Sunday, May 03, 2015

South East Queensland and rainfall intensity: so this is what global warming looks like?

Rainfall statistics can be analysed any number of ways, and it seems to me that intensity of rainfall is one of the things that has become very important but is being investigated a bit too slowly. 

My strong, strong hunch is, however, that at least South East Queensland (if not other parts of the country) is now clearly undergoing the type of intensification of rainfall that was always expected under global warming and is suffering badly for it.  

Last Friday's rainfall was deadly, remarkable, and unseasonal across most of the South East, but particularly just to the north of Brisbane.   It reminded me of the intensity of rainfall that led to the Lockyer Valley disasters in the 2011 floods - where all forms of normal drainage (and Brisbane's drainage is built to sub-tropical standards) is so overwhelmed  that the flood is disastrously out of the norm in terms of suddenness of onset.    

But I'm not sure whether we are getting a good analysis of this in a timely fashion.

See, while it's interesting that a daily rainfall total might be a record for the time of year, I don't know that this captures the importance of the hourly intensity of rainfall adequately.

There may well be some academic papers on this around the place, but if so, it seems to me it is not attracting adequate publicity via the Bureau of Meteorology.  (Although I think the public knows something is going on.)

Alternatively, I could be wrong and the intensity is not out of the norm in historic terms.   I very much doubt that is the case, however. 

Update:  my point was alluded to in this article in The Conversation (my bold):
The problem is: “How can we estimate the frequency of rare extreme events from observations, or events that we are yet to witness, such as a 1-in-500-year event?” To solve this problem we need to model the data and use it to extrapolate outside our observations.
When we’re talking about flash floods and extreme rainfall, we want to know the highest rainfall in a single day or in a few hours, rather than total rainfall over longer periods such as a month or year. The best long-term rainfall observations are for daily rainfall.

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