Humid subtropical climate
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The humid subtropical climate (Köppen Cfa) is a climate zone characterized by hot, humid summers and chilly to mild winters. This climate type covers a broad category of climates, and the term "subtropical" may be a misnomer for the winter climate in the cooler areas within this category. Significant amounts of precipitation occur in all seasons in most areas. Winter rainfall (and sometimes snowfall) is associated with large storms that the westerlies steer from west to east. Most summer rainfall occurs during thunderstorms and an occasional tropical storm or hurricane.
Humid subtropical climates lie on the southeast side of all continents except Antarctica, roughly between latitudes 25° and 40° north and south. The only exceptions where this climate zone reaches up to latitude 46° North, are the Po Valley and the Toulouse regions in Europe. The Köppen definition of this climate is for the coldest month to be above 0 °C mean (Köppen: C), and the warmest month to be above 22 °C (Köppen: a); and to be constantly moist with the driest month to get more than 60 mm rain (Köppen: f).[1]
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[edit] Africa
In Africa, this climate type is found only on the east coast of South Africa including Durban and extends northward into extreme southern Mozambique.
[edit] Asia
Humid subtropical climates in Asia differ from those in other continents in generally having a very pronounced dry winter even on the poleward boundary of this region. They occupy extensive arcs of relatively low land from northern Pakistan circling the Himalayas to China, Southern Coast of South Korea and Japan (South of Tokyo). Some major Asian cities in this climate zone include Islamabad, Kathmandu, Chongqing, Chengdu, Shanghai, Nanjing, Busan, Kyoto and Tokyo. Hong Kong and Taipei are on the equatorward boundary of this zone.
In most of this region, there is very little precipiation during the winter owing to the powerful anticyclonic winds from Siberia. Only in those parts of coast eastern China between about the Yellow River and the Pearl River is there sufficient winter rainfall to produce a Cfa climate and even in these areas rainfall and streamflow show a very pronounced summer peak quite unlike other regions of this climate type. The only area where the winter rainfall equals the summer rain is on the "San-in" (Sea of Japan) coast of Japan, which during winter is effectively on the windward side of the westerlies. The winter rainfall in these regions is usually produced by low pressure systems off the east coast that develop in the onshore flow from the Siberian High. Summer rainfall comes from the East Asian Monsoon and from frequent typhoons.
Annual rainfall is generally over 1,000 mm (40 inches), and in areas below the Himalayas can be much higher still. In the west humid subtropical climate border on continental climates as altitude increases, or on winter-rainfall climates in Pakistan.
[edit] Isolated humid zones in western Asia
Although humid climates in Asia are mostly confined to the southeastern quarter of the continent, there are some isolated areas on the Black and Caspian Seas than possess humid climates that are unusually warm for their high latitudes.
In the narrow Caspian coastal strip of Iran (Gilan and Mazandaran) a humid subtropical climate prevails at an unusually high latitude. Annual rainfall ranges from around 740 mm (29 inches) at Sari to over 2,000 mm (78 inches) at Bandar-e Anzali, and is heavy throughout the year, with a maximum in October or November when Bandar-e Anzali can average 400 millimetres (16 inches). Tempteratures are generally moderate in comparison with other parts of western Asia. In Rasht, the average maximum in July is around 28 °C (82 °F) but with near-saturation humidity, whilst in January it is around 9 °C (48 °F).
In Georgia and the adjacent region of Turkey, the Kolkheti Lowland has a climate similar to that of Gilan in Iran. Temperatures range from 22 °C in summer to 5 °C in winter and rainfall is even heavier than in Caspian Iran, up to 2,300 millimetres per year in Hopa, and it falls throughout the year. This climate is almost a Cfa/Cfb borderline case, however.
[edit] Australia
The humid subtropical climate dominates most of eastern Australia south from about Bundaberg, Queensland down to about Bega on the south coast of New South Wales. It extends from the coast inland to about Dubbo and the Warrumbungle and Nandewar mountain ranges, where it grades into arid climates. In the Great Dividing Range and to the south of about Bega, this climate type grades into warm temperate climates (Köppen Cfb) as at Guyra and Katoomba, in New South Wales.
This zone contains the only regions where soils are not acutely deficient in phosphorus, as well as the heaviest rainfall south of the Tropic of Capricorn, making it prime agricultural country, centred on towns such as Coffs Harbour, Grafton, Port Macquarie, Tamworth, and Moree.
Many of Australia's major cities are also in this climate zone, including Sydney, Brisbane, Gold Coast-Tweed Heads, Newcastle and Wollongong.
[edit] Variations in Australia
There is considerable variation in climate within this zone. Annual rainfall on the coast can reach as high as 2,000 mm (80 inches) in favourable locations and is generally above 1,000 mm (40 inches). However, because most of the heaviest two- and three-day rainfalls in the world occur in this coastal zone as a result of east coast cyclones forming to the north of a large high pressure system, there can be great variation in rainfall from year to year. At Lismore in the centre of this zone, the annual rainfall can range from less than 550 mm (22 inches) in 1915 to more than 2,780 mm (110 inches) in 1950. There is usually a distinct summer rainfall maximum that becomes more pronounced moving northwards: in Brisbane the wettest month (February) receives five times the rainfall of the driest (September).
Temperatures in this zone are typically very warm but not excessive: the average maximum in January is usually around 28 °C (82 °F) and in July around 19 °C (66 °F). Frosts are extremely rare except at higher elevations.
In the Darling Downs and further south, the summer rainfall maximum is less marked and by the time one reaches Dubbo, there are actually on average more rainy days in the winter months. Temperatures here are more extreme, with summers being generally very hot with maxima of around 32 °C (88 °F) and frosts being common during dry winters: at Mitchell the temperature has reached as low as -9.4 °C (15 °F).
North of the Cfa climate zone there is a zone centred upon Rockhampton and extending up to the Atherton Tableland of Köppen Cwa climate. This has a very pronounced dry winter with often negligible rainfall between June and October, and winter temperatures generally only slightly below 14.4°C, above which one would have a tropical savanna, or Aw, climate.
[edit] Europe
In some areas of Europe, such as parts of France, northern Italy, Croatia, Hungary, and some southern Swiss lowlands that have summers too warm (21°C in at least one month) to qualify as oceanic, no freezing month, and adequate summer precipitation to preclude classification as Mediterranean one finds a transition zone between oceanic climates (Cfb) characteristic of England and either Mediterranean climates (Csa) of southern Italy or hot hot-summer continental climates (Dfa) characteristic of the inland areas of the Balkans (example: Bucharest, Romania). This is a narrow band of climate, but it includes some densely-populated territory.
[edit] North America
In North America, humid subtropical climates are almost exclusively the domain of the American South, including the eastern half of Texas, Louisiana, most of Arkansas, Mississippi, Tennessee, Kentucky, Alabama, North Carolina, South Carolina, Georgia, most of Florida and Virginia, except for upland regions including Southwest Virginia. It also exists in low lying or urban areas, in some cases extending just south of 40N in Delaware, southwestern West Virginia, eastern and southern Maryland, southeastern Pennsylvania (Philadelphia metropolitan area), southern New Jersey, southern Missouri, and extreme southern Ohio.
Major cities in this climate zone include Houston, San Antonio, Austin, Dallas, Atlanta, Memphis, New Orleans, Birmingham, Louisville, Nashville,Chattanooga, Greenville (SC), Charlotte, Raleigh, Jackson (MS),Jacksonville, Orlando, Tampa, Richmond, and Little Rock. Cities on the northern periphery of this zone include Tulsa, St. Louis, Cincinnati[citation needed], Washington (DC), Baltimore, Philadelphia (northernmost metropolitan area), Wilmington (DE), and Atlantic City. Dallas and Oklahoma City show marked reduction in rainfall that suggests a shading into steppe climates to be found farther west, as in Lubbock, Texas. Some of these cities, such as Tampa, New Orleans and Atlanta, are of a warmer variety; and others, such as Washington, and Cincinnati, are of a colder variety with occasional significant winter snowfalls.
[edit] Characteristics and variants
The southernmost limits of this climate are around Miami and southern coastal Texas, and areas further south have a true tropical climate with a very warm weather year round and minimal temperature differences between seasons. The northernmost limits of the humid subtropical climate are around Philadelphia and adjacent southern New Jersey or around 40°N, southwest to Washington, D.C. and the edge of the Blue Ridge west to Louisville, Kentucky then roughly along the Ohio River through Paducah, Kentucky to south of Springfield, Missouri. Areas further north, inland, or higher in elevation which have a humid continental climate with colder winters.
Snowfall varies greatly in this climate zone. In areas around Florida and the Gulf Coast, snowfall is very rare and it occurs a few times per generation. In southern cities farther north, such as Atlanta, Little Rock, Nashville, Dallas, Greenville, Charlotte, Raleigh, and Norfolk, snowfall is sporadic, but occasional light snow and ice storms are not unusual. Into the northern limits of this climate zone, in cities like Baltimore, Cincinnati and Philadelphia, snow is more common and it occurs every year, sometimes accumulating heavily.
Precipitation is plentiful in the humid subtropical climate zone. Although most areas tend to have precipitation spread evenly throughout the year, a somewhat monsoon-like pattern is seen in parts of the Southeast (in locales such as Augusta, Georgia and Columbia, South Carolina), which experience an extremely dry (by humid subtropical standards) and warm spring, followed immediately by a long, hot, rainy and humid summer. In addition, areas in Texas that are slightly inland from the Gulf of Mexico, such as Austin, generally see a peak of precipitation in the spring, and a deep, drought-like nadir in mid-summer.
[edit] South America
In South America, this kind of climate can be found mainly at the southern Atlantic Coast. In Southern Brazil (south of the highlands of the Rio de Janeiro and São Paulo states, where the coastal area is tropical), the South of Paraguay, the North of Uruguay and the North-East of Argentina (Eastern Chaco, Mesopotamia and the Northern and Central Pampas) temperatures are within the range of this climate and there is rainfall the year round. South-east of a line between Buenos Aires and Bahía Blanca summer temperatures are too low, and west of a line between Bahía Blanca, Rosario and the cities on the Paraná river there is a dry period in winter. The region covers three vegetation zones: the subtropical rain forest in Misiones Province and parts of Southern Brazil, where rainfall and winter temperatures are high (1500 mm and above, more than 16°C in winter) but summer temperatures lie below 26°; the eastern Chaco and the swamplands of the Argentine Corrientes Province with fewer rainfall (800 to 1500 mm) and higher summer temperatures above 26°C, and the generally cooler Humid Pampas area with warm summers of 22° to 25°C and cool winters of 8° to 12°C which receive great influence by the Oceanic regions of the Atlantic Coast of the region around Mar del Plata.
Summer temperatures in some valleys of southern Central Chile (the Temuco/Concepción area) are about 22° but in the greatest part of this region they are below this mark. Another small area with a similar climate are parts of the northern Yungas in Bolivia and Peru.
[edit] References
- ^ The Times Atlas of the World (1993). Times Books ISBN 0-7230-0492-7.
Climate types under the Köppen climate classification | |
|---|---|
| Class A | Equatorial (Af) · Monsoon (Am) · Savanna (Aw, As) |
| Class B | Desert (BWh, BWk) · Semi-arid (BSh, BSk) |
| Class C | Humid subtropical (Cfa, Cwa) · Oceanic (Cfb, Cwb, Cfc) · Mediterranean (Csa, Csb) |
| Class D | Humid continental (Dfa, Dwa, Dfb, Dwb) · Subarctic (Dfc, Dwc, Dfd, Dwd) · Continental (Dsa, Dsb) . Other continental (Dsc, Dsd) |
| Class E | Polar (ET, EF) · Alpine (ETH) |
he:אקלים סובטרופי גשום ja:温暖湿潤気候 no:Fuktig subtropisk klima nn:Fuktig subtropisk klima ru:Гумидный климат
