Fig. 3From: Correlation networks of air particulate matter (\(\hbox {PM}_{2.5}\)): a comparative studyComparison of Methods in China: the Z-score network definition method formulates less densely connected networks, detecting links from high correlation values achievable only within a short and significant interval of time lags. a, e Weights display similar bi-modal distributions. b, f Averages of positive and negative weights at distance r: cities in high proximity are more highly correlated while Z-scores are distance-independent. c, g Probability distribution function of time lag \(\delta\)* in positive and negative networks following a characteristic 12 h periodicity. d, h Spatial distribution of positive directional weighted degree during the last week of 2017: Method II reveals nodes with sharp haze events and their direction of transportBack to article page