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A major ocean response to tropical cyclone (TC) wind is the mixing of warm sea-surface water with cool subsurface water, which decreases the sea-surface temperature (SST). The decreased SST (δT) under the TC (rather than the cooled water in the wake after the storm has passed) modifies the storm's intensity and is of interest to TC intensity studies. Here, the author shows that δT (non-dimensionalized by some reference temperature) is linearly related to Ψ, a dimensionless (nonlinear) function of TC and ocean parameters: the TC maximum wind, radius, and translation speed, as well as the ocean's 26 °C and 20 °C isothermal depths (Z26 and Z20). The Ψ can be estimated from observations. The modelled δT is validated against sea-surface cooling observed by satellites, δTo, for typhoons during the May–December 2015 period in the western North Pacific. The result yields a best-fit, linear relation between δTo and Ψ that explains ~60% of the observed variance: r2 ≈ 0.6 (99% confidence). Tests show that the cube of the TC maximum wind and the ocean's Z26 account for 46% and 7%, respectively, of the observed variance, indicating their predominant influence on TC-induced cooling. Contributions from other parameters are less but not negligible. [ABSTRACT FROM AUTHOR]

A major ocean response to tropical cyclone (TC) wind is the mixing of warm sea-surface water with cool subsurface water, which decreases the sea-surface temperature (SST). The decreased SST (δT) under the TC (rather than the cooled water in the wake after the storm has passed) modifies the storm’s intensity and is of interest to TC intensity studies. Here, the author shows that δT (non-dimensionalized by some reference temperature) is linearly related to Ψ, a dimensionless (nonlinear) function of TC and ocean parameters: the TC maximum wind, radius, and translation speed, as well as the ocean’s 26 °C and 20 °C isothermal depths (Z26 and Z20). The Ψ can be estimated from observations. The modelled δT is validated against sea-surface cooling observed by satellites, δTo, for typhoons during the May–December 2015 period in the western North Pacific. The result yields a best-fit, linear relation between δTo and Ψ that explains ~60% of the observed variance: r2 ≈ 0.6 (99% confidence). Tests show that the cube of the TC maximum wind and the ocean’s Z26 account for 46% and 7%, respectively, of the observed variance, indicating their predominant influence on TC-induced cooling. Contributions from other parameters are less but not negligible.

Time series changes in sea surface temperature (SST), chlorophyll a (Chl a), nutrients (PO, NO), and sea winds, which correlated with the passage of Typhoon Shanshan in the East/Japan Sea (EJS), are illustrated using satellite data for Chl a, SST, sea winds, and in situ data for nutrients and water temperature. The sea-surface cooling (SSC) effect by the passage of the typhoon was higher at stations nearer to the center compared to stations further from the center. The SSC effect at stations in the colder water region (on the left side of the typhoon's track) was higher than at stations in the Tsushima Warm Current region (on the right side of the typhoon). The SSC effect continued for approximately 10 days after the passage of the typhoon. The Chl a concentration at all stations increased after the passage of the typhoon. This increase continued for a period of approximately 10 days, but the duration period at each station varied with distance from the typhoon center. Changes in Chl concentrations at stations within a 2° distance on both sides from the typhoon's center were higher than that at other stations. The changes in Chl a by the passage of the typhoon were measured at approximately 0.3-1.0 mg/m along the moving path of the typhoon. Phosphate and nitrate changes were inversely correlated with the water temperature changes; the nutrient concentration increased with the passage of the typhoon. Like the changes in SST, changes in nutrient concentrations on the left side of the typhoon's track were higher compared to those at the center and the right side. [ABSTRACT FROM AUTHOR]

Abstract: An automatic measuring system for the partial pressure, pCO2, of atmospheric and oceanic carbon dioxide was developed. The system was mounted on a moored buoy for routine observation of maritime meteorology in the East China Sea. CO2 observations were conducted from June 29, 1997 to January 6, 1998. During the observation period, the atmospheric pCO2 showed little variation (341–365μatm), whereas pCO2 in the surface water varied significantly (308–408μatm). In the summer, pCO2 was higher in the surface water than in the overlying atmosphere, implying that this area was a source for atmospheric CO2, though it became a sink after late September. Time-series data clearly exhibited significant short-term variations in the oceanic pCO2, i.e. sudden variations during the passage of typhoons, and diurnal variations driven by the diurnal variations in the sea-surface temperature under calm conditions. The effects of typhoons on ocean–atmosphere CO2 exchange at the surface could differ, depending on the relative position of the mooring site with respect to the center of the moving typhoons. These differences result from the different contributions of sea-surface cooling, entrainment, and upwelling. The efflux enhanced by three typhoons accounted for 60% of the efflux of CO2 in the warm season. It is suggested that typhoons have a significant impact on the carbon cycle in the western subtropical North Pacific. [Copyright &y& Elsevier]

Abstract: Low vertical mixing rates are a key physical condition associated with the development of phytoplankton spring blooms in coastal and ocean waters. Vertical mixing rates in shallow coastal regimes are decreased not only by thermal stratification but also by haline stratification due to river runoff. In this paper, the main physical processes involved in the onset of phytoplankton spring blooms are examined in a tide-dominated estuarine embayment, characterized by weak current velocities, using a 1-D ecosystem model (the European Regional Seas Ecosystem Model) coupled with a 3-D physical model (the Princeton Ocean Model coupled with a sediment transport model) via the off-line method. Simulation results show that a reduction in vertical mixing, caused by the episodic input of buoyant, freshwater inflows from a reservoir during the period of neap tides, is the main physical controlling process on the occurrence of spring algal blooms. Furthermore, sensitivity tests using: (1) layered and (2) depth-averaged monthly vertical eddy diffusivity values reveal that the timing of phytoplankton spring blooms in the model is strongly affected by the parameterization of vertical diffusivity. [Copyright &y& Elsevier]