Overview of the Cumulus Humilis Aerosol Processing Study

Abstract

The primary goal of the Cumulus Humilis Aerosol Processing Study (CHAPS) was to characterize and contrast freshly emitted aerosols below, within, and above fields of cumuli, and to study changes to the cloud microphysical structure within these same cloud fields in the vicinity of Oklahoma City during June 2007. CHAPS is one of few studies that have had an aerosol mass spectrometer (AMS) sampling downstream of a counterflow virtual impactor (CVI) inlet on an aircraft, allowing the examination of the chemical composition of activated aerosols within the cumuli. The results from CHAPS provide insights into changes in the aerosol chemical and optical properties as aerosols move through shallow cumuli downwind of a moderately sized city. Three instrument platforms were employed during CHAPS, including the U.S. Department of Energy Gulfstream-1 aircraft, which was equipped for in situ sampling of aerosol optical and chemical properties; the NASA Langley King Air B200, which carried the downward-looking NASA Langley High Spectral Resolution Lidar (HSRL) to measure profiles of aerosol backscatter, extinction, and depolarization between the King Air and the surface; and a surface site equipped for continuous in situ measurements of aerosol optical properties, profiles of aerosol backscatter, and meteorological conditions, including total sky cover and thermodynamic profiles of the atmosphere. In spite of record precipitation over central Oklahoma, a total of 8 research flights were made by the G-1 and 18 by the B200, including special satellite verification flights timed to coincide with NASA satellite A-Train overpasses.