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LINKING THE UPPER AND LOWER TROPOSPHERE: HIGHS AND LOWS Dr. Sam Miller

Learn about the concepts of troughs, ridges, wind flow aloft, forces in the free troposphere, and the implications of divergence aloft. Understand the characteristics and behaviors of low pressure systems.

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LINKING THE UPPER AND LOWER TROPOSPHERE: HIGHS AND LOWS Dr. Sam Miller

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  1. LINKING THE UPPER AND LOWER TROPOSPHERE: HIGHS AND LOWS Dr. Sam Miller Weather & Climate – MTDI 1200OL Plymouth State University 1

  2. Ahrens, Ch. 6, 7 & 8

  3. Troughs and Ridges

  4. Troughs & Ridges • Ridge– elongated region of clockwise curvature in the wind field • Anticyclonic • Drawn as a zigzagging line • Trough – elongated region of counterclockwise curvature in the wind field • Cyclonic • Drawn as a curved line (sometimes dashed)

  5. Troughs & Ridges • Both are visible in the wind field and the height contours

  6. WIND FLOW ALOFT

  7. REGIONS OF CYCLONIC CURVATURE (AXES MARK SHARPEST TURNING)

  8. REGION OF ANTICYCLONIC CURVATURE (AXIS MARKS SHARPEST TURNING)

  9. TROUGH (TROF) RIDGE TROUGH (TROF)

  10. PART OF A GLOBAL PATTERN

  11. Divergence & Convergence Aloft

  12. TROUGH (TROF) RIDGE TROUGH (TROF)

  13. HEIGHT CONTOURS

  14. L LOW HEIGHTS H H HIGH HEIGHTS HIGH HEIGHTS

  15. Recall characteristics of forces in the free troposphere: • Pressure Gradient Force (PGF): Points across isobars (or height contours) toward lower pressure (heights) • Coriolis Force (CoF): Points 90 degrees to the right of the wind direction (Northern Hemisphere) • Centrifugal Force (CeF): Points away from the focus of curvature (not present in straight flow)

  16. L H H

  17. REGIONS OF STRAIGHT-LINE FLOW L H H

  18. REGIONS OF CURVED FLOW L H H

  19. CeF CeF PGF PGF L CoF CoF FORCES IN CURVED REGIONS H H PGF CoF CeF

  20. CeF CeF PGF PGF L CoF CoF H H PGF CoF CeF

  21. CeF CeF PGF PGF L CoF CoF H H PGF CoF PGF & CeF IN OPPOSITION CeF

  22. CeF CeF PGF PGF L CoF CoF WIND SLOWS DOWN IN BASE OF TROUGH H H PGF CoF CeF

  23. CeF PGF & CeF ARE ADDITIVE CeF PGF PGF L CoF CoF H H PGF CoF CeF

  24. CeF CeF WIND SPEEDS UP AT TOP OF RIDGE PGF PGF L CoF CoF H H PGF CoF CeF

  25. MAXIMUM SPEED MAXIMUM SPEED L H H MINIMUM SPEED

  26. L SLOWING DOWN SPEEDING UP H H

  27. L CONVERGENCE ALOFT DIVERGENCE ALOFT H H

  28. Implications of Divergence Aloft

  29. Divergence occurs downwind of an upper-level trough and upwind of an upper-level ridge DIVERGENCE ALOFT H

  30. UP DIVERGENCE ALOFT POLAR JET NORTHEAST SOUTHWEST

  31. UP POLAR JET MASS REMOVAL NORTHEAST SOUTHWEST

  32. TROPOPAUSE PREVENTS VERTICAL MOTION UP POLAR JET MASS REMOVAL NORTHEAST SOUTHWEST

  33. TROPOPAUSE PREVENTS VERTICAL MOTION UP POLAR JET MASS PULLED UP FROM BELOW TO REPLACE MASS REMOVED BY DIVERGENCE ALOFT NORTHEAST SOUTHWEST

  34. TROPOPAUSE PREVENTS VERTICAL MOTION UP POLAR JET UPWARD VERTICAL MOTION IS INDUCED NORTHEAST SOUTHWEST

  35. TROPOPAUSE PREVENTS VERTICAL MOTION UP POLAR JET MASS REMOVAL NORTHEAST SOUTHWEST

  36. TROPOPAUSE PREVENTS VERTICAL MOTION UP POLAR JET LESS MASS = PRESSURE FALLS NORTHEAST SOUTHWEST

  37. TROPOPAUSE PREVENTS VERTICAL MOTION UP POLAR JET L AREA OF LOW PRESSURE ON SURFACE NORTHEAST SOUTHWEST

  38. TROPOPAUSE PREVENTS VERTICAL MOTION UP POLAR JET H L H HIGHER PRESSURE ON ALL SIDES NORTHEAST SOUTHWEST

  39. TROPOPAUSE PREVENTS VERTICAL MOTION UP POLAR JET TOP OF ATMOSPHERIC BOUNDARY LAYER H L H NORTHEAST SOUTHWEST

  40. TROPOPAUSE PREVENTS VERTICAL MOTION UP POLAR JET TOP OF ATMOSPHERIC BOUNDARY LAYER H L H FRICTION PRESENT: WIND CROSSES TO LOWER PRESSURE NORTHEAST SOUTHWEST

  41. TROPOPAUSE PREVENTS VERTICAL MOTION UP POLAR JET TOP OF ATMOSPHERIC BOUNDARY LAYER H L H LOW-LEVEL CONVERGENCE NORTHEAST SOUTHWEST

  42. UP DIVERGENCE ALOFT POLAR JET UPWARD VERTICAL MOTION (CHIMNEY) L LOW-LEVEL CONVERGENCE NORTHEAST SOUTHWEST

  43. Chimney SURFACE

  44. Low Pressure Systems • Also called cyclones • Associated with stormy weather • Counterclockwise circulation in the Northern Hemisphere • Upper-level divergence • Rising motions • Low-level convergence • Often have fronts associated with them

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