Tradeoffs concerning complexity, expense and accuracy in observational data sets for the optical remote sensing of atmospheric parameters

A WMO sponsored workshop was held in Boulder, Colorado, in December, 1991, to address the direct and indirect effects of aerosols upon climate. The workshop addressed the question of which types of measurements are most important, as well as the complexities involved in acquiring those measurements. It was agreed that aerosol optical depth, condensation nuclei and chemical measurements of size fractionated aerosol should receive the highest priority as core measurements in the Global Atmospheric Watch (GAW) program. Additional recommended measurements included: 1) aerosol light scattering coefficient, 2) backwards-hemispheric scattering coefficient, 3) aerosol absorption coefficient, 4) cloud condensation nuclei; 5) vertical profile lidar, 6) aerosol mass and size distribution, and 7) diffuse and total sky radiation measurements. The present study represents a first attempt to assess the relationships between the optical acid aerosol characteristics which are to be measured, the unobserved (modeled) parameters which are necessary to assume, the resultant parameters retrieved, their accuracy, and the complexity (and expense) associated with these measurements programs. These relationships are presented in tabular form, with the first being actinometric measurements of aerosol optical thickness in the 0.3-3.0 μm shortwave spectral interval. Then progressively more refined measurement programs are outlined