Geoscience Reference
In-Depth Information
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
Notes
Even for hot, moist air,
¯
v
is only a few degrees
greater than the air temperature.
2 ATMOSPHERIC COMPOSITION,
MASS AND STRUCTURE
5
The official definition is the lowest level at which the
lapse rate decreases to less than, or equal to, 2°C/km
(provided that the average lapse rate of the 2-km
layer does not exceed 2°C/km).
1
Mixing ratio = ratio of number of molecules of ozone
to molecules of air (parts per million by volume,
ppm(v)). Concentration = mass per unit volume of
air (molecules cubic metre).
2
K = degrees Kelvin (or Absolute). The degree symbol
is omitted.
°C = degrees Celsius.
°C = K - 273.
Conversions for °C and °F are given in Appendix 2.
3 SOLAR RADIATION AND THE GLOBAL
ENERGY BUDGET
1
The radiation flux (per unit area) received normal
to the beam at the top of the earth's atmosphere is
calculated from the total solar output weighted by
1/(4
3
Joule = 0.2388 cal. The units of the International
Metric System are given in Appendix 2. At present
the data in many references are still in calories; a
calorie is the heat required to raise the temperature
of 1 g of water from 14.5°C to 15.5°C. In the United
States, another unit formerly in common use is the
Langley (ly) (ly min
-1
= 1 cal cm
-2
min
-1
).
10
11
m, since the surface area of a sphere of radius r (here
equivalent to D) is 4
π
D
2
), where the solar distance D = 1.5
π
r
2
- i.e. the radiation flux is
(6.24
10
7
Wm
-2
) (61.58
10
23
m
2
)/4
π
(2.235
10
22
) = 1367 W m
-2
.
4
The equation for the so-called 'reduction' (actually
the adjusted value is normally greater!) of station
pressure (p
h
) to sea-level pressure (p
0
) is written:
2
The albedos refer to the solar radiation received on
each given surface: thus the incident radiation is
different for planet earth, the global surface and
global cloud cover, as well as between any of these
and the individual cloud types or surfaces.
g
o
p
o
= p
h
exp -----
()
Z
p
R
d
¯
v
6 ATMOSPHERIC MOTION:
PRINCIPLES
where R
d
= gas content for dry air; g
0
= global
average of gravitational acceleration (9.8 ms
-2
); Z
p
=
geopotential height of the station (geometric height
in the lowest kilometre or so);
¯
v
= mean virtual
temperature. This is a fictitious temperature used in
the ideal gas equation to compensate for the fact that
the gas constant of moist air exceeds that of dry air.
1
The centrifugal 'force' is equal in magnitude and
opposite in sign to the centripetal acceleration. It is
an apparent force that arises through inertia.
2
Apparent gravity, g = 9.78 m s
-2
at the equator,
9.83m s
-2
at the poles.
