Monday, December 13, 2010

Oops ...

I have made an embarrassing discovery: I have been using the wrong rainfall data for Canberra. The rainfall data that I have been using was from here: http://www.bom.gov.au/climate/dwo/IDCJDW2801.latest.shtml

I had made the assumption that this data was the same as the date from here:

http://www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=139&p_display_type=dataFile&p_startYear=&p_stn_num=070014

This is not the case, as I would have realised had I been paying attention:

"Source of data

Observations were drawn from Canberra Airport {station 070351}.

Weather observations for Canberra were previously taken at a nearby site {number 070014}. These can be seen on the "Canberra Airport" Daily Weather Observations; you may need to consult these to get all the relevant data."

My predictions were based on the data from station 070014, as the data from station 070351 only goes back to the middle of 2008. This can be seen here:

http://www.bom.gov.au/jsp/ncc/cdio/weatherData/av?p_nccObsCode=139&p_display_type=dataFile&p_startYear=&p_stn_num=070351

So, at the moment it is not clear that my prediction has been falsified. I think that it has, but I will not know for certain until some time early next year.

To be sure that this is the data that I used, please read this post:

http://evilreductionist.blogspot.com/2010/01/future-of-rainfall-in-canberra.html

You can check the 10-year averages for temperature and rainfall from the data obtained from site 070014 and see that the slope between them is practically identical to the one displayed in the above post. The very small difference is due to slight corrections in the 2009 data, the latter part of it being still provisional in January 2010.

To go back a step, you can bring up the data by entering the site number into this web page: http://www.bom.gov.au/climate/data/

So: we will soon see if my prediction has been falsified (which it likely has been).

Another consequence of this error on my part is that inflow for the rest of the year will be higher than it otherwise would have been, as the rate of inflow for megalitre has increased (due to there having been less rainfall at station 070014). Thus, my estimate for the inflow - and I must estimate it, because it cannot be measured as the dams are all above 100 per cent - will be greater. At present, that does not matter, as we have not had much rain since reaching 100 per cent. But rain is expected soon.

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