recentpopularlog in

robertogreco : meteorology   3

Why San Francisco Gets So Windy and Foggy in the Summer | Bay Curious | The California Report | KQED News
"Every day Will Pearson bikes from his home in San Francisco's Marina district to his office in the Financial District. His morning ride along the Embarcadero is pleasant and calm, but he has noticed the wind picks up significantly on his ride home.

"I’ve always wondered why different parts of the day have such different levels of wind," said Pearson.

Fortunately, it's not too complicated, said meteorologist Jan Null.

Here's the simple explainer from KQED cartoonist Mark Fiore."

[image]

"For more detail, here's the breakdown.

Why it's windier in the afternoon

• Air always moves from areas of high pressure to areas of low pressure.
• Hot air rises and is less dense, and is typically low pressure, while cold air sinks and is dense, and is typically higher pressure.
• Over the course of the day, the air inland heats up in California. But air remains cool over the ocean — where the water stays about the same temperature all day.
• The cold, high-pressure air from over the ocean rushes inland, toward the warm, lower pressure air.
• It takes the path of least resistance, squeezing through sea-level gaps in the mountains and ridges — the biggest of which is at the Golden Gate.
• This creates something known as the Bernoulli Effect. "Think about a garden hose. You have the water cranked up all the way and you have the flow coming out of it. Well, you put your thumb over it, you restrict it down, and all of a sudden you shoot 20 yards across the driveway," said Null. "The same thing happens if you compress air down to a smaller gap like through the Golden Gate or the San Bruno Gap."

That's why the winds are strongest on the days where it's hottest inland and still cool on the coast, when the temperature and pressure difference is the biggest.

Why it's foggy in the summer

The temperature differences also explain why the Bay Area gets so much fog in the summer.

• There is a system of high pressure over the Pacific Ocean called the North Pacific High. In the summer, it gets stronger, creating big clockwise winds over the ocean.
• Those winds push the surface water of the ocean away from the California coastline.
• Very cold water from deep in the ocean rises to the surface. This is called upwelling.
• Something known as the California Current also brings cold water south from Alaska.
• When the sea breeze blows over this much colder water, condensation forms — creating fog.
• The fog comes inland in the summer for similar reasons as the wind: While it stays cool by the ocean, the high temperatures inland create lower pressure, and the fog is sucked in through gaps in the mountains, like the Golden Gate.

That's why we see picturesque summer fog rolling in past the Golden Gate Bridge in the afternoon.

"Nothing's going to move them out until the sun comes up the next morning and evaporates it," said Null.

Our topography also explains why one neighborhood can be foggy, like the Sunset, and another warm, like the area in Sausalito known as the Banana Belt. The hills and ridges direct the path of the fog and wind, creating these microclimates.

Will our fog and wind remain?

The amount of summer fog has decreased 33 percent over the last century, studies have found. Warming oceans and climate change could continue to affect the complicated weather systems that create our unique Bay Area fog and wind."
sanfrancisco  weather  fog  bayarea  2018  explainer  visualization  markfiore  jannull  meteorology  classideas 
august 2018 by robertogreco
JORINDEVOIGT.COM » -NEWS-
"For the past decade, Jorinde Voigt has been creating large-scale drawings on paper, using traditional materials such as ink, oil stick, pencil, watercolor, and, more recently, collage. In the drawings that she did before incorporating collage, the artist combined line and text to diagram both factual and fictive activities, such as the flight of eagles, geographical directions, wind patterns, rotations, shifting horizon lines, top-ten pop charts, kisses, and electrical currents. Whirling across the paper, the sinuous patterns of lines and arrows—some of which may overlap—mark relentless change as well as convey the potential for chaos and ecstasy that resides within any system. Classification and pandemonium are inseparable. It is on the porous border of this vast abyss—what is called “infinity”—that Voigt investigates the caesuras between perception & knowledge, form and dissolution…"

[Text from PDF: http://jorindevoigt.com/blog/wp-content/wp-content/uploads/J.Yau_J.Voigt_EN2.pdf ]
meteorology  cartography  geography  collage  lines  nature  currents  wind  patterns  taxonomy  classification  johnyau  data  design  illustration  visualization  drawing  artists  art  memory  time  mapping  maps  jorindevoigt  via:selinjessa 
january 2013 by robertogreco
Radarmatic
"You’re looking at the level of precipitation in the air, as measured by a network of weather radar sites called NEXRAD.<br />
<br />
The National Weather Service makes the raw data from 200 radars across the continental US and overseas available on noaa.gov for anyone to use, usually within minutes of being generated. Radarmatic caches and translates the radar data from its native binary format to JSON and then republishes it as a web service.<br />
<br />
The radar imagery on the home page is rendered in-browser using Javascript and the HTML5 canvas element."
weather  maps  mapping  nws  meteorology  html5  geography  radar  faa  dod  dBZ  noaa 
september 2010 by robertogreco

Copy this bookmark:





to read