Spacial Structure and Annual Variation Estimated from Argo Float Data for Subtropical Mode Water in the Northwest Pacific Ocean

Based on the Argo float profiliug data from International ARGO data center and the WOAOL data (World Ocean Atlas 2001) in the period from Jan, 2004 to Oct, 2007, the features of the spatial structure and temporal variation in the area (30~35°N, 140~155°E) where the North Pacific Subtropical Mode Water (NPSTMW) is formed are analyzed. The monthly mean temperature and salinity for March are used to show the spatial range of NPSTMW. The water has its northern boundary at 34.5 °N, its southern at 30°N or further, its eastern at 151.5°E, and its western at 140° or further, and it is shallower than 350 m. The seasonal variation of area is also analyzed by use of the monthly mean temperature and salinity data. At the same time, new method is suggested to define NPSTMW by means of the salinity criterion. Furthermore the sea level anomaly data are jointly used to analyze the eddy effect on NPSTMW. The results show that eddies only give a short time effect on NPSTMW and the water property will be recovered to the normal conditions after eddies have passed away. Finally as shown from the hydrographic data (2004~2007), NPSTMW keeps stable and less change in the 4 years time.