DISCUSSION: The Koppen climate classification divides Earth's climate into five main categories (i.e., tropical, dry, mild mid-latitude, severe mid-latitude, and polar) and many subtypes. This classification is important because it gives you some idea of what type of weather to expect if you plan to visit or move to a certain place. In addition, the classification can be used to assess how the climate is changing over time.
There is currently some debate as to how to properly classify the climate in southern Australia, specifically, near Adelaide, as described in this ABC News story. Currently, Adelaide is classified as a Mediterranean climate type, a sub-category of the mild mid-latitude category. This climate type is characterized by hot, dry summers as the subtropical highs typically found near 30 degrees north and south move poleward. Winters are cool and wet as mid-latitude cyclones pass over the area and the subtropical high retreats toward the equator. During the winter, Mediterranean climates typically have relatively light rain distributed over a large number of days. However, the rain during the winter in Adelaide tends to fall in heavy, short bursts which is more like the rainfall that falls in a monsoon-type climate.
Typical monsoon climates are driven by seasonal changes in surface heating as illustrated in the figure above (courtesy of pmfias.com). During the summer, India and southern Asia heats up more than the surrounding ocean causing low pressure to develop over the land. This causes the intertropical convergence zone (ITCZ) to move over land and causes warm, moist air to flow onshore. This flow results in heavy rainfall over land. The opposite occurs over land in winter. The land cools more than the adjacent ocean, high pressure develops, and offshore flow inhibits rainfall.
The rainfall in Adelaide in winter is driven by mid-latitude cyclones, not directly by large-scale changes in surface heating and a reversal in wind direction, but the intensity of the rain is similar to what occurs in a monsoon climate. Hence, the climate of Adelaide is sort of a cross between a Mediterranean and monsoon climate. Perhaps a new climate subtype should be developed that better describes the climate of southern Australia.
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© 2018 Meteorologist Dr. Ken Leppert II
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