A humid continental climate is a climatic region defined by Russo-German climatologistWladimir Köppen in 1900,[1] typified by four distinct seasons and large seasonal temperature differences, with warm to hot (and often humid) summers and cold (sometimes severely cold in the northern areas) winters. Precipitation is usually distributed throughout the year but often does have dry seasons. The definition of this climate regarding temperature is as follows: the mean temperature of the coldest month must be below 0 °C (32.0 °F) or −3 °C (26.6 °F) depending on the isotherm, [2] and there must be at least four months whose mean temperatures are at or above 10 °C (50 °F). In addition, the location in question must not be semi-arid or arid. The cooler Dfb, Dwb, and Dsb subtypes are also known as hemiboreal climates.
Humid continental climates are generally found between latitudes 40° N and 60° N,[3] within the central and northeastern portions of North America, Europe, and Asia. They are rare and isolated in the Southern Hemisphere, due to the larger ocean area at that latitude, smaller land mass, and the consequent greater maritime moderation. In the Northern Hemisphere, some of the humid continental climates, typically in Hokkaido, Northern Honshu, Sakhalin island, northeastern mainland Europe, Scandinavia, Nova Scotia, and Newfoundland are closer to the sea and heavily maritime-influenced and comparable to oceanic climates, with relatively cool summers and winters being just below the freezing mark (too cold for such a classification).[4] More extreme and inland humid continental climates are found in northeast China, southern Siberia, the Korean Peninsula (except for the southeastern and southwestern region in Korea), and the Canadian Prairies, where temperatures in the winter resemble those of subarctic climates but have warmer and longer summers. In east-central China, central Korea, the Great Lakes region of the American Midwest, New England, and southern parts of Central Canada the climate combines hotter summer maxima and colder winters than the marine-based variety and is less extreme than the most inland variety, with similarities to the adjacent humid subtropical climate but with colder winters which preclude such classifications.[5]
Definition
The snowy city of Sapporo, Japan, has a humid continental climate (KöppenDfa).
Using the Köppen climate classification, a climate is classified as humid continental when the temperature of the coldest month is below 0 °C [32.0 °F] or −3 °C [26.6 °F] and there must be at least four months whose mean temperatures are at or above 10 °C (50 °F).[6] These temperatures were not arbitrary. In Europe, the −3 °C (27 °F) average temperature isotherm (line of equal temperature) was near the southern extent of winter snowpack. In the United States, it is more common to use the 0 °C [32.0 °F] isotherm instead. The 10 °C (50 °F) average temperature was found to be roughly the minimum temperature necessary for tree reproduction and growth.[7] Wide temperature ranges are common within this climate zone.[8]
Second letter in the classification symbol defines seasonal rainfall as follows: [6]
s: A dry summer—the driest month in the high-sun half of the year (April to September in the Northern Hemisphere, October to March in the Southern Hemisphere) has less than 30 millimetres (1.18 in)/40 millimetres (1.57 in) of rainfall and has exactly or less than 1⁄3 the precipitation of the wettest month in the low-sun half of the year (October to March in the Northern Hemisphere, April to September in the Southern Hemisphere).
w: A dry winter—the driest month in the low-sun half of the year has exactly or less than one‑tenth of the precipitation found in the wettest month in the summer half of the year.
f: No dry season—does not meet either of the alternative specifications above; precipitation and humidity are often high year-round.
while the third letter denotes the extent of summer heat:[6]
a: Hot summer, warmest month averages at least 22 °C (71.6 °F),
b: Warm summer, warmest month averages below 22 °C (71.6 °F) but at least four months averages above 10 °C (50.0 °F).
Associated precipitation
Within North America, moisture within this climate regime is supplied by the Great Lakes, Gulf of Mexico and adjacent western subtropical Atlantic.[9]Precipitation is relatively well distributed year-round in many areas with this climate (f), while others may see a marked reduction in wintry precipitation,[7] which increases the chances of a wintertime drought (w).[10]Snowfall occurs in all areas with a humid continental climate and in many such places is more common than rain during the height of winter. In places with sufficient wintertime precipitation, the snow cover is often deep. Most summer rainfall occurs during thunderstorms,[7] and in North America and Asia an occasional tropical system. Though humidity levels are often high in locations with humid continental climates, the "humid" designation means that the climate is not dry enough to be classified as semi-arid or arid.
By definition, forests thrive within this climate. Biomes within this climate regime include temperate woodlands, temperate grasslands, temperate deciduous or evergreen forests,[9] coniferous forests, and coniferous swamps.[11] Within wetter areas, maple, spruce, pine, fir, and oak can be found. Fall foliage is noted during the autumn of deciduous forests.[7]
Hot summer subtype
Regions with hot-summer humid continental climates
A hot summer version of a continental climate features an average temperature of at least 22 °C (71.6 °F) in its warmest month.[14] Since these regimes are limited to the Northern Hemisphere, the warmest month is usually July or August. High temperatures in the warmest month tend to be in the high 20s or low 30s °C (80s or low 90s °F), while average January afternoon temperatures are near or well below freezing. Frost free periods normally last 4–7 months within this climate regime.[7]
In the Eastern Hemisphere, this climate regime is found within interior Eurasia, east-central Asia, and parts of India. Within Europe, the Dfa climate type is present near the Black Sea in southern Ukraine, the Southern Federal District of Russia, southern Moldova, Serbia, parts of southern Romania, and Bulgaria,[15][16] but tends to be drier and can be even semi-arid in these places. In East Asia, this climate exhibits a monsoonal tendency with much higher precipitation in summer than in winter, and due to the effects of the strong Siberian High much colder winter temperatures than similar latitudes around the world, however with lower snowfall, the exception being western Japan with its heavy snowfall. Tōhoku, between Tokyo and Hokkaidō and Western coast of Japan also has a climate with Köppen classification Dfa, but is wetter even than that part of North America with this climate type. A variant which has dry winters and hence relatively lower snowfall with monsoonal type summer rainfall is to be found in northern China including Manchuria and parts of North China, and over much of the Korean Peninsula; it has the Köppen classification Dwa. Much of central Asia, northwestern China, and southern Mongolia has a thermal regime similar to that of the Dfa climate type, but these regions receive so little precipitation that they are more often classified as steppes (BSk) or deserts (BWk).
Dsa climates are rare; they are generally restricted to elevated areas adjacent to Mediterranean climate regions with a Csa climate well inland to ensure hot summers and cold winters. They are generally found in the highly elevated areas of south-eastern Turkey (Hakkâri), north-western Iran and parts of Central Asia.
This climate zone does not exist at all in the southern hemisphere, where the only landmass that enters the upper-middle latitudes, South America, tapers too much to have any place that gets the combination of snowy winters and hot summers. Marine influences preclude Dfa, Dwa, and Dsa climates in the southern hemisphere.
Warm summer subtype
Regions with warm-summer humid continental climates
Also known as Hemiboreal climate, areas featuring this subtype of the continental climate have an average temperature in the warmest month below 22 °C (72 °F). Summer high temperatures in this zone typically average between 21–28 °C (70–82 °F) during the daytime and the average temperatures in the coldest month are generally well or far below the −3 °C (27 °F) (or 0 °C (32.0 °F)) isotherm. Frost-free periods typically last 3–5 months. Heat spells lasting over a week are rare.[7]
The warm summer version of the humid continental climate covers a much larger area than the hot subtype. In North America, the climate zone covers from about 42°N to 50°N latitude mostly east of 100°W, including parts of Southern Ontario, the southern half of Quebec, The Maritimes, and Newfoundland, as well as the northern United States from eastern North Dakota east to Maine. However, it can be found as far north as 54°N, and further west in the Canadian Prairie Provinces[citation needed] and below 40°N in the high Appalachians. In Europe, this subtype reaches its most northerly latitude in Bodø at the 67°N.[21]
High-altitude locations such as Aspen, Colorado and Los Alamos, New Mexico in the western United States exhibit local Dfb climates. The south-central and southwestern Prairie Provinces also fits the Dfb criteria from a thermal profile, but because of semi-arid precipitation portions of it are grouped into the BSk category. [citation needed]
Since climate regimes tend to be dominated by vegetation of one region with relatively homogenous ecology, those that project climate change remap their results in the form of climate regimes as an alternative way to explain expected changes.[1]
