This article is cross posted from Tim’s blog as of interest to some Talkshop readers with a few extra sentences likely to raise discussion.
August 2014 there was a meteorological gift of both exceptional conditions and good data. What can be learnt?
Three Met Office sites showed a signature of exponential cooling. This requires clear sky and a calm. Given somewhat limited parameter hourly data the following shows the commonality. The computed terminal conditions are shown later in this article.
Benson and Santon Downham data has been normalised to Katesbridge, which has the least noisy data or the three.
Achieving a close overlay requires taking earth rotation into account, dusk and dawn move relatively both by geographic location and the peculiar movement throughout the year as night length changes, these do not move together . Fractional delay (less that the sample period) was used to equalize diurnal time. (see the two blog articles here)
Dusk appears to be the important factor, a surprising finding, I assume cooling is time from dusk, dawn terminates cooling.
General information, under essentially calm conditions wind drops for a period during the night then reappears just after dawn. (not shown here)
Temperature normalisation defined is for the cold period, not as accurate for Benson where the better site exposure (more open) led to more wind at times.