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Hogan, J. S.

Publications and source records attributed to Hogan, J. S..

At least 19 records

Radiative-convective equilibrium models of Jupiter and Saturn

Radiative-convective equilibrium models for Jupiter and Saturn have been produced in a study concentrating on the stratospheric energy balance and the possible role of aerosol heating. These models are compared directly with the thermal structure profiles obtained from Voyager radio occultation measurements. The method is based on a straightforward flux divergence formulation derived from earlier work. The balance between absorbed and emitted energies is computed iteratively at each level in the atmosphere, assuming local thermodynamic equilibrium and employing a standard treatment of opacities. Results for Jupiter indicate that a dust-free model furnishes a good mean thermal profile for the stratosphere when compared with the Voyager 1 radio occultation measurements. Observations of the equatorial region exhibit periodic vertical structure. The Saturn models are relatively simple and in good agreement with the Voyager 2 radio occultation temperature profiles at all levels. Aerosol heating played a minor role in Saturn's midlatitude stratospheric energy balance at the time of the Voyager 2 encounter.

Appleby, J. F.

Response of the global climate to changes in atmospheric chemical composition due to fossil fuel burning

Recent modeling of atmospheric chemical processes (Logan et al, 1978; Hameed et al, 1979) suggests that tropospheric ozone and methane might significantly increase in the future as the result of increasing anthropogenic emissions of CO, NO(x), and CH4 due to fossil fuel burning. Since O3 and CH4 are both greenhouse gases, increases in their concentrations could augment global warming due to larger future amounts of atmospheric CO2. To test the possible climatic impact of changes in tropospheric chemical composition, a zonal energy-balance climate model has been combined with a vertically averaged tropospheric chemical model. The latter model includes all relevant chemical reactions which affect species derived from H2O, O2, CH4, and NO(x). The climate model correspondingly incorporates changes in the infrared heating of the surface-troposphere system resulting from chemically induced changes in tropospheric ozone and methane. This coupled climate-chemical model indicates that global climate is sensitive to changes in emissions of CO, NO(x) and CH4, and that future increases in these emissions could augment global warming due to increasing atmospheric CO2.

Hameed, S.

Response of the global climate to changes in atmospheric chemical composition due to fossil fuel burning

Tropospheric ozone and methane might increase in the future as the result of increasing anthropogenic emissions of CO, NOx and CH4 due to fossil fuel burning. Since O3 and CH4 are both greenhouse gases, increases in their concentrations could augment global warming due to larger future amounts of atmospheric CO2. To test this possible climatic impact, a zonal energy-balance climate model has been combined with a vertically-averaged tropospheric chemical model. The latter model includes all relevant chemical reactions which affect species derived from H2O, O2, CH4 and NOx. The climate model correspondingly incorporates changes in the infrared heating of the surface-troposphere system resulting from chemically induced changes in tropospheric ozone and methane. This coupled climate-chemical model indicates that global climate is sensitive to changes in emissions of CO, NOx and CH4, and that future increases in these emissions could enhance global warming due to increasing atmospheric CO2.

Cess, R. D.

Jupiter - Interpretation of the Pioneer 10 infrared radiometer and S-band occultation observations

On the basis of recently calculated models of the Jovian atmosphere, a value of 5.0 was derived for the H2/He mixing ratio from the Pioneer 10 infrared radiometer data. A far-infrared spectrum corresponding to the thermal profile obtained in the Pioneer S-band occultation experiment was also computed. The spectrum strongly suggests a misinterpretation of the data obtained in that experiment.

Hogan, J. S.

The GISS model of the global atmosphere

A description and numerical results are presented for a global atmospheric circulation model developed at the Goddard Institute for Space Studies (GISS). The model version described is a 9-level primitive-equation model in sigma coordinates. It includes a realistic distribution of continents, oceans and topography. Detailed calculations of energy transfer by solar and terrestrial radiation make use of cloud and water vapor fields calculated by the model. The model hydrologic cycle includes two precipitation mechanisms: large-scale supersaturation and a parameterization of subgrid-scale cumulus convection. Results are presented both from a comparison of the 13th to the 43rd days (January) of one integration with climatological statistics, and from five short-range forecasting experiments. In the extended integration, the near-equilibrium January-mean model atmosphere exhibits an energy cycle in good agreement with observational estimates, together with generally realistic zonal mean fields of winds, temperature, humidity, transports, diabatic heating, evaporation, precipitation, and cloud cover.

Somerville, R. C. J.

Error analysis for the Mariner-6 and -7 occultation experiments.

The Mariner-6 and -7 occultation experiments provide sets of Doppler residuals from which physical properties of the Martian atmosphere, such as the ionospheric electron-density distribution and the lower-atmosphere temperature profile, may be derived. The Doppler residuals contain both systematic and random errors. The former are removed during the data reduction, and the latter are analyzed to yield error limits on the derived physical properties of the atmosphere.

Stewart, R. W.

Error analysis in the Mariner 6 and 7 occultation experiments

The Mariner 6 and 7 occultation experiments provide sets of Doppler residuals from which physical properties of the Martian atmosphere may be derived, such as the ionospheric electron density distribution and the lower atmosphere temperature profile. The Doppler residuals contain both systematic and random errors. The former are removed during the data reduction, and the latter are analyzed to yield error limits on the derived physical properties of the atmosphere.

Stewart, R. W.

Radio occultation measurements of the Mars atmosphere with Mariners 6 and 7.

An analysis of the Mariner 6 and 7 occultation data has been completed. Final profiles of temperature, pressure, and electron density have been obtained for the Mariner 6 and 7 entry and exit cases, and results are presented for both the lower atmosphere and the ionosphere. At all four occultation points, the lapse rate of temperature was subadiabatic up to altitudes in excess of 20 km. A pronounced temperature inversion was present above the surface at the Mariner 6 exit point. All four profiles exhibit a sharp, superadiabatic drop in temperature at high altitudes, with temperatures falling below the frost point of carbon dioxide. These results give a strong indication of frozen carbon dioxide in the middle atmosphere of Mars.

Hogan, J. S.

Tests of a procedure for inserting satellite radiance measurements into a numerical circulation model.

Description of experiments designed to test the sensitivity of a new method for retrieving vertical temperature profiles from satellite radiance measurements to the initial guess of temperature distribution. Emphasis is placed on initial guesses of the kind that would be provided by a numerical model of the atmospheric circulation, with the objective of developing a procedure for direct use of satellite radiation measurements as input to a numerical forecasting scheme.

Hogan, J. S.

Results of the Mariner 6 and 7 Mars occultation experiments

Final profiles of temperature, pressure, and electron density on Mars were obtained for the Mariner 6 and 7 entry and exit cases, and results are presented for both the lower atmosphere and ionosphere. The results of an analysis of the systematic and formal errors introduced at each stage of the data-reduction process are also included. At all four occulation points, the lapse rate of temperature was subdadiabatic up to altitudes in excess of 20 km. A pronounced temperature inversion was present above the surface at the Mariner 6 exit point. All four profiles exhibit a sharp, superadiabatic drop in temperature at high altitudes, with temperatures falling below the frost point of CO2. These results give a strong indication of frozen CO2 in the middle atmosphere of Mars.

Hogan, J. S.

Global winds from Nimbus temperature data for July 1970

Simulation studies to determine the best techniques for making use of vertical sounding temperature data are reported. An atmospheric model was developed to accept real SIRS radiance data from Nimbus 4 for June and July 1970. The results were compared to real observations. It was found that the model accepts real temperature data on a continuing basis, and real temperature data determine winds to a useful degree of accuracy.

Hogan, J. S.

Ocean circulation and climatic changes.

Ocean circulation as climate regulator, discussing role in redistributing climate-changing energy input from solar radiation or lunar tidal friction into atmosphere

Hogan, J. S.