Abstract
Abstract. Although aggressive emission control strategies have been implemented recently in the Beijing–Tianjin–Hebei area (BTH), China, pervasive and persistent haze still frequently engulfs the region during wintertime. Afforestation in BTH, primarily concentrated in the Taihang and Yan Mountains, has constituted one of the controversial factors exacerbating the haze pollution due to its slowdown of the surface wind speed. We report here an increasing trend of forest cover in BTH during 2001–2013 based on long-term satellite measurements and the impact of the afforestation on the fine-particle (PM2.5) level. Simulations using the Weather Research and Forecast model with chemistry reveal that afforestation in BTH since 2001 has generally been deteriorating the haze pollution in BTH to some degree, enhancing PM2.5 concentrations by up to 6 % on average. Complete afforestation or deforestation in the Taihang and Yan Mountains would increase or decrease the PM2.5 level within 15 % in BTH. Our model results also suggest that implementing a large ventilation corridor system would not be effective or beneficial to mitigate the haze pollution in Beijing.
Highlights
Heavy haze with extremely high levels of fine particles (PM2.5), caused by rapid growth of industrialization, urbanization, and transportation, frequently covers northern China during wintertime, in the Beijing–Tianjin–Hebei area (BTH)
We report an analysis of long-term satellite measurements of the land cover change in BTH and quantitatively evaluate the impacts of the afforestation on the haze pollution in BTH using the WRF-CHEM model
In BTH, forests and croplands have increased by 7.2 % and 1.9 %, while shrublands and grasslands/savannas have decreased by 3.9 % and 5.1 %, respectively
Summary
Heavy haze with extremely high levels of fine particles (PM2.5), caused by rapid growth of industrialization, urbanization, and transportation, frequently covers northern China during wintertime, in the Beijing–Tianjin–Hebei area (BTH). There has been ongoing debate in China on whether the afforestation program contributes enough to mitigate the haze formation in BTH (China Forestry Network, 2016a, 2017). A remarkable forest growth has been reported in the northwest of BTH from 2000 to 2010 (Li et al, 2016), which has the potential to increase the surface roughness and decrease the surface wind speed (Wu et al, 2016a; Bichet et al, 2012), and could potentially aggravate the haze pollution. We report an analysis of long-term satellite measurements of the land cover change in BTH and quantitatively evaluate the impacts of the afforestation on the haze pollution in BTH using the WRF-CHEM model.
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