Christmas Bells

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Christmas Bells - Blandfordia nobilis

Sunday, January 01, 2012

Rainfall in Robertson in 2011

The rainfall in Robertson in 2011 was very close to "spot on" the long term "mean" figure (what we non-statisticians think of as the "average").

Annual total rainfall for 2011 =  1739.4 mm
The long-term "mean" figure was 1658.7 mm
On my calculations, that means we exceeded the "mean" by just 4.86%.
That is pretty close to the "mean".

For the non-metrically inclined, that means we got 68.48 inches of rain.
Having come from Canberra, 
where the old figure for rain was always "about 25 inches" 
The Botanic Gardens site in Canberra reports 700.3 mm (27.57 inches) 
that is a lot of rain, unless one comes from Tully or Innisfail in Queensland.
Innifail's long-term annual average rainfall is 3580.0 mm (140.9 inches)
Tully's long-term annual average rainfall is 4127.0 mm (162.48 inches)

Do you know what your local rainfall figure is?
Go to this Bureau of Meteorology page
Select "rainfall" in the first box - (there is a small "drop down" list)
Type in the name of your nearest town (without state initials)
then click "find".
"Matching towns" will show closest rainfall stations
Select one (click on it).
Then go to the next button and select the year 2011
(no point in leaving it as 2012 - no records yet)
Click "Get data"
Finally, look underneath the first table
You will see: Annual total for 2011 = xxx.x mm
It will be 1739.4 mm (if you live in Robertson)   

A word of warning, many stations have "data gaps"
If you find "annual total = n.a" (not available)
click on the little box under the data table
"view all monthly data"
Scroll down to the bottom of the table, and look at the 
"summary statistics for all years"
The first line will be "mean".
Go across that line to the last entry "annual"
That is your mean annual rainfall figure.

The Bureau of Meteorology provides several graphing tools on its website for Robertson rain records.
This one graphs the rain on a monthly basis, comparing the actual rainfall (shown in grey columns) against the "mean" rainfall figures (shown in green).
Bureau of Meteorology Graph of monthly rainfall 2011
The standout months are February (for relatively low rainfall), March for very high rainfall (290.2 mm), then July and November for much higher rainfall than the "mean" would lead one to expect.

Bureau graph of daily rainfall, and accumulated total (across the year)
This is an interesting way of assessing the rainfall. May was only our 4th wettest month, yet in two days we got in excess of 150 mm of rain, including 99 mm on the last day of the month. the rest of the month was virtually free of rain.

The other thing to note is that Robertson has a reputation for being a town where it is "always raining". Not this last year.
It clearly experienced statistical "spikes", or heavy downpours, interspersed by long periods of little or no rainfall. 

Storm approaching up the Valley below my house
We had only 7 days when in excess of 50 mm fell in 24 hours. 
One was 99 mm.
Heavy rainfall, in my book. 
I believe it is those "rainfall events" which impress themselves on people's minds. 

Try telling the general public that 
"2011 was not a particularly wet year"
a mere 4% above "normal" 
and they will be surprised.


In that regard, the worst offenders are the
Rural Fire Service head office spokespersons
who routinely report "higher than normal rainfall" and 
then use that false statement 
in an attempt to justify 
more and more "burn-offs" in the bush.
because of the "supposed resultant heavy fuel load in the forests".

At least in this area, that is simply a false statement.

Yes, there is a heavy (very heavy)
build up of fuel in the local forests.
But it is the normal situation.

Besides, the advocates of increased "burn-offs"
seem to fail to understand that
more burn-offs simply promote 
which grow back more quickly 
than the main forest tree species.

Those species (especially Wattles and Pea shrubbery)
actually promote fires.


Flabmeister said...


With that average rainfall and your deep fertile soil no wonder stuff grows so well in Robbo. We struggle with 650mm of rain on rotten shale!

WRT to the fire service folk, I think the experience of recent "controlled" burns in WA says all that is necessary. I once heard one of these guys complaining about use of tan bark in urban yards as being a fire hazard. Unfortunately he was being serious.

Even more unfortunately their views seem to be shared by many Parks people. While this is probably a political imperative one should have thought they would understand more about Botany.


Denis Wilson said...

Thanks Martin
I have edited in some conversion figures, for the old-fashioned amongst us, who still think of rainfall in "inches" (and who amongst us can honestly claim we don't?).
Your rainfall is 25.59 inches.
We got 68.48 inches, last year.
By contrast, Tully, Qld, gets 162.48 inches.

Denis Wilson said...

Hi Martin
It occurs to me that not everybody records their own rainfall, (as you and I do).
I have added in some instructions to help people find their closest rainfall station.
And, with more difficulty, instructions on how people may use the Bureau's wonderful but immensely complicated website, to find their own local rainfall figures.
Thanks for providing the "spark" for me to help people get rainfall data comparisons with their own area.
(Blogging is best, when it is a collaborative art form!)

wildwings said...

Hi Denis, we totalled 4232 mm for the year in Daintree. Although data is collected and reported to the BOM in Daintree Village it is apparently not an "official" station as I can't find any mention of it on their website. However we know our annual average is approx. 3.5 m in this area so we are a little above. Your comments regarding events that stick in people's minds is interesting. We had a lovely 'dry season' in 2011 although it was cut short by early rains it didn't seem like a very wet year.

wildwings said...

I should have added that we had 5049 mm in 2010 - and we do remember that as being a very wet year.

Denis Wilson said...

Hi Barbara
I didn't have any trouble finding Daintree on that page I linked to.
Copy and paste this link (all of it).
There are several stations listed, but some have data gaps.
The official list was not as impressive as your reports.
4232 mm is amazing
Martin, near Queanbeyan, near Canberra, is both dry and also on old, poor soils.
Mind you, his land might not be good for farming, but he gets very nice Native Plants, because they are adapted to his conditions.
The marvels of evolution and adaptation.
You obviously keep your own records anyway, but it is good to be able to check with the official site.