The reason that Korea has recorded no fine dust advisories nationwide in May

Korea has recorded zero fine dust advisories nationwide so far in May, a marked improvement from the 19 alert days issued between January and April.

According to the National Institute of Environmental Research (NIER), as of Friday and Saturday, fine dust and ultrafine dust levels across the country were rated “good” — the highest clean air category — with concentrations staying within 0 to 30 micrograms per cubic meter for fine dust and 0 to 15 for ultrafine dust. 

An advisory is triggered when hourly average concentrations exceed 150 micrograms per cubic meter for fine dust and 75 micrograms per cubic meter for ultrafine dust over two or more consecutive hours.

The improvement is largely attributed to a seasonal shift in wind direction.

From winter through early spring, the Korean Peninsula sits under the influence of the Siberian high-pressure system. Winds circulate clockwise around the high, creating airflow patterns that carry pollutants from China's high-emission areas — including Beijing, Tianjin and the province of Hebei — toward Korea.

NIER identifies two main inflow routes. 

In one, fine dust from northern China rides southwesterly winds toward northern Manchuria before being pushed southeast into the Korean Peninsula on northwesterly winds.

In the second, a cold Siberian high drifts south toward China and, as temperatures rise and the Siberian high transitions into a mobile one, carries Chinese fine dust eastward toward Korea on prevailing westerly winds.

Once over the peninsula, the incoming pollution mixes with domestically generated particulates and can stagnate from being blocked by a high-pressure system near Japan.

As summer approaches, however, this pattern gives way to the North Pacific high. 

Although winds still circulate clockwise, the high sits near Japan rather than over the continent, pushing southerly and southwesterly winds across Korea and reducing the likelihood of pollutant inflow from the northwest. NIER officials say the North Pacific high has been expanding earlier in the season in recent years, which has brought the cleaner wind pattern sooner.

Satellite imagery from Korea's Chollian-2B environmental satellite showed Chinese airspace appearing blue and yellow on Friday, indicating low fine dust concentrations, compared to deep red readings in early April.

Lee Jae-beom, the director of the Integrated Air Quality Forecasting Center at NIER, said rising temperatures are a key factor. 

In winter, cold air settles close to the ground, concentrating fine dust at altitudes of 600 to 700 meters (1,968.5 to 2,296.6 feet). 

“As temperatures climb, the same particles rise up to 1.5 kilometers [0.93 miles], dispersing more widely and lowering surface-level concentrations,” Lee said. “Increased vertical air mixing in warmer months also helps flush pollutants upward.”

Reduced emissions play a role as well. 

Heating demand falls sharply in spring, and cities in northern China, including Beijing, operate centrally controlled district heating only from mid-November to mid-March.

China's annual average fine dust levels have also been on a downward trend.

China's ministry of ecology and environment announced in February that the national annual average concentration of ultrafine dust stood at 28 micrograms per cubic meter in 2025, a 20 percent reduction over the 14th Five-Year Plan period from 2021 to 2025, attributed in part to cuts in coal-fired power generation.

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom. 

BY HEO JEONG-WON [seo.jieun1@joongang.co.kr]