5.4
Observations of stratocumulus entrainment in the coastal zone
John Kalogiros, National Observatory of Athens, Athens, Greece and NPS, Monterey, CA; and Q. Wang
The stratocumulus cloud within 100-200 km off the coast of central California was studied during the 1999 DECS summer campaign using the Twin Otter research aircraft operated by the CIRPAS of the Naval Postgraduate School. The instrumentation of the aircraft included fast sensors for the measurement of wind components, air temperature, humidity, liquid water, cloud droplet spectra, and aerosol size distribution. We found that the coastal zone is characterized by significant inhomogeneity of the mean and turbulent fields. The height of the marine temperature inversion typically varied from 400-500 m close to the shoreline to 800 m about 200 km offshore, while a smaller slope was observed in the direction along the coast. We estimated the entrainment velocity using the total water fluxes from level flight legs near the cloud top and jump conditions from porpoising soundings at the top of the cloud. Our results showed a significant spatial variation of the entrainment velocity. We further examined the response of entrainment velocity to the variability of external forcing such as the surface fluxes and the possible effect of the significant wind shear that is observed at the height of the temperature inversion. These results will be presented and the budget of the turbulent kinetic energy at different locations relative to the coast will be discussed.
Session 5, Cloudy BLs
Tuesday, 16 July 2002, 8:30 AM-1:59 PM
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