Everything about Humid Subtropical Climate totally explained
Humid Subtropical climate (
Köppen Cfa or
Cwa) 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,
hurricane or cyclone.
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 -3 °
C mean (Köppen: C), and the warmest month to be above 22 °C (Köppen: a); and either a dry winter with less than one tenth of the precipitation of the wettest summer month (Köppen: w) or without dry season (Köppen: f, winter months get more than one tenth of the precipitation of the wettest summer month and summer months get at least 40mm per month or more than one third as much the wettest winter month).
Africa
In Africa, this climate type is found only on the east coast of
South Africa including
Durban and extends almost northward into extreme southern
Mozambique.
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 (most part of
Honshu,
Kyūshū and
Shikoku). Some major Asian cities in this climate zone include
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's 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.
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's 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.
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.
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 (Septet text]]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 (90 °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's 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.
Europe
In some areas of Europe, such as parts of southern France, northern Italy (Po River Valley), coastal Croatia, have summers too warm (>21°C in the warmest month) to qualify as oceanic, no freezing month, and adequate summer precipitation to preclude their classification as
Mediterranean. This is a narrow band of climate that could be classified as humid sub-tropical, which includes some densely-populated territory.
North America
In
North America, humid subtropical climates are almost exclusively the domain of the
American South, the eastern half of
Texas (includes South Texas),
Louisiana, most of
Arkansas,
Mississippi,
Tennessee,
Kentucky,
Alabama,
North Carolina,
South Carolina,
Georgia, most of
Florida and
Virginia, excluding upland regions of the Appalachians. It also exists in low lying or urban areas including
Delaware, southwestern
West Virginia, eastern and southern
Maryland, southeastern
Pennsylvania (Philadelphia metropolitan area only), most of
New Jersey, Up the east coast of
New England, southern
Missouri, and extreme southern
Ohio. The most classic example of a humid subtropical climate is the deep south, because the summers are long and almost tropical, and it only reaches freezing a few times in the winter with rare snowfall. Summer conditions in this zone are hot and humid, with daily averages ranging between 25°C (77°F) and 30°C (86°F).
Major cities in this climate zone include
Houston,
San Antonio,
Austin,
Dallas,
Atlanta,
Memphis,
New Orleans, Louisiana,
Lafayette, Louisiana Birmingham,
Louisville,
Nashville,
Chattanooga,
Greenville (
SC),
Charlotte,
Raleigh,
Jackson (
MS),
Jacksonville,
Orlando,
Tampa,
Richmond,
Charleston (
WV)
(External Link
) and
Little Rock. Cities on the northern periphery of this zone include
Tulsa,
St. Louis,
Cincinnati,
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.
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. By contrast, the northernmost limits of the humid subtropical experience much greater seasonal variation. The humid subtropical climat extends north of Boston. They draw influence from the Atlantic Ocean and its bays,
Delaware Bay and
Chesapeake Bay including
Washington, D.C.. Further away from the Atlantic, it's found at the edge of the
Blue Ridge west to
Louisville, Kentucky then roughly along the lower
Ohio River through
Paducah, Kentucky to a line south of
Springfield, Missouri, that doesn't include the city itself. Areas further north than this, inland, or at a higher elevation fall into the
humid continental climate category with harsher winters.
Snowfall varies greatly in this climate zone. In areas around Florida and the
Gulf Coast, snowfall is very rare and it occurs a most a few times per generation. In inland 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, however most of the winter temperatures remain above or well above freezing with hardy sub-tropical plant growth. However in the northern limits of this climate zone, in cities like
Louisville,
Cincinnati and
Philadelphia, snow is more common and it occurs every winter, sometimes accumulating heavily although it melts quicker than in regions to the north.
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 dry winters (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.
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's 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's 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're below this mark. Another small area with a similar climate are parts of the northern
Yungas in
Bolivia and
Peru.
Further Information
Get more info on 'Humid Subtropical Climate'.
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