Darkest Before the Dawn

It has been very, very dark around here lately.  

 In fact, the measurements of solar radiation on top of the atmospheric sciences building showed that today was the 6th darkest day since the beginning of the year, with Sunday being the fourth darkest (thanks to Mark Albright for supplying these numbers).  Here is the total daily radiation in megajoules per day per square meter (megajoules is an amount of energy) for the darkest days of the year:

19 Nov 2012 0.47 

23 Nov 2012  0.49
4 Jan 2012    0.76

9 Dec 2012    0.79
15 Jan 2012   0.93
11 Dec 2012   0.94
22 Jan 2012   0.99

In mid-summer we often get above 20, and occasionally above 30.  Yes, we can get 20-30 times more radiation in summer than during this dark days.  No wonder we feel better then.


But I have some very good news for those with Seasonal Affective Disorder (SAD) or the need to wear sunglasses... sunset is no longer moving earlier and today sunset actually occurred slightly later than yesterday.

Here are the sunrise/sunset table for Seattle. Sunset has bottomed out at 4:18 PM and WILL BE 4:19 by Sunday.  A reason to rejoice.  Now the day is still getting shorter and will continue to do so until December 21st, so don't get too excited. 

Does the sun look any bigger to you during December?   Did you know we are closest to the sun during midwinter?  The table shows our distance to the sun; you can see we are getting closer and closer!  If that weren't true our winters would be even cooler.  We are actually farther from the sun during summer.

The shortest day of the year and the earliest sunset do not coincide because the day is not exactly 24 h and the earth's orbit around the sun is not circular.  But those details belong in an astronomy blog.

Super dark days like today start with weak winter sun and add to it a deep, multilevel cloud deck.   Here is the visible satellite picture for this afternoon at 1 PM Tuesday--you can see the thick frontal cloud band that messed up our day.

More good news: today will be a bit brighter, with no major system in our area.  At least the darkness and clouds keeps the influx of Californians down to a reasonable level.  Let them think we are the land of darkness, rain, and vampires.