The Interdecadal Variation In ENSO Impacts On The Autumn Precipitation In The Eastern China

Based on the 160 stations of precipitation data compiled by the China Meteorological Administration from 1951 to 2015,precipitation and extended reconstructed surface temperature data from NOAA,NECP/NCAR reanalysis data sets,the inter-annual and inter-decadal variations of autumn precipitation in eastern China and the tropical ocean affects the transformation characteristics of autumn precipitation in eastern China have been investigated.The main conclusions drawn are as follows:1)The first three modes of autumn precipitation in eastern China were extracted by EOF analysis,the total variance was explained by more than 59%.The EOF1 mode shows the consistent precipitation characteristics in eastern China and the precipitation anomaly in South China is particularly significant.It is affected by the anticyclone circulation near the bottom Philippines and is controlled by the southwest wind.The tropical eastern Pacific warm SST and the western Pacific cold SST have a great impact on the EOF1 mode on an inter-annual scal;the 13-year significant inter-decadal signal of PC1 is closely related to the tropical mid-Pacific SST.EOF2 shows the characteristics of the dipole precipitation pattern in the eastern China,which is controlled by the cyclone circulation from the eastern coast of China to Japan,and the South and North of China are controlled by the southwest and northwest,respectively;the tropical mid-east Pacific SST has a huge impact on the EOF2 mode.Both EOF1 and EOF2 are related to the ENSO signal of the tropical ocean,but there are significant differences in the associated anomalous SST distributions in the equatorial Pacific.EOF3 is characterized by heavy precipitation on the eastern coast and less precipitation inland.It is affected by anomalous anticyclone over the East Asian continent and anomalous cyclone circulation in the eastern coastal region.The inland is affected by the northwestward dry airflow,while the eastern coast is controlled by southwesterly wind.The relationship with the tropical SST is not significant,it may be affected by the mid-high latitude tele-connection in the northern hemisphere.2)The 31-year sliding correlation between ENSO and eastern autumn precipitation indicates that the relationship between them has changed significantly in the mid-1980 s.The atmospheric circulation and the precipitation anomaly in eastern China associated with La Nina in the early stage almost mirrored to the effects of the El Ni?o at this time,resulting in a significant dipole precipitation pattern in eastern China.The impact of El Ni?o in the second period was similar to that of the first period,the impact of La Nina showed a spatially consistent negative precipitation anomaly in eastern China.The inter-decadal variations in ENSO impacts on the autumn precipitation in the Eastern China mainly due to the changes in the influence of the La Ni?a in the second period.3)The impact of the La Ni?a during the second period may due to higher SST and precipitation anomalies in the tropical WNP near east of the Philippines,which cause the westward shift of the anomalous anticyclone from the northeastern Asia near Japan in the first period to Mongolia in the second period.Consequently,the northern China is under the influences of anomalous northerlies along the southeastern flank of the anomalous anticyclone in the later period,which is not conducive to the positive precipitation anomalies.The results of sensitivity test in AGCM confirmed this hypothesis.