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Jack A. C. Kaiser

Abstract

BY Placing a small convective source (electrical heater) in a rotating, vertically sheared, stratified flow in a rotating annulus, a well-organized vortex flow is generated. A qualitative description of the flow is given. The flow is always cyclonic below the heater and anticyclonic above, and is quite persistent in the sheared flow.

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Jack A. C. Kaiser

Abstract

Measurements of the components of the heat balance of the upper 30 m of the ocean were made in the Bermuda area in August and September 1974. The quantities measured included surface downwelling and underwater downwelling and upwelling irradiance, surface net irradiance, heat content, and the bulk meteorological variables.

Under conditions of light winds, one or more layers of 1 to 10 m thickness form and persist at the surface. In some cases the bottom of the layers have sufficiently high Richardson numbers so that no vertical transport occurs through them, vastly simplifying the measurements and interpretation of their heat balance. These data illustrate several such cases. The net flux of heat from the layer at the surface is usually much larger than the bulk formulas predict in these light wind cases. When the winds are calm and the sea glassy, total heat fluxes of several kilowatts per square meter occur for several hours in the afternoon. This has been observed previously in the Sargasso Sea.

Generally twice during the day, the beat content of the upper ocean has an extremum, usually after sunrise and somewhat before sunset. At these times the net heat flow out of a layer is equal to the irradiance absorbed in the layer providing a simple determination of surface fluxes from irradiance measurements. These measurements show this feature clearly.

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Jack A. C. Kaiser

Abstract

Measurements of underwater downwelling D, underwater upwelling U, both at 5 m, and surface down-welling irradiance I were taken over most of a 5-day period in August and September 1974 south and west of Bermuda. On clear days D/I reached a pronounced maximum at local noon, whereas U/I had a weak minimum at midday. On cloudy days both of the above ratios were larger at all times of the day and did not exhibit the midday maximum.

An absorption model for D/I is constructed by decomposing I into components from the sun, clear sky and clouds. The major differences between the components is their spectral and radiance distributions. Atmospheric water vapor and sea surface roughness effects are included. The model agrees with the experimental values of D/I to within 5% of I for A the data, and it reproduces the variation of this ratio with solar zenith angle and cloud cover.

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Jack A. C. Kaiser

Abstract

Results of heat transfer measurements in a differentially heated annulus of fluid for both the non-rotating and rotating cases are given. (In the latter case the flow is in the upper symmetric regime.) In all cases the upper surface of the fluid is free. The non-rotating heat transfer is essentially the same as that of vertical slot convection, whereas rotation modifies the heat transfer; the resulting main effects appear to be exerted through a decrease in the Ekman layer thickness.

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Jack A. C. Kaiser and Kingsley G. Williams

Abstract

By measuring the time rate of change of temperature in the upper 65 m of the sea at night with a precision sounding device, the amount of heat transported upward at various depths and through the sea surface as a function of time during the night was determined. The heat flux through any surface of depth z was given by e −αt (1−Az ) for z<z max (40–65 m). The amount of heat released from the sea surface ranged from 1.34 to 0.311 ly min−1, the release rate decreasing with time after sunset.

The data also allowed estimates of the spatially averaged thermal boundary layer thickness in the sea surface, 0.2 cm or less.

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Dave Fultz and Jack A. C. Kaiser

Abstract

Detailed measurements of the complete vector-velocity and temperature fields have been carried out for an upper symmetrical (Hadley regime) flow in a rotating, differentially heated annulus of water in order that precise comparison could be made with numerical integrations by G. Williams. To make the measurements, small hypodermic probes must be inserted into the fluid from above. Definite and significant alterations of the torque-angular momentum balance of the fluid, and associated alterations of other field variables have been detected experimentally and shown to be due to the probes. Measurements have been made that allow extrapolation from the altered state to a “no-probe” state and the determination of correction fields for the temperature and velocity. Evidence that the drag on the probes in the upper westerly zonal flow may be the main source of the flow alteration is given. Important implications of the existence of such effects for quantitative meteorological experiments are pointed out, including clear indications that, for the low probe Reynolds numbers involved, the drag values cannot be greatly reduced by reducing probe sizes.

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