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Harrison, E. F.

Publications and source records attributed to Harrison, E. F..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1995

Absorption of Solar Radiation by Clouds: Observations Versus Models

There has been a long history of unexplained anomalous absorption of solar radiation by clouds. Collocated satellite and surface measurements of solar radiation at five geographically diverse locations showed significant solar absorption by clouds, resulting in about 25 watts per square meter more global-mean absorption by the cloudy atmosphere than predicted by theoretical models. It has often been suggested that tropospheric aerosols could increase cloud absorption. But these aerosols are temporally and spatially heterogeneous, whereas the observed cloud absorption is remarkably invariant with respect to season and location. Although its physical cause is unknown, enhanced cloud absorption substantially alters our understanding of the atmosphere's energy budget.

Cess, R. D.↗
NASA NTRS1994

Radiation budget measurements for the eighties and nineties

The Earth Radiation Budget Experiment (ERBE) consisted of a scanning radiometer and non-scanning radiometers on each of three spacecraft. These instruments began flying in October 1984. The nonscanning radiometers continue to operate, providing broadband radiation measurements of the Earth's outgoing longwave radiation and reflected solar radiation, in addition to measurements of the solar output. The Clouds and Earth Radiant Energy System (CERES) features a scanning radiometer, which is an improved version of the ERBE scanning radiometer, and will fly on the Tropical Rainfall Measurement Mission and Earth Observation System platforms in the late nineties. The CERES project will provide not only radiant fluxes at the 'top of the atmosphere' (TOA), but also at the surface and will compute radiant flux divergence through the atmosphere.

Smith, G. L.↗
NASA NTRS1993

Radiative climate forcing by the Mount Pinatubo eruption

Radiative flux anomalies derived from the NASA spaceborne Earth Radiation Budget Experiment were used to determine the volcanic radiative forcing that followed the eruption of Mount Pinatubo in June 1991. They are the first unambiguous, direct measurements of large-scale volcanic forcing. The volcanic aerosols caused a strong cooling effect immediately; the amount of cooling increased through September 1991 as shortwave forcing increased relative to the longwave forcing. The primary effects of the aerosols were a direct increase in albedo over mostly clear areas and both direct and indirect increases in the albedo of cloudy areas.

Minnis, P.↗
NASA NTRS1990

Seasonal variation of cloud radiative forcing derived from the Earth Radiation Budget Experiment

The impact of clouds on the earth's radiation balance is assessed in terms of longwave, shortwave, and net cloud forcing by using monthly averaged clear-sky and cloudy-sky flux data derived from the NASA Earth Radiation Budget Experiment (ERBE). Emphasis is placed on regional measurements, regional cloud forcing, zonal cloud forcing, and snow and ice contributions. It is shown that the global mean cooling varied from 14 to 21 W/sq m between April 1985 and January 1986; hemispherically, the longwave and shortwave cloud forcing nearly cancel each other in the winter hemisphere, while in the summer the negative shortwave cloud forcing is significantly lower than the longwave cloud forcing, producing a strong cooling. The ERBE data reveal that globally, hemispherically, and zonally, clouds have a significant effect on the radiative heating gradients.

Harrison, E. F.↗
NASA NTRS1990

Time dependence of the earth's radiation fields determined from ERBS and NOAA-9 satellites

Satellite measurements from the Earth Radiation Budget Experiment (ERBE) are providing important quantitative data on the diurnal variability of broadband shortwave and longwave radiation. The results derived from the combination of the Earth Radiation Budget Satellite (ERBS) and NOAA-9 indicate that the largest diurnal variations in longwave radiation occur typically over deserts and over land areas which experience intense convective activity. Maximum values of the albedo diurnal amplitude factor are over oceans. Seasonal and cloud cover variations have important effects on the diurnal cycles of earth's radiation budget. ERBE results derived for individual regions are in substantial agreement with the diurnal results derived from the Geostationary Operational Environmental Satellite (GOES) measurements.

Harrison, E. F.↗
NASA NTRS1990

Characteristics of the earth's radiation budget derived from the first year of data from the Earth Radiation Budget Experiment

The first year of broadband Earth Radiation Budget Experiment (ERBE) data is analyzed for top-of-the-atmosphere regional variations of outgoing longwave (LW) flux and planetary albedo for total scene as well as clear-sky conditions. The annual variation of radiative parameters is examined for February 1985 through January 1986 for selected regions, latitude zones, and the entire globe. Results show significant seasonal variations for both LW fluxes and albedo. A broad longwave flux maximum (with a relative minimum corresponding to the intertropical convergence zone in the middle) covers the tropics and the subtropics with its center moving about 20 deg in latitude between seasonal extremes. Minimum albedo (about 20 percent) occurs within 15 deg of the equator. In the tropics and midlatitudes, there is a tendency toward higher albedos during the summer. Larger albedos at the higher latitudes are caused by solar zenith angle effects and by increased snow and ice cover. Net warming occurs between 35 deg N and 35 deg S latitude near the equinoxes and in a 90-deg-wide latitude band at the solstices centered around 35 deg latitude in the summer hemisphere. This energy surplus at lower latitudes coupled with an energy deficit in the poleward regions is the primary driver of atmospheric circulations. For the year, the global net radiation is nearly in balance.

Gibson, G. G.↗
NASA NTRS1990

Seasonal variation of the diurnal cycles of earth's radiation budget determined from ERBE

ERBE scanner data from the Earth Radiation Budget Satellite and NOAA-9 satellites obtained from February 1985 through January 1986 are used to investigate the diurnal cycles of both LW radiation and albedo for each month of the year. Seasonal variations of the diurnal cycles are examined for the deserts, vegetated land, and oceans over the globe. Comparisons are made between clear-sky and total-scene conditions. ERBE satellite data showed that many areas of the earth exhibit significant diurnal variations in both LW flux and albedo. The LW diurnal range was found to be greatest for deserts and smallest for oceans, whereas the albedo diurnal amplitude factor is a maximum over the tropical oceans and a minimum over land. Cloud cover and seasonal variations have a major effect on the diurnal cycles. Generally, maximum diurnal ranges were found in the summer hemisphere and minimum values in the winter hemisphere.

Harrison, E. F.↗
NASA NTRS1990

Effect of cloud cover and surface type on earth's radiation budget derived from the first year of ERBE data

One year of ERBE data is analyzed for variations in outgoing LW and absorbed solar flux. Differences in land and ocean radiation budgets as well as differences between clear-sky and total scenes, including clouds, are studied. The variation of monthly average radiative parameters is examined for February 1985 through January 1986 for selected study regions and on zonal and global scales. ERBE results show significant seasonal variations in both outgoing LW and absorbed SW flux, and a pronounced difference between oceanic and continental surfaces. The main factors determining cloud radiative forcing in a given region are solar insolation, cloud amount, cloud type, and surface properties. The strongest effects of clouds are found in the midlatitude storm tracks over the oceans. Over much of the globe, LW warming is balanced by SW cooling. The annual-global average net cloud forcing shows that clouds have a net cooling effect on the earth for the year.

Gibson, G. G.↗
NASA NTRS1990

Analysis of radiation parameters derived from the multisatellite Earth Radiation Budget Experiment

To quantify the diurnal radiative heating and cooling cycles of the earth and the atmosphere, data from instruments on the Earth Radiation Budget Satellite (ERBS) spacecraft and NOAA-9 satellites obtained from February 1985 through January 1986 were used to investigate longwave (LW) and shortwave (SW) flux as well as albedo for each month of the year. Seasonal variations of radiative parameters and their diurnal cycles are examined for the deserts, vegetated land, and oceans over the globe. The results show significant seasonal variations in both the outgoing LW and the absorbed SW flux, and a pronounced difference was found between oceanic and continental surfaces. Over much of the globe, LW warming is balanced by SW cooling, and clouds have a net cooling effect on the earth. Many areas of the earth were found to exhibit significant diurnal variations in both the LW flux and albedo.

Gibson, G. G.↗
NASA NTRS1989

Cloud-radiative forcing and climate - Results from the Earth Radiation Budget Experiment

The spaceborne Earth Radiation Budget Experiment was begun in 1984 to obtain quantitative estimates of the global distributions of cloud-radiative forcing. The magnitude of the observed net cloud forcing is about four times greater than the expected value of radiative forcing from a doubling of CO2; the shortwave and longwave components of cloud forcing are about 10 times as large as those for a CO2 doubling. Small changes in the cloud-radiative forcing fields can therefore play a significant role as a climate-feedback mechanism.

Ramanathan, V.↗
NASA NTRS1988

Diurnal variability of the planetary albedo - An appraisal with satellite measurements and general circulation models

An atmospheric radiation model is used here to illustrate several features associated with modeling the diurnal cycle of the planetary albedo. It is found that even for clear regions there appear to be deficiencies in our knowledge of how to model this quantity. The diurnal amplitude factor, defined as the ratio of the diurnally averaged planetary albedo to that at noon, between two GCMs and measurements made from a geostationary satellite. While reasonable consistency is found, the comparisons underscore difficulties associated with converting local-time albedo measurements, as made from sun-synchronous satellites, to diurnally averaged albedos.

Potter, G. L.↗
NASA NTRS1986

First data from the earth radiation budget experiment (ERBE)

The first data obtained from the Earth Radiation Budget Experiment (ERBE) are presented. These data include emitted infrared radiation, albedo, and estimated scene types for Nov. 15, 1984, as well as measurements of the 'solar constant'. Images from the GOES on the same day are included for comparison with the ERBE scene identification. On an instantaneous basis, clouds appear colder and more reflective than seems to have been noted before. The experiment data will be applied to several key studies of cloud-radiation-climate interactions.

Barkstrom, B. R.↗
NASA NTRS1986

The Earth Radiation Budget Experiment - Early validation results

The primary techniques used to obtain and validate the data of the Earth Radiation Budget Experiment (ERBE) are described, together with preliminary results of the validation. The ERBE consists of radiometers aboard the ERB Satellite, dedicated to a 57-deg orbit, and each of the two NOAA meteorological spacecraft (NOAA 9 and NOAA G) in near polar orbits. The radiometers include scanning narrow field-of-view (FOV) and nadir-looking wide and medium FOV radiometers, and a solar monitoring channel. Measurements of the solar constant by the solar monitors, and the wide and medium FOV radiometers of the ERB and the NOAA 9 spacecraft agree within a fraction of a percent. Comparison of the wide and medium FOV radiometers with the scanning radiometers showed an agreement of 1 to 4 percent. The multiple ERBE satellites are acquiring the first global measurements of regional scale-diurnal variations in the earth's radiation budget. These were verified by comparison with the high-temporal-resolution geostationary satellite data.

Smith, G. L.↗
NASA NTRS1986

Development of algorithms for understanding the temporal and spatial variability of the earth's radiation balance

A brief description is given of how temporal and spatial variability in the earth's radiative behavior influences the goals of satellite radiation monitoring systems and how some previous systems have addressed the existing problems. Then, results of some simulations of radiation budget monitoring missions are presented. These studies led to the design of the Earth Radiation Budget Experiment (ERBE). A description is given of the temporal and spatial averaging algorithms developed for the ERBE data analysis. These algorithms are intended primarily to produce monthly averages of the net radiant exitance on regional, zonal, and global scales and to provide insight into the regional diurnal variability of radiative parameters such as albedo and long-wave radiant exitance. The algorithms are applied to scanner and nonscanner data for up to three satellites. Modeling of dialy shortwave albedo and radiant exitance with satellite samling that is insufficient to fully account for changing meteorology is discussed in detail. Studies performed during the ERBE mission and software design are reviewed. These studies provide quantitative estimates of the effects of temporally sparse and biased sampling on inferred diurnal and regional radiative parameters. Other topics covered include long-wave diurnal modeling, extraction of a regional monthly net clear-sky radiation budget, the statistical significance of observed diurnal variability, quality control of the analysis, and proposals for validating the results of ERBE time and space averaging.

Brooks, D. R.↗
NASA NTRS1986

First diurnal results from the Earth Radiation Budget Experiment

Early results are reported from measurements of the diurnal variability of total and clear-sky regional radiative parameters by the ERBE instruments on one dedicated satellite and the polar-orbiting NOAA-9 satellite. Attention is focused on November 1984, the first complete data set. The scene is identified in terms of longwave and shortwave radiances (daytime) or longwave radiation (night) and maximum likelihood estimates carried out with the addition of Earth Radiation Budget data from Nimbus-7. Analysis of the first data set revealed significant differences between total and clear-sky albedo. The clear-sky and LRE both reach maximum around noon and minimum values at midnight.

Harrison, E. F.↗
NASA NTRS1984

Diurnal variability of regional cloud and clear-sky radiative parameters derived from GOES data. I - Analysis method. II - November 1978 cloud distributions. III - November 1978 radiative parameters

Cloud cover is one of the most important variables affecting the earth radiation budget (ERB) and, ultimately, the global climate. The present investigation is concerned with several aspects of the effects of extended cloudiness, taking into account hourly visible and infrared data from the Geostationary Operational Environmental Satelite (GOES). A methodology called the hybrid bispectral threshold method is developed to extract regional cloud amounts at three levels in the atmosphere, effective cloud-top temperatures, clear-sky temperature and cloud and clear-sky visible reflectance characteristics from GOES data. The diurnal variations are examined in low, middle, high, and total cloudiness determined with this methodology for November 1978. The bulk, broadband radiative properties of the resultant cloud and clear-sky data are estimated to determine the possible effect of the diurnal variability of regional cloudiness on the interpretation of ERB measurements.

Minnis, P.↗
NASA NTRS1983

Orbital and cloud cover sampling analyses for multisatellite earth radiation budget experiments

Computer simulations have been performed to determine the geographical and temporal coverage of various satellite orbits and scanning and nonscanning radiometers for earth radiation budget measurements. These results were used to simulate the sampling of a diurnally varying cloud and radiation field for several different satellite systems to estimate errors in regional monthly mean reflected radiation. The combined results indicate that coincient observations with a minimum of one sun-synchronous satellite and a midinclined orbit satellite are needed to obtain the required regional, zonal, and global coverage with sufficient temporal sampling for obtaining accurate estimates of monthly mean reflected solar radiation. Overall, the best sampling capability and lowest errors were obtained with a three-satellite system, i.e., two sun-synchronous satellites with different equatorial crossing times combined with either a 46 or 57-deg orbit satellite. The results from these analyses have been used in defining a joint NASA-NOAA multisatellite mission for an earth radiation budget experiment.

Harrison, E. F.↗