Field sun photometer data collected from 1990 through 1991 is used to provide quantitative atmospheric correction to remotely sensed data of forest reflectance and radiance.

Airborne sun photometer data collected from 1990 through 1991 used to provide quantitative atmospheric correction to remotely sensed data of forest reflectance and radiance.

Laboratory hemispherical reflectance spectra measurements taken to eliminate the effects of atmosphere, understory, exposed soils, mixed species and canopy architecture

Airborne sun photometer data taken from C-130

The data in the Sunphotometer Optical Thickness Data from C130 Aircraft data set were collected in June, July and August 1987, and in August 1989. The data was collected at selected locations within the FIFE study area. Atmospheric optical depths derived from measurements of solar radiation by the airborne suntracking sunphotometer are available in this data set. These data are necessary for atmospheric correction of data from Earth viewing airborne and satellite sensors in the visible and near infrared regions of the electromagnetic spectrum. The data show that atmospheric optical depth changes significantly both spatially and temporally. Variability in atmospheric optical properties and substantial differences in atmospheric optical properties during the data collection, emphasize the need to make quantitative measurements of atmospheric optical properties at the time of remote sensing data acquisition.

Laboratory hemispherical reflectance spectra measurements taken to eliminate the effects of atmosphere, understory, exposed soils, mixed species and canopy architecture.

The NIPS and Reagan Sunphotometer Optical Thickness study compared various ground and image-based techniques used to characterize the atmosphere. These data are used to remove atmospheric absorption and scattering from remote sensing scenes so that surface parameters can be retrieved. An evaluation of the effects of uncorrected atmospheric absorption and scattering on various vegetation indices and subsequent biophysical parameter estimations was also undertaken. These data can also be used to derive aerosol size distribution (King et al., 1978) and thereby estimate the phase function. Aerosol optical depths were recorded at various locations within the FIFE site. A Normal Incident Pyrheliometer (NIP) and a Reagan sunphotometer was used to collect data during the IFCs. These data showed that daily averages span a range of 0.05 to 0.28 in the mid-visible wavelength (Bruegge et al., 1992a). Diurnal variations were recorded. The afternoon optical depths are greater than those of the morning by as much as 0.07. These data are analyzed using the Langley technique. Rayleigh optical depth is subtracted, and aerosol, ozone, and water vapor abundance's simultaneously measured. In retrieving ozone, a Junge aerosol model is assumed, thus, the natural log of aerosol optical depth is linear with wavelength (Bruegge et al., 1992a). This contrasts with other experimental approaches used by investigators in which an ozone abundance is assumed (Halthore and Markham 1992). This approach allows measurement of aerosol, but is limited by the accuracy of the ozone data.

Aerosol optical thickness in conjunction with an atmospheric model can provide estimates of atmospheric effects on transmitted and reflected solar radiation. These effects can then be used to correct aircraft and satellite radiometric data. In FIFE, three sunphotometers were used to track the sun through a range of airmasses during the period of February 6, 1987 through October 31, 1989. The Aerosol Optical Thickness from GSFC Data Set were analyzed using the Langley technique. Rayleigh optical depth was subtracted, and aerosol, ozone, and water vapor abundance's simultaneously measured. In retrieving ozone a Junge aerosol model was assumed, thus the natural log of aerosol optical depth was linear with wavelength (Bruegge et al. 1992). This approach allows measurement of aerosol, but is limited by the accuracy of the ozone data.

Aerosol optical thickness data reported by Robert Fraser

The Solar Transmissometer Aerosol Optical Thickness Data Set contains optical thickness data that provide a measure of the effect of aerosols on the attenuation of radiation through the atmosphere at 8 discrete wavelength bands throughout the visible and near IR portion of the electromagnetic spectrum. These data were collected using a ground-based solar transmissometer in June and July of 1987, and July and August of 1989, at two stations in the FIFE study area. These data are used to provide atmospheric correction of remotely sensed data using radiative transfer models and to study aerosol particle size distribution (see Halthore and Markham 1992; King et al. 1978). These data are also used to infer the optical clarity of the atmosphere.