Spatiotemporal variability of surface extinction coefficient based on two-year hourly visibility data in mainland China
2019
Abstract
Visibilityis an important indicator for weather and air quality.
Historical subjective
visibilityobservations suffer from large uncertainty. Based on hourly instrumental
visibilitydata at 2356 meteorological stations during 2016–2017 in
mainland China, this study presents a closer look at the spatiotemporal variability of
visibility-derived surface extinction coefficient (σe). The data reveal that the regional
hazeis concentrated over North China Plain, the Sichuan Basin and Central China. Seasonal variations of σe in different regions are similar, although their seasonal variation amplitudes show subtle spatial dependence. σe generally decreases from January to April or May, then remains relatively lower values until August and finally starts to increase gradually until December. The largest seasonal variation is found in Xinjiang Autonomous region where the regional mean σe ranges from 0.55 km−1 in January (maxima) to 0.12 km−1 in June (minima). Winter
hazeis often found at
urban agglomerationsin Northeast China. Pronounced diurnal variation of σe is evident, especially in winter and in northern China. Peak values are generally observed between 7:00 and 9:00 a.m. and they appear later in winter relative to summer. Lower values are generally found between 13:00 and 15:00 p.m. A large-spread of regional aerosol pollution with rapid evolution in North China Plain is well captured by the
visibilitynetwork. Automatic
visibilitynetwork is a great supplement for air quality monitoring network. Much attention should be paid to its great potential in air quality study.
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