Believe it or not, today is the first day of spring
San Luis Obispo Tribune
Published: Sunday, Mar. 20, 2011
It's difficult to believe with the current Gulf of Alaska storm bearing down on the Central Coast, but today is the first day of spring.Spring is a transition season in terms of weather conditions: not quite summer and not quite winter. You may have stormy weather one day followed by record-breaking heat nearly the next.
However, spring along the Central Coast usually means constant northwesterly winds. It's interesting reading old weather reports from the early 1900s in San Luis Obispo; locals often called these winds the "Los Osos winds" as they blew in from the Los Osos Valley off the Pacific Ocean.
These onshore winds create a great amount of upwelling along our coast, resulting in the coldest seawater temperatures of the year.
It's not uncommon for seawater temperatures along the immediate coastline to drop to 47 degrees — that's just flat cold. You just never get warm diving in 40-degree water, no matter how thick your wetsuit.
Because the calendar year is not exactly 365 days, the first day of spring in the Northern Hemisphere ranges from March 20 to 21.
Earth is on a 23½-degree tilt as it rotates around the sun. This is the reason we have seasons. As Earth orbits around the sun during this time of the year, the Northern Hemisphere becomes more tilted toward the sun, while the Southern Hemisphere tilts away.
When the sun is directly over the equator today, at 4:22 p.m., it's called the vernal equinox. Equinox comes from the Latin phrase for "equal nights."
However, sunrise and sunset are about 12 hours apart everywhere on Earth on this date, but the sunrise and sunset times listed on the PG&E Diablo Canyon weather forecast are not exactly 12 hours apart, as one might suspect.
That's because Earth's atmosphere refracts or "bends" light coming from the sun, so we see the sun a couple of minutes before it actually rises over the horizon and a couple of minutes after the sun sets.
Also, sunrise is classified as the moment the upper edge of the sun's disk appears on the horizon, and sunset is when the upper edge disappears below the horizon adding to the slightly longer days.
As a kid growing up in Santa Rosa, one of the more interesting urban legends that I often heard was the one about easily balancing eggs on their ends during the equinox because of the equal length of the day and night.
With enough patience and practice, you can balance eggs on their ends at any time of the year just as easily as during the first day of spring.
View entire article here: http://www.sanluisobispo.com/2011/03/19/1528698/believe-it-or-not-today-is-the.html#ixzz1HAnGxb2p
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