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Davis, California

Tuesday, September 21, 2021

Davis wind blows strong this season

It’s spring in Davis and the student body is abuzz with excitement for the nice weather. Unfortunately, along with the beautiful sunshine comes another, less-loved phenomena: wind.

If you’ve been at UC Davis for more than a year, the odds are that you have some sort of story in which the wind has embarrassed you.

The wind can be blamed for almost anything from a terrible hair day to physical injury. Stories of the wind blowing people off their bikes are not uncommon. The latter is especially true in the normally hazardous bike circles, where wind adds a new level of difficulty for inexperienced riders who don’t account for the increased resistance and end up poorly executing their overly ambitious moves.

According to Kyaw Tha, a professor in the Environmental Science Department at UC Davis, wind is caused when one current of air pushes another out of the way.

“Pressure gradients — the change in pressure over distance — power the wind,” said Tha in an email interview. “The greater the pressure change within a particular distance, the stronger the wind.”

Many factors contribute to the air in some areas being under greater pressure than in other areas. These factors include the heat capacity of surfaces like water, roads and other infrastructure, as well as the area’s altitude. The basic rules of physics dictate that substances will want to move from an area of high pressure to an area of low pressure, and air is no exception. When the air moves to the low pressure areas, we call it wind.

According to Climate-Zone.com, average wind speeds for the greater Sacramento area peak in April and May at nearly 10 mph. That does not sound like very much, but just consider that for the rest of the year, the average wind speed is closer to between 3 and 5 mph.

“Davis, within the Central Valley, typically has winds determined by larger scale ‘synoptic’ systems throughout much of the year,” Tha said.

This means that our weather depends primarily on high-altitude winds, called Rossby waves, that end up creating pressure gradients over large distances. The more air that moves, the more wind you get.

“During this time of year between high and low pressure systems, the gradients become very strong, so the winds become high,” Tha said.

Furthermore, Davis is flat. Really flat. This will come as no surprise to anyone who grew up in an area with even moderate elevation changes, but it has some important consequences.

Although it doesn’t fit our colloquial understanding of the term, air is defined as a fluid based on its ability to flow, and the study of a fluid moving is termed fluid dynamics.

“In fluid dynamics, flow rate usually increases as resistance decreases,” said Joseph Ephron, a fourth-year mechanical and aerospace engineering double major at UC Davis.

When something blocks the movement of a fluid, it’s said to increase resistance. Thus things like hills, mountains, valleys and even trees all increase resistance for wind.

Unfortunately, Davis has nearly none of those things, so there is nothing to stop the wind from blowing at full speed.

On a smaller scale, closer to the average size of a person instead of a mountain, the buildings on campus provide resistance, forming a sort of tunnel that channels the wind into one area, making the wind very strong, but diluting it in other areas.

In the end, while the question as to why the wind seems so intense in Davis is pretty complex and depends on many factors, the effects of the wind — and the problems it causes — are readily apparent.

For more information on the Sacramento climate, go to climate-zone.com.

KYLE SCROGGINS can be reached at science@theaggie.org.

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