Zhicong Yin

Climatic change features of fog and haze in winter over North China and Huang-Huai Area

This paper revealed the climatic change characteristics of fog and haze of different levels over North China and Huang-Huai area (NCHH). It was found that the haze-prone period has changed from winter into a whole year, and the haze days (HD) in winter have increased significantly. The foggy days (FD) are half of HD. There are little difference on the number of days and trends of fog at various levels. The HD and FD show no obvious positive correlation until the 1980s. Fog has larger spatial scale, showing more in the south than in the north. Haze occurs mainly around large cities with a discrete distribution. In the background of weakened East Asian Winter Monsoon (EAWM) and sufficient particulate matter, the negative correlation between haze and wind speed is weakened, but the positive correlation between haze and moisture conditions (precipitation and humidity) is significantly strengthened. In recent years, small wind and variability appear frequently. Meanwhile, as the stable source and strong moisture absorption of the aerosol particles, the moisture condition becomes one key control factor in the haze, especially wet haze with less visibility. In contrast, the FD presents a stable positive correlation with precipitation and relative humidity, but has no obvious negative correlation with wind speed.

The Relationship between the Anticyclonic Anomalies in Northeast Asia and Severe Haze in the Beijing–Tianjin–Hebei Region

Haze pollution in the Beijing-Tianjin-Hebei (BTH) region has become increasingly more severe and persistent in recent years. To better understand the formation of severe haze and its relationship with anticyclonic anomalies over Northeast Asia (AANA), this research focused on severe haze over the BTH region occurring in December during 2014-2016 and examined the impacts of the AANA. The results indicated that local meteorological conditions were conductive to severe haze (such as weaker surface wind, stronger temperature inversion, lower boundary layer and higher relative humidity) and were all closely related to the AANA. During severe haze episodes, the AANA remained strong in the mid-upper troposphere, which caused anomalous southerly wind. From the horizontal direction, strong southeasterly wind promoted the accumulation of pollutants and moisture while generating temperature inversion layer. The AANA also induced anomalous ascending motion over the BTH region, which broke the local meridional circulation. This restricted clean air from sinking to the surface and directly led to severe haze. The downward transportation of westerly momentum was also restrained, resulting in weaker surface wind and shallower boundary layer. The indirect zonal circulation between the BTH region and western Pacific triggered by the AANA provided a stable source of moisture to the BTH region, which strengthened the development of severe haze by promoting the growth of fine particles and weakening turbulence. The advance and retreat of the AANA were corresponded with the emergence and dissipation of severe haze, illustrating that the AANA could be an effective forecast indicator for air quality.

Statistical Prediction of Winter Haze Days in the North China Plain Using the Generalized Additive Model

AbstractWinter (December–February) haze days in the North China Plain (WHDNCP) have recently dramatically increased. In addition to human activities, climate change and variability also contributed to the severe situation and supported the possibility of seasonal predictions. In this study, using the generalized additive model (GAM), the sea surface temperature around the Alaska Gulf and sea ice area of the Beaufort Sea were selected as the predictors to establish a statistical prediction model (SPM). The difference between the current and previous year of WHDNCP (WDY) was predicted first and was then added to the observation of the previous year to obtain the final predicted WHDNCP. For WDY prediction, the root-mean-square error of the SPM using GAM was 3.01 days. In addition to the annual variation, the tropospheric biennial oscillation features and the dramatically increasing trend after 2010 were both captured successfully. Furthermore, for the final predicted WHDNCP anomalies, the long-term trend and...