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NCAR/ATD October 1, 2002

NCAR/ATD October 1, 2002. Frost-point hygrometer observations in the tropical upper troposphere and lower stratosphere: The troposphere/stratosphere interface. Holger Vömel University of Colorado, CIRES and NOAA/CMDL. Overview. Motivation Instruments and campaigns

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NCAR/ATD October 1, 2002

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  1. NCAR/ATD October 1, 2002 Frost-point hygrometer observations in the tropical upper troposphere and lower stratosphere: The troposphere/stratosphere interface Holger Vömel University of Colorado, CIRES and NOAA/CMDL

  2. Overview • Motivation • Instruments and campaigns • Observations of water vapor and ozone • Convective dehydration • Non-convective dehydration • Wave-driven dehydration • Absence of dehydration • Secondary dehydration • Transition layer • What happens in the tropical tropopause region • Summary

  3. Motivation: Stratospheric water vapor trend Location: Boulder, CO Period: 1980-2002

  4. Motivation: Radiative effects Average temperature response of a GCM to the 1979-1997 stratospheric water vapor trends From Forster and Shine, Geophys. Res. Lett., 1999

  5. Motivation: zonal picture From Holton et al., Rev. Geophys. 1995

  6. Tropopause definitions

  7. The NOAA frost-point hygrometer • Vertical Range: • Lower troposphere to 28 km • Sensitivity: • Detection limit < 0.7 ppmv • Accuracy : 10% • Weight: • 5 lbs • (6lbs with ozone sonde)

  8. The NOAA frost-point hygrometer • Cryogenic cooling • Linear controller • Temperature controlled and compensated optics

  9. NOAA hygrometer:Particle intercomparison

  10. Tropical frost-point soundings

  11. Deep convective profile • Saturation up to tropopause • Low ozone close to tropopause

  12. Deep convective signature • Saturation close to tropopause • Low ozone close to tropopause • No saturation throughout lower and middle troposphere

  13. Stratospheric drain From Sherwood. Geophys. Res. Lett.. 2000 Observational result: “Reverse” Walker circulation Gage et al., Science 1991

  14. Convective profile, particle signature

  15. Non convective dehydration • Saturation in upper troposphere • High ozone in upper troposphere • Very dry lower and middle troposphere

  16. Non convective profile: La Niña • Saturation in upper troposphere • High ozone in upper troposphere • No saturation throughout lower and middle troposphere

  17. Non convective profile: El Niño • Saturation in upper troposphere • High ozone in upper troposphere • No saturation throughout lower and middle troposphere • Low ozone extends to higher altitude

  18. Outgoing longwave radiation From Nishida et al., J. Meteorol. Soc. Jap., 2000

  19. Tropopause temperature (GPS/MET) From Nishida et al., J. Meteorol. Soc. Jap., 2000

  20. Kelvin wave event: Water, ozone 150 ppb 6 ppm

  21. Kelvin wave event: RH, ozone

  22. Kelvin wave event: Ozone, temperature 100 ppbv level Tropopause

  23. Kelvin wave: ECMWF 100 hPa temperature Eastward propagating disturbance, 90ºW = San Cristóbal From Fujiwara et al., Geophys. Res. Lett., 2001

  24. No dehydration, warm season

  25. Mean tropopause properties, Galapagos Tropopause mean: radiosonde data 1991-2002

  26. No dehydration, cold season

  27. Mean tropopause properties, Brazil Tropopause mean: SHADOZ data 1998-2002

  28. Tropopause layer: Lapse rate, ozone Ozone soundings March

  29. Mean ozone profiles March San Cristóbal, Galapagos March 1998: El Niño March 1999: La Niña

  30. RH in the TTL: cold season

  31. RH in the TTL: warm season

  32. RH in the TTL: tropical eastern Brazil

  33. Development of the hygropause Tropopause—> Tropopause—> Tropopause—> Tropopause—> Tropopause—>

  34. Summary: Longitudinal sketch From Vömel et al., J. Geophys. Res., 2002

  35. Summary • Longitudinal cross section of the equatorial region: • Convective dehydration • Non-convective dehydration • Wave driven dehydration • Absence of dehydration • All processes have a strong seasonal cycle and different geographic distribution • Minimum in RH can indicate the lower boundary of the tropopause transition layer • Secondary dehydration in November/December

  36. The Meteolabor SnowWhite sonde • Vertical Range: • Lower troposphere to tropopause (?) • Sensitivity: • Frost-point depression  36°C • Accuracy 0.1 °C (company spec.) • Launch Restrictions: • Night for highest range • Can’t pass rain clouds • Contamination: • Minimal on ascent (?)

  37. The Meteolabor SnowWhite sonde

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