Characteristics of haze change in China since the twenty-first century

Abstract

Meteorological observation data from 843 national basic/base stations of the China were used to analyze the spatial and temporal distributions of haze in China. The area where there were more than 30 days of haze annually expanded gradually. The average number of haze days across China from 2001 to 2016 was 22.9d. The number of haze days increased gradually from 2001 to 2004 then declined slightly from 2004 to 2012. In 2013, the number of haze days increased to the highest level but then decreased through 2016. The annual number of haze episodes demonstrated a similar trend to the number of haze days. From 2014 to 2016, the cold air was weaker than in the past 30 years. At the same time, the number of breeze days increased and average wind speed decreased. The meteorological conditions were favorable for the formation of haze in China from 2014 to 2016. However, annual haze days, NO2 and SO2 from the OMI (Ozone Monitoring Instrument) data decreased in the three regions from 2014 to 2016, which implies that the emission control program conducted by the Chinese government was effective.