PART III: SOME EXAMPLES OF THE INFLUENCE OF CULTURAL AND
PHYSICAL FEATURES ON MORNING AIR TEMPERATURE
measured at a similar elevation south of the ham-
INTRODUCTION
let in Table 8. The tabulation is again stratified by
We established in Parts I and II that the small
stability and snow cover, and the temperatures
variation in winter morning air temperature that
shown are temperature differences, referenced to
occurs in the plane coincident with the banks of
the river plane at P. The mean temperature differ-
the Connecticut River is related to stability of the
ence at u , 29.4 km from P, is shown as a reference.
air overlaying the valley and the continuity of
Note that the mean temperature difference at u
snow cover. The vertical temperature structure of
was shown to approximate the 84th percentile of
the lower 100 m of air overlaying this plane (i.e.,
the frequency distribution of temperature differ-
that below 230-m elevation) is dependent on the
ences between P and u in Part I. The mean tem-
temperature structure of the air above and the
perature difference, exceeded in less than 0.16 of
continuity of surface snow cover. The frequency
cases in this data set, is shown here for more
of occurrence of inversions, and the magnitude of
direct comparison to other heat island analyses.
inversion, increase with the thickness and conti-
We have omitted temperature differences mea-
nuity of snow cover. The mean vertical tempera-
sured under lapse in Table 8, as these are consis-
ture structure in the study area and analysis of
tently small, in agreement with Lowry (1977).
temperatures in basins just above river level, by
There is very little temperature difference under
Hogan and Ferrick (1993), indicate adjacent flats
inversion when less than 10 cm of snow is present.
or basins separated by a discontinuity or barrier
When snow exceeds 10 cm, the temperature along
the green is 0.5C greater in the mean than the
had comparable temperatures. The techniques of
analysis developed in Parts I and II will be used
adjacent temperature, although other nearby tem-
to examine winter morning temperature varia-
peratures are comparable. This indicates that the
tion associated with cultural and surface features.
wooden buildings along the green, snow removal
around the perimeter, and the presence of several
idling vehicles along the green induce very little
modification of the surface air temperature field.
ANALYSIS OF TEMPERATURE
This is probably due to the green, and the sur-
DIFFERENCE OCCURRING
rounding area, providing a relatively uniform
WITHIN A HAMLET
snow-covered surface plane much greater in area
The magnitude of influence of physical or cul-
than that disturbed by buildings and roads. A
tural discontinuities on the morning air tempera-
much more sophisticated experiment would be
ture can be estimated by comparison with adjacent
required to identify a heat island associated with
temperature, in a similar manner to that described
a hamlet of this size. The small, nearly level "flats"
by Lowry (1977) and Landsberg (1981). Landsberg
are not bounded basins but are embedded on
(1981) showed that the initial construction be-
slopes. They are systematically warmer than the
ginning the "new town" of Columbia, Mary-
Connecticut River reference plane.
land, induced a 1C heat island about the
construction site. Our initial work (Hogan
Table 8. Temperature differences observed at and near the
and Ferrick 1990) showed "downtown"
Lyme Green, with respect to Piermont bridge P tempera-
Hanover, New Hampshire, to be 1 to 2C
tures.
warmer than adjacent open fields and rec-
Snow cover category
reational areas at the same elevation when
Elevation
<3 cm
310 cm
1030 cm
>30 cm
(C)
(C)
(C)
(C)
the ground was snow covered. We were
Location
(m)
not able to distinguish or attribute a tem-
Lyme Green
171
()0.25
1.05
1.30
4.10
perature influence in comparing hamlets
Flat N of t
160
()0.55
1.05
0.80
3.50
of about 30 buildings to surrounding ter-
rain using a single winter of data. Tem-
Flat at t
177
0.15
1.15
1.60
4.70
peratures observed along the green in
Flat S of t
177
0.35
0.75
0.90
3.70
Lyme, noted by name in the map in Fig-
River at u
122
1.15
1.40
1.10
2.20
ure 3 are compared with temperatures
30
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