800
31
32
30
a. 20 Jan '94
31
31
0700-0805
31
32 (C temp.)
32
34
32
34
35
33
31
600
35
32
34
39.6
32
36
34
39.1
36
37
38
37
34 36
34
36
35
37
37
400
m
u L
P
O
S
800
32 31
b. 27 Jan '94
31
31
32
31
31
32
35 (C temp.)
34
32
34
35
33
32
33
600
34
32
32
33
33
34
35
33
35
34
33
35
34
35
33
33
33
400
0
10
20
30
Chord (km)
Figure 21. Temperatures observed relative to the topographic cross section along PSL on 20 and
27 January 1994. Thin ice fog akin to the "clear sky precipitation" observed at the South Pole
occurred along m and north of O on 27 January.
Temperatureterrain cross sections of morning
and the temperatures at points used in the river
plane analysis of Part I differ by less than 2C.
surface air temperature measured on 20 and 27
January 1994 are shown coincident with terrain
Cold advection continued to produce morning
temperatures of 30C through mid-February
features along the Z-W-A path in Figure 20 and
the P-S-L path in Figure 21. The minimum tem-
1994, and "exploration" was conducted on sev-
peratures observed at W (since 1988) occurred on
eral mornings to determine if some other nearby
these days, 38.9C on 20 January and 39.1C on
basins experienced lesser temperatures than those
27 January 1994. The temperature gradients sur-
studied. Terraintemperature cross sections ob-
rounding basins I and II were similar to those of
served 2 and 10 February 1994 are given in Figure
other snow-covered periods shown in Figure 3.
22, in similar format to Figure 21. These cross
Basins I and II had lesser temperatures than Mt.
sections were obtained along a path from Z ex-
Washington on both of these mornings, and sig-
tending across basin II and then along a north-
nificant warming had already occurred at Mt.
easterly radial following the road shown in Figure
Washington 27 January. It is important to note
9, passing through some additional small and large
that on 20 January, air temperature of 39.6C
basins. The temperatures observed northeast of
was observed concurrent with ice fog along flats
basin II are comparable to those south of the ba-
at mO along the lower river basin. This was the
sin, and no colder air was found along this cross
only observation of record where the coldest air
section on these or other days of exploration. The
of a morning was measured along this segment of
temperatures observed at several elevations along
the observation path, and it occurred under a
this transect are quite similar to those observed
very low (<15-m) surface inversion indicated by
along the usual observation path.
the flattening of smoke plumes of house chim-
Some similar exploration was conducted in the
neys. The general slope warmer-basin colder re-
winter of 199192, concurrent with the extension
lationship remains on these very cold mornings,
of the river level analysis to bridge H, described
25
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