Friday, 6 December 2013

November Weather report

This is a mixture of information from my own weather station (referred to as an Integrated Sensor Suite - ISS - which has been fixed up by Davis Australia - thanks guys) and from the Bureau of Meteorology website. A comparison between the two series will be covered in the temperature section below.  We will begin however with ...

Rainfall!

We were well above last year's fall, but below the average for the previous 6 years.  

Looking at the year overall we seem to be about normal in terms of the number of days with rainfall, but well down on the number of days with more than 5mm.  Overall I think we are heading for about 600mm of rain in 2013, unless we get a lot more than we are hoping for in December.

Temperature

While my weather station was in in ISS-hospital I took data for the Isabella Plains BoM site as an indicator.  I have compared the two series since getting the ISS back.
The correlation coefficient for maxima was/is 098 (very strong) while for minima is "only" 0.87 (still significant, but not so good).  The key date appears to be the 5th, where BoM recorded a minimum of 11o while the ISS recorded 4.9o.  

(I suspect the problem here is the difference in timing as the BoM "day" runs from 9am to 9am while the ISS does calendar days.  This would require a warm morning followed by a cool evening, and I can't find the data to demonstrate this.  I will note that from the lines in the chart above the BoM observation looks more like an outlier than does the ISS data.)

Overall I believe that combining the two series gives a fair picture of what temperatures have done over the past month.
We had two ground frosts (minimum between 0 and +2o but no minima below 0o.  Three maxima exceeded 30o while a further 9 were between 25o and 30o.

Wind

The following chart shows the BoM maximum gust for the whole month and the ISS maximum gust since it has been back with us.  
Clearly the ISS records lower wind speed than the BoM.  This is not surprising as the ISS is sited far lower than a meteorological standard anemometer.  The correlation between the two series is "reasonable" at 0.51, but not even close enough to good enough to contemplate combining them!

Humidity

I have in the past used 5pm Relative Humidity as my ISS indicator.  In this case the BoM offer 3pm and 9am as their standards so I have used both of those below (with the 3pm one first).

Eyeballing the graphs suggests they travel pretty well together.  This is supported by both correlation coefficients being a very healthy 0.876 (plus small change).

I thought it might be interesting to compare the two BoM series.  
The basic story is  unsurprising with 0900 usually >1500 and both series having a very high value on the day of consistent rain,  However there are a number of days inwhich the day to day changes move in different directions so the series do not correlate strongly.

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