Institute for Climate and Atmospheric Science

1. Institute for Climate and Atmospheric Science MOGUL Meeting – Feb 28, 2013 • Balloons, waves and cirrus in the tropics • Steven Dobbie • Institute for Climate and Atmospheric Science • University of Leeds Sardar Al-Jumur Benjamin Murray, Theodore Wilson, Zhiqiang Cui Ottmar Möhler, Martin Schnaiter, Robert Wagner, Stefan Benz, Monika Niemand, Harald Saathoff, Volker Ebert, Steven Wagner and Bernd Kärcher Neil Gordon

2. Institute for Climate and Atmospheric Science Balloons, waves and cirrus in the tropics

3. Institute for Climate and Atmospheric Science What is interesting about TTL region? Ice supersaturations frequently exceed 100% Rhi (Jensen et al, 2005; Peter et al., 2006). Is something inhibiting the formation of cirrus?

4. Institute for Climate and Atmospheric Science What is interesting about thin TTL cirrus? High in-cloud supersaturations and low ice number concentrations (Kramer et al., 2009) Why aren’t high supersaturations in cloud being quenched?

5. Institute for Climate and Atmospheric Science “Supersaturation puzzle”

6. Institute for Climate and Atmospheric Science • Source of supersaturation • As air rises the air cools and RHice rises • Sink of supersaturation • As RHice rises vapour deposits on ice crystals present

7. Institute for Climate and Atmospheric Science • Homogeneous nucleation results in numerous crystals of small size so RHice is quenched quickly • Heterogeneous nucleation results in few crystals of larger size and RHice is slower to quench. • Numbers of traditional IN are too few

8. Institute for Climate and Atmospheric Science

9. Institute for Climate and Atmospheric Science

10. Institute for Climate and Atmospheric Science • What is up there? • Froyd et al 2010:

11. Institute for Climate and Atmospheric Science Candidates? • Mineral dust? • Low numbers • “Even if all mineral dust nucleated they couldn’t explain the ice numbers” (Froyd et al 2010)

12. Institute for Climate and Atmospheric Science What if? What if some of the numerous solution aerosols were nucleating at lower super-saturations—below water saturation?

13. Institute for Climate and Atmospheric Science Candidates? Sulphates crystallise in low relative humidity conditions. - numbers are high - solid so could act as an ice nuclei?

14. Institute for Climate and Atmospheric Science Candidates? - Sulphates are too viscous at TTL conditions to crystallise (Bodsworth et al., 2010)

15. Institute for Climate and Atmospheric Science Candidates? • Very low accommodation coefficient (0.0075) and so slow uptake of water vapour? (Magee et al., 2006) • Recent work by Skrotzki (2012) shows it is > 0.1

16. Institute for Climate and Atmospheric Science Candidates? What else could be solid and act as an IN at low temperatures?

17. Institute for Climate and Atmospheric Science Glassy aerosols ”Temperature at which materials change from hard and brittle to soft and pliable” “The temperature below which an amorphous material is a glassy solid and above which it is a viscous liquid“ Murray et al., 2008 and Zobrist et al., 2008 Previously not thought to be applicable to troposphere but is relevant for TTL. Thought to potentially inhibit nucleation

18. Institute for Climate and Atmospheric Science Laboratory glassy aerosols Brittle glassy aerosol T / RHi decreasing

19. Institute for Climate and Atmospheric Science Brittle glassy aerosol Liquid solution aerosol T / RHi increasing

20. Institute for Climate and Atmospheric Science AIDA Chamber, Karlsruhe • Aqueous citric acid, • Raffinose/M5AS, • Levoglucosan, • HMMA • it has similar functionality to oxygenated organic compounds known to exist in atmospheric aerosols; • its glass forming properties are similar to a range of other atmospherically relevant aqueous organic solutions and aqueous organic-sulphate mixtures; and • Representative of products found in the atmosphere.

21. Institute for Climate and Atmospheric Science • What did the AIDA results show for glassy behaviour during nucleation?

22. Institute for Climate and Atmospheric Science AIDA results: Above 212K (non-glassy regime) Below 212K (glassy regime)

23. Institute for Climate and Atmospheric Science AIDA results: Above 212K (non-glassy regime) Below 212K (glassy regime)

24. Institute for Climate and Atmospheric Science Modelling results 1-D APSC (Karcher, DLR) runs:

25. Institute for Climate and Atmospheric Science APSC results: Constant uplift b) Glassy

26. Institute for Climate and Atmospheric Science APSC results: Citric acid/constant uplift

27. Institute for Climate and Atmospheric Science APSC results: Raffinose/M5AS

28. Institute for Climate and Atmospheric Science IN indirect response

29. Institute for Climate and Atmospheric Science Glassy indirect effect

30. Institute for Climate and Atmospheric Science

31. Institute for Climate and Atmospheric Science Forced by single waves: het/glassy

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33. Institute for Climate and Atmospheric Science Forced by observed superposition of waves: (Jensen and Pfister, 2004)

34. Institute for Climate and Atmospheric Science Deposition coefficient sensitivity

35. Institute for Climate and Atmospheric Science High altitude balloon observations(Hertzog et al., LMD) - 2-3 months floating around in the tropics advected on constant density surfaces - measuring temperature and pressure

36. Institute for Climate and Atmospheric Science High altitude balloon (LMD; Hertzog et al) - 2-3 months floating around in the tropics advected on constant density surfaces - measuring temperature and pressure

37. Institute for Climate and Atmospheric Science Balloon trajectory Hertzog et al

38. Institute for Climate and Atmospheric Science Temperature variations

39. Institute for Climate and Atmospheric Science Het (glassy) model run

40. Institute for Climate and Atmospheric Science

41. Institute for Climate and Atmospheric Science Hom activated

42. Institute for Climate and Atmospheric Science Optical depth

43. Institute for Climate and Atmospheric Science Cloud lifetime Hom Glassy

44. Institute for Climate and Atmospheric Science Radiative properties

45. Institute for Climate and Atmospheric Science Satellite observations Can we obtain remote sensing at the location of the balloon?

46. Institute for Climate and Atmospheric Science Satellite observations

47. Institute for Climate and Atmospheric Science MLS – AURA CALIPSO - Lidar

48. Institute for Climate and Atmospheric Science • Conclusions • Experiments: • A range of common organics and organic/sulphate mixtures become glassy and nucleate ice heterogeneously • Modelling: • Modelling results using glassy aerosols are consistent with observed high in-cloud super-saturations and low ice number concentrations • Modelling agree for ice number, RHi, optical depth, heating rates, etc.

49. Institute for Climate and Atmospheric Science • Conclusions • Modelling: • Consistency for both constant lifting and gravity waves forcings • Strong potential indirect response with glassy nucleation • Suppression of ice number • Shorter lifetime • Heterogeneous nucleation mechanism is needed to explain observations.

50. Institute for Climate and Atmospheric Science • Next steps • Remote sensing: • Frequency of cloud: average the cloud occurrence from Calipso that are detached, at TTL heights, and close to balloon. • Launch a balloon with humidity, particle counters, etc.