Friday, 21 December 2012

Weather watching continues

After my previous post I concluded that the position in which I had placed the new station was slightly under-recording rain and was also rather sheltered from Northerly winds.  Thus a move was needed.

In deciding where to move it, I was a tad restricted (I thought) by the advertised range of the station: 50m.  However on contemplating what was involved I decided it should be quite easy to shift the whole device about 10m to the location of the old rain gauge and see if communication continued.  It did!

There has only been one rain shower thus far which seemed to record a little over 0.5mm (ie 3/7 of 5/8 of sod-all) in the old rain guage and 0.6mm in the new one.  Close enough I think.  [On 23 December we had a heavy thnderstorm in the afternoon which recorded a bit over 15mm in the old gauge and 15.3mm in the new one.  Confirms reliability.]

There has also been quite a bit more recording of Northerly wind (matching the basic weather technique of "looking out the window") so the shelter issue also seems to have been resolved.

I have played about with the data a little more to compare Indoor and Outdoor temperatures in a few ways and have a think about how to record/present wind.

The first graph plots indoor (blue line) and outdoor (maroon line) temperatures each hour.  The pattern is quite similar but the level of variation far less for indoors.
 The next graph shows the average temperature recorded for each hour.  The extra cooling outdoors overnight was as expected but the relatively high average temperatures indoors during the day were a surprise.  This suggests that my mental image of what has gone on doesn't allow enough for the days when the house stays warmer than outside manages.
A graph of maximum temperatures recorded for each hour over a 12 day period shows more like the expected pattern.
 WRT to wind the station generates two measurements: the wind speed at 9 minutes past the hour (because I originally connected it up at 9 minutes past some hour or another) and the maximum gust of wind in that hour.        I added the hourly readings for a day together to get a number resembling the windrun. Looking at 310 observations the windrun and maximum gust per day correlate quite well (R=0.81).  It would appear, on this small sample, either measure would serve as an indicative answer to the question "Was it windy recently?"

No comments: