Travel restriction and less human mobility during the COVID-19 lockdown around the world have resulted in a lower emissions scenario around the world. Most of the Hong Kong citizens have also mentioned blue skies are more common this year.

There is no strong evidence that the short-term impacts of COVID-19 lockdown have a correlation of more days of blue skies in Hong Kong. But one thing for sure, everyone enjoys breathing fresh and healthy air. The clean blue skies make us feel happier during the time full of uncertainties and chaos.

It is interesting to compare the number of Clear Days in Hong Kong over the past few years:

Clear Days in Hong Kong 2016-2020

Number of Clear Days in each month

Here the “Clear Day” is defined by the Hedley Environmental Index (HEI). It is the day all five major air pollutants (Fine suspended particulates, Respirable suspended particulates, Sulphur dioxide, Nitrogen dioxide and Ozone) at all 13 urban rooftop monitoring stations complied with the short-term WHOAQG.

The finding shows that we experienced a long-term period the city’s air quality level did not exceed the safety recommendation set by WHO from 25th May to 20th August. A total of 88 days, and consecutively, we were breathing the air that was fresh and healthy for everyone this summer.

During the COVID-19 related lockdowns in many cities around the world, researchers detected a sharp decline in air pollutant concentrations. The most obvious change was the significant decreases in nitrogen oxides (NOx) over China, South Korea and European countries earlier this year because of reduction in road traffic, travel ban and shutting down of industrial activities.

The Himalayas were visible again this year, while people in India could see the mountains for the first time in almost 30 years. Kenyans reported seeing the jagged peaks of Mount Kenya from behind Nairobi’s skyscrapers and NASA satellite data showed a drop in pollution over the highways spanning the United States’ northeast corridor.

If the number of clear days is going to be more than 183 days in Hong Kong, it means we have breathed healthy air more than half a year, breaking a new record over the past few years.

It seems the COVID-19 lockdowns have given people a glimpse of a clean air future. The lockdown-like intervention and measures can be applied in the coming decades to combat air pollution. It is all about stringent legislation, behaviour change and public participation on pollution control.

Story posted on
8th Sep, 2020


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