During weather broadcasts on television, the term of ‘Advection’ has been thrown into the mix usually when referring to a transfer of cold air or warm air into a specific region that will cause a variation in temperature. This explanation should help to understand the meaning of this term and its uses.
Advection is defined as a transfer of some property by the atmosphere or ocean. This term can actually be very vague unless there is a description of what exactly could be transferred. Most commonly, you will hear terms like ‘cold-air advection’ after the passing of a cold front where cold air is transferred into your region (usually from the North, Northwest or Northeast) resulting in a drop in temperatures. On the contrary, warm-air advection refers to the passing of a warm front that causes a transfer of warm air into your region (typically from the South, Southwest or Southeast) and increase temperatures.
Figure: 12-hour temperature changes depicted from the GFS model on the night of March 1 to the morning of March 2 showing significant cold-air advection over 12 hours to the Oklahoma and Texas area. (Courtesy of pivotalweather.com)
While temperature is the most commonly paired term with advection, there are many more elements that can be transferred from one region to another. Wind can also aid in the transfer of more than just air temperature changes. Modification of air can refer to changing the humidity or dew point as well. Besides modifying the air with moisture, we can also see transfer of dirt, dust, salt or smoke.
The purpose of tracking changes to air temperature help to determine how localized elements will change during a given time. For example, transfer of moist, humid and unstable air to a different region that leads to convective storms (severe thunderstorms and tornados) is essential to track the potential for severe weather. Timing of potential impacts is essential to residents planning a commute or maintaining their personal safety.
Advection is a term that refers specifically to changes based on atmospheric or oceanic transfer. These are a few examples of what the term advection does not refer to: plowing snow from one area to another, watering your lawn, or salting an icy sidewalk or street.
If there are calm conditions at a station, that also does not mean that temperature will not change. Radiative cooling can occur at night with no solar heating and under dry conditions, which allows for heat to radiate from the surface that results in a temperature drop. Solar heating can cause an increase in temperature during the day merely from the warmth of the sun and no interaction from wind.
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© 2019 Meteorologist Jason Maska