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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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slide1

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

motivation
Motivation
  • 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
what constitutes extreme region wide mercury wet deposition events across the great lakes region
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
slide4
Relative Contribution of Extreme (Top 10%) Mercury Weekly Wet Deposition Events(all years for each site)

40 percent

slide5

Relative Contribution of Extreme (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?

determination of synoptic climatology of extreme events
Determination of Synoptic Climatology of Extreme Events
  • Challenges
    • MDN data is weekly
    • Multiple synoptic weather systems events may impact region during any given week
determination of synoptic climatology of extreme events7
Determination of Synoptic Climatology of Extreme Events

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)
determination of synoptic climatology of extreme events8
Determination of Synoptic Climatology of Extreme Events
  • 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)
determination of synoptic climatology of extreme events9
Determination of Synoptic Climatology of Extreme Events
  • 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
determination of synoptic climatology of extreme events10
Determination of Synoptic Climatology of Extreme Events
  • 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
slide11

Important Ingredients

Relatively stagnant

conditions, followed

by.......

…passage of mid-

latitude cyclone

flow through mid latitude cyclone
Flow through mid-latitude cyclone

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.

slide13

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

further questions
Further Questions…
  • 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.
conclusions
Conclusions….
  • 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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