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

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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.

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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

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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)

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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

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Projects relating in to aerosol

Projects Relating IN to Aerosol

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Ice nuclei concentrations

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

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Ice nuclei concentrations1

Ice nuclei concentrations

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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

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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

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All data predicted versus measured

All Data: Predicted versus Measured

Param. predicts ~2/3 data within factor 2

MOCA-2009


Ice nucleation parameterizations

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

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

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

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Global model cam3 5 year simulations annual averages

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

Total liquid water path

Total ice water path

Total cloud cover

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Boulder, CO


Summary

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

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

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

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