PART II: OTHER TEMPERATURE VARIATIONS
WITH RESPECT TO THOSE ALONG A RIVER
surface roughness, which modifies lapse tempera-
INTRODUCTION
ture structure along or in the vicinity of hills or
Part I introduced the concept of the using the
mountains. Although Geiger's (1965) descriptions
air temperature observed along the plane coinci-
of drainage winds, sink holes, and cold valleys
dent with the bank of the Connecticut River, near
are well respected, there are significant differ-
44N latitude, as a reference temperature to ex-
ences of opinion regarding the relative contribu-
amine the processes responsible for large morn-
tion of cold air drainage and resident stagnation
ing air temperature differences observed in the
to diminished air temperatures in basins.
region. The logarithms of temperature difference
Magono et al. (1982) quite successfully mod-
among points along this plane were normally dis-
eled the horizontal distribution of winter tem-
tributed, and the geometric standard deviation of
peratures in Hokkaido, but were not able to model
temperature difference was quite similar along a
the extremely cold air found in small basins and
30-km segment of the river valley. Temperature
narrow valleys on the coldest days. They con-
differences of the greatest magnitude occurred
ducted an additional field experiment in the
most frequently under inversion and over deep-
Moshiri Basin, which they proposed produced
est snow cover. This report will apply the tech-
the coldest air in Hokkaido. They found an inver-
niques of measurement and analysis described in
sion to form more rapidly in the basin, which
Part I to examining the much larger temperature
decoupled the basin from the down valley winds
differences observed in hilly terrain east of the
that continued to circulate heat through the night
Connecticut River.
along the adjacent slopes. Maki et al. (1986), Kondo
It is well known, and summarized by Clements
(1986), and Maki and Harimaya (1988) studied
(1989), that basins and valleys experience over-
and modeled the heat budget in this and other
night air temperatures that are lower than those
complex Hokkaido basins. Their models predict
found at nearby ridges or extensive plains. Miller
nocturnal winter cooling to be greater in basins
(1956a,b) studied the influence of snow cover,
than on flat terrain, and also that nocturnal win-
intercepted snow, and vegetation on air tempera-
ter cooling will be greater at the base than at the
ture in the Sierra and Rocky Mountains, showing
tops of mountains. The mountain (or hill) tops are
a decoupling of the surface layer. We propose
not as frequently decoupled from tropospheric
that principles of polar and mountain meteorol-
heat advection. Downslope drainage may also in-
ogy can be synthesized with smaller distance scale
duce circulation of this warmer air along slopes.
concepts of nocturnal inversion formation by
Geiger (1965) provided marvelous insight to
Andre and Mahrt (1982), Arya (1981), Yamada
local climate variation. The observation, measur-
(1979), and Sutherland (1980), and the winter ba-
ing, and experiment sites designated in Figure 9
sin flow concepts of Maki and Harimaya (1988),
reflect these, and later, ideas of Geiger (1965, 1969).
to examine the differences of surface air tempera-
The measuring points were chosen to include sev-
ture observed in the Connecticut Valley by Hogan
eral apparent cold air drains and locations similar
and Ferrick (1990).
to those representative of microclimates given by
Nakamura and Magono (1982) showed that air
Geiger, but some more specific recent studies
temperature just above a snow surface dimin-
dominated the experiment plan. Measuring points
ishes with wind speed, but that the air tempera-
reflecting hamlets (Landsberg 1981), basins (Maki
ture at conventional screen height of 1.25 m
et al. 1986), slopes (Maki and Harimaya 1988),
becomes a minimum when wind speed 9 m above
barriers (Baines 1979), and forest/field bound-
the surface is about 1 m/s. This dependence of
aries (Raynor 1971) were selected to examine the
the "surface" (i.e., 1.25-m) air temperature on wind
influence of these cultural, topographic, and natu-
speed a few meters above apparently contributes
ral surface features. Raynor's (1971) boundaries
to the production of "surface" temperature dif-
and Baines' (1979) barriers to flow in the form of
ferences of several degrees over horizontal dis-
narrowing or widening of tributary valleys, small
tances of a few hundreds of meters in snow-
ridges, woods, and forests were used to define
covered terrain. It also induces "surface" tem-
the boundaries of some slopes and basins for
perature variation in conjunction with slope and
analysis.
13
Previous Page
