“Two Exceptional Events Concerning Ozone and Particle Pollution

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					“Two Exceptional Events Concerning Ozone
  and Particle Pollution in the Southeast”


                         Bill Murphey
                  Chief Meteorologist, Georgia EPD
                      Carlos Cardelino
          Research Scientist, Georgia Institute of Technology
What is an Exceptional Event?
U.S. EPA defines the term "exceptional event" to mean an
event that:
Affects air quality;
   1.Is not reasonably controllable or preventable;
   2.Is an event caused by human activity that is unlikely to
   recur at a particular location or a natural event; and
   3.Is determined by U.S. EPA through the process
   established in the regulations, 40 CFR Part 50.14.
   Exceptional Events Examples

 Case 1 - Elevated ozone levels at three high
  altitude Smoky Mountain monitors and possible
  contribution from stratospheric ozone intrusion
  (Feb 24, 2008 - case study)

 Case 2 - Recent PM2.5 smoke episode from Arabia
  Bay Fire activity in South Georgia (November 12, 2010
  - case study)
            Case 1: Tropopause Fold

Schematic diagram illustrating the important features of a typical mid-latitude jet stream
tropopause fold (as pioneered by Danielson, 1968). Light arrows indicate cyclonic motion around
jet core (J), while dark arrows show vertical motion of tropopause (TROP).

1. Note clouds in warm air sector with ascending motion, rising tropopause, and decreasing total
column ozone amount.
2. Descending motion, a lowered tropopause, drier air, and increased total column ozone is found
behind the front and on the south side of the jet.
    O3 Measurements at Smoky Mts.

                                                             Data provided by Jim Renfro
  High ozone (70s and 80s ppb) measured at 3 high elevation Smoky Mountain sites
(near 850mb). Two other lower elevation sites stayed in the 17-23 ppb range. All sites
           were in the 20's ppb near midnight out ahead of a cold front.
Mechanisms of Transport Across the

 a) The jetstream tropopause fold (due to the
    presence of a strong jet aloft and short wave).

 b) Subsidence (due to strong Arctic anticyclone)

 c) Cutoff Lows (tropopause fold occurs during
    formation of closed Low, typically have
    interaction of jet streak with a short wave)

 (a) was the mechanism in this particular case.
Relative Humidity (850mb) – Smoky Mts.
300 MB Chart – Feb. 24
500 MB Chart – Feb. 24
HYSPLIT Back Trajectory - Feb. 24
TOMS Ozone Data for Feb. 21-25

 The TOMS instrument ( OMI/AURA) measures the differential absorption
 of backscattered UV radiation from the earth's atmosphere absorbed by
 ozone and the other weakly absorbed. The unit used for ozone measurement
 in a vertical column having a base of one cm (squared) at STP is defined the
 Dobson unit (DU). Drier air and lowered tropopause accompanied the
 increase on 2/24.
       Case 2 – Arabia Bay Fire

   The Arabia Bay fire, located six to
    ten miles northwest of Homerville
    in Clinch County (south Georgia),
    had burned nearly 3000 acres
    from Nov 9-29th, as reported the
    Georgia Forestry Commission.

   Satellite photo showing the area
    in which the Arabia Bay swamp
    fire was burning. Mainly
    composed of brush and leaf litter,
    the fire was believed to be caused
    by an arsonist. Fire caused dense
    smoke and reduced visibility in
    Homerville and Valdosta areas.
Elevated PM2.5 Hourly Values
       (Valdosta, GA)
Known Fire Data with MODIS Imagery
Satellite Surface Map – Nov 12, 2010
• High Pressure system centered over the mid-Atlantic moved eastward,
  keeping mostly dry stable conditions over central and south GA, along with
  mostly clear skies
• Good pre-frontal build-up of PM2.5 ahead of the approaching cold front
  (stagnant conditions) may have helped concentrations at VLD go even
Objective WRF Mesoanalysis
                • Local model run internally
                  at EPD.
                • Domain chosen for fire
                  region over South Georgia.
                • Wind (barbs), mean
                  Sea-level pressure
                  (contours), and Relative
                  Humidity (color fill)
                  are plotted.
                • Winds veer from northerly
                  to northeasterly from
                  11/13 into 11/14.
                • PM 2.5 concentrations
                  rapidly increase on 11/14,
                  as smoke is transported
                  from the fire region (near
                  Homerville) towards the
                  Valdosta monitoring site.

                EPD’s WRF-ARW is initialized with NAM12 data
RUC Forecast Time-Height Section
      For Homerville, GA

Light low-level northeasterly flow transported smoke into Valdosta from the fire region
Visible Imagery/RUC Analysis
Aqua Modis RGB – Southeast (11/14)
CALIPSO – Backscatter Plot
 Additional Exceptional Event
        Example (2/11/08)

Warehouse fire in South Fulton County (GA) caused hourly PM2.5
        values to increase at EPD Monitoring stations
   Several meteorological tools (Trajectories, satellite
    imagery, synoptic conditions) could be utilized
    when characterizing exceptional events.
   In case of a tropopause fold, it is important to recognize
    the type of dynamic mechanism and to investigate total
    column ozone variability. This helps validate surface and
    low-level observations. Difficult to forecast, however,
    due to short duration and lack of upper air data.
   In fire/smoke activity, other meteorological factors could
    have contributed to enhanced particle pollution levels,
    such as approaching frontal systems and pre-frontal
    pooling. Easier to predict due to long duration and
    availability of surface data.
   Some exceptional events are more frequent and clear-cut
    than others, such as the Arabia fire/smoke case.

• Amy K. Huff, Battelle Memorial Institute

• Nyasha Dunkley, Georgia Environmental
  Protection Division

• Sean Miller, Georgia Environmental Protection

• Jim Renfro, National Park Service

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