Low-pressure Fangs Lurking Behind the Warm Winter--Anomalous Winds Blowing over the Japanese Archipelago in 2007

Low-pressure Fangs Lurking Behind the Warm Winter--Anomalous Winds Blowing over the Japanese Archipelago in 2007

In 2007, a shock was felt in the Japanese meteorological community. According to a report published by a research group at the University of Tokyo Graduate School, the "warm winter" over the Japanese archipelago is deeply related to an increase in "bomb cyclones," which develop very rapidly and have a different weather mechanism than before. This "bomb low" refers to an intense low-pressure system whose central pressure drops more than 10 hectopascals in 12 hours, and has become a frequent occurrence on the Pacific side of Japan during the winter season. In a normal winter, the dominant pressure pattern is a westerly high and easterly low caused by the Siberian High and Aleutian Low, but this pattern has been disrupted by the bomb low, and moist warm air has been covering the archipelago with increasing frequency. This unusual circulation has brought winters with little snow and mild cold days in various regions.

The year 2007, when this study was published, was a year in which the world shared an unprecedented sense of urgency about global warming: the Intergovernmental Panel on Climate Change (IPCC) and former U.S. Vice President Al Gore received the Nobel Peace Prize, and the documentary film "An Inconvenient Truth" brought the reality of climate change home to many people. The documentary film "An Inconvenient Truth" has brought the reality of climate change to many people's attention. In Japan, the government-led "Team Minus Six Percent" campaign was underway, and the effectiveness of the Kyoto Protocol was being questioned at home and abroad. In such an era, the study of the bomb cyclone attracted attention not as a mere weather anomaly, but as a terminal symptom of global climate change.

The researchers warn. Global warming is altering atmospheric circulation in the North Pacific Ocean, shaking the "cold structure" of winter to its very foundations. More frequent bomb storms will eliminate the dry, cold winter and increase the likelihood of moist rainfall and unseasonably high temperatures in the winter. This would not just be a "slightly warmer winter," but would have serious consequences for social and industrial activities. For example, ski resorts will experience a severe lack of snow, which will hurt the tourism industry. Also, the retail industry will be in a quandary as winter clothing will not sell well. In agriculture, the growth cycle of winter vegetables, which require low temperatures, will be disrupted, affecting quality and yields. These changes will alter winter living itself.

The importance of this study lies in the fact that it suggests a more fundamental change, an alteration of the climate structure, rather than just a transient anomaly in weather phenomena. The increase in the number of cyclone bombings is a clear indication of this, and a sign of a new normal in Japan's winters. In the face of the enormous force of global warming that lies behind this trend, meteorology was increasingly called upon to speak at the forefront of society.

The results of this research in 2007 were a pioneering wake-up call that foreshadowed the following decade. In fact, since the beginning of the 2000s, Japanese winters have repeatedly shown a marked warming trend, and extreme phenomena such as bomb cyclones, heavy rains, and gusty winds have become the norm. In other words, this study may have been an initial response to the "climatic anomaly" that had already begun, rather than a forecast for the future. The warm winter brought about by the bomb cyclone was a sign of climate change, a transformation under the guise of weather.