Input Files: All five channels of the AVHRR are required, as are images of solar zenith angle, sensor scan or zenith angle, and sun-sensor azimuth angle. Also needed are latitude/longitude images and a land mask. Processing can only be done for NOAA polar orbiters that have AVHRR channel 5: NOAA 7, 9, 11, 12, and 14. The input files need to be in a specific format; see the User's Guide.
Memory: The amount of memory (bytes) needed is approximately:
[(ncols x nrows x 4 x 34) +
(npcols x nprows x nlevs x 4 x 3.5)]
/ 1024^2 + 2
where ncols and nrows are the numbers of columns and rows in the image, npcols and nprows are the numbers of columns and rows in the profiles image, and nlevs is the maximum number of levels in the profiles. These requirements are for single-image cloud masking. For time series masking add
{[ncols x nrows x 4 x (ndays+1) x 7.5] +
(ncols x nrows x 4 x 6)} / 1024^2
For example, given a 512 x 512 pixel image and an 8 x 8 cell profile image with 15 levels, about 36 MB of memory are needed if single-image cloud masking is employed. For time series masking using 5-day statistics add 51 MB for a total of 87 MB. If clear sky compositing is done, add
(ncols x nrows x 4 x 25 + ncols x nrows x 10)/1024^2 MB.
e.g., 27.5 MB for a 512 x 512 pixel image.
Clearly, times series masking with images larger than 512 x 512 pixels will require more memory than many workstations have. However, time series cloud masking can be run alone and then the resulting cloud masks can be read in when other parameters (surface and cloud properties and radiative fluxes) are to be computed. In that case the memory requirements would be the same as for single-image masking.
Other: Temperature and humidity profiles are required for the computation of cloud top pressure and surface radiative fluxes.