Welcome to the Raring Ringtail Alpha 2 release, which will in time become the 13.04 release.
This alpha features images for Kubuntu and Ubuntu Cloud.
At the end of the 12.10 development cycle, the Ubuntu flavour decided that it would reduce the number of milestone images going forward and the focus would concentrate on daily quality and fortnightly testing rounds known as cadence testing. Based on that change, the Ubuntu product itself will not have an Alpha 2 release. Its first milestone release will be the FinalBetaRelease on the 28th of March 2013. Other Ubuntu flavours have the option to release using the usual milestone schedule.