The data directory holds the ISCCP-D1 Three-hourly Cloud Products for the years 1983 (beginning July 1983), 1984, 1985, 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998 and 1999 in one directory [e.g., data/isccp_d1/1983/]. The data reside on the disk in HDF4 format. The data is provided in HDF by the Langley Atmospheric Sciences Data Centre. A wider set of ISCCP data is available from their webpage. The data in its raw format is stored on an equal area grid of 280km resolution. The sample read software provided converts this to an equal angle resolution of 2.5 degrees. Additionally, conversion tables included in the software are required to convert the data to real numbers from integer counts.
There is a small change in the data format and filenames from 1994 onwards. For the years 1983 to 1993 the file naming convention is d1_yyyymmdd (e.g. d1_19920501). For the years 1994 onwards the file naming convention becomes ISCCP.D1.1.GLOBAL.yyyy.mm.dd.9999.GPC.hdf(e.g. ISCCP.D1.1.GLOBAL.1922.214.171.12499.GPC.hdf). These later files no longer contain the read software and the ancillary data is included as a VDATA. The sample read files will read both file types.
Two hundred and two variables are available which include temporal and spatial means and standard deviations for cloud top pressure and temperature, cloud optical depth, and cloud water path. Optical depth, water path, cloud top pressure, cloud top temperature, and frequencies are available for low, middle, and high clouds as well as 15 different cloud types e.g. cumulus, cirrus etc. Variables derived from the TIROS Operational Vertical Sounder (TOVS) are precipitable water and atmospheric temperatures. Variables derived from visible wavelengths are available only during daylight hours. Each variable has values for the following GMT times of day: 00:00, 03:00, 06:00, 09:00, 12:00, 15:00, 18:00, 21:00.