PROGRAM TITLE:	Boundary Layer Dynamics, Marine Aerosols 
ACTIVITY STREAM:	Process Studies
SCIENCE ELEMENT:	Biogeochemical Dynamics


SCIENTIFIC MERIT:  This is a basic research effort to understand and 
quantify the physical and chemical mechanisms determining the size 
distribution and chemical constituents of marine aerosols and the 
dynamics of their evolution.  Knowledge of the physical and chemical 
properties of marine aerosol particles is important because of the 
role these particles play in a number of important atmospheric 
processes.  Marine aerosols affect radiative transfer and climate 
directly by scattering and absorbing radiation and indirectly by 
influencing the droplet size distribution and albedo of marine 
boundary layer clouds.  In addition, the emissions of reduced sulfur 
gases from the oceans contribute significantly to the global sulfur 
cycle.  The processes controlling the production and consumption of 
these reduced sulfur gases in the sea are poorly understood.
A guiding principle is to achieve a mechanistic rather than empirical 
or correlational understanding of marine aerosol dynamics.  
Immediate objectives include determining the effects of:  
microphysical parameters on evolution of measured aerosol 
distributions, non-precipitating cloud cycling, and gas-to-particle 
conversion dynamics.  The role of marine aerosols in cloud 
condensation nuclei dynamics and electro-optical extinction 
coefficient will be specifically targeted.  This work will capitalize on 
and improve predictive models developed by DOE and DOD.  Parallel 
efforts in the laboratory, field experiments, and a modeling 
component will address electro-optics problems impacting DOD 
communications, surveillance, and guidance issues while at the same 
time work the two highest priority Global Change science element 
problems.  This program will provide new data and insight to the 
role of clouds and bio/atmosphere/ocean flux questions highlighted 
by the USGCRP.  This research initiative has been approved by DOD 
and endorsed by the National Academy of Science.   Several 
workshops were held to frame this program, and the federal and 
academic research communities have participated from the 
STAKEHOLDERS:  Strong interaction with DOD laboratories and the 
academic communities is programmed.  For example, transition 
routes from federal labs and academia are established with Air Force 
and Navy operational modeling community. This work will then 
support regional nested models made available to the Global Climate 
Modelers.  A strong cooperative effort with DOE modelers involving 
evolution of aerosols from a point source is underway now.  In 
addition to this program's emphasis on modeling and hence 
prediction of natural and human factors involved in the generation of 
cloud condensation nuclei, whose impacts on climate are still not well 
understood; the program interacts with US-JGOFS in helping to 
characterize the oceanic chemistry, particularly of the mixed layer. 
Participation in the US-JGOFS EQ-PAC experiment was highly 
contributive, participation in the Southern Ocean experiment is 
POLICY RELEVANCE:  One objective of this program is to provide 
better prediction of laser systems effectiveness in varying 
oceanographic and meteorological conditions.  However, the same 
understanding contributes directly to the evaluation of climate 
change and natural and man-made variability.  In particular, the 
program seeks to provide understanding of to what degree natural 
and man-made sulfur compounds contribute to cloud creation by 
providing cloud condensation nuclei and the relative roles of 
anthropogenic versus natural sources.
PROGRAM CONTACT:  Dr. Edward J. Green, ONR Code 323C, 800 N. 
Quincy Street, Arlington, VA 22217-5660, (703) 696-4591