Continuous currents, water quality and meteorological monitoring have been conducted at the mouth of Tokyo bay since Dec. 2003. The data were obtained using a ferry boat, Tokyo-wan Ferry“Kanayamaru”. Analyzed results are as follows.
　(1) Maximum (Minimum) water temperature is about 27℃(12℃) in Jul. to Aug. (Jan. to Feb.). Due to the intrusion of Kuroshio current, water temperature in winter changes about 5℃ in a period of 1 to 2 weeks. Salinity is about 34PSU in dry winter and 25PSU in autumn because of heavy rain fall. Maximum concentration of Chlorophyll.a is about 10μg/l in winter and 54μg/l in Jun. to Sep.
　(2) Before the occasion of a strong intrusion of Kuroshio current, there is a strong water outflow from Tokyo Bay. The Kuroshio intrusion was periodic in Jan. to Mar. 2004 and the peak spectrum is seen in 7.1days and 21.3days.
　(3) According to the cross correlation between the flow rate in Tama river and the salinity at the mouth of Tokyo Bay, the salinity at the mouth of Tokyo Bay becomes minimum in 2 to 3 days after the time when the flow rate in Tama river is maximum.
　(4) Using ABIC (Akaike Bayesian Information Criterion) , water exchange rate is estimated from the current obtained by ADCP data. The maximum (minimum) rate was seen in autumn (winter).