Air quality index gets new hourly updates

A new air-quality measure that provides hourly updates will be introduced today, the Shanghai Environmental Protection Bureau said.

The index will include hourly updates for all major pollutants, including PM2.5 and PM10, though the original air quality index (AQI) will still be used for forecasting and as the yardstick for the activation of pollution alarms, the bureau said.

Readings for both measures will be available via the Shanghai Environmental Monitoring Center’s website (www.semc.gov.cn/aqi) and its smartphone app, and will be included in TV news broadcasts and on social media, officials said.

“The current AQI provides a useful guide to air quality and is in line with the national standard,” said Fu Qingyan, chief engineer at the Shanghai Environmental Monitoring Center.

“But when conditions change it can become quickly outdated, which is where the new index is better.”

The current AQI is based on the levels of six pollutants: PM2.5, PM10, sulfur dioxide, nitrogen dioxide, ozone and carbon monoxide. While it is reported hourly, only four of the measures are actually updated hourly. The measures for PM2.5 and PM10 are given as an average over the previous 24 hours.

Increased accuracy

“In stable weather and air quality conditions, the real-time air quality index and the standard AQI will not differ too much,” said Luo Hailin, deputy chief engineer at the monitoring center.

“But in changeable conditions, the concentration of tiny particles can fluctuate significantly in a very short time, and it is then that the new measure will be more accurate,” he said.

Despite the introduction of the new measure, the original index will be used as a base for air quality alarms.

Under the new system, the lowest blue alarm will be issued when the AQI is forecast to be between 201 and 300 for the coming 24 hours. If the reading is expected to last for 48 hours, the alarm will be raised to yellow.

An orange alarm will be issued when the AQI is predicted to be between 301 and 450 over the next 24 hours, and the top-tier red alarm is triggered when the index is forecast to surpass 450.