An Improved Nearness Grey Incidence Model and Its Application in the Analysis of Air Pollutants in Beijing-Tianjin-Hebei Region

A new nearness grey incidence model that not only measures the degree of correlation but also measures the direction is proposed to analyze the distribution characteristics of air pollutants in the Beijing–Tianjin–Hebei region, from 2016 to 2024. To be specific, improvements in this proposed model lie in the following aspects: First, the calculation method of the symbol judgement factor is updated, so that the final nearness grey incidence degree can better reflect the nearness degree and nearness direction between any two sequences, which improves the stable robustness of the grey incidence degree. Second, the anti-fluctuation factor is introduced into the new model, and the relative volatility between series is included in the calculation process of the grey incidence degree. Third, several practical properties of the proposed model are elaborated to further interpret the feasibility and adaptability of the proposed model. In experiments, based on the daily data of the six pollutants in the Beijing–Tianjin–Hebei region from 2016 to 2024, using the new model as a tool, the main pollutants in the Beijing–Tianjin–Hebei region are identified, the temporal and spatial distribution of different pollutants is analyzed, the changes in trends of air pollution processes in the past 9 years are identified, and a comparison with pollution levels of other cities in Beijing–Tianjin–Hebei and Beijing is also detailed. Finally, the superlative performance of the proposed model is confirmed by the model comparison, Monte Carlo analysis and example analysis.