CWB Director Cheng Ming-dean said increasing desertification in northern mainland China is responsible for this phenomenon. "But the cold air mass, which is forecast to arrive March 24, may also bring rain that could wash away much of the sand."
Chen Jen-ping of National Taiwan University’s Department of Atmospheric Sciences said another sandstorm could follow the cold front March 26, but the situation remains unclear, so all of Taiwan should be prepared.
Over the past two days and nights 39 Environmental Protection Agency monitoring stations around the island have registered record-breaking particulate concentrations exceeding 1,000 micrograms per cubic meter per hour. As the high pressure front which brought the sandstorm moves away, conditions should improve March 23. However, there is still a high concentration of dust particles suspended in the air.
Air quality in the north gradually improved through the afternoon of March 22, while in the south from the evening of March 21 till the morning of March 22 air pollution was severe.
The Xinying monitoring station in Tainan County recorded a dust level of 1,230 micrograms per cubic meter per hour at 11 p.m. March 21, while the Shanhua station registered 1,116 micrograms just after midnight March 22, 12 times the normal reading and far exceeding the “hazardous” standard. At 2 a.m. March 22 the particulate concentration at the Nanzi station in Kaohsiung City topped out at 1,156 micrograms.
EPA data show that on the morning of March 22, 10 stations still were recording levels above 1,000 micrograms, but in the afternoon all stations around the island were under that figure. Chu Yu-chi, director of the EPA’s Department of Environmental Monitoring and Information Management, said air quality throughout Taiwan can be expected to gradually return to normal levels of 100 micrograms of suspended particulates March 23.
As to why the sandstorm is so severe this time, Cheng said normally before the air stream reaches Taiwan the upper and lower streams will split, thus reducing the amount of dust that invades the island, but in this case the air stream did not separate, and so brought tremendously high concentrations of sand. (THN)