Comparing Aircraft Measurements of Atmospheric Compounds with a Regional Photochemical Model by Jennifer Schiffelbein CE 394K GISWR Fall 2003

Outline  Description of Model and Aircraft Data –TexAQS 2000 (Southeast Texas)  Completed Work –Creating grids & polygons with ArcInfo –CAMx Projection  Future Work –Spatial & Temporal issues –Interpolation

Description of Data: Aircraft  Electra aircraft –NOAA  Data collected –Position (GPS x,y,z) –Air analysis: CO, NOx, O 3, PM, VOCs….. –Meteorological  Data frequency: 1 per second  Duration: 6-7 hours (~26,000 points!)

Description of Data: Model  Predicts chemistry of atmosphere over time  Inputs: emissions, temperature, meteorology…  Time scale: 1 hour  Structure: 3-D grid

Description of Data: Model  Structure –Chosen domain: Houston/Galveston (HG) –Box = 1 km x 1 km x variable height (m) –Horizontal extent: 74 cells x 74 cells –Vertical extent: 21 layers from 0 (ground) to 4106 m

Completed Work  Generate grid (“fishnet”) Example: 2x3 grid –ArcGIS/ArcInfo Workstation/Arc Arc: workspace mydirectory Arc: generate stockings Generate: fishnet Fishnet Origin Coordinate (X,Y): 0,0 Y-Axis Coordinate (X,Y): 0,2 Cell Size (width, height): 1,1 Number of Rows, Columns: 2,3 Generate: quit *Italics = prompts *mydirectory = z:\uteid, or c:\mystuff *red text = name of file you must specify

Completed Work  Generate grid –Make map displayable Arc: clean stockings drawer Arc: build drawer poly Arc: addxy drawer Arc: quit (to close Arc window) -Directory “drawer” contains “polygon” grid shapefile -“addxy” assigns x-y coordinate to center of each grid cell -“addxy” assigns x-y coordinate to center of each grid cell *Italics = prompts *mydirectory = z:\uteid, or c:\mystuff *red text = name of file you must specify

Completed Work  Generate grid –Example: 2x3 grid result

Completed Work  Generate polygon Example: 1000x1000 box Arc: generate bigbox Generate: polygons : ID, {AUTO | X,Y}: 1, auto X,Y: -1000,0; -1000, 1000; 0,1000; 0,0 X,Y: end ID, {AUTO | X,Y}: end Generate: quit *Clean “bigbox” & build as with grid

Completed Work  Generate polygon Example results

Completed Work  CAMx Projection –Projection type: Lambert Conformal Conic –First true latitude: 30°N –Second true latitude: 60°N –Latitude of origin: 40°N –Central meridian: 100°W *Earth datum: Perfect sphere, radius = 6370km *BUT ArcGIS only offers r ~6371 km -exact projection difficult to create

Future Work  Spatial issues: *Filter aircraft data points by 1.) Is aircraft within HG domain? 2.) Which vertical layer is aircraft in?

Future Work  Spatial issues: 1.) Exclude all points outside domain

Future Work  Spatial issue: 2.) Which vertical layer is aircraft in? -Horizontal slice-Vertical slice

Future Work  Spatial issues: 2.) Which vertical layer?

Future Work  Spatial issues:  2.) Which vertical layer? –Decisiion – Assign points +½(h i+1 -h i ) & -½(h i -h i-1 ) to layer at h i

Future Work  Temporal issue: –Model hourly species concentration Example: 1:00 pm, CO conc. = 50 ppb 2:00 pm, CO conc. = 40 ppb 2:00 pm, CO conc. = 40 ppb  Aircraft second by second concentrtion Example: 1:32:08 pm, CO conc. = 46 ppb  How assign time intervals for comparison? -Aircraft points with time between *1:31 to 2:30 with 2:00 model *2:31 to 3:30 with 3:00 model

Future Work  Interpolation –Spatial Analyst – Interpolate to Raster *Try & compare 2-3 methods *Consider ~small, spatially concentrated points for each time interval and vertical layer

Concluding Remarks  Complex problem –3 dimensions and time must be considered  Large volume of data –74x74 cells = 5476 grid cells per layer –~26,000 aircraft data points

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