Explorations: Changes in Australia

When looking at global albedo changes, I noticed something interesting about Australia in particular: in the period 2001-2021, non-cloud albedo increased in Australia. In most of the world, changes in albedo during this period are attributable primarily to changes in snow/ice coverage, and secondarily attributable to changes in aerosols. However, neither snow and ice nor aerosols explain the albedo changes in Australia.

The albedo changes in Australia are not large enough that they affect the global energy budget. However, as a matter of curiosity, I’ve plotted some available data regarding Australia in case this may be of interest.

Overall Changes

The map below shows changes in the local contribution to global non-cloud albedo, between the period 2001-2005 and the period 2017-2021. The local contribution to global albedo is [local upward SW radiation at TOA] / [global average downward SW radiation at TOA]. In comparison, local albedo would be [local upward SW radiation at TOA] / [local downward SW radiation at TOA].

What is plotted is albedo as viewed from TOA, so it could in principle include albedo from aerosols

The change in the aerosol contribution to global albedo is shown below. Note that the change in albedo due to change in aerosols is very small. The contours are more finely spaced in the map below than in the map above. If a similar contour spacing had been used, the map below would show no significant changes.

The map below shows changes in local surface albedo. The pattern is quite similar to the pattern for changes in non-cloud contributions to the global albedo, as had been shown above. Minor differences can be attributed to differences in measurement techniques and differences between the CERES EBAF and SYN1deg datasets. It appears that the albedo change in Australia was a change in surface albedo, not attributable to changes in atmospheric scattering.

The map below shows changes in emissivity. The same dataset (CERES SYN1deg ed. 4.1 Terra-Aqua) indicates that Australia was fairly unusual in experiencing such widespread (if small) emissivity changes.

The map below show changes in the amount of precipitable water measured in the atmosphere over the same period. The air over parts of Australia got quite a bit drier over the study period. However, from looking at other data, the amount of precipitable water in the air seems to have surprisingly little relationship to how much precipitation occurs.

Changes in cloud cover are shown below. On an annual basis, there was little change in cloud coverage. However, the seasonal charts in the next section indicate that cloud coverage changed seasonally.

The map below shows changes in the surface “skin temperature” as estimated in the CERES SYN1deg dataset. It shows significant warming in Central and Western Australia.

Below is a map of changes in snow/ice coverage. It’s apparent that this is not the explanation of surface albedo changes in Australia.

Seasonal Changes

Below, I offer some maps similar to those above, but split into data for two different halves of the year.

Other Data

The Australian Government Bureau of Meteorology has various historical data for this same period time period. Note that the natural seasons in Australia apparently run from October through April (“Northern Rainy Season”) and May through September (“Cool Season”). Contacts in Australia tell me there has been a lot of drought that led to loss of vegetation, which would presumably account for changes in albedo and emissivity.