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

Airmass History Analysis During High and Low Sulfate Days

Bret A. SchichtelNPS/CIRA

Fort Collins, CO

BRAVO Study Data Analysis MeetingSan Antonio, TXMarch 23, 2001

Presentation available on IMPROVE website (cira.colostate.edu\IMPROVE) in the Study / BRAVO section

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

Distance weighted residence time analysis (similar to source contribution fnc.): Removes the central tendency (hump at the receptor) in the plot.

Residence Time AnalysisWhere is the airmass most likely to have previously resided prior to impacting the receptor

Residence Time Density Fnc

Distance Weighted Residence TimeThe residence time is the time all airmasses reside over a grid cell. An 80 km Grid used to track the particles

Decomposition of Residence Time Density FncResidence Time Density Fnc D: Transport Direction Frequency

AP: Accumulation PotentialRes. Time = D * AP * (Traj. Length)

D = Transport Direction FrequencyThe frequency airmass histories pass over a grid cell (trajectories count)

AP = Accumulation PotentialThe inverse of the average speed the airmasses reside over a grid cell

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

Relationship of Airmass Transport and Sulfate Concentrations

Transport condition were examined during:

•High (90th %-ile) and low (10th %-ile) sulfate concentrations

•Individual episodes

Transport Patterns - High SO4 Days (> 5 g/m3)

Residence Time Density Fnc. Distance Wgted Residence Time

Conditional Probability Residence Time Wgted Mean SO4

Transport Patterns - High SO4 Days (> 5 g/m3)

Transport Directional Frequency Distance Wgted Directional Freq

Accumulation Potential Average Particle Height

Transport Patterns - Low SO4 Days (<0.82 g/m3)

Residence Time Density Fnc. Distance Wgted Residence Time

Conditional Probability

Transport Patterns - Low SO4 Days (<0.82 g/m3)

Transport Directional Frequency Distance Wgted Directional Freq

Accumulation Potential Average Particle Height

Conclusions – High & Low SO4 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

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


Predominate transport pathway is from southeast Texas which is associated with low transport heights and speeds. (E. Texas Episode)



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)




Predominate transport is from eastern Texas and south of Texas border. This is low level and moderate speed transport. (E. Texas - N. Mexico episode)




Low level moderate speed transport from the Gulf along Northern Mexico. (Northern Mexico Episode)




Low level and speed transport from Eastern Texas and northern Mexico. (E. Texas – Northern Mexico episode)




Transport is predominantly from Eastern Texas. (E. Texas Episode)



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.

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

EDAS Meteorological Data ArchiveThe 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

FNL Meteorological Data ArchiveThe 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.

http://capita.wustl.edu/Asia-FarEast/reports/DustMcarloSim/fnlnhgrd.gif

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.

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)

Documents

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