摘要:

During the August‐September 1977 Mixed Layer Experiment (Mile) and the July‐September 1978 Joint Air‐Sea Interaction (Jasin) project, moored current measurements were made in the upper ocean with Savonius rotor and vane vector‐averaging current meters (VACM), dual orthogonal propeller vector‐measuring current meters (VMCM), and dual orthogonal acoustic travel‐time vector‐averaging current meters (ACM). Wind speeds and significant wave heights reached 20ms−1and 5 m. The influence of mooring motion upon ACM, VACM, and VMCM measurements are described. In the mixed layer above about 30 m depth where mean currents are relatively large, the effect of a surface‐following buoy upon ACM, VACM, and VMCM velocity fluctuations at frequencies less than 0.3 cph was negligible; at frequencies above 4 cph, the VACM data contained the largest amount of mooring induced contamination. Below the mixed layer at depths greater than about 75 m, a subsurface mooring should be used; however, when a surface‐following buoy was used, then VMCM data better approximated the spectrum of the fluctuations than VACM data. A spar‐buoy should not be used to measure currents at depths as deep as 80 m. The frequency‐dependent differences between VACM and VMCM and between VACM and ACM measurements are described. At frequencies less than 0.3 cph, the differences between the VACM and ACM or the VMCM records were not significant with 95% confidence limits, were always positive, and above 80 m depth were less than 20%. At frequencies above 4 cph, the VACM‐VMCM differences were about 5 times larger than

ISSN:0148-0227    

DOI:10.1029/JC086iC01p00419

年代:1981

数据来源: WILEY

摘要:

The damping of ocean surface waves by a monomolecular oleyl alcohol film of about 1.5–3 km2in area is measured in the North Sea by wave staffs, a coherentXband microwave scatterometer mounted on a sea‐based platform, and an incoherentKuband microwave scatterometer carried by an aircraft under moderate wind conditions (wind speedu10= 3.5–7.7 m s−1). The observed wave attenuation by the monomolecular surface film measured by a wave staff in the frequency band between 3.2 and 16 Hz is in the range of about 40–60%, with only a slight increase with frequency. From this result it can be predicted that slicks affect microwave backscattering similarly in theLband (λ0≈ 20 cm) as in theKuandXbands (λ0≈ 2 cm). It is shown by additional wave tank experiments that a direct influence of oleyl alcohol surface films on wave damping is confined to frequenciesf≥ 2 Hz, but a further indirect effect of oleyl alcohol films on the damping of ocean waves in the frequency range between 0.12 and 0.7 Hz by modifying the wind input and wave‐wave interaction mechanisms is indicated from our results. A possible directional dependence of the wave‐damping effect caused by surfa

ISSN:0148-0227    

DOI:10.1029/JC086iC01p00429

年代:1981

数据来源: WILEY

摘要:

Practical applications of organic surface films added to the sea surface date back to ancient times. Aristotle, Plutarch, and Pliny the Elder describe the seaman's practice of calming waves in a storm by pouring oil onto the sea [Scott, 1977]. It was also noted that divers released oil beneath the water surface so that it could rise and spread over the sea surface, thereby suppressing the irritating flicker associated with the passage of light through a rippled surface.From a scientific point of view, Benjamin Franklin was the first to perform experiments with oils on natural waters. His experiment with a ‘teaspoonful of oil’ on Clapham pond in 1773 inspired many investigators to consider sea surface phenomena or to conduct experiments with oil films. This early research has been reviewed byGiles[1969],Giles and Forrester[1970], andScott[1977]. Franklin's studies with experimental slicks can be regarded as the beginning of surface film chemistry. His speculations on the wave damping influence of oil induced him to perform the first qualitative experiment with artificial sea slicks at Portsmouth (England) in October of 1773. Although the sea was calmed and very few white caps appeared in the oil‐covered area, the swell continued through the oiled area to Franklin's great disappoin

ISSN:0148-0227    

DOI:10.1029/JC086iC01p00439

年代:1981

数据来源: WILEY

摘要:

Eddy correlation measurements of water vapor, heat, and momentum fluxes have been made at a fixed tower near the water's edge on a low, sand island. The evaporation data collected extend the range of conditions to cooler water (larger Bowen ratio) and include cases of stable stratification and downward vapor flux. The evaporation coefficientCEhas a value of 1.3 × 10−3in neutral conditions, varies with stability in accordance with accepted empirical profile laws, and increases significantly with increasing wind speed at this shoal location. The Bowen ratio of sensible to latent heat flux varies widely with meteorological conditio

ISSN:0148-0227    

DOI:10.1029/JC086iC01p00449

年代:1981

数据来源: WILEY

摘要:

Previous measurements of small bubbles in the near‐surface ocean are summarized and are reviewed to obtain variations of bubble populations and size distributions with depth and wind velocity, to explore mechanisms of bubble production, and to suggest further studie

ISSN:0148-0227    

DOI:10.1029/JC086iC01p00457

年代:1981

数据来源: WILEY

摘要:

Spectral and integrated solar reflectance of nonhomogeneous snowpacks are derived assuming surface reflection of direct radiation and subsurface multiple scattering. For surface reflection, a bidirectional reflectance distribution function derived for an isotropic Gaussian faceted surface is considered, and for subsurface multiple scattering an approximate solution of the radiative transfer equation is studied. Solar radiation incident on the snowpack is decomposed into direct and atmospherically scattered radiation. Spectral attenuation coefficients of ozone, carbon dioxide, water vapor, aerosol, and molecular scattering are included in the calculation of incident solar radiation. Illustrative numerical results are given for a case of North American winter atmospheric condition. The calculated dependence of spectrally integrated directional reflectance (or albedo) on solar elevation is in qualitative agreement with available observations.

ISSN:0148-0227    

DOI:10.1029/JC086iC01p00465

年代:1981

数据来源: WILEY

摘要:

Individual Seasat altimeter profiles in the western North Atlantic have been differenced with the best available geoid model to remove the gravitational component. The resulting sea surface height profiles compare remarkably well with independent oceanographic observations. The Gulf Stream is clearly apparent in each profile as a 1‐ to 2‐m step, and known positions of cyclonic and anticyclonic rings correspond with depressions and elevations, respectively, with amplitudes as large as 95 cm. Some of the most important altimeter data for analyzing the dynamic ocean signal were gathered during the last month of the mission when the same ground track was repeated every 3 days. These data allow detailed examination of time‐varying ocean phenomena, since the gravitational component is time‐invariant. One set of collinear passes clearly shows a cyclonic ring as it moves out from underneath the spacecraft's track, an event which was simultaneously observed with the aid of a satellite‐tracked surface buoy. Another striking feature seen in the altimeter data set is the apparent variability exhibited by the Gulf Stream. On time scales of a few days, surface transport indicated by the sea surface height difference across the stream varied by nearly 30%, and over the entire 3‐month period much larger fluctuations were observed, suggesting significant changes in total mass transport. Altimetry may provide an effective means of determining the time and space scales associated with these

ISSN:0148-0227    

DOI:10.1029/JC086iC01p00473

年代:1981

数据来源: WILEY

摘要:

A brief review is given of the spatial and temporal pattern of sea surface temperature (SST) observations for the southern hemisphere. An analysis is made of 20 years (1950–1969) of observations of mean monthly SST for each degree square along the shipping routes, and relative variability is assessed on seasonal, latitudinal, and geographical bases. Highest variability occurs in oceanic regions of the western boundary currents, of current confluence, of upwelling, and also of convergence of low‐level atmospheric flow, notably in the central South Pacific. Within the data limitations the relative areas of above‐ and below‐normal SST are measured for selected tropical ocean regions near Australia for 6 years of extremely high and low extent of annual continental rainfall and for transitions from very dry years to very wet years and vice versa. The 3 extremely dry years are found to occur with an average reduction of some 14% in the area of above‐normal SST as compared with the 3 extremely wet years; the corresponding regional seasonal mean atmospheric pressure is above normal in dry years and below normal in wet years. The greatest interannual changes in rainfall extent are also accompanied by corresponding transitions in the area of above‐normal SST. Evidence suggests that the extent of above‐normal SST over the whole ocean (including higher latitudes) surrounding continental Australia may be closely associated with extreme r

ISSN:0148-0227    

DOI:10.1029/JC086iC01p00485

年代:1981

数据来源: WILEY

摘要:

Time‐dependent global warming due to increasing levels of atmospheric carbon dioxide has been estimated by employing an ocean‐land global climate model. Ocean heat capacity is incorporated by means of a global ocean model having a 70 m deep mixed layer, with heat being transported from the mixed layer to deeper waters by eddy diffusion. The time‐dependent increase in atmospheric CO2, from 1860 to 2025, is taken from carbon‐cycle models. The model results suggest that ocean heat capacity will produce a lag in CO2‐induced global warming of about 2 decades. For example, without inclusion of ocean heat capacity the model predicts that an increase in global surface temperature of 1°C, relative to 1860, will occur by 1988. But when ocean heat capacity is included, the 1°C warming is delayed until 2006–2012, this range of times corresponding to no land‐ocean advective coupling (2006) and complete land‐ocean coupling (2012). By 2025, when the assumed atmospheric CO2content is twice the 1860 value, the model predicts global warming of 1.5°–1.8°C, in contrast to 3.1°C when ocean heat

ISSN:0148-0227    

DOI:10.1029/JC086iC01p00498

年代:1981

数据来源: WILEY

摘要:

The Viking Mars landers contain meteorological instrumentation to measure wind, temperature, and pressure but not atmospheric water content. The landings occurred during local summer, and it was observed that the nocturnal temperature decrease at sensor height (1.6 m) did not exhibit a uniform behavior at either site. It was expected that the rate of decrease would gradually slow, leveling off near sunrise. Instead, a leveling occurred several hours earlier. Temperature subsequently began a more rapid decrease which slowed by sunrise. This suggested that the temperature sensors may be detecting the frost point of water vapor. Analysis of alternative hypotheses demonstrates that none of these are viable candidates. The frost point interpretation is consistent with other lander and orbiter observations, with terrestrial experience, and with modeling of Mars' atmospheric behavior. It thus appears that the meteorology experiment can help provide a basis toward understanding the distribution and dynamics of Martian water vapor.

ISSN:0148-0227    

DOI:10.1029/JC086iC01p00503

年代:1981

数据来源: WILEY