Microclimate

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For the viticultural use of the term microclimate, see Regional climates levels in viticulture.
Microclimate on rock located in intertidal zone in Sunrise-on-Sea, South Africa

A microclimate is a local atmospheric zone where the climate differs from the surrounding area. The term may refer to areas as small as a few square feet (for example a garden bed) or as large as many square miles.

Microclimates exist, for example, near bodies of water which may cool the local atmosphere, or in heavily urban areas where brick, concrete, and asphalt absorb the sun's energy, heat up, and reradiate that heat to the ambient air: the resulting urban heat island is a kind of microclimate. Microclimates can be found in most places. Another place this can occur is when the ground is made of tar or concrete, because these are man made object's they do not take in much heat they mainly reradiate it.

Another contributing factor to 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.

Background[edit]

Tree ferns thrive in a protected dell area in the Lost Gardens of Heligan, in Cornwall, England, latitude 50° 15'N.

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.[citation needed]

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.

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.

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[edit]

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 [1]

Sources and influences on microclimate[edit]

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[edit]

The well known examples of cold air pool (CAP) effect are Gstettneralm Sinkhole in Austria (lowest recorded temperature -53 C) [2] and Peter Sinks in the US. The main criterion on the wind speed v in order to create a warm air flow penetration into a CAP is the following:

 \mathrm{Fr} = \frac{v}{Nh} \geq \mathrm{Fr}_c,

where \mathrm{Fr} is the Froude number, N --- the Brunt–Väisälä frequency, h --- depth of the valley, and \mathrm{Fr}_c --- Froude number at the threshold wind speed.[3]

Craters[edit]

The presence of permafrost close to the surface in a crater creates a unique microclimate environment.[4]

Caves and lava tubes[edit]

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[edit]

As pointed out by Rudolf Geiger in his book [5] 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.

Dams[edit]

Artificial reservoirs as well as natural ones create microclimates and often influence the macroscopic climate as well (see Environmental impact of reservoirs).

Cities and regions known for microclimates[edit]

Americas[edit]

Europe and Africa[edit]

Asia and Oceania[edit]

References[edit]

  1. ^ Gardening Resources, Cornell University
  2. ^ Microclimate, www.wetter-freizeit.com, in German.
  3. ^ J. Racovec et al. Turbulent dissipation of the cold-air pool in a basin: comparison of observed and simulated development. Meteorol. Atmos. Phys. 79, 195-213 (2002).
  4. ^ Permafrost in Hawaii, NASA Astrobiology Institute, 2010
  5. ^ R. Geiger. The climate near the ground. Harvard University Press, 1957.
  6. ^ "Climate Of California". Wrcc.dri.edu. Western Regional Climate Center. Retrieved 2014-02-02. 
  7. ^ "Calgary’s Gardening Climate". Scarboro.ca. 2008-05-05. Retrieved 2014-02-02. 
  8. ^ Potter, Robert B.; Khadija Darmame; Nasim Barham; Stephen Nortcliff (2008). "‘‘Ever-growing Amman’’, Jordan: Urban expansion, social polarisation and contemporary urban planning issues". Habitat International (www.journals.elsevier.com/habitat-international) 33: 81–92. doi:10.1016/j.habitatint.2008.05.005. Retrieved 2014-02-02. 
  9. ^ "Sydney/Kingsford-Smith International Airport". Climate statistics for Australian locations. Bureau of Meteorology. Retrieved 27 August 2014. 
  10. ^ "Penrith". Climate statistics for Australian locations. Bureau of Meteorology. Retrieved 19 January 2014. 
  11. ^ Sydney’s Climate
  12. ^ "Badgerys Creek AWS". Climate statistics for Australian locations. Bureau of Meteorology. Retrieved 19 January 2014. 

External links[edit]