Environmental Engineering Reference
In-Depth Information
poleward side of the Hadley cell (see Chapter 6). Weaker polar divergence is
strengthened by the katabatic effects of ice sheets and accounts for mid- to high-latitude
loess sheets. Ocean circulation also contributes to coastal deserts through the upwelling
of cold currents on western coasts in the case of the Mojave, Sonora and Atacama deserts
of the Americas, the Namibian desert of south-west Africa and the Western Australian
desert (Figure 1).
Zonal climate does not account wholly for desert location and landsystems.
Morphotectonics inevitably superimpose their influence through rain-shadow effects,
altitude and the deflatable products of erosion. Coastal cordillera reinforce the arid
impact of coastal upwelling by extending their rain shadow across continental interiors.
The latter is most pronounced in the basin-range region of the south-west United States
and leeward of the still rising Tibetan plateau, whose elevation by 3ยท5 km during 2 Ma of
the Plio-Pleistocene greatly extended north-central Asian interior deserts. Tectonic uplift
and subsidence also play active and passive roles respectively in hot desert denudation
processes, sourcing or collecting aeolian materials, and are hence linked with their
geomorphic landsystems.
Figure 1
The distribution of hot and polar deserts.
Source: Partly after Collinson (1986).
