Geoscience Reference
In-Depth Information
high pressure cell in October allows depressions to move and form over the relatively warm
Mediterranean Sea, giving well-marked orographic winds (e.g., mistral) and stormy, rainy winters.
Spring is an unpredictable season marked by the collapse of the Eurasian high pressure cell to the
north and the strengthening of the Saharan-Azores anticyclone. In summer, the latter gives dry,
hot conditions with strong local southerly airstreams (e.g., scirocco). The simple winter rainfall
maximum is most characteristic of the eastern and southern Mediterranean, whereas in the north
and west, autumn and spring rains become more important. North Africa is dominated by high
pressure conditions. Infrequent rainfall may occur in the north with extratropical systems and to
the south with Saharan depressions.
Australian weather is determined largely by traveling anticyclone cells from the southern Indian
Ocean and intervening low pressure troughs and fronts. In the winter months, such frontal troughs
give rains in the southeast. The climatic controls in New Zealand are similar to those in southern
Australia, but South Island is greatly influenced by depressions in the southern westerlies. Rainfall
amounts vary strongly with the relief.
The southern westerlies (30-40
°
to 60-70
°
S) dominate the weather of the Southern Ocean. The
strong, mean zonal flow conceals great day-to-day synoptic variability and frequent frontal
passages. The persistent low pressure systems in the Antarctic trough produce the highest year-
round zonally averaged global cloudiness.
The Arctic margins have six to nine months of snow cover and extensive areas of permanently
frozen ground (permafrost) in the continental interiors, whereas the maritime regions of northern
Europe and northern Canada-Alaska have cold, stormy winters and cloudy, milder summers
influenced by the passage of depressions. Northeast Siberia has an extreme continental climate.
The Arctic and Antarctica differ markedly owing to the types of surface - a perennially ice-covered
Arctic Ocean surrounded by land areas and a high Antarctic ice plateau surrounded by the Southern
Ocean and thin seasonal sea ice. The Arctic is affected by mid-latitude cyclones from the North
Atlantic and in summer from northern Asia. A surface inversion dominates Arctic conditions in
winter and year-round over Antarctica. In summer, stratiform cloud blankets the Arctic and
temperatures are near 0
°
C. Sub-zero temperatures persist year-round on the Antarctic continent
and katabatic winds dominate the surface climate. Precipitation amounts are low, except in a few
coastal areas, in both polar regions.
•
Compare the climatic conditions in maritime and continental locations in the major continents,
and in your own region of the world, using available station data from reference works or the Web.
•
Consider how major topographic barriers in the Americas, Western Europe, New Zealand and
so on modify the patterns of temperature and precipitation in those regions.
•
Examine the seasonal distribution of precipitation in different parts of the Mediterranean Basin
and consider the reasons for departures from the classical view of a wet winter/dry summer
regime.
•
Examine the spatial extent of 'Mediterranean-type' climates in other continents and the reasons
for these conditions.
•
Compare the climatic characteristics and controls of the two polar regions.
•
What are the primary causes of the world's major deserts?
