This post is a bit late, but as it is never too late, I'm posting it now. The reason I didn't do it before is that it's a lot of work and I'm not even sure I'm doing it right or if it will have any use at all. But there's only one way to find out...
We are entering the final phase of the melting season. Extent decrease rates are getting lower and lower and soon we will start seeing the first days of extent growth, followed soon after by minimum extent. I figured it might be interesting to have a look at what happened in other years, specifically the years of the 'new Arctic era': 2007, 2008 and 2009. Perhaps we'll see some parallels that give us an idea of when and how the 2010 melting season will end.
I have downloaded a lot of images from different sources and combined them to make animations of the period August 25th-September 24th. The final date is based on when 2007 reached minimum extent.
I'm starting off with air temperatures. I'll explain more about the images below the animation, but have a look first:
Did you notice they keep changing the colour bar to the right? I apologize for that, but there's nothing I can do about it. I have downloaded these images from the Daily Mean Composite page, compiled by the Physical Science Division of NOAA's Earth System Research Laboratory. The daily composites (averages) are based on NCEP/NCAR Reanalysis and other datasets.
When I said I wasn't sure I was doing it right, I meant that I'm not sure if I'm using the right variables. Here's a screenshot of how I got the air temperature images for the periods August 25th-September 24th 2007-2009:
I'll gladly take advice from anyone who likes to fiddle with these parameters and knows what they're doing. I think an analysis level of 925 mb is best for air temperature. I'll be using the same source for another End Zone instalment on Sea Level Pressure (500 mb) in the coming days, so a good tip might save me from having to do things again.
I haven't had a good look at the animation myself yet, but from a quick glance I think I can tell that La Niña year 2008 had much lower air temperatures in September than 2007 and 2009. It's probably not a coincidence then that 2008 had the earliest minimum extent date of the three.
In about a week from now we can compare 2010's air temperature changes and see which year it resembles most. But everyone, feel free to compare and speculate. Here's my assist, you score the goal.