satisfactorily the present meridional heat flux and latitudinal temperature distributions. It is found that the model predicts that the efficiency of the meridional heat transport decreases for low values of the solar constant. Consequently, if the solar irradiance is lowered, a progressive development of the polar caps and a decrease of the global surface temperature are obtained without major irreversibility in the system. A comparison with a similar model including diffusive heat transport formalism shows that the value of the critical solar luminosity causing a global glaciation is decreased when the meridional heat fluxes are determined by the MEP principle. [less ▲]

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See detailThe atmosphere's response to solar irradiation.
Hunten, D.M.; Gérard, Jean-Claude ULg; François, Louis ULg

Conference (1989)

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See detailRAPID DEACTIVATION OF N(2D) BY O - IMPACT ON THERMOSPHERIC AND MESOSPHERIC ODD NITROGEN
FESEN, C. G.; Gérard, Jean-Claude ULg; RUSCH, D. W.

in Journal of Geophysical Research. Space Physics (1989), 94(A5), 5419-5426

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See detailClimatic warming due to increasing trace gases: simulations with a seasonal energy balance model
Hauglustaine, Didier A.; Gérard, Jean-Claude ULg; Brasseur, G.

in Proceedings of the 28th Liège International Astrophysical Colloquium (1989)

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See detailOur Changing Atmosphere
Crutzen, Paul; Gérard, Jean-Claude ULg; Zander, Rodolphe ULg

Book - Université de Liège (1989)

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See detailClimatic response to solar variability: simulations with a seasonal energy balance model
Gérard, Jean-Claude ULg

in Proceedings of the 28th Liège International Astrophysical Colloquium (1989)

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See detailAeronomy and paleoclimate
Gérard, Jean-Claude ULg

in Berger, A.; Dickinson, R. E.; Kidson, J. W. (Eds.) Understanding climate change (1989)

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See detailSOURCES AND DISTRIBUTION OF ODD NITROGEN IN THE VENUS DAYTIME THERMOSPHERE
Gérard, Jean-Claude ULg; DENEYE, E. J.; LERHO, M.

in Icarus: International Journal of Solar System Studies (1988), 75(1), 171-184

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See detailOZONE, CLIMATE AND BIOSPHERIC ENVIRONMENT IN THE ANCIENT OXYGEN-POOR ATMOSPHERE
François, Louis ULg; Gérard, Jean-Claude ULg

in Planetary and Space Science (1988), 36(12), 1391-1414

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See detailTHE ROLE OF NITRIC-OXIDE ON THE ZONALLY AVERAGED STRUCTURE OF THE THERMOSPHERE - SOLSTICE CONDITIONS FOR SOLAR-CYCLE MAXIMUM
Gérard, Jean-Claude ULg; ROBLE, R. G.

in Planetary and Space Science (1988), 36(3), 271-279

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