ISSN:0148-0227    

DOI:10.1029/JD089iD04p04967

年代:1984

数据来源: WILEY

摘要:

Three NIMBUS 7 CZCS chlorophyll images of the southern Benguela Current region off the west coast of South Africa on February 9, 13, and 15, 1980, during a surface truth experiment in the area are evaluated in the light of a time series of airborne radiation thermometry and wind data for this period, and the validity of CZCS chlorophyll estimates for the region is discussed. There was good agreement between upwelling and relaxation in the system and changes in the distribution of chlorophyll. The development of upwelling tongues with the subsequent increase in chlorophyll concentrations and the intensification of the oceanic front off capes was evident. An S‐shaped band of high chlorophyll was present well offshore of the Orange River mouth and lends support to the existence of a divergence zone at the shelf break in the area, there being fair agreement between satellite buoy tracks, topography, and the position of the oceanic color front. Areas of elevated chlorophyll were evident in two bays on the south coast on February 13, 1980, and these are ascribed to an earlier upwelling event in the region. Implications for future work in the area are discusse

ISSN:0148-0227    

DOI:10.1029/JD089iD04p04968

年代:1984

数据来源: WILEY

摘要:

Different spectral signatures of coastal waters are presented and analysed with respect to possible improvements of the CZCS algorithms. When adjusted to the prevailing oceanographic conditions, algorithms can be improved in different ways: by adjustment of the coefficients in the ratio algorithms, by use of the amplitude of reflectance, or by adjustment of the method for the aerosol correction. It is shown that the combined use of ratio and amplitude of reflectance in a sediment algorithm can be used to distinguish between offshore upwellings and turbid near shore coastal water. The processing of CZCS scenes illustrates the importance of ocean color imagery in various aspects of oceanography: fundamental biology and transport of coastal pollutants.

ISSN:0148-0227    

DOI:10.1029/JD089iD04p04977

年代:1984

数据来源: WILEY

摘要:

Data from the scanning channels of the NIMBUS 7 Earth Radiation Budget (ERB) experiment are combined with other data on earth surface conditions and cloudiness. Patterns of bi‐directional reflectance are constructed from this data for uniform earth and cloud surfaces. Examples are shown that illustrate the bi‐directional properties of surfaces and how these properties vary with solar zenith angle (SZA). Dependence of albedo on SZA is also shown. Conclusions may be summarized as follows: (1) Water surfaces exhibit limb brightening at all SZAs; (2) cloud and land surfaces change from limb darkening to brightening as SZA increases; (3) the land surface exhibits higher backward reflection for SZAs less than about 50°; (4) all of the surfaces in this study become more specular as SZA increases; (5) snow is the most nearly isotropic of these surfaces; (6) snow albedo shows very little variation with SZA and even shows a slight decrease over a limited range; (7) albedo generally increases with increasing SZA for other than snow surfaces; (8) angular patterns for high water and ice clouds are quite similar, but ice clouds are more nearly isotropic; (9) the angular patterns developed in this study are in qualitative agreement with those from other investigat

ISSN:0148-0227    

DOI:10.1029/JD089iD04p04987

年代:1984

数据来源: WILEY

摘要:

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/m2and 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 operationa

ISSN:0148-0227    

DOI:10.1029/JD089iD04p04997

年代:1984

数据来源: WILEY

摘要:

Earth Radiation Budget (ERB) experiments on board the NIMBUS 6 (ERB 6) and NIMBUS 7 (ERB 7) spacecraft have measured wide‐field‐of‐view (WFOV) total (0.2 to 50 μm), shortwave (0.2 to 3.8 μm), and near‐infrared (0.7 to 2.8 μm) terrestrial irradiances for a joint lifetime of over 8 years. Though the spectral characteristics of both experiments are nearly identical, instrument degradation and altitude differences introduce discrepancies between the two data sets. ERB parameters from these two observing platforms may be combined into a scientifically meaningful data set only after these discrepancies are eliminated. To facilitate the creation of a long‐term ERB data set, comparisons of the ERB 6 experiment irradiances with, and calibrations adjustments with respect to, the corresponding ERB 7 irradiances have been performed. Two calibration methods were developed and applied to the irradiance data from 28 pairs of collocated orbits. The differential effects of altitude, illumination, albedo, and scene inhomogeneities were applied. The result is a set of calibration adjustments that adjust the ERB 6 data to match th

ISSN:0148-0227    

DOI:10.1029/JD089iD04p05011

年代:1984

数据来源: WILEY

摘要:

The development of ERB observational systems is traced from its beginnings in the late 1950's through to the current ERB on the NIMBUS 7 satellite. The instruments comprising the current 22‐channel ERB experiment are described in some detail. Noteworthy are the inclusion in one solar channel, of a self‐calibrating cavity to measure the solar constant and the use of biaxial scanning telescopes to determine the angular reflection and emission model required for processing the narrow‐angle radiometric data. A fairly detailed description of the prelaunch and in‐flight calibrations is given along with an analysis of the radiometric performance of the instruments. The data processing system is traced with the aid of a schematic flow diagram showing the steps required to produce the many tape and microfilm products archived. Future plans for improving the quality and accuracy of the data products are discussed. Finally, the upcoming Earth Radiation Budget Experiment (ERBE) is briefly mentioned. It will be capable of simultaneously measuring the radiation budget from three satellites, each having a different equator crossing time an

ISSN:0148-0227    

DOI:10.1029/JD089iD04p05021

年代:1984

数据来源: WILEY

摘要:

Shortwave reflected terrestrial irradiance is routinely measured at satellite altitude by wide field‐of‐view radiometers on board earth radiation budget experiments. Although these irradiances are then corrected for time‐dependent variations in mean filter‐dome transmissivity, asymmetries in the amount of degradation over the filter dome hemisphere have the potential of producing large biases in the estimated irradiance field when positively or negatively correlated with inhomogeneities in the incident radiance field. The extent of this asymmetry, caused by the combination of instrument configuration and contamination, direct and diffuse solar radiation and contact with exospheric constituents, is obtained empirically for the radiometer on board the NIMBUS 7 spacecraft during the first data year. Further analysis assesses the impact of this phenomenon on earth radiation budget parameter measu

ISSN:0148-0227    

DOI:10.1029/JD089iD04p05039

年代:1984

数据来源: WILEY

摘要:

Detailed characterizations of flight spare earth flux sensors from the NIMBUS Earth Radiation Budget (ERB) program have been performed which, when coupled with a more careful accounting of the orbital instrument environment, provide the potential for improved accuracy in the final data products. The characterizations included detailed field‐of‐view mappings, responses to transient long and short wavelength radiation, and response to sensor temperature changes. These sensor and environment characterizations, along with the outstanding low noise and stability properties of the ERB instrument signal processing system, promise improvement of the data accuracy to levels sufficient for long‐term budget and climatological purposes. The combined data sets from NIMBUS 6 and 7 are expected to span a period in excess of 10 years. The improvements in data accuracy are particularly significant over zonal latitude bands because the corrections are strongly latitude depe

ISSN:0148-0227    

DOI:10.1029/JD089iD04p05049

年代:1984

数据来源: WILEY

摘要:

The in‐flight space environment of the NIMBUS 6 and 7 earth radiation budget instrument differs in many important ways from the steady state preflight laboratory calibration environment. Because of this, the first 20 months of NIMBUS 7 wide field of view (WFOV) channels had their calibration adjusted through a comparison with the in‐flight calibrated longwave scanner data. The adjustments were most important for the reflected solar radiation channel 13. The scanner failed on June 22, 1980, leading to the requirement for new algorithms to process the remainder of the WFOV data set. On the basis of detailed studies of the sensor characteristics, in‐flight calibration adjustments of the WFOV channels are developed which account for the major thermal, chemical, and radiative dynamics of the orbital environment. These adjustments correct for (1) long‐term changes in the rsponse of the sensors; (2) thermal transients due to the instrument's on‐off duty cycle, and (3) absorption of longwave radiation by the filter domes. In addition, these studies have led to improved in‐flight calibration adjustments for channel 12, the broadband total irradiance sensor. The rational behind the new algorithm is described, and differences between the new and old algorithms ar

ISSN:0148-0227    

DOI:10.1029/JD089iD04p05057

年代:1984

数据来源: WILEY