Why some snows are heavier

People commute to work in Jung-gu, Seoul on Thursday. (Yonhap)

Record amounts of heavy snow blanketed Seoul and its surrounding areas for a second consecutive day, causing tree branches to snap and roofs to collapse in areas hit hard by the snowstorm on Thursday.

In addition to the volume of snow, the Korea Meteorological Administration attributed the danger to its composition.

The snow that has fallen in greater Seoul over the past two days has been predominantly wet snow, significantly heavier than dry snow.

While dry snow weighs about 150 kilograms per cubic meter, wet snow can weigh as much as 300 kilograms per cubic meter.

Wet snow forms at relatively warmer temperatures, typically between minus 5 and 0 degrees Celsius, compared to the colder conditions of minus 20 to minus 10 degrees Celsius that produce dry snow.

On Wednesday, temperatures in greater Seoul ranged from minus 8.6 to 8 degrees Celsius.

The KMA also noted that unusually warm waters in the Yellow Sea have contributed to the snow’s density as well as volume.

Winter sea surface temperatures in the region have been 1 to 2 degrees Celsius higher than average, following a summer in which temperatures were 3 to 4 degrees Celsius above normal.

“When the difference between air and sea surface temperatures is more than 17 degrees, heavy snow tends to fall,” a KMA official said. “Currently, the temperature difference is between 25 and 28 degrees.”

Meanwhile, the KMA warned that falling temperatures on Thursday night could increase the risk of additional accidents due to the accumulated snow and ice.