Here we are going to compute the climatology for the month of July from the stack of 120 months (10 years) created previously. The procedure to compute climatologies for other months (or seasons) would be the same as outlined here, with only minor modifications.
When you open the stack SST monthly file besides the display of the first layer in file, there is also a smaller window to the right that looks like the above. This window let us select the layer to display (using the slider) and to select the processing method at (1). Here we are going to use the "Climatologies (months)".
(1) Since July is month seven in the years enter 7 (or 7:7) to tell the program to compute a climatology of this month (average of all Julies in the 10 years period). (2) is a parameter that selects the maximum gaps, in member of grid cells, that will be filled by interpolation. (3) is the output file name with this month climatology. If not provided, it will be asked by a separate window. (4) Selects the quality flag to apply to data (For MODIS '0' means retain only the best quality data). (5) Holds the name of the grid with the quality flags. We obtain one such grid by running the "Make a stack of L3 MODIS files" Lesson with a "sds2" parameter to select Qualities instead of SSTs. At the end, hit (5) and provide a file name to save the result.