From Thursday to Monday, there were up to 300 and in some places even just over 400 millimeters, especially in parts of Lower Austria, Geosphere Austria reported on Wednesday. Heavy rain has become more frequent and intense in many regions of Austria in recent decades, it was emphasized. “An analysis based on observation data shows that the number of days with a lot of precipitation has increased in summer and autumn and the days with little precipitation are becoming rarer. Specifically, for example, the number of days with extreme rain has increased by 30 percent in summer and 40 percent in autumn since the 1960s,” explained Marc Olefs, head of the climate research department at Geosphere Austria.
There have also been significant changes in precipitation events lasting several days in recent decades. A comparison of maximum five-day precipitation totals in the period 1991 to 2020 with those in the period 1961 to 1990 shows a statistically significant increase of 19 percent in Lower Austria and 20 percent in Vienna. The largest five-day events in these federal states now bring around 20 percent more rain and snow than before.
Polar cold air meets warm air in the south
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The large amounts of rain around last weekend were caused by a Vb weather situation (pronounced “five B”). In a Vb weather situation, a low pressure area moves from the western Mediterranean across Italy, Austria and Hungary to Poland. These low pressure areas are formed when cold polar air flows from the north over the Alps and meets the warm air in southern Europe.
“Vb weather conditions are comparatively rare, but usually bring large amounts of precipitation,” explained Olefs, “in recent decades only five percent of the low pressure areas in Austria and the surrounding area were Vb weather conditions. But they were responsible for 45 percent of the large-scale extreme precipitation events in Austria and the Czech Republic, for example also for the floods in 2013 and 2002.”
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In recent decades, there has been no clear trend towards more or fewer Vb weather conditions, but they have become more intense. The individual events therefore bring more precipitation. “The intensification of Vb weather conditions could continue due to global warming,” stressed Olefs, “to put it simply, this depends on two factors. Firstly, the warmer the air, the more water vapor it can absorb and the more rain is then possible. For every degree of warming, saturated air can absorb seven percent more water vapor.”
The warmer a sea, the more evaporation potential
“Secondly, global warming is also making the oceans warmer. The warmer the ocean is, the more potential there is for evaporation. Another research question that has not yet been fully answered is whether such Vb weather conditions move more slowly due to global warming. This is an important question, because the longer a low-pressure area stays over a region, the more rain accumulates there,” said Olefs.
In order to investigate the reasons for the extremely large amounts of rain in recent days, studies will be carried out in the coming weeks and months in cooperation between Geosphere Austria and other European organizations. In the case of the Vb low-pressure area, for example, the focus is on “which regions and to what extent the moisture came, what influence the surface temperature of the seas had on this, how the general weather situation affected the speed and path of the low-pressure area and to what extent man-made climate change has exacerbated such an event,” explained Olefs.
ePaper
– How has climate change impacted the frequency and intensity of heavy rainfall in Austria?
Heavy Rainfall in Austria: Climate Change Blamed for Increased Frequency and Intensity
Austria has been experiencing heavy rainfall in recent decades, with a significant increase in frequency and intensity of precipitation events. According to Geosphere Austria, the country witnessed up to 300 millimeters of rainfall in some areas, and in some cases, even over 400 millimeters, especially in parts of Lower Austria, from Thursday to Monday. This extreme weather phenomenon has become more frequent and intense, prompting concerns about the role of climate change.
Increased Frequency of Heavy Rainfall
An analysis of observation data reveals that the number of days with heavy precipitation has increased in summer and autumn, while days with little precipitation are becoming rarer. Specifically, the number of days with extreme rain has increased by 30 percent in summer and 40 percent in autumn since the 1960s. This trend is evident in the significant changes observed in precipitation events lasting several days in recent decades.
Vb Weather Situation: A Rare but Potent Cause of Heavy Rainfall
The recent heavy rainfall around last weekend was caused by a Vb weather situation, a rare phenomenon that occurs when cold polar air flows from the north over the Alps and meets warm air in southern Europe. This clash of air masses leads to the formation of low-pressure areas that bring large amounts of precipitation. Vb weather conditions are responsible for a significant proportion of extreme precipitation events in Austria and the surrounding region.
Climate Change: The Primary Driver of Heavy Rainfall
The increasing frequency and intensity of heavy rainfall events in Austria are attributed to climate change. As the planet warms, the atmosphere’s capacity to hold moisture increases, leading to more intense precipitation events. The analysis of observation data and climate models suggests that human-induced climate change is the primary driver of this trend.
Consequences of Heavy Rainfall
The consequences of heavy rainfall can be devastating, leading to flash flooding, landslides, and property damage. The 2013 and 2002 floods in Austria are examples of the destruction caused by extreme precipitation events. It is essential to understand the causes and consequences of heavy rainfall to develop effective strategies for mitigating its impacts.
Conclusion
The recent heavy rainfall in Austria is a stark reminder of the increasing frequency and intensity of precipitation events in the region. Climate change is the primary driver of this trend, and it is essential to take immediate action to reduce greenhouse gas emissions and adapt to the changing climate. By understanding the causes and consequences of heavy rainfall, we can develop effective strategies to mitigate its impacts and ensure a safer and more sustainable future.
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