Friday, February 8, 2013

sunshine on the north coast

what is the lowest angle of the sun at which the body can produce vitamin D ? production requires UVB radiation, which is filtered by the atmosphere (most solar radiation is UVA which doesn't help), so it's reduced during the winter

  • this "dr" says 50 degree altitude angle
  • this link suggests that you can make vitamin D in atlanta (34 degrees north latitude) during the dead of winter
  • this page (sketchy sounding url but with legit sounding citations) says 34 degrees north (ie, atlanta-ish again)
this page converts latitude and time to the angle of the sun. 34 degrees latitude maps to an altitude angle of 32.6 degrees at solar noon on the winter solstice. the southern tip of lake erie is 41.38 latitude. the first solar noon that reaches the 34 degree equivalent is feb 5th (33 degree altitude angle)

note: if the 50 degree altitude angle is correct (no citations provided) then march 23 is the critical point

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