Abstract
Using meteorological observation data and NCEP/NCAR (National Centers for Environmental Prediction/National Center for Atmospheric Research) reanalysis data, the impacts of the atmospheric circulation pattern on the interannual variability of haze-fog in northern China in January are studied by means of statistical methods. The results showed that the Eurasian teleconnection (EU) at the 500 hPa isostatic surface is the most important pattern affecting the haze-fog frequency in northern China. However, the existing EU index cannot perfectly describe this pattern. To this end, this study selects three main activity centers to define a new EU index, which are located in the Europe (10 °E, 55 °N), Siberia (80 °E, 60 °N), and Shandong, China (120 °E, 40 °N). The difference between the existing EU index and the new EU index is mainly the position of the anomaly center of the 500 hPa geopotential height. The EU is in a negative phase in higher haze-fog years but is in a positive phase in lower haze-fog years. The 500 hPa geopotential height shows negative anomalies in Europe and East Asian and a positive anomaly in Siberia in the negative EU phase. Using Plumb wave activity flux analysis, it was found that the cold wave affecting northern China is less in the negative EU phase than that in the positive EU phase, which resulted in more haze-fog days. In addition, the results also showed that the EU pattern goes through a considerable development and decay within 13 days. The visibility starts to significantly decrease at a lag of −1 to 2 days in the negative EU peak phase and is influenced by the weak north wind that is caused by the high pressure.
Highlights
Haze and fog lead to reductions in horizontal visibility caused by suspensions in the air [1]. the compositions of the suspended materials are different, fog and haze often coexist and are interchangeable under certain conditions [2,3]
China is less in the negative Eurasian teleconnection (EU) phase than that in the positive EU phase, which resulted in more haze-fog days
Pattern is located over the Eurasian continent, and its changes are closely related to the adjustment of the atmospheric circulation in the northern hemisphere in the winter [18,19], which is an important indicator of climate change in East Asia
Summary
Haze and fog lead to reductions in horizontal visibility caused by suspensions in the air [1]. Pattern is located over the Eurasian continent, and its changes are closely related to the adjustment of the atmospheric circulation in the northern hemisphere in the winter [18,19], which is an important indicator of climate change in East Asia. Liu [26] studied the relationship between the monsoon in East Asia and haze-fog and considered that the calm weather that was related to the Siberian High and cold wave are the main influencing factors of haze-fog variation in the winter. According to the previous analysis, this paper argues that the EU may influence the East Asian monsoon by changing the strength of the East Asian trough and may result in the interannual variability of the haze-fog in northern China.
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