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CSTAR Investigation Carolina Coastal Fronts

CSTAR Investigation Carolina Coastal Fronts. October 16, 2003 K. Wyat Appel Keith Contre Allen J. Riordan Department of Marine, Earth, and Atmospheric Sciences North Carolina State University. Schematic Example of a Coastal Front. Role of the Gulf Stream. Provides Thermal Contrast

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CSTAR Investigation Carolina Coastal Fronts

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  1. CSTAR InvestigationCarolina Coastal Fronts October 16, 2003 K. Wyat Appel Keith Contre Allen J. Riordan Department of Marine, Earth, and Atmospheric Sciences North Carolina State University

  2. Schematic Example of a Coastal Front

  3. Role of the Gulf Stream • Provides Thermal Contrast • Gulf Stream structure may influence CF development

  4. Coastal Front Case Study • Coastal Front of 29-30 March 2001 • surface analysis every 6 hours from 0300 UTC 29 March to 0900 UTC March 30 • temperature analysis every 2C • sea-level pressure analysis every 2 mb • Highlights some of the difficulties forecasters encounter with coastal fronts

  5. 0300 UTC March 29 2001

  6. 0600 UTC March 29 2001

  7. 0900 UTC March 29 2001

  8. 1200 UTC March 29 2001

  9. 1500 UTC March 29 2001

  10. 1800 UTC March 29 2001

  11. 2100 UTC March 29 2001

  12. 0000 UTC March 30 2001

  13. 0300 UTC March 30 2001

  14. 0900 UTC March 30 2001

  15. Temperature Trend at Cape Hatteras

  16. Temperature Trend at Wilmington

  17. Temperature Trend at Raleigh

  18. Was it a Typical Case? • Which fronts move ashore? • Can we differentiate? • What changes accompany FROPA? • Temperature • Wind Direction • Precipitation • Can models be improved?

  19. Compositing • Composting • Compositing

  20. Data Sources • National Data Buoy Center (NDBC) • buoy 41001 • buoy 41002 • SAMSON (from NCDC) • 1961 -1990, 1990-1995 • Cape Hatteras, Wilmington • Raleigh • NCEP reanalysis data (composites)

  21. Platforms Used

  22. Offshore Coastal Front Detection Detection based on wind speed, wind direction, and temperature Detection Pairs Cape Hatteras / 41001 Wilmington / 41002

  23. Missing Buoy Data • One or the other = 44 % • Both buoys missing = 3% • Missing data not distributed evenly • Complicated coastal front detection • Seasonal comparisons limited

  24. Composite Overview • Used NCEP reanalysis data • Resolution • Spatial 2.5° by 2.5° • Temporal: every 6 hours • Students’ t test • Large, Synoptic features

  25. Algorithm Results • 432 coastal front events found from 1984 – 1994 • Fronts were classified according to behavior • 103 Offshore fronts 83 cold season 20 warm season

  26. Algorithm Results • 432 coastal front events found from 1984 – 1994 • Fronts were classified according to behavior • 73 Onshore fronts 68 cold season 5 warm season

  27. Algorithm Results • 432 coastal front events found from 1984 – 1994 • Fronts were classified according to behavior • 256 Diurnal fronts 127 cold season 129 warm season

  28. Start and End Time Distributions for Diurnal Fronts

  29. Algorithm Results CAD was not always present

  30. Offshore CF Relation to Season and CAD

  31. Cold-Season Frontogenesis

  32. Composite Comparisons(24 hours before onset) Onshore Offshore

  33. Composite Comparisons(24 hours before onset) Onshore Diurnal

  34. Composite Comparisons(12 hours before onset) Onshore Offshore

  35. Composite Comparisons(12 hours before onset) Onshore Diurnal

  36. Composite Comparisons(onset) Onshore Offshore

  37. Composite Comparisons(onset) Onshore Diurnal

  38. Composite Comparisons(12 hours after onset) Onshore Offshore

  39. Composite Comparisons(12 hours after onset) Onshore Diurnal

  40. Composite Comparisons(24 hours after onset) Onshore Offshore

  41. Composite Comparisons(24 hours after onset) Onshore Diurnal

  42. Summary Significant Discriminators • Onshore • Onshore Surface Vg • Sfc Low in NW Gulf • Deep Upper Trof • Offshore • Coast-Parallel Vg • Ridge in NW Gulf • Shallow Transient Trof

  43. Can You DifferentiateOnshorefromOffshore?

  44. Answer: Onshore

  45. Answer: Offshore

  46. Answer: Onshore!

  47. Future Work • Composite on Finer Scale • Especially CAD Erosion • Add Precip Climatology • Suggestions?

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