The Aerosol Best Estimate (ABE) value-added product (VAP) provides best-estimate time series of total column aerosol optical depth (AOD) and the associated column Angstrom exponent, as well as time/height profiles of aerosol extinction, single-scattering albedo, asymmetry parameter, and Angstrom exponents above the Central Facility at the ARM Southern Great Plains (SGP) site.
As inputs, ABE uses datastreams from the Aerosol Intensive Properties VAP, the Aerosol Optical Depth VAP, the Merged Sounding VAP, and surface meteorological instrumentation (MET). (Note that evaluation versions of this VAP used data from the Raman Lidar Vertical Profiles (RLPROF) VAP, but the current release does not. It is anticipated that future releases will use input from RLPROFBE.)
ABE applies quality checks and a cloud screen based on the standard of deviation on AOD measurements (from the normal incidence multifilter radiometer and multifilter rotating shadowband radiometer), employing interpolation over short gaps or a multi-variable regression over longer gaps to provide a nearly continuous time series estimate of AOD. The multi-variable regression includes surface aerosol scattering (from the aerosol observing system [AOS] and AIP), relative humidity (from MET), and boundary-layer height (seasonally proscribed) with weighting coefficients determined monthly to maximize agreement with coincident column AOD measurements. Column Angstrom exponents are computed from screened AOD values and interpolated over gaps.
ABE reports time/height profiles of aerosol extinction at 500 nm estimated via a seasonal climatology of RL extinction profiles as a function of column optical depth. ABE provides best-estimate time/height profiles of intensive properties of single-scattering albedo (SSA), backscatter fraction (bsf), and asymmetry parameter (g) for the red, green, and blue wavelengths estimated from surface measurements (from AOS/AIP) and the vertical profile of relative humidity (Merged Sounding) along with the assumption that the dry aerosol properties are vertically well mixed. The well mixed assumption allows the humidity dependence measured at the surface to be applied to the vertical column, yielding estimates for the ambient aerosol scattering that reflect the vertical structure in the humidity field while the ratios involved in computing the intensive properties (SSA, bsf, g) mitigate scale-height effects on the extensive aerosol profiles.