Thursday, September 23, 2010

Double climate whammy to bring more rain!

Record rainfall!
Rainfall across many parts of the country has been enormous this year, and there is more on the way. One example of the massive rainfall turn-around from 2009 to 2010 is Alice Springs, which picked up only 77mm in all of last year, but has already had over 500mm so far this year!

Double climate whammy!
One of the main reasons for this above average rainfall is the fact that we have two climate phenomena conducive to above average rainfall happening simultaneously, which is very rare. Off the east coast of Australia in the Pacific Ocean we have a well established La Nina, a climate pattern that occurs every 3-7 years and usually results in above average rainfall across northern and eastern Australia. Meanwhile, off the west coast of Australia in the Indian Ocean, the negative phase of the Indian Ocean Dipole (IOD) is strengthening. When the IOD is in a negative phase, we typically get above average rain across most of Australia. If both of these persist through Spring, it will be the first simultaneous La Nina and negative IOD event since 1975. During this time, the rainfall pattern across the country from June to November was almost identical to what we're experiencing at present with above average rainfall almost everywhere, except for the southwest corner of WA which is unaffected by these two climate phenomena. So it is very likely that we will continue to see above average rainfall across much of the country for the rest of the year.

More cyclones??
One of the signatures of both a negative IOD and La Nina is warmer than normal waters of Australia's northern coastline. This suggests that we may experience a more active tropical cyclone season this year. QLD typically gets 50% more cyclone impacts in a La Nina year compared to a normal year, with as many as double the amount of cyclone impacts in a La Nina year compared to an El Nino year.

No comments:

Post a Comment