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La Jolla Fog Study

Summary

June - July 2002

V. Ramanathan, Greg Roberts, M.V. Ramana and Andy Pham
Center for Atmospheric Sciences, Scripps Institution of Oceanography, UCSD


We conducted a ground-based experiment to study fog/marine-stratus clouds over the San Diego region. The purpose of the experiment is to understand aerosol/cloud interactions and how they influence cloud radiative properties and precipitation. The site at Mt. Soledad gives us a unique opportunity to simulate flying a plane because clouds can envelope the top of the "mountain" (at 811 feet) during the fog events.

Motivation:
• Relate total aerosol concentration and CCN to cloud droplet concentration
• Directly measure CCN at a low enough supersaturation such NCCN = ND.
• Assess scientific approach for aircraft study
   - Is the instrumentation sufficient to characterize cloud processes (and radiative structure)?
   - Effective and cheap platform for measurements on clouds


Instruments:
• FSSP: cloud droplet distribution
• Cloud Condensation Nuclei (CCN): aerosol concentration between 0.1 and 1.0% supersaturation
   - DH1 - static thermal-gradient chamber
   - Scripps CCN - continuous flow chamber
• Condensation Particle Counter: total aerosol concentration
• Scanning Mobility Particle Sizer (SMPS)
   - aerosol size distribution
• Weather Station: pressure, temperature, wind speed and direction, relative humidity

La Jolla Fog Study Photos