Secondary flow caused by differential roughness,Langmuir circulations,and their effect on the development of sand ribbons

The process of Differential Roughness Secondary Flow (DRSF), hitherto little recognized, recently was demonstrated in a wind tunnel and in a flume. It is suggested here the DRSF may, in the natural environment, play an important part in the persistence and sharp definition of sand ribbons, previously initiated by other processes. In 1980 Karl described a series of sand ribbons, alternating with exposed substrate, which he attributed to the effect of Langmuir circulations. Although Langmuir Circulation Secondary Flow (LCSF) may indeed, in some cases, initiate sand ribbons, the sharply-defined edges typical of these features are explained better by DRSF.     

Statistical analysis of a global photochemical model of the atmosphere

This is a study of the sensitivity of model results (atmospheric content of main gas constituents and radiative characteristics of the atmosphere) to errors in emissions of a number of atmospheric gaseous pollutants. Groups of the model variables most dependent on these errors are selected. Two variants of emissions are considered: one without their evolution and the other with their variation according to the IPCC scenario. The estimates are made on the basis of standard statistical methods for the results obtained with the detailed onedimensional radiative—photochemical model of the Main Geophysical Observatory (MGO). Some approaches to such estimations with models of higher complexity and to the solution of the inverse problem (i.e., the estimation of the necessary accuracy of external model parameters for obtaining the given accuracy of model results) are outlined.     

Well log interpretation and seismic character of the cenozoic sequence in the northern Alboran Sea

Seismic stratigraphic and main lithological features of the sedimentary cover overlying the basement of the Alboran Sea were established via the analysis of commercial multichannel seismic surveys, geophysical well logs, and well data. Six seismic stratigraphics units (VI to I), bounded by unconformities, form the marine sediments that range in age from early Miocene to Quaternary. They are dated by extrapolation of commercial drilling results from the northern Alboran Sea. Volcanic activity is recorded within sedimentary sequences of units V to II. Undercompaction features are detected in the two basal units.     

Atmospheric forcing of fine-sand transport on a low-energy inner shelf: south-central Louisiana,USA

Hydrodynamic and sediment transport measurements from instrumentation deployed during a 54-day winter period at two sites on the Louisiana inner shelf are presented. Strong extratropical storms, with wind speeds of 7.8 to 15.1 m s^-1, were the dominant forcing mechanism during the study. These typically caused mean oscillatory flows and shear velocities about 33% higher than fair weather (averaging 12.3 and 3.2 cm s^-1 at the landward site, and 11.4 and 2.7 cm s^-1 at the seaward site, respectively). These responses were coupled with mean near-bottom currents more than twice as strong as during fair weather (10.3 and 7.5 cm s^-1 at the landward and seaward sites, respectively). These flowed in approximately the same direction as the veering wind, causing a net offshore transport of fine sand. Weak storms were responsible for little sediment transport whereas during fair weather, onshore sand transport of approximately 25-75% of the storm values appears to have occurred. This contradicts previous predictions of negligible fair-weather sediment movement on this inner shelf.     

Reversing Water Exchange Patterns at the Entrance to a Semiarid Coastal Lagoon

Water velocity and density profiles were obtained in late-spring and late-winter to document reversing mean circulation patterns at the entrance to a semiarid coastal lagoon, the Bay of Guaymas, in the Gulf of California, Mexico. The lagoon is shallow but the bathymetry at its entrance is similar to that of temperate estuaries with an asymmetrically positioned channel flanked by shoals. In late-spring the mean circulation at the entrance to the lagoon was driven by horizontal density gradients that arose from excess evaporation over precipitation in the area as evidenced by water density profiles. The lagoon exported relatively warm (25·8 °C) and salty (36·2) water to the Gulf of California through the channel. This export was consistent with inverse estuarine circulation influenced by bathymetry. In late-winter, the circulation at the entrance of the lagoon was mostly driven by wind stress that blew from the northwest, roughly along the main axis of the lagoon. Relatively cool (16·0) °C) and less salty (35·1) water from the Gulf of California was driven into the lagoon within the channel. Density gradients inside the lagoon seem to have played a secondary role in driving the circulation. The late-winter circulation was then estuarine-like, with outflow in the direction of the wind over the shallow areas and a compensatory inflow appearing in the channel as expected from theory of wind-driven flow over bathymetry. This estuarine-like circulation developed despite the lack of measurable freshwater input to the lagoon and was the opposite to that observed in late-spring. These observations then document a reversal in water exchange patterns from season to season in a semiarid coastal lagoon. The observations also constitute one of the few reported examples of flow over shoals driven in the same direction as the wind stress with a compensatory flow in the channel.     

Calibration of visual observations of wave period

Visual observations of wave properties are an important source of statistical information needed for the prediction of design and operational conditions of ocean structures. In particular, mean wave periods are important parameters for predicting the response of ocean structures. The existing calibration studies were based on data sets with a poor correlation between observations and measurements. The data set analysed here show a good correlation indicating the feasibility of collecting further good data sets to provide an adequate calibration to the existing statistical compilations of wave data.     

Theoretical wind wave frequency spectra in deep water——Ⅰ. Form of spectrum

In this part ot the paper theoretical wind-wave spectra nave been derived oy (I) expressing the spectrum in series composed of exponential terms; (2) assuming that the spectrum satisfies a high order linear ordinary differential equation; (3) introducing proper parameters in the spectrum; and (4) making use of some known charateristics of wind-wave spectrum, for instance, the law governing the equilibrium range. The spectrum obtained contains the zero order moment of the spectrum m0, the peak frequency ω0 and the ratio R =ω/ω0 (ω being the mean zero-crossing frequency) as parameters. The shape of the nondimensional spectrum S(ω) = ω0S(ω)/m0(ω=ω/ω0) changes with R and theoretically reduces to a Dirac delta function δ(ω-1) when R = 1. A spectrum of simplified form is given for practical uses, in which R is replaced by a peakness factor P=S(1).     

Effects of pulp bleach plant effluents on hepatic xenobiotic biotransformation enzymes in fish: Laboratory and field studies

The present preliminary report on studies of the influence of pulp bleach plant effluents on hepatic biotransformation enzymes in fish is a part of a major characterisation of biochemical and physiological effects of effluents from pulp industries in Sweden. Our studies on the xenobiotic biotransformation enzymes demonstrate, so far, that the pulp effluents have the potential to strongly induce 7-ethoxyresorufin-O-deethylase activity (EROD) in fish liver and that fish living in the receiving water of an effluent from a pulp bleach plant have induced hepatic EROD activities as well as higher hepatic UDP glucuronyltransferase activities than those living in an unpolluted area. It is thus apparent that measures of induction of biotransformation enzymes in fish liver may be a useful approach in monitoring the presence of potential hazardous compounds released from pulp industries.