Narrowband angular reflectance properties of the alkali flats at white sands, New Mexico

The CERES/ARM/GEWEX Experiment (CAGEX) for the Retrieval of Radiative Fluxes with Satellite Data

“…Calculated surface insolation for totalsky conditions is again too large (Fig. lb), in agreement with the GEWEX SRB Project (Alberta et al 1994;Whitlock et al 1995). Each SW bias in Table 1 can be very roughly scaled to an effective annual global, 24-h value by 1) multiplying the bias by the annual global, 24-h TOA insolation (1365/4 W nr 2 ) and then 2) dividing by the corresponding mean TOA insolation of the bias.…”

“…2a-d shows significant discrepancies. For surface SW flux, the discrepancies are larger than the uncertainties in the radiometric measurements, as found in earlier studies [i.e., Whitlock et al (1995) using algorithms from Darnell et al (1992) and Pinker and Laszlo (1992)]. For the observations of surface SW insolation, we combined measurements of the direct pyrheliometric flux and the diffuse flux from a shaded pyranometer, as recommended by BSRN.…”

“…The reflected component is more important with clouds, and it is difficult to accurately measure broadband TOA reflected flux using a narrowband radiance such as GOES-7. As noted earlier, the calibration of narrowband radiometers on operational satellites can be problematic (Brest and Rossow 1992;Whitlock et al 1995). After calibration, the measured directional radiance must be converted to a flux using angular and directional models (i.e., Suttles et al 1988;Suttles et al 1989).…”

“…The CAGEX estimate of the full SARB over the ARM CART site is produced by forward radiative transfer calculations and based heavily on satellite data. In this respect, while CAGEX is spatially and temporally intensive, the approach is similar to that used in the global GEWEX Surface Radiation Budget (SRB) Project (Whitlock et al 1995). The SRB Project uses International Satellite Cloud Climatology Project (Rossow et al 1991) data and fast SW (Pinker and Laszlo 1992) and LW (Gupta et al 1992) radiation codes for surface fluxes.…”

“…NOAA surface radiation (Hicks et al 1995) will provide measurements of aerosol optical depth and surface fluxes at other sites. CERES plans to conduct a surface optical property experiment over the SGP site during 1997, measuring the surface SW broadband albedo, SW spectral bidirectional reflectance, and the angular dependence of LW window radiance with a helicopter (Whitlock et al 1994); a preparatory airborne experiment has been conducted over Virginia to support this. The survey of surface radiative characteristics in the First International Satellite Land Climatology Project Field Experiment (FIFE; Sellers and Hall 1992) provides impetus to take similar measurements over the SGP site.…”