The turbulent structure of the internal boundary layer near the shore

A field experiment to measure the turbulent structure of the internal boundary layer near the shore was conducted using three instrumented meteorological poles, a kytoon, and a crane-mounted ultrasonic anemometer-thermometer, as well as three reference ultrasonic anemometer-thermometers positioned near the poles. Part 1 of this study gives the explicit details and general characteristics for one run of the experiment. Part 2 (Ohara and Ogawa, 1984) will present a similarity and energy budget analysis. The mean velocity profiles showed that there was wind speed acceleration due to the sea-land temperature difference. In addition, the velocity profiles consisted of three distinct regions; the region near the ground had the largest gradient followed by a transition zone which had a small velocity gradient, while above, the profile resembled the oncoming sea breeze. In general, the turbulence was greatest near the shore, gradually decreasing inland. The lowest region had large turbulence intensities and the transition region had some intermittent turbulence characteristics between the lower strong unstable layer and the relatively turbulent-free region above.Deceased March 1984.Present address: The Institute of Behavioral Sciences, Yoyagi, Tokyo 151, Japan.     

The effects of mesoscale convective cells on the surface wind field over the ocean

Near-surface wind velocities were measured on an array of anchored spar buoys in the East China Sea in February 1975 as a part of the Japanese AMTEX '75 (Air Mass Transformation Experiment), a subprogram of GARP. These data were used to determine the effects of atmospheric convection associated with mesoscale convective cells (MCC) on near-surface winds over the ocean. When MCC were present, a peak occurred in the near-surface wind spectrum in the so-called spectral gap.     

Aircraft Observations of Air-mass Modification Over the Sea of Okhotsk during Sea-ice Growth

In order to quantitatively investigate the role of leads and sea-ice in air-mass modification, aircraft observations were conducted over the partially ice-covered Sea of Okhotsk. We investigated two cold-air outbreak events with different sea-ice concentrations. In both cases, the difference between the temperatures of surface air and the sea surface (ΔT) dropped rapidly with the accumulated fetch-width of leads up to about 35-40 km, and then decreased very slowly. The surface sensible heat flux originating from open water was about 300 W m⁻² within a few kilometres from the coast and decreased with increasing accumulated fetch-width. The sensible heat flux was about 100 W m⁻² on average. These results indicate that the downwind air-mass modification depends mainly on the total (accumulated) extent of open water. The total buoyancy flux calculated by the joint frequency distribution method correlated very well with ice concentration. Such a relationship was not clear in the case of the moisture flux . The ratio between rising thermals and cold downdrafts differed significantly between upwind and downwind regions; that is, the buoyancy flux was dominated by in the developing stage of the boundary layer, while also became important after the development of the boundary layer.     

A Generation Mechanism for Mesoscale Eddies in the Kuril Basin of the Okhotsk Sea: Baroclinic Instability Caused by Enhanced Tidal Mixing

Mesoscale eddies, particularly anticyclonic ones, are dominant features in the Kuril Basin of the Okhotsk Sea. In 1999, both surface drifter and hydrographic observations caught the same anticyclonic eddy northwest of Bussol’ Strait, which has a diameter of ∼100 km, typical surface velocity of 0.2–0.3 m s⁻¹, and less dense core extending to a depth of ∼1200 m. Based on an idea that the generation of mesoscale eddies is caused by strong tidal mixing in and around Kuril Straits, we have conducted a series of three-dimensional numerical model experiments, in which strong tidal mixing is simply parameterized by increasing coefficients of vertical eddy viscosity and diffusivity along the eastern boundary. Initially, a regular series of disturbances with a wavelength of ∼70 km starts to develop. The disturbances can be clearly explained by a linear instability theory and regarded as the baroclinic instability associated with the near-surface front formed in the region between the enhanced mixing and offshore regions. In the mature phase, the disturbances grow large enough that some eddies pinch off and advect offshore (westward), with the scale of disturbances increasing gradually. Typical eddy scale and its westward propagation speed are ∼100 km and ∼0.6 km day⁻¹, respectively, which are consistent with the observations by satellites. The westward propagation can be explained partly due to nonlinear effect of self-offshore advection and partly due to the β-effect. With the inclusion of the upper ocean restoring, the dominance of anticyclonic eddy, extending from surface to a depth of ∼1200 m, can be reproduced.     

Distribution coefficient of Mg ions between calcite and solution at 10–50°C

The distribution coefficient (λ_Mg) of Mg²⁺ ions between calcite and solution was found to be 0.012 ± 0.001 (10°C), 0.014 ± 0.001 (15°C), 0.019 ± 0.001 (25°C), 0.024 ± 0.001 (30°C), 0.027 ± 0.001 (35°C) and 0.040 + 0.003 (50°C). This indicates a remarkable dependence on temperature. The effect of the Mg²⁺/Ca²⁺ molar ratio in a parent solution on λ_Mg for calcite is small, where the molar ratio lies in the range 0.04-2. However, the λ_Mg value for aragonite tends to decrease with increasing Mg²⁺/Ca²⁺ ratio in the parent solution. The largest Mg content of calcite in the Ca(HCO₃)₂-Mg²⁺ → calcite system is around 2 mol% in the temperature range 10–50°C. Neither homogeneous nor heterogeneous distribution laws hold for aragonite precipitation, and the temperature effect on the coprecipitation of Mg²⁺ ions with aragonite is very small.     

Pre-Japan-ARGO: Experimental Observation of Upper and Middle Layers South of the Kuroshio Extension Region Using Profiling Floats

We deployed two profiling floats in the region south of the Kuroshio Extension in March 2000. Temperature and salinity profiles from a depth of 1500 × 10⁴ Pa to the surface are reported every two and four weeks, respectively. The floats performed very well for first four months after deployment. Later they failed in surfacing for a few months when the sea surface temperature in the region was high. The salinity sensors seemed to suffer from some damage during their failure-in-surfacing period. Despite this trouble, the results clearly demonstrate that the profiling float is a very useful and cost-effective tool for physical oceanographic observation in the open sea. This revised version was published online in July 2006 with corrections to the Cover Date.     

The coprecipitation of uranium with calcium carbonate

This report is one of the studies on the factors controlling the trace element contents of marine calcareous skeletons. The values of the distribution coefficients of UO₂ ²⁺ between solutions and carbonate precipitates were measured in the laboratory at 20±1C. From the determination of the uranium contents of marine calcareous skeletons and sea water, the values of uranium between marine calcareous skeletons and sea water are expected as 1.2 to 0.3 for aragonite and 0.2 to 0,0n for calcite. The experimentally measured value of the distribution coefficient for aragonite is thermodynamically discussed. And it was known that the value of the distribution coefficient of UO₂ ²⁺ is controlled greatly by the activity coefficient of uranium dissolved in a parent medium and the crystal form of CaCO₃. The activity coefficient of uranium in solution mainly owes to the formation of complexes between UO₂ ²⁺ and CO₃ ^2–in the solution.     

Mass balance of heavy metals in the seto inland sea, Japan

To discuss the geochemical and environmental behavior of heavy metals in the Seto Inland Sea, the largest semi-enclosed coastal sea in Japan, mass balances of Cu and Zn were studied by application of a simple box model using sedimentation rates and heavy metal contents of core sediments. In 1980, total sedimentary loads of Cu and Zn over the whole area of the Sea were estimated to be 630 and 3500 tons year⁻¹, respectively. Further, the sedimentary loads without (natural) and with human activities were estimated separately to be, respectively, 320 and 310 tons year⁻¹ for Cu and 1800 and 1700 tons year⁻¹ for Zn. Total inputs of Cu and Zn into the Sea, in 1980 were estimated to be 870 and 4250 tons year⁻¹ about one half of this being the result of human activities. 70% of the Cu input and 80% of the Zn input are taken into the sediments. Mean residence times of Cu and Zn in the Sea are calculated to be ≈0.3 and 0.2 years, respectively. Since these values are relatively small compared to the mean residence time of the seawater (0.9 years), Cu and Zn supplied to the Sea are considered to be accumulated rapidly in the sediments.