MASE

2005 MASE-MArine Stratus Experiment-Pt. Reyes, CA

5 July 2005 - 27 July 2005

Lead Scientist: Peter Daum

Observatory: OSC

The MArine Stratus Experiment (MASE) was designed to examine the influences of anthropogenic aerosols on marine stratus clouds so that the relevant processes can be more accurately represented in climate models. The primary measurement platform was the DOE G-1 research aircraft. The G-1 carried numerous state-of-the-art instruments for characterization of aerosol properties, cloud microphysics, and atmospheric state parameters including ozone. The aircraft was based out of Mather airport, just south of Sacramento, and flew 13 research flights. These flights were planned on the basis of forecast or prevailing meteorological conditions, specifically the presence of cloud layers over the near coastal (100 nautical miles) Pacific Ocean. All flights were conducted during daylight hours. Under appropriate meteorological conditions, flights over the ARM Mobile Facility (AMF) site located at Point Reyes National Seashore were emphasized. AMF instrumentation included a 95-GHz cloud radar, microwave radiometers for measurement of liquid water path, a complete radiometer package, lidars for measuring cloud base, a balloon borne sounding system, a surface meteorology package, an aerosol package, and other instruments. When possible, flights included below-cloud (no lower than 500 feet above ground level), in-cloud, and above-cloud passes. Flights farther away from the coast (up to 200 nm) were also flown, both in conjunction with flights over Point Reyes and independently. Such flights were conducted in uncontrolled airspace, or in Military Operations Areas (MOA''s). Flight altitudes ranged approximately between 300'' above the ocean surface to no higher than 10,000''. Another key measurement platform was the CIRPAS Twin Otter research aircraft instrumented by researchers from the California Institute of Technology and ASP investigators. The G-1 fights were conducted in co-ordination with the Twin Otter that has a similar complement of instrumentation except that the Twin Otter also carried a sophisticated complement of radiometers to measure up- and down- welling radiation fields. Much of the emphasis of the present project was examination of the chemical and microphysical properties of aerosol particles which have, or have not, been activated to become cloud droplets. The Point Reyes site was well situated to such a study, being shrouded in fog much of the time. A campaign surface site was located near the AMF site. A key sampling device there was the Cloudwater Virtual Impactor (CVI), which inertially separates cloud droplets from the surrounding air, and then evaporates these droplets so that the residual aerosol particles may be studied. Several of the instruments were either duplicated in the aerosol sampling system, or are switched between the two systems, to permit comparison of the properties of activated and unactivated aerosol particles.