Abstract
Abstract. Air pollution is substantially modulated by meteorological conditions, and especially their diurnal variations may play a key role in air quality evolution. However, the behaviors of temperature diurnal cycles along with the associated atmospheric condition and their effects on air quality in China remain poorly understood. Here, for the first time, we examine the diurnal cycles of day-to-day temperature change and reveal their impacts on winter air quality forecasting in mountain-basin areas. Three different diurnal cycles of the preceding day-to-day temperature change are identified and exhibit notably distinct effects on the day-to-day changes in atmospheric-dispersion conditions and air quality. The diurnal cycle with increasing temperature obviously enhances the atmospheric stability in the lower troposphere and suppresses the development of the planetary boundary layer, thus deteriorating the air quality on the following day. By contrast, the diurnal cycle with decreasing temperature in the morning is accompanied by a worse dispersion condition with more stable atmosphere stratification and weaker surface wind speed, thereby substantially worsening the air quality. Conversely, the diurnal cycle with decreasing temperature in the afternoon seems to improve air quality on the following day by enhancing the atmospheric-dispersion conditions on the following day. The findings reported here are critical to improve the understanding of air pollution in mountain-basin areas and exhibit promising potential for air quality forecasting.
Highlights
Air pollution is affected by anthropogenic emissions (Streets et al, 2001; Zhang et al, 2009; Kelly and Zhu, 2016) and controlled by atmospheric-dispersion conditions (Wei et al, 2011; Li et al, 2015; Ye et al, 2016; Zhang et al, 2020)
No noticeable decreases in wind speed appear in the Sichuan Basin (SCB) (Fig. 8g). These results suggest that the diurnal cycle with increasing temperature (Cluster 1) enhances atmospheric stability in the lower troposphere, which can weaken the vertical exchange of airflow and suppress the development of the planetary boundary layer (PBL), resulting in a small dispersion space of air pollutants and poor air quality in the SCB on the following day
The surface wind speed in the entire SCB is strengthened obviously, indicating that the horizontal dispersion capacity of air pollutants is improved. These results suggest that the diurnal cycle with decreasing temperature in the afternoon weakens atmospheric stability in the lower troposphere and creates good vertical mixing of airflow, which can promote the development of the PBL and surface wind speed, facilitating the improvement of air quality on the following day
Summary
Air pollution is affected by anthropogenic emissions (Streets et al, 2001; Zhang et al, 2009; Kelly and Zhu, 2016) and controlled by atmospheric-dispersion conditions (Wei et al, 2011; Li et al, 2015; Ye et al, 2016; Zhang et al, 2020). Stagnant meteorological conditions significantly contribute to the formation and maintenance of heavy air pollution as they play important roles in regulating the increment of air pollutant concentrations (Deng et al, 2014; Bei et al, 2016; Zhang et al, 2016; Wang et al, 2018). D. Kong et al.: Diurnal cycles of temperature changes and their effects on air quality lutions of large-scale synoptic systems can lead to the improvement or deterioration of air quality (Yarnal, 1993; Miao et al, 2017; Ning et al, 2019, 2020; Dong et al, 2020). These factors highlight the significance of further revealing the physical mechanism of atmospheric-dispersion evolutions
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