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  • Author or Editor: Frederick M. Denn x
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Takmeng Wong
,
Edwin F. Harrison
,
Gary G. Gibson
, and
Frederick M. Denn

Abstract

Clouds and the Earth’s Radiant Energy System (CERES) is a NASA spaceborne measurement program for monitoring the radiation environment of the earth–atmosphere system. The first CERES instrument is scheduled to be launched on board the Tropical Rainfall Measuring Mission (TRMM) satellite in late 1997. In addition to gathering traditional cross-track fixed azimuth measurements for calculating monthly mean radiation fields, this single CERES scanner instrument will also be required to collect angular radiance data using a rotating azimuth configuration for developing new angular dependence models (ADMs). Since the TRMM single CERES instrument can only be run in either one of these two configurations at any one time, it will need to be operated in a cyclical pattern between these two scan modes to achieve the intended measurement goals. To minimize the errors in the derived monthly mean radiation field due to missing cross-track scanner measurements during this satellite mission, determination of the optimal scan mode sequence for the TRMM single CERES instrument is carried out. The Earth Radiation Budget Experiment S-4 daily mean cross-track scanner data product for April and July 1985 and January 1986 is used with a simple temporal sampling scheme to produce simulated daily mean cross-track scanner measurements under different TRMM CERES operational scan mode sequences. Error analysis is performed on the monthly mean radiation fields derived from these simulated datasets. It is found that the best monthly mean result occurred when the cross-track scanner is operated on a “2 days on and 1 day off” mode. This scan mode sequence will effectively allow for 2 consecutive days of cross-track scanner data and 1 day of angular radiance measurement for each 3-day period. The root-mean-square errors for the monthly mean all-sky (clear sky) longwave and shortwave radiation field, due to missing cross-track scanner measurements for this particular case, are expected to be less than 2.5 (0.5) and 5.0 (1.5) W m−2, respectively.

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Edwin F. Harrison
,
David R. Brooks
,
Patrick Minnis
,
Bruce A. Wielicki
,
W. Frank Staylor
,
Gary G. Gibson
,
David F. Young
,
Frederick M. Denn
, and
the ERBE Science Team3

First results for diurnal cycles derived from the Earth Radiation Budget Experiment (ERBE) are presented for the combined Earth Radiation Budget Satellite (ERBS) and NOAA-9 spacecraft for April 1985. Regional scale longwave (LW) radiation data are analyzed to determine diurnal variations for the total scene (including clouds) and for clear-sky conditions. The LW diurnal range was found to be greatest for clear desert regions (up to about 70 W · m−2) and smallest for clear oceans (less than 5 W · m−2). Local time of maximum longwave radiation occurs at a wide range of times throughout the day and night over oceans, but generally occurs from noon to early afternoon over land and desert regions.

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Charles K. Rutledge
,
Gregory L. Schuster
,
Thomas P. Charlock
,
Frederick M. Denn
,
William L. Smith Jr.
,
Bryan E. Fabbri
,
James J. Madigan Jr.
, and
Robert J. Knapp

When radiometers on satellites point toward Earth with the goal of sensing an important variable quantitatively, rather than just creating a pleasing image, the task at hand is often not simple. The electromagnetic energy detected by the radiometers is a puzzle of various signals; it must be solved to quantify the specific physical variable. This task, called the retrieval or remote-sensing process, is important to most satellite-based observation programs. It would be ideal to test the algorithms for retrieval processes in a sealed laboratory, where all the relevant parameters could be easily measured. The size and complexity of the Earth make this impractical. NASA's Clouds and the Earth's Radiant Energy System (CERES) project has done the next-best thing by developing a long-term radiation observation site over the ocean. The relatively low and homogeneous surface albedo of the ocean make this type of site a simpler environment for observing and validating radiation parameters from satellite-based instruments. To characterize components of the planet's energy budget, CERES uses a variety of retrievals associated with several satellite-based instruments onboard NASA's Earth Observing System (EOS). A new surface observation project called the CERES Ocean Validation Experiment (COVE), operating on a rigid ocean platform, is supplying data to validate some of these instruments and retrieval products. This article describes the ocean platform and the types of observations being performed there, and highlights of some scientific problems being addressed.

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