Geoscience Reference
In-Depth Information
Site characteristics and meteorological variables for the three Australian
sites considered in question 10.
Table 26.4
Variable
Units
Site 1
Site 2
Site 3
Maximum air temperature
(
°C
)
29.10
35.00
23.00
Minimum air temperature
(
°C
)
17.90
21.40
11.50
Dry bulb temperature
(
°C
)
24.00
n/a
n/a
Wet bulb temperature
(
°C
)
19.00
n/a
n/a
Relative humidity
(%)
n/a
39
n/a
Dew point
(
°C
)
n/a
n/a
11.00
Wind measurement height
(m)
10.00
10.00
2.00
Wind speed
(m s
−1
)
5.60
4.70
3.70
Day of year
(none)
40
46
52
Latitude
(deg)
−19.62
−15.78
−33.13
Cloud fraction
(none)
0.40
0.10
n/a
Number of bright sunshine hours
(hours)
n/a
n/a
4.000
Elevation
(m)
12
44
30
Assigned site humidity
(none)
Humid
Arid
Humid
Measured pan evaporation
(mm)
7.6
11.2
4.9
Selected value for Albedo
(none)
0.23
0.23
0.23
Albedo of open water
(none)
0.08
0.08
0.08
vapor pressure is 9.86 kPa [from Equation (2.17)], vapor pressure is 2.46
kPa [from Equation( 2.19)], specific humidity is 0.0152 kg kg
−1
[from
Equation (2.9], and the gas constant for moist air is 289.2 J kg
−1
K [from the
equation given in the question].
(b) At Kitt Peak where the altitude is 7080 ft, or 2158 m, air temperature is
312.01 K assuming the local lapse rate is 0.0065 Km
−1
, and air pressure is
90.1 kPa [from Equation (3.13)].
(c) From Equation (2.21), at the ambient air pressure on Kitt Peak water boils
at 96.5°C.
(d) The warmed parcels of air near the desert floor have a temperature of
50.56°C or 323.7 K, and their vapor pressure is still 2.46 kPa. They will
saturate at a dew point temperature of 20.85°C [from Equation (2.21)], or
at 294.0 K. If the ascending parcels cool at the adiabatic lapse rate of
0.00968 Km
−1
, they would need to reach a height of 3068 m above the
desert floor before their temperature falls from 323.71 K to 294.0 K and
they saturate. The warmed air parcels will lose buoyancy at a height
h
at
which their temperature has fallen such that it is equal to that of the
surrounding air, i.e., when (323.7 - 0.0097
h
) = (318.17 - 0.0065
h
), thus at
about 1500 m above the desert floor. Consequently there is unlikely to be
any convective cloud on this day because the warmed air parcels lose
buoyancy at
∼
1500 m above the desert floor before they can saturate at
about 3000 m.
