These diagrams show the percentage frequency of occurrence of any brightness temperatures lower than a 230 K threshold within the plotted 1x1 deg boxes.

The method of calculation is as follows:

  a)For each year, all the available images in January within the specified three-hour time period were collected.

  b)For each 1x1 deg box, we calculated the percentage of the available images where at least 1 pixel had a 12-micron brightness temperature less than 230 K.

  c) For each 3-hour bin, we averaged the individual monthly percentages in the four-year period together.

Note, this is NOT simply the percentage of pixels less than 230K. Essentially, the quantity plotted is the likelihood that you will find a cloud that is colder than 230 K somewhere in a given 1x1 deg grid box at some time during the specified 3-hour period.