This data comes from the ASA 2007 data expo,
http://stat-computing.org/dataexpo/2006/. The data
are geographic and atmospheric measures on a very coarse 24
by 24 grid covering Central America. The variables are:
temperature (surface and air), ozone, air pressure, and
cloud cover (low, mid, and high). All variables are monthly
averages, with observations for Jan 1995 to Dec 2000. These
data were obtained from the NASA Langley Research Center
Atmospheric Sciences Data Center (with permission; see
important copyright terms below).