Is there a database of airport ceilometer raw data? I am interested in obtaining raw ceilometer data, to test some cloud/aerosol layer identification algorithms.


Is this type of data freely available or will I need to ask for it directly from the airport?
Do airports keep an archive of raw data or simply of cloud heights as determined by manufacturers algorithm and provided in METAR reports?
OGIMET looks like it goes back to 2005. 

My favorite weather site Weather Underground has historical data.

It seems like you need to plug in dates one at a time but there are plenty of ways to skim a page and im sure you can ask them for a data dump if you know what you need.