Figure 1.

Analyses of ambient temperature and rainfall at Darwin Airport (12°25′ S 130°52′ E), in the Australian ‘wet–dry tropics’, based on data from 1941 to 2004 (from the Australian Bureau of Meteorology). (a) Mean annual values for monthly air temperatures and precipitation. Maximum temperatures (thin solid line) are similar among months, minimum temperatures (thick solid line) fall mid-year and rainfall (thin broken line) is concentrated in a brief wet season; (b) monthly mean coefficients of variation from the overall (long-term) annual mean monthly value for each trait. Maximum temperatures (thin solid line) are less variable than are minimum temperatures (thick solid line). Variation in both temperature and rainfall levels is high during the dry season, but is low for all weather variables otherwise. (c) Degree of year-to-year variation in the deviation of these traits from the long-term average, to clarify the extent to which weather conditions are predictable from one year to the next. To do this, we plot the absolute value of the deviation from the long-term average for each variable for each month. Temperatures (solid lines) are predictable, but rainfall (broken line) is not.