148
Fie. 112.—Schematic diagram of heat-island circulation (redrawn from Lowry“)
cago area,
The weather maps show the broad seale framework
sources.
We drew SOs isopleths and shaded areas progres-
sively darker with mereasing concentration to show
pollution patterns at a glance. These are general patterns only—they are not meant to give details. For
example, where data were sparse, uniform concentration gradients were drawn. This is an obvious simplification. Others may be evident as we look at the
three cases in detail.
RESULTS AND DISCUSSION
Oo
mn
7
fF
—
t
tf
a
A
ua
on
tf
a
bo
pre
of each specific local event. The time sections show
the hour-to-hour relationships between SO. and
winds. These relationships are clearest in smoothed
data; therefore, we plotted hourly averaged winds and
SO. concentrations on the time sections. The purpose
of the meso-scale charts is to show instantaneousdistributions of SQe, winds, and temperature over Chicago, Thus the winds on these charts are J- to 5-min
averages, and temperatures are instantaneous. SOs
values are still 1-hr averages, though. to insure that
plotted values represent real effects and not nearby
—
o
(3) meso-seale charts showing winds,
temperatures and SO. concentrations over the Chi-
|
MiDWAY ——--——
— O'HARE
| ARGONNE ------
a
tions of SO. concentrations and winds at selected
stations; and
r
TEMPERATURE, (F )
We studied each case using three graphical aids:
(1) a surface weather map for the day; (2) time sec-
}
DATA AND PROCEDURES
{|
2
|
4
|
6
| | jf | f | tf
8 10 12 14 16 I8 20 22 24
19 JANUARY 1966, CST
Fic. 113—Diurnal temperature changes at Argonne, Midway. and O’Hare, 19 January 1966.
19
JANUARY 1966
19
o600 CST
GRB
JANUARY
1966
20 JANUARY [966
1800 CST
PIA
PIA
f
fF -
eif Ff)
fF OC
GRB
Bal /
I
f
[
—r
{
fF
{/
7
f
VOX
\_
\ sunrsce >
SN
o-2 kt
OT
FYE A
ov] 4 Ld
YR
XL
pe esN
err XN
PIA
fo aw
¢ Cl
gir, t
3 >
GRB
0600 CST
KEY
XQ
3-7 kt
at
RK
a-l2kt
13-17 kt
19 January 1966: A Possible Heat-Island Circulation Case
Fic. 114—Winds aloft at Peoria and Green Bay, 19-20
January 1966.
The 1200 CST* surface weather map (Figure 105)
shows an anticyclone covering the Midwest. Its center
was just west of Chicago. The pressure gradient over
* All times in this paper are CST.
Chicago was weak; hence winds were light. The 19th
was the third consecutive day that Chicago was in-