Intercontinental Transport and Climatic Effect of Air Pollutants (ICAP)

Second Workshop, October 21-22, 2004, Chapel Hill, NC

Intercontinental Aerosol Transport:Quantitative Tools an Results

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July

Global Aerosol Pattern – NASA MISR Team

• Sahara is the largest global aerosol source as evidenced by several satellite products• Sahara transport path touches the SE US, mostly in July• So, the quantification of intercontinental transport to the US is promising

Regional Haze Rule: Glide Path Toward ‘Natural Condition’

Natural haze is due to natural windblown dust, biomass smoke and other natural processes

Man-made haze is due industrial activities AND man-perturbed smoke and dust emissions

(A fraction of the man-perturbed smoke and dust is assigned to natural by policy decisions)

Origin of Fine Dust Events over the US

Gobi dust in springSahara in summer

US-scale fine dust events are mainly

from

intercontinental transport

Fine Dust Events, 1992-2003ug/m3

Observational Tools Establishing Aerosol Origin (Egen, 1835)

Direct Evidence

Spatial Pattern Wind Pattern

Composition Temporal Pattern

Trajectory

Modern Methods – similar to century-old approaches but with more data

• Direct Evidence. Photographic, satellite or compelling visual evidence of origin• Aerosol Composition. Chemical fingerprinting of different source types (speciation, traces)• Temporal pattern. Chemical Physical property analysis (satellite, ASOS, PM2.5)• Spatial Pattern. Chemical• Transport Pattern. Forward, backward trajectory, residence time analysis • Chemistry with Transport. Combining chemical fingerprinting and transport (CATT) • Dynamic modeling. Simulation model (forward, inversion) quantifying origin/transport

Historical Methods

• Source attribution methods have been used for the past 2 centuries

• A list of methods was given my Egen, 1835. See paper and PPT

Satellite Observation of Sahara Dust (SeaWiFS)

• The SeaWiFS satellite provides ‘truecolor’ images of the Sahara dust as it approaches (July 21, 1998) and covers part of the continent (July 24).

• Such SeaWiFS and other satellite data allow daily dust tracking as well as climatological dust studies.

• Sahara dust has also been frequently photographed over the Caribbean by the astronauts.

Sahara and Local Dust Identification at Big Bend, TX

• The two dust peeks at Big Bend have different Al/Si ratios

• During the year, Al/Si = 0.4 • In July, Al/Si reaches 0.55, closer to the

Al/Si of the Sahara dust (0.65-0.7) • The spring peak is identified as as ‘Local

Dust’, while the July peak is dominated by Sahara dust.

• If most of the Coarse Mass (PM10-PM2.5) is dust, the CM/FM ratio is indicative of the dust size.

• In the winter, CM/FM ~ 20, which implies large characteristic dust size (>10 m). The spring ratio is ~8 which corresponds to smaller size (8-10 m?)

• In July, CM/FM dips to ~ 4• The July ratio approaches the Sahara dust ratio of

CM/FM ~3.

Attribution of Fine Particle Dust: Local and Sahara

• In Florida, virtually all the Fine Particle Dust appears to originate from Sahara throughout the year

• At other sites over the Southeast, Sahara dominates in July

• The Spring and Fall dust is evidently of local origin

Sahara and Local Dust Apportionment: Annual and July

• The maximum annual Sahara dust contribution is about 1 g.m 3

• In Florida, the local and Sahara dust contributions are about equal but at Big Bend, the Sahara contribution is < 25%.

The Sahara and Local dust was apportioned based on their respect ive Al/Si ratios.

• In July the Sahara dust contributions are 4 -8 g.m 3

• Throughout the Southeast, the Sahara dust exceeds the local source contributions by w wide margin (factor of 2 -4)

Annual July

Temporal Scales of Aerosol Events• A goal of the FASTNET project is to detect and document natural aerosol events in the context

of the overall PM pattern

• Inherently, aerosol events are spikes in the time series of monitoring but the definition and documentation of events has been highly subjective

• Temporal variation occurs at many scales from micro scale (minutes) to secular scale (decades)

• At each scale the variation is dominated different combination of the key processes: emission, transport, transformations and removal

• Natural aerosol events occur mostly at synoptic scale of 3-5 days

Dust

Seasonal + spikes

East – west events are independent

East events occur several times a year, mostly in summer

West events are lest frequent, mostly in spring

US

West

East

Example high fine dust days (See console for complete list)

Asian DustApril 16, 2001

Sahara DustJuly 5, 2001

Southwestern Dust

Oct. 16, 2001

Dust

Signal Components:Seasonal cycle,

Synoptic ‘noise’

Event spikes

US

West

Western US - Dust

Western US - Sulfate

Signal Components:Seasonal cycle,

Synoptic ‘noise’

Sulfate

Seasonal Pattern of Dust Baseline and Events

• The dust baseline concentration is has a 5x seasonal amplitude from 0.2 to 1 ug/m3• The dust events (determined by the spike filter) occur in April/May and in July• The two April/May and the July peak in avg. dust is due to the events

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

01/01/92 02/20/92 04/10/92 05/30/92 07/19/92 09/07/92 10/27/92 12/16/92

Events

Baseline

Total

Temporal Signal Decomposition and Event

Detection

• First, the median and average is obtained over a region for each hour/day (thin blue line)

• Next, the data are temporally smoothed by a 30 day moving window (spatial median - red line; spatial mean – heavy blue line). These determine the seasonal pattern.

EUS Daily Average 50%-ile, 30 day 50%-ile smoothing

Deviation from %-ile

Event : Deviation > x*percentile

Average

Median

• Finally, the hourly/daily deviation from the the smooth median is used to determine the noise (blue) and event (red) components

TOMS and VIEWS, July

• TOMS – Dust plume from Sahara

Sahara Dust Impact EventsAIRS PM10 Concentration

Seasonal Average Fine Soil (VIEWS database, 1992-2002)

• Fine soil concentration is highest in the summer over Mississippi Valley, lowest in the winter• In the spring, high concentrations also exists in the arid Southwest (Arizona and Texas)• Evidently, the summer Mississippi Valley peak is Sahara dust while the Spring peak is from local (and

Asian) sources

Combined Aerosol-Trajectory Tool (CATT)

• High dust concentration (>7 ug/m3) in July all originate from Sahara

• Lower concentration form local sources

Eastern US PM25 Event Composition

• The largest EUS PM25 events (as RCFM) are simultaneously ‘events’ in sulfate, organics and soil!

• Some EUS PM25 events are single species events

• Some PM25 events are not events in any species; their reinforcing combination causes the PM25 event

Summary of Quantification Techniques

• Direct evidence – satellite images • Chemical tracers of Sahara, Gobi & Local dust (Al, Si, Fe, K)• Temporal analysis – spikes are IC transport events• Spatial analysis – excess dust in the dust transport path• Spatio-temporal-chemical analysis with backtrajectories

• The chemical, temporal and spatial analyses indicate a consistent estimate of 0.3 ug/m3 (2 ug/m3 in July) of fine dust over the SE US.

• These tools are primarily for science (why, how) and not necessarily good for policy (what if.. )

• We are in the midst of an aerosol sensing revolution and it would be a bummer …

Analyst Consoles:

Near-Real-Time Data

Example: NE Sulfate Episode: 8/27/04 17:00UTC

Sulfate in the Northeast

Sahara Dust in the Gulf

Fires in the Southeast

Time Series Console: Southeast

Aerosol Event Catalog: Distributed Web pages

• Aerosol events appear any time and place and analyzed by many organizations.

• The event info. is encoded, cataloged and accessed through Event Catalog

• Each ‘event’ is given attributes: location and time of occurrence and aerosol type (dust, smoke, haze, other)

• This allows graphic browsing of event-related information on maps and calendars and linking the info source, e.g. TNRCC.

• Ideas on the Event Catalog (content, structure, interface, maintenance, etc) are welcome.

Browser

Links to Distributed Analyst/Data Web page

Start with Kitty: http://webapps.datafed.net/dvoy_services/datafed.aspx?view=Kitty

Kitty

DataFed.net Large Collection of Projects, Data, Tools. Where’s CATT “Start”?

Aerosol Event Catalog: Web pages

• Catalog of generic ‘web objects’ – pages, images, animations that relate to aerosol events

• Each ‘web object’ is cataloged by location, time and aerosol type.