1. Airmass History Analysis During High and Low Sulfate Days Bret A. Schichtel NPS/CIRA Fort Collins, CO BRAVO Study Data Analysis Meeting San Antonio, TX March 23, 2001 Presentation available on IMPROVE website (cira.colostate.edu\IMPROVE) in the Study / BRAVO section

2. Big Bend Airmass Histories The history of an airmass arriving at Big Bend on 8/23/99 Airmass history database: Five day airmass historys Every two hours from7/1 – 10/31/99 Each airmass is comprised of 75 particles RH, Temp, precipitation and wind speeds were saved along with each particles 3-D position EDAS and FNL winds used to generate airmass histories

3. Distance weighted residence time analysis (similar to source contribution fnc.): Removes the central tendency (hump at the receptor) in the plot. Residence Time Analysis Where is the airmass most likely to have previously resided prior to impacting the receptor Residence Time Density Fnc Distance Weighted Residence Time The residence time is the time all airmasses reside over a grid cell. An 80 km Grid used to track the particles

4. Decomposition of Residence Time Density Fnc Residence Time Density Fnc D: Transport Direction Frequency AP: Accumulation Potential Res. Time = D * AP * (Traj. Length) D = Transport Direction Frequency The frequency airmass histories pass over a grid cell (trajectories count) AP = Accumulation Potential The inverse of the average speed the airmasses reside over a grid cell

5. Characterization of Airmass Height Average Particle Height The airmass height helps to characterize the dilution of the airmass and whether or not the airmass could accumulated emission from a source region

6. Relationship of Airmass Transport and Sulfate Concentrations Transport condition were examined during: High (90 th %-ile) and low (10 th %-ile) sulfate concentrations Individual episodes

7. Transport Patterns - High SO 4 Days (> 5  g/m 3 ) Residence Time Density Fnc. Distance Wgted Residence Time Conditional Probability Residence Time Wgted Mean SO 4

8. Transport Patterns - High SO 4 Days (> 5  g/m 3 ) Transport Directional Frequency Distance Wgted Directional Freq Accumulation Potential Average Particle Height

9. Transport Patterns - Low SO 4 Days (<0.82  g/m 3 ) Residence Time Density Fnc. Distance Wgted Residence Time Conditional Probability

10. Transport Patterns - Low SO 4 Days (<0.82  g/m 3 ) Transport Directional Frequency Distance Wgted Directional FreqAccumulation Potential Average Particle Height

11. Conclusions – High & Low SO 4 Days High sulfate concentrations are associated with: Frequent low level and low speed transport from East Texas and along the Texas-Mexican border Transport over the Industrial Midwest and eastern TN. Airmasses over the Industrial Midwest are high (>2km) and have high speeds (>10 m/s). Low sulfate concentrations are associated with: Frequent low level, high speed transport from the Gulf of Mexico. Occasional low level, low speed transport from Southern California - Hummm

12. Transport Patterns: 7/1 - 7/9 Episode Predominate transport pathway is along the Texas – Mexican border and from the southeastern US. (Border & S.E US episode) Residence Time Density Fnc. Distance Wgted RT Accumulation Potential Avg. Particle Height

13. Transport Patterns: 8/20 - 8/23 Episode Predominate transport pathway is from southeast Texas which is associated with low transport heights and speeds. (E. Texas Episode) Residence Time Density Fnc. Distance Wgted RT Accumulation Potential Avg. Particle Height

14. Transport Patterns: 8/32 – 9/3 Episode Frequent, low level transport along border and from the S.E. US. Low wind speeds along Mexican – Gulf border. Similar to 8/1-8/9 episode (Border & E. US episode) Residence Time Density Fnc. Distance Wgted RT Accumulation Potential Avg. Particle Height

15. Transport Patterns: 9/13 – 9/16 Episode Predominate transport is from eastern Texas and south of Texas border. This is low level and moderate speed transport. (E. Texas - N. Mexico episode) Residence Time Density Fnc. Distance Wgted RT Accumulation Potential Avg. Particle Height

16. Transport Patterns: 9/26 - 9/28 Episode Low level moderate speed transport from the Gulf along Northern Mexico. (Northern Mexico Episode) Residence Time Density Fnc. Distance Wgted RT Accumulation Potential Avg. Particle Height

17. Transport Patterns: 10/4 – 10/8 Episode Low level and speed transport from Eastern Texas and northern Mexico. (E. Texas – Northern Mexico episode) Residence Time Density Fnc. Distance Wgted RT Accumulation Potential Avg. Particle Height

18. Transport Patterns: 10/11 – 10/14 Episode Transport is predominantly from Eastern Texas. (E. Texas Episode) Residence Time Density Fnc. Distance Wgted RT Accumulation Potential Avg. Particle Height

19. Conclusions Big Bend sulfate episodes are associated with prior low level and low speed transport over three regions: Eastern Texas North Mexico/Texas-Mexican border from Big Bend to Gulf Southeastern US from Louisiana to eastern Tennessee. Highest episode sulfate concentrations occur when transport over these regions coincide. Lowest episode sulfate concentrations were associated with transport from the Gulf along northern Mexico / Texas-Mexican border.

20. Next Steps Airmass history Analyses: Other aerosol types and trace species Look at other meteorological parameters Climatological analysis – Place this period in a historical context Forward Transport Analyses: Trajectory mass balance analysis Emission retrieval Air Quality Pattern Analysis: Extensive monitoring network can allow for detailed spatial analysis to complement airmass histories

21. EDAS Meteorological Data Archive The EDAS (Eta Data Assimilation System) data are a product of the NWS' National Centers for Environmental Prediction (NCEP). EDAS is a data assimilation system consisting of successive 3-h Eta model forecasts and Optimum Interpolation (OI) analyses. 79 by 55 Lambert Conformal grid ~ 80 km resolution. 22 vertical layers on constant pressure surfaces from 1000 to 50 mbar 3 hour time increment Upper Air Data: 3-D winds, Temp, RH Surface Data includes: pressure, 10 meter winds, 2 meter Temp & RH, Momentum and heat flux Data is available from 1/97 to present. Note Oct. 1999 data is unavailable due to a fire at NCEP

22. FNL Meteorological Data Archive The FNL data is a product of the Global Data Assimilation System (GDAS), which uses the Global spectral Medium Range Forecast model (MRF) to assimilate multiple sources of measured data and forecast meteorology. 129 x 129 Polar Stereographic Grid with ~ 190 km resolution. 12 vertical layers on constant pressure surfaces from 1000 to 50 mbar 6 hour time increment Upper Air Data: 3-D winds, Temp, RH Surface Data includes: pressure, 10 meter winds, 2 meter Temp & RH, Momentum and heat flux Data is available from 1/97 to present.

23. Games we can play: Stratify trajectories based upon concentrations - – where is the air most likely to have resided prior to impacting the receptor when the concentrations are high, are low, are ?? Conditional probabilities – If the airmass passed through this or that area what is the likelyhood it arrived with high or low or.. concentrations. Residence time weighted concentrations. – what is the average concentrations of the airmass at the receptor when it previously resided in this or that area.

24. Concept of regional verse location transport Met wind fields suited for regional analysis will not properly capture locally, terrain influenced flow Big bend is remote and would expect synoptic scale flow to be an important factor, however eagle pass is x km away (add a transport time), montery is x km away houston is x km away – significant sources near by Acctual contributions will (could?) be a combination of locally induced and regional transport we are examining only the regional part at this time (we await the MM5 winds)