Title: NARSTO PM Assessment Chapter 5: Spatial and Temporal Pattern TOC Introduction Data Global Pattern NAM Dust NAM Smoke NAM Haze NAM Total PM Local PM Dust over North America
1NARSTO PM AssessmentChapter 5 Spatial and
Temporal PatternTOC Introduction Data Global
Pattern NAM Dust NAM Smoke NAM Haze NAM Total
PM Local PM Dust over North America
- Section Contents
-
- Fine Dust Concentration
- Sahara Dust Plume in July
- Sahara Events over the Gulf Coast
- Seasonal and Secular Trends of Sahara Dust over
the US - Global Scale Dust Transport The April 1998
Asian Dust Event - Asian Dust Impact on NAM A Spatial and Temporal
Perspective - Dust Generated within in North America??
Direct questions to Rudolf B. Husar
rhusar_at_me.wustl.edu
2Sahara Dust Plume in July
- Based on TOMS Satellite. Work of Herman,
Prospero.
- In July (1998) elevated levels of absorbing
aerosol (Sahara Dust) reaches the Gulf of Mexico
and evidently, enters the continent . - High TOMS dust levels are seen along the
US-Mexican borders, reaching New Mexico. Higher
levels also cover the Caribbean Islands and S.
Florida. - Another patch of absorbing aerosol (local dust?)
is seen over the Colorado Plateau, well separated
from the Sahara dust.
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5Fine Dust Concentration
- Based on IMPROVE
- See Sisler Malm
- The year average Fine Dust is highest over the
Gulf region (gt 1 ug/m3). - In Texas and the West, Fine Dust accounts for
10-25 of the Fine Mass.
6Fine Particle Dust Concentration Over the East
Coast
- Seasonal Pattern of Dust from IMPROVE
- Strong peak in July. Dust trace extends to
Shenandoah - Dust is highly episodic 90 percentile is gtgt
median - Lots of previous work by Prospero, Cahill, Malm
7Seasonal and Secular Trends of Sahara Dust over
the US
- Daily dust levels at 6 IMPROVE sites over the SE
US were averaged to indicate regional values. - Regional Sahara Dust events occur several times
each summer (as shown by Prospero, Cahill,
Malm.) - Seasonal pattern peaks sharply in July when the
Sahara plume swings to ne North into the
Caribbean. - The July average dust declines from 7 ug/m3 in S
Florida to about 1 ug/m3 in Shenandoah.
8Sahara Events over the Eastern US
PM10 in Sahara Dust Events
- Based on PM10 data in EPAs AIRS. Previous work
by Prospero, Cahill, Malm - Scanning the AIRS PM10 database several
regional-scale PM10 episodes over the Gulf Coast
(gt 80 ug/m3) - Three such episodes are shown on the right for
July 5, 1992, June 30, 1993 and June 21, 1997. - Speciation data (IMPROVE) show that during the
events, the fine particle dust exceeds 20 ug/m3.
- The Sahara dust impact on PM10 is not confined to
fluke events. In fact, the regional PM10
concentrations over the entire Eastern US (90th
percentile) occur in July over the Gulf Coast - Hence, Sahara dust is the dominant contributor to
peak PM10 levels over the Gulf Coast (and over
the EUS NW Mexico?). - The Sisler Malm analysis also shows that Fine
Dust over the entire US is highest over the
Sahara impact region. - Issue Can this be true????RBH
9Global Scale Dust Transport The April 1998 Asian
Dust Event
Approximate location of the April 19 dust cloud
over the Pacific Ocean based on daily SeaWiFS,
GMS5/GOES9/GOES10 and TOMS satellite data. Over
the Pacific Ocean, the dust cloud followed the
path of the springtime East-Asian aerosol plume
shown by the optical thickness derived from AVHRR
data.
- a. GOES 10 geostationary satellite image of the
dust taken on the evening of April 27. - The dust cloud, marked by the brighter
reflectance covers the entire northwestern US and
adjacent portions of Canada. - A dust stream is also seen crossing the Rocky
Mountains toward the east. - b. Contour map of the PM10 concentration on April
29, 1998. Note the coincidence of high PM10 and
satellite reflectance over Washington - c. Regional average daily PM10 concentration over
the West Coast. The sharp peak on April 27-30 is
due to the Asian dust.
10The Asian Dust Event over NAM A Spatial and
Temporal Perspective
The PM2.5 dust concentration data from the
IMPROVE speciated aerosol network show virtually
no dust on April 25th, high values over the West
Coast on April 29th and dust further inland on
May 2. Evidently, on April 25th the dust layer
seen by the sun photometers was still elevated
since the surface dust concentration was low.
- The average PM2.5 dust concentration at three
IMPROVE monitoring sites over the 1988-98 period
was well below 1 mg/m3 - On April 29, 1998 the sites show simultaneous
sharp rise to 3-11 mg/m3. - Evidently, the April 1998 Asian dust event caused
2-3 times higher dust concentrations then any
other event during 1988-1998.
11Size and Composition of the Global Dust
- Both the aged Sahara and East Asian dusts have
fixed composition. - East Asian dust is enriched in Fe, CA and K
compared to the Sahara dust.
- Volume (mass) size distribution of long range
transported global-scale dust. - MMD 2-3 um.
12Dust Generated within in North America??
- Buds, can you spare some of your ideas? This
section really needs ideas! - There must be dust generated in different parts
of North America. - But
- Where
- When
- How much
- How do we document it?
13Summary of Dust Pattern over North America
- Sahara, Sahara, Sahara
- Occasional Asian Dust
- Some local NAM dust but
- Where
- When
- How much
- OK, Are YOU provoked yet?
14NARSTO PM AssessmentChapter 5 Spatial and
Temporal PatternTOC Introduction Data Global
Pattern NAM Dust NAM Smoke NAM Haze NAM Total
PM Local PM Speciated Seasonal Fine Dust
Percentiles over the Eastern US
- The seasonal aerosol aerosol pattern at the
IMPROVE sites is examined using two
methodologies - Seasonal Percentile Frequency Charts
-
15Method 2 Seasonal Percentiles, 1992-99
- The charts depict the magnitude of seasonal and
synoptic variation - The synoptic-scale variation (day-to-day) can be
measured by the 20-80 percentile spread
Great Smoky Mtn.
Lye Brook
Dirty days, 80-90
Dirty days, 80-90
Clean days (20)
Clean days (20)
- At Lye Brook, VT, the clean days (20 percentile)
corresponds to 4 ug/m3 throughout the year - The dirty days are (80-90-ile) have 2-5 times
higher concentration than the clean days.
At the Smoky Mtn, the clean days in the winter
are also 4 ug/m3. However in the summer, even
the clean days have 14 ug/m3 PM2.5. The dirty
days are have 2-3 times higher than the clean
days through out the year.
16Regional Grouping of Sites
- For this presentation the IMPROVE sites were
grouped as follows - New England ()
- Mid-Atlantic ()
- Central EUS ()
- Peripheral ()
- For each region, the seasonality is displayed
for - Chemical Mass Balance
- Carbonaceous Mass Balance
- Fine Particle Mass Percentiles
- Coarse Mass Percentiles
- Sulfate Percentiles
- Fine Soil Percentiles
- Tot. Carbon. 'Unknown' Percentiles
- Smoke Organics Percentiles
17New England Fine Soil Percentiles
Acadia
Lye Brook
18Mid-Atlantic Fine Soil Percentiles
Washington DC
Brigantine
Shenandoah
Dolly Sods
Jefferson
19Central EUS Fine Soil Percentiles
Upper Buffalo
Mammoth Cave
Shining Rock
G.Smoky Mtn.
Sipsy
20Peripheral Sites Fine Soil Percentiles
Voyageurs
Acadia
Badlands
Big Bend
Everglades
21New England Coarse Mass Percentiles
Moosehorn
Acadia
Lye Brook
22Mid-Atlantic Coarse Mass Percentiles
Washington DC
Brigantine
Shenandoah
Dolly Sods
Jefferson
23Central EUS Coarse Mass Percentiles
Upper Buffalo
Mammoth Cave
Shining Rock
G.Smoky Mtn.
Sipsy
24Peripheral Sites Coarse Mass Percentiles
Voyageurs
Acadia
Badlands
Big Bend
Everglades