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Meteorological analysis of SCAVEX flights

Meteorological analysis of SCAVEX flights. Peter van Velthoven. Overview of flights. 5-4-1: Stratosphere+low level clouds 11-4-1: Clouds northeast of trough (turning wind profile) 18-4-1: Stratosphere+cloud layer+perhaps outflow of uplift 25-4-1: Thin “f ö hn layer”, subsidence, lee waves

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Meteorological analysis of SCAVEX flights

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  1. Meteorological analysis of SCAVEX flights Peter van Velthoven

  2. Overview of flights • 5-4-1: Stratosphere+low level clouds • 11-4-1: Clouds northeast of trough (turning wind profile) • 18-4-1: Stratosphere+cloud layer+perhaps outflow of uplift • 25-4-1: Thin “föhn layer”, subsidence, lee waves • 2-5-1: EW, uninteresting?, some North African air • 3-5-1: Possibly föhn outflow, lee waves, air from West Atlantic and North African lowermost troposphere. • 4-5-1: Occasionally clouds? , some North African air • 11-4-2: Large scale uplift in cloud system over North Italy • 22-4-2: Profiles in frontal cloud band and trough (stratosphere) • 23-4-2: High cloud band • 24-4-2: EW flight below trough and through frontal clouds north of Alps (with southward winds).

  3. 5 April 2001: stratosphere + low level clouds

  4. 5 April 2001 North-south X-section at 11 E of cloud cover

  5. 5 April 2001: NOAA 14h23

  6. 11 April 2001: clouds northeast of trough

  7. X-section versus time of cloud cover 11 April 2001 10h11-12h39

  8. 11 April 2001 NS X-section of cloud coverat 10 Eprojection!

  9. 18 April 2001: stratosphere+deep cloud layer

  10. 18 April 2001: stratosphere+cloud layer Outflow north Italy?

  11. 25 April 2001: predicted föhn counteracted by subsidence

  12. 25 April 2001: predicted föhn was counteracted by subsidence • High clouds above aircraft • Thin ascending layer on southern slopes • Lee waves Vertical wind dp/dt (t)

  13. 2 May 2001 • Possible föhn counteracted by subsidence • East-west flight in large anticylone • Profile just up to tropopause • Some uplifted air from north Africa

  14. 3 May 2001: possible föhn, lee waves not enough high clouds föhn uplift lee waves North Italy Some air from West Atlantic and North African lowermost troposphere

  15. Relatively cloud free? Over north Italy ascent but no deep clouds, except occa-sionally? Air from the North Africa BL. 4 May 2001: NS flight to Italy North Italy profile

  16. 4 May 2001Occasionally clouds ... RH signature

  17. 4 May 2001: Air from the North African BL 300 hPa Pressure Trajectories 8h32-9h

  18. Large scale uplift in a cloud system over north Italy. Some air from North Africa at low levels over north Italy. 11 April 2002 North Italy

  19. 11 April 2002: Large scale uplift in a cloud system over north Italy. “Föhn index”

  20. IR -12 h Profiles in frontal cloud band and trough (stratosphere) 22 April 2002

  21. Wind from northeast, high cloud band 23 April 2002 IR 12h30 North Italy

  22. Below trough and frontal clouds 24 April 2002 IR 14h

  23. Northward föhn-like: Föhn index predictions • 18-4-2001 (northward flight, no profile in Italy, outflow?) • (25-4-2001+subsidence) • (2-5-2002+subsidence, east-west flight) • 3-5-2001 (evidence for föhn clouds and precipitation) • 11-4-2002 (interesting case) Southward föhn-like : • (5-4-2001, small winds in Alps, only northward flight) • 11-4-2001 (rather flow around Alps in LT, northward wind component at 300 hPa, southward component at 850 hPa .... hence complex case) • 24-4-2002 (east-west flight north of Alps)

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