This summer, Korea is experiencing the hottest weather in 117 years. In contrast, San Francisco, USA, with a similar latitude, is facing the coldest summer in 60 years. "The extreme weather anomalies in the two regions may be related," weather experts say. Recently, a 'double high pressure system' has covered Korea while San Francisco is under a 'low pressure system.'
◇ July: San Francisco 15°C VS Seoul 38°C
"The coldest winter I ever experienced was San Francisco's summer." The Los Angeles Times reported on the 26th (local time), quoting the famous saying of American writer Mark Twain, asserting that "this is truly the case this year." It was an article reporting that San Francisco is experiencing its coldest summer in 60 years.
According to the National Weather Service (NWS), the average temperature in San Francisco in July has been recorded at 15.2°C. Even in mid-summer, it is the kind of weather where people can easily be seen wearing long sleeves and scarves. The last year when the temperatures were this low was 1982 for downtown and 1965 for the international airport.
In contrast, it is scorching in Seoul. At the Seoul Meteorological Observatory in Jongno-gu, Seoul, a temperature of 37.7°C was recorded on the 8th, setting a record for the highest temperature in 117 years for early July (1st to 10th). On the 27th, it reached 38.0°C, which is also a rare record that has occurred only 9 times in 117 years. Since modern weather observations began in 1907, records for the highest temperatures are being broken.
◇ "High and low pressure systems locked in a 'circumglobal teleconnection' pattern"
The scorching heat in Seoul this summer is attributed to the influence of a 'double high pressure system.' With the North Pacific high pressure system covering the airspace over the Korean Peninsula, the Tibetan high pressure system, which has expanded its influence from inland China, is trapping heat underneath. Additionally, in the lower atmosphere of the Korean Peninsula, warm and humid southeast winds are flowing in, and as these winds cross the Sobaek Mountains, the 'Föhn effect' causes the western areas, such as the capital region, to become particularly hot.
In contrast, a 'low pressure system' has lingered over San Francisco. Due to the warm high pressure system being shifted westward compared to normal, a low pressure system has settled over California, which has resulted in cloudy weather and lower temperatures. Furthermore, the unique geographical characteristics of the San Francisco Bay, where cold seawater rises to the surface and winds blow, have contributed to lowering the land temperatures.
Weather experts analyze that there may be an interrelationship between the phenomenon of distant regions, like Seoul and San Francisco, displaying 'extreme opposite' weather. Lee Myung-in, director of the Heatwave Research Center at the Ulsan National Institute of Science and Technology (UNIST), noted, "Since early July, a pattern known as 'circumglobal teleconnection' (CGT) has emerged, leading to stagnation in the airflow across the globe."
'Circumglobal teleconnection' refers to the phenomenon where weather or climate changes in one region of the Earth affect the climate in other regions located thousands of kilometers away. Due to the stagnation of airflows, high pressure can remain over some areas, causing extreme heat, while other specific areas may experience low pressure leading to continuous heavy rains and low temperatures.
Extreme heat phenomena are also occurring in Europe. Over the past weekend, temperatures in Turkey soared to 50.5°C, and Greece recorded 45.2°C. This region has been experiencing consecutive large wildfires. Even Switzerland, which typically enjoys milder summers, endured unprecedented heat with temperatures reaching the mid-to-late 30s from late June to early July, but recently, morning low temperatures dropped back down to 10°C to 14°C.