OTAG Air Quality Analysis Workgroup

OTAG Air Quality Analysis WorkgroupOTAG Air Quality Analysis Workgroup

Volume I: EXECUTIVE SUMMARYVolume I: EXECUTIVE SUMMARY

Dave Guinnup Dave Guinnup andand Bob Collom, Bob Collom, Workgroup co-chairWorkgroup co-chair

Telling the OTAG Ozone Story with DataTelling the OTAG Ozone Story with Data

Draft, June 2, 1997

Workgroup ObjectiveWorkgroup Objective

The Workgroup is to provide assessments of air quality The Workgroup is to provide assessments of air quality and meteorological data relevant to the mission of OTAG.and meteorological data relevant to the mission of OTAG.

OTAG mission:

To understand the role of transported ozone and precursors in the current ozone nonattainment problem

Description of the Air Quality Analysis WGDescription of the Air Quality Analysis WG

AQA WG members were affiliated with EPA, state agencies, industry (power,transportation), consultants, academia

Members were analysts or research managers generally representing their organizations

Interaction occurred through meetings, conference calls (monthly), and e-mail

Sharing of reports, data and comments was conducted through the AQA-WG interactive web site. (http:\\capita.wustl.edu\OTAG\)

Types of AnalysesTypes of Analyses

Spatial pattern percentile analyses Trajectory residence time analyses Spatial, temporal correlation analyses Statistical cluster analyses Model/data comparisons Tracer analyses Temporal pattern and trends analyses Meta analysis: analysis of analysis Results integration

Problem StatementProblem Statement

Some nonattainment areas (e.g. NE corridor, Lake Michigan) experience considerable influx of ozone across their boundaries

They cannot demonstrate nonattainment by local measures only Significant ozone reductions at their boundaries will also be

necessary

From the OTAG Background Document:

Counties not meeting the 80 ppb standard are more Counties not meeting the 80 ppb standard are more numerous than 120 ppb nonattainments. numerous than 120 ppb nonattainments. Transport impacts at 80 ppb are more likely.Transport impacts at 80 ppb are more likely.

AreaArea source NO source NOxx emissions are highest near cities. emissions are highest near cities.

Point Point sources dominate the center of OTAG.sources dominate the center of OTAG.

Area Source Density of NOx Point Source Density of NOx

The OTAG domain corners are at tropospheric OThe OTAG domain corners are at tropospheric O33 levels. levels.

The highest avg. OThe highest avg. O33 is over the megalopolis and Ohio Valley. is over the megalopolis and Ohio Valley.

There is an increasing trend from west to east.There is an increasing trend from west to east.

Highest (90 %-ile) OHighest (90 %-ile) O33 occurs near urban areas. occurs near urban areas.

Lowest (10 %-ile) OLowest (10 %-ile) O33 is high in the center of the domain. is high in the center of the domain.

10th percentile of daily max. O390th percentile of daily max. O3

NortheastNortheast O O33 exceedances have been declining. exceedances have been declining.

OTAGOTAG domain exceedances show less decline. domain exceedances show less decline.

Ten year station-day exceedances for the Northeast.

Ten year station-day exceedances for the OTAG domain.

At At slowslow wind speeds, O wind speeds, O33 accumulates near source areas. accumulates near source areas.

At At highhigh wind speeds, O wind speeds, O33 is dispersed from sources. is dispersed from sources.

The dispersion leads to long range transport and The dispersion leads to long range transport and regional Oregional O33..

Average ozone during high (>6 m/s) wind speeds.

Average ozone during low ( < 3 m/s) wind speeds.

In the In the NortheastNortheast, regional O, regional O33 is transported mainly is transported mainly

through synoptic and channeled flows while local Othrough synoptic and channeled flows while local O33 is is

moved by near surface flows.moved by near surface flows.

On On highhigh O O33 days, the transport winds are slow with clockwise days, the transport winds are slow with clockwise

circulation around the south-center of the domain.circulation around the south-center of the domain.On On lowlow O O3 3 days, the swift transport winds are from outside the days, the swift transport winds are from outside the

domain.domain.

Transport winds during high (90%-ile) local ozone days.

Transport winds during low (10%-ile) local ozone days.

During During regional episodesregional episodes, air masses meander over the , air masses meander over the high emission regions and accumulate Ohigh emission regions and accumulate O33..

The ‘88,‘91,‘95 modeling episodes lasted 6-9 days.The ‘88,‘91,‘95 modeling episodes lasted 6-9 days.

Ozone pattern and air mass histories during the 1995 episode.

Daily maximum ozone averaged over all monitors in the domain.

OTAG-wide episodes tend to be associated with OTAG-wide episodes tend to be associated with stagnation followed by transportstagnation followed by transport..

The 4 episode avg. model concentration shows high OThe 4 episode avg. model concentration shows high O33

over the central section of the domain.over the central section of the domain. The measured OThe measured O33 pattern roughly corresponds to the model. pattern roughly corresponds to the model.

Model-average daily maximum O3

during the four episodes. Measured average daily maximum

O3 during the four episodes.

The model The model underpredictsunderpredicts O O33 in the North and in the North and overpredictsoverpredicts in in

the South by 10-20 ppb.the South by 10-20 ppb.The modeling periods The modeling periods over-representover-represent O O33 in the North and in the North and

under-representunder-represent O O33 in the South. in the South.

Difference between UAM-V model

prediction and measured O3. Difference between the OTAG domain

episodes and the 90th percentile O3.

Transport winds during the ‘91,‘93,‘95 episodes are Transport winds during the ‘91,‘93,‘95 episodes are representative of regionalrepresentative of regional episodes. episodes.OTAG episode transport winds differ from winds at OTAG episode transport winds differ from winds at high local Ohigh local O33 levels. levels.

Comparison of transport winds during the ‘91, ‘93, ‘95 episodes with winds during regional episodes in general.

Comparison of transport winds during the ‘91, ‘93, ‘95 episodes with

winds during locally high O3.

OTAG is a well defined control region. Low OOTAG is a well defined control region. Low O33 air comes air comes

from outside, high Ofrom outside, high O33 air from inside OTAG. air from inside OTAG.

Back trajectory frequencies for low ozone days.

Back trajectory frequencies for high ozone days.

The transport winds on high OThe transport winds on high O33 days are days are slow in the slow in the

center of the domaincenter of the domain..At many sites, the avg. OAt many sites, the avg. O33 is higher when the wind blows is higher when the wind blows

from the center of the domain.from the center of the domain.

Ozone roses for selected 100 mile size sub-regions.

Superposition of O3 contours and transport winds during high (90th

percentile) O3 conditions.

Emission changes do change OEmission changes do change O3 3 levels. 120 ppb exceedances levels. 120 ppb exceedances

are are 3 times higher3 times higher on Fridays than on Sundays. on Fridays than on Sundays.

Map of exceedances on Fridays. Map of exceedances on Sundays.

ConclusionsConclusions

O3 transport is real, characterized by time and space scales of 150-500 miles

Transport from central portion of OTAG domain more closely associated with high ozone levels downwind

Model may understate transport impacts -- interpret results accordingly