Dry climates (B)

Group B, dry climates, have rainfall too low for plant growth. They cover huge areas, from 15° to 60° N and S.

• At 15°-30° they lie under the subtropical highs, where sinking air and temperature inversion prevent rain. On the western margins of continents beside cold currents (especially the west coast of South America) they reach further towards the equator, right onto the coast.
• At 35°-60° they are in continental interiors that moist sea winds cannot reach, often ringed by mountains.

Types: steppe or semi-arid (BS) and desert (BW); subdivided into subtropical steppe (BSh) and subtropical desert (BWh) at 15°-35°, and mid-latitude steppe (BSk) and mid-latitude desert (BWk) at 35°-60°.

Subtropical steppe and desert (BSh, BWh):

• The steppe lies between humid and dry climates and gets slightly more rain than the desert, enough for sparse grassland.
• Rainfall in both is highly variable; the variation hurts life in the steppe more than in the desert, often causing famine.
• Desert rain comes in short, intense thundershowers that do little for soil moisture. Fog is common in coastal deserts beside cold currents.
• Summer maximum temperatures are very high, with large annual and daily ranges. The book quotes 58°C at Al Aziziyah, Libya (1922); that reading has since been rejected, and the accepted world record is 56.7°C at Death Valley, USA.

Example (new): the western part of Rajasthan around Jaisalmer, with very little and unreliable rain, scorching summers and cold winter nights, is a hot desert (BWh), while the drier grasslands farther east toward Jodhpur grade into steppe.