HR: 14:55h
AN: A13E-06    [Abstracts]
TI: Aerosol-Cloud Interactions Evaluated with Aircraft Measurements during the Marine Stratus Experiment (MASE)"
AU: * Conant, W C
EM: conant@atmo.arizona.edu
AF: Department of Atmospheric Sciences, University of Arizona , Tucson, AZ 85721-0081
AU: Arnott, P
EM: pat@dri.edu
AF: Division of Atmospheric Sciences, Desert Research Institute, Reno, NV 89512
AU: Bucholtz, A
EM: bucholtz@nrlmry.navy.mil
AF: Marine Meteorology Division, Naval Research Laboratory, Monterey, CA 93943-5502
AU: Buzorius, G
EM: gbuzoriu@nps.navy.mil
AF: CIRPAS, Naval Postgraduate School, Monterey, CA 93943
AU: Chuang, P Y
EM: pchuang@es.ucsc.edu
AF: Earth Sciences Department, University of California, Santa Cruz, Santa Cruz, CA 95064
AU: Jonsson, H H
EM: hjonsson@nps.navy.mil
AF: CIRPAS, Naval Postgraduate School, Monterey, CA 93943
AU: Murphy, S M
EM: shanem@caltech.edu
AF: Department of Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
AU: Rissman, T A
EM: rissman@caltech.edu
AF: Department of Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
AU: Small, J D
EM: jsmall@es.ucsc.edu
AF: Earth Sciences Department, University of California, Santa Cruz, Santa Cruz, CA 95064
AU: Sorooshian, A
EM: armin@caltech.edu
AF: Department of Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
AU: Varutbangkul, V
EM: tomtor@caltech.edu
AF: Department of Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
AU: Flagan, R C
EM: flagan@caltech.edu
AF: Department of Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
AU: Seinfeld, J H
EM: seinfeld@caltech.edu
AF: Department of Chemical Engineering, California Institute of Technology, Pasadena, CA 91125
AB: In this presentation we explore how aerosols influence the microphysical, dynamical, and radiative properties of marine stratocumulus clouds. We address these aerosol-cloud interactions using data collected by the CIRPAS Twin Otter aircraft during the MASE (Marine Stratus Experiment) campaign, which was conducted off the coast of northern California in July of this year. The otter was instrumented to measure aerosol number concentration, size distribution from 15 nm - 2500 nm, composition (TOF-AMS; PILS), and light absorption. Furthermore, an array of optical probes on the aircraft provided detailed information on the cloud microphysics, including droplet concentration, size distribution, liquid water content and precipitation size distribution. Pyranometers measuring upwelling and downwelling solar irradiance (0.3 μm - 3.5 μm) mounted on a stabilized radiometer platform were used to obtain cloud albedo immediately above the region that was being profiled. Localized (2-20 km wide) regions of high aerosol concentration in the marine boundary layer (MBL) were found and identified as "ship tracks", although no coincident features were immediately apparent in the visible satellite images. Vertical profiles were conducted by the Twin Otter within and on both sides of each ship track to obtain the contrast in aerosol and cloud properties. The ship emissions enhanced aerosol number concentration by factors ranging from 2 to more than 10. They contribute almost entirely to sulfate aerosol -- there was virtually no change in organic aerosol concentration measured by the Aerodyne TOF-AMS or light absorption measured by a photoacoustic instrument within the tracks. The ship emissions are found to have a significant impact on the cloud microphysics, including nearly a doubling of droplet concentration and a reduction in effective radius. The change in droplet dispersion is found to be important in understanding the indirect effect. Cloud albedo tended to be slightly enhanced in the region immediately above a ship track, although the enhancement was well within the range of ordinary horizontal variation. The implications of these microphysical changes on precipitation, entrainment, and the second indirect effects are explored. Furthermore, a widespread layer of concentrated organic aerosol overlay the MBL. Its composition and size distribution are consistent with urban/continental aerosol. The implication that this layer may distribute CCN to remote low-cloud systems is discussed.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0320 Cloud physics and chemistry
DE: 0321 Cloud/radiation interaction
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 1600 GLOBAL CHANGE
SC: Atmospheric Sciences [A]
MN: Fall Meeting 2005