January 2025 Wildfires in Los Angeles County
In January 2025, Los Angeles County experienced several significant wildfires
This month was a crucial month for the people of Los Angeles. Since January 7, 2025, a series of wildfires have affected several areas in Los Angeles, killing at least 28 people. Along the Pacific Coast, the Palisades fire has burned more than 23,400 acres, and the Eaton fire in the San Gabriel Mountains has burned more than 14,000 acres. Fires in Los Angeles have gotten bigger and bigger every year.
The rainy season on the West Coast typically occurs in winter, but in recent years, winters have brought little rainfall. Today, I’d like to explore the mechanisms behind this phenomenon.
Why is California receiving less rain? These events have been attributed to the meandering of the jet stream.
The jet stream refers to a high-altitude wind that blows from west to east around the Earth. It is driven by two factors: the temperature differences caused by colder conditions near the poles and warmer conditions near the equator, and the Earth's rotation. The jet stream is particularly prominent in mid-latitude regions (areas outside the poles and equator), where the temperature difference between the north and south is significant, and the rotational effect of the Earth is strong.
In the past, the jet stream flowed steadily, but now, with global warming, the temperature in the Arctic has risen, causing sea ice to melt, and its area to decrease each year. As a result, the temperature difference between the equator and the Arctic in the Northern Hemisphere has diminished. This has led to the jet stream meandering, which is linked to abnormal weather patterns.
Under normal conditions, the jet stream flows quickly and relatively straight between the warm southern air and the cold northern air, resulting in only minor meandering. However, as Arctic temperatures rise due to rapid global warming, the temperature difference between the Arctic and the equator narrows. Consequently, the jet stream slows down, making its flow unstable and more prone to significant meandering.
The jet stream typically carries moist air from the Pacific Ocean, forming rain clouds and bringing rain. However, this year, the jet stream has diverted rain to places like Washington and Canada, while California has received almost none.Typically, the rainfall from July to December is 94.4 mm, but recently it was only 0.6 mm!
Additionally, over the past few years, the Pacific Ocean's sea surface temperatures have risen due to global warming. This has strengthened the cold, dry Santa Ana winds that flow over the region, intensifying wildfires. These strong winds likely contributed to the rapid spread of wildfires after ignition. (The greater the temperature difference, the stronger the winds tend to blow.)
We are keeping those affected by the fires in our thoughts and wishing them all the best as they recover. And let’s think about what we can do to prevent disasters like this from happening again.