Call me cynical, but after spending decades watching property developers, the construction industry, business lobbyists, venal politicians and dodgy local government administrations make a mockery of federal and state laws meant to protect against environmental vandalism, planning decisions that place communities at risk and sub-standard dwelling design and construction, I have yet to see any indication that the NSW Perrottet Government or various local governments intend to do more than paper over the current and future flood risks within the est. 100km wide & 2,007km long coastal zone of New South Wales.
GRAPHIC: Fuller M. & O’Kane M. (29 July 2022) Report, 2022 Flood Inquiry Volume One: Summary.
Data used in the infographic on the prior page is from the following sources:
• Rainfall data. Bureau of Meteorology. (2022). Special Climate Statement 76 – Extreme rainfall and flooding in south-eastern Queensland and eastern NSW. Retrieved from: scs76.pdf (bom.gov.au)
• Roads data. Transport for NSW. (2022). Advice to the Inquiry provided and valid as of 21 July 2022.
• Agricultural data. Department of Primary Industries. (2022). Advice to the Inquiry provided and valid as of 4 July 2022.
• Unless specified above, data has been provided to the Inquiry from Resilience NSW and is valid as of 13 July 2022. This does not include Inquiry data.
Fuller M. & O’Kane M. (... by clarencegirl
The full report can be found at:
https://www.nsw.gov.au/sites/default/files/noindex/2022-08/VOLUME_TWO_Full%20report.pdf
BACKGROUND
A brief explanation of the processes involved in 2022 high rainfall events.
Australian Bureau of Meteorology (BOM), Special Climate Statement 76, 25 May 2022, excerpt:
The 2022 rainfall and flooding were the result of a blocking high pressure system over New Zealand, that assisted the formation of a series of slow-moving low pressure systems within a trough that fed a large volume of warm moist air from the Coral and Tasman seas into eastern Australia. The subsequent development of a series of deep low pressure systems delivered intense rain to east and south-east New South Wales. Following two years of La Niña conditions, the rain fell on catchments that were already wet so water storages and river levels were high and catchments quickly became saturated…..
BOM, Key climate drivers behind record rainfall in New South Wales, 5 July 2022, excerpt:
The Bureau's 2022 winter outlook showed above average rainfall over the coming months, particularly for most of eastern and northern Australia, due to warmer than usual waters around the continent and more moisture-filled air being directed into eastern Australia.
University of New South Wales, Newsroom, 8 March 2022:
At any one time, Earth’s atmosphere holds only about a week’s worth of rain. But rainfall and floods have devastated Australia’s eastern regions for weeks and more heavy rain is forecast. So where’s all this water coming from?
We recently investigated the physical processes driving rainfall in eastern Australia. By following moisture from the oceans to the land, we worked out exactly how three oceans feed water to the atmosphere, conspiring to deliver deluges of rain similar to what we’re seeing now.
Such research is important. A better understanding of how water moves through the atmosphere is vital to more accurately forecast severe weather and help communities prepare.
The task takes on greater urgency under climate change, when heavy rainfall and other weather extremes are expected to become more frequent and violent.
Big actors delivering rain
The past few months in eastern Australia have been very wet, including the rainiest November on record.
Then in February, heavy rain fell on already saturated catchments. In fact, parts of Australia received more than triple the rain expected at this time of year.
So what’s going on?
In the theatre that is Australia’s rainfall, there are some big actors – the so-called climate oscillations. They’re officially known as:
El Niño-Southern Oscillation (ENSO): this cycle comprises El Niño and its opposite, La Niña. ENSO involves temperature changes across the tropical Pacific Ocean, affecting weather patterns around the world
Southern Annular Mode (SAM): the north-south movement of strong westerly winds over the Southern Ocean
Indian Ocean Dipole (IOD): changes in ocean temperatures and winds across the tropical Indian Ocean.
Like swings in a character’s mood, each climate mode has positive, negative and neutral phases. Each affect Australia’s weather in different ways.
ENSO’s negative phase, La Niña, brings wetter conditions to eastern Australia. The IOD’s negative phase, and SAM’s positive phase, can also bring more rain.
Going back in time
We studied what happens to the moisture supplying eastern Australian rainfall when these climate drivers are in their wet and dry phases.
We used a sophisticated model to trace moisture backwards in time: from where it fell as rain, back through the atmosphere to where it evaporated from.
We did this for every wet winter and spring day between 1979 and 2013.
This research was part of a broader study into where Australia’s rain comes from, and what changes moisture supply during both drought and heavy rain.
We found most rain that falls on eastern Australia comes from moisture evaporated from a nearby ocean. Typically, rain in eastern Australia comes from the Coral and Tasman seas. This is depicted in the strong blue colours in the figure below.
But interestingly, some water comes from as far as the Southern and Indian oceans, and some originates from nearby land areas, such as forests, bare soils, lakes and rivers.
Natural processes can alter the typical supply of moisture to the atmosphere, causing either droughts or floods.
Read the full article here.
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