Geoscience Reference
In-Depth Information
Table A1.2
Radiation budget criteria for major climatic types. Units W m
-2
.
Climatic type
Annual short wave
Annual long wave
Annual range of short wave
Land
Tropical:
>140
<70
<100
Wet>140
<50
<100
Wet/dry
>140
>50
<100
Desert>90
Steppe
70<L
N
<90
Subtropical
>140
<70
>100
Temperate
100<S
N
<140
<70
Boreal
50<S
N
<100
<70
Polar
0<S
N
<50
<50
Oceans
Tropical
>210
<140
Convergence and stratus
170<S
N
<210
<140
Subtropical
>150
>140
Temperate
80<S
N
<150
Polar
0<S
N
<80
Source
: From Smith
et al
. (2002).
radiation and advection) and outputs (sensible heat and
latent heat), and their seasonal range. On this basis,
sixty-two climatic types were distinguished (in six broad
groups), and a world map was provided. Smith
et al
.
(2002) determine net short-wave and net long-wave
radiation criteria for a climate classification with nine
global types that is similar to Köppen's, developed by
Trewartha and Horn (1980). Table A1.2 summarizes
their criteria.
W. Lauer has prepared a new classification and map
of world climate types based on thermal and hygric
thresholds for both natural vegetation and agricultural
crops. The limits of the four primary zones (tropical,
subtropical, mid-latitude and polar regions) are deter-
mined from a radiation index (duration of daily sunshine
hours). Climate types are then based on a thermal index
(temperature sums) and a moisture index, which takes
account of the difference between monthly precipitation
and potential evaporation.
H. Flohn proposed one system in 1950. The major
categories are based on the global wind belts and
precipitation seasonality, as follows:
1
Equatorial westerly zone: constantly wet.
2
Tropical zone, winter trades: summer rainfall.
3
Subtropical dry zone (trades or subtropical high
pressure): dry conditions prevail.
4
Subtropical winter-rain zone (mediterranean
type): winter rainfall.
5
Extra-tropical
westerly
zone:
precipitation
throughout the year.
6 Subpolar zone: limited precipitation throughout
the year.
6(a) Boreal, continental subtype: summer rainfall;
limited winter snowfall.
7
High polar zone: meagre precipitation; summer
rainfall, early winter snowfall.
Temperature does not appear explicitly in the
scheme. Figure A1.2B shows the distribution of these
types on a hypothetical continent. Rough agreement
between these types and those of Köppen's scheme is
apparent. Note that the boreal subtype is restricted to
the northern hemisphere and that the subtropical zones
do not occur on the eastern side of a landmass. Flohn's
approach has value as an introductory teaching outline.
C GENETIC CLASSIFICATIONS
The genetic basis of large-scale (macro-) climates is
the atmospheric circulation, and this can be related
to regional climatology in terms of wind regimes or
airmasses.
