Figure 4: (b) The geographical distribution of the difference in the probability of cirrus occurring in the four boreal winters. Winter 1990-91 minus winter 1989-90 is the upper left panel, winter 1991-92 minus 1990-91 is the upper right panel and winter 1992-93 minus 1991-92 is the lower left panel. Boreal winter includes the months of December, January, and February.

Color versions of the upper left panel and upper right panel are available.