Geoscience Reference
In-Depth Information
RAINFALL
Cir
Canc
>500 mm per year
250-500 mm per year
0-250 mm per year
Figure 19.1. Mean annual precipitation in Asia. (After
The Times Atlas of Asia
,
2010.)
mountains on the planet, such as the Himalayas to the north of the deserts of India
and Pakistan. As a result, many of the Asian deserts are located in the rain shadow of
very high mountain ranges (e.g.,
Chapter 8
,
Figure 8.12
. In addition, the huge size of
the continent dictates that rainfall in the interior is both sparse and erratic, because the
moisture-bearing air masses from the ocean shed much of their precipitation within
the first few hundred kilometres of the coast (
Figure 19.1
).
The climate of this vast region is dominated by the summer monsoon in the south
and the winter monsoon in the north (
Figure 19.2
). Some precipitation is also derived
from the mid-latitude westerly air masses from the Atlantic via the Mediterranean that
bring modest amounts of snow and rain to the mountains north of the Tibetan Plateau,
such as the Tian Shan. The strength of the Siberian anticyclone determines the strength
of the winter monsoon. The summer monsoon is controlled by the pressure gradient
between land and sea, which is in turn controlled by the temperature contrast between
the ocean surface and the adjacent land. In fact, it is misleading to think in terms of
a single, monolithic summer monsoon. In China, for example, the summer monsoon
really consists of three quite independent monsoon systems, namely, the East Asian
monsoon originating from the Pacific Ocean, the Indian monsoon originating from
the Indian Ocean and the Plateau monsoon stemming from the Tibetan Plateau.
El Ni no-Southern Oscillation events are an additional influence contributing to
interannual precipitation variability in easternChina, northern Thailand and peninsular
India, and they are discussed in detail in
Chapter 23
. The sphere of influence of the
