Geoscience Reference
In-Depth Information
A. N. Strahler (1969) proposed a simple but effective
genetic classification of world climates, based on the
fundamental planetary mechanisms. Following a tripar-
tite division by latitude (low, middle and high), regions
are grouped according to the relative influence of the
ITCZ, the subtropical high-pressure cells, cyclonic
storms, high-latitude frontal zones and Polar/Arctic
air sources. This gives fourteen classes and a separate
category of Highland climates. Briefly, these are as
follows:
cP air. Hot summers and cold winters give a large
annual temperature range.
10 Humid continental climate (35° to 60°N). Central
and eastern continental locations. Frontal cyclones.
Cold winters, warm to hot summers, large annual
temperature range. Well distributed precipitation.
(C) High-latitude climates controlled by polar and
Arctic airmasses.
11 Continental sub-Arctic climates (50° to 70°N).
Source region for cP air. Very cold winters, short,
cool summers, extreme annual temperature range.
Year-round cyclonic precipitation.
12 Marine sub-Arctic climate (50° to 60°N and 45° to
60°S). Dominated by the winter Arctic frontal zone.
Cold, moist winters, cool summers; small annual
temperature range.
13 Polar tundra climates (north of 55° to 60°N and
south of 60°S). Arctic coastal margins dominated
by cyclonic storms. Humid and cold, moderated
somewhat by maritime influences in winter.
14 Ice sheet climates (Greenland and Antarctica).
Source regions of Arctic and Antarctic air. Perpetual
frost, low snowfall except near coasts.
(A) Low-latitude climates controlled by equatorial and
tropical airmasses.
1 Wet equatorial climate (10°N to 10°S; Asia 10°S to
20°N) - converging equatorial and mT air masses
produce heavy convectional rains; uniform temper-
ature.
2 Trade wind littoral climate (10° to 25°N and S) -
high sun trade winds alternate seasonally with
subtropical high pressure; strong seasonality of
rainfall, high temperatures.
3 Tropical desert and steppe (15° to 35°N and S) -
dominance of subtropical high pressure gives low
rainfall and high maximum temperatures with
moderate annual range.
4 West Coast desert climate (15° to 30°N and S) -
dominance of subtropical high pressure. Cool seas
maintain low rainfall with fog and small annual
temperature range.
5 Tropical wet - dry climate (5° to 15°N and S) - high
sun wet season, low sun dry season; small annual
temperature range.
(D) Highland climates - localized and varied in
character.
D CLASSIFICATIONS OF CLIMATIC
COMFORT
The body's thermal equilibrium is determined by
metabolic rate, heat storage in body tissues, radiative
and convective exchanges with the surroundings, and
evaporative heat loss by sweating. In indoor conditions,
about 60 per cent of body heat is lost by radiation and
25 per cent by evaporation from the lungs and skin.
Outdoors, additional heat is lost by convective transfer
due to the wind. Human comfort depends primarily
on air temperature, relative humidity and wind speed
(Buettner 1962). Comfort indices have been developed
by physiological experiments in test chambers. They
include measures of heat stress and windchill.
Windchill
describes the cooling effect of low temper-
ature and wind on bare skin. It is commonly expressed
via a windchill equivalent temperature. For example,
a 15 m s
-1
wind with an air temperature of -10°C has a
(B) Mid-latitude climates controlled by both tropical
and polar airmasses.
6 Humid subtropical climate (20° to 25°N and S) -
high sun moist mT air and low sun cyclones give
well-distributed annual rainfall with moderate
temperature regime.
7 Marine west coast climate (40° to 60°N and S) -
windward coasts with cyclones all year. Cloudy;
well-distributed rainfall with low sun maximum.
8 Mediterranean climate (30° to 45°N and S). Hot,
dry summers associated with the subtropical highs
alternate with winter cyclones bringing ample rain.
9 Mid-latitude continental desert and steppe (35° to
50°N and S). Summer cT air alternates with winter
