March 24, 2010 - Warming Winds

By: Mallory Brooke
By: Mallory Brooke

Wind direction plays a major part in how warm or cold we get on a certain day. Usually wind with a northerly component cools us down, but not always. Read today's blog to learn more about downslope winds and why they warm us up.

Winds from the south typically bring warmer air. Winds from the north typically bring cooler air. That's just simple warm air advection or cold air advection. But we live in a mountainous area - with the Appalachians to the west and the Blue Ridge to the east - therefore we receive much more than the typical warm or cold air advection.

We're all very familiar with upslope flow - that's why the mountains see more cloud cover and rain/snow showers than the majority of the Valley. But what goes up must come down. Hence, downslope.

We've seen this many times - a cold front moves through and winds start cranking out of the northwest. Many times the higher elevations are experiencing rain and/or snow or simply covered by clouds, but the Valley is clear and significantly warmer.

Downslope wind (as you guessed) is wind that moves down the slope of a mountain. This flow produces sinking air, ultimately drying and warming the air that reaches the Valley. Winds originate near the summit and start their way down the lee side of the mountain. Descending air warms at a rate of 10 degrees Celsius per kilometer. This is also known as the dry adiabatic lapse rate (the rate of decrease (or increase, in this case) of temperature with height of a parcel of dry air). This keeps the lee side of the mountain warmer and drier than the windward side of the mountain.

Whatever the reason is for warmer air - we're enjoying it! Take advantage of Wednesday, it's the nicest day of the week!

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