Geoscience Reference
In-Depth Information
SHEBA Turbulence Mast Temperatures
-
1.625
a
-
1.6375
4 m
8 m
-
1.65
167
167.5
168
168.5
169
169.5
170
170.5
171
SHEBA Turbulent Heat Flux
5
b
0
5
-
-
10
4 m
8 m
-
15
167
167.5
168
168.5
169
169.5
170
170.5
171
Fig. 8.2 a
Three-hour average turbulence mast temperatures. Shaded circles represent local solar
zenith,atapproximatelyUT
+
23h.
b
Corresponding heat fluxmeasurements: ρ
c
p
w
T
(see also
colorplate on p. 208)
The general picture of diurnal heating and nocturnal cooling was supported by
turbulentheatfluxmeasurementsattheTIClevels(Fig.8.2b).Althoughnotsoclean
as the temperature records, heat flux also showed a diurnally varying signal with
maximumdownward(negative)fluxatorshortlyafterlocalnoon,andupwardheat
flux at night (solar nadir). There was an upward overall trend in temperature over
thefourdays,typicalofSHEBAduringtheearlysummer.Thiswasconsistentwith
the increase in temperature elevation above freezing
,shownin
Fig.8.3a,suggestingthatthetrendresultedfromlocalheatingratherthanadvection
of the ice station into a different water type. Incoming shortwave radiation was
strongduringthisperiod(Fig.8.3a),reachingamaximumofabout600Wm
−
2
late
onday168,butwith significantday-to-dayvariation.
There were times during the period when heat flux at both levels approached
zero (e.g., days 168.75and 169.625in Fig. 8.2b).Again reasoning that these times
would providean accurate “calibrationbath,” we calculated the difference in mean
temperaturebetweentheTICsensors,whichwasabout1.8mK.Adjustingthelower
thermometer by this amount for all the samples then provided an estimate of the
temperaturegradientbetween4.2and8.2masafunctionoftime.Comparisonofthe
negativetemperature gradient with the average heat flux from the two TICs shows
the time series to be well correlated, despite the small magnitudes of both (e.g., a
maximum absolute temperature difference between the two SBE thermometers of
(
∆
T
=
T
−
T
f
(
S
))
