arctic aerosol research activities dorothy koch giss, columbia university
DESCRIPTION
Arctic Aerosol Research Activities Dorothy Koch GISS, Columbia University. Observations: ARCTAS 1. GEOS-5, MODIS: Chu, Rodriguez, da Silva 2. RSP: Cairns Global modeling of aerosols 3. Transport, HTAP: Shindell, Chin, et al. 4. Climate: Shindell - PowerPoint PPT PresentationTRANSCRIPT
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Arctic Aerosol Research ActivitiesDorothy Koch GISS, Columbia University
I.I. Observations: ARCTASObservations: ARCTAS
1. GEOS-5, MODIS: Chu, Rodriguez, da Silva1. GEOS-5, MODIS: Chu, Rodriguez, da Silva
2. RSP: Cairns2. RSP: Cairns
II.II. Global modeling of aerosolsGlobal modeling of aerosols
3. Transport, HTAP: Shindell, Chin, 3. Transport, HTAP: Shindell, Chin, et al.et al.
4. Climate: Shindell4. Climate: Shindell
5. Climate: Koch 5. Climate: Koch et al.et al.
III.III. Modeling of aerosol - cloud interactionsModeling of aerosol - cloud interactions
6. GCM: Menon 6. GCM: Menon et al.et al.
7. Cloud scale: Fridlind 7. Cloud scale: Fridlind et al.et al.
GSFC Aerocenter March 4, 2008
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GEOS-5 AOT on July 21, 2007
MODIS Terra on July 21, 2007ARCTAS – Arctic Research of the Composition of the Troposphere from Aircraft and SatellitesNASA field program based out of Fairbanks, AK (April 2008) and Cold Spring, Canada (June/July 2008) to study the transport pathways of atmospheric pollutants to the ARCTIC. GSFC: real-time aerosol and chemical forecasts with GEOS-5 model and near real-time satellite retrievals of aerosol properties from MODIS.
1. PI’s: Chu, Rodriguez, da Silva1. PI’s: Chu, Rodriguez, da Silva
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Summer ARCTAS deployment: focus on forest fires
Frequency and altitude of pyro-convection: from TOMS Aerosol Index (AI).• LIDAR is CPL from McGill/Hlavka
at GSFC• AI is TOMS from Fromm at NRL.
ARCTAS - Summer: Research Scanning Polarimeter (RSP)
2. Cairns2. Cairns
Lidar: CPLLidar: CPL
TOMS AITOMS AI
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• The Research Scanning Polarimeter (RSP is a proxy for APS on the NASA Glory mission) will fly on the same platform as the High Spectral Resolution Lidar (B200) during ARCTAS.
• Previous measurements have shown consistency between RSP retrievals of imaginary index, optical depth, size and aerosol top height with lidar (4.5 km) and TOMS AI (8.5).
• ARCTAS in situ measurements: evaluate RSP single scattering albedo. Lidar: evaluate determination of aerosol layer height.
ARCTAS - Summer
2. Cairns2. Cairns
Clear Smokey
RSP AOD
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HTAPShindell et al.: A multi-model assessment of pollution transport to the Arctic
European pollution dominates near the surface.Other regions (e.g. SE Asia more important at higher altitudes.
3. Shindell et al.3. Shindell et al.
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Shindell (GRL, 2007) Analyzed transient (1880-2000) simulations of Hansen et al. (2007), and found that Arctic surface air temperature changes correlate better to GLOBAL rather than LOCAL radiative forcings.
4. Shindell 4. Shindell
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Koch, D., S. Menon, A. Del Genio, I. Alienov, R. Ruedy, G. Schmidt, Distinguishing
Aerosol Impacts on Climate During the Past Century, to be submitted to J. Clim.
5. Koch 5. Koch
Direct Indirect BC-albedo
Series of equilibrium climate experiments in GISS ModelE, with fully coupled aerosols and a slab ocean (1890 and 1995), distinguishing direct, indirect and BC-albedo effects
[Arctic]-
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Arctic seasonality: Autumn cryospheric changes have wintertime temperature impact?
Indirect
BC-albedoDirect
5. Koch 5. Koch JAN JUL DEC JUL DEC
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New schemeOld scheme
ModelE: New aerosol-cloud approach
Two-moment bulk cloud microphysics scheme (Morrison et al., 2005)
Number concentration and mixing ratio of Cloud drop, Cloud ice, Rain, Snow
First step: Added in prognostic equations for prediction of cloud droplets and ice crystals
Cloud Droplet Number Concentration
6. Menon 6. Menon
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Ice crystal number concentration
Processes: heterogeneous freezing via immersion freezing (based on Bigg, 1953), and nucleation by deposition/condensation-freezing via the formulation of
Cooper (1986) as a function of temperature
Or
DeMott et al. (personal communication) as a function of dust aerosol number
.05
.05
Evaluation in progress
Second step: Switch on interactions between hydrometeors and examine changes to clouds.
Processes represented: Melting, freezing, collection, sedimentation, autoconversion, accretion, evaporation, condensation, deposition, sublimation 6. Menon 6. Menon
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7. Fridlind, Ackerman: Cloud-scale modeling of field measurements 7. Fridlind, Ackerman: Cloud-scale modeling of field measurements Ice Particle Formation and a NEW Arctic Aerosol Indirect Effect?
• Publication: “Ice Properties of Single-Layer Stratocumulus during M-PACE. Part II: Model Results” by Fridlind, Ackerman, et al. (JGR, 2007)
• NEW AIE: Under polluted conditions, ice formation is inhibited, increasing LWP (important for LW cloud effects) via reduced desiccation
• Detailed simulations of mixed-phase Arctic stratus: known ice formation mechanisms produce two orders of magnitude fewer crystals than measured
• But ice formation mechanisms related to liquid drop evaporation (hypothesized since the 1950’s) are a viable explanation
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