How does El Niño-Southern Oscillation affect winter fog frequency over eastern China?

The winter fog frequency over eastern China displays remarkable interannual variability, which has a linear relationship with El Niño-Southern Oscillation (ENSO). Eastern China usually experiences more (less) frequent fog during El Niño (La Niña) winters. During El Niño winters, an anomalous anticyclone tends to appear over the western North Pacific (WNP), which can weaken the climatological winter northerly winds and enhance water vapor supply from oceans, conducive to the formation of foggy weather. Roughly opposite anomalies of fog frequency are displayed during La Niña winters. However, this linear relationship is mainly contributed by the La Niña and partial El Niño events, since the El Niño events exhibit diversity in impacts on the winter fog frequency due to their different types. Increased winter fog frequency can be significantly detected during eastern-Pacific (EP) El Niño, while this signal is not observed during central-Pacific (CP) El Niño. It is found that the winter fog frequency during the CP El Niño seems to be dependent on its zonal locations, associated with different WNP atmospheric circulation and local difference between air temperature and dew point temperature (T − Td) anomalies. The further eastward CP El Niño largely coincides with more frequent fog weather similar to the EP El Niño, while the further westward CP El Niño is usually accompanied with less frequent fog weather. This relationship has important implications for seasonal prediction of winter fog frequency and places a high requirement on consideration of zonal location of the CP El Niño. [ABSTRACT FROM AUTHOR]