This directory contains Level 3 (1.0 degree latitude/longitude globally gridded) 
Monthly MISR CTH-OD histogram data that has been stored in a CMOR-like format.

These data have been extracted from the operational MISR product which is stored
in HDF format. We URGE all users to please read the QUALITY_STATEMENT also
located in this directory.

There are two file types: clMISR and samplesMISR.  clMISR is the joint histogram
of cloud-top-height and cloud-optical depth.  samplesMISR is the total number
of samples in each lat/lon grid cell.   

The histograms are stored as relative frequencies, in percent. That is, 
  100 * (the counts in each category) divided by MISR_total_samples.    

Grid-cells with fewer than 10,000 samples have been set to a fill-value of 1e20 
in the clMISR dataset.   This threshold ensures that the histograms in each grid-cell
are not "noisy" as a result of having too few samples.  When aggregating data
on time scales which are greater than monthly, users should weight the data
according to the number of samples. 

The histograms contain one-additional row and columns called "No Retrieval" or "NR".   
This additional row/column provides a count of the number of pixels where the MISR 
cloud-mask indicated a cloud was present but the CTH or OD retrieval failed.  

Roj Marchand
rojmarch@u.washington.edu

Last updated: Feb. 2013