Inconsecutive 'Sandwich Structure' Pattern For High Temperature Warm Water In The Western Pacific Warm Pool

An inconsecutive high frequency distribution with'Sandwich structure'pattern for high temperature warm water warmer than 29℃in the western Pacific warm pool (WPWP) was found using Tropical Rainfall Measuring Mission (TRMM) sea surface temperature (SST) data, a relatively high resolution data in space. This phenomenon only shows up in boreal summer (June to September), and becomes obvious when WPWP SST is higher than 29℃. This structure becomes obvious when SST is higher than 29℃, which suggests that'Sandwich Structure'is a special phenomenon of high temperature warm water (HTWW) in the western Pacific warm pool.It appears that East Asian summer monsoon (EASM) has crucial impact on the formation and maintenance of'Sandwich Structure'. As observed, before the onset of EASM, the warm pool is governed by cloud-SST mechanism. However, when EASM arrives at western Pacific, it impinges on Philippine Islands in July, which forms a wind jet at the southern tip, leading to the formation of the'Sandwich Structure'. Winds affect the distribution of SST in two ways:one by increasing the local latent heat flux due to the wind jet; Meanwhile by Ekman transport and strengthening the anticyclone current, EASM can help delivery cold water in the southern part northward and eastward, leading to the appearance of'Sandwich Structure'To analyze the interannual variation of the phenomenon and its possible relationship with El Nino and Southern Oscillation (ENSO), Climate Forecast System Reanalysis (CFSR) data from 1979 to 2009 is picked up. It turns out that the same structure of HTWW in western pool still exists and the impact of EASM on the formation and maintenance of the'Sandwich Structure'is verified again. A cold water index in the low frequency area is defined to depict the variation of'Sandwich Structure', using the area averaged sea surface water anomaly (SSTA) from June to August, and the correlation between the cold water index and Nino 3.4 index in January reaches-0.62 one year in advance, which implies that ENSO affects HTWW in its developing summer by inducing changes in EASM. Generally speaking, the area of cold water is obviously larger when EASM is stronger. In the meantime, an anomaly cyclone circulation occupies Philippine Sea, which attributes to the subtropical anticyclone moving westward and decreasing the rainfall around Yellow River. The anomaly of HTWW in western Pacific warm pool can change the state of North America through teleconnection. Meanwhile, by analyzing warm water in the northern part of Philippine Sea, we find that intraseasonal oscillation there very intensive, which is affected mainly by the variation of the atmosphere.