Conditions Governing the Formation of Stratocumulus Clouds over the Western Atlantic during Cold Air Outbreaks.
Extensive stratocumulus (Sc) clouds from frequently in the winter months over the western North Atlantic Ocean during episodes of cold air advection off the continent. During a four month study period (November 1981 through February 1982), 25 separate episodes resulted in varying extents and amounts...
| Main Authors: | , , |
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| Other Authors: | |
| Format: | Text |
| Language: | English |
| Published: |
1984
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| Subjects: | |
| Online Access: | http://www.dtic.mil/docs/citations/ADA146780 http://oai.dtic.mil/oai/oai?&verb=getRecord&metadataPrefix=html&identifier=ADA146780 |
| Summary: | Extensive stratocumulus (Sc) clouds from frequently in the winter months over the western North Atlantic Ocean during episodes of cold air advection off the continent. During a four month study period (November 1981 through February 1982), 25 separate episodes resulted in varying extents and amounts of maritime cloud cover during 36 days, or 30% of the time during the study period. An examination of satellite imagery and surface analysis charts shows that these offshore Sc formations occur primarily following the passage of a cold front offshore, or in the southwest quadrant of a passing cyclone, or with the development of a high pressure ridge over the Atlantic coastal states. Data from four buoys between Cape Hatteras and Maine were used to look for thresholds in air-sea temperature difference (delta tan) and surface windspeed for the initiation and maintenance of these Sc formations. For locations from 25 to 200 miles (40 to 300km) east of Cape Hatteras, thresholds of 5 C and 5 m/s at a given at-sea location seem to be a good predictor for the existence of Sc overhead. The reliability of this rule decreases rapidly within 50 miles (80km) of the shoreline where the fetch may be inadequate. For locations 150 miles (240km) or so east of Cape Cod and in the Gulf of Maine, these rules break down and the air sea temperature difference and windspeed do not appear to have any useful predictor capability. |
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