I recently looked for trends in precipitation in New South Wales, searching for a regional rather than continental trend. There wasn’t much to find, no real evidence of change in the yearly average rainfall. But we can also look for trends on a seasonal rather than annual basis, and we can do so for all seven Australian states for which the BoM kindly provides precipitation data.
When we isolate seasons, we find some patterns strong enough to rise above the noise. For example, Victoria has been getting dryer during Autumn:
Meanwhile West Australia has been getting wetter during summer:
Using PCA (Principle Component Analysis), for all seasons the first PC turns out to be very close to the overall (continent-wide) average. The second PC highlights patterns of consistent differences between states. Just as an example, here it is for the Autumn season:
On the left are the loadings, showing that the time series pattern is much like the difference between Victoria+Tasmania(+some of New South Wales) minus West Australia+Northern Territories. On the right is the time series pattern with its evident recent drying.
Both the summer and autumn seasons show similar patterns, West Australia/Northern Territories contrasting with Victoria/Tasmania, and the way the two interact isolates the pattern we noted before: that the northwest has been getting wetter during summer while the southeast has been drying during autumn.
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