# Presentation: 318473

## Atmospheric Mercury Modeling at the NOAA Air Resources Laboratory using the HYSPLIT-Hg Model

**Presentation at the **
**Gulf Coast Mercury Research Collaboration Meeting **
**Gulf Power Building, Pensacola FL, May 18-19, 2006**

**Dr. Mark Cohen**
**NOAA Air Resources Laboratory**
**1315 East West Highway, **
**R/ARL, Room 3316**
**Silver Spring, Maryland, 20910**
***mark.cohen@noaa.gov***
***http://www.arl.noaa.gov/ss/transport/cohen.html***

## Outline of Presentation

**modeling methodology**
**some preliminary results for Mobile Bay **
***	******	******(based on this methodology)***
**model intercomparisons**
**summary of previous work; current goals; challenges**

## Outline of Presentation

**Outline of Presentation**
**modeling methodology**
**some preliminary results for Mobile Bay **
***	******	******(based on this methodology)***
**model intercomparisons**
**summary of previous work; current goals; challenges**

## Modeling Methodology

- _Modeling Methodology_

## NOAA 

**NOAA **
**HYSPLIT**
**MODEL**

## Slide 6

**Notes:**
This is way we typically run the HYSPLIT model.  We do a run for one particular source location, and we release puffs periodically throughout the year (e.g., once every 7 hours).  We follow each puff and keep track of the dispersion and the fate processes (deposition, transformation, etc.).  The model uses the physical-chemical properties of the pollutant we are modeling, of course. By the end of the year, we have a good idea of the average impact that a source in this location would have on the receptors of interest (e.g., the Great Lakes).

## Modeling Methodology

**NOAA HYSPLIT model ******** HYSPLIT-Hg**
**Modeling domain: North America**
**	****	*****(northern half of Mexico; continental U.S.; southern half of Canada)***
**1996 meterolog****y (180 km horizontal resolution)**

## Slide 8

## Modeling Methodology

**Modeling domain: North America**
**	****	*****(northern half of Mexico; continental U.S.; southern half of Canada)***
**1996 meterolog****y (180 km horizontal resolution)**
***only***** ****U.S. and Canadian **_**anthropogenic**_** sources****; **
**	****	*****(natural emissions, re-emissions, & global sources not included)***
**Model evaluation:**** ****1996 emissions**** and 1996 monitoring data**
**	****	*****(also evaluated in EMEP Hg model intercomparison project)***

- _Modeling Methodology_

## Figure 7. Model evaluation sites for wet deposition fluxes within 250 km of any Great Lake with available data for 1996.(Cohen et al., 2004, Environmental Research 95: 247-265)

- Figure 7. Model evaluation sites for wet deposition fluxes within 250 km of any Great Lake with available data for 1996.(Cohen et al., 2004, Environmental Research 95: 247-265)

**(Cohen et al., 2004, Environmental Research 95: 247-265)**

## Figure 8. Comparison of annual model-estimated wet deposition fluxes with measured values at sites within 250 km of the Great Lakes during 1996. The range of modeled estimates shown for each site represents the difference in estimated deposition in using the NGM-forecast model precipitation and the actual precipitation at the site. (Cohen et al., 2004, Environmental Research 95: 247-265)

- Figure 8. Comparison of annual model-estimated wet deposition fluxes with measured values at sites within 250 km of the Great Lakes during 1996. The range of modeled estimates shown for each site represents the difference in estimated deposition in using the NGM-forecast *model* precipitation and the *actual* precipitation at the site. (Cohen et al., 2004, Environmental Research 95: 247-265)

## Modeled vs. Measured Wet Deposition at Mercury Deposition Network Site DE_02 during 1996

**Modeled vs. Measured Wet Deposition at Mercury Deposition Network Site DE_02 during 1996**

## Modeling Methodology

**Modeling domain: North America**
**	****	*****(northern half of Mexico; continental U.S.; southern half of Canada)***
**1996 meterolog****y (180 km horizontal resolution)**
***only***** ****U.S. and Canadian **_**anthropogenic**_** sources****; **
**	****	*****(natural emissions, re-emissions, & global sources not included)***
**Model evaluation:**** ****1996 emissions**** and 1996 monitoring data**
**	****	*****(also evaluated in EMEP Hg model intercomparison project)***
**1****st**** set of results – Cohen et al. 2004**

- _Modeling Methodology_

## Cohen, M., Artz, R., Draxler, R., Miller, P., Poissant, L., Niemi, D., Ratte, D., Deslauriers, M., Duval, R., Laurin, R., Slotnick, J., Nettesheim, T., McDonald, J.   “Modeling the Atmospheric Transport and Deposition of Mercury to the Great Lakes.” Environmental Research 95(3), 247-265, 2004.

**Cohen, M., Artz, R., Draxler, R., Miller, P., Poissant, L., Niemi, D., Ratte, D., Deslauriers, M., Duval, R., Laurin, R., Slotnick, J., Nettesheim, T., McDonald, J.****   “Modeling the Atmospheric Transport and Deposition of Mercury to the Great Lakes.” *****Environmental Research***** 95(3), 247-265, 2004.**
**Note: Volume 95(3) is a Special Issue: "An Ecosystem Approach to Health Effects of Mercury in the St. Lawrence Great Lakes", edited by David O. Carpenter.**

## Modeling Methodology

**Modeling domain: North America**
**	****	*****(northern half of Mexico; continental U.S.; southern half of Canada)***
**1996 meterolog****y (180 km horizontal resolution)**
***only***** ****U.S. and Canadian **_**anthropogenic**_** sources****; **
**	****	*****(natural emissions, re-emissions, & global sources not included)***
**Model evaluation:**** ****1996 emissions**** and 1996 monitoring data**
**	****	*****(also evaluated in EMEP Hg model intercomparison project)***
**1****st**** set of results – Cohen et al. 2004**
**2****nd**** set of results (examples shown today) – **
***1996 meteorology***
***1999 U.S. EPA National Emissions Inventory***
***2000 emissions data from Environment Canada***

- _Modeling Methodology_

## Geographic Distribution of Largest Anthropogenic Mercury Emissions Sources in the U.S. (1999) and Canada (2000)

**Geographic Distribution of Largest Anthropogenic Mercury ****Emissions Sources in the U.S. (1999) and Canada (2000)**

## Outline of Presentation

**Outline of Presentation**
**modeling methodology**
**some preliminary results for Mobile Bay **
***	******	******(based on this methodology)***
**model intercomparisons**
**summary of previous work; current goals; challenges**

## some earlier results

**some earlier results**
**for Mobile Bay**

## Total modeled mercury deposition at selected receptors arising from from 1999 direct anthropogenic emissions sources in the United States and Canada (IPM coal fired plants are large coal-fired plants in the U.S. only) 

**Total modeled mercury deposition at selected receptors arising from from 1999 direct anthropogenic emissions sources in the United States and Canada ****(IPM coal fired plants are large coal-fired plants in the U.S. only) **

## Largest Modeled Individual Sources Contributing Mercury Deposition Directly to Mobile Bay (national view)

**Largest Modeled Individual Sources Contributing Mercury Deposition ****Directly to Mobile Bay (national view)**

***1996 meteorology (NGM)***
***1999 U.S. emissions (EPA NEI)***
***2000 Canadian emissions (Envr. Canada)***
***no sources other than U.S. & Can. anthropogenic emissions ***
***total modeled deposition to Mobile Bay ~ 3.5 g Hg/km******2******-year***

## 1996 meteorology (NGM)

***1996 meteorology (NGM)***
***1999 U.S. emissions (EPA NEI)***
***2000 Canadian emissions (Envr. Canada)***
***no sources other than U.S. & Can. anthropogenic emissions ***
***total modeled deposition to Mobile Bay ~ 3.5 g Hg/km******2******-year***

## Slide 22

## Slide 23

## Slide 24

## Largest Modeled Individual Sources Contributing Mercury Deposition Directly to Mobile Bay (large regional view)

**Largest Modeled Individual Sources Contributing Mercury Deposition ****Directly to Mobile Bay (large regional view)**

***1996 meteorology (NGM)***
***1999 U.S. emissions (EPA NEI)***
***2000 Canadian emissions (Envr. Canada)***
***no sources other than U.S. & Can. anthropogenic emissions ***
***total modeled deposition to Mobile Bay ~ 3.5 g Hg/km******2******-year***

## Largest Modeled Individual Sources Contributing Mercury Deposition Directly to Mobile Bay (regional view)

**Largest Modeled Individual Sources Contributing Mercury Deposition ****Directly to Mobile Bay (regional view)**

***1996 meteorology (NGM)***
***1999 U.S. emissions (EPA NEI)***
***2000 Canadian emissions (Envr. Canada)***
***no sources other than U.S. & Can. anthropogenic emissions ***
***total modeled deposition to Mobile Bay ~ 3.5 g Hg/km******2******-year***

## Largest Modeled Individual Sources Contributing Mercury Deposition Directly to Mobile Bay (local view)

**Largest Modeled Individual Sources Contributing Mercury Deposition ****Directly to Mobile Bay (local view)**

***1996 meteorology (NGM)***
***1999 U.S. emissions (EPA NEI)***
***2000 Canadian emissions (Envr. Canada)***
***no sources other than U.S. & Can. anthropogenic emissions ***
***total modeled deposition to Mobile Bay ~ 3.5 g Hg/km******2******-year***

## Top 25 Modeled Contributors to 1999 Hg Deposition Directly to Mobile Bay, considering anthropogenic direct emission sources in the United States and Canada

- Cumulative Fraction of Modeled Deposition

## Outline of Presentation

**Outline of Presentation**
**modeling methodology**
**some preliminary results for Mobile Bay **
***	******	******(based on this methodology)***
**model intercomparisons**
**summary of previous work; current goals; challenges**

## Model Intercomparisons

** ****EMEP MSC-East (~7 models)**
** ****HYSPLIT-Hg vs. ISC**
** ****HYSPLIT-Hg vs. CMAQ-Hg**

## Model Intercomparisons

**Model Intercomparisons**
** ****EMEP MSC-East (~7 models)**
** ****HYSPLIT-Hg vs. ISC**
** ****HYSPLIT-Hg vs. CMAQ-Hg**

## Participants

| EMEP Intercomparison Study of Numerical Models for Long-Range Atmospheric Transport of Mercury |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Intro-duction | Stage I | Stage II |  |  | Stage III |  |  | Conclu-sions |
|  | Chemistry | Hg0 | Hg(p) | RGM | Wet Dep | Dry Dep | Budgets |  |

**Participants**

- D. Syrakov ...................................**	****Bulgaria**....	**NIMH**
- A. Dastoor, D. Davignon ..................**	****Canada**......	**MSC-Can**
- J. Christensen** **...............................** ****	****Denmark**...**NERI**
- G. Petersen, R. Ebinghaus** **..................**	****Germany**...**GKSS**
- J. Pacyna ..................................... **	****Norway**.....	**NILU**
- J. Munthe, I. Wängberg .................... 	**Sweden**.....**	****IVL**
- R. Bullock ....................................**USA**.........**EPA**
- M. Cohen, R. Artz, R. Draxler ............**	****USA**.........**NOAA**
- C. Seigneur, K. Lohman ....................**	****USA**.........**	****AER/EPRI**
- A. Ryaboshapko, I. Ilyin, O.Travnikov...**	****EMEP**......	**MSC-E**

## Intercomparison Conducted in 3 Stages

| EMEP Intercomparison Study of Numerical Models for Long-Range Atmospheric Transport of Mercury |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Intro-duction | Stage I | Stage II |  |  | Stage III |  |  | Conclu-sions |
|  | Chemistry | Hg0 | Hg(p) | RGM | Wet Dep | Dry Dep | Budgets |  |

**Intercomparison Conducted in 3 Stages**

**Comparison of chemical schemes for a cloud environment**
**Air Concentrations in Short Term Episodes**
**Long-Term Deposition and Source-Receptor Budgets**

## Participating Models

| EMEP Intercomparison Study of Numerical Models for Long-Range Atmospheric Transport of Mercury |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Intro-duction | Stage I | Stage II |  |  | Stage III |  |  | Conclu-sions |
|  | Chemistry | Hg0 | Hg(p) | RGM | Wet Dep | Dry Dep | Budgets |  |

| Model Acronym | Model Name and Institution | Stage |  |  |
| --- | --- | --- | --- | --- |
|  |  | I | II | III |
| CAM | Chemistry of Atmos. Mercury model, Environmental Institute, Sweden |  |  |  |
| MCM | Mercury Chemistry Model, Atmos. & Environmental Research, USA                                                  |  |  |  |
| CMAQ | Community Multi-Scale Air Quality model, US EPA |  |  |  |
| ADOM | Acid Deposition and Oxidants Model, GKSS Research Center, Germany                                                                  |  |  |  |
| MSCE-HM | MSC-E heavy metal regional model, EMEP MSC-E |  |  |  |
| GRAHM | Global/Regional Atmospheric Heavy Metal model, Environment Canada |  |  |  |
| EMAP | Eulerian Model for Air Pollution, Bulgarian Meteo-service |  |  |  |
| DEHM | Danish Eulerian Hemispheric Model, National Environmental Institute                                                                      |  |  |  |
| HYSPLIT | Hybrid Single Particle Lagrangian Integrated Trajectory model, US NOAA |  |  |  |
| MSCE-HM-Hem | MSC-E heavy metal hemispheric model, EMEP MSC-E |  |  |  |

**Participating Models**

## Anthropogenic Mercury Emissions Inventoryand Monitoring Sites for Phase II(note: only showing largest emitting grid cells)

| EMEP Intercomparison Study of Numerical Models for Long-Range Atmospheric Transport of Mercury |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Intro-duction | Stage I | Stage II |  |  | Stage III |  |  | Conclu-sions |
|  | Chemistry | Hg0 | Hg(p) | RGM | Wet Dep | Dry Dep | Budgets |  |

**Anthropogenic Mercury Emissions Inventory****and Monitoring Sites for Phase II****(note: only showing largest emitting grid cells)**

## Slide 36

| EMEP Intercomparison Study of Numerical Models for Long-Range Atmospheric Transport of Mercury |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Intro-duction | Stage I | Stage II |  |  | Stage III |  |  | Conclu-sions |
|  | Chemistry | Hg0 | Hg(p) | RGM | Wet Dep | Dry Dep | Budgets |  |

## Total Gaseous Mercury at Neuglobsow: June 26 – July 6, 1995

| EMEP Intercomparison Study of Numerical Models for Long-Range Atmospheric Transport of Mercury |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Intro-duction | Stage I | Stage II |  |  | Stage III |  |  | Conclu-sions |
|  | Chemistry | Hg0 | Hg(p) | RGM | Wet Dep | Dry Dep | Budgets |  |

**Total Gaseous Mercury at Neuglobsow: June 26 – July 6, 1995**

## Total Gaseous Mercury (ng/m3) at Neuglobsow: June 26 – July 6, 1995

| EMEP Intercomparison Study of Numerical Models for Long-Range Atmospheric Transport of Mercury |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Intro-duction | Stage I | Stage II |  |  | Stage III |  |  | Conclu-sions |
|  | Chemistry | Hg0 | Hg(p) | RGM | Wet Dep | Dry Dep | Budgets |  |

**Total Gaseous Mercury (ng/m****3****) at Neuglobsow: June 26 – July 6, 1995**

## Total Particulate Mercury (pg/m3) at Neuglobsow, Nov 1-14, 1999

| EMEP Intercomparison Study of Numerical Models for Long-Range Atmospheric Transport of Mercury |  |  |  |  |  |  |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- |
| Intro-duction | Stage I | Stage II |  |  | Stage III |  |  | Conclu-sions |
|  | Chemistry | Hg0 | Hg(p) | RGM | Wet Dep | Dry Dep | Budgets |  |

**Total *****Particulate***** Mercury (pg/m****3****) at Neuglobsow, Nov 1-14, 1999**

## Model Intercomparisons

**Model Intercomparisons**
** ****EMEP MSC-East (~7 models)**
** ****HYSPLIT-Hg vs. ISC**
** ****HYSPLIT-Hg vs. CMAQ-Hg**

## Slide 41

## HYSPLIT 1996

_**HYSPLIT 1996**_

_**ISC: 1990-1994**_

***Different Time Periods and Locations, but Similar Results***

## Model Intercomparisons

**Model Intercomparisons**
** ****EMEP MSC-East (~7 models)**
** ****HYSPLIT-Hg vs. ISC**
** ****HYSPLIT-Hg vs. CMAQ-Hg**

## Modeled Mercury Deposition in the Great Lakes Region from all sources during 2001

**Modeled Mercury Deposition in the Great Lakes Region from all sources during 2001**

**Modeled Mercury Deposition in the Great Lakes Region attributable to U.S. coal-fired power plants during 2001**

_***CMAQ-Hg results from EPA analysis performed for the Clean Air Mercury Rule***_

## Model-estimated U.S. utility atmospheric mercury deposition contribution to the Great Lakes: HYSPLIT-Hg (1996 meteorology, 1999 emissions) vs. CMAQ-HG (2001 meteorology, 2001 emissions). 

**Model-estimated U.S. utility atmospheric mercury deposition contribution to the Great Lakes: HYSPLIT-Hg (1996 meteorology, 1999 emissions) vs. CMAQ-HG (2001 meteorology, 2001 emissions). **

## Model-estimated U.S. utility atmospheric mercury deposition contribution to the Great Lakes: HYSPLIT-Hg (1996 meteorology, 1999 emissions) vs. CMAQ-Hg (2001 meteorology, 2001 emissions). 

- Model-estimated U.S. utility atmospheric mercury deposition contribution to the Great Lakes: HYSPLIT-Hg (1996 meteorology, 1999 emissions) vs. CMAQ-Hg (2001 meteorology, 2001 emissions).
- This figure also shows an added component of the CMAQ-Hg estimates -- corresponding to 30% of the CMAQ-Hg results – in an attempt to adjust the CMAQ-Hg results to account for the deposition underprediction found in the CMAQ-Hg model evaluation.

**Notes:**
an older version of graph... small error here – the graph shows 25% (in label and in data) but should be 30%.

## Outline of Presentation

**Outline of Presentation**
**modeling methodology**
**some preliminary results for Mobile Bay **
***	******	******(based on this methodology)***
**model intercomparisons**
**summary of previous work; current goals; challenges**

## Slide 48

| Emissions Inventories |  |
| --- | --- |
| Previous Work |  1996, 1999 U.S. NEI
 1995, 2000 Canada |

## Slide 49

| Emissions Inventories |  |
| --- | --- |
| Previous Work |  1996, 1999 U.S. NEI
 1995, 2000 Canada |

| Current Objectives |  2002 U.S. NEI
 2002 Canada
 Global – 2000 (Pacyna-NILU)
 Natural sources
 Re-emitted anthropogenic |
| --- | --- |

## Slide 50

| Emissions Inventories |  |
| --- | --- |
| Previous Work |  1996, 1999 U.S. NEI
 1995, 2000 Canada |

| Current Objectives |  2002 U.S. NEI
 2002 Canada
 Global – 2000 (Pacyna-NILU)
 Natural sources
 Re-emitted anthropogenic |
| --- | --- |

| Challenges and Notes | Speciation?
Short-term variations (e.g. hourly) [CEM’s?]
Longer-term variations (e.g., maintenance)?
Mobile sources
Harmonization of source-categories 
Emissions inventories currently only become available many years after the fact; how can we evaluate models using current monitoring data?  |
| --- | --- |

## Slide 51

| Meteorological Data |  |
| --- | --- |
| Previous Work | For U.S./Canadian modeling, 1996 data from NOAA Nested Grid Model (NGM), 180 km |

## Slide 52

| Meteorological Data |  |
| --- | --- |
| Previous Work | For U.S./Canadian modeling, 1996 data from NOAA Nested Grid Model (NGM), 180 km |

| Current Objectives |  U.S.     –  NOAA EDAS 40 km,  3 hr
 Global –  NOAA GDAS 1o x 1o,  3 hr |
| --- | --- |

## Slide 53

| Challenges and Notes | Forecast vs. Analysis
Data assimilation
Precipitation??
Difficult to archive NOAA analysis datasets
Need finer-resolution datasets, especially for near-field analysis and model evaluation
We have conversion filters (e.g., for MM5), but these data are not readily available
What is the best way to archive and share data? |
| --- | --- |

| Meteorological Data |  |
| --- | --- |
| Previous Work | For U.S./Canadian modeling, 1996 data from NOAA Nested Grid Model (NGM), 180 km |

| Current Objectives |  U.S.     –  NOAA EDAS 40 km,  3 hr
 Global –  NOAA GDAS 1o x 1o,  3 hr |
| --- | --- |

## Slide 54

| Atmospheric Chemistry and Physics |  |
| --- | --- |
| Previous Work | Typical chemical mechanism
Prescribed fields for reactive trace gases (e.g., O3, OH, SO2) and other necessary constituents (e.g., soot) based on modeled, measured, and/or empirical relationships |

## Atmospheric Chemical Reaction Scheme for Mercury

| Reaction | Rate |  | Units | Reference |
| --- | --- | --- | --- | --- |
|     GAS PHASE REACTIONS |  |  |  |  |
| Hg0  + O3   Hg(p) | 3.0E-20 | cm3/molec-sec |  | Hall (1995) |
| Hg0  + HCl  HgCl2  | 1.0E-19 | cm3/molec-sec |  | Hall and Bloom (1993) |
| Hg0  + H2O2  Hg(p)  | 8.5E-19 | cm3/molec-sec |  | Tokos et al. (1998) (upper limit based on experiments) |
| Hg0  + Cl2  HgCl2 | 4.0E-18 | cm3/molec-sec |  | Calhoun and Prestbo (2001) |
| Hg0 +OH•  Hg(p) | 8.7E-14 | cm3/molec-sec |  | Sommar et al. (2001) |
|     AQUEOUS PHASE REACTIONS |  |  |  |  |
| Hg0 + O3  Hg+2 | 4.7E+7 | (molar-sec)-1 |  | Munthe (1992) |
| Hg0  + OH•  Hg+2 | 2.0E+9 | (molar-sec)-1 |  | Lin and Pehkonen(1997) |
| HgSO3  Hg0 | T*e((31.971*T)-12595.0)/T)    sec-1
[T = temperature (K)] |  |  | Van Loon et al. (2002) |
| Hg(II)  + HO2•  Hg0 | ~ 0 | (molar-sec)-1 |  | Gardfeldt & Jonnson (2003) |
| Hg0  + HOCl  Hg+2 | 2.1E+6 | (molar-sec)-1 |  | Lin and Pehkonen(1998) |
| Hg0  + OCl-1  Hg+2 | 2.0E+6 |  (molar-sec)-1 |  | Lin and Pehkonen(1998) |
| Hg(II)     Hg(II) (soot) | 9.0E+2 | liters/gram;
t = 1/hour |  | eqlbrm: Seigneur et al. (1998)
rate: Bullock & Brehme (2002). |
| Hg+2  + h<  Hg0 | 6.0E-7 | (sec)-1 (maximum)	 |  | Xiao et al. (1994); 
Bullock and Brehme (2002) |

## Atmospheric Mercury Fate Processes

**Atmospheric Mercury Fate Processes**

## Slide 57

| Atmospheric Chemistry and Physics |  |
| --- | --- |
| Previous Work | Typical chemical mechanism
Prescribed fields for reactive trace gases (e.g., O3, OH, SO2) and other necessary constituents (e.g., soot) based on modeled, measured, and/or empirical relationships |

| Current Objectives | Include new information on chemistry, e.g., bromine reactions, etc.
Sensitivity analyses
Use gridded chemical output from full-chemistry atmospheric model (e.g., CMAQ) 
Option - run HYSPLIT in Eulerian mode for chemistry; conduct one-atmosphere simulation |
| --- | --- |

## Slide 58

| Atmospheric Chemistry and Physics |  |
| --- | --- |
| Previous Work | Typical chemical mechanism
Prescribed fields for reactive trace gases (e.g., O3, OH, SO2) and other necessary constituents (e.g., soot) based on modeled, measured, and/or empirical relationships |

| Current Objectives | Include new information on chemistry, e.g., bromine reactions, etc.
Sensitivity analyses
Use gridded chemical output from full-chemistry atmospheric model (e.g., CMAQ) 
Option - run HYSPLIT in Eulerian mode for chemistry; conduct one-atmosphere simulation |
| --- | --- |

| Challenges and Notes | What is RGM?
What is Hg(p)?
What is solubility of Hg(p)?
Fate of dissolved Hg(II) when droplet dries out?
What reactions don’t we know about yet?
What are rates of reactions? |
| --- | --- |

## Slide 59

| Model Evaluation |  |
| --- | --- |
| Previous Work | US: 1996 MDN measurements
Europe: 1999 speciated ambient concentrations in short-term episodes, monthly wet deposition |

## Slide 60

| Model Evaluation |  |
| --- | --- |
| Previous Work | US: 1996 MDN measurements
Europe: 1999 speciated ambient concentrations in short-term episodes, monthly wet deposition |

| Current Objectives | Attempt to utilize all available 2002-2005 speciated ambient concentrations and wet deposition data from U.S. and other regions |
| --- | --- |

## Slide 61

| Model Evaluation |  |
| --- | --- |
| Previous Work | US: 1996 MDN measurements
Europe: 1999 speciated ambient concentrations in short-term episodes, monthly wet deposition |

| Current Objectives | Attempt to utilize all available 2002-2005 speciated ambient concentrations and wet deposition data from U.S. and other regions |
| --- | --- |

| Challenges and Notes | Comprehensive evaluation has not been possible due to large gaps in availability of monitoring and process-related data
Need data for upper atmosphere as well as surface
Need data for both source-impacted and background sites
Use of recent monitoring data with EPA 2002 inventory?
Time-resolved monitoring data vs. non-time-resolved emissions?
Hard to diagnose differences between models & measurements
Can we find better ways to share data for model evaluation (and other purposes)? To this end,  discussion is beginning on national, cooperative, ambient Hg monitoring network |
| --- | --- |

## Thanks!

**For more information on this modeling research:**
***http://www.arl.noaa.gov/ss/transport/cohen.html***