Instrument Testing and Deployment for the DOE CHAPS Field Campaign
EMSL Project ID
24697
Abstract
We are requesting support for EMSL participation in DOEs Cumulus Humilis Aerosol Plume Study, CHAPS. This campaign is being organized by DOEs Atmospheric Sciences Program (ASP) with support from NOAA, NASA and DOEs ARM Program. As discussed in the attached document, airborne field measurements of aerosols will be made below, within and above large fields of Cumulus humilis downwind of Oklahoma City, OK, between June 1 and June 30, 2007.
Cumulus humilis is a technical term describing small convective cloud systems with limited vertical extent. They cover much of the planet during the summer months and can process ~30% of all surface air and associated compounds within a one hour period. The measurements to be made during this program will allow scientists to characterize and contrast aerosols below and above these clouds. Sampling is designed to include clouds within both clean background air and clouds within polluted air downwind of Oklahoma City. These results will be used to evaluate the mathematical descriptions of the transport and transformation of aerosols within large scale models used to study climate change.
This work is directly relevant to the scientific goals of DOEs Climate Change Research Division since it is thought that aerosols may offset ~ 50% of the warming attributed to greenhouse gases. One of the mechanisms by which this offset occurs is through aerosol effects on cloud microphysical properties. Understanding the role of aerosol composition and size in determining why some aerosols are better suited to form cloud droplets, and how clouds, in turn, affect aerosols, are two key scientific goals of this program.
Pre-campaign, laboratory calibration and testing of an Aerosol MS (AMS) and a PTR-MS will be critical to assure success in making the actual measurements in the field. We propose to use the EMSL aerosol mass spectrometer to make high speed, size-dependent measurements of the composition of aerosols *not* activated into cloud droplets. A separate AMS to be provided by Aerodyne Corporation and Brookhaven National Laboratory (under separate funding) will provide similar (cross-calibrated) measurements for aerosols that *have been* activated into cloud droplets. Sampling of these activated droplets will be done in flight through the use of a counterflow virtual impactor to be provided by the NOAA Earth Systems Research Laboratory (ESRL). This specialized inlet allows relatively large cloud droplets to enter into a sampling line while rejecting smaller, non-activated aerosols. The droplets are then evaporated and the residual cores passed to the AMS. The ambient gas-phase hydrocarbon levels will play an important role in explaining the composition of the aerosols and possibly in suggesting what role aqueous phase chemistry played in their formation. The hours of requested usage for these instruments corresponds to the number of hours we expect to sample with the G-1 aircraft plus 10 additional hours for testing and calibration on the ground.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2007-05-31
End Date
2009-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members
Related Publications
Alexander ML, M Newburn, JM Hubbe, LA Berg, CM Berkowitz, SR Springston, G Senum, YN Lee, and E Andrews. 2007. "Measurement of the VOC Environment from an Aircraft Platform During an Aerosol-Cloud Interaction Study Near Oklahoma City." Presented at AGU Conference, San Francisco, CA on December 12, 2007.