For information about the datasets you can read a NOAA technical report ftp://ftp.ncdc.noaa.gov/pub/data/noaa/ish-tech-report.pdf
This contains ISH/ISD data in directories by year. Please note that ISH and ISD refer to
the same data--Integrated Surface Data, sometimes called Integrated Surface Hourly.
The filenames correspond with the station numbers listed in the ish-history.txt file described below -- eg, 723150-03812-2006 corresponds with USAF number 723150 and WBAN number 03812.