ARM Mobile Facility Begins Study of Marine Stratus Clouds


On March 12, 2005, DOE’s Atmospheric Radiation Measurement (ARM) Program deployed its new ARM Mobile Facility (AMF) for the first time at the Point Reyes National Seashore on the coast of California north of San Francisco to study the interactions between marine stratus clouds and aerosols and the effect of such interactions on the absorption and scattering in incoming solar radiation and drizzle. Marine stratus clouds are one of the most prevalent types of clouds on earth, and they exert a large-scale cooling effect on the ocean surface. Thus, they have an important effect on the earth s total energy budget. In addition, the formation and properties of marine stratus clouds are influenced by aerosols that are a byproduct of fossil fuel consumption. Despite their known importance to the earth-ocean-atmosphere system, relatively few detailed and comprehensive data on marine stratus clouds are available. Researchers from the ARM Program in collaboration with scientists from the U.S. Office of Naval Research and DOE’s Atmospheric Science Program are collecting data using the AMF to study marine stratus clouds, including coastal drizzle processes associated with the transformation of cloud water droplets to drizzle-size droplets in these clouds. The objectives of the experiment are to collect data on cloud-aerosol interactions to improve understanding of the (1) general relationship between cloud structure, aerosols, cloud microphysics, drizzle, and radiation in coastal marine stratus clouds and (2) the specific effects of aerosols on the discrepancy between the measured and modeled amount of solar radiation absorbed by these clouds.