IUGG-biological-2007-PJDeMottvali/perugia07/talks/demott.pdf · 2007. 8. 3. · Title: Microsoft PowerPoint - IUGG-biological-2007-PJDeMott Author: Paul Created Date: 7/16/2007 1:06:11

XXIV IUGG XXIV IUGG –– Biological Ice Biological Ice NucleatorsNucleators in the Atmospherein the Atmosphere

July 10, 2007July 10, 2007PerugiaPerugia, Italy, Italy

Author: Paul DeMottAuthor: Paul DeMott

Atmospheric ice nuclei Atmospheric ice nuclei concentrations and concentrations and

characteristics constraining characteristics constraining the role of biological ice the role of biological ice

nucleinuclei

Paul J. DeMott, Mathews S. Richardson, Daniel .J. Paul J. DeMott, Mathews S. Richardson, Daniel .J. CziczoCziczo, Anthony J. , Anthony J. PrenniPrenni and Sonia M. and Sonia M. KreidenweisKreidenweis




Overview of TodayOverview of Today’’s Talks Talk

•• How we measure ice nuclei and infer sources and How we measure ice nuclei and infer sources and characteristics in the atmospherecharacteristics in the atmosphere

•• The characteristics of ice nuclei based on The characteristics of ice nuclei based on measurements over the last decade or someasurements over the last decade or so–– ConcentrationsConcentrations–– SizesSizes–– CompositionsCompositions

•• Some present limitations on assessing the likelihood Some present limitations on assessing the likelihood that biothat bio--aerosols play a role as ice nuclei (sizes aerosols play a role as ice nuclei (sizes measured, appearance, where/when sampled)measured, appearance, where/when sampled)




Measuring ice nuclei: Continuous flow Measuring ice nuclei: Continuous flow diffusion chamber (CFDC)diffusion chamber (CFDC)

OPC

0.3 1.5 μmaerosolaerosol Activated INActivated IN

or PCVI extracts to single particle mass spectrometer

5




What ice nucleation mechanisms do we measure?What ice nucleation mechanisms do we measure?

Yes

YesYes/maybe

No, but…

Aerosols nucleate ice by varied Aerosols nucleate ice by varied mechanisms, most depending mechanisms, most depending on T, some on RH as wellon T, some on RH as well

No instrument yet capable of No instrument yet capable of measuring all mechanismsmeasuring all mechanisms

What can a CFDC measure?What can a CFDC measure?

Is immersion freezing a singular Is immersion freezing a singular process on the time scale of process on the time scale of measurement?measurement?

Contact freezing nuclei should be Contact freezing nuclei should be defined by the total numbers of defined by the total numbers of immersion freezing nuclei active at immersion freezing nuclei active at somewhat lower temperature?somewhat lower temperature?




aircraft aerosol sample inletaircraft aerosol sample inlet

CVI inlet (aerosol CVI inlet (aerosol from evaporated from evaporated cloud particles)cloud particles)

Sampling in various locations in various seasons from Sampling in various locations in various seasons from the surface and from aircraftthe surface and from aircraft

Compact Compact instrument instrument certified for certified for sampling on any sampling on any aircraft platformaircraft platform

Sampling at surface sitesSampling at surface sites




What are the concentrations of ice nuclei What are the concentrations of ice nuclei in the atmosphere?in the atmosphere?




IN concentration dependence on IN concentration dependence on temperaturetemperature

0.01

0.1

1

10

100

1000

10000

-50 -40 -30 -20 -10 0

Temperature (oC)

IN c

once

ntra

tion

(per

lite

r)

INSPECT-I binned

INSPECT-II binned

Meyers et al. (1992);RHw = 100%

Fletcher

Phillips et al. (2007)'background'

0.01

0.1

1

10

100

1000

10000

-50 -40 -30 -20 -10 0

Temperature (oC)

IN c

once

ntra

tion

(per

lite

r)

INSPECT-I binned

INSPECT-II binned

M-PACE binned

FIRE-ACE binned

Meyers et al. (1992);RHw = 100%

Fletcher

Phillips et al. (2007)'background'0.01

0.1

1

10

100

1000

10000

-50 -40 -30 -20 -10 0

Temperature (oC)

IN c

once

ntra

tion

(per

lite

r)

INSPECT-I binned

INSPECT-II binned

M-PACE binned

FIRE-ACE binned

WISP94 (Winter-Spring)Meyers et al. (1992);RHw = 100%Fletcher

Phillips et al. (2007)'background'CRYSTAL-FACE: SALdustPacDEx: Asian dust




IN concentration dependence on IN concentration dependence on supersaturationsupersaturation with respect to icewith respect to ice

0.01

0.1

1

10

100

1000

10000

0 20 40 60Ice Supersaturation (%)

IN c

once

ntra

tion

(per

lite

r)

INSPECT-I (Fall)binnedINSPECT-II(Spring) binnedM-PACE binned

WISP94 (Winter-Spring)FIRE-ACE (May1998)Meyers et al.(1992)Phillips et al. (2007)'Background'CRYSTAL-FACE:SAL dustPacDEx: Asiandust




Cumulative distribution of [IN] and Cumulative distribution of [IN] and sampling conditions in many projectssampling conditions in many projects

Increasing dust Increasing dust particle impactsparticle impacts

MPACE: Arctic FallFIRE-ACE: Arctic Spring

INSPECT-2: Western U.S. SpringCRYSTAL-FACE: Florida July

winter to summerwinter to summer




Do ice nuclei relate to ice in Do ice nuclei relate to ice in clouds?clouds?




Winter Icing in Storms Project (1994) Winter Icing in Storms Project (1994) wave cloud [ice (>50 wave cloud [ice (>50 μμm)] versus [IN]m)] versus [IN]

0.01

0.1

1

10

100

-40 -30 -20 -10 0

Temperature (oC)

IN o

r Ice

Cry

stal

Con

c. (L

-1) CFDC IN Data

DCC IN Data

Cloud Ice Conc.




IN data versus ice in clouds for Arctic IN data versus ice in clouds for Arctic stratus (spring versus fall seasons)stratus (spring versus fall seasons)

2Dc > 125 μm ice versus IN

0.01

0.1

1

10

100

-40 -30 -20 -10 0

Temperature (oC)

[2D

c>12

5 μm

],[IN

] (pe

r lite

r)

MPACE ice cloudsMPACE INFIREACE ice cloudsFIREACE IN




Where do IN come from? What are their Where do IN come from? What are their physical and chemical characteristics?physical and chemical characteristics?




Ice nuclei physical size from TEM Ice nuclei physical size from TEM analyses in several programsanalyses in several programs




Relation of IN to larger aerosol using a variety Relation of IN to larger aerosol using a variety of data setsof data sets

0.01

0.1

1

10

100

0.01 0.1 1 10 100 1000 10000IN concentration (per liter)

Aer

osol

con

c. >

0.5

μm

(cm

-3)

INSPECT-2 (>1 hr)

CRYSTAL-SAL dust

AIRS-11/14/03

AIRS-11/19/03

PacDEx Asian dust

Power law fit

y = 0.2084x0.6894

r2 = 0.7526




Mineral dust and metallic particles dominate Mineral dust and metallic particles dominate IN compositions (IN compositions (CziczoCziczo et al. 2003; et al. 2003; Richardson et al. 2007)Richardson et al. 2007)

Results from PALMS (Particle Ablation Laser Mass Spectrometry) analysis of ambient aerosol particles

PALMS analyses of IN (residues of ice crystals) activated in the CFDC and aerodynamically extracted from flow.




IN composition (TEM/EDS) in several studies IN composition (TEM/EDS) in several studies (arctic, subtropics, (arctic, subtropics, midlatitudesmidlatitudes represented)represented)

C: Carbonaceous as inferred by absence of elemental signature

DM: dust and metallic (some oxides and some not)




Many laboratory studies support the role of mineral dusts as IN,Many laboratory studies support the role of mineral dusts as IN, but but our data suggests larger dusts particles needed to account for iour data suggests larger dusts particles needed to account for ice ce formation at very warmest temperaturesformation at very warmest temperatures

300 nm

400 nm

Canary Island200 nm

Water Saturation

RHw = 80%

Homogeneous freezing of sulfates




Role of carbonaceous particles as IN Role of carbonaceous particles as IN (TEM (TEM vsvs PALMS apparent discrepancy)PALMS apparent discrepancy)

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0 1 2Length (μm)

Cum

ulat

ive

frac

tion

Si,metal oxide-particles

C-particles1 = sulfates+organics

2 = carbonaceous

3 = minerals

4 = metal (oxides)

5 = “other”




What are these carbonaceous IN?What are these carbonaceous IN?irregular

structure

amorphous

sooty

Lab graphitized soot




Biomass burning smoke particles tested in Biomass burning smoke particles tested in laboratory only rarely a source of laboratory only rarely a source of measurable IN measurable IN

Utah sage/rabittbrush mix indicates apparent modest numbers of freezing nuclei (only one

of more than 40 tested)

Most smokes froze at low temperature at the conditions identified for homogenoeus

freezing of soluble haze particles




PACDEX vertical profile over Central PACDEX vertical profile over Central Pacific Ocean (May 23, 2007)Pacific Ocean (May 23, 2007)

0.001

0.01

0.1

1

10

100

50001000015000200002500030000

Pressure Alt. (ft)[IN

], [S

P2],

[CC

N-0

.1%

] (cm

-3)

0

20

40

60

80

100

120

140

160

[CO

] (pp

bv)

Filter[CO][IN]-CFDC[CIP_SP2][UHSAS>500nm]

T = -32ºC;

RH = 100-103%

Likely dust plumes, but note rise of “black carbon”(SP-2) particle concentrations in hand with larger particles.




Some present limitationsSome present limitations

•• We are designing instruments to detect ice We are designing instruments to detect ice formation by larger aerosols, but by removing formation by larger aerosols, but by removing the distinction of ice and aerosol by size, how the distinction of ice and aerosol by size, how do we extract ice crystals to measure IN do we extract ice crystals to measure IN composition?composition?




New detectors should allow elimination of New detectors should allow elimination of activated IN detection by size aloneactivated IN detection by size alone




Some present limitationsSome present limitations

•• We are designing instruments to detect ice We are designing instruments to detect ice formation by larger aerosols, but by removing formation by larger aerosols, but by removing the distinction of ice and aerosol by size, how the distinction of ice and aerosol by size, how do we extract ice crystals to measure IN do we extract ice crystals to measure IN composition?composition?

•• We have not sampled much directly in We have not sampled much directly in regions likely to have strong biological inputs regions likely to have strong biological inputs (lower altitude areas over oceans and source (lower altitude areas over oceans and source plant surfaces)plant surfaces)

•• How best to identify How best to identify ““biologicalbiological”” IN?IN?




SummarySummary•• IN concentrations in the atmosphere range from below IN concentrations in the atmosphere range from below

0.0001 cm0.0001 cm--33 to as high as a few cmto as high as a few cm--33. Nevertheless, . Nevertheless, typical values are 0.001 to 0.01 cmtypical values are 0.001 to 0.01 cm--3 and rarely exceed a 3 and rarely exceed a 0.1cm0.1cm--33..

•• Lower IN concentrations are found particularly in cold Lower IN concentrations are found particularly in cold seasons/regions and at times through elevated layers of seasons/regions and at times through elevated layers of the atmosphere. Desert dust is usually responsible for the atmosphere. Desert dust is usually responsible for highest [IN].highest [IN].

•• IN compositional measurements confirm sources from IN compositional measurements confirm sources from mineral dusts, metallic particles (some may be mineral dusts, metallic particles (some may be anthropogenic) and substantial but variable and anthropogenic) and substantial but variable and unidentified numbers of carbonaceous particles. unidentified numbers of carbonaceous particles. Biomass smokes are mostly poor sources of IN. Biomass smokes are mostly poor sources of IN.




Summary (continued)Summary (continued)

•• IN, while having mode sizes between 0.2 IN, while having mode sizes between 0.2 –– 0.5 0.5 μμm, m, extend into the extend into the supermicronsupermicron range where we have range where we have the weakest instrumental capabilities for identifying the weakest instrumental capabilities for identifying their compositions.their compositions.

•• NietherNiether the apparent physical morphology, nor the apparent physical morphology, nor typical sizes of IN support a strong biological source, typical sizes of IN support a strong biological source, but measurements have not emphasized the but measurements have not emphasized the expected size range of these and sampling has not expected size range of these and sampling has not focused very much on seasons and locations where a focused very much on seasons and locations where a strong biostrong bio--input is most expected.input is most expected.

Acknowledgments: U.S. NSF grants ATM0334228, ATM0313628, ATM07Acknowledgments: U.S. NSF grants ATM0334228, ATM0313628, ATM07????????; NCAR ; NCAR Research Aviation Facility; DOEResearch Aviation Facility; DOE--ARM; NASA NAG5ARM; NASA NAG5--11476; 11476; U.S.ForestU.S.Forest Service, National Service, National Park Service, Mike Park Service, Mike PoellotPoellot, Randy , Randy BorysBorys, Doug , Doug WestphalWestphal, Jeff , Jeff StithStith, David Rogers, , David Rogers, OttmarOttmarMoehlerMoehler..

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IUGG-biological-2007-PJDeMottvali/perugia07/talks/demott.pdf · 2007. 8. 3. · Title: Microsoft PowerPoint - IUGG-biological-2007-PJDeMott Author: Paul Created Date: 7/16/2007 1:06:11