In some ways, an ECL is easy to describe - it's a low pressure system that occurs off the east coast of Australia, generally defined between Brisbane and eastern Victoria. Low pressure systems, of course, happen around the world and are a major cause of weather everywhere, although we get a bit more than normal for our latitude. A few years back, a study by Speer et al. (2009) found that there are about 22 ECLs a year, of which about 7 cause widespread rainfall totals above 25 mm. They're most common in winter, especially in May and June, but can happen any time of year.
But, as always in science, it gets a bit more complicated than that. Because there are a lot of different things that sometimes get included under the term “East Coast Low” that look quite different to each other, leading to a lot of disagreement on what exactly distinguishes it from any other low. See how different the five ECLs in June 2007 alone looked! So a big low pressure system that comes from the westerly storm track south of Australia, or an ex-tropical cyclone, or a small but intense low that develops in a coastal trough, could all be included under some definitions, and excluded under others.
And then you get into all the different computer-based methods for finding ECLs (none of which do exactly the same thing as human pattern recognition) and different sets of pressure data to find them in, and… you can see how it gets complicated. (We recently published a whole paper comparing different computer-based methods and how their “ECLs” compare with those that Speer et al. found)
So, this means that we can never truly answer the question of “How many ECLs are there each year” – it always depends on what you mean by ECL!
Why do I study ECLs?
In a way I fell into studying ECLs by chance – back when I was doing my masters (in polarimetric radar, a very different thing), I got a part-time job at the Bureau of Meteorology, and the first project I worked on was helping with the Speer et al. paper (making it my first paper!).
At that time, ECLs were suddenly a hot topic of research in NSW, having had a very significant ECL in June 2007 that people are still talking about, thanks to a ship (the Pasha Bulker) that got stuck on a beach just north of Sydney. And thanks to the vagaries of geography, most of the climate researchers in Australia were based in Melbourne and focusing on droughts, leaving the climate of the east coast as fair game for a young, up & coming researcher.
So, since I was based in Sydney, I just started playing with bits and pieces of projects on east coast climate, with a particular focus on ECLs, since they turned out to be one of the biggest causes of severe weather in our region as well as critically important to our dam levels (if you look at a chart of Sydney dam levels you can really see June 2007’s impact!)
This lead to being involved in a multi-agency/university partnership known as ESCCI, where I met the people who would become my PhD supervisors. As to what I’m actually doing in my PhD? That can wait til next time.
Update: Wow, apparently this got some traction! Thanks everyone who was interested - an improved version of this (with less focus on me) is now available here.
Well it's a miserable day in Sydney today, and set to get worse tomorrow as an East Coast Low develops, likely the biggest one since spring last year. So this seems as good a time as any to start my 2015 goal of occasional blogging, starting with the question – what is an East Coast Low, and how did I come to study them?