The variability of the thermal state over the western Pacific warm pool(WP) and the characteristics of its adjacent convective activities were studied using the monthly subsurface sea temperature data of GODAS from 1981 to 2011,together with a variety of statistical methods.The heat content(HC) was defined as the subsurface vertical temperature averaged from 5 to 366 m.The results demonstrate that:(1)The WP area is the place where the HC has its largest variability,and its maximum value can reach 1.2 ℃ which is equivalent to the variation in SST.The depth layer from 100 to 200 m is the largest in terms of the change in subsurface temperature,usually changing from -4.0 ℃ to 4.0 ℃ Its seasonal variation is highly consistent with SST,and its interannual variability is much greater than that of SST.There is a certain degree of contribution to the HC from the SST of the WP.The thermal condition of the WP is closely related with ENSO events,as the largest cold(warm) SST anomalies correspond to El Niño(La Niña) events in the ENSO cycle.(2)The dominant mode of HC is one of positive anomalies,and its corresponding time coefficient(PC1) shows evident annual variability in the sub-layer heat condition over the WP.A heat content index(HCI) was constructed by using the HC averaged over the WP region.Then,five colder years(HCI smaller than -1) and six warmer years(HCI larger than 1) were identified from the total 31 years,with the total abnormal years accounting for 1/3 of the whole period.(3)There is a close relationship between the convective activities nearby the WP and the abnormal thermal state there in summer.The area of(16-26°N,126-146°E) around the Philippines was chosen as the key area to reflect the characteristics of convection of the adjacent areas of the WP,revealing that the convective activities over this critical region significantly enhance(weaken) when the WP is warmer(colder).The fact that convective activities are affected by the HC can be traced back to the July prior to a particular year,and through to the September of that current year,demonstrating the strongly persistent effects of the HC anomalies on the convective activities.(4)HC anomalies of the WP cause abnormal convection around the Philippines,and thus stimulate the East Asia-Pacific teleconnection pattern,with a positive-negative-positive pattern of centers in the 500 hPa height fields from the low to the high latitudes over East Asia in summer.The region with positive correlation in the low latitudes corresponds to the western Pacific subtropical high;the negative correlation in the midlatitudes corresponds to the Mei-yu front;and the other positive correlation in the high latitudes represents the Okhotsk high.This circulation situation indicates that when the convective activities around the Philippines are enhanced,it is conducive to the western Pacific subtropical high controlling the Yangtze River region,with its intensity weakened.As a result,the precipitation and convective activities over the Yangtze River in summer will be affected,due to the weakened southward movement of cold air,which is the result of the weakened Okhotsk high.In order to study the responses of the atmospheric circulation in East Asia to the thermal states of the WP,the anomalous wind fields in the lower troposphere were composited between the significant warmer and colder years.The results reveal that there is an abnormal anticyclonic(cyclonic) circulation bias in the lower troposphere over the western Pacific Ocean to the east of the Philippines when the WP is warmer(colder),which has an important influence on the East Asian monsoon and the precipitation over eastern China.