Behind the Forecast: Microclimates

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Science Behind the Forecast: Microclimates

LOUISVILLE, Ky. (WAVE) - Microclimates can play a large role in a specific location’s weather. 

The National Weather Service defines microclimates as "the climate of a small area such as a cave, house, city or valley that may be different from that in the general region."

Usually, the term references glacial and terrestrial environments, but it can also refer to bodies of water. 

Microclimatic conditions can depend on the following:

  • temperature
  • wind
  • humidity
  • atmospheric turbulence
  • frost
  • evaporation
  • heat balance
  • dew
  • soil type

In the case of soil, sandy soils are responsive to the daily high and low temperatures. Soil with lighter colors reflect more heat and have a less significant reaction to heating. Evaporation and humidity both increase when an area's soil is moist. When the soil becomes very dry, it can keep additional moisture from being pulled into the atmosphere, keeping conditions dry.

Plants control the amount of water vapor pumped into the atmosphere each day through transpiration. Plants can also protect the soil, helping to reduce temperature swings.

Topography can also influence an area's microclimate, impacting the wind's path and humidity. Air rising along a hill or mountain decreases in pressure as moisture condenses into clouds and, eventually, precipitation. As the air slides down the leeward side of a mountain, it is heated and compressed, encouraging hotter and drier conditions. 

Cities can be a microclimate of their own since they can have distinctly hotter temperatures compared to nearby rural areas. Urban heat islands vary from city to city depending on the distribution of buildings, factories, homes, and even the heights of buildings. Temperatures are typically higher in the core of a city and decrease towards the suburban and rural areas. 

Cities can be wetter than surrounding areas thanks to more condensation nuclei being releases by factories, cars, and industrial plants. The heat created by cities can fire up or intensify thunderstorms over and downwind of cities. Urban heat islands can even refuel storms as they pass by. 

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