The autumn precipitation over southwest China is one of the main causes of
meteorological disasters. Using observed monthly station rainfall data and HadISST
and NCEP/NCAR analysis data, the impacts of three types of El Ni
ño-Southern Oscillation
(ENSO) events on the boreal autumn rainfall over southwest China were determined.
Over southwest China, autumn rainfall constitutes > 20% of the total annual rainfall
and a marked decline in autumn rainfall commenced around 1990. During La Ni
ña events,
there is surplus (deficit) over the middle (northwest and southeast) of southwest
China. In cnetral Pacific (CP) El Ni
ño events, the autumn rainfall anomaly shows
a deficiency over China. The large-scale atmospheric circulation anomalies in the
three ENSO categories also exhibit distinct characteristics. During CP El Ni
ño autumns,
the pressure anomaly over the North Pacific Ocean displays a “
” structure, with
a high-pressure anomaly over the Asian continent. An anomalous cyclone appears over
the western North Pacific (WNP). In EP El Ni
ño autumns, the pressure anomaly over
the North Pacific Ocean has a “
” structure, with a low-pressure anomaly over the
Asian continent. An anomalous anticyclone appears over the WNP and the 500-hPa anomalies
are opposite to those of CP El Ni
ño events. During La Ni
ña autumns, the characteristics
of circulation present
the opposite structure to those of CP El Niño events. This work is of certain
significance for an in-depth understanding of the impacts of ENSO on the autumn precipitation over southwest China.