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Bruce R. Barkstrom

Abstract

In standard treatments of the mass and energy budget of cloud droplets, radiant energy transfer is neglected on the grounds that the temperature difference between the droplet and its surroundings is small. This paper includes the effect of radiant heating and cooling of droplets by using the Eddington approximation for the solution of the radiative transfer equation. Although the calculation assumes that the cloud is isothermal and has a constant size spectrum with altitude, the heating or cooling of droplets by radiation changes the growth rate of the droplets very significantly. At the top of a cloud with a base at 2500 m and a top at 3000 m, a droplet will grow from 9.5 to 10.5 µm in about 4 min, assuming a supersaturation ratio of 1.0013. Such a growth rate is more than 20 times the growth rate for condensation alone, and may be expected to have a significant impact on estimates of precipitation formation, as well as droplet spectrum calculations.

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Bruce R. Barkstrom

The Earth Radiation Budget Experiment (ERBE) is the first multisatellite system designed to measure the Earth's radiation budget. It will fly on a low-inclination NASA satellite and two Sun-synchronous NOAA satellites during the mid-1980s. Each satellite will carry two instrument packages—a scanner and a nonscanner—each package containing a complete, traceable system for inflight calibration. The nonscanner package has four Earth-viewing channels, as well as a solar monitor similar to that flown on the Solar Max Mission. The nonscanner detectors are the first Earth-viewing active cavity radiometers. The scanner package contains three thermistor bolometers which scan the Earth perpendicular to the orbital track.

The data from the satellite radiometers will be brought to the top of the atmosphere using a pixel-by-pixel process for the scanner data and a numerical filter for the nonscanner. The inversion will use angular directional models based on the Nimbus 7 ERB instruments, selecting the appropriate model for cloud conditions from the ERBE scanner data. After the measurements have been brought to the top of the atmosphere, they will be averaged over time to produce monthly averages. In averaging, allowance will be made for meteorological variations, as well as albedo variations with solar zenith angle. These new features are expected to provide a substantial improvement in the accuracy of the radiation budget on regional as well as global scales. This paper also provides a brief description of the implementation of the ERBE Project, including the ERBE Science Team.

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Bryan A. Baum
and
Bruce R. Barkstrom

The Earth Observing System (EOS) will collect data from a large number of satellite-borne instruments, beginning later in this decade. To make data accessible to the scientific community, NASA will build an EOS Data and Information System (EOSDIS). As an initial effort to accelerate the development of EOSDIS and to gain experience with such an information system, NASA and other agencies are working on a prototype system called Version 0 (VO). This effort will provide improved access to pre-EOS earth science data throughout the early EOSDIS period. Based on recommendations from the EOSDIS Science Advisory Panel, EOSDIS will have several distributed active archive centers (DAACs). Each DAAC will specialize in particular datasets. This paper describes work at the NASA Langley Research Center's (LaRC) DAAC.

The Version 0 Langley DAAC began archiving and distributing existing datasets pertaining to the earth's radiation budget, clouds, aerosols, and tropospheric chemistry in late 1992. The primary goals of the LaRC VO effort are the following:

  1. Enhance scientific use of existing data;

  2. Develop institutional expertise in maintaining and distributing data;

  3. Use institutional capability for processing data from previous missions such as the Earth Radiation Budget Experiment and the Stratospheric Aerosol and Gas Experiment to prepare for processing future EOS satellite data;

  4. Encourage cooperative interagency and international involvement with datasets and research;

  5. Incorporate technological hardware and software advances quickly.

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Craig R. Burfeind
,
James A. Weinman
, and
Bruce R. Barkstrom

Abstract

This study has applied computerized pattern analysis techniques to the location and classification of feature of several mature extratropical cyclones that were depicted in GOES satellite images. These features include the location of the center of the cyclone vortex core and the location of the associated occluded front. The cyclone type was classified in accord with the scheme of Troup and Streten. The present analysis was implemented on a personal computer, results were obtained within approximately one or two minutes without the intervention of an analyst.

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Kenneth R. Knapp
,
John J. Bates
, and
Bruce Barkstrom
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Bruce A. Wielicki
,
Bruce R. Barkstrom
,
Edwin F. Harrison
,
Robert B. Lee III
,
G. Louis Smith
, and
John E. Cooper

Clouds and the Earth's Radiant Energy System (CERES) is an investigation to examine the role of cloud/radiation feedback in the Earth's climate system. The CERES broadband scanning radiometers are an improved version of the Earth Radiation Budget Experiment (ERBE) radiometers. The CERES instruments will fly on several National Aeronautics and Space Administration Earth Observing System (EOS) satellites starting in 1998 and extending over at least 15 years. The CERES science investigations will provide data to extend the ERBE climate record of top-of-atmosphere shortwave (SW) and longwave (LW) radiative fluxes. CERES will also combine simultaneous cloud property data derived using EOS narrowband imagers to provide a consistent set of cloud/radiation data, including SW and LW radiative fluxes at the surface and at several selected levels within the atmosphere. CERES data are expected to provide top-of-atmosphere radiative fluxes with a factor of 2 to 3 less error than the ERBE data. Estimates of radiative fluxes at the surface and especially within the atmosphere will be a much greater challenge but should also show significant improvements over current capabilities.

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G. Louis Smith
,
D. K. Pandey
,
Robert B. Lee III
,
Bruce R. Barkstrom
, and
Kory J. Priestley

Abstract

The Clouds and Earth Radiant Energy System (CERES) scanning radiometer was designed to provide high accuracy measurements of the radiances from the earth. Calibration testing of the instruments showed the presence of an undesired slow transient in the measurements of all channels at 1% to 2% of the signal. Analysis of the data showed that the transient consists of a single linear mode. The characteristic time of this mode is 0.3 to 0.4 s and is much greater than that the 8–10-ms response time of the detector, so that it is well separated from the detector response. A numerical filter was designed for the removal of this transient from the measurements. Results show no trace remaining of the transient after application of the numerical filter. The characterization of the slow mode on the basis of ground calibration data is discussed and flight results are shown for the CERES instruments aboard the Tropical Rainfall Measurement Mission and Terra spacecraft. The primary influence of the slow mode is in the calibration of the instrument and the in-flight validation of the calibration. This method may be applicable to other radiometers that are striving for high accuracy and encounter a slow spurious mode, regardless of the underlying physics.

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Robert B. Lee III
,
Bruce R. Barkstrom
,
G. Louis Smith
,
John E. Cooper
,
Leonard P. Kopia
,
R. Wes Lawrence
,
Susan Thomas
,
Dhirendra K. Pandey
, and
Dominique A. H. Crommelynck

Abstract

The Clouds and the Earth's Radiant Energy System (CERES) spacecraft sensors are designed to measure broadband earth-reflected solar shortwave (0.3–5 µm) and earth-emitted longwave (5– > 100 µm) radiances at the top of the atmosphere as part of the Mission to Planet Earth program. The scanning thermistor bolometer sensors respond to radiances in the broadband shortwave (0.3–5 µm) and total-wave (0.3– > 100 µm) spectral regions, as well as to radiances in the narrowband water vapor window (8–12 µm) region. The sensors are designed to operate for a minimum of 5 years aboard the NASA Tropical Rainfall Measuring Mission and Earth Observing System AM-I spacecraft platforms that are scheduled for launches in 1997 and 1998, respectively. The flight sensors and the in-flight calibration systems will he calibrated in a vacuum ground facility using reference radiance sources, tied to the international temperature scale of 1990. The calibrations will be used to derive sensor gains, offsets, spectral responses, and point spread functions within and outside of the field of view. The shortwave, total-wave, and window ground calibration accuracy requirements (1 sigma) are ±0.8, ±0.6, and ±0.3 W m−2 sr−1, respectively, while the corresponding measurement precisions are ±0.5% and ±1.0% for the broadband longwave and shortwave radiances, respectively. The CERES sensors, in-flight calibration systems, and ground calibration instrumentation are described along with outlines of the preflight and in-flight calibration approaches.

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Kory J. Priestley
,
Bruce R. Barkstrom
,
Robert B. Lee III
,
Richard N. Green
,
Susan Thomas
,
Robert S. Wilson
,
Peter L. Spence
,
Jack Paden
,
D. K. Pandey
, and
Aiman Al-Hajjah

Abstract

Each Clouds and the Earth’s Radiant Energy System (CERES) instrument contains three scanning thermistor bolometer radiometric channels. These channels measure broadband radiances in the shortwave (0.3–5.0 μm), total (0.3–>100 μm), and water vapor window regions (8–12 μm). Ground-based radiometric calibrations of the CERES flight models were conducted by TRW Inc.’s Space and Electronics Group of Redondo Beach, California. On-orbit calibration and vicarious validation studies have demonstrated radiometric stability, defined as long-term repeatability when measuring a constant source, at better than 0.2% for the first 18 months of science data collection. This level exceeds by 2.5 to 5 times the prelaunch radiometric performance goals that were set at the 0.5% level for terrestrial energy flows and 1.0% for solar energy flows by the CERES Science Team. The current effort describes the radiometric performance of the CERES Proto-Flight Model on the Tropical Rainfall Measuring Mission spacecraft over the first 19 months of scientific data collection.

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