Thunderstorms are more common in the southern hemisphere than in the northern hemisphere. Although the reasons for this phenomenon have puzzled scientists for years, only recently a team from the University of Chicago decided to find out why this is happening. As the researchers showed in their analyses, two important factors have an impact on the increased number of cases of severe weather.
Researchers from the University of Chicago have been able to explain what contributes to the more frequent thunderstorms in the southern hemisphere. Climate scientists led by Tiffany Shaw, thanks to the analysis of satellite data, calculated that violent events occur there 24 percent more often. However, it was not clear what was behind it.
Research by scientists. “You can’t put the earth in a jar”
Scientists from Chicago have noticed that the southern hemisphere is not one of the most favorable places to study the weather, because it is mostly covered with water. Meanwhile, most of the methods are based on analyzes conducted from land. However, with the increasing number of satellite studies conducted since the 1980s, researchers have had the opportunity to see how the two hemispheres differ in terms of weather.
Shaw and her colleagues Osamu Miyawaki of the US National Center for Atmospheric Research and Aaron Donohoe of the University of Washington made some hypotheses from their own and previous research, but needed more data. This meant further observations, hypotheses and simulations of climate change on our planet.
“You can’t put the Earth in a jar, so instead we used climate models built on the laws of physics and conducted experiments to test our hypotheses,” Shaw said. She added that after using the models, scientists removed individual variables and determined the impact of their absence on the frequency of storms.
Causes and past
The first factor studied was topography. The researchers explained their decision by the fact that large mountain ranges disturb the airflow, so there is a chance to limit storms where they are located. Comparing both hemispheres, there are more bands in the north of our planet. However, when the researchers “flattened” all the mountains on Earth in the models, the difference between the number of storms in both hemispheres significantly blurred.
The second significant variable was air circulation. Water moves around the globe like a slow but strong conveyor belt. The movement of water causes a difference in energy reserve between the two hemispheres. When scientists tried to eliminate this variable as well, they also saw that the storm’s disparity decreased.
Once they knew what made storms more frequent, they set out to study how the variation in both hemispheres had changed in the past. Analyzing data from the last decades, they found that this surprising asymmetry began to increase rapidly from the 1980s. This means that the southern hemisphere becomes even more prone to frequent storms. According to scientists, this is related to changes in the ocean. Similar trends are observed in the northern hemisphere, but their consequences are offset by the absorption of sunlight due to the loss of sea ice and snow.
The scientists compared their reports with reports from the Intergovernmental Panel on Climate Change (IPCC). They turned out to show the same results.
A young field of science
Some may wonder why only now scientists have become interested in the reasons for the disproportion in the number of storms in both hemispheres. As Shaw explained, the physics of weather and climate is relatively young compared to other fields of science. The first models of this specialization began to be created only after World War II.
Understanding these climate mechanisms and how they respond to human activities is crucial to anticipating and understanding what will happen when dangerous processes accelerate even further.
– Thanks to our analyses, we increase confidence in the forecasts of climate change. Thus, we help society better prepare for them. One of the main motives of my research is to understand whether models already predict information correctly so that I can trust them to predict the future. The stakes are high and it’s important to get an honest answer, Shaw concluded.
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