The Clouds and Radiative Swath (CRS) product contains one hour of
instantaneous Clouds and the Earth's Radiant Energy System (CERES) data for a
single scanner instrument. The CRS contains all of the CERES SSF product data.
For each CERES FOV on the SSF, the CRS also contains vertical flux profiles
evaluated at five levels in the atmosphere: the surface, 500 hPa,
200 hPa, 70 hPa, and TOA. These through-the-atmosphere fluxes are
computed by making two passes through a radiative transfer model. After an
initial pass through the model, the modeled TOA results are compared against
the CERES TOA results produced by the CERES inversion process and contained on
the SSF. Inputs to the model are adjusted accordingly, and a second pass is
made through the model. The results of the second, or constrained, pass are
more consistent with the CERES TOA values.
The CRS contains the following constrained vertical flux profiles for both
clear sky and total sky conditions evaluated at the surface, 500 hPa,
200 hPa, 70 hPa, and TOA, along with pristine and aerosol-free total
sky fluxes evaluated at the surface and the TOA. (Please note that the
aerosol-free total sky flux data are not available on the TRMM CRS granules.)
Pristine denotes a theoretical sky condition that is free of both aerosols and
clouds. Aerosol-free total sky denotes a theoretical sky condition that
includes clouds but is free of aerosols.
Longwave upward and downward.
Shortwave upward and downward.
Window channel upward and downward.
The initial flux profiles are not contained on the CRS; however, the
adjustments between the constrained and initial profiles for the following are
included for clear sky, total sky, pristine, and aerosol-free total sky
conditions:
Longwave upward at the surface and TOA, and downward at the surface.
Shortwave upward at the surface and TOA, and downward at the surface.
Window channel upward at the surface and TOA, and downward at the
surface.
The adjustments to the radiative transfer model input parameters between the
initial and the constrained passes are also contained on the CRS. These
parameters include:
Surface albedo and skin temperature.
Total column precipitable water and upper tropospheric relative humidity.
Aerosol optical depth.
Cloud optical depth, fractional area, and effective temperature.
Additional information about the format and content of the CRS can be found
in the CERES Data Products Catalog. The CRS Quality Summary briefly describes
the algorithms used for radiative transfer and constrainment (tuning), as well
as the data inputs.
The CERES Data Management Team and the Atmospheric Science Data Center
(ASDC) at Langley use a Sampling Strategy, a Production Strategy, and a
Configuration Code (CCode) to track versions of CERES primary data products. In
general, minor reprocessing changes are tracked by increasing the Configuration
Code while major reprocessing changes result in a new Production Strategy. The
Sampling Strategy identifies the satellite and instruments which aquired the
data in the product.
A summary of changes made to the CERES CRS product is shown in the following
tables.
A new ancillary data file was added for Aqua processing which
eliminates the use of the monthly MODIS aerosol map. This solved
infrequent problems caused by treatment of default data in MODIS
files.
Photosynthetically active radiation over surface values were modified
to include spectral weighting factors that convert the spectral band 7-10
(557.5 - 689.6nm) output to 400 - 700nm (CRS SDS 161).
Surface albedo retrievals were corrected for instances where the
associated MATCH value is less than 0.0001 to avoid division by zero.
The definition of surface albedo over cloudy-sky coast was modified to
use the SAH cloudy land albedo value from the monthly SSF-based surface
albedo history map for ocean coverage of less than 1% to correct
unrealistically large surface albedo values for cloudy-sky coastal FOVs.
The definition of surface albedo for clear-sky coast was modified to
use Zhonghai Jin's ocean look-up table value to correct the resulting
modeled TOA albedo that was larger than the CERES value for clear-sky coast.
Cloudy sky over snow surface albedo retrievals were modified to include
a more complex look-up table to account for the influence of more available
input parameters. Sulfate aerosol optical depth is used for the retrieval
model. Ocean surface albedo is assumed for out-of-range low retrieval and
Snow is assumed for out-of-range high retrieval.
The spectral shape in the UV region was modified to include revised
values for the closed shrubs, woody savanna, savanna, grassland, cropland,
crop mosaic, and tundra IGBP scene types.
The direct/diffuse definition for ice clouds was corrected to improve
the handling of the ice cloud forward scattering peak for the 2-stream
solver.
Time varying trace gas concentrations for CO2, CH4, and N2O were
included to account for trace gas increases that have been observed.
The water percentage thresholds to 20:99% were treated as coast for
surface albedo logic. FOVs that are mostly land (1:20%) are better served
by using the monthly SSF-based surface albedo history map than a water
percent weighted IGBP default surface albedo.
The Aqua Beta1 CRS data set was the first CRS data set produced from
Aqua data. This data set was produced using the same software and ancillary
input data sets as the Terra Edition2B CRS data set.
For FOVs where the MATCH data is the sole source of aerosol optical
depth information, the MATCH 0.55 mm data instead of the MATCH 0.63 mm data
will be applied in the Fu-Liou model. Using the wrong wavelength causes
constituents with extinction decreasing with wavelength (sulfate, water
soluble, soot) to have a reduced effect, and causes constituents that have
extinction increasing with wavelength (mineral dust, insoluble) to have an
increased effect.
The Langley Fu-Liou model was updated to add new Lacis dust aerosol
data for the aerosol scene type indexes 19-23 for 0.5mm, 1.0mm, 2.0mm,
4.0mm, and 8.0mm dust, respectively. The FLSA table was also modified
accordingly. The new dust properties are less absorbing than the earlier
(1996) version.
Aerosols are now allowed in the stratosphere above 15km, which allows
for full use of the MATCH aerosol profile data which is provided up to 1
hPa or ~50Km.
Modified interpretation of the ADMgeo parameter to take advantage of
new information added by the ADM group for the Terra Edition2B SSF
delivery. Default values are now clearer and new non-default data provided
information regarding the location of the centroid of the FOV in relation
to the microwave imager retrievals.
CRS Parameters Affected: Terra CRS 161-163, 172-183, 193-235
For FOVs where the MATCH data is the sole source of aerosol optical
depth information, the MATCH 0.55 mm data instead of the MATCH 0.63 mm data
will be applied in the Fu-Liou model. Using the wrong wavelength causes
constituents with extinction decreasing with wavelength (sulfate, water
soluble, soot) to have a reduced effect, and causes constituents that have
extinction increasing with wavelength (mineral dust, insoluble) to have an
increased effect.
The Langley Fu-Liou model was updated to add new Lacis dust aerosol
data for the aerosol scene type indexes 19-23 for 0.5mm, 1.0mm, 2.0mm,
4.0mm, and 8.0mm dust, respectively. The FLSA table was also modified
accordingly. The new dust properties are less absorbing than the earlier
(1996) version.
Aerosols are now allowed in the stratosphere above 15km, which allows
for full use of the MATCH aerosol profile data which is provided up to 1
hPa or ~50Km.
Modified interpretation of the ADMgeo parameter to take advantage of
new information added by the ADM group for the Terra Edition2B SSF
delivery. Default values are now clearer and new non-default data provided
information regarding the location of the centroid of the FOV in relation
to the microwave imager retrievals.
CRS Parameters Affected: Terra CRS 161-163, 172-183, 193-235
The use of the Gridded Daily MODIS land angstrom exponent with the
0.55µm AOT was incorporated to produce a spectral AOT for desert
scene types. The angstrom exponent previously derived from the fit to the
three wavelengths for land given by the MOD08_d3 product produced large
negative (physically unrealistic) angstrom exponents in many
locations.
A new version of Fu-Liou radiative transfer model that includes a Gamma
Weighted Two-Stream Algorithm (GWTSA) SW code that deals with inhomogeneous
clouds was incorporated. The new model configuration is a more efficient,
one time computation of cloud and aerosol optical properties, necessary for
the more complex GWTSA solver.
The SW downward spectral weights for an adjustment of the initial
spectral albedo to match the retrieved TOA-based broadband surface albedo
was modified to include tables for desert and snow surfaces where spectral
insolation weights are different from those for low albedo surfaces. This
corrected for significant differences at low sun angles.
The definition for out of range cloudy sky TOA-based retrievals was
updated to default to the broadband surface albedo and spectral shape of
the sea ice. The previous approach of defaulting to the ocean broadband
surface albedo and spectral shape was incorrect.
The surface properties algorithm was updated to treat sea ice coverage
over the range of 0 to 100 percent. Previously, the ocean albedo algorithm
was only called when the ocean area coverage was greater than 50
percent.
The spectral emissivity for desert and open shrub scene types for the
10-11µm and 11-12µm Fu-Liou bands was revised to reflect the
yearly scene type mean of the Cloud WG ISCCP-based emissivity maps to
produce more consistent results between Clouds and SARB.
The software was modified to process FOVs for which the CERES Observed
SW TOA is bad but the CERES Observed LW TOA is good through the radiative
transfer model. The increased number of processed FOVs provides more LW
results for analysis.
The SSF ADMgeo parameter was included in the logic that adjusts the
IGBP scene vector when the cloud coverage is greater than 95 percent to be
consistent with the Cloud WG retrieval assumption of cloud properties over
a snow or ice surface. The Instantaneous SARB logic uses the IGBP scene
vector to decide the surface spectral albedo and emissivity as well as the
mode of obtaining the broadband surface albedo.
The look-up table values for fresh snow and permanent snow surface
albedo used in the computation of surface albedo were modified to include
values for different snow grain sizes (50µm for fresh snow and
1000µm for permanent snow).
The diffuse angle for cloudy scenes was corrected from 60 degrees to 53
degrees.
The ocean surface albedo lookup table was updated. The new table values
are based on improved ocean optics data (sea water absorption data from
Pope and Fry (1997) and parameterizations for the optical properties of
Phytoplankton particles based on Morel and Mariterena (2001)).
SARB SDS 75, Sigma table version number, was redefined as FuLiou model
error code. SARB SDS 75 now indicates the error status returned from the
radiative transfer algorithm. The new SDS is the same type as the old SDS.
(CERES SCCR #498)
Use of the GFDL aerosol climatology was replaced with the use of a new
MATCH-based climatology that varies with month. The MATCH-based climatology
is only used if there is no daily MATCH data. The proportion of absorbing
aerosol over the Northern Polar regions was too large in the GFDL
climatology.
The cloudy-sky over snow albedo retrieval algorithms were modified to
correctly use the snow/ice percentage flag provided on the SSF input
product.
Corrections were made to the use of aerosol optical thickness over land
from the backup source, the MODIS MOD08-based Interpolated Daily Maps.
Previous use resulted in invalid OLR values.
Aerosol-free total sky flux profile data at the surface and the TOA
were added to the CRS product.
Two new sources for aerosol optical thickness data were incorporated
into the CRS product. The first is an instantaneous aerosol optical
thickness data set based on the MODIS MOD03 product and the second new
source is aerosol optical thickness over land data from the MODIS
MOD08-based Interpolated Daily Map product.
Algorithms for retrieving surface albedo over snow conditions were
incorporated.
The modified version of the Fu-Liou model used by the CERES SARB
Working Group was modified to include the Hitran2000 SW absorption.
No changes were made to the SARB algorithms from those used for the
TRMM-PFM-VIRS_Edition2B data set.
Software errors encountered when converting from a binary format to an
HDF format were corrected. The parameters affected include the CERES
Observed TOA and surface fluxes, the number of levels included in the
vertical profiles, and the aerosol constituency flags. In the
TRMM-PFM-VIRS_Edition2B data set these parameters were erroneously defined
according to the CERES default values.
The limit for the allowable sunglint percentage per FOV was increased
from zero to 90%, allowing more FOVs to be processed through the SARB
algorithms.
The SARB Constrainment algorithm was modified to "freeze"
cloud parameters for skies that are less than 5% cloudy.
New water spectral surface albedo look up table values were
incorporated.
A new ocean spectral surface albedo look up table, the result of a
discrete ordinate model with coupled ocean and atmosphere optics, was
incorporated.
To improve accuracy of the Outgoing Longwave Radiation (OLR) results
over hot surfaces, the radiative transfer model was modified to include
two bands in the thermal IR/Solar transition region to cover wavelengths
2200 to 2850 cm-1.
The water vapor continuum parameterization was updated from CKD 2.1 to
CKD 2.4. CKD2.4 is more transparent in the 400 to 1000 cm-1 wavelength
range, leading to increased OLR by approximately 1 Wm-2.
A bug in previous CRS results for ice clouds was corrected. The ice
particle diameter is now converted from the mean effective diameter (De)
obtained from the input SSF product to a generalized effective diameter
(Dge) that is required by the Fu-Liou radiative transfer model.
An inconsistency between cloud height and temperature between the
initial and constrained passes was corrected by constraining to the cloud
top temperature instead of to the cloud effective temperature.
Scene-dependent spectral curves for wavelengths greater than 1.5
microns were modified for consistency with results from MODIS, which
showed a lower surface reflectance than that which SARB had been using.
Instead of calculating vertical flux profile values for the TOA at 1.0
hPa, modeled TOA fluxes are now calculated at 0.1 hPa.
Due to the advances in the TRMM ADMs that yield more accurate
instantaneous CERES TOA flux values, the sigma values used in the
constrainment process were modified so that the modeled TOA fluxes are
more tightly constrained to the Total flux provided on the SSF product,
and less tightly to the radiances and window channel flux also provided
as input on the SSF.
Use of a monthly surface albedo history product was added.
Access to a climatology for the total aerosol optical depth whenever
such data were unavailable from the SSF input product was added. The
aerosol data provided by either the SSF or the climatology were divided
into multiple aerosol scene-dependent constituencies, with constituency
scale heights and percent ratios obtained through the climatology.
The archived vertical flux profiles for clear and total sky
conditions were expanded to include a fifth level at 200 hPa.
Pristine fluxes at the surface and TOA were added.
Charlock, T. P., and T. L. Alberta, 1996: The CERES/ARM/GEWEX
Experiment (CAGEX) for the retrieval of radiative fluxes with satellite data.
Bull. Amer. Meteor. Soc., 77, 2673-2683.
Clouds and the Earth's Radiant Energy System (CERES) Algorithm
Theoretical Basis Document, Compute Surface and Atmospheric Fluxes
(System 5.0), Release 2.2, June 2, 1997.
Clouds and the Earth's Radiant Energy System (CERES) Data Management
System Data Products Catalog Release 3, Version 2, August 2001.
Clouds and the Earth's Radiant Energy System (CERES) Validation
Document, Surface and Atmospheric Radiation Budget (SARB) Validation Plan for
CERES Subsystem 5.0 (Compute Surface and Atmospheric Fluxes), Release 4.0,
October 2000.
Collins, W.D., P.J.Rasch, B.E.Eaton, B.V.Khattatov, J-F.Lamarque, and
C.S.Zender, 2001: Simulating Aerosols Using a Chemical Transport Model With
Assimilation of Satellite Aerosol Retrievals: Methodology for INDOEX.
Journal Geophysical Research, Volume 106, 7313-7336.
Fu, Q. and K.N.Liou, 1993: Parameterization of the Radiative Properties
of Cirrus Clouds. Journal of Atmospheric Science, 50, 2000-2025.
HDF User's Guide, NASA Langley Atmospheric Science Data Center,
Hierarchical Data Format Web Site, (from NCSA) Version 4.0, February 1996.
Rose, F., T. Charlock, D, Rutan, and G. L. Smith, 1997: Tests of a
constrainment algorithm for the surface and atmospheric radiation budget.
Proceedings of the Ninth Conference on Atmospheric Radiation, Long Beach (Feb.
2-7, 1997), AMS, 466-469.
Rutan, D., and T. Charlock, 1997: Spectral reflectance, directional
reflectance, and broadband albedo of the earth's surface. Proceedings of the
Ninth Conference on Atmospheric Radiation, Long Beach (Feb. 2-7, 1997), AMS,
466-469.
Wielicki, B.A., B.R.Barkstrom, E.F.Harrison, R.B.Lee, G.L.Smith, and
J.E.Cooper, 1996: Clouds aand the Earth's Radiant Energy System (CERES): An
Earth Observing System Experiment. Bullitin American Meteorological
Society, 77, 853-868.
Dr. Bruce A. Wielicki
CERES Interdisciplinary Principal Investigator
Atmospheric Sciences Research Building 1250
NASA Langley Research Center
Hampton, Virginia 23681-2199
E-mail: b.a.wielicki@nasa.gov
Technical Contact:
Dr. Thomas P. Charlock, SARB Working Group Chair
Atmospheric Sciences Research Building 1250
NASA Langley Research Center
Hampton, Virginia 23681-2199
E-mail: thomas.p.charlock@nasa.gov
Author/Data Center:
Atmospheric Science Data Center
User and Data Services Office
Mail Stop 157D
NASA Langley Research Center
Hampton, Virginia 23681-2199
USA
Telephone: (757) 864-8656
FAX: (757)864-8807
E-mail: larc@eos.nasa.gov
URL: http://eosweb.larc.nasa.gov
The requested form of acknowledgment for any publication in which these
data are used is:
"These data were obtained from the NASA Langley Research Center
Atmospheric Science Data Center."
The Langley Data Center requests a reprint of any published papers or
reports or a brief description of other uses (e.g., posters, oral presentations,
etc.) of data that we have distributed. This will help the Data Center determine
the use of data distributed, which is helpful in optimizing product development.
It also helps us to keep our product related references current.
Reference:The CERES Team has gone to considerable
trouble to remove major errors and to verify the quality and accuracy of these
data. Please provide a reference to the following paper when you publish
scientific results with the CERES data:
Wielicki, B. A., B. R. Barkstrom, E. F. Harrison, R. B. Lee III, G. L. Smith,
and J. E. Cooper, "Clouds and the Earth's Radiant Energy System (CERES):
An Earth Observing System Experiment," Bull. Amer. Meteor. Soc.,
77, 853-868, 1996.
Web Page Information:
Document Creation Date: August 28, 2001 Last Date Modified: Jan 23, 2002; Dec 3, 2003; Mar 15, 2004;
Sep 21, 2004; Jul 6, 2005; Sep 19, 2006; Oct 18, 2007; Aug 28, 2008 Review Date: August 2008 Author: User and Data Services Office, ASDC ASDC Help Desk: Phone (757) 864-8656; E-mail
larc@eos.nasa.gov URL:
http://eosweb.larc.nasa.gov/GUIDE/dataset_documents/cer_crs.html
