This paper uses more than 5000 colocated and near coincident in-situ profiles from the National Oceanic and Atmospheric Administration/Global Temperature and Salinity Profile Program database spanning over the period from 2002 to 2005 to systematically validate the satellite-altimetry-derived upper ocean thermal structure in the western North Pacific Ocean as such ocean thermal Structure information is critical in typhoon-intensity change. It is found that this satellite-derived information is applicable in the central and the southwestern North Pacific (covering 122-170 degrees E, 9-25 degrees N) but not in the northern part (130-170 degrees E, 2540 degrees N). However, since> 80% of the typhoons are found to intensify in the central and southern part, this regional dependence should not pose a serious constraint in studying typhoon intensification. Further comparison with the U.S. Naval Research Laboratory's North Pacific Ocean Nowcast/Forecast System (NPACNFS) hydrodynamic ocean model shows similar regional applicability, but NPACNFS is found to have a general underestimation in the upper ocean thermal structure and causes a large under-estimation of the tropical cyclone heat potential (TCHP) by up to 60 kl/sq cm. After validation, the derived upper ocean thermal profiles are used to study the intensity change of super typhoon Dianmu (2004). It is found that two upper ocean parameters, i.e., a typhoon's self-induced cooling and the during-typhoon TCHP, are the most sensitive parameters (with R2 - 0.7) to the 6-h intensity change of Dianmu during the study period covering Dianmu's rapid intensification to category 5 and its subsequent decay to category 4. This paper suggests the usefulness of satellite-based upper ocean thermal information in future research and operation that is related to typhoon-intensity change in the western North Pacific.