The wind field plays a decisive role in haze generation and dissipation processes over the Beijing- Tianjin-Hebei （BTH） region. Although geographically the BTH region is under the influence of the East Asian winter ...The wind field plays a decisive role in haze generation and dissipation processes over the Beijing- Tianjin-Hebei （BTH） region. Although geographically the BTH region is under the influence of the East Asian winter monsoon （EAWM）, this study finds that common indices of the EAWM cannot adequately describe the actual wind speed changes in the BTH region.Thus, observational data are used to analyze the interannual variations of the winter wind field over the BTH region. The results show that the average winter wind speed is 2.0 m s-1, with a slight rate of decline of 0.01 m s-1 yr-1. In most cases, strong-wind years correspond to negative sea surface temperature （SST） anomalies over the tropical Pacific, whereas weak-wind years correspond to positive SST anomalies. Moreover, correlation and composite analyses show that the interannual variability is affected by multiple factors, including the following： （1） the pressure gradient in the high and middle latitudes of the Northern Hemisphere, as in strong-wind years the pressure gradient helps cold air move from high latitudes to middle latitudes; （2） the skin temperature in Eurasia, as low skin temperature in Eurasia in strong-wind years is conducive to the accumulation of cold air; and （3） the SST of the tropical Pacific east of the Philippines, as in strong-wind years the high temperature of this area affects the BTH region through anticyclonic activity and associated tropical circulation systems.展开更多
基金supported by the National Natural Science Foundation of China[grant number 41176014]
文摘The wind field plays a decisive role in haze generation and dissipation processes over the Beijing- Tianjin-Hebei （BTH） region. Although geographically the BTH region is under the influence of the East Asian winter monsoon （EAWM）, this study finds that common indices of the EAWM cannot adequately describe the actual wind speed changes in the BTH region.Thus, observational data are used to analyze the interannual variations of the winter wind field over the BTH region. The results show that the average winter wind speed is 2.0 m s-1, with a slight rate of decline of 0.01 m s-1 yr-1. In most cases, strong-wind years correspond to negative sea surface temperature （SST） anomalies over the tropical Pacific, whereas weak-wind years correspond to positive SST anomalies. Moreover, correlation and composite analyses show that the interannual variability is affected by multiple factors, including the following： （1） the pressure gradient in the high and middle latitudes of the Northern Hemisphere, as in strong-wind years the pressure gradient helps cold air move from high latitudes to middle latitudes; （2） the skin temperature in Eurasia, as low skin temperature in Eurasia in strong-wind years is conducive to the accumulation of cold air; and （3） the SST of the tropical Pacific east of the Philippines, as in strong-wind years the high temperature of this area affects the BTH region through anticyclonic activity and associated tropical circulation systems.
