摘要:

A technique is presented which improves existing methods of calculating sea ice concentrations from microwave radiances by reducing weather‐related effects over open ocean areas and in the vicinity of marginal sea ice zones. Winds, atmospheric water vapor, cloud liquid water, and rain increase the microwave emission over these regions and thus result in erroneous values of computed sea ice concentration. The method described is based on the microwave spectral properties of sea ice and ice‐free ocean and utilizes ratios of the polarized radiances at the 0.81‐cm (37 GHz) and 1.7‐cm (18 GHz) wavelengths. Following a discussion of the physical basis for this technique, examples are provided which demonstrate its utility. While the technique was developed for use with the Nimbus 7 scanning multi‐channel microwave radiometer data, it is applicable also to data from other microwave radiometers operating in a similar wavelen

ISSN:0148-0227    

DOI:10.1029/JC091iC03p03913

年代:1986

数据来源: WILEY

摘要:

Imagery from the shuttle imaging radar‐B experiment as well as other satellite and meteorological data are examined to learn more about the open sea ice margin of the Weddell‐Scotia Seas region. At the ice edge, the ice forms into bandlike aggregates of small ice floes similar to those observed in the Bering Sea. The radar backscatter characteristics of these bands suggest that their upper surface is wet. Further into the pack, the radar imagery shows a transition to large floes. In the open sea, large icebergs and long surface gravity waves are discernable in the radar ima

ISSN:0148-0227    

DOI:10.1029/JC091iC03p03920

年代:1986

数据来源: WILEY

摘要:

The transfer of weakly soluble gases between the atmosphere and seas or lakes is controlled by liquid‐phase molecular and turbulent diffusion mechanisms, which essentially depend on wind velocity and gas Schmidt number. A distinct change in regime is observed around 2–3 m s−1, when capillary waves appear, which present models cannot explain. We suggest relating turbulent diffusivity with (1) possible motions close to a “free” liquid‐gas interface, (2) mean current distribution in that region, and (3) capillary wave spectra. Resulting transfer velocities explain laboratory and field data at low and moderate

ISSN:0148-0227    

DOI:10.1029/JC091iC03p03925

年代:1986

数据来源: WILEY

摘要:

Global temperature records extending about 100 years into the past display interannual fluctuations of a few tenths °C on a variety of time scales. A number of previous model simulations have employed anthropogenic CO2warming, solar variability, and volcanic aerosol loading as external forcings to account for major features of these records. We develop a simple system using a one‐dimensional, upwelling‐diffusion world ocean model that incorporates a nonlinear linkage between the global surface temperature and the large‐scale oceanic overturning. Interesting dynamic behavior was discovered, in particular, internal self‐excited oscillations with parameter‐dependent periods of the approximate order of a hundred years exhibiting surface temperature changes of the order of ±0.5°C. The largest features of the northern hemispheric surface land temperature record can be simulated with our climate and deep ocean feedback formulation and CO2forcing alone. One would conclude that internal processes of this type can indeed produce temperature changes as powerful and as rapid as those produced by the above mentioned external forcings, and our results indicate that more work is needed on the role of nonlinear coupling between surface temperature and ocean dynamics in transient cl

ISSN:0148-0227    

DOI:10.1029/JC091iC03p03944

年代:1986

数据来源: WILEY

摘要:

Kootenay Lake is a long (100 km), deep (140 m), dimictic lake in southeastern British Columbia. Internal waves were observed over an 18‐month period using three thermistor chains moored along the major axis of the lake. To characterize their seasonal aspects, four types of oscillations are recognized: (1) classical seiches with amplitudes of 10–30 m and periods of 1–2 weeks, (2) intrabasin waves with periods of 2–4 days, (3) large‐amplitude waves resembling nonlinear surges, and (4) high‐frequency waves associated with both the internal surge and large‐amplitude internal seiche motions. The periods of the major components of the internal wave field are determined mainly by morphometry but vary seasonally with stratification. Thus the wind, which not only forces internal waves but can also modify stratification, is important. In large lakes like Kootenay, the thermal structure may vary not only spatially but also temporally at periods comparable to those of the internal waves themselves. Hence the shape and frequency of these waves may be altered as they pass thr

ISSN:0148-0227    

DOI:10.1029/JC091iC03p03951

年代:1986

数据来源: WILEY

摘要:

Intermediate‐scale shear waves are ubiquitous in the world's ocean. They are the horizontal wavy movement along the shear interface having a typical wavelength of 100 km. Based on a simple theoretical model using the standard shallow water geophysical fluid dynamic equation, we found that these phenomena can be modeled by a kind of stable shear wave triggered by external forces, such as wind stress. Our results indicate that their amplitudes should be directly proportional to the wind stress, and the relationship between the phase speeds of the waves and their wave numbers can be expressed by a parabolic equation. Comparisons between theoretical results and data derived from the satellite IR images show good agreemen

ISSN:0148-0227    

DOI:10.1029/JC091iC03p03959

年代:1986

数据来源: WILEY

摘要:

Observations of horizontal velocities just outside the surf zone on two natural beaches show unexpected time lags between the onshore/offshore currents and the longshore currents at incident wave frequencies. These time lags, typically around 20 s, appear to have been first noticed by Katoh (1981) in data from a beach in Japan. A number of possible hypotheses to explain these time lags are examined. Of these, propagation of secondary waves formed by reflection or diffraction at a point alongshore from the measurement site seems most able to explain the observations. This suggests a significance for reflected/diffracted waves, some distance from breakwaters or headlands, which has not previously been recognized in field studies. However, a number of questions remain that will only be resolved by further field data, particularly from beaches far removed from end effects.

ISSN:0148-0227    

DOI:10.1029/JC091iC03p03967

年代:1986

数据来源: WILEY

摘要:

The nonlinear Schrödinger equation derived by Liu and Tsay (1984) is used to investigate the forward scattering of the second‐order Stokes waves by a depth discontinuity. It is shown that, due to nonlinearity, stem waves develop along a line caustic. The structure of the present stem waves is similar to that found by Yue and Mei (1980) along the wall of a thin wed

ISSN:0148-0227    

DOI:10.1029/JC091iC03p03979

年代:1986

数据来源: WILEY

ISSN:0148-0227    

DOI:10.1029/JC091iC03p03983

年代:1986

数据来源: WILEY