1. Aerosols effects on turbulence in mixed- phase deep convective clouds investigated with a 2D cloud model with spectral bin microphysics The 26th Annual Meeting of the Israeli Association of Aerosol Research Aerosols effects on turbulence in mixed- phase deep convective clouds investigated with a 2D cloud model with spectral bin microphysics The 26th Annual Meeting of the Israeli Association of Aerosol Research Nir Benmoshe, Alexander Khain Atmospheric science department The Hebrew University in Jerusalem

2. Cloud in real life

3. HUCM A 2D cloud model with 43 bins spectral bins 7 different hydrometeors type Aerosols Diffusional growth, collision, freezing, melting, advection Model resolution of 50 m x 50 m was used.

4. Droplet fall and collisions in non-turbulent air

5. Formation of eddies Absolute velocitiesRelative velocities

6. Physical mechanisms of effects of turbulence on collisions Formation of relative velocity between particles and environment Formation of concentration inhomogeneity (droplet clustering)

7. Swept volumeCollision efficiencyFluctuations of concentration is the collision kernel References: Saffman and Turner (1956); Khain and Pinsky, 1995; Pinsky and Khain, 1996,1997a,b; Pinsky et el, 2000, 2001; Zhou et al, 1998; Wang et al, 1998, 2000; Elperin and Dodin, 2012 References: Maxey, 1987, Wang and Maxey, 1993; Pinsky et al. 1997; 1999, Pinsky and Khain 2001, 2003. Shaw et al, 1998; Shaw and Kostinsky 2003; Elperin et. al 1996; 1998, 2002 Falkovich et al, 2001, 2002; References: Pinsky et al, 1999, 2000; 2001; 2004; 2008 Khain et al, 2000; Pigeonneau and Feuillebois, 2002 Wang et al, 2004; Ayala et al 2010 How does turbulence influence droplet collisions? Benmoshe et al. (2012)  combined effect of all factors

8. Mean normalized collision kernel in turbulent flow for three cases: stratiform clouds (left panel), cumulus clouds (middle) and cumulonimbus (right panel). Pressure is equal to 1000mb. (After Pinsky et al, 2008) Stratocumulus Cumulus Cumulonimbus Collision rate enhancement is determined by two parameters : eps and Re Collision kernel enhancement factors for different dissipation rates and Reynolds numbers

9. Novel approach for calculation of collisions: a)Calculation of dissipation rate in each grid point at each time step b)Calculation of Reynolds number in each grid point at each time step; c)Calculation of collision enhancement factor in each grid point at each time step This method makes it possible to investigate effects of turbulence on precipitation formation.

10. Turbulence kinetic energy equation Calculation of dissipation rate Benmoshe et al. (2012) Dissipation rate cm^2/sec^3

11. Calculating Taylor microscale Characteristic velocity fluctuation Reynolds lambda L is the external turbulent scale Benmoshe et al. (2012)

12. Blue ocean - CCN concentration 200 cm -3 Green ocean – CCN concentration 700-900 cm -3 Smoky clouds - CCN concentration 5000-10000 cm -3 CASE STUDIES: LBA-SMOC FIELD EXPERIMENT Andreae et al, 2004

13. Turbulent structure of deep cumulus clouds

14. Turbulence properties Benmoshe et al. (2012)

15. spatial vs. averaged values

16. Aerosols effect on cloud turbulence

17. Accumulated rain: effects of turbulence and aerosols

18. Effect of turbulence on collisions in mixed-phase clouds

19. The turbulence effect on ice particles collision is larger than on water droplets Effects of turbulence on ice collisions should be larger because of lower sedimentation velocity at the same mass (inertia) von Blohn et.al. 2005 Nowell 2010

20. Pinsky, M.B., A.P. Khain, D. Rosenfeld and A. Pokrovsky, 1998 Increase in the collision kernel

21. EFFECTS WITH ENHANCED RIMING graupel CWC CONTROL

22. EFFECTS WITH ENHANCED RIMING Graupel, grav Graupel, turb Snow, grav Snow, turb CONTROL

23. Accumulated rain

24. High resolution of the model gives us real fractal cloud structures. This is the first time that time and spatial depended turbulence characteristics were calculated for cumulus clouds Turbulence in clouds is highly inhomogeneous: mean values do not reflect effects of turbulence on collisions Conclusions – turbulence structure Turbulent intensity in clouds increase in the presence of higher aerosols concentration Increase in the collision rate between droplets reduces the total amount of precipitation since it eventually weakens cold precipitation processes Turbulence substantially accelerates formation of warm rain, especially in polluted clouds. Turbulence in mixed phase clouds increases the rate of riming, mass and size of graupel and accelerates formation of cold rain

25. Questions ? Next time you are in an air pocket think about its good side….

26. Questions ?

27. Conclusions – effect of turbulence on precipitation First rain drops form in zones of enhance turbulence near cloud top Zones of enhance turbulence coincide with zones of high cloud water content. So, first rain drops form in undiluted cloud volumes where turbulence intensity is maximum. Maximum turbulence intensity is in the top area of the cloud bubbles

28. IMPORTANCE OF THE STUDY increasing the collision rate in highly turbulent clouds by order of the magnitude. increasing the collision rate in highly turbulent clouds by order of the magnitude. cloud turbulence determines processes of entrainment of dry air into the cloud and affects the cloud height. cloud turbulence determines processes of entrainment of dry air into the cloud and affects the cloud height. The knowledge of the cloud turbulence intensity is important for purposes of flights safety. The knowledge of the cloud turbulence intensity is important for purposes of flights safety. why the shape of DSD is wider than it is supposed to be according to the equation for the diffusion droplet growth (e.g., Brenguier and Chaumat, 2001) why the shape of DSD is wider than it is supposed to be according to the equation for the diffusion droplet growth (e.g., Brenguier and Chaumat, 2001) and why warm rain formation, as shown by Jonas (1996), occurs significantly faster than it is supposed to in accordance with the classical theory of gravitational coagulation. and why warm rain formation, as shown by Jonas (1996), occurs significantly faster than it is supposed to in accordance with the classical theory of gravitational coagulation. Pinsky et al 2008 tell how turbulence kernel effect a DSD Pinsky et al 2008 tell how turbulence kernel effect a DSD Falkovich et al (2002); Pinsky et al (1997a,b; 2008); Xue et al (2008); Wang and Grabowsky (2009), the authors presented solutions of the stochastic collision equation in which turbulent effects on the evolution of the initially given DSD were simulated. Falkovich et al (2002); Pinsky et al (1997a,b; 2008); Xue et al (2008); Wang and Grabowsky (2009), the authors presented solutions of the stochastic collision equation in which turbulent effects on the evolution of the initially given DSD were simulated.

29. סרטון של ענן מצולם So, what are we talking about

30. Previous work The mean kinetic energy dissipation rate in stratocumulus clouds (Sc) is estimated as (Siebert et al. 2006) and in small cumuli as (MacPherson and Isaac, 1977; Mazin et al 1989; Pinsky and Khain 2003). The mean kinetic energy dissipation rate in stratocumulus clouds (Sc) is estimated as (Siebert et al. 2006) and in small cumuli as (MacPherson and Isaac, 1977; Mazin et al 1989; Pinsky and Khain 2003). According to Panchev (1971) and Weil et al (1993), the values of measured in deep cumulus clouds range from several hundreds to. According to Panchev (1971) and Weil et al (1993), the values of measured in deep cumulus clouds range from several hundreds to. The recent measurements of the turbulent structure of the boundary layer using a helicopter (Siebert et al 2006) indicated dramatic spatial inhomogeneity of: while the typical mean values of are, in some zones of Sc clouds (possibly in zones of imbedded convection) the values of can increase up to. The recent measurements of the turbulent structure of the boundary layer using a helicopter (Siebert et al 2006) indicated dramatic spatial inhomogeneity of: while the typical mean values of are, in some zones of Sc clouds (possibly in zones of imbedded convection) the values of can increase up to. the typical values of were estimated by Pinsky et al (2007, 2008) as ranging from ~ in stratiform clouds to ~in strong deep convective clouds (Cb). the typical values of were estimated by Pinsky et al (2007, 2008) as ranging from ~ in stratiform clouds to ~in strong deep convective clouds (Cb). According to Siebert et al (2006), turbulent intensity varies dramatically within stratocumulus clouds. One can expect a high variability of and in cumulus and Cb clouds as well. According to Siebert et al (2006), turbulent intensity varies dramatically within stratocumulus clouds. One can expect a high variability of and in cumulus and Cb clouds as well. To our knowledge, there have been no regular measurements of the fine spatial distribution of and in deep cumulus clouds. To our knowledge, there have been no regular measurements of the fine spatial distribution of and in deep cumulus clouds. Turbulence determines small scale spatial fluctuations of the liquid water content (e.g., Spyksma and Bartello, 2008). Turbulence determines small scale spatial fluctuations of the liquid water content (e.g., Spyksma and Bartello, 2008). turbulence affects droplet size distributions (DSD) thus having an impact on diffusion growth/evaporation of drops (e.g., Jensen and Baker, 1989; Khvorostyanov and Curry 1999a,b). turbulence affects droplet size distributions (DSD) thus having an impact on diffusion growth/evaporation of drops (e.g., Jensen and Baker, 1989; Khvorostyanov and Curry 1999a,b).

31. Where are the first drops forms? X, km Height, km eps,1500sec,M 2 /S 3 2.557.51012.5 10.35 7.85 5.35 2.85 0.35 0.00 0.01 0.02 0.03 0.05 0.08 0.13 0.22 X, km Height, km RAIN DROP mass,1800sec,g/m 3 2.557.51012.5 10.35 7.85 5.35 2.85 0.35 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 X, km Height, km RAIN DROP mass,1500sec,g/m 3 2.557.51012.5 10.35 7.85 5.35 2.85 0.35 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 Rain water content, gm -3, t=1500s Rain water content, gm -3, t=1800s Dissipation rate, m 2 s -3, t=1500s X, km Height, km eps,1800sec,M 2 /S 3 2.557.51012.5 10.35 7.85 5.35 2.85 0.35 0.00 0.01 0.02 0.03 0.05 0.08 0.13 0.22 Dissipation rate, m 2 s -3, t=1800s X, km Height, km eps,1500sec,M 2 /S 3 2.557.51012.5 10.35 7.85 5.35 2.85 0.35 0.00 0.01 0.02 0.03 0.05 0.08 0.13 0.22 X, km Height, km RAIN DROP mass,1500sec,g/m 3 2.557.51012.5 10.35 7.85 5.35 2.85 0.35 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 Rain water content, gm -3, t=1500s Rain water content, gm -3, t=1800s Dissipation rate, m 2 s -3, t=1500s X, km Height, km eps,1800sec,M 2 /S 3 2.557.51012.5 10.35 7.85 5.35 2.85 0.35 0.00 0.01 0.02 0.03 0.05 0.08 0.13 0.22 Dissipation rate, m 2 s -3, t=1800s E200TE2000T

32. Data Size Distributions

33. How is the first precipitation influenced by turbulence ? GO-turb GO-grav S-turb S-grav Strange notations

34. R eff

38. Turbulence properties

39. Problems of formation of large cloud drops and rain formation: a)Diffusional growth is a slow process and cannot explain formation of droplets with radii exceeding about 22 um, needed for triggering of collisions; b)Pure gravitational collision rate is low, so formation of raindrops requires several hours (Jonas 1996) MOTIVATION PROBLEM OF RAIN FORMATION TIME 300  m 200  m 100  m 25  m 20 min40 min60 min condensation Classic evaluation of time of raindrop development: 60 min+60 min=120 min. Collisions In real clouds: 15 min Jonas, 1996

40. 1)Clouds are zones of enhanced turbulence. 2) There are no in situ data because it’s unsafe to fly in high turbulence areas 3) Can turbulence be an important factor accelerating formation of rain formation? 4) What is the dynamical structure of turbulent cloud? Where turbulence in cloud is most intense? 5) What is the effects of turbulence of drop size distribution? What is the combined effects of aerosols and turbulence? 6) How is lightning in clouds related to cloud turbulence? MOTIVATION

41. DSDs obtained by solving the stochastic collision equation during t=30 min Stratiform clouds Cu Cb Pinsky et. al., 2008

42. GOAL: analysis of turbulent effects on cloud microphysics using a spectral bin cloud model

43. Raindrop formation Effective radius, Mean volume – Effective radius relationship Ice particles droplets mm Mean volume radius, HUCM Freud and Rosenfeld, 2012 Effective radius, mm Mean volume radius, mm mm mm mm mm

44. Effect of turbulence on formation on first raindrops and on surface precipitation

45. Where do the first drops form?

46. First raindrops form in zones of enhanced turbulence <4km 4km -5km 5km<

47. More bubbles

48. Creation of each bubble