CERES/ARM Validation Experiment (CAVE)

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 Surface Obs Validation Tables CRS Edition E2b.terra E2b.aqua E2c.aqua E2b.trmm E2a.aqua E2a.terra Date Year 2000 2001 2002 2003 2004 2005 2006 Month All.MonthsJanFebMarAprMayJunJulAugSepOctNovDec Surface Site(s) All During Terra (TTS)Select Sites (CVS)All Available ARM/SGP E13ARM/SGP E02ARM/SGP E16 ARM/SGP E18ARM/TWP ManusARM/TWP Nauru GMD BondvilleGMD Dsrt RockGMD Ft Peck GMD Gdwn CreekGMD Penn StGMD Tbl Mntn GMD BarrowGMD BermudaGMD Boulder Twr GMD KwajeleinGMD Mauna LoaGMD Samoa GMD S PoleBSRN Alc SpringsBSRN De Aar BSRN G Von NeumBSRN LauderBSRN Lindenberg BSRN Ny AlesundBSRN PayerneBSRN Sede Boqer BSRN SyowaBSRN TammanresetBSRN Tateno BSRN Saudi Sol VilChes Bay Lighthouse'WHOI Stratus Buoy WHOI NTAS BuoySGP GrpSURFRAD Grp Polar GrpIsland GrpDesert Grp Coastal GrpDesert GrpBSRN No Islands ARM/SGP E01ARM/SGP E03ARM/SGP E04 ARM/SGP E05ARM/SGP E06ARM/SGP E07 ARM/SGP E08ARM/SGP E09ARM/SGP E10 ARM/SGP E11ARM/SGP E12ARM/SGP E15 ARM/SGP E20ARM/SGP E22ARM/SGP E24 click here for list of sites Constrained to TOA Observation? No (Untuned)Yes (Tuned)

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

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.