# Microclimate

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A microclimate is a local set of atmospheric conditions that differ from those in the surrounding areas, often with a slight difference but sometimes with a substantial one. The term may refer to areas as small as a few square meters or square feet (for example a garden bed or a cave) or as large as many square kilometers or square miles. Because climate is statistical, which implies spatial and temporal variation of the mean values of the describing parameters, within a region there can occur and persist over time sets of statistically distinct conditions, that is, microclimates. Microclimates can be found in most places.

## Contents

Microclimates exist, for example, near bodies of water which may cool the local atmosphere, or in heavy urban areas where brick, concrete, and asphalt absorb the sun's energy, heat up, and re-radiate that heat to the ambient air: the resulting urban heat island is a kind of microclimate. [1]

Another contributing factor of microclimate is the slope or aspect of an area. South-facing slopes in the Northern Hemisphere and north-facing slopes in the Southern Hemisphere are exposed to more direct sunlight than opposite slopes and are therefore warmer for longer periods of time, giving the slope a warmer microclimate than the areas around the slope. The lowest area of a glen may sometimes frost sooner or harder than a nearby spot uphill, because cold air sinks, a drying breeze may not reach the lowest bottom, and humidity lingers and precipitates, then freezes.

## Background

The terminology "micro-climate" first appeared in the 1950s in publications such as Climates in Miniature: A Study of Micro-Climate Environment (Thomas Bedford Franklin, 1955). [2]

The area in a developed industrial park may vary greatly from a wooded park nearby, as natural flora in parks absorb light and heat in leaves that a building roof or parking lot just radiates back into the air. Advocates of solar energy argue that widespread use of solar collection can mitigate overheating of urban environments by absorbing sunlight and putting it to work instead of heating the foreign surface objects. [3]

A microclimate can offer an opportunity as a small growing region for crops that cannot thrive in the broader area; this concept is often used in permaculture practiced in northern temperate climates. Microclimates can be used to the advantage of gardeners who carefully choose and position their plants. Cities often raise the average temperature by zoning, and a sheltered position can reduce the severity of winter. Roof gardening, however, exposes plants to more extreme temperatures in both summer and winter.

In an urban area, tall buildings create their own microclimate, both by overshadowing large areas and by channeling strong winds to ground level. Wind effects around tall buildings are assessed as part of a microclimate study. (Urban Microclimate)

Microclimates can also refer to purpose-made environments, such as those in a room or other enclosure. Microclimates are commonly created and carefully maintained in museum display and storage environments. This can be done using passive methods, such as silica gel, or with active microclimate control devices.

Usually, if the inland areas have a humid continental climate, the coastal areas stay much milder during winter months, in contrast to the hotter summers. This is the case further north on the American west coast, such as in British Columbia, Canada, where Vancouver has an oceanic wet winter with rare frosts, but inland areas that average several degrees warmer in summer have cold and snowy winters.

### Soil types

The type of soil found in an area can also affect microclimates. For example, soils heavy in clay can act like pavement, moderating the near ground temperature. On the other hand, if soil has many air pockets, then the heat could be trapped underneath the topsoil, resulting in the increased possibility of frost at ground level. [4]

## Sources and influences on microclimate

Two main parameters to define a microclimate within a certain area are temperature and humidity. A source of a drop in temperature and/or humidity can be attributed to different sources or influences. Often microclimate is shaped by a conglomerate of different influences and is a subject of microscale meteorology.

### Cold air pool

The well known examples of cold air pool (CAP) effect are Gstettneralm Sinkhole in Austria (lowest recorded temperature −53 °C (−63 °F)) [5] and Peter Sinks in the US. The main criterion on the wind speed ${\displaystyle v}$ in order to create a warm air flow penetration into a CAP is the following:

${\displaystyle \mathrm {Fr} ={\frac {v}{Nh}}\geq \mathrm {Fr} _{c},}$

where ${\displaystyle \mathrm {Fr} }$ is the Froude number, ${\displaystyle N}$ — the Brunt–Väisälä frequency, ${\displaystyle h}$ — depth of the valley, and ${\displaystyle \mathrm {Fr} _{c}}$ — Froude number at the threshold wind speed. [6]

### Craters

The presence of permafrost close to the surface in a crater creates a unique microclimate environment. [7]

### Caves and lava tubes

As similar as lava tubes can be to caves which are not formed due to volcanic activity the microclimate within the former is different due to dominant presence of basalt. Lava tubes and basaltic caves are important astrobiological targets on Earth and Mars (see also Martian lava tube).

### Plant microclimate

As pointed out by Rudolf Geiger in his book [8] not only climate influences the living plant but the opposite effect of the interaction of plants on their environment can also take place, and is known as plant climate. This effect has important consequences for forests in the midst of a continent; indeed, if forests were not creating their own clouds and water cycle with their efficient evapo-transpiration activity, there would be no forest far away from coasts [9] , as statistically, without any other influence, rainfall occurrence would decrease from the coast towards innland. Planting trees to fight drought has also been proposed in the context of afforestation [10] .

### Dams

Artificial reservoirs as well as natural ones create microclimates and often influence the macroscopic climate as well.

## Cities and regions known for microclimates

### Americas

• Northern California above the Bay Area is also well known for microclimates with significant differences of temperatures.[ citation needed ] The coastline typically averages between 17 and 19 °C (63 and 66 °F) during summer months along that coastline, but inland towns not far from the ocean such as Lakeport, average as much as 34 °C (93 °F) in spite of being just around 40 miles (64 km) inland. Even as far north as the Klamath River valley around the 41st parallel north between Willow Creek and Eureka averages such temperatures, which is extremely hot for such northerly areas. At this parallel, the temperature at the coast is so cool that Willow Creek beats Eureka's all-time record temperature on average 79 times per year. This is in spite of the areas being less than 50 miles from each other. In oceanic stable terms it is like traveling from the summers in the north of England to the south of Spain in a fraction of the distance.
• San Francisco is a city with microclimates and submicroclimates.[ citation needed ] Due to the city's varied topography and influence from the prevailing summer marine layer, weather conditions can vary by as much as 9 °F (5 °C) from block to block. The Noe Valley district for example, is typically warmer and sunnier than adjacent areas because the surrounding hills block some of the cool fog from the Pacific.
• The region as a whole, known as the San Francisco Bay area can have a wide range of extremes in temperature. In the basins and valleys adjoining the coast, climate is subject to wide variations within short distances as a result of the influence of topography on the circulation of marine air. The San Francisco Bay Area offers many varieties of climate within a few miles. In the Bay area, for example, the average maximum temperature in July is about 64 °F (18 °C) at Half Moon Bay on the coast, 87 °F (31 °C) at Walnut Creek only 25 mi (40 km) inland, and 95 °F (35 °C) at Tracy, just 50 mi (80 km) inland. [11]
• The Los Angeles and San Diego areas are also subject to phenomena typical of a microclimate.[ citation needed ] The temperatures can vary as much as 18 °F (10 °C)) between inland areas and the coast, with a temperature gradient of over one degree per mile (1.6 km) from the coast inland. Hills and mountains can also block coastal air masses. The San Fernando Valley is usually much warmer in summer than most of Los Angeles, because the Santa Monica Mountains usually block the cool ocean breezes and fog. Southern California has also a weather phenomenon called "June Gloom" or "May Grey", which sometimes gives overcast or foggy skies in the morning at the coast, but usually gives sunny skies by noon, during late spring and early summer.
• The Big Island of Hawaii is also an area known for microclimates,[ citation needed ] as Kailua-Kona and Hilo, Hawaii experience rainfall of 18 in (460 mm) and 127 in (3,200 mm) per year, respectively, despite being just 60 mi (97 km) from each other.
• Calgary, Alberta is also known for its microclimates.[ citation needed ] Especially notable are the differences between the downtown and river valley/flood plain regions and the areas to the west and north. This is largely due to an elevation difference within the city's boundaries of over 1,000 ft (300 m), but can also be attributed somewhat, to the effects of the seasonal Chinooks. [12]
• Halifax, Nova Scotia also has numerous microclimates.[ citation needed ] Coastal temperatures and weather conditions can differ considerably from areas located just 5–15 km (3.1–9.3 mi) inland. This is true in all seasons. Varying elevations are common throughout the city, and it is even possible to experience several microclimates while traveling on a single highway due to these changing elevations.
• Chesapeake Bay is also known for its subtropical microclimate. [13] It is most notable for its mild climatic effects on the area east and west of the lowlands of Maryland and Delmarva. Having over 64,000 square miles of water; (most of which is a mix of fresh and salt water) creates higher levels of humidity and heat in the spring and summer months. An example of this effect is the survival of tropical palm trees and plants such as water hyacinths [14] in the area. [15] [13]
• Chile Chico and Los Antiguos on the southern shores of General Carrera Lake have favourable conditions for agriculture despite being in inner Patagonia. [16]

### Europe

• Known for its wines, the Ticino region in Switzerland benefits from a microclimate in which palm trees and banana trees grow.[ citation needed ]
• Gran Canaria is called "Miniature Continent" for its rich variety of microclimates.[ citation needed ]
• Tenerife is known for its wide variety of microclimates.[ citation needed ]
• Biddulph Grange is very rich with microclimates as a result of the large dips and variety of very large trees alongside a large amount of water.[ citation needed ]
• Leeds, located in Yorkshire, England is known to have a number of microclimates because of the number of valleys surrounding the city centre.[ citation needed ]
• The coastal areas in the Andalusia region of Spain has a microclimate.[ citation needed ] It typically averages around at 30 °C (86 °F) in summer, but Tarifa only averages 24 °C (75 °F). Further north along the coast Cádiz has a summer average of 27 °C (81 °F) withco warm nights, whereas nearby Jerez de la Frontera has summer highs of 33 °C (91 °F) with inland areas further north such as Seville being even hotter.
• Sorana, a commune in Italy's Pescia Valley with a microclimate considered ideal for growing the Sorana bean. [17]

### Asia and Oceania

• Amman, Jordan has extreme examples of microclimate, and almost every neighbourhood exhibits its own weather. [18] It is known among locals that some boroughs such as the northern and western suburbs are among the coldest in the city, and can be experiencing frost or snow whilst other warmer districts such as the city centre can be at much warmer temperatures at the same time.
• Yazd and Kashan in Iran, the traditional architecture benefits from central courtyards with trees and water pools that function together with wind catchers to create a favorable microclimate in this desert area.[ citation needed ]
• Sydney, Australia has a microclimate occurring prominently in the warmer months.[ citation needed ] Inland, in Sydney's western suburbs, the climate is drier and significantly hotter with temperatures generally around 3–7 °C (5–13 °F) above Sydney CBD and Eastern Suburbs (the coast), as sea breezes don't penetrate further inland. In summer, the coast averages at 25.9 °C (78.6 °F), while inland varies between 28 and 30 °C (82 and 86 °F), depending on the suburb. [19] [20] In extreme occasions, the Coast would have a temperature of 24 °C (75 °F), while a suburb 20 km (12.43 mi)) inland bakes in 36 °C (97 °F) heat. However, winter lows in the West are around 3–5 °C (5–9 °F) cooler than the coastal suburbs, and may provide mild to moderate frost. [21] Within the city and surrounds, rainfall varies, from around 682.5 mm (26.87 in) in the far-west to 1,213.8 mm (47.79 in) at Observatory Hill (the east or the coast). [22]

## Related Research Articles

Peru is a country on the central western coast of South America facing the Pacific Ocean. It lies wholly in the Southern Hemisphere, its northernmost extreme reaching to 1.8 minutes of latitude or about 3.3 kilometres (2.1 mi) south of the equator. Peru shares land borders with Ecuador, Colombia, Brazil, Bolivia, and Chile, with its longest land border shared with Brazil.

An urban heat island (UHI) is an urban area or metropolitan area that is significantly warmer than its surrounding rural areas due to human activities. The temperature difference is usually larger at night than during the day, and is most apparent when winds are weak. UHI is most noticeable during the summer and winter. The main cause of the urban heat island effect is from the modification of land surfaces. Waste heat generated by energy usage is a secondary contributor. As a population center grows, it tends to expand its area and increase its average temperature. The term heat island is also used; the term can be used to refer to any area that is relatively hotter than the surrounding, but generally refers to human-disturbed areas.

Norway is a country located in Northern Europe on the northern and western parts of the Scandinavian Peninsula. The majority of the country borders water, including the Skagerrak inlet to the south, the North Sea to the southwest, the North Atlantic Ocean to the west, and the Barents Sea to the north. It has a land border with Sweden to the east and a shorter border with Finland and an even shorter border with Russia to the northeast.

Alpine tundra is a type of natural region or biome that does not contain trees because it is at high elevation. As the latitude of a location approaches the poles, the threshold elevation for alpine tundra gets lower until it reaches sea level, and alpine tundra merges with polar tundra.

The Santa Cruz Mountains, part of the Pacific Coast Ranges, are a mountain range in central and northern California, United States. They form a ridge down the San Francisco Peninsula, south of San Francisco. They separate the Pacific Ocean from the San Francisco Bay and the Santa Clara Valley, and continue south to the Central Coast, bordering Monterey Bay and ending at the Salinas Valley. The range passes through the counties of San Mateo, Santa Clara, Santa Cruz, San Benito and Monterey, with the Pajaro River forming the southern boundary.

A Mediterranean climate or dry summer climate is characterized by dry summers and mild, wet winters. The climate receives its name from the Mediterranean Basin, where this climate type is most common. Mediterranean climate zones are typically located along the western sides of continents, between roughly 30 and 45 degrees north and south of the equator. The main cause of Mediterranean, or dry summer climate, is the subtropical ridge which extends northwards during the summer and migrates south during the winter due to increasing north-south temperature differences.

An oceanic climate, also known as a marine climate or temperate oceanic climate, is the Köppen classification of climate typical of west coasts in higher middle latitudes of continents, and generally features cool summers and cool but not cold winters, with a relatively narrow annual temperature range and few extremes of temperature. Oceanic climates are defined as having a monthly mean temperature below 22 °C (72 °F) in the warmest month, and above 0 °C (32 °F) in the coldest month. This climate type is often caused by the onshore flow from the cool, high latitude oceans that are found west of their location.

A humid continental climate is a climatic region defined by Russo-German climatologist Wladimir Köppen in 1900, typified by four distinct seasons and large seasonal temperature differences, with warm to hot summers and cold winters. Precipitation is usually distributed throughout the year. The definition of this climate regarding temperature is as follows: the mean temperature of the coldest month must be below −3 °C (26.6 °F) 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 Dfb, Dwb and Dsb subtypes are also known as hemiboreal.

London, the capital of the United Kingdom and largest city in the United Kingdom, has a temperate oceanic climate, with mild summers and cool winters. While the city annually has modest precipitation, annually averaging less than cities like Rome, New York City, or Shanghai, unlike those cities, London has many long periods of overcast skies and frequent light mist-type precipitation, which may account for the rainy image of the city. Nevertheless, London averages about 1600 hours of sunshine annually, which is comparable with most northern European capitals. Like much of the U.K., the climate of London is shaped by the onshore flow of the high latitude Atlantic Ocean, which brings moist, cool air, and frequent cloudy skies.

The Halifax Regional Municipality (HRM) in Nova Scotia, Canada has a widely varied geography.

Blue Mountain Resort is a ski resort located near Palmerton, Pennsylvania, on Blue Mountain in the northern part of the Lehigh Valley, in Pennsylvania. Blue Mountain serves the Allentown, Philadelphia, New York City, and Wilmington urban areas, as well as Carbon County, Schuylkill County, and the Hazleton area.

Bear Creek is a ski resort near Macungie, in the Berks County region of Pennsylvania, in the United States. The resort opened in 1967. It was known as the Doe Mountain until 1999.

California's climate varies widely from hot desert to polar, depending on latitude, elevation, and proximity to the coast. California's coastal regions, the Sierra Nevada foothills, and much of the Central Valley have a Mediterranean climate, with warmer, drier weather in summer and cooler, wetter weather in winter. The influence of the ocean generally moderates temperature extremes, creating warmer winters and substantially cooler summers in coastal areas.

The climate of San Diego, California is classified as a Mediterranean climate. The basic climate features hot, sunny, and dry summers, and cooler, wetter winters. However, San Diego is much more arid than typical Mediterranean climates, and winters are still dry compared with most other zones with this type of climate.

Australia's climate is governed mostly by its size and by the hot, sinking air of the subtropical high pressure belt. This moves north and south with the seasons. The climate is variable, with frequent droughts lasting several seasons, thought to be caused in part by the El Niño-Southern Oscillation. Australia has a wide variety of climates due to its large geographical size. The largest part of Australia is desert or semi-arid. Only the south-east and south-west corners have a temperate climate and moderately fertile soil. The northern part of the country has a tropical climate, varying between tropical rainforests, grasslands and desert.

The climate of Massachusetts is mainly a humid continental climate, with warm summers and cold, snowy winters and abundant precipitation. Massachusetts is a state located in the New England region of the northeastern United States. Most of its population of 6.4 million live in the Boston metropolitan area. The eastern half of this relatively small state is mostly urban and suburban. Massachusetts is the most populous of the six New England states and ranks third in the nation by population density and fourth by GDP per capita. Massachusetts receives about 43 inches (1016 mm) of rain annually, fairly evenly distributed throughout the year, slightly wetter during the winter. Summers are warm with average high temperatures in July above 80 °F (26.7 °C) and overnight lows above 60 °F (15.5 °C) common throughout the state. Winters are cold, but generally less extreme on the coast with high temperatures in the winter averaging above freezing even in January, although areas further inland are much colder. The state does have extreme temperatures from time to time with 90 °F (32.2 °C) in the summer and temperatures below 0 °F (-17.8 °C) in the winter not being unusual.

The climate of Hungary is characterised by its position. Hungary is in the eastern part of Central Europe, roughly equidistant from the Equator and the North Pole, more than 1,000 kilometres (600 mi) from either and about 1,000 kilometres from the Atlantic Ocean.

The average annual temperature in Estonia is 5.2 °C (41.4 °F). The average temperature in February, the coldest month of the year, is −5.7 °C (21.7 °F). The average temperature in July, which is considered the warmest month of the year, is 16.4 °C (61.5 °F). The climate is also influenced by the Atlantic Ocean, the North-Atlantic Stream and the Icelandic Minimum, which is an area known for the formation of cyclones and where the average air pressure is lower than in neighbouring areas. Estonia is located in a humid zone in which the amount of precipitation is greater than total evaporation. The average precipitation in 1961–1990 ranged from 535 to 727 millimeters per year and was heaviest in late summer. There were between 102 and 127 rainy days a year, and average precipitation was most plentiful on the western slopes of the Sakala and Haanja Uplands. Snow cover, which is deepest in the south-eastern part of Estonia, usually lasts from mid-December to late March.

The climate in Spain varies across the country. Spain is the most climatically diverse country in Europe with 13 different Köppen climates, excluding the Canary Islands, and is within the 10 most climatically type countries in the world. Five main climatic zones can be distinguished, according to Guzman geographical situation and orographic conditions:

The Alentejo is a geographical, historical and cultural region of south central and southern Portugal. In Portuguese, its name means "beyond the Tagus river" (Tejo).

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