Wet weather

For those of you wondering about what caused the recent extreme rain event in Redlands and elsewhere in south east Queensland, there are three main factors.

Blocking high pressure system

A blocking high in the Tasman Sea (see figure below), stopping movement of weather systems (Highs and Lows) from west to east across the continent, was the first factor.

Usually, the weather systems take about 4 days to pass. But this system “stuck” for about a week, bringing rain via coastal and inland troughs (elongated low-pressure regions). Troughs are associated with high instability in the atmosphere, which brings rain and storms. Blocking patterns occur from time to time and can bring extreme wet, dry, hot or cold events or combinations.

Blocking high caused the recent wet weather
Source: Bureau of Meteorology

La Nina and the weather

The second factor is the influence of La Nina, with cooler water temperature conditions in the eastern tropical Pacific Ocean, bringing a wetter season to eastern Australia in particular. According to the Bureau of Meteorology, “La Niña events tend to begin in autumn, mature during winter, spring and early summer, then begin to decay in late summer. Events generally end in the autumn. The greatest impact normally occurs during the winter, spring and early summer period”.

Global heating impacts on our weather

The third factor is global heating (a far more accurate term than the neo-liberal introduced phrase, climate change).  This is causing the Rossby Wave Circulation to slow and meander more. This circulation occurs around mid-latitudes in both hemispheres and helps control the transfer of solar energy from the Equator (region of maximum solar gain) to the Poles. This helps make most of the planet liveable.  See this explanation and video example from space for the Northern Hemisphere’s Rossby Circulation.

Global heating is exacerbating the slowing and meandering of Rossby Waves and hence bringing more extreme blocking weather systems.

The major culprit is our excessive use of fossil fuels. The solutions can be found here:  www.drawdown.org  

Trevor Berrill

Trevor Berril is a Sustainable Energy Systems Consultant & Educator.
See his website https://trevolution.com.au/

More by Trevor Berrill

Weather the climate is changing in the Redlands

Redlands2030 – 25 March 2021

3 Comments

Dave, Mar 29, 2021

Trevor thanks for the insight, looking forward to learning more …its good to know we have a local who can put CC into context.

Trevor Berrill, Mar 29, 2021

Dear David
It appears from your comment that you didn’t read my post above. With regard to the reduction in energy demand and greenhouse gas emissions due to COVID19 impacts, the real data can be found here: https://www.iea.org/articles/global-energy-review-co2-emissions-in-2020
It says: “As primary energy demand dropped nearly 4% in 2020, global energy-related CO2 emissions fell by 5.8% according to the latest statistical data, the largest annual percentage decline since World War II. In absolute terms, the decline in emissions of almost 2 000 million tonnes of CO2 is without precedent in human history – broadly speaking, this is the equivalent of removing all of the European Union’s emissions from the global total. Demand for fossil fuels was hardest hit in 2020 – especially oil, which plunged 8.6%, and coal, which dropped by 4%. Oil’s annual decline was its largest ever, accounting for more than half of the drop in global emissions. Global emissions from oil use plummeted by well over 1 100 Mt CO2, down from around 11 400 Mt in 2019. The drop in road transport activity accounted for 50% of the decline in global oil demand, and the slump in the aviation sector for around 35%. Meanwhile, low-carbon fuels and technologies, in particular, solar PV and wind, reached their highest ever annual share of the global energy mix, increasing it by more than one percentage point to over 20%”
.

David j medland, Mar 29, 2021

So our consumption of fossil fuel (almost no aircraft over the last 12 months and road consumption drastically reduced ) we have not heard a word to say that their was any change for the better over that period ,but with a weather collision its all about global warming .Remember Tim Flanery “never rain again” YEA RIGHT,!

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