ABSTRACT
APPROACHES TO ANALYZING ATMOSPHERIC SYSTEMS 422
Conservation of Mass and Energy Approach 423 Volumetric Approach 426 Gaussian Approach 428 Summary of Assumptions 435 Numerically Integrated Approach 444
Statistical and Proportional Approaches 455 Statistical Approach 455 Proportional Approach 460
SELECTING AN APPROPRIATE AIR QUALITY MODEL 462
Population of Air Quality Models 464 Relating Problems to Models 469 Procedure for Selecting an Appropriate
Air Quality Model 473 Characteristics Used to Summarize Air
Quality Models 477 Terrain Characteristics 478 Physical Processes 478
INTRODUCTION 393
C h e m i c a l P r o c e s s e s 4 7 8
M a t h e m a t i c a l P r o p e r t i e s 4 7 8
T i m e P r o p e r t i e s 4 7 9
S p a c e P r o p e r t i e s 4 8 0
I n p u t D a t a R e q u i r e m e n t s 4 8 2
C o n c l u d i n g C o m m e n t ^ M o d e l S e l e c t i o n 4 8 4
C O N C L U D I N G C O M M E N T S 4 8 4
N O T E S 4 8 7
R E F E R E N C E S 4 9 0
A p p e n d i x A : S U M M A R Y T A B L E S O F A I R Q U A L I T Y M O D E L S 4 9 5
A p p e n d i x B : A N N O T A T E D B I B L I O G R A P H Y F O R A I R Q U A L I T Y M O D E L S 5 3 1
Chapter Five
ANALYZING ATMOSPHERIC SYSTEMS
F. Douglas Muschett
INTRODUCTION
An atmospheric system is defined herein as a specified volume of air
over a given land area. A typical atmospheric system extends vertically
from the ground to the top of the atmospheric mixing layer, about 5 to 10
thousand feet in altitude, and horizontally encompasses regions on the order
of 300 to 500 square miles. Horizontal boundaries of an atmospheric system
are defined according to the areal extent of the land area of interest,
e.g., metropolitan area defined by county boundaries, or the areal extent
of a given air quality problem, e.g., usually defined as the area within a
specified isopleth at a given point in time."^ An isopleth is a line drawn
on a map of a region connecting points of equal ambient concentration for
a specified residual, as shown in figure 5-1. In figure 5-1, the atmospheric
system in relation to the suspended particulate problem would roughly be
defined by the volume enclosed by the 30.0 micrograms per cubic meter 3 3 .(mcg/m ) isopleth. Beyond the 30.0 mcg/m isopleth, the ambient concen-
3trations of suspended particulates are generally 25.0 mcg/m and are as
sumed to be primarily the result of natural sources, residuals entering the 2region from outside of the region, or both.
