The approach of the previous anomalous heat content in the western Pacific warm pool affecting the summer rainfall over the middle and lower reaches of the Yangtze River

The relationship between the previous heat content anomaly in the western Pacific warm pool(WPWP) and summer rainfall over the middle and lower reaches of the Yangtze River,and the way how heat content anomaly probably affects the summer rainfall are studied by using the historical ocean temperature analysis data provided by Japan Meteorological Agency,NCEP/NCAR reanalysis dataset,sea surface temperature and rainfall data.The results indicated that there is a significant two-season lead negative correlationship between the previous heat content of the WPWP and the summer rainfall over the middle and lower reaches of the Yangtze River,and it is an important indicator for prediction that the smaller anomalies of the 0~200 m heat content averaged from November to January in the key area(166.5°E-173.5°W,7.5°S-3.5°N) are followed by more rain in the middle and lower reaches of the Yangtze River.The baroclinic East Asia-Pacific(EAP) teleconnection stimulated by the previous heat content anomaly for its persistence in the WPWP may be the main reason that influences the summer rainfall in the middle and lower reaches of the Yangtze River.The negative heat content anomaly between the previous November and January in the key area leads to the formation and persistence of anomalous Philippine Sea anticyclone.In summer,the anticyclone expands northwestward and strengthens,and then the EAP teleconnection appears along the East Asian coast,which makes the middle and lower reaches of the Yangtze River and the area to its east in the Northwest Pacific subtropical region under the control of anomalous cyclone,and thus the middle and lower reaches of the Yangtze River becomes the area where cold air from the North and warm air from the South join together.At the same time,there exists a wave train of EAP pattern in the upper troposphere tilting to northwest compared to the middle and lower troposphere,so that the middle and lower reaches of the Yangtze River and the area to its south is under the control of anomalously stronger high,which is conducive to more rain in the middle and lower reaches of the Yangtze River with upper tropospheric divergence as well as middle and lower tropospheric convergence,and vice versa.