Two Exceptional Events Concerning Ozone and Particle Pollution in the Southeast By:Bill Murphey Chief Meteorologist, Georgia EPD&Carlos CardelinoResearch 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; Is not reasonably controllable or preventable; Is an event caused by human activity that is unlikely to recur at a particular location or a natural event; and Is determined by U.S. EPA through the process established in the regulations, 40 CFR Part 50.14.http://www.in.gov/idem/5498.htm

Exceptional Events ExamplesCase 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 FoldSchematic 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. HEIGHT, km

O3 Measurements at Smoky Mts.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. Data provided by Jim Renfro

Chart1

2622142025

2023181848

1424221952

2224202052

4722211951

6921201756

7832231470

8261191479

8362151282

8566141362

7670141458

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4652181749

4846171654

4852181548

5250202143

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5035261837

Purchase Knob (4,900 ft)

Cove Mountain (4,150 ft)

Look Rock (2,700 ft)

Cades Cove (1,850 ft)

Joanna Bald (4,716 ft)

Date/Hour

Ozone, ppb

High February Ozone Event at Great Smoky Mountains NP Precursor/Pollutant Transport or Stratospheric Intrusion?

Ozone

Purchase Knob (4,900 ft)Joanna Bald (4,716 ft)Cove Mountain (4,150 ft)Look Rock (2,700 ft)Cades Cove (1,850 ft)

February 23, 2008182625221420

192048231818

201452242219

212252242020

224751222119

236956212017

February 24, 200807870322314

18279611914

28382621512

38562661413

47658701414

57354781515

67448771713

76844621612

85742511314

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104844471917

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124854461716

134848521815

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175037352618

Ozone

Purchase Knob (4,900 ft)

Cove Mountain (4,150 ft)

Look Rock (2,700 ft)

Cades Cove (1,850 ft)

Joanna Bald (4,716 ft)

Date/Hour

Ozone, ppb

High February Ozone Event at Great Smoky Mountains NP Precursor/Pollutant Transport or Stratospheric Intrusion?

Temp RH

Ambient TemperatureRelative Humidity

February 23, 20081830100

1929100

202899

212899

222799

232799

February 24, 200802799

13284

23753

34135

44425

54610

6468

74217

84222

94419

104230

114367

124077

134171

144469

154175

164078

173979

Temp RH

Ambient Temperature

Relative Humidity

Date/Hour

Ambient Temperature, deg F

Relative Humidty, %

Temperature and Relative Humidity at Cove Mtn

Mechanisms of Transport Across the TropopauseThe 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. 21-25The 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.

Chart2

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Dobson Units (DU)

Date

Dobson Units (DU)

Total Column Ozone Derived from TOMS Data for Nashville, TN (February 21-25, 2008)

Sheet1

DateDobson Units (DU)

2/21/08294

2/22/08300

2/23/08312

2/24/08331

2/25/08300

Sheet1

0

0

0

0

0

Dobson Units (DU)

Date

Dobson Units (DU)

Tropospheric Ozone Derived from TOMS Data for Nashville, TN (February 21-25, 2008)

Sheet2

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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, 2010High Pressure system centered over the mid-Atlantic moved eastward, keeping mostly dry stable conditions over central and south GA, along with mostly clear skiesGood pre-frontal build-up of PM2.5 ahead of the approaching cold front (stagnant conditions) may have helped concentrations at VLD go even higher

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.

EPDs WRF-ARW is initialized with NAM12 data

RUC Forecast Time-Height Section For Homerville, GALight 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

SummarySeveral 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.

AcknowledgementsAmy K. Huff, Battelle Memorial Institute

Nyasha Dunkley, Georgia Environmental Protection Division

Sean Miller, Georgia Environmental Protection Division

Jim Renfro, National Park Service

Picture on far right (controlled burn-example of not an exceptional event)Remember the tropapause is a dynamic phenomenon.Total column ozone observations near BNA saw increase in total column amount as the tropapause lowered and decreasing amount as the tropopause height rose. Dry air accompanied elevated ozone ozone near 850 mb (~5000 ft).Dry air and enhanced PV accompanied the depressed tropopause near 850mb level. According to Danielsen, ozone and PV should both be conserved at the trop level during a fold for mid-latitude systems (unless near baroclinic zones or diabatic processes).Dry air at 850mb correlated well with enhanced ozone and enhanced potential vorticity (IPV). Good subsidence and divergence aloft associated with jetstream trop fold (upstream deep low pressure system) and total column increased with lowering of tropopause and total column decreased as tropopause rose. Big divergence field centered over OK/TEX/ARK border indicative of large scale subsidence with passage of jet streak (on trailing edge).500 mb chart shows short wave location over south central plains (with lowering heights). Short wave and jet streak are ingredients for jet-stream tropopause fold. Jet-stream trop fold occurred upstream probably followed by large scale subsidence (sinking motion along 330 and 322 theta surfaces near BNA).Horizontal resolution: 1 deg x 1 deg, Vertical resolution: approx 80 km (the total atmospheric column), temporal resolution: daily1170 acres burned (swamp bay with brush and leaf litter)These measurements were from the BAMS sampler---FRM showed good agreement.Other hot spots are in the area.The surface ridge axis slowly worked eastward across GA allowing winds to shift more from the ESE.

This flow pattern advected smoke from Arabia Bay southwestward into the metropolitan Valdosta area. Model seems to have good resolution on the surface wind field.Surface observations verified smoke/haze reports. If we can determine if there is a wind shift or not during the middle of the day, then the 24-hr average will be affectedNote stream of smoke even visible on the visible satellite imagery.Stream of smoke across south GA along interacting with mid-clouds associated with approaching frontal system to the west. Enhanced AOD near VLD from downward-looking LIDAR at fire location, verifying ground observations of enhanced PM2.5. A lidar profile from the CALIPSO spacecraft, specifically the 523 nanometer Total Attenuated Backscatter. Pinks are clouds, while orange and reds are AOD from aerosols. Gives vertical view of the atmosphere by emitting short pulses of green and IR light.Other exceptional events can occur which are easier to forecast. Note strong surface inversion that put cap on smoke up to about 900 mb.Further recommendations: There may be 10 or so trop folds that occur across the SE during the year and they need to be investigated as possible exceptional events (i. e. figure out the dynamic mechanism, look at TOMS, etc...). Mesoscale analysis (WRF wind analysis and RUC40) did a nice job of handling fire/smoke transport pathway. Very difficult from a prediction point of view. Fires last long enough to account for this, so much easier to forecast because the availability of surface wind observations. Trop folds would be much more difficult to forecast because lack of upper air data ( except for rawinsonde data).