Introduction

The purpose of this chapter is to illustrate how climates in the southern hemisphere can be 'explained' (to quote the book's title) in terms of what has been discussed in previous chapters, mostly concerning weather. Climate is the product of prevailing weather, as mentioned in Section 1.1, i.e. of the shifting highs and lows which occur at particular latitudes and linger in particular regions (Figures 12.1 and 13.16), creating average patterns of pressure (Figures 1.8 and 12.7) and winds (Figures 12.1-2, 12.46 and 12.12).

As regards geographical factors, we have seen that the climate of any place depends chiefly on the following six:

1 the hemisphere, which determines the warm season outside the Tropics, or the wet season between them;

2 the latitude, which controls daylength (Table 2.1), annual mean temperature (Section 3.2), seasonal range (Section 3.3), rainfall (Table 10.1), and prevailing winds (Section 12.1);

3 the elevation, which influences the amount of UV radiation (Section 2.6), the net radiation (Section 2.8), mean temperature (Section 3.2) and, to a lesser extent, its daily and annual range (Sections 3.3 and 3.4), as well as the precipitation (Section 10.3), whilst the location upwind or downwind of a mountain range determines rainfall and affects temperature (Note 7.E);

4 the ocean circulation (and hence the pattern of sea-surface temperatures), which affects conditions at the coast (Table 11.2);

5 the distance downwind of an ocean, which governs annual and daily temperature ranges (Section 3.4) and rainfall (Section 10.3); and

6 the local topography, which influences the temperature (e.g. frost hollows, Section 3.6) and local airflow (Section 14.3).

These relationships are summarised in Table 16.1.

We will now consider climates in general, in terms of their classification, and then the effects of the six factors mentioned above on the climates of the main land areas of the southern hemisphere.

Table 16. 1 The effects of geographical factors on climate elements. For instance, an increase of elevation lowers the temperature except in a valley bottom at night. '(S3.2)', for instance, means that further information is given in Section 3.2. '(T1.1)' refers to Table 1.1.

Water

Climate scale

Geo

vapour

graphical

Radiation

Mean temp.

Annual

Atmos. uplift Precipitation pressure

(Tl.l)

factor

(S2.4)

(S3.2)

range (S3.3)

(S7.4)

(SI 0.3)

(S6.4)

Global

Latitude

Various

Less *

More

Various

Various

Less

Synoptic

Elevation

More

Less

-

More

Various

Less

SST upwind

-

More

-

More

More

More

Distance

More

Various

More

-

Less

Less

inland

Meso and

Landformt

Various

Various

-

Various

Various

-

topo

Surface condition

Micro

Various

Various

Various

* That is, an increase of latitude is associated with a lower temperature t That is, slope, orientation, albedo, wetness, runoff

* That is, an increase of latitude is associated with a lower temperature t That is, slope, orientation, albedo, wetness, runoff

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