The featured graph and images are from the Ames SchoolNet Site and Webcamera. The time series is of instantaneous solar radiation sampled every minute. Notice how the curve transitions from smooth to choppy in the afternoon and then smooth again just before sunset. The shape of this curve tells the story shown in the featured 3 webcam images, a transition from clear skies to party clooudy to mostly clear at sunset. The solar radiation curve becomes choppy as the sun plays peekaboo with the clouds as opposed to being a pure function of location in the sky during optically clear situations.

Voting:
Good = 23
Bad = 6

Tags:   sun   radiation  

The featured graph has a lot going on. The three data lines are from the NSTL Flux site near Ames for Tuesday morning. The green line is long wave radiation and simply shows the period up until 5 AM which was cloudy (clear sky values are around -100 W m**-2). The orange line is short wave (solar) radiation and its obviously near 0 until sunrise around 8 AM increasing to around 400 W m**-2 at midday. The air temperature trace in red shows three distinct regimes during this period.

• Between midnight-5AM: Cloudy skies trap heat near the surface (decreased long wave) and temperatures slowly cool.
• Between 5AM-8AM: Skies clear, long wave radiation increases, and air temperatures cool rapidly at 4 times the rate with clouds.
• 8AM - after: The sun rises and short wave radiation exceeds long wave radiation (net radiation positive) and the result is heating.

Really great stuff! You can view plots like these here.

Voting:
Good = 29
Bad = 9

Tags:   radiation