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  • This is Mike Petrucelli with the National Weather Service office in Medford, Oregon

  • with a video on the Spring Equinox. With the recent change over to Daylight Savings Time

  • and the warmer weather, you may be wondering when the first official day of spring is and

  • what that means for the weather in our area. This graphic shows the earth’s tilt in its

  • orbit around the sun. This tilt leads to our changing seasons and the amount of daylight

  • through the year. We are currently moving from the Winter Solstice toward the Spring

  • Equinox. Our Spring Equinox will occur at 4:02am on March 20th.

  • The first days of spring and fall are referred to as equinoxes because there are nearly 12

  • hours of day and 12 hours of night throughout the northern and southern hemispheres. As

  • you can see in the picture, the sun angle is 90 degrees at the equator at solar noon.

  • Solar noon is the time when the sun is at its highest point in the sky for the day.

  • These images show the amount of daylight expected across the globe on the first day of summer,

  • winter and spring and fall. Since Medford is near 42 degrees north latitude, daylight

  • will be near 12 hours on the first day of spring, increasing to 15 hours and 17 minutes

  • on the first day of summer. Daylight then decreases back to near 12 hours by the first

  • day of fall until it bottoms out at 9 hours and 4 minutes on the first day of winter.

  • This figure shows the path the sun takes across the sky during the spring and fall, winter

  • and summer. The sun takes a lower path in winter and increases each day until it reaches

  • its highest point on the first day of summer. This day is also known as the Summer Solstice.

  • This image shows where the sun angle is at solar noon in the winter, spring/fall and

  • summer in Medford. In the winter, when the sun angle is lower, the mountains block more

  • direct sunlight keeping the valleys cooler. As the sun angle gets higher, more energy

  • is concentrated over the same area allowing the surface and atmosphere to heat up more.

  • There is also less blockage from the mountains in the valleys allowing them to heat more.

  • What does this mean for our weather as we move into spring and summer? Warmer days and

  • less fog. We hope youve enjoyed this brief educational

  • video on what the Spring Equinox means. Here are several websites you can use to stay up

  • to date on the latest forecast. Thank you for listening.

This is Mike Petrucelli with the National Weather Service office in Medford, Oregon

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2013年春分 (Spring Equinox 2013)

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    Bing-Je 發佈於 2021 年 01 月 14 日
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