Synoptic Climatology of Extreme Mercury Wet Deposition Events in the Great Lakes Region: 2001-2008
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Synoptic Climatology of Extreme Mercury Wet Deposition Events in the Great Lakes Region: 2001-2008 Frank J. Marsik , Robert Nelson, Gerald J. Keeler, David Gay, Martin Risch and Pierrette Blanchard. Integrating Multimedia Measurements of Mercury in the Great Lakes Region July 13-15, 2010

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Synoptic Climatology of Extreme Mercury Wet Deposition Events in the Great Lakes Region: 2001-2008Frank J. Marsik, Robert Nelson, Gerald J. Keeler, David Gay, Martin Risch and Pierrette Blanchard

Integrating Multimedia Measurements of Mercury

in the Great Lakes Region

July 13-15, 2010

Ann Arbor, Michigan


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Motivation Events in the Great Lakes Region: 2001-2008

  • Determination of the relative contribution of extreme mercury wet deposition events to annual loading across the Great Lakes

  • Determination of the synoptic characteristics of extreme region-wide mercury wet deposition events across the Great Lakes region


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What constitutes “extreme region-wide mercury wet deposition events across the Great Lakes region” ?

  • Great Lakes region

    • Comprised of all state and provinces that touch one of the five major Great Lakes

  • Region-wide event

    • Weekly “event” for which precipitation was observed at 90 percent or more of measurement sites

  • Extreme

    • Largest ten percent of weekly deposition totals

      • Used for weekly region-wide average deposition

      • Used for weekly deposition at individual measurement sites


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Relative Contribution of Extreme deposition events across the Great Lakes region” ?(Top 10%) Mercury Weekly Wet Deposition Events(all years for each site)

40 percent


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Relative Contribution of Extreme deposition events across the Great Lakes region” ?(Top 10%) Mercury Weekly Wet Deposition Events(2001-2008; considered weeks where 90% of sites experienced rainfall)

Is there a climatology to the synoptic features that are contributing

to these high deposition events?


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Determination of Synoptic Climatology of Extreme Events deposition events across the Great Lakes region” ?

  • Challenges

    • MDN data is weekly

    • Multiple synoptic weather systems events may impact region during any given week


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Determination of Synoptic Climatology of Extreme Events deposition events across the Great Lakes region” ?

26 April 2009

28 April 2009

  • Challenges

    • Multiple synoptic features impact the Great Lakes during any given week

    • For a given synoptic event, different portions of the Great Lakes are impacted by different portions of the mid-latitude cyclone

      • Warm frontal precipitation (stratiform/convective)

      • Cold frontal precipitation (stratiform/convective)


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Determination of Synoptic Climatology of Extreme Events deposition events across the Great Lakes region” ?

  • Methodology

    • Utilized MDN and UMAQL data for the period from 2001-2008

    • Focused on regional events (N=137)

    • Computed basin-wide weekly average mercury wet deposition flux

      • Looked at Top 10% weekly mercury wet deposition events (N=14)

      • Looked at Bottom 10% weekly mercury wet deposition events (N=14)


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Determination of Synoptic Climatology of Extreme Events deposition events across the Great Lakes region” ?

  • Results

    • Top 10% weekly mercury wet deposition events

      • Predominantly spring/summer seasons

      • Persistent presence of stationary front across Great Lakes, often followed by mid-latitude cyclone

    • Bottom 10% weekly mercury wet deposition events

      • Predominantly fall/winter seasons

      • Transient mid-latitude cyclones


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Determination of Synoptic Climatology of Extreme Events deposition events across the Great Lakes region” ?

  • Results

    • Top 10% weekly mercury wet deposition events during spring/summer seasons

      • Persistent presence of stationary front across Great Lakes, often followed by mid-latitude cyclone

    • Bottom 10% weekly mercury wet deposition events during spring/summer seasons

      • Transient mid-latitude cyclones


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Important Ingredients deposition events across the Great Lakes region” ?

Relatively stagnant

conditions, followed

by.......

…passage of mid-

latitude cyclone


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Flow through mid-latitude cyclone deposition events across the Great Lakes region” ?

WCB = Warm Conveyor Belt

CCB = Cold Conveyor Belt

DA = Dry Air from Aloft

PCF = Post Cold Frontal Air

Cooper et al. (2004) found the highest mixing ratios of CO in the WCB and CCB.


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size/shape of symbol denotes amount of mercury emitted (kg/yr)

5 - 10

10 - 50

50 - 100

100 – 300

300 - 500

500 - 1000

1000 - 3500

color of symbol denotes type of mercury source

coal-fired power plants

other fuel combustion

waste incineration

metallurgical

manufacturing & other

Reactive Gaseous Mercury -- RGM -- Emissions to the Air

from Large Point Sources in the United States, Canada, and Mexico

Courtesy:

Mark Cohen

2002 U.S. data from USEPA National Emissions Inventory (NEI); 2002 Canadian data from Environment Canada;

1999 Mexican data from inventory prepared by Acosta y Asociados for the Commission for Environmental Cooperation


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Further Questions… (kg/yr)

  • A multi-day storm event can result in a site receiving precipitation from various forms of precipitation cells.

  • Are extreme events associated with a given precipitation cell type?

    • Stratiform precipitation

    • Convective precipitaiton

      • Single or clusters of cells

      • Linear (squall line)

      • Cloud type height

  • We can utilize UMAQL daily event database in combination with NEXRAD radar imagery to investigate potential relationships in a “case study” mode.


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Precipitation-scale Analysis (kg/yr)

UMAQL Dexter Site


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Conclusions…. (kg/yr)

  • Extreme, regional weekly mercury wet deposition events account for between 25 and 50 percent of total mercury wet deposition to a site within the Great Lakes.

  • Extreme, regional weekly mercury wet deposition events are almost exclusively warm season events.

  • These events tend to be associated with the presence of a stationary front (ie., stagnant conditions), followed by a mid-latitude weather system moving through Great Lakes.

  • Preliminary case study analysis suggests that mesoscale (<200km) convective systems (such as squall lines) may play an important role.


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