Simulations of convection/ventilation and diagnoses of water mass subduction/formation/transformation in the Japan/East Sea (JES): Impact of atmospheric forcing with different time-space scales .

摘要

In this study the impacts of surface atmospheric forcing of different time-space scales on water mass formation and spreading of formed water are investigated for the Japan/East Sea (JES). Three sets of atmospheric flux data were used; (1) fluxes from monthly averaged atmospheric variables (mont), (2) monthly means of 6-hourly fluxes ( empm), and (3) 6-hourly fluxes (syn). To calculate wind stress and heat fluxes, surface atmospheric variables (wind vectors, air temperature, dew point temperature, etc.) from the 6-hourly ECMWF (1° x 1°) data set, monthly mean cloud cover from COADS (1° x 1°), and daily MCSST (ca. 18 km) were utilized for the period from 1993 to 1997, the period of the CREAMS cruises.; The annual magnitudes of JES-averaged fluxes for the three different data sets are very different: the wind stress of mont is ca. 45% of that of the other two data sets (empm and syn). With the net heat flux of empm and syn, the JES loses heat from the surface with a range from −74 W/m2 in 1996 to −54 W/m2 in 1997. These results are consistent with those from Hirose et al. (1996) of −50 W/m 2 and Na et al. (1999) of −108 W/m2. While with the net heat flux of mont, however, the JES gains heat, ranging from 0.4 W/m2 in 1996 to 19 W/m2 in 1997.; The Princeton Ocean Model was implemented for JES (JES-POM) to simulate interannual, seasonal, and mesoscale variations in velocity and hydrographic fields. It reproduced the general features of the JES circulation. However, the air-sea forcing conditions do not appear to be directly responsible for the strong subduction in Area K and Area KB. In empm and syn, the “flux center” off Vladivostok is identified as the primary subduction area, though the positions and values of the localized maximum subduction rate are different year-to-year. There is no localized maximum subduction rate in the “flux center” off Vladivostok in mont for any of the simulated years, while it occurs in empm every year except 1997 and in syn for all five years.; During January 1997, mesoscale atmospheric forcing was applied to JES-POM and the mean MLD depths were deeper in the MM5 case along the Primorski coast and in the “flux center”. Overall, surface waters in the MM5 case become cooler and saltier in the convection areas. (Abstract shortened by UMI.)