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The Great Sand Dunes Monument and Preserve is located in the San Luis Valley of south central Colorado, in the upper reaches of the Rio Grande River. Specifically, it is located in an easternmost part of the San Luis Valley that nests into the Sangre De Cristo Mountains. The Wilderness Area is wholly contained within the Monument boundaries, and comprises ~ 90% of the Monument area. The predominant physical feature is the Sand Dunes, which were formed over time by prevailing southwest winds forcing sand from the San Luis Valley up against the Sangre de Cristo Mountains. Elevations within the Wilderness Area range from ~2,380 m (~7,800 ft) to ~2,900 m (~9,500 ft), although most of the area lies below ~2,750 m (~9,000 ft). By contrast, elevations of the Sangre de Cristo Mountains rise to ~ 3,500 m (~11,500 ft) immediately east of the Wilderness Area. The generally low relief terrain of the greater San Luis Valley area to the west and southwest has elevations typically near 2,300 m (~7,500 ft). Although the elevation of the Wilderness and adjacent San Luis Valley are lower than typical elevations representative of the Southern Rocky Mountains, it is included in the Southern Rocky Mountain physiographic region, surrounded as it is by the Sangre de Cristo and San Juan ranges of the southern Rockies to the east and west, respectively. At its relatively low-lying elevation it may be more subject to direct local source effects than most high elevation Class I areas of the Southern Rocky Mountain region. The Great Sand Dunes IMPROVE site, GRSA1, is located just within the southeastern Monument boundary at an elevation of 2,504 m (8,213 ft), an elevation near the lowest end of Wilderness elevations.
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Aerosol Summary Products
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The following link opens a series of aerosol extinction summary products. Each graphic contains a stacked bar timeline chart of reconstructed aerosol extinction for
2002 with the 20% best and worst days indicated with a "B" and "W" (for monitored data only). Each graphic also contains two pie charts showing the extinction budgets
for the 20% best and worst days in 2002. The pie charts are labeled with the average and range of extinction for each category. Also included are tables summarizing the pie chart
data in absolute and percent contribution to extinction. Note that sometimes the percentages listed in the table and the corresponding percentages on the pie charts are slightly different due to rounding algorithms in the software used to generate them. (The monitored data used for these products were
taken from the VIEWS Web site, and include patched values where applicable, as determined by the procedures outlined in the
Guidance for Tracking Progress Under the Regional Haze Rule.)
Two versions of the pie charts are available, one showing aerosol extinction, the other showing total extinction, which includes Rayleigh scattering. Rayleigh
scattering is caused by the natural atmosphere and is not influenced by particulates. It is generally a large fraction of the total extinction budget in the WRAP
region and often dominates the budget on clean days. Each timeline is represented in the file twice, once generated with an auto scale feature to capture the entire range of extinction, and once generated with a scale of 150 Mm-1 to allow for easy comparison between sites. Additional timelines are available for a few sites that experienced significant filter clogging due to fire events during 2002.
Monitored data (collected every third day) and model results (generated for every day) are shown in the IMPROVE and CMAQ charts, respectively. The pie charts
represent the best and worst monitored or modeled visibility days, depending on data type. Comparisons between monitored and modeled timelines should focus on
whether the species seasonal trends and episodes are similar. (For more information regarding model performance see the AoH final report or visit the Regional
Modeling Center Web site.)
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Aerosol Summary Products
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Source Apportionment Comparisons
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The following link opens a series of source apportionment comparison products. CMAQ Tagged Species Source Apportionment (TSSA) was performed for sulfate (SO4) and
nitrate (SO3) mass. Trajectory Regression Analysis (TRA) was performed using monitored data and HYSPLIT for SO4 and extinction. Each of these products divides the
modeling domain into distinct source regions: the state the Class I area resides in; the surrounding states; the remaining WRAP states; international and other
categories. Each product presents results for either different methods or different pollutant parameters.
The first product compares TSSA and TRA SO4 results for the 20% worst visibility days. This comparison demonstrates the degree of similarity (or difference) between
apportionment methods, and can be used to qualitatively determine confidence in the results. TRA results are available only for IMPROVE monitoring sites, so
comparisons made for Class I areas without monitors show TSSA results for that CIA and TRA results for the associated IMPROVE site. State apportionment in TRA
results can be affected by the proximity of strong sources near state boundaries since trajectories may pass over those sources yet not necessarily contain
discreet trajectory points within the source state.
The second product presents TSSA SO4 and NO3 results for the 20% worst visibility days. While similarities are expected in the apportionment results for both
species, they are often not identical at a given Class I area. These products can be used to group Class I areas with similar SO4 and NO3 source regions.
The third product presents TRA extinction results for the 20% worst visibility days and for all days. This comparison is useful to show if there is a difference
between source regions contributing to extinction on dirty days than on all days. However, since extinction is determined by multiple aerosol species which may have
different source regions, these results should be considered more uncertain than apportionment results for individual species.
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Source Apportionment Comparisons
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Regional Modeling Center TSSA Data Products
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The following link points to the Regional Modeling Center's TSSA results Web page. The RMC results contain more detailed information than what is presented in the
source apportionment comparisons above.
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RMC TSSA Data
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Causes of Haze Data Products
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The following link opens a Class I area-specific site and data descriptions page on the Causes of Haze Web site. The page contains a series of links to
descriptive pages for aerosol data, meteorological conditions, emissions information, and trajectory regression analysis (TRA) results. The TRA results
contain more detailed information than what is presented in the source apportionment comparisons above.
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COHA Site Assessment
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Causes of Haze Back Trajectory Map Gallery
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The following link opens a Class I area-specific map gallery of back trajectory products on the Causes of Haze Web site. The page contains a drop down
menu that can be used to select from a variety of back trajectory map products. Of particular relevance to this report are the following maps: 3-yr
Total Residence Time; worst 20% Sulfate Residence Time; worst 20% Sulfate Residence Time Difference; and worst 20% Sulfate Conditional Probability.
Similar maps are available for other aerosol species. These maps can be used in conjunction with TSSA and TRA results to better understand geographic
source regions.
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COHA Back Trajectory Map Gallery
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Monitoring Site Information on VIEWS Web Site
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The following link opens a Class I area-specific Monitoring Site Browser on the VIEWS Web site. Available on this page are monitoring site specifications,
photos, maps, histories.
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VIEWS Monitoring Site Browser
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Emissions Inventory Information
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The following links lead to the emissions inventory data used for the AoH project and the most current emissions inventory data in the WRAP
Emissions Data Management System (EDMS) database.
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AoH Emissions Inventories
WRAP EDMS
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