A Possible Role for Immersion Freezing in Mixed-phase Stratus Clouds. Gijs de Boer T. Hashino, G.J. Tripoli, and E.W. Eloranta

Transcription

1 A Possible Role for Immersion Freezing in Mixed-phase Stratus Clouds Gijs de Boer T. Hashino, G.J. Tripoli, and E.W. Eloranta

2 Introduction EUREKA BARROW HSRL/MMCR combination - Barrow (8/04-11/04) M-PACE (Verlinde, 2007) - Eureka (8/06-Present) SEARCH

3 Introduction Lidar 2ackscatter cross section &Masked 8alues s9o:n in 2lack and :9ite( )ltitude &km( <10 5<20 5<30 5<40 5<50 Time &'T( 1G&m str 1e!9 1e!8 1e!F 1e!6 1e!5 1e!4 1e!3

4 Introduction Data from Klein et al. (2008)

5 Ice Nucleation So, where does the ice come from? - Primary Ice Formation - Homogeneous nucleation (Pruppacher and Klett, 1997) - Condensation nucleation - Nucleation through free IN (Contact) (Deposition) - Immersion nucleation

6 Ice Nucleation So, where does the ice come from? - Secondary Ice Formation - Multiplication mechanisms - Drop shattering: (Pruppacher and Klett, 1997) - Ice-Ice Collisions: - Splinter ejection during riming (Hallett-Mossop, 1974)

7 Ice Nucleation Ice concentrations often significantly exceed IN concentrations (Mossop, 1970; Beard, 1992) 10 4 IN vs. Ice Number Concentration (10/09/04 Barrow, AK) 1DC+2DC Ice Particle Concentration (1/L) !2 10!4 10!4 10! CFDC IN Concentration (1/L) Data courtesy of Greg McFarquhar and Gong Zhang

8 Ice Nucleation So, where does the ice come from? Normalized # Homogeneous Freezing (< -35 C) (Hagen et al., 1981; Jensen et al., 1998) Probability Density Function Cloud Min. Temp. Cloud Max. Temp. Splinter Ejection (> -8 C) (Heymsfield and Mossop, 1984) Temperature (K)

9 Immersion Freezing What about immersion freezing? Some Observational Evidence - Bigg (1980) observed sulfuric acid coating on aerosol particles during winter - Reduced IN activity with coating confirmed by Bertram and Girard in laboratory Image courtesy of J-P Blanchet - Blanchet (2007) hypothesizes that sulfur coating is a result of sulfur emissions from Siberia, and that resulting particles in Arctic have reduced ice nucleating ability.

10 Immersion Freezing What about immersion freezing? Some Observational Evidence From ground-based sensors: - Large increases in IWC in updrafts - Decrease in Liquid Fraction in updrafts Figure courtesy of M. Shupe (NOAA) From in-situ measurements: - Ice crystal concentrations strongly proportional to concentration of drops larger than 20 µm. (Rangno & Hobbs, 2001)

11 Conceptual Model: Immersion Freezing Initialization

12 Conceptual Model: Immersion Freezing Initialization

13 Conceptual Model: Immersion Freezing Initialization Mature Polar Cloud Working Group, 4th Pan-GCSS -- Toulouse, 2-6 June 2008

14 Conceptual Model: Immersion Freezing Initialization * Mature Polar Cloud Working Group, 4th Pan-GCSS -- Toulouse, 2-6 June 2008

15 Simulation t=10 min t=350 min t=700 min QC (Shaded), QI(contours): 07!May! :50:00 QC (Shaded), QI(contours): 07!May! :40:00!"#$%& :FD;E Z (km) Z (km) 0.475? >@ A; BC DE ED '()*+,-."#$%& QC (Shaded), QI(contours): 07!May! :10: Distance (km) /0"#12+3.3&4"/5#-6,*678)&9":;!<+=!>??@">A9B:9:: Distance (km) /0"#12+3.3&4"/5#-6,*678)&9":;!<+=!>??@"A:9B:9:: Z (km) 0.475!"#$%& :FA;B!"#$%& :FB;E Distance (km)? >@ C; DE AB BA '()*+,-."#$%&? >@ A; CD BE EB '()*+,-."#$%& (g/kg)

16 Summary - Nucleation of ice appears to control amount of liquid in mixed-phase stratus - In-Situ and remotely-sensed observations provide evidence for possibility of immersion freezing - Simulations reveal early hints at possibility of controlled nucleation through immersion freezing

17 References Beard, K.V., 1992: Ice Initiation in Warm-Base Convective Clouds: An Assessment of Microphysical Mechanisms, Atmos. Res., 28, Bigg, E.K., 1980: Comparison of Aerosol at Four Baseline Atmospheric Monitoring Stations, J. Appl. Met., 19, Blanchet, J-P, E. Girard, C. Jones, P. Grenier, R. Munoz-Alpizar, P. Du, C. Stefanof, A. Stefanof, and D. Simjanovski, 2007: Arctic Regional Climate Modelling: GEM-Arctic, the DGF Process and CloudSat- CALIPSO New Perspective, Polar Snow Hydrology Mission Workshop, Montreal, Canada. Fridlind, A.M., A.S. Ackerman, G. McFarquhar, G. Zhang, M.R. Poellot, P.J. DeMott, A.J. Prenni and A.J. Heymsfield, 2007: Ice Properties of Single-Layer Stratocumulus during the Mixed-Phase Arctic Cloud Experiment (M-PACE): Part II, Model Results, J. Geophys. Res., In Preparation. Hagen, D.E., R.J. Anderson, and J.L. Kassner, 1981: Homogeneous Condensation Freezing Nucleation Rate Measurements for Small Water Droplets in an Expansion Cloud Chamber. J. Atmos. Sci., 38, Hallett, J., and S.C. Mossop, 1974: Production of Secondary Ice Particles During the Riming Process, Nature, 249, Jensen, E.J., and Coauthors, 1998: Ice Nucleating Processes in Upper Tropospheric Wave-Clouds Observed During SUCCESS. Geophys. Res. Lett., 25, Klein, S., and Coauthors, 2008: Intercomparison of Model Simulations of Mixed-Phase Clouds Observed During the ARM Mixed-Phase Arctic Cloud Experiment, Part 1: Single Layer Cloud. Submitted to Quart. Roy Meteorol. Soc. Mossop, S.C., 1970: Concentrations of ice crystals in clouds. Bull. Amer. Meteorol. Soc., 51, Pruppacher, H.R., and J.D. Klett, 1997: Microphysics of Clouds and Precipitation, Springer. Rangno, A.L., and P.V. Hobbs, 2001: Ice Particles in Stratiform Clouds in the Arctic and Possible Mechanisms for the Production of High Ice Concentrations, J. Geophys. Res., 106, Verlinde, J., and Coauthors, 2007: The Mixed Phase Arctic Cloud Experiment, Bull. Amer. Meteo. Soc., 88,