Albedo, internal heat flux, and energy balance of Saturn
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Hanel, R. A.↗
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The thermal structure and energy balance of the Uranian upper atmosphere
Uranus upper atmosphere occultation observations are reported for August 15-16, 1980, and April 26, 1981. Mean atmospheric light curves of 154 + or - 15 K and 132 + or - 15 K, respectively, are derived from the light curves. A comparison of all available Uranus occultation data since March 1977 suggests a significant mean atmospheric temperature change, with a typical 15 K/year variation. It is suggested that molecular and eddy diffusion, together with atmospheric dynamics, are potentially as important as radiation in the upper atmosphere heat balance of Uranus. The close agreement of occultation immersion and emersion temperatures further suggests that effective meridional transport occurs on Uranus.
French, R. G.↗
Satellite-derived surface energy balance estimates in the Alaskan sub-Arctic
The capabilities of the heat capacity mapping mission (HCMM) satellite are described, together with the numerical model used for data analysis. The HCMM carries the HCM radiometer for remote sensing in the visible and 0.55-1.1 micron wavelength regions, as well as in the 10.5-12.5 micron interval, with the swath being 720 km and each pixel being a square 500 m on a side. The HCMM is intended to aid in hydrological studies of soil moisture, runoff, and evapotranspiration estimates. Data are taken of the albedos and temperatures of vegetation, assuming that all reflection is diffuse. Corrections are made in the algorithm to account for sun angle and the spacecraft distance from the earth. Sample calculations are provided from scans of a coastal plain, mountains, and plateaus of Alaska.
Gurney, R. J.↗
Energy balance of stellar coronae. III - Effect of stellar mass and radius
A homologous transformation is derived which permits the application of the numerical coronal models of Hammer from a star with solar mass and radius to other stars. This scaling requires a few approximations concerning the lower boundary conditions and the temperature dependence of the conductivity and emissivity. These approximations are discussed and found to be surprisingly mild. Therefore, the scaling of the coronal models to other stars is rather accurate; it is found to be particularly accurate for main-sequence stars. The transformation is used to derive an equation that gives the maximum temperature of open coronal regions as a function of stellar mass and radius, the coronal heating flux, and the characteristic damping length over which the corona is heated.
Hammer, R.↗
Modeling long-term changes in forested landscapes and their relation to the Earth's energy balance
The dynamics of the forested parts of the Earth's surface on time scales from decades to centuries are discussed. A set of computer models developed at Oak Ridge National Laboratory and elsewhere are applied as tools. These models simulate a landscape by duplicating the dynamics of growth, death and birth of each tree living on a 0.10 ha element of the landscape. This spatial unit is generally referred to as a gap in the case of the forest models. The models were tested against and applied to a diverse array of forests and appear to provide a reasonable representation for investigating forest-cover dynamics. Because of the climate linkage, one important test is the reconstruction of paleo-landscapes. Detailed reconstructions of changes in vegetation in response to changes in climate are crucial to understanding the association of the Earth's vegetation and climate and the response of the vegetation to climate change.
Shugart, H. H.↗
Far-infrared spectroscopy of galaxies - The 158 micron C(+) line and the energy balance of molecular clouds
Observations of the 158 microns fine-structure line of C(+) toward the nuclei of six gas-rich galaxies are presented. The observations are compared with observations of the CO J = 1-0 and H I 21 cm lines, observations of far-IR continuum emission, and observations of forbidden C II emission with the Galaxy. The forbidden C II line comes from dense, warm gas in UV-illuminated photodissociation regions at the surfaces of molecular clouds. This line is probably optically thin in all but the brightest of galactic sources. The variation of forbidden C II brightness from source to source and its ratio to the integrated infrared continuum intensity agree well with the theoretical prediction that UV absorption by dust controls the C(+) column density. The forbidden C II line is a tracer of molecular clouds, especially those near intense sources of UV radiation.
Crawford, M. K.↗
An investigation of the energy balance of solar active regions using the ACRIM irradiance data
The detection of a significant correlation between the solar irradiance, corrected for flux deficit due to sunspots, and both the 205 nm flux and a photometric facular index were examined. A detailed analysis supports facular emission as the more likely source of correlation with the corrected radiance, rather then the error in sunspot correction. A computer program which simulates two dimensional convection in a compressible, stratified medium was investigated. Subroutines to calculate ionization and other thermodynamic variables were also completed.
Petro, L. D.↗
An investigation of the energy balance of solar active regions using the ACRIM irradiance data
The correlation between the irradiance (as measured by the Active Cavity Radiometer Irradiance Monitor and the Earth Radiation Budget) as corrected for sunspot flux deficit (which is responsible for most of the variance of the uncorrected signal) and both the 205 nm flux (as measured by Nimbus 7) and a photometric facular index is discussed. The computer program which simulates two-dimensional convection in a compressible, stratified medium is described. Equipment which was acquired to perform high precision, white-light observations of sunspot areas, and procedures were tested. Analysis of observations of large scale convective heat inhomogeneities which were obtained in May 1985 was begun.
Petro, L. D.↗
Energy balance constraints on gravity wave induced eddy diffusion in the mesosphere and lower thermosphere
The constraints on turbulence improved by the mesospheric heat budget are reexamined, and the sufficiency of the theoretical evidence to support the hypothesis that the eddy Prandtl number is greater than one in the mesosphere is considered. The mesopause thermal structure is calculated with turbulent diffusion coefficients commonly used in chemical models and deduced from mean zonal wind deceleration. It is shown that extreme mesopause temperatures of less than 100 K are produced by the large net cooling. The results demonstrate the importance of the Prandtl number for mesospheric turbulence.
Strobel, D. F.↗
Estimating regional evapotranspiration from remotely sensed data by surface energy balance models
Spatial and temporal variations of surface radiative temperatures of the burned and unburned areas of the Konza tallgrass prairie were studied. The role of management practices, topographic conditions and the uncertainties associated with in situ or airborne surface temperature measurements were assessed. Evaluation of diurnal and seasonal spectral characteristics of the burned and unburned areas of the prairie was also made. This was accomplished based on the analysis of measured spectral reflectance of the grass canopies under field conditions, and modelling their spectral behavior using a one dimensional radiative transfer model.
Asrar, Ghassem↗
Energy balance and plume dynamics in Triton's lower atmosphere
The present study of the thermal balance-affecting relationships among Triton lower atmosphere thermal conduction, eddy mixing, condensation, and radiative heating indicates that, while the temperature gradient is negative in the lower atmosphere, it becomes positive at higher altitudes due to the downward conduction of ionospheric heat. This temperature profile is essentially consistent with radio-occultation experiment data; the geyser-like plumes observed by Voyager suggest that the Trioton atmosphere's convective and conductive regions join near 10-km altitude, and that the values inferred for the eddy diffusion and heat-transport coefficients indicate a profile reminiscent of the earth's.
Yelle, Roger V.↗
Energy balance components from six sites in a native prairie
The surface-flux stations investigated are of similar design and operation, but are located on different slopes and aspects and provided data with significant variations. The largest difference between sites is noticed in the data for soil heat-flux density, and the general variability is theorized to be related to treatment and locations. The number of surface-flux stations required for the prairie topography can be inferred from the results of the data analysis.
Fritschen, Leo J.↗
Thermal structure and energy balance of Uranus
The present study determines the basic properties of the atmospheric temperature field of Uranus through a combination of earth-based and Voyager measurements. Stellar occultation observations indicate both spatial and temporal variability at microbar pressure levels. The tropospheric and stratospheric vertical structure are established via Voyager radio occultation and infrared measurements as well as earth-based full-disk infrared observations. It is found that the measured lapse rate at pressures greater than about 600 microbar exceeds that for fully equilibrated ortho and para hydrogen. The latitude dependence of the upper tropospheric temperatures is determined from Voyager infrared measurements; remarkably little contrast is found. The weak horizontal structure is consistent with tropospheric zonal winds which decay with height and are directed prograde at midlatitudes but retrograde at low latitudes.
Conrath, B. J.↗
The effect of a non-volatile dust mantle on the energy balance of cometary surface layers
It is likely that large parts of a cometary surface layer consist of porous ices, which are covered by a thin layer of non-volatile debris, whose structure is also fluffy and porous. In this paper the results of model calculations are presented. The calculations show the effect of ice and dust pore sizes and of the dust mantle thickness upon the thermal behavior of such a dust-ice system, when it is irradiated by the sun. In particular, it is found that the average pore size of the ice and the dust material has a large influence both on the dust surface temperature and on the temperature at the dust-ice interface.
Koemle, Norbert I.↗
Triton's surface-atmosphere energy balance
A model encompassing the turbulent transfer of sensible heat as well as insolation, reradiation, and latent heat transport is presently used to investigate the energetics of the surface-atmosphere system of Triton. Under the assumption of a physically plausible range of heat transfer coefficients, the atmospheric temperature 1 km above the surface is found to be 1-3 K hotter than the Triton surface. The observed N2 frosts must have an emissivity lower than unity in order to match a frost temperature at the surface of about 38 K.
Stansberry, John A.↗
Satellite remote sensing of surface energy balance - Success, failures, and unresolved issues in FIFE
Utilizing single-view-angle visible and NIR satellite observations, it was possible to make the necessary radiometric corrections to produce reliable estimates of the simple ratio and the normalized difference vegetation index as inputs to surface evaporation models. Agreement was achieved between helicopter and satellite measures of surface reflectance to within +/-1 percent absolute for both the visible and the NIR bands. A theoretical calculation utilizing radiative transfer models indicates that this translates into a +/-10 percent error in the estimation in Fpar.
Hall, Forrest G.↗
Relative Influence of Initial Surface and Atmospheric Conditions on Seasonal Water and Energy Balances
We constructed and analyzed wet and dry soil moisture composites for the mid-latitude GCIP region of the central US using long climate model simulations made with the NCAR CCM3 and reanalysis products from NCEP. Using the diagnostic composites as a guide, we have completed a series of predictability experiments in which we imposed soil water initial conditions in CCM3 for the GCIP region for June 1 from anomalously wet and dry years, with atmospheric initial conditions taken from June 1 of a year with 'near-normal' soil water, and initial soil water from the near-normal year and atmospheric initial conditions from the wet and dry years. Preliminary results indicate that the initial state of the atmosphere is more important than the initial state of soil water determining the subsequent late spring and summer evolution of sod water over the GCIP region. Surprisingly, neither the composites or the predictability experiments yielded a strong influence of soil moisture on the atmosphere. To explore this further, we have made runs with extreme dry soil moisture initial anomalies imposed over the GCIP region (the soil close to being completely dry). These runs did yield a very strong effect on the atmosphere that persisted for at least three months. We conclude that the magnitude of the initial soil moisture anomaly is crucial, at least in CCM3, and are currently investigating whether a threshold exists, below which little impact is seen. In a complementary study, we compared the impact of the initial condition of snow cover versus the initial atmospheric state over the western US (corresponding to the westward extension of the GAPP program follow-on to GCIP). In this case, the initial prescription of snow cover is far more important than the initial atmospheric state in determining the subsequent evolution of snow cover. We are currently working to understand the very different soil water and snow cover results.
Oglesby, Robert J.↗
Comments on "Tropical Convection and the Energy Balance at the Top of the Atmosphere"
Analyses of the Earth Radiation Budget Experiment (ERBE) data show that the effects of clouds on the solar and thermal infrared radiation in the tropical deep convective regions have a similar magnitude but opposite signs. This small difference in the effects of clouds on radiation led Hartmann et al. (2001) to conclude that the contrast in the net radiation at the top of the atmosphere between the convective and non-convective regions must also be small. However, we have found that the ERBE data do not generally show a small contrast in the radiation between the convective and non-convective regions, and the model used by Hartmann et al., therefore, seems unlikely to represent the real physical processes involving convection, radiation, and climate in an appropriate way.
Chou, Ming-Dah↗