SouthWest Organizing Project

weather condition factors

Using the information below, find your Weather Condition Factor (A, B, C, D, E, or F), then using your browser's back arrow, return to the previous page and adjust your input matrix.

Atmospheric Stability Classifications

Category Description

A Very Unstable

B Moderately Unstable

C Slightly Unstable

D Neutral (heavy overcast, day or night)

E Slightly Stable

F Stable

Category	Description
A	Very Unstable
B	Moderately Unstable
C	Slightly Unstable
D	Neutral (heavy overcast, day or night)
E	Slightly Stable
F	Stable

Weather Condition's Matrix

Wind Speed
@ 10 m
(m/s) Strong
(Comment A) Daytime
Solar Insolation
Moderate
(Comment B) Slight
(Comment C) Night Cloudy
(1/2 or more)
(Comment D) Night Clear
(Less than 1/2)
(Comment D)

<2 A A-B B E E

2 A-B B C E F

4 B B-C C D E

6 C C-D D D D

>6 C D D D D

Wind Speed @ 10 m (m/s)	Strong (Comment A)	Daytime Solar Insolation Moderate (Comment B)	Slight (Comment C)	Night Cloudy (1/2 or more) (Comment D)	Night Clear (Less than 1/2) (Comment D)
<2	A	A-B	B	E	E
2	A-B	B	C	E	F
4	B	B-C	C	D	E
6	C	C-D	D	D	D
>6	C	D	D	D	D

Comment A: Clear summer day, sun is greater than 60 degrees above horizon
Comment B: Summer day with a few broken clouds or clear day with sun, 35-60 degrees above horizon
Comment C: Fall afternoon or cloudy summer day or clear summer day with sun 15-35 degrees above horizon
Comment D: Fraction of sky covered by clouds: 1/2 or more = 50% or greater; less than 1/2 = less than 50%

The information on this page came from the class notes for ABEN 475: Environmental Systems Analysis (Cornell University). Page vi-19. He cited:
Turner, D.B. 1970. Workbook of Atmospheric Dispersion Estimates. USEPA, Washington, DC., and
Masters, G. M. 1991. Introduction to Environmental Engineering & Science. Prentice Hall, Englewood Cliffs, NJ.

Questions, Comments about air pollution modeling? Contact x-man@asu.edu.