SEOUL — As South Korea enters the peak period for yellow dust, many weather experts say they don’t expect dust concentrations to be heavy this season. “The seasons vary from year to year, and it’s hard to determine if this season is going to be worse than the previous one or not,” said Lt. Matthew Silver, chief of operations for the 607th Weather Squadron. “It’s kind of like the accuracy that you’d have with a farmer’s almanac.”

Also called Asian dust, the dust consists of particles that blow across the Korean peninsula from China and Mongolia and may include concentrations of heavy metals. High dust levels can leave a yellowish haze in the atmosphere and cause health problems for among “high risk” segments of the population, particularly among the young, the elderly and those with chronic respiratory or cardiac illnesses.

The yellow dust season runs from March to June, with the heaviest dust concentrations typically coming in late April and early May.

So far, this year’s yellow dust season has been relatively light, with only two days of moderate dust levels. Concentrations reached just below 600 micrograms per cubic meter March 19 and April 9, Silver said.

The Korea Meteorological Administration issues advisories when dust concentrations rise above 400 micrograms per cubic meter for more than two hours, and warnings are issued when dust levels exceed 800 micrograms for more than two hours.

People in the high risk category should avoid or minimize all outdoor activity when dust levels reach 400 micrograms, according to information from the 65th Medical Brigade posted on U.S. Forces Korea’s website. All outdoor activities should be canceled when dust levels reach 800 micrograms, it said.

A spokesman for the National Institute of Meteorological Research in Seoul said this year’s yellow dust season will likely be similar to previous years. A KMA spokesman said concentrations of yellow dust may be lower than last year because the Gobi Desert is unusually dry.

South Korea experienced a rare November yellow dust storm last year, when levels rose to 1,200 micrograms one day and visibility decreased to about one mile, Silver said.

But yellow dust is rare outside the typical spring dust season. During the summer, winds typically come from the south and bring heavy monsoon rains, instead of from the northwest as they do during the spring. And during the winter, the Northern Mongolian region where yellow dust originates is covered with ice, “so there’s no dust to be lifted,” Silver said.

Yellow dust reached only trace levels across South Korea on Friday afternoon, according to USFK.

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