Impact of Low-Frequency Oscillation Intensity and Phases in Tropics on the Winter Precipitation in Southern China

The relationship of the low-frequency oscillation(LFO) intensity and phases in tropics and the winter precipitation in southern China has been investigated based on the NOAA outgoing longwave radiation (OLR) data,NCAR/NCEP data and observed precipitation data in China.The phase composites of the low-frequency precipitation for the high-index years show that the phase changes are significantly correlated with the low-frequency changes of the circulation systems in the subtropical and Philippines and they can affect the precipitation in southern China for different phases.For the high-index years when the active convection center is located in tropical Indian Ocean(western Pacific),the Arabian trough and the Bay of Bengal trough are deepened(weakened),and the anticyclone(cyclone) circulation appears near Philippines.Such environment leads to the south(north) wind anomaly to appear in southern China,the moisture and upward motion are increased(decreased) and the precipitation is more(less).The anomalies in convection,precipitation and other factors are not obvious in each phase for the low-index years.