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Multi-project analyses of ice nuclei relation to aerosols and ice in clouds

Multi-project analyses of ice nuclei relation to aerosols and ice in clouds. 1 Colorado State University 2 Pacific Northwest National Laboratory

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Multi-project analyses of ice nuclei relation to aerosols and ice in clouds

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  1. Multi-project analyses of ice nuclei relation to aerosols and ice in clouds 1 Colorado State University 2Pacific Northwest National Laboratory Acknowledgments: NSF (various). DOE-ARM (Grant No. DE-FG02-09ER64772), NASA-MAP (Grant NNG06GB60G), NASA NIP (Prenni), DOE Climate Change Prediction Program, Cooperative Institute for Research in the Atmosphere, Dave Hudak, Ulrich Poeschl. Submitted to PNAS: DeMott, P.J. , A.J. Prenni, X. Liu, M.D. Petters, C.H. Twohy, M.S. Richardson, T. Eidhammer, S.M. Kreidenweis, D.C. Rogers, Predicting global atmospheric ice nuclei distributions and their impacts on climate. Anthony J. Prenni1 P. J. DeMott1 and X. Liu2 DOE AWG

  2. Overview of today’s talk • Measurement description • Do IN predict ice formation in clouds in the situations absent of secondary influences? • Database from almost a decade of ice nuclei (IN) measurements at surface sites and via aircraft. • Relations between aerosol properties and IN number concentrations in mixed phase clouds. • Some first applications toward global modeling studies. DOE AWG

  3. Real-time atmospheric measurement of IN - Continuous flow diffusion chamber (CFDC) * -6 < T < -40°C Total residence time ~6s OPC * PM1 contributes ~50% of IN number at -15 °C Santachiara, G., et al., Atmospheric particles acting as Ice Forming Nuclei in different size ranges, Atmos. Res. (2009), doi:10.1016/j.atmosres.2009.08.004 DOE AWG

  4. Sampling methodologies aircraft aerosol sample inlet CVI inlet (aerosol from evaporated cloud particles) Ground-based aerosol sample inlet, Brazil DOE AWG

  5. Ice in Clouds Experiment (ICE-L, 2007): Orographic wave clouds used as natural laboratories to study ice initiation CVI inlet sampling Radar/lidar profiling Ambient inlet sampling Case studies indicating IN ≈ Ice in clouds (Paul Field’s Presentation on Wednesday + submitted J. Atmos. Sci.; Eidhammer et al. 2009) DOE AWG

  6. Ice nuclei (CVI sample) versus ice concentration in warm frontal clouds during Pacific Dust Experiment (PACDEX;17 May 2007) Tamb ≈ -25°C TCFDC ≈ -25°C DOE AWG

  7. Projects Relating IN to Aerosol DOE AWG

  8. Ice nuclei concentrations • 5-30 min. averages • Processed from 100-105% RH • Processed from -10 °C to -35 °C • Limited to ~constant Temp (5 °C) and RH (3%) • Limited to ~constant altitude (500 m) • Clear air measurements only, except for ICE-L, where CVI residuals were also characterized DOE AWG

  9. Ice nuclei concentrations DOE AWG

  10. Strong IN dependence on aerosol concentrations in selective size and temperature range (-32±2°C) PACDEX project Berezinski et al. (1986), extrapolated -32°C Georgii and Kleinjung (1967), -21°C, > 0.6 mm DOE AWG

  11. Size and temperature dependence in all CFDC projects can be parameterized -30 to -35°C -25 to -30°C -20 to -25°C -10 to -20°C DOE AWG

  12. All Data: Predicted versus Measured Param. predicts ~2/3 data within factor 2 MOCA-2009

  13. Ice nucleation parameterizations • Meyers et al. (1992): nin= exp(12.96(Si-1)- 0.639) (no links to aerosol properties) • DeMott et al. (2009): ( T, naer>0.5mm diameter) a = 0.00001968 b = -0.0167(Tk-273.15) + 0.2877 Ice supersaturation dependence only DOE AWG

  14. Single column model (SCAM3) simulation of M-PACE Arctic Stratus Observations  Ice water content Cloud water content Liu et al. 2-moment microphys. + Meyers  As above new param DOE AWG

  15. Global model (CAM3) 5-year simulations, annual averages Total liquid water path Total ice water path Total cloud cover DOE AWG Boulder, CO

  16. Summary • Ice formation predicted by IN measurements in absence of homogeneous freezing and secondary ice nucleation. • IN concentrations in mixed-phase cloud regime relates to larger/coarse mode aerosol concentrations and temperature. • Global model simulation sensitivity to IN is quite strong using this information. • Studies of IN compositional dependencies continue • Will use ISDAC dataset to test parameterization DOE AWG

  17. Project average IN vs ice in clouds from FIRE-ACE/SHEBA (1998) and M-PACE (2004) ○ IN FIRE-ACE/SHEBA ● cloud ice FIRE-ACE/SHEBA □ IN M-PACE ■ cloud ice M-PACE Cloud ice based on 2D-C probe > 125 mm FIRE-ACE/SHEBA ice data: Gultepe et al., 2001 M-PACE ice data: McFarquhar et al., 2007 DOE AWG

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