Yellow dust expected to hit by end of week

Korea is expected to be hit by a strong torrent of yellow dust, another unwelcome guest from China following severe pollution that blanketed the peninsula over the winter, according to a statement by Kweather, a weather information service in Korea.

The weather service said that the yellow dust, slated to hit the country on Friday, is anticipated to be so strong that the weather authority may have to issue a special nationwide warning.

Air pollution, or particle pollution, is produced when moisture in the air is combined with fine-particle matter. Particles less than 10 micrometers in diameter - known as PM-10, or coarse particles - are small enough to be inhaled into the lungs.

A special warning is announced when the concentration of PM-10 measures more than 400 micrograms per cubic meter for more than two hours. Such a warning was not issued in 2012 or 2013.

Yellow dust differs in that it is a seasonal phenomenon that hits the Korean Peninsula in the spring months. Dense clouds of dust and soil particles kicked up in sandstorms in deserts in Mongolia and northern China make their way on eastern-moving winds across East Asia to Korea.

Kweather predicts that a low pressure current passing through the Gobi Desert and Inner Mongolia will combine with an upward-moving current, and will arouse a sandstorm of yellow dust today and tomorrow. Those dust clouds are expected to move through northeastern China and flow into the Korean Peninsula on Thursday or Friday.

Based on that anticipation, the weather service forecast that the hwangsa, or yellow dust, will hit the west coast on Thursday in the afternoon and extend across the rest of the nation by the morning on Friday.

“Yellow dust is highly likely to influence the Korean Peninsula because we are expecting northerly or northwesterly winds, given the pressure currents around the peninsula,” said Ban Gi-seong, head of the Kweather forecast center.

Yellow dust tends to originate in relatively drier climates where there is a lack of precipitation. The average rainfall in March in Inner Mongolia, for instance, is about 0.5 millimeters - or nearly 4.6 millimeters below the annual mean.

Currently, 90 out of 119 weather observation stations in the region are recording the worst drought in 55 years, providing a convincing basis for Kweather’s yellow dust prediction.

However, the National Institute of Meteorological Research, the official yellow dust monitoring body, remained cautious despite the forecast.

“A low pressure current is passing through areas with yellow dust, but we still need to see how strong the ascending current will be, and forecast models in and outside of Korea have not detected any signals [of yellow dust origination],” said Lim Eun-ha, the head of yellow dust research. “But if other weather conditions stay the same, it is true that sandstorms are more likely to arise when those regions are drier.”

Meanwhile, the Korea Centers for Disease Control and Prevention yesterday announced guidelines for sanitation and health during the yellow dust season.

Those with respiratory problems and the old and infirm are particularly vulnerable to yellow dust, it said, and even healthy people may suffer from eye and skin problems as a result.

The authority advised people to stay inside as much as possible. It also said they should keep windows closed, maintain an indoor humidity level between 40 and 50 percent, and drink plenty of water.

BY KIM HAN-BYUL AND JANG JOO-YOUNG [bongmoon@joongang.co.kr]