KLIMAT STREFY PODZWROTNIKOWEJ Klimatologia regionalna 1 Climate of subtropical zone KLIMAT STREFY PODZWROTNIKOWEJ Klimatologia regionalna 2 – Exception: monsoon climates – opposite situation KLIMAT STREFY PODZWROTNIKOWEJ Klimatologia regionalna 3 Internal subdivision of subtropical climates • Climate of western coasts (mediterranean): – Oceanic type – Internal seas type (Mediterranean Sea) • Climate of continental interior – Zone of extratropical travelling cyclones and western circulation is enlarged towards lower latitudes – Frequent convergence at polar folar front – Enhanced cloudiness and precipitation • Summer: – Predominance of tropical highs a little transposed towards higher latitudes – Domination of subsidence and free inversion (air stability) – Convection inhibition – Low cloudiness, high insolation, scarce precipitation KLIMAT STREFY PODZWROTNIKOWEJ Klimatologia regionalna 5 Geographic location of mediterranean climate • Relatively narrow coastal zone (<150 km wide) below 750-1500 m a.s.l., – Mediterranean Sea basin (this climate name is born here!) – California in N. America (in the USA) – central Chile – SW tip of Africa (Cape Town and vicinity) – Parts of southern Australia • Perth and vicinity in the SW • Adelaide and vicinity KLIMAT STREFY PODZWROTNIKOWEJ Klimatologia regionalna 6 Mediterranean climate (oceanic type) • Summer: – strong influence of E flank of an oceanic anticyclone – The most frequent air advection from higher latitudes – Oceanic current along the coast towards lower latitudes – Frequent upwelling of deep (and cold) oceanic water • Winter: western oceanic circulation prevails with intense cyclo- and frontogenesis • Relatively flat seasonal T range • Relatively cool summer • Strong breeze circulation (e.g. doctor) KLIMAT STREFY PODZWROTNIKOWEJ Klimatologia regionalna 7 Mediterranean climate (Mediterranean Sea basin) • Summer: – N peripheries of tropical anticyclone (clearly visible in the middle troposphere); weak low-level horizontal pressure gradient • Ethesian wind as an example of trade wind extremely distant from equator – Air subsidence and stagnation • Winter: – Pressure trough over Mediterranean Sea between the tropical high over N Africa and high pressure wedge along the axis of European continent – Convergence of SW and NE airstreams • Seasonal T range and summer T increase from W to E – Guess: Where the absolute T maxima might be expected in Europe? KLIMAT STREFY PODZWROTNIKOWEJ Klimatologia regionalna 8 Mediterranean climate; sunshine duration (SS) • SS is high, around twice as high as in neighbouring region of temperate latitudes (decideous forest of W coasts) – Exception: very narrow oceanic coasts with nocturnal and morning fogs – SS decreases towards higher latitudes • Relatively high SS also in cool half of the year because cyclonic episodes are rather rare and short-lasting although accompanied by intense precipitation KLIMAT STREFY PODZWROTNIKOWEJ Klimatologia regionalna 9 Mediterranean climate; air temperature (T) • summer: – Long and warm with T 21-27°C over at least 2 months • In oceanic type T is lower: 16-21°C – Annual Tmax frequently above 38-40°C (*) – High daily T range around 20°C between daytime and night (*) • winter: – T of the coolest month usually >5 °C • No wintertime break in vegetation – Diurnal T range: 8-11 °C – Rare frost events (not every year usually) but Tmin_abs <0 °C – Frost very unlikely on islands (*) except of oceanic coasts with cold current e.g. Chile KLIMAT STREFY PODZWROTNIKOWEJ Klimatologia regionalna 10 Mediterranean climate; Precipitation (R) • Around 65-75% of precipitation in cool half of the year • Annual total R usually 380-900 mm with significant variability of temporal and spatial distribution • Very weak summer precipitation (even nil) • Snow is a rare phenomenon near sea level – in the surrounding mountains snow cover reaching 100-200 cm thick can last even for the whole winter KLIMAT STREFY PODZWROTNIKOWEJ Klimatologia regionalna 10 Mediterranean climate; Precipitation (R) • Around 65-75% of precipitation in cool half of the year • Annual total R usually 380-900 mm with significant variability of temporal and spatial distribution • Very weak summer precipitation (even nil) • Snow is a rare phenomenon near sea level – in the surrounding mountains snow cover reaching 100-200 cm thick can last even for the whole winter KLIMAT STREFY PODZWROTNIKOWEJ Klimatologia regionalna 12 Mediterranean climate - vegetation • High seasonal variability of landscape • Gradual summertime evolution towards arid zone conditions – High dust concentration in late summer – Even drought-induced vegetation break possible • Autumn vegetation revival • Springtime vegetation climax • Predominance of bushy tree-like plants » makia (M.S. bassin) » chaparral (SW USA) » mallee (Australia) » fynbos (S Africa) • Frequent groups of trees (or single specimens) separated by grassy and bushy vegetation
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STREFY PODZWROTNIKOWEJ śródziemnomorski klimat |