Uncovering the mystery of central Australia's drought: the multiple roles of geography, ocean currents and climate change

Hello everyone, I am the assistant of Australian Encyclopedia. Recently, some friends asked me aboutClimate characteristics and causes of central AustraliaNow I will summarize the relevant issues and hope it will be helpful to those who want to know more.

The vast red desert, sparse vegetation and extreme temperature differences in central Australia form one of the most unique arid landscapes on Earth. The average annual rainfall in this area of 1.3 million square kilometers is less than 250 mm, and in some areas it is even less than 150 mm. This article will provide you with an in-depth analysis of the formation mechanism of this "arid heart" from four dimensions: geographical structure, atmospheric circulation, ocean currents and human activities.

Key issues related to central Australia's climate

1. How does geographical location determine the fate of drought?

The Australian continent is located between 10° and 44° south latitude, and its central part is located in the core area of the subtropical high pressure belt. The Coriolis effect caused by the rotation of the earth makes the downward airflow prevail in this latitude belt, forming a stable "high pressure dome". Meteorological data shows that this area is controlled by the high pressure system for more than 200 days a year. The temperature rises and the humidity decreases during the air sinking process, making it difficult for clouds to form.

From the perspective of the continental outline, Australia is an oval that is wide from east to west and narrow from north to south, with the widest point reaching 4,000 kilometers. This terrain requires ocean water vapor to travel a long distance to reach the inland. Take the southeast trade wind as an example. When the moist air blows from the Pacific Ocean, it must first cross the Great Dividing Range with an average altitude of 1,000 meters, producing a significant foehn effect. Measured data show that the precipitation on the west side of the Great Dividing Range is 60%-80% less than that on the east side.

2. What role does the Western Australian cold front play?

The cold current system flowing along the west coast is an important factor in aggravating the drought. The surface water temperature of this Western Australian cold current originating from Antarctica is 5-8℃ lower than that of the sea areas at the same latitude. The evaporation of low-temperature seawater is reduced, resulting in a significant decrease in atmospheric humidity along the coast. Satellite observations show that the water vapor content above the cold current-affected area is more than 40% lower than that of the east coast.

More importantly, the cold current strengthens the formation of the coastal inversion layer. When cold seawater meets warm air, a temperature inversion layer (inversion layer) will form near the ground, just like a "thermal blanket" covering the atmosphere, inhibiting the development of convective clouds. Meteorological radar monitoring confirms that the frequency of cumulus clouds along the coast of Western Australia is 65% less than that on the east coast.

3. How does topography change rainfall distribution?

The average altitude of central and western Australia is only 200-300 meters, lacking high mountains to intercept water vapor. In contrast, Mount Kosciusko, the highest peak of the Great Dividing Range in the east, is 2,228 meters above sea level, completely intercepting Pacific water vapor. Orographic rainfall simulation experiments show that if the Great Dividing Range is removed, annual rainfall in the central region may increase by 300-400 mm.

The special basin topography exacerbates the drought cycle. The Great Artesian Basin covers an area of 1.75 million square kilometers, and its closed geological structure causes evaporation to exceed recharge. NASA satellite data shows that the amount of water lost through evaporation in this area each year is equivalent to 120 times the water storage capacity of Sydney Harbor.

4. What is climate change changing?

The latest CSIRO research shows that in the past 50 years, the number of extremely high temperature days in the central region has increased by 23%, the number of heavy rainfall events has decreased by 40%, but the intensity of short-term rainstorms has increased by 15%. This "drought-flood" alternation pattern is changing the fragile ecological balance. The 2022 Australian Bureau of Meteorology report pointed out that the climate zone in the central region is moving southward at a speed of 10 kilometers per year.

The impact of human activities cannot be ignored either. Overgrazing has led to a 34% decrease in vegetation coverage, and changes in surface albedo have exacerbated the heat island effect. Satellite thermal imaging shows that the daytime surface temperature in pasture areas is 6-8°C higher than that in natural vegetation areas.

Future climate change trends

According to the IPCC Sixth Assessment Report, by 2100, central Australia may experience:

• The annual average temperature rose by 2.4-4.5℃
• Dry season extended by 30-50 days
• Increased sandstorm frequency by 40%
• The extinction risk of endemic species has increased by 60%

The Australian government has launched the "Drought Adaptation 2030" plan, which includes underground aquifer management, drought-tolerant crop cultivation and ecological corridor construction. Among them, the new technology of using ancient groundwater recharge system can improve agricultural water efficiency by 70%.

Thank you for your reading. I hope this article can help you understandThe complex causes of central Australia's climateWhether you are planning an inland trip, conducting ecological research, or paying attention to climate change, it is crucial to understand the climate code of this red land. We will continue to update the latest research results in related fields, so stay tuned!