A4 A5

Heavy industrial

Major chemical, steel, and fabrication industries generally 3-5 story buildings, flat roofs Light-moderate industrial

Rail yards, truck depots, warehouse, industrial parks, minor fabrications; generally 1-3 story buildings, flat roofs Commercial

Office and apartment buildings, hotels; >10

story heights, flat roofs Common residential

Single-family dwelling with normal easements; generally one story, pitched roof structures; frequent driveways Compact residential

Single-, some multiple-, family dwellings with close spacing; generally <2 story height, pitched roof structures; garages (via alley), no driveways Compact residential

Old multifamily dwellings with close (<2m)

lateral separation; generally 2 story height, flat roof structures; garages (via alley) and ash pits, no driveways Estate residential

Expansive family dwelling on multiacre tracts Metropolitan natural

Major municipal, state, or federal parks, golf courses, cemeteries, campuses; occasional single-story structures Agricultural rural Undeveloped Uncultivated, wasteland

Undeveloped rural Water surfaces Rivers, lakes

Grass and tree growth extremely rare; <5% vegetation

Very limited grass, trees almost totally absent; <5% vegetation

Limited grass and trees; < 15% vegetation

Abundant grass lawns and light-moderately wooded; >70% vegetation

Limited lawn sizes and shade trees; <30% vegetation

Limited lawn sizes, old established shade trees; <35% vegetation

Abundant grass lawns and light wooded; >80% vegetation

Nearly total grass and light wooded; >95% vegetation

Local crops (e.g., corn, soybean); 95% vegetation

Mostly wild grasses and weeds, lightly wooded; >90% vegetation Heavy wooded; 95% vegetation

Source: A.H. Auer, 1978, Correlation of land use and cover with meteorological anomalies, Journal of Applied Meteorology 17.

FIG. 5.8.16 Schematic of the virtual point source as projected from an area source. (Reprinted from TRW Systems Group, 1969, Air quality display model, Washington, D.C.: National Air Pollution Control Administration, DHEW, U.S. Public Health Service.)

consistency, the EPA has a protocol to follow when data are substituted for missing observations.

Both short- and long-term models also require mixing height data to define the upper limit of the area where effluent mixing occurs (the ground being the lower limit). Holzworth (1972) developed a set of figures and tables for seasonal and annual mixing heights, which are typically used in long-term modeling. For short-term applications, model users can interpolate hourly mixing height values (using the EPA's RAMMET preprocessor) based on twice-a-day upper air data collected by radiosonde measurements at numerous sites throughout the country and available through the National Climatic Center (NCC).

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