Integrating Multimedia Measurements of Mercury in the Great Lakes Region July 13-15, 2010 Ann Arbor, Michigan

1. 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

2. 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

3. 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

4. Relative Contribution of Extreme (Top 10%) Mercury Weekly Wet Deposition Events(all years for each site) 40 percent

5. 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?

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

7. 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)

8. 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)

9. 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

10. 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

11. Important Ingredients Relatively stagnant conditions, followed by....... …passage of mid- latitude cyclone

12. 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.

13. 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

14. 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.

15. Precipitation-scale Analysis UMAQL Dexter Site

16. 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.