Better but Still Needs to Improve

Sunday’s weather did improve on Saturday’s and we even had a little bit of sunshine late in the afternoon.

The morning was dull again but by about lunchtime it was starting to dry up a little. Then the showery rain started and lasted on and off through the afternoon until it brightened up for a short while then more rain arrived late into the evening.

In the morning I’d investigated the data stored by my weather station to see if it could give me some figures to rank really dull days in order. I already have a little extra program to calculate how many hours of sunshine are recorded each day. However, we have plenty of days when this value is zero as we obviously have plenty of days without sunshine.

My weather station also calculates the total amount of solar energy falling on a horizontal surface which is called Global solar exposure.

Global solar exposure is the total amount of solar energy falling on a horizontal surface. The daily global solar exposure is the total solar energy for a day. Typical values for daily global solar exposure range from 1 to 35 MJ/m2 (megajoules per square metre). The values are usually highest in clear sun conditions during the summer, and lowest during winter or very cloudy days.

Reference Australian Government Bureau of Meteorology

I'm presuming the minimum value of 1 MJ/m2 is during daylight hours as this value is obviously 0 MJ/m2 during the hours of darkness. So using this value I've plotted the figures out for all the days in October that my weather station has been operating. The best thing is not to worry about the units just consider that a value of 0 means it’s dark and a value of 35 represents a brilliantly sunny day in Australia. 

Using this as a guide then Saturday was the dullest October day I’ve recorded with a “Martyn’s Dullness Rating” of 0.4. At the top of the rating is 01 October 2011 with a value of 10.2 which coincided with 5.7hrs of sunshine and a temperature of 28.5°C.

I also did a quick check on the sort of maximum values I would record in summer so I checked out the figures for July 2013. The highest value was 22.7 on 09-July-2013 with 9.4 hours of sunshine. Out of interest the lowest value was 04-July-2013 at 4.6 on a day when no sunshine was recorded.

So far Saturday is the dullest day I have on record but I suspect once I've calculated the values for the winter months with their shorter daylight hours I will come up with a smaller value.

I’d now like the weather to improve so that we can continue tidying up in the garden and down on the plot. 

Copyright: Original post from A Gardener's Weather Diary http://ossettweather.blogspot.co.uk/ author M Garrett