DATA DESCRIPTION

GOES Data for FIRE/SRB:

• Hourly visible data from GOES 6 satellite
• Pixel size 7 km near nadir --> pixels ~ 12 km x 7 km for Wisconsin
• October 11 - November 2, 1986 (Days 284 - 306)
• Observations ~ 4 minutes after GMT hour
• Data for eighteen FIRE/SRB Surface Stations in Wisconsin
• Data referenced in:

  Whitlock, C. H., LeCroy, S. R., and Raitch, E. J.: GOES Satellite Observations for the FIRE/SRB Wisconsin Experiment Region from October 11 Through November 2, 1986, NASA TM-100485, October 1987.

GOES Data for Narrowband-Broadband Correlations:

• Hourly visible data from GOES 6 satellite
• Pixel size 4 km near nadir
• October 1 - October 31, 1986 (Days 274 - 304)
• Data averaged on standard 2.5° x 2.5° ERBE Grid ( PDF, PostScript, or GIF) in the region 100°W > longitude > 90°W and 45°N > latitude > 35°N

ERBE Data for Narrowband-Broadband Correlations and for Directional Models:

• S-9 scanner data from the ERBS satellite
• October 1 - October 31, 1986 (Days 274 - 304)
• Data averaged on standard 2.5° x 2.5° ERBE Grid ( PDF, PostScript, or GIF) in the region 100°W > longitude > 90°W and 45°N > latitude > 35°N

NARROWBAND-BROADBAND CORRELATIONS

• GOES data are averaged on standard 2.5° x 2.5° ERBE Grid
• ERBE data are matched to nearest GOES hourly data
• No data are used with SZA > 85° or VZA > 70°
• GOES counts, D are converted to narrowband reflectance using the Whitlock radiance calibration:

  

  where

  

  is the cosine of the solar zenith angle and

  

  is the narrowband visible solar constant.
• Narrowband albedos are calculated using ERBE bidirectional models. A composite anisotropic correction is calculated based on the GOES angles and the ERBE scene fractions
• A regression of the form:

  

  is performed between the broadband (ERBE) and narrowband (GOES) albedos shown in this PLOT of the albedos.
• The coefficients are from data in the region 100°W > longitude > 90°W and 45°N > latitude > 35°N:

  

  

  

  

  where

  

DIRECTIONAL MODELS

Directional models (relating variation of ERBE broadband albedo to variation of solar zenith angle) were produced for the ERBE/GOES analysis grid

• Created using ERBS satellite data for October 1986
• Data in the region 100°W > Longitude > 90°W, 45°N > Latitude > 35°N were used
• A separate regression of the form:

  

  was performed for each ERBE scene type (Clear, Partly Cloudy, Mostly Cloudy, and Overcast) as shown in this PLOT.
• The coefficients are:

  Overcast

  

  

  

  Mostly Cloudy

  

  

  

  Partly Cloudy

  

  

  

  Clear

  

  

  

CALCULATION OF BROADBAND ALBEDOS

For each hour of each FIRE/SRB site:

• A broadband albedo is calculated for each ERBE scene type from the directional models
• A narrowband albedo is calculated for each broadband albedo from the narrowband-broadband correlation
• An effective visible count, Deff, is calculated for each narrowband albedo from the Whitlock calibration
• The actual visible count, Dact, from FIRE/SRB data referenced above, is interpolated between the effective visible counts of the different ERBE scene types to determine the cloud fraction and corresponding anisotropic factor
• The narrowband albedo is calculated from the actual visible count, Dact, the Whitlock calibration, and the anisotropic factor
• The broadband albedo is calculated from the narrowband-broadband correlation