In 1999 and 2000, the Cloud and Aerosol Research Group (CARG) of the University of Washington will participate in two NASA-funded projects by operating its Convair-580 research aircraft in field projects in the Marshall Islands and in Southern Africa. The primary purpose of the NASA experiments is to compare airborne, in situ measurements of cloud and aerosol properties with remote sensing measurements from satellites. Taking advantage of the opportunities offered by the NASA projects, CARG will undertake additional experiments supported by NSF while the Convair-580 is in transit to and from the field sites and on location in Southern Africa. In September 1999, on the return from the Marshall Islands, the airplane will be based near Tokyo for about a week to carry out several series of measurements of the variation with altitude of the physical, chemical, and optical properties of aerosol particles. The intention is to provide data that are comprehensive enough to permit comparisons of computed and measured effects of the aerosols on solar radiation (so-called radiative "closure" calculations). The second NSF experiments will be in 2000, when CARG and the research aircraft will be participating in SAFARI-2000. The focus will be on the pall of polluted air over the Atlantic Ocean off the coast of Southern Africa. Measurements will be taken to document the evolution of the physical and chemical properties of the aerosols and to measure vertical profiles as in the earlier Japanese experiments. Collaborating with Dr. Hobbs in these experiments will be several other investigators who will bring new instruments for atmospheric measurements. The plan is to evaluate the performance of the instruments in flights around the Seattle area before the NASA missions to Japan and Southern Africa.