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John M. Bane Sara M. Haines Melanie F. Meaux University of North Carolina Chapel Hill

Atmospheric Internal Boundary Layer Over the Oregon Shelf During Summer 2001: Its Causes and Oceanic Consequences. John M. Bane Sara M. Haines Melanie F. Meaux University of North Carolina Chapel Hill Roger M. Samelson Oregon State University Corvallis.

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John M. Bane Sara M. Haines Melanie F. Meaux University of North Carolina Chapel Hill

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  1. Atmospheric Internal Boundary LayerOver the Oregon Shelf During Summer 2001:Its Causes and Oceanic Consequences John M. Bane Sara M. Haines Melanie F. Meaux University of North Carolina Chapel Hill Roger M. Samelson Oregon State University Corvallis Sponsor: National Science Foundation

  2. ATMOSPHERIC SURFACE PRESSURE Height of 1000 mb surface (m) Average: May-August 2001 ALEUTIAN LOW L COAST E. PACIFIC HIGH H THERMAL LOW L

  3. ATMOSPHERIC SURFACE PRESSURE Height of 1000 mb surface (m) Average: May-August 2001 Columbia R. .Tillamook .Newport .Florence 160 170

  4. Northward Wind Stress Newport NDBC Buoy (N/m2) DOWNWELLING (25%) UPWELLING (75%) May June July August MONTH 2001

  5. Northward Wind Stress Newport NDBC Buoy (N/m2) DOWNWELLING (25%) UPWELLING (75%) May June July August MONTH 2001 July 24

  6. ATMOSPHERIC SURFACE PRESSURE Height of 1000 mb surface (m) 5pm PDT 24 July 2001 L COAST L H L L

  7. AIRCRAFT WINDS (150m) July 24, 2001 20 m/sec Latitude Longitude

  8. AIRCRAFT WINDS (150m) July 24, 2001 20 m/sec VERTICAL SECTIONS Latitude Longitude

  9. q Atmos q Ocean T July 24 Line 4

  10. Temperature Inversion q Mixed Layer Atmos q Ocean T July 24 Line 4

  11. Temperature Inversion q Mixed Layer COOL Atmos q Ocean T July 24 Line 4

  12. OFFSHORE SHELFBREAK q NEARSHORE COOL Atmos q Ocean T July 24 Line 4

  13. ATMOSPHERIC POTENTIAL TEMPERATURE PROFILES July 24 Line 4 Altitude (m) SHELFBREAK OFFSHORE SHELFBREAK NEARSHORE NEARSHORE Atmos q COOL OFFSHORE q (K)

  14. ATMOSPHERIC POTENTIAL TEMPERATURE PROFILES July 24 Line 4 Near-surface dT/dz => sensible heat flux into cool, upwelled waters Flux ~10 W/m2 Altitude (m) SHELFBREAK OFFSHORE SHELFBREAK NEARSHORE NEARSHORE Atmos q COOL OFFSHORE q (K)

  15. ATMOSPHERIC POTENTIAL TEMPERATURE PROFILES July 24 Line 4 Altitude (m) OFFSHORE SHELFBREAK TOP OF IBL NEARSHORE Atmos q COOL IBL q (K)

  16. q COOL Atmos q IBL Ocean T July 24 Line 4

  17. q m/sec Atmos q, v Atmos q Ocean T July 24 Line 4

  18. q m/sec LOW SPEED Atmos q, v Atmos q IBL Ocean T July 24 Line 4

  19. q m/sec LOW SPEED Atmos q, v Atmos q AIRCRAFT TRACK Ocean T July 24 Line 4

  20. qv Wind v u speed IBL

  21. qv Wind Ri v u speed INV IBL IBL

  22. SEA SURFACE TEMP and BUOY WINDS

  23. INTERNAL BOUNDARYLAYER HEIGHT (meters)

  24. h (IBL thickness, m) h = 18 X1/2 [Hsu, 1983] X (downwind distance, km) Internal Boundary Layer Thickness vs. Downwind Distance July 24, 2001

  25. h (IBL thickness, m) h = 18 X1/2 [Hsu, 1983] X (downwind distance, km) Internal Boundary Layer Thickness vs. Downwind Distance July 24, 2001

  26. SEA SURFACE TEMP and BUOY WINDS SLOWER WINDS NEARSHORE => + WIND STRESS CURL

  27. ty z . . . . x UPWELLING WITH CONSTANT SOUTHWARD WIND STRESS (No IBL)

  28. ty z . IBL . . . x UPWELLING WITH VARIABLE SOUTHWARD WIND STRESS (IBL Present)

  29. EKMAN PUMPING (m/day) NORTHERLY WINDS SOUTHERLY WINDS NORTHWARD WIND (NDBC Buoy, m/sec)

  30. Conclusions • Synoptic atmospheric pressure field determines first-order • wind stress spatial and temporal patterns • Wind stress can be modified by local effects • Atmosphere-to-ocean sensible heat flux lowers surface • air temperature over cool, upwelled waters • An Internal Boundary Layer forms, and increased static • stability plus thermal wind effect in the IBL lowers • the nearshore wind stress • IBL positive wind stress curl => upward Ekman pumping • of about 1 m/day

  31. August 01, 2001Remnant upwelled waterunder moderate southerly winds

  32. ATMOSPHERIC SURFACE PRESSURE Height of 1000 mb surface (m) 5pm PDT 01 August 2001 L L L COAST H L

  33. ATMOSPHERIC SURFACE PRESSURE Height of 1000 mb surface (m) 5pm PDT 01 August 2001 L L L COAST H L

  34. AIRCRAFT WINDS (150m) August 01, 2001 20 m/sec Latitude Longitude

  35. AIRCRAFT WINDS (150m) August 01, 2001 20 m/sec VERTICAL SECTIONS Latitude Longitude

  36. Atmos q Ocean T Aug 01 Line 6

  37. ATMOSPHERIC POTENTIAL TEMPERATURE PROFILES August 01 Line 6 Altitude (m) SHELFBREAK NEARSHORE Atmos q OFFSHORE q (K)

  38. ATMOSPHERIC POTENTIAL TEMPERATURE PROFILES August 01 Line 6 Altitude (m) TOP OF IBL IBL Atmos q COOL q (K)

  39. q COOL Atmos q IBL Ocean T Aug 01 Line 6

  40. q Atmos q IBL Ocean T Aug 01 Line 6

  41. Conclusions • Synoptic atmospheric pressure field determines first-order • wind stress spatial and temporal patterns

  42. Conclusions • Synoptic atmospheric pressure field determines first-order • wind stress spatial and temporal patterns • Wind stress can be modified by local effects

  43. Conclusions • Synoptic atmospheric pressure field determines first-order • wind stress spatial and temporal patterns • Wind stress can be modified by local effects • Atmosphere-to-ocean sensible heat flux lowers surface • air temperature over cool, upwelled waters

  44. Conclusions • Synoptic atmospheric pressure field determines first-order • wind stress spatial and temporal patterns • Wind stress can be modified by local effects • Atmosphere-to-ocean sensible heat flux lowers surface • air temperature over cool, upwelled waters • An Internal Boundary Layer forms, and increased static • stability in the IBL lowers the nearshore wind stress

  45. Conclusions • Synoptic atmospheric pressure field determines first-order • wind stress spatial and temporal patterns • Wind stress can be modified by local effects • Atmosphere-to-ocean sensible heat flux lowers surface • air temperature over cool, upwelled waters • An Internal Boundary Layer forms, and increased static • stability in the IBL lowers the nearshore wind stress • IBL positive wind stress curl => upward Ekman pumping • of about 0.1-0.5 m/day

  46. q m/sec JET JET LOW SPEED Atmos q, v Atmos q Ocean T July 24 Line 4

  47. q COOL Atmos q Ocean T July 24 Line 4

  48. q Atmos q IBL Ocean T Aug 01 Line 6

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