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

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


Overview of today s talk
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


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

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


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

Sampling methodologies

aircraft aerosol sample inlet

CVI inlet (aerosol from evaporated cloud particles)

Ground-based aerosol sample inlet, Brazil

DOE AWG


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

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


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


Projects relating in to aerosol
Projects Relating IN to Aerosol frontal clouds during Pacific Dust Experiment (PACDEX;17 May 2007)

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Ice nuclei concentrations
Ice nuclei concentrations frontal clouds during Pacific Dust Experiment (PACDEX;17 May 2007)

  • 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


Ice nuclei concentrations1
Ice nuclei concentrations frontal clouds during Pacific Dust Experiment (PACDEX;17 May 2007)

DOE AWG


Strong in dependence on aerosol concentrations in selective size and temperature range 32 2 c
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


Size and temperature dependence in all cfdc projects can be parameterized
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


All data predicted versus measured
All Data: Predicted versus Measured parameterized

Param. predicts ~2/3 data within factor 2

MOCA-2009


Ice nucleation parameterizations
Ice nucleation parameterizations parameterized

  • 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


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

Single column model (SCAM3) simulation of parameterizedM-PACE Arctic Stratus

Observations 

Ice water content

Cloud water content

Liu et al. 2-moment microphys. + Meyers 

As above new param

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Global model cam3 5 year simulations annual averages
Global model (CAM3) 5-year simulations, annual averages parameterized

Total liquid water path

Total ice water path

Total cloud cover

DOE AWG

Boulder, CO


Summary
Summary parameterized

  • 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


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

Project average IN parameterizedvs 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