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Here, one can plot CERES/SARB validation results. Radiation transfer model runs at CERES footprint resolution (archived in the CERES CRS data product CRS - defined ) are compared to observed SW and LW fluxes at the surface and TOA. Footprints fall within 15km and 7 minutes of surface observations. Surface SW & LW results are ploted along with tables of statistics as shown in the example below.
Plot Pages
Footprint
Validation
Monthly Mean
Time Series
Surface Data
Cloud Fraction
FSW Plots
Statistics
 
 
CRS vs SFC Obs Validation Tables
Surface
Site(s)
click here for list of sites
Date
Year
Month
Untuned (ut)
or Tuned (tu)
CRS Edition
2B (latest) or 2A
Available CERES/CRS SARB Results Compared to CAVE Observations
TRMM Edition 2C CAVE Validation Sites (CVS) for Jan-Aug 1998
Terra Edition 2A CAVE Validation Sites (CVS) for Mar-Oct 2000
Terra Edition 2B CAVE Validation Sites (CVS) for Jan-Dec 2001
5 Year Terra Record Terra Time Series (TTS) for Jan-Dec 2001 

Here's how to decode the tables.

LW Dn Sfc = Broadband longwave (thermal IR) downward at surface
LW Up Sfc = Broadband longwave (thermal IR) upward at surface
            Observations are from pyrgeometers

SW Dn Sfc = Broadband shortwave (solar) downward at surface
            Observations from pyrheliometer plus shaded pyranometer

SW Up Sfc = Broadband shortwave (solar) upward at surface
            Observations from pyranometer

LW Up TOA = Outgoing Longwave Radiation (OLR)
SW Up TOA = Reflected Shortwave Flux
            Observations from CERES broadband instruments processed
            by the advanced SSF method (i.e., better than ES8 ERBE-like)

Obs Mean = Observed flux in Wm-2

      Surface observations are 15 minute means.  CERES observations
      and SARB/CRS products are instantaneous.  SW observations at
      the surface have been adjusted to correspond to the solar
      zenith angle (SZA) of the satellite observation.

               a = cos(SZAsatellite)

               b = cos(SZAeachminute)

               c = 15 minute mean of b

               adjusted sfc obs flux = (sfc obs flux)*a/c


      LW was computed and observed for day and night footprints.
      SW was computed and observed for daytime footprints only.
      To estimate a 24 hour mean SW flux or bias from the tables,
      divide each SW flux or bias by 2.


N = number of samples

Bias = SARB/CRS product minus Observations

Std Dev = standard deviation

RMS = root mean square difference of SARB/CRS product and observations

Mod Frc All-Clr = Model (SARB/CRS product) cloud forcing as difference of
             computed all sky flux (available for all footprints)
             and computed clear sky flux (available for all footprints)

Forcing All-CNA= Aerosol forcing as the difference of
             computed all sky flux (including clouds & aerosols)
             and computed cloudy sky flux (Includes clouds but NO aerosols)

Dif Bias Obs-CRS = Bias (Observations - SARB/CRS product)
             of the diffuse downwelling SW (Tuned results only)

AOT Frc Clr-Prs= Aerosol forcing as the difference of
             computed clear sky flux (including aerosols)
             and computed pristine flux (clear sky with NO aerosols)

All Sky = all available CERES fooprints (commonly 15-40 km)

Clear Sky VIRS = CERES footprints identified as clear using
                 high resolution VIRS imager pixels (~1 km)

Clear Sky VIRS & L/AA = CERES footprints identified as clear using both
                 high resolution VIRS imager pixels (~1 km)
                 AND a minute-by-minute time series analysis
                 of surface pyranometer data as per the
                 Long and Ackerman algorithm

Overcast VIRS = CERES footprints identified as overcast using
                 high resolution VIRS imager pixels (~1 km)

Overcast VIRS & L/AA = CERES footprints identified as overcast using both
                 high resolution VIRS imager pixels (~1 km)
                 AND a minute-by-minute time series analysis
                 of surface pyranometer data as per the
                 Long and Ackerman algorithm

Accuracy

The following table shows desired surface flux accuracies from BSRN: From Ohmura et al., 1998

Quantity at Surface Capability
Direct solar irradiance 2 Wm-2
Diffuse solar radiation 5 Wm-2
Global (SW) radiation 5 Wm-2
Downwelling longwave radiation 10 Wm-2
Ohmura, A., E. Dutton, B. Forgan, C. Frohlich, H. Gilgen, H. Hegne, A. Heimo, G. Konig-Langlo, B. McArthur, G. Muller, R. Philipona, C. Whitlock, K. Dehne, and M. Wild, 1998: Baseline Surface Radiation Network (BSRN/WCRP): New precision radiometery for climate change research. Bull. Amer. Meteor. Soc. 79 No. 10, 2115-2136.

Accuracies specified by BSRN in the Longwave region are seen as overly pessimistic as pointed out in Charlock et al. 2001. This is also found in the statistics tables above in model to observation comparisons.
Responsible NASA Official: Dr. Thomas Charlock
Data/Web Questions:David Rutan
Last Updated: 2008/05/02

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