Operational satellites provide global data from multispectral narrowband radiometric scanners such as the Advanced Very High Resolution Radiometer (AVHRR) and the High Resolution Infrared Radiation Sounder (HIRS) found on the polar-orbiting NOAA series of satellites. For many years, the narrowband channels have been utilized to estimate the components of the Earth's radiation budget (ERB). Broadband instruments specially designed for ERB measurements have been available only on experimental satellites. Unfortunately, these instruments have been very intermittent in their coverage, with large gap's in time occurring between the failure of an instrument and the launch of its successor. AVHRR instruments, on the other hand, have been present on every operational NOAA satellite since 1979, making it possible for continuous coverage. The evolution of the ERB products generated from the AVHRR over this period will be discussed, as well as the expectations and plans for the future. This will include a brief tutorial on the generation of the current products, a discussion on anticipated improvements to the algorithms, the use of the HIRS in estimating the outgoing longwave radiation flux, and the development of new products that will enhance our ability to monitor climate and global change.

A method for calibrating satellite radiometers is investigated. A calibrated spectral radiometer carried aboard a U2 aircraft at an altitude of 60 000 ft was aligned with White Sands. New Mexico along the same view vector as the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-9 spacecraft at the time of the spacecraft's overpass on 26 August 1985. Both sets of data have been transformed into best estimates of the radiance at satellite altitude inside the footprint of the aircraft radiometer, allowing an estimate of radiance calibration changes in the AVHRR to be made. It is assumed that both instrument systems are linear, that the spectral response function of AVHRR has not changed from its prelaunch value, and that the zero radiance responses of both instruments are accurately known. Extrapolation of the radiances measured from the aircraft to those expected at satellite altitude is achieved by modeling the experimental conditions at White Sands and calculating the ratio of radiances at the two altitudes through the LOWTRAN VI computer program. Results from data taken within 2 minutes either side of the satellite overpass indicate a 98.9% correlation between the two sets of data, and a change in gain relative to the prelaunch calibration of +2 ± 5% for channel 1 and −2 ± 5% for channel 2 of the NOAA-9 AVHRR. Analysis of other coincident data for the NOAA-9 AVHRR and the aircraft spectral radiometer, including a large dataset from October and November 1986, is now in progress and will establish the day-to-day repeatability of results using this method.

Observations made with the current and proposed narrowband shortwave channels aboard the NOAA series of satellites were simulated for a number of different surfaces (ocean, vegetative land, desert, cloud and snow) using the ATRAD radiation model to study the relative merit of each channel and, in various combinations to predict the broadband albedo. Solar zenith angles were varied over the range from 0 to 60 degrees. The results indicated that for all of the surfaces considered there would be no significant difference in predicting the broadband albedo with either the current (0.58–0.68 μn) or proposed (0.58–0.68 μm) channel 1 of the AVHRR. The proposed narrower channel 2(0.84–0.87 μm), however, would be a better predictor than the current wider channel 2(0.725–1.0 μm). Channel 1 is better than channel 2 for surfaces of low or moderate reflectivity, while over snow, the error in using channel 2 would be less than half of that for channel 1. Combining channels 1 and 2 would reduce the error by abo...

The planetary outgoing longwave radiation has been estimated since 1974 from two different series of NOAA operational polar spacecraft. The first series provided data from June 1974 through February 1978 and was designated “SR” for the scaning radiometers used at that time. This data set has been used in a variety of radiation budget and climate studies, such as that by Ohring and Gruber, 1983. The second satellite system is the currently operational TIROS-N series of satellites. Data from this series began in January 1979 and are continuing. In both systems, estimates of the outgoing longwave radiation are obtained from narrow spectral interval (10–12 μm) window radiances. A comparison is made of the estimates from the two different series of satellites in order to arrive at an assessment of their compatibility. This is important since the SR observations were taken at approximately 0900 and 2100 local times, while the TIROS-N data alternate between 0730-1930 and 0300-1500 local times. In addition, there is a period of overlap between the TIROS-N data and the broad band (5–50 μm) Nimbus 7 EArth radiation budget data. A comparison of those two data sets indiciate excellent agreement generally within about 1–2 Wm−2 on the monthly means on global and hemispherical scales. Comparisons of zonal averages indicate maximum differences as large as 9 Wm−2.

The earth radiation budget as determined from the ERB experiment aboard the NIMBUS 7 polar‐orbiting satellite is presented in the form of time‐latitude cross sections, hemispherically and globally averaged time plots, and annual global averages for the time period spanning November 1978 through October 1979. Comparisons are made between results derived from the fixed wide field‐of‐view (WFOV) radiometers and those derived from the scanning narrow field‐of‐view (NFOV) radiometers. While there is excellent agreement in regard to the spatial and temporal variations, the absolute magnitudes differ. The NFOV yields outgoing longwave fluxes and albedos that are about 4W/m2 and 2.5% respectively, greater than those derived from the WFOV sensors. Also, limited simultaneous comparisons are made between ERB results and those from the AVHRR on the NOAA 7 operational satellite.