Airborne Measurement of Dimethylsulfide, Isoprene, and other Trace Volatile Organic Compounds using a Proton Transfer Reaction Mass Spectrometer during the 2008 DOE ASP VOCALS Field Campaign
EMSL Project ID
30439
Abstract
This proposal requests the participation of EMSL scientist Dr. M. Lizabeth Alexander as a collaborator to deploy on the DOE G-1 aircraft a state-of-the-art volatile organic compound instrument, the Proton Transfer Reaction Mass Spectrometer (PTRMS), in the upcoming DOE ASP VOCALS field campaign in Chile, October to November 2008. The main objective is to make fast and sensitive in-situ measurement of dimethylsulfide (DMS), isoprene, terpenes, and aromatic compounds that are crucial to identifying the sources of aerosol particles, including marine, combustion, and terrestrial biogenic emissions, and the role they play in the formation and radiative properties of marine stratus/stratocumulus clouds that contribute importantly to radiative forcing of the climate system.The DOE ASP VOCALS field campaign is a part of an NSF sponsored major international field program scheduled for Oct-Nov 2008 in Chile (the VAMOS Ocean-Cloud-Atmosphere-Land Study Regional Experiment, VOCALS-REX) in the tropical southeastern Pacific Ocean, and is designed to gain a quantitative understanding of the role cloud-aerosol interactions play in the formation and radiative properties of marine stratus/stratocumulus clouds that dominate much of the eastern parts of the Pacific and Atlantic, including this region. This influence of aerosol loading on cloud radiative properties is referred to as aerosol indirect effect. Satellite data of this region show cloud droplet number concentration, Ncd, is higher toward the coast and lower into the open ocean. The high Ncd near the coast is thought to result from a high aerosol loading derived from either DMS released from this nutrient rich upwelling region or terrestrial sources of both natural and anthropogenic in origin. Further away from the coast (~400 km), the clouds often collapse and exhibit a network of so called "pockets of open cells" (POCs) wherein clouds are absent. It is hypothesized that POCs, which persist for a period of a few days, form because of drizzle formation by collision coalescence favored by fewer but larger cloud droplets, thereby depleting accumulation mode particles. In order to provide experimental evidence for the aerosol-cloud relationships with which the aerosol indirect effect is based upon, the DOE ASP effort will make detailed characterization of gases, aerosols, clouds, and radiation fields under contrasting conditions using the instrumented DOE G-1 to investigate not only the relationships between cloud microphysics (Ncd, size distribution and dispersion) and aerosol properties (size, number, chemical composition, cloud nucleating ability), but also the sources of aerosols that are responsible for the indirect effect. The concentrations of key organic compounds (DMS, isoprene, terpenes, benzene, toluene) determined using a PTRMS on the G-1 supported by this proposed research, in combination with other gas (CO, O3, SO2) and aerosol (SO42-, NO3-, NH4+, Organics, Na+, Cl-, and methanesulfonate) chemical data simultaneously collected, will permit the different aerosol sources and their contributions to cloud radiative properties to be unambiguously identified.
Project Details
Project type
Large-Scale EMSL Research
Start Date
2008-09-05
End Date
2010-09-30
Status
Closed
Released Data Link
Team
Principal Investigator
Team Members