We spend our entire lives in it, but the average Joe on the street has most likely never heard of it. This article was made to The boundary layer is an essential concept in meteorology. It is the section of the atmosphere that directly interacts with Earth’s surface (example: rain falling from the clouds to the ground), which typically extends about a few kilometers. So what, you may be asking, makes the boundary layer so unique?
- It is where we live.
We humans call the boundary layer home. It is where we build, pollute, and change the environment around us. The schematic below shows a rough example of how deep the boundary layer can be, though this changes spending on atmospheric conditions.
- It can vary depending on the time of day and season.
During the daytime, temperatures rise, and heat at the surface causes turbulent motion. This is known as ‘thermally-driven turbulence,’ and it works in conjunction with mechanically-driven turbulence (which occurs from wind flow around buildings or other surface obstacles) to create a convective, unstable atmosphere. However, when the sun goes down, the temperature does too, and the thermally-driven turbulence subsides. Only mechanically-driven turbulence remains, causing the atmosphere to become less convective and more stable during the night. This is generally how the boundary layer behaves during the daytime and nighttime. One can imagine how much more unstable the boundary layer gets during summer, where temperatures are warmer, compared to winter, where temperatures are colder.
- Man-made devices can impact it.
It isn’t just the time of day and year that influences the boundary layer; human creation can also alter it. A great example of this is wind farms. It has been found in multiple scientific studies that wind turbines can affect the flow by slowing down wind speed, but increasing turbulence. These are referred to as ‘wakes.’ Alternatively, the boundary layer can also impact the turbines themselves, such as when regions are prone to severe weather, which can damage the turbines. It’s an interesting dual effect that takes place here!
- Going with the Flow.
Wind flow in the boundary layer has the power to transport heat, moisture, and pollution to different locations. This process is known as ‘advection,’ and it is an important concept to understand from a human health perspective. For example, the air quality in an area could be perfect at first glance, but if the wind speed and direction is expected to push a ton of pollutants from nearby power plants later in the day, it could be hazardous to people with poor health conditions.
- A farmer’s almanac.
Agricultural production is highly dependent on the conditions of the boundary layer. Climatological measurements of temperature, dew point, soil moisture, and other factors can help farmers understand the best and worst times to grow crops. A good depiction of this is provided at the museum where the Mesonet Tower and the Farmbot Genesis are located.
There are many exciting components of the boundary layer, and there are still many to be discovered. Research is ongoing to understand more about the processes that occur within it. It may be a small part of the atmosphere, but it definitely deserves our appreciation!
By: Arianna Jordan
References:
“The atmospheric boundary layer is your home.” Penn State College of Earth and Mineral Sciences, https://www.e-education.psu.edu/meteo300/node/711
“Mesoscale and Boundary-Layer Meteorology.” UC Davis Atmospheric Sciences, http://atm.ucdavis.edu/research/boundary-layer-and-mesoscale-meteorology/
“Atmospheric Boundary Layer with respect to the Troposphere and Stratosphere.” ResearchGate, https://www.researchgate.net/figure/Atmospheric-Boundary-Layer-with-respect-to-the-Troposphere-and-the-Stratosphere_fig1_269519800