Mars - Earth program
School Weather Examples

Solar blight
James E. Tillman

  • Environmental -- Technology conflicts

    On Saturday, 18 September, 1999 I went to my office to work on a K-12 education module and its temperature sensors, making certain to arrive before the football crowd gridlock began. I decided to check the weather at our school sites, Coe a grade K-5 school and McClure a grade 6-8 school, as well as our Atmospheric Sciences Dept. roof. (Coe is a few miles west of UW while McClure is about 1/2 mile east of Coe.) Being a quite clear day, the Coe observation was as expected (the rapid rise in the morning is due to a hill to the east), and agreed with McClure. However,

    [Solar radiation on 1999/09/18 at Coe school]
    Solar radiation
    Coe School
    ( Note, all times are GMT which is 8 hours later than PST)

    [Plot of Solar radiation at McClure]
    Solar Radiation
    McClure Schol

    [Plot of Solar Radiation at University of Washington]
    Solar Radiation
    University of Washington

    the rapid decrease in our ATG (Atmospheric Sciences/Geophysics building) rooftop observations shortly after 19:00 GMT, immediately above, seemed quite unrealistic. Sitting in my office 4 floors below the roof, I began to speculate about faulty wiring, (that should have caused a complete loss), data logger problems (that should have affected all variables and I have never seen one of these data loggers have ANY problem), or sensor problems. Since the sensor it is an Eppley and has NO active electronics, merely a thermopile, costs more than $2,000 and we had just paid over $1,000 to have it refurbished and recalibrated, that also seemed unlikely. Running out of plausible hypotheses, the only recourse was to form an investigative committee (of one). Reaching the base of the mast, the solution to my mystery was obvious to even the most amateur detective; a direct hit on the polished glass dome of the solar sensor and its neighboring sensor by a BIRD! The cross arm supporting the wind and humidity sensors, 5 to 10 meters above the solar sensors, offers a panoramic view for birds.

    Two morals might be drawn:

    This page is: http://www.atmos.washington.edu/~mars/weather_school/seattle_solar_blight.html
    Linked from      http://www.atmos.washington.edu/~mars/
    Italicized font indicate active web link Created 99/09/25
    Last update 2001/06/23

    J Tillman