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NASA CMAI Workshop April 20-21, 2006
Modeling Studies of Modeling Studies of Aerosol-Cold Cloud InteractionsAerosol-Cold Cloud Interactions
Sonia M. Kreidenweis and Paul J. DeMottSonia M. Kreidenweis and Paul J. DeMottDepartment of Atmospheric ScienceDepartment of Atmospheric Science
Colorado State UniversityColorado State University
NASA CMAI Workshop April 20-21, 2006
MotivationMotivation• Aerosol indirect effects on climate
– Includes effects on mixed and ice phase clouds… but these are poorly understood [IPCC TAR]
• For warm clouds, and homogeneous freezing processes, aerosol effects depend on size distribution, number concentration, composition– Probably true for ice formation at warmer
temperatures
• Models will need to move toward representation of aerosol sources, sinks, and key characteristics
NASA CMAI Workshop April 20-21, 2006
Assessing ice nuclei (IN) concentrations, their variability, their Assessing ice nuclei (IN) concentrations, their variability, their sources, and their role in cloud ice formationsources, and their role in cloud ice formation
Measurement of IN in the Measurement of IN in the field and in the labfield and in the lab
Evidence for relation of IN Evidence for relation of IN to ice in cloudsto ice in clouds
IN variability in atmosphere? IN variability in atmosphere? Why? Does it matter?Why? Does it matter?
Improve Improve representation of representation of
cold cloud cold cloud formation in formation in
climate modelsclimate models
NASA CMAI Workshop April 20-21, 2006
What ice nucleation mechanisms do we measure?What ice nucleation mechanisms do we measure?
Yes
YesYes/maybe
No, but…
Aerosols nucleate ice by varied mechanisms, most depending on T, some on RH as well
No instrument yet capable of measuring all mechanisms
What can a CFDC measure?
NASA CMAI Workshop April 20-21, 2006
What can be improved in models?What can be improved in models?• Newer and more observations of IN now available to revisit prior
parameterizations
• Also clear that IN must be prognostic
– evidence that ice doesn’t form in depleted air masses
• Certain aerosol types (dust, metallic particles) and certain sizes appear to be more active IN
NASA CMAI Workshop April 20-21, 2006
What can be improved in models?What can be improved in models?• For solution droplets, the theory of Koop et al. (2000) predicts that
homogeneous freezing occurs at a defined aw(T)
• We have developed methods for converting hygroscopic growth data into solution water activity data (example below is for levoglucosan, a compound in wood smoke)
– Already applied to prediction of CCN activity
• If models carry soluble particle type, and information on hygroscopicity, homogeneous freezing can be predicted
0.9
1
1.1
1.2
1.3
1.4
1.5
1.6
1.7
1.8
30 40 50 60 70 80 90 100RH (%)
GF
HTDMA
fit to GF data
Mochida and Kawamura (2004)
0.8
0.82
0.84
0.86
0.88
0.9
0.92
0.94
0.96
0.98
1
0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00x (%)
water activity
NASA CMAI Workshop April 20-21, 2006
Proposed WorkProposed Work
1. Build parcel models for aerosol-cloud interactions a. Begin with Feingold et al. (1998) aerosol-warm cloud model
and Young (1974) model
b. Modifications to include the ice phase, incorporating our lab and field data
c. Run as adiabatic parcel or from saved histories
2. Develop parameterizations for CRMs and GCMs to replace saturation-adjustment schemes
a. Implement and test through CMAI structure
3. Make models available through web interface
NASA CMAI Workshop April 20-21, 2006
Seeking correlation of IN with larger aerosol Seeking correlation of IN with larger aerosol using a variety of data setsusing a variety of data sets
r2 = 0.7526
NASA CMAI Workshop April 20-21, 2006
Examining cumulative distribution of [IN] and Examining cumulative distribution of [IN] and sampling conditions in many projectssampling conditions in many projects
Increasing dust Increasing dust particle impactsparticle impacts
MPACE: Arctic Fall FIRE-ACE: Arctic Spring
INSPECT-2: Western U.S. SpringCRYSTAL-FACE: Florida July
NASA CMAI Workshop April 20-21, 2006
Parcel ModelParcel Model
• Each parcel initialized with thermodynamic fields and aerosol size distributions, composition, hygroscopicity, ice forming characteristics (onset conditions [T, RH] for homogeneous freezing and for heterogeneous freezing, if applicable)
LES simulationof marine stratus
Run ensemble of parcels using trajectories & analyze for cloud particle characteristics
NASA CMAI Workshop April 20-21, 2006
Sample interfaceSample interface
NASA CMAI Workshop April 20-21, 2006
Specific “framework” activitiesSpecific “framework” activities
• Implement and test parameterization ideas across the whole range of models• We contribute one model type to the investigation
encompassing multiple model types• As suggested in the White Paper, analyze results to
make link to larger-scale models more explicit
• Help define observational tests for comparing process representation at all scales• Threshold conditions for glaciation; precip onset?• Mean particle size, IWC• CloudSat / CALIPSO
NASA CMAI Workshop April 20-21, 2006
Specific “support” elements to be usedSpecific “support” elements to be used
• Any trajectory data generated by other investigators
• Datasets produced for observational tests of model physics and performance
• Liaison team support for optimization of parameterizations
NASA CMAI Workshop April 20-21, 2006
ExtraExtra
NASA CMAI Workshop April 20-21, 2006
How do we measure IN and interpret the data?How do we measure IN and interpret the data?
NASA CMAI Workshop April 20-21, 2006
In deeper and mostly ice phase clouds: In deeper and mostly ice phase clouds:
400
500
600
700
800
900
1000
-30 -20 -10 0 10
TAMB
TCFDC400
500
600
700
800
900
1000
-30 -20 -10 0 10
TAMB
TCFDC
Secondary ice formation or sampling issue?
Closest correspondence between ice and IN from CVI residuals Closest correspondence between ice and IN from CVI residuals occurs only in upper regionoccurs only in upper region
Nov. 19, 2003
NASA CMAI Workshop April 20-21, 2006
Some cases for IN = primary initial ice formation: Some cases for IN = primary initial ice formation: studies in/around orographic wave cloudsstudies in/around orographic wave clouds
(WAVEICE, CO-WY, Wyoming King Air, March 2000)
(Rogers and DeMott, 2002 AMS Conf. Cloud Phys.)
IN
NASA CMAI Workshop April 20-21, 2006
Some evidence that presence or absence of ice in Some evidence that presence or absence of ice in clouds is linked to the availability of ice nuclei clouds is linked to the availability of ice nuclei
(AIRS-2, Ontario/Quebec, NCAR C-130, Nov. 2003)(AIRS-2, Ontario/Quebec, NCAR C-130, Nov. 2003)
IN by CFDC from CVI cloud particle residuals
CFDC processing temperature approximately equal to cloud temperature
NASA CMAI Workshop April 20-21, 2006
Great difficulty assigning true ice crystal Great difficulty assigning true ice crystal concentrations based on particle probe dataconcentrations based on particle probe data
NASA CMAI Workshop April 20-21, 2006
Measuring ice nuclei: Continuous flow Measuring ice nuclei: Continuous flow diffusion chamber (CFDC)diffusion chamber (CFDC)
OPC
0.3 1.5 m
aerosolaerosol Activated INActivated IN
NASA CMAI Workshop April 20-21, 2006
heated inlet heated inlet (ambient sample)(ambient sample)
Interior tubing and transfer to Interior tubing and transfer to other aerosol instrumentsother aerosol instruments
CVI inlet CVI inlet (residual (residual particles particles from from evaporated evaporated cloud cloud particles)particles)
Sampling involves inlets and their potential effects Sampling involves inlets and their potential effects on the nuclei we are trying to measureon the nuclei we are trying to measure
CFDCCFDC
CCNCCN
NASA CMAI Workshop April 20-21, 2006
Future plans – PACDEX with HIAPER Future plans – PACDEX with HIAPER aircraft (April-May 2007)aircraft (April-May 2007)
Goal: Dust-pollution effects on clouds and radiation following from near-source across ocean. Includes IN measurements.
NASA CMAI Workshop April 20-21, 2006
Future opportunity – ICE-L (Ice in Clouds Experiment – Future opportunity – ICE-L (Ice in Clouds Experiment – Layer clouds) with NCAR C-130 aircraft (March-April 2007)Layer clouds) with NCAR C-130 aircraft (March-April 2007)
Altostratus/altocumuli
Wave clouds
Goal: Identify ice formation mechanisms in clouds, Includes aerosol, IN, CCN measurements.
International Ice Nucleation Workshop: AIDA cloud chamber
facility (Karlsruhe, Germany), Summer or Fall 2007, Several
new instruments
NASA CMAI Workshop April 20-21, 2006
IN variability in atmosphere? Why? Does it matter?IN variability in atmosphere? Why? Does it matter?
NASA CMAI Workshop April 20-21, 2006
IN relations to aerosols have been explored during IN relations to aerosols have been explored during sampling periods at mountaintop laboratorysampling periods at mountaintop laboratory
SPL: Storm Peak Laboratory, 3.2km MSL, SPL: Storm Peak Laboratory, 3.2km MSL, Steamboat Springs, COSteamboat Springs, CO
INSPECT (Ice Nuclei INSPECT (Ice Nuclei Spectroscopy) I,II – Fall 2001, Spectroscopy) I,II – Fall 2001, Spring 2004Spring 2004
NASA CMAI Workshop April 20-21, 2006
IN relation to dust particles is clear, which may IN relation to dust particles is clear, which may explain IN-aerosol size relation (most times!)explain IN-aerosol size relation (most times!)
Timeline of global aerosol model dust Timeline of global aerosol model dust mass concentration, measured aerosol mass concentration, measured aerosol volume, and IMPROVE dust mass volume, and IMPROVE dust mass concentration (April to May 2004)concentration (April to May 2004)
Timeline of IN concentration and Timeline of IN concentration and aerosol particle concentration in aerosol particle concentration in the 300 to 700 nm size range.the 300 to 700 nm size range.
Heavy pollution event
NAAPS model results courtesy of Doug Westphal, NRL, Monterrey).
µg
m-3
µm3 cm-3
µg
m-3
Per std liter
cm-3
NASA CMAI Workshop April 20-21, 2006
Relation apparent between larger aerosol and IN from Relation apparent between larger aerosol and IN from mixed-phase cloud residual particlesmixed-phase cloud residual particles
Nov. 19, 2003
Appear related
Appear not related
NASA CMAI Workshop April 20-21, 2006
A case for IN impacting Arctic cloudiness during a A case for IN impacting Arctic cloudiness during a dust-poor scenario: M-PACE (October 2004)dust-poor scenario: M-PACE (October 2004)
Prenni et al. (2006)Prenni et al. (2006)
Observed cloudiness
Cloud model (RAMS) with “global” IN allowed to “deplete”
North Slope AlaskaIN
measured
“Global” IN function often assumed (Meyers et al.)
Cloud modeled with observed IN allowed to “deplete”
Knowing IN concentrations was critical to predicting cloud presence, phase, liquid water path, and surface net infrared radiation. Allowing the nuclei to be redistributed and used up was also very important.
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