Frontal zone

Because at higher latitudes the coriolis force deflects wind to a greater extent than in the tropics, winds become much more zonal (flow parallel to lines of latitude). Also in contrast to the persistent circulation of the tropics, the mid-latitude circulations are quite transient. There are large temperature contrasts, and temperature may vary abruptly over relatively short distances (frontal zones). In these regions of large temperature contrast, potential energy is frequently released and converted into kinetic energy as wind. Near the surface there are many closed pressure sys-... 

The southern flank of the upwelling CDW sinks around the continent of Antarctica to become AABW The northern flank of upwelling CDW is transported by surface currents, first into the polar frontal zone (PFZ) where AAIW forms, and then into the subantarctic zone (SAZ ) where SAMW forms. At these latitudes, dust deposition is high enough to reduce iron limitation of the diatoms. As the surfece waters move northward. 

Triggered by planetary pressure gradients, large-scale transfers of air masses occur which differ in terms of their energy or humidity content. When they collide, this creates frontal zones as the warmer, hghter (or even more humid) air rises above the colder air. This process can result in condensation and longer-lasting precipitation (Fig. 2b). 

The 6-hourly precipitation distribution for the January storm, shown in Figure 9, reflects the difference in the dynamics processes of the frontal zone between the two storms. The isohyets show an increasing 6-hourly precipitation rate as the front moved southward, reaching a maximum of over 25 mm. per six hours near San Diego which was about twice that observed in northern California, opposite the trend noted in the latitudinal distribution for the November storm. 

An analysis of the temperature distribution in a mold (Fig. 4.54) at the final moment of filling for two reactive systems with different values of G shows that the temperature along the central line increases monotonically downstream (at distance x) from the inlet nozzle. At high values of the gelation criterion, the temperature at locations close to the injection nozzle is maximum near the mold wall. Moving down stream, the position of the temperature maximum shifts to the center, except at the frontal zone. Here the temperature is nearly constant, because the major part of the... 

This equation can be used as a basis for calculating the velocity components in the plane front zone. Analysis of this equation shows that, at a distance x = H from the surface of the piston, the flow can be treated as unidimensional to within an error of less than 1 %. Then, based on this result, we can assume that the length of the front zone If (Figs. 4.52 and 4.58) equals H and that the line dividing the stream into main and frontal zones is positioned at this distance from the front. The stream can be treated as unidimensional up to this line. 

Fig. 4.59 illustrates the flow pattern determined by Eqs (4.45) and (4.47). The distribution of the velocity vectors is shown for the case when the axial velocity component equals (ux - 1). Eqs. (4.45) and (4.47) allow us to find temperature and degree of conversion distributions in the frontal zone based on the fundamental balance equations. These equations differ from Eqs. (4.36) and (4.47) because they take into account convective heat transfer along the z-direction. The dimensionless forms of the main determining equations are as follows energy balance... 

This system of equations allows us to take account of the flow in the frontal zone and the influence of the fountain effect on the distributions of variables in the main stream zone. The equations for this rather complicated model can be solved numerically by computer. Comparison of the calculations with experimental data shows that the maximum deviations of the predicted values from the experimental points do not exceed 15 % (Fig. 4.60). 

Figure 6.9 Theoretical diagram of fluid mud formation and disruption at the frontal zone showing (a) neap tide stratified fluid mud formation—with strong vertical salinity gradient and (b) spring tide mixed or mobile fluid mud formation—with strong horizontal salinity gradient. (Modified from Kineke et al., 1996.)...

The mixing zone usually includes an area of the most intense interaction and mixing of river and sea water, where horizontal and vertical gradients of hydrological and hydrochemical characteristic, and primarily water salinity, are maximum. This area is called frontal zone. 

The sea boundary of a river mouth area or the outer boundary of an open nearshore zone of a river mouth is defined by a maximum propagation distance of the outer (marine) part of the frontal zone into the sea, when river and sea waters are mixed in the surface layer. This boundary is arbitrarily defined by the location of the isohaline equalling about 90% of water salinity in the adjacent part of the sea at the river high-flow period. 

Main Frontal Zone in the Layer of the Main Pycnocline. 246... 

Table 3 Climatic parameters (mean values standard deviations) of the Black Sea main frontal zone in salinity field at a depth of 100 m on standard sections in February and August. For the section locations, see Fig. 1. Xm3x distance from coast (km) dS/dxm3X size (psukm ) of maximum along section salinity gradient X0ffshore distance from coast (km) of the offshore MFZ edge Xinshore the same for the inshore MFZ edge...

Figure 1 Frontal zone profile of electroosmotic flow in open-tubular capillary column. A rectangular capillary (1 mm x 50 pm and 16.4 cm long) was used. Colored sample methanol solution of 0.1 mM Rohdamine 6G. Frontal zone profiles of 0, (white) and 02 (black) were successively taken. The period between two zones was 11.44 s. The distance between two frontal zones was 6.52 mm. Flow velocity of the center was 0.57 mm/s. The ratio of the flow velocities given by (flow velocity at half-radius)/(flow velocity at center) was 1.0027. The retarded speed of the flow velocity at the center compared to that at the corner was only 0.4%. Although the same scale was used for the X and Y axes, there are time intervals between 0, and 02 in (A). Figure (B) was obtained by the combination of 0, and 02 (overlapping two frontal zone profiles at the corner). Therefore the right and left profiles correspond to 0, and 02, respectively. Applied voltage, 1.59 kV current, 120 nA.

Figure 2 Frontal zone profile of electroosmotic flow in packed capillary column. The capillary column was packed with silica gel (particle diameter 5 pm). The medium was cyclohexanol. As cyclohexanol and silica gel have similar refractive indexes, the column looked transparent. The lower photo was taken 31 s after the upper one.

Figure 3 Progress of frontal zone under application of pulsed electric field. A pulsed electric field was applied in 2-s cycles (electric field was applied for half of the period, and was stopped for the other half). Frontal zone positions were measured from the digital picture on a CRT. The perpendicular line shows the direction of movement of the frontal zone, and 1 mm in length is equal to 167 pixels. The horizontal line shows the time, and the minimum time scale observed is equal to one-fifteenth. A round open-tubular capillary column 75 pm in diameter and 28 mm in length was used. Applied voltage, 1 50 V. Colored sample methanol solution of 1 mM Rhodamine 6G.

Franck, V. M., Brzezinski, M. A., Coale, K. H., and Nelson, D. M. (2000). Iron and srhcic acid concentrations regulate Si uptake north and south of he Polar Frontal Zone in the Pacific Sector of the Southern Ocean. Deep Sea Res. II47, 3315—3338. 

Elskens, M., Baeyens, W., Cattaldo, T., Dehairs, F. (2002). N uptake conditions during summer in the Subarctic and Polar Frontal Zones of the Australian sector of the Southern Ocean. J. Geophys. Res, 107(Cl 1), 3182, doi 10.1029/2001JC000897. 

Altabet, M. A., and Frangois, R. (2001). Nitrogen isotope biogeochemistry of the Polar Frontal Zone at 170 degrees W. Deep — Sea Research II48, 4247—4273. 

Gervais, F., RiebeseU, U., and Gorbunov, M. (2002). Changes in primary productivity and chlorophyll a in response to iron fertilization in the Southern Polar Frontal Zone. Limnol. Oceanogr. 47, 1324—1335. 

Step-function space series were initially divided into three segments inshore data, frontal zone data, and offshore data. Frontal zone data were not used in the subsequent statistical analyses for the reasons just cited. The inshore and offshore data segments were tested for the presence of trends and then for stationarity with the procedures given by Bendat and Piersol (46). In some instances, the inshore and offshore data segments were further subdivided in an attempt to satisfy the conditions of weakly stationary data. 

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