Find in Library

The study of the characteristics and variations of cloud condensation nuclei (CCN) plays an important role in understanding the effects of aerosol–cloud interactions. This paper selected observation data in a city region of Shijiazhuang in North China from 2005 to 2007, along with the corresponding MERRA-2 and ERA5 data, to analyze the characteristics of CCN, sort the factors affecting the diurnal variation of CCN number concentration (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi mathvariant="normal">N</mi><mrow><mi>CCN</mi></mrow></msub></mrow></semantics></math></inline-formula>) according to their importance, and build the relationship between <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi mathvariant="normal">N</mi><mrow><mi>CCN</mi></mrow></msub></mrow></semantics></math></inline-formula> and supersaturation (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>SS</mi></mrow></semantics></math></inline-formula>) in the heavily polluted region. The results show that there was a bimodal distribution of a daily time series for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi mathvariant="normal">N</mi><mrow><mi>CCN</mi></mrow></msub></mrow></semantics></math></inline-formula> in Shijiazhuang, China. By calculating the correlation between CCN and pollutants observed in winter 2007, we identified that the dominant factor for peaks of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi mathvariant="normal">N</mi><mrow><mi>CCN</mi></mrow></msub></mrow></semantics></math></inline-formula> is <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>SO</mi></mrow><mn>2</mn></msub></mrow></semantics></math></inline-formula> in the morning but <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mrow><mi>NO</mi></mrow><mn>2</mn></msub></mrow></semantics></math></inline-formula> in the evening. We also ranked the factors affecting the diurnal variation of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi mathvariant="normal">N</mi><mrow><mi>CCN</mi></mrow></msub></mrow></semantics></math></inline-formula> by using observation and reanalysis data and found that the concentration of pollutants is the greatest impact factor in summer, but the atmospheric stability is the greatest factor in winter. Finally, we determined the relationship between <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi mathvariant="normal">N</mi><mrow><mi>CCN</mi></mrow></msub></mrow></semantics></math></inline-formula> and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>SS</mi></mrow></semantics></math></inline-formula> according to the Twomey formula (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi mathvariant="normal">N</mi><mrow><mi>CCN</mi></mrow></msub><mo>=</mo><msup><mrow><mi>cSS</mi></mrow><mi mathvariant="normal">k</mi></msup></mrow></semantics></math></inline-formula>) and found there was a reasonable value range (i.e., 0.5~0.7) for the parameter <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="normal">k</mi></semantics></math></inline-formula> in East and North China. Specifically, it is more reasonable for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi mathvariant="normal">k</mi></semantics></math></inline-formula> to be 0.5 in summer and 0.7 in winter.