the influence of the chesapeake bay breeze on maryland air quality

Martin O’Malley, Governor | Anthony G. Brown, Lt. Governor | Robert M. Summers, Ph.D, Acting Secretary

MARAMA Data Analysis WorkshopLaura Landry

January 20, 2011

The Influence of theChesapeake Bay Breeze on

Maryland Air Quality

2

Outline

Introduction

Investigation of the interaction between Maryland’s air quality and the bay breeze

Methodology

Overall results

Case Study: August 18, 2009

Future workSource: AIRNow

3

Introduction

4

A Bay Breeze’s Influence

Forms due to a large temperature difference between land and bay waters

Creates a boundary, much like a small scale cold front

Ozone pollution easily accumulates along this boundary

Warm airrises

Cold airsinks

5

2009 Ozone SeasonAir Monitoring Sites D

aily peak 8-hour ozone concentration

(ppb)

Daily num

ber of sites w

ith an exceedance

Aldino

Davidsonville

Edgewood

Essex

Furley ES, Baltim

ore

Padonia

So. Carroll

Calvert Cnty

PG County

Equest. Ctr

Frederick County

HU

-Beltsville

Rockville

So. Maryland

Fair Hill

Millington

Hagerstow

n

Piney Run

4/25/2009 76 76 1

4/26/2009 78 78 1

6/8/2009 76 76 76 2

6/25/2009 79 109 86 76 109 4

6/26/2009 81 91 83 91 3

7/13/2009 77 77 1

7/15/2009 82 82 1

7/16/2009 81 77 81 2

8/16/2009 85 85 1

8/18/2009 83 83 1

8/27/2009 76 76 1

Number of exceedance days

2009: 11 2 0 9 1 0 1 0 1 0 0 1 0 0 3 0 0 0

Bay Breeze Effect

Bay Breeze EffectBay Breeze Effect

Bay Breeze Effect

Bay Breeze Effect

56% of 2009 Edgewood exceedance days also observed a bay breeze

6

Bay Breeze Climatology Days of analysis were selected based on...

75 ppb ozone NAAQS

Baltimore NAA exceedance days in June-August from 2004-2009*

High ozone days were analyzed for event types Criteria were developed using Miller and Keim (2003)

Event types: bay breeze, marginal, and non-bay breeze

Identified the “Maximum Ozone Gradient” for each day Difference between ozone at a monitoring site along the bay’s coast and

ozone at a site further inland

Used AIRNow-Tech Navigator GIS-based tool that plots current and archived pollution and meteorological

data on to customizable map

* No 2006 exceedance days were included in this study due to irregular wind data at the Edgewood site in June-August 2006.

* The Fort Meade monitor was discontinued in December 2004.

*

8

Bay Breeze Climatology Based on 83 events

24 bay breeze (29%)

15 marginal (18%)

44 non-bay breeze (53%)

Bay breeze events

Showed much higher Max. Ozone Gradients

Hour of onset: 12 PM EDT(16 UTC)

Hour of dissipation: 7 PM (23 UTC)

Baltimore NAA Ozone Exceedance Day ClimatologyDistribution by Event Type

29%

53%

18%

Bay BreezeMarginalNon-Bay Breeze

Maximum Ozone Gradient by Event Type

-25

-15

-5

5

15

25

35

45

55

65

Bay Breeze Marginal Non-Bay Breeze

Ozo

ne g

radi

ent (

ppb)

Q3MaxMedianMinQ1

Martin O’Malley, Governor | Anthony G. Brown, Lt. Governor | Robert M. Summers, Ph.D, Acting Secretary

Case Study: August 18, 2009

10

Weather Conditions

August 18th

High pressure system over Mid-Atlantic and Southeast

Clear skies

Light and variable surface winds

High temperatures in upper 80’s to lower 90’s ( F)

8 AM (EDT)

H

11

Vertical Wind Profile atBeltsville, MD

8 PM 11 PM 2 AM 5 AM 8 AM

Radar Wind Profiler

A nocturnal low level jet (NLLJ) formed

Fast moving stream of air

Shown in vertical profile measurements of wind speed and direction

Known to transport ozone into Maryland

12

Ozonesonde

Balloon carrying instruments that measure:

Ozone

Temperature

Wind speed and direction

GPS coordinates and height

Measured 100 ppb at approximately 1 km in the afternoon, 2:40 PM EDT

Source: Howard University

13

Surface Ozone Measurements

Daily maximum 8-hour ozone average

Highest at Edgewood with 83 ppb

All other sites were 31-71 ppb

Maximum ozone gradient was 60 ppb

Ozone gradient = Coastal site’s ozone – Inland site’s ozone

14

Hourly Ozone Concentrations

0

10

20

30

40

50

60

70

80

90

100

110

120

130

0 2 4 6 8 10 12 14 16 18 20 22 24

Hour (EDT)

1-hr

ozo

ne c

once

ntra

tions

(ppb

)

AldinoBeltsvilleEdgewoodEssexFair HillPadoniaPiney RunShenandoah

August 18, 2009

Edgewood peaked at 119 ppb

Short-lived, increase at Padonia at 4 PM

Decrease at Edgewood at 3 PM from the bay breeze’s shift inland

Essex began decline around the same time

Major drop in ozone by nearly all sites at

5 PM due to thunderstorms

15

Ozone and Wind Analysis10 AM (EDT)

Estimated bay breeze

Onshore flow

Source: AIRNow-Tech

Edgewood

Direction wind is coming from

16

Ozone and Wind Analysis12 PM (EDT)


High values started at Edgewood

Source: AIRNow-Tech

17



Edgewood jumped ~20 ppb from 12 – 1 PM

Source: AIRNow-Tech

18



…then ~20 ppb again by 2 PM

Source: AIRNow-Tech

Ozone gradient:

119 (Edgewood) – 59 (Aldino) = 60 ppb 90 (Essex) – 53 (Padonia) = 37 ppb

19



Edgewood began its decline while surrounding

sites started to rise

Source: AIRNow-Tech

20



Bay breeze moved inland

Source: AIRNow-Tech

21



Source: AIRNow-Tech

22



Back to Green (Good) air quality -thunderstorms moved eastward

through MD

Source: AIRNow-Tech

23

Bay Breeze in the Radar

Next you will see the bay breeze in an animation of radar imagery

Pay close attention to the white dashed lines

It will indicate where the boundary will briefly appear

24

Bay Breeze in the Radar

Bay breeze close to Edgewood

Boundary moved inland by 3 PM

25

End to the Episode

Strong thunderstorms swept through the state from the west

The following day brought cloudier skies

Afternoon thunderstorms moved in earlier than they had on August 18th

August 18th

August 19th

26

Future Work

Formulate a bay breeze climatology for Edgewood only

Seems most prone to its ozone being negatively affected by the bay breeze

Tentative methodology

Edgewood ozone exceedance days

Use the NOAA MADIS mesonet of weather observations to aid in wind analysis This dataset will aid in determining how far inland the bay breeze

can move More precise hour of onset/dissipation

27

Maryland Department of the Environment1800 Washington Boulevard | Baltimore, MD 21230

410-537-3000 | TTY Users: 1-800-735-2258www.mde.state.md.us

Contact and ReferencesContact Information:

Laura LandryMeteorologist

Air Monitoring Program / MDEPhone: 410-537-3122

Email: [email protected]

Acknowledgements:

Duc Nguyen and Michael Woodman

References:

AIRNow, cited 2009: AIRNow-Tech. [www.airnowtech.org]

Miller, S. T. and B. T. Keim, 2003: Synoptically-driven controls on the sea breeze of the central New England coast. Wea. Forecasting, 18, 236-248.

NOAA NCDC, cited 2009: NCDC NEXRAD Data Inventory Search. [www.ncdc.noaa.gov/nexradinv/]

Plymouth State University, cited 2009: Plymouth State Weather Center. [http://vortex.plymouth.edu]

mailto:[email protected]�

28

Appendix

The appendix includes the following items:

1. Event Type Criteria

2. Additional measurements from the August 18th

ozonesonde

3. Poster presented at the 2010 AMS Annual Meeting and the 2010 National Air Quality Conference

29

Event Type CriteriaCriteria were developed to identify bay breeze, marginal, and non-bay breeze events. These were an adaptation of Miller and Keim (2003) sea breeze event criteria.

BAY BREEZE:

1. An onshore wind shift must occur at 1+ coastal sites. Coastal sites: Edgewood, Essex

Average of morning to midday cloud cover must be < BKN to ensure a wind shift was not synoptically driven

2. 1+ inland sites must display parallel, antiparallel, or perpendicular wind flow to the shoreline. Inland sites: Aldino, Padonia

3. Wind speeds associated with the bay breeze must be ≥ 3 kts. 1 hour of lighter wind speed was allowable due to the bay breeze’s light wind nature.

4. Criteria #1-3 must be sustained for ≥ 3 hrs.

MARGINAL:

1. All bay breeze event criteria were met except the bay breeze duration, lasting < 3 hrs.

NON-BAY BREEZE:

1. Bay breeze and marginal event criteria were not met.

30

Ozonesonde on August 18th

Ozonesonde at Beltsville, MDLaunched: August 18, 2009, 2:40 PM (EDT)

0

0.5

1

1.5

2

2.5

3

3.5

4

70 120 170 220 270

Hei

ght (

km)

Wind Direction (deg)


0

0.5

1

1.5

2

2.5

3

3.5

4

0 2 4 6 8 10 12 14

Hei

ght (

km)

Wind Speed (m/s)


0

0.5

1

1.5

2

2.5

3

3.5

4

-5 5 15 25 35 45 55 65 75 85 95 105

Heig

ht (k

m)

0

0.5

1

1.5

2

2.5

3

3.5

4

T (degC)RH (%)

WE S

The Influence of the Chesapeake Bay Breeze on Maryland Air QualityLaura Landry, Michael Woodman, and Duc Nguyen | Maryland Department of the Environment, Baltimore, MD

OVERVIEWMaryland has greatly improved its air quality over the past several years. However, one region within the

Baltimore Nonattainment Area (BNAA) presents many challenges in meeting the 2008 8-hour average ground-level ozone National Ambient Air Quality Standard (NAAQS) of 75 ppb. The northern Chesapeake Bay regionobserves the highest ozone concentrations throughout the state, largely due to its location downwind of twomajor metropolitan areas as well as the development of the bay breeze. The formation of this micro-scalecirculation has been known to create a sharp gradient of monitored ozone concentrations across its boundary.

A climatological study of the Chesapeake Bay breeze is presented, specifically focusing on the northern bayregion of the BNAA. The results of this study describe bay breeze frequency during the months of June-August,2004-2009 with respect to days when ozone exceeded the standard. In addition, a comparison of ozoneconcentrations between inland and coastal air monitoring sites will help quantify the ozone load that can beattributed to the bay breeze.

METHODOLOGYCriteria were developed to identify bay breeze, marginal,

and non-bay breeze events. These were an adaptation ofMiller and Keim (2003) sea breeze event criteria.

BAY BREEZE:1) An onshore wind shift must occur at 1+ coastal sites.

Coastal sites: Edgewood, EssexInland sites: Aldino, Padonia

2) 1+ inland sites must display parallel, antiparallel, orperpendicular wind flow to the shoreline.

3) Wind speeds associated with the bay breeze must be≥ 3 kts. 1 hour of lighter wind speed was allowable dueto the bay breeze’s light wind nature.

4) Criteria #1-3 must be sustained for ≥ 3 hrs.

MARGINAL:All bay breeze criteria were met except the bay breeze duration lasts < 3 hrs.

NON-BAY BREEZE:Bay breeze and marginal criteria were not met.

NOTE: Fort Meade was closed in 2004

NON-BAY BREEZEOnset: - Dissipation: -• Maximum ozone gradient of 17 ppb at 2100 UTC• High pressure over the Midwest and western Mid-Atlantic

regions• Synoptic wind flow from N• Mostly sunny skies• Maximum temperatures in the low 90’s ( F)

July 31 2007

1600 UTC

July 31 2007

2100 UTC

Aug. 1, 2007

0000 UTC

Hourly Ozone Trends: July 31, 2007

0

20

40

60

80

100

120

140

500 800 1100 1400 1700 2000 2300 200

Hour (UTC)

Ozo

ne (p

pb)

AldinoDavidsonvilleEdgewoodEssexFurleyPadoniaSouth Carroll

MARGINALOnset: 1900 UTC Dissipation: 2100 UTC• Maximum ozone gradient of 21 ppb at 2000 UTC• High pressure over the southern Mid-Atlantic• Stationary front W-E across the Midwest and PA• Mostly sunny skies• Maximum temperatures in the low 90’s ( F)

Aug. 4, 2004

1900 UTC

Aug. 4, 2004

2000 UTC

Aug. 4, 2004

2100 UTC

Hourly Ozone Trends: August 4, 2004

020406080

100120140

500 800 1100 1400 1700 2000 2300 200

Hour (UTC)

Ozo

ne (

ppb)

AldinoDavidsonvilleEdgewoodEssexFort MeadePadoniaSouth Carroll

BAY BREEZEOnset: 1600 UTC Dissipation: 0100 UTC• Maximum ozone gradient of 55 ppb at 2100 UTC• Weak high pressure over Mid-Atlantic region• Synoptic wind flow from WNW• Mostly sunny skies• Maximum temperatures in the upper 80’s ( F)

June 25, 2009

1600 UTC

KDOX, 1653 UTC

June 25, 2009

2100 UTC

June 26, 2009

0100 UTC

Hourly Ozone Trends: June 25, 2009

020

406080

100

120140

500 800 1100 1400 1700 2000 2300 200Hour (UTC)

Ozo

ne (p

pb)

AldinoDavidsonvilleEdgewoodEssexFurleyPadoniaSouth Carroll

RESULTS

Of the 83 cases selected from 130 BNAA exceedance days, there were 24 bay breeze events, 15 marginalevents, and 44 non-bay breeze events. For bay breeze events, the average hour of onset was 1600 UTC, whilethe typical hour of dissipation was 2300 UTC. For marginal events, most had an hour of onset and dissipation of1800 and 2000 UTC, respectively. The maximum ozone gradient was calculated by taking the difference in ozoneconcentrations from coastal sites to inland sites. These gradients showed a large spread of values, especially formarginal events. However, they do show that the bay breeze’s median gradient of 37 ppb was the largest whilenon-bay breeze events had the lowest of 13 ppb. This means that the median gradient of bay breeze events wasnearly 3X greater than the non-bay breeze.

Maximum Ozone Gradient by Event Type

-25

-15

-5

5

15

25

35

45

55

65

Bay Breeze Marginal Non-Bay BreezeOzo

ne g

radi

ent (

ppb)

Q3

Max

Median

Min

Q1

Hour of Onset

0123456789

101112

1400 1500 1600 1700 1800 1900 2000 2100Hour (UTC)

Freq

uenc

y

Bay BreezeMarginal

Hour of Dissipation

0123456789

101112

1600 1700 1800 1900 2000 2100 2200 2300Hour (UTC)

Freq

uenc

y

Bay BreezeMarginal

Distribution by Event Type

29%

53%

18%

Non-Bay Breeze

Bay Breeze

Marginal

REFERENCES:

AIRNow, cited 2009: AIRNow-Tech. [www.airnowtech.org]

Miller, S. T. and B. T. Keim, 2003: Synoptically-driven controls on the sea breeze of the central New England coast. Wea. Forecasting, 18, 236-248.

NASA, cited 2009: The LANDSAT Program. [landsat.gsfc.nasa.gov]DDEPARTMENT OF THE EPARTMENT OF THE EENVIRONMENTNVIRONMENT

CONTACT:ARMA / Ambient Air Monitoring Program

1800 Washington Blvd., Suite 730Baltimore, MD 21230Phone: (410) 537-3616 V

ersi

on: 1

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the influence of the chesapeake bay breeze on maryland air quality

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