CHAPS

2007 Cumulus Humilis Aerosol Process Study (CHAPS)

4 June 2007 - 25 June 2007

Lead Scientist: Carl Berkowitz

Observatory: OSC

The primary goal of this campaign was to characterize and contrast freshly emitted aerosols above, within and below fields of cumulus humilis (or fair-weather cumulus, FWC) and to use these observations to address how below-cloud and above-cloud aerosol optical and cloud nucleating properties differ downwind of a mid-size city relative to similar aerosols in air less affected by emissions. The observations from this campaign can also be used to aid in the development and evaluation of parameterizations of the transformation and transport of these aerosols by FWC for use in regional-scale and Global Climate Models. This final product has the potential to reduce the uncertainties associated with the treatment of aerosols by these models. During CHAPS, the DOE Gulfstream-1 (G-1) aircraft carried two broad categories of instruments to measure climate-relevant properties of aerosols. One set of instruments measured the properties of aerosols found within individual cloud droplets. The other set of instruments measured these same properties both for aerosols not incorporated into cloud droplets as well as aerosols found outside of the larger cloudy environment. Joining the G-1 was the NASA Langley Research Center’s King Air Be-200. This aircraft had a High Spectral Resolution Lidar (HSRL) onboard to obtain profiles of aerosol backscatter and extinction in the vicinity of these clouds. Measurements were also made of the composition of aerosols inside and outside of the urban plume in order to characterize both activated and interstitial aerosols. Due to the transient nature and the small spatial scale of the individual FWC, this study looked at the aerosol properties in aggregate, rather than data from individual transects through a cloud. Surface measurements made just north of Oklahoma City can be used to continuously characterize aerosol and chemical features within the boundary layer.