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Do you live in a microclimate? Science Behind the Forecast explains microclimates

A woman stands underneath Fourth Street Live's roof while waiting for the thunderstorm to pass on Tuesday, July 3.
Michelle Hanks
A woman stands underneath Fourth Street Live's roof while waiting for the thunderstorm to pass on Tuesday, July 3.

Every week WAVE 3 meteorologist Tawana Andrew breaks down what we know and what we don't about the climate and weather here in Louisville.

Bill Burton: It's time for us to take a look at the Science Behind the Forecast as I am joined by WAVE 3 meteorologist Tawana Andrew. Good morning, Tawana.

Tawana Andrew: Good morning. Today we're talking about something a little smaller than usual.

BB: I see what you did there, that smaller thing is a microclimate. What do we need to know about a microclimate?

TA: So the National Weather Service defines a microclimate as the climate of a small area such as a cave, a house, city, or valley that may be different from the rest of that region. And usually, it references terrestrial environments, but it can also refer to a body of water. Microclimate conditions can depend on a couple of things. It can depend on temperature, wind, humidity, atmospheric turbulence, frost, evaporation, transpiration, heat balance, dew, and even the type of soil in an area can influence a microclimate.

BB: So pretty much everything.

TA: Pretty much everything. Let's start off with the soil because this is the part that I find pretty interesting. In the case of soil, sandy soils are more responsive to daily high and low temperatures. So the soil that Sandy will actually reflect more heat, and has a less significant reaction to day to day heating. However, when soil is saturated, it will actually increase the humidity and evaporation in a particular area. So it's actually pumping more moisture back into the air. If soil becomes too dry, then it can actually keep additional moisture from being pulled into the atmosphere. And in some situations, it could keep a drought ongoing for a long time. So it's a crazy feedback loop in that kind of a situation. And then for plants, they control the amount of water vapor being pumped into the atmosphere daily through transpiration. So they're just moving all of that moisture into the air. And plants can also help to protect the soil and reduce temperature swings. That's why you hear a lot about people wanting to plant all these trees in urban areas. That's exactly why. Topography can also influence an area's microclimate. It can influence the winds, path and humidity. So let's say we're on the windward side of a hill or mountain, air rising actually decreases in pressure. And as that happens, we have the moisture condensing into clouds, and eventually you can get precipitation on that side. Now on the leeward side of a mountain, what happens is the air is sliding down, and it's heated and compressed and that actually encourages hotter and drier conditions. That's why you can have two very different climates on each side of a mountain just depending on how the wind typically blows. Cities on their own can be their own microclimate because they typically have distinctly hotter temperatures compared to nearby country areas. Urban heat island effects can vary from city to city, just depending on the distribution of buildings, factories, homes, and even the heights of our buildings in those cities. Temperature is in the core of a city, and we know this very well in Louisville, temperatures in the core of like, let's say Louisville will be substantially higher in some cases five to 10 degrees warmer than what we see in suburban and rural areas.

This transcript was lightly edited for clarity

Bill Burton is the Morning Edition host for LPM. Email Bill at bburton@lpm.org.

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