![July diurnalvariation US](https://upload.wikimedia.org/wikipedia/commons/a/ad/July_diurnalvariation_US.svg)
In
meteorology
Meteorology is a branch of the atmospheric sciences (which include atmospheric chemistry and physics) with a major focus on weather forecasting. The study of meteorology dates back millennia, though significant progress in meteorology did no ...
, diurnal temperature variation is the variation between a high
air temperature
Atmospheric temperature is a measure of temperature at different levels of the Earth's atmosphere. It is governed by many factors, including incoming solar radiation, humidity and altitude. When discussing surface air temperature, the annual atm ...
and a low temperature that occurs during the same
day.
Temperature lag
Temperature lag is an important factor in diurnal temperature variation: peak daily temperature generally occurs ''after'' noon, as air keeps net absorbing heat even after noon, and similarly minimum daily temperature generally occurs substantially after midnight, indeed occurring during early morning in the hour around dawn, since heat is lost all night long. The analogous annual phenomenon is
seasonal lag
Seasonal lag is the phenomenon whereby the date of maximum average air temperature at a geographical location on a planet is delayed until some time after the date of maximum insolation (i.e. the summer solstice). This also applies to the minim ...
.
As solar energy strikes the Earth's surface each morning, a shallow layer of air directly above the ground is heated by conduction. Heat exchange between this shallow layer of warm air and the cooler air above is very inefficient. On a warm summer's day, for example, air temperatures may vary by from just above the ground to waist height. Incoming solar radiation exceeds outgoing heat energy for many hours after noon and equilibrium is usually reached from 3–5 p.m. but this may be affected by a variety of different things such as large bodies of water, soil type and cover, wind, cloud cover/water vapor, and moisture on the ground.
[M. Hackworth "Weather & Climate" course notes, with prior permission](_blank)
Differences in variation
Diurnal temperature variations are greatest very near Earth's surface. The
Tibetan
Tibetan may mean:
* of, from, or related to Tibet
* Tibetan people, an ethnic group
* Tibetan language:
** Classical Tibetan, the classical language used also as a contemporary written standard
** Standard Tibetan, the most widely used spoken dial ...
and
Andean Plateaus present one of the largest differences in daily temperature on the planet.
High desert regions typically have the greatest diurnal-temperature variations, while low-lying humid areas typically have the least. This explains why an area like the
Snake River Plain can have high temperatures of during a summer day, and then have lows of . At the same time,
Washington D.C.
)
, image_skyline =
, image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, Na ...
, which is much more humid, has temperature variations of only ;
urban
Hong Kong
Hong Kong ( (US) or (UK); , ), officially the Hong Kong Special Administrative Region of the People's Republic of China (abbr. Hong Kong SAR or HKSAR), is a city and special administrative region of China on the eastern Pearl River Delta i ...
has a diurnal temperature range of little more than .
While the
National Park Service
The National Park Service (NPS) is an agency of the United States federal government within the U.S. Department of the Interior that manages all national parks, most national monuments, and other natural, historical, and recreational propert ...
claimed that the world single-day record is a variation of (from to ) in
Browning, Montana
Browning is a town in Glacier County, Montana, United States. It is the headquarters for the Blackfeet Indian Reservation and the only incorporated town on the Reservation. The population was 1,018 at the 2020 census.
The town was named in 188 ...
in 1916, the Montana Department of Environmental Quality claimed that
Loma, Montana
Loma is a census-designated place (CDP) in Chouteau County, Montana, United States. The population was 85 at the 2010 census.
History
James Kipp, of the American Fur Company founded the first community here in 1831. The Blackfeet laid siege to ...
also had a variation of (from to ) in 1972.
Montana Department of Environmental Quality (DEQ) - FAQ
Both these extreme daily temperature changes were the result of sharp air-mass changes within a single day. The 1916 event was an extreme temperature drop, resulting from frigid Arctic air from Canada invading northern Montana, displacing a much warmer air mass. The 1972 event was a chinook event, where air from the Pacific Ocean overtopped mountain ranges to the west, and dramatically warmed in its descent into Montana, displacing frigid Arctic air and causing a drastic temperature rise.
In the absence of such extreme air-mass changes, diurnal temperature variations typically range from 10 or fewer degrees in humid, tropical areas, to 40-50 degrees in higher-elevation, arid to semi-arid areas, such as parts of the U.S. Western states' Intermountain Plateau areas, for example Elko, Nevada, Ashton, Idaho
Ashton is a city in Fremont County, Idaho, United States. The population was 1,127 at the 2010 census, and it is part of the Rexburg Micropolitan Statistical Area. The district is noted for seed potato production and bills itself as the world's ...
and Burns, Oregon. The higher the humidity
Humidity is the concentration of water vapor present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present.
Humidity dep ...
is, the lower the diurnal temperature variation is.
In Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a subcontinent of Eurasia and it is located entirel ...
, due to its more northern latitude and close proximity to large warm water bodies (such as the Mediterranean
The Mediterranean Sea is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean Basin and almost completely enclosed by land: on the north by Western Europe, Western and Southern Europe and Anatolia, on the south by North Africa ...
), differences in daily temperature are not as pronounced as in other continents. However, places in Southern Europe
Southern Europe is the southern region of Europe. It is also known as Mediterranean Europe, as its geography is essentially marked by the Mediterranean Sea. Definitions of Southern Europe include some or all of these countries and regions: Alba ...
significantly far from the Mediterranean tend to have high differences in daily temperatures, some around . These include Southwestern Iberia
The Iberian Peninsula (),
**
* Aragonese and Occitan: ''Peninsula Iberica''
**
**
* french: Péninsule Ibérique
* mwl, Península Eibérica
* eu, Iberiar penintsula also known as Iberia, is a peninsula in southwestern Europe, defi ...
(e.g. Alvega
Alvega is a former ''freguesia'' ("civil parish"), located in the municipality of Abrantes, in Santarém District, Portugal. In 2013, the parish merged into the new parish Alvega e Concavada. The population in 2011 was 1,499, in an area of 55.33&n ...
or Badajoz
Badajoz (; formerly written ''Badajos'' in English) is the capital of the Province of Badajoz in the autonomous community of Extremadura, Spain. It is situated close to the Portuguese border, on the left bank of the river Guadiana. The populatio ...
) or the high-altitude plateaus of Turkey (if part of Europe) (e.g. Kayseri).
Viticulture
Diurnal temperature variation is of particular importance in viticulture
Viticulture (from the Latin word for '' vine'') or winegrowing (wine growing) is the cultivation and harvesting of grapes. It is a branch of the science of horticulture. While the native territory of '' Vitis vinifera'', the common grape vine, ...
. Wine regions
This list of wine-producing regions catalogues significant growing regions where vineyards are planted. Wine grapes mostly grow between the 30th and the 50th degree of latitude, in both the Northern and Southern hemispheres. Grapes will sometimes ...
situated in areas of high altitude
Altitude or height (also sometimes known as depth) is a distance measurement, usually in the vertical or "up" direction, between a reference datum and a point or object. The exact definition and reference datum varies according to the context ...
experience the most dramatic swing in temperature variation during the course of a day. In grape
A grape is a fruit, botanically a berry, of the deciduous woody vines of the flowering plant genus '' Vitis''. Grapes are a non- climacteric type of fruit, generally occurring in clusters.
The cultivation of grapes began perhaps 8,000 years a ...
s, this variation has the effect of producing high acid and high sugar content as the grapes' exposure to sunlight increases the ripening qualities while the sudden drop in temperature at night preserves the balance of natural acids in the grape.[J. Robinson ''"The Oxford Companion to Wine"'' Third Edition pg 691 Oxford University Press 2006 ]
See also
*Diurnal cycle
A diurnal cycle (or diel cycle) is any pattern that recurs every 24 hours as a result of one full rotation of the planet Earth around its axis. Earth's rotation causes surface temperature fluctuations throughout the day and night, as well as we ...
References
{{Climate oscillations
Meteorological phenomena
Daily events
Atmospheric temperature
fr:Amplitude thermique#Types