Table 9. Frequency distribution of temperature difference along a
narrow stream valley.
Elevation
Temperature distribution
Location
(m)
84th%
Median
16th%
GSD
Stability
Along PO
122130
0.5
0.2
<0.1
2.5
L
j
180
0.9
0.4
<0.1
2.3
L
5
181
1.1
0.5
0.1
2.2
L
4
188
1.3
0.6
0.2
2.3
L
3
189
1.2
0.5
0.2
2.3
L
2
204
1.5
0.8
0.3
2.0
L
1
223
1.3
0.6
0.2
2.1
L
W
230
2.4
1.3
0.2
1.8
L
Along PO
122130
1.0
0.4
0.1
2.5
I
j
180
1.4
0.6
0.2
2.4
I
5
181
1.8
0.9
0.2
2.0
I
4
188
1.7
0.8
0.2
2.0
I
3
189
1.7
0.8
0.2
2.0
I
2
204
2.4
1.0
0.3
2.4
I
1
223
2.9
1.2
0.4
2.4
I
W
230
3.0
1.6
0.5
2.1
I
and originates and terminates in wider flatter ba-
(II) surrounding W under general lapse continues
sins.
above 1 and 2, but allows some exchange with
The data used to produce the vertical tempera-
layers of warmer air from higher elevation. Inter-
ture profiles plotted in Part II, Figures 10 and 11,
mittent exchange immediately beneath the inver-
were combined into two sets dependent on lapse
sion or inflection may alter the air temperature at
or inversion structure. Frequency analysis of tem-
points 3, 4, and 5 (basin III) giving the appearance
perature difference at each point from j at the
of a superadiabatic lapse rate coincident with the
western most edge of Basin III to W in Basin II are
valley as noted in Part II. The stratification over
given in Table 9. The five air temperature differ-
snow-covered basins II and III only allows cold
ences at the near river observing points between
air drainage down the valley when lapse coin-
the Piermont (P) and Orford (O) bridges have
cides with minimal snow cover.
been combined to provide PO reference differ-
ences for the same days in Table 9. The median
and GSD of the distribution of these differences
FREQUENCY OF
SUBZERO (<17.8C) DAYS
provides an insight for comparison of the trend in
temperature difference.
IN THE STUDY AREA
The temperature differences observed at 3, 4,
5, and j, and the GSD of the differences, are quite
Climatological data cited (NOAA 1982) in the
comparable under both lapse and inversion con-
Introduction to Part I showed a great variation in
the frequency of subzero (<17.8C) days in the
ditions. There is systematically less difference at j
which is closest in proximity to the Piermont
vicinity of the study area. The results of observa-
bridge (P) reference point. It appears that the chan-
tions presented to this point have primarily re-
neling of flow over snow cover observed by
lated to temperature differences, with respect to
Yasuda did occur here under inversion condi-
variation in topography and snow cover within
tions. The colder air from the basin (II) surround-
the study area. The number of observations of
subzero (<17.8C) and lesser air temperatures at
ing W appears to extend to 1, along the side of the
valley on some mornings with inversion. The stan-
several observation points are tabulated in Table
dard deviation of temperature difference at points
10. The tabulation is ordered by decreasing fre-
1 and 2 approach that of W under lapse and de-
quency of occurrence of subzero mornings.
part from that of W under inversion. We interpret
These observations represent 158 observation
this as evidence that the temperature inflection or
days over three winters when no rain or super-
inversion that is generally present over the basin
cooled fog occurred, and should not be consid-
33
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