Dynamics of near-shore vortices

This work addresses two problems: 1) the dispersion induced by a cloud of vortices near a straight coast-line when the bottom is flat and the coastal boundary is a vertical plane or when the bottom is a planar slope; 2) the dynamics of vortices moving over a planar sloping bottom. Vortices near a vertical boundary are studied by the well-known method of images. For a plane sloping bottom we describe and develop a model, first introduced by Peregrine (1996) that uses a sector of a vortex ring to model a vortex in a wedge of fluid, where the wedge is formed by the water surface and by the planar sloping bottom. Numerical simulations using these free-slip analytical models are used to investigate the dispersion of vorticity and of a passive tracer induced by clouds of vortices. The results of the two models are compared. The dispersion of vortices and particles is mainly affected by the formation of vortex dipoles. The shoreline sets a preferential direction for the dispersion process and the dispersion normal to the shoreline is generally smaller, or bounded when the vortices forming the dipole have different absolute circulation. The dispersion of particles is generally smaller than the dispersion of vortices. In the second part of this work the analytical model of Peregrine (1996) for vortices moving over a planar slope at an angle a with the horizontal is tested against a set of laboratory experiments. Experiments were made by studying the dynamics of a vortex dipole moving towards a planar sloping beach. We measured the minimum distance from the shoreline reached by the vortices and their along-shore speed. The parameter ranges examined were 3º≤α≤45º, and 1×103≤Re≤6×103 (where Re is the Reynold's number of the vortices). We find a good agreement between the predictions and the observations when Re >~ 1500

On the use of the method of images to investigate nearshore dynamical processes

This note describes how the method of images may be used to determine the motion and evolution of two related kinds of phenomena within a wedge of inviscid fluid. The image field of a curved vortex within a wedge with vortex lines lying along sectors of circles around the apex of the wedge is that segment of a complete vortex ring which remains outside the wedge and of which the curved vortex forms a part. The image system can be used to describe the motion, interaction and stability of single or multiple vortices within the wedge. Axisymmetric jets form the image system for flow parallel to the edge of the wedge, akin to alongshore currents. Knowledge of the instability of jets provides information about the evolution of waves in the wedge domain. Existing results on the motion and instability of single or multiple co-axial ring vortices and of waves and instabilities in jets may be applied to describe the evolution of low Froude number eddies and waves in alongshore flow over a steadily shelving sea bed

Winter conditions in the Irminger Sea observed with profiling floats

Temperature/salinity profiles collected between 1994 and 2003 with profiling floats in the North Atlantic subpolar gyre are analyzed to investigate the hydrographic conditions in winter in the Irminger Sea. The salinity data can be calibrated against accurate profiles from ships obtained mostly during summer months and the resulting float profile salinity accuracy is of the order of 0.015. Between 1997 and 2003, when the North Atlantic Oscillation (NAO) index was generally low, the potential temperature and salinity of the Labrador Sea Water (LSW) core observed by the floats showed a positive trend, an indication of little or no deep convection. The float data show that in the Irminger Sea the thermal energy of the water column reaches the lowest values south and southwest of Cape Farewell, a place where deep convective events are likely to occur. The geostrophic velocity field at 15 m computed from drifting buoys and satellite measurements of sea level shows, for the same area, mean currents below 0.1 m s-1 and low levels of eddy kinetic energy. These factors, together with recent estimates of winter air-sea heat fluxes as high as 500 W m-2 for this region, are exploited to explore the evolution of the surface mixed layer using several one-dimensional models. The results suggest that the typical thickness of the surface mixed layer at the end of winter is of the order of 400 m. This is similar to observed values from floats

Habitat requirements and population size of the Javan plover Charadrius Javanicus (Aves, Charadriidae) on Java, Indonesia

Nach aktuellem Wissenstand erstreckt sich die Verbreitung des Java Regenpfeifers (Charadrius javanicus) überwiegend auf die Küstengebiete Javas. Diese Arbeit versucht artspezifische Habitats-anforderungen zu quantifizieren und aktuelle Populationsgrößen zu ermitteln. Während der Erhebung eines 0,5 km langen Transektes entlang von 72,5 km Küstenlinie wurden 218 Java Regenpfeifer - im Mittel (± SD) of 1,47 (± 2,64) Vögel pro 0,5 km Küstengebiet - erhoben. Höchste Dichte wurde an der Südküste Javas gefunden, wobei die Dichte des Java Regenpfiefer signifikant zwischen unterschiedlichen Habitatstypen variierte. Breite (>50m) kleinkörnige sandige Strände waren das bevorzugte Habitat. Neben dem bevorzugten Sandstrand-Habitat des Java Regenpfeifers spielte die Strand- bzw Strandgut-breite eine wichtige Rolle bei der Zunahme der Dichte des Vogels. Effekte durch menschliche Störung konnte nicht nachgewiesen werden. Wir stellten einen schwacher Trend zur Abnahme der Individuenzahl bei fehlender pflanzlicher Bedeckung fest. GLMs hat gezeigt, daß die Strandbreite die beste Erklärungsvariable für die Vorhersage des Vorkommens des Java Regenpfeifers innerhalb eines 500m Transektes ist. Entlang von 76 Transekten an Sandstrand-Habitaten inklusive Lagunen wurden 205 Java Regenpfeifer oder 5,39 Individuen pro Kilometer Küstenlinie beobachtet. Insgesamt 2000 Vögel wurden für die Küste Java erhoben, wobei 125 km durch menschliche Siedlungen stark geprägt sind. Dadurch könnten sich geringere Dichten in anthropogen geprägten Küstenabschnitten ergeben. Diese Schätzung beinhaltet nicht jenen Teil der Population, welcher in künstlich angelegten Fischteichen vorkommt, welche ein wichtiges Sekundärhabitat für die Art darstellt. Außerdem scheint es als ob die Art momentan nicht unmittelbar gefährdet sei, dennoch sollte die Population in naher Zukunft kontinuierlich erfasst werden bevor weitere küstennahe Entwicklung oder Intensivierung der Fischteich Industrie eine ernsthafte Bedrohung für das Tier darstellen.Based on current knowledge the distribution of the Javan Plover Charadrius javanicus is predominantly restricted to Java, where it occurs in coastal habitats. This study tried to quantify the species´ habitat requirements and to contribute to estimating its actual population size. During a survey of 0.5 km long transects along a total of 72.5 km of coastline, a total of 218 Javan Plovers corresponding to a mean (± SD) of 1.47 (± 2.64) birds per 0.5 km shoreline was recorded. However, the density of Javan Plovers differed significantly between surveyed coastal regions. Highest abundances were found on the south coast of Java. Furthermore, abundances of Javan Plovers differed significantly between coastal habitats. Wide (>50m), small-grained sandy beaches were the preferred habitat. The likelihood of Javan Plover occurrence on small-grained beaches increased with beach and flotsam width, while no effect of human disturbance could be found. A weak trend of a decline in Plover numbers towards beaches without any vegetation was found. GLMs indicated that beach width was the best explanatory variable for predicting the occurrence of Javan Plovers in 500 m transects. Along 76 transects of sandy beach habitat including lagoons, a total of 205 Javan Plovers or 5.39 individuals per 1 km shoreline were observed. A total of ca. 2000 birds were estimated for coastal habitats of Java. However, ca. 125 km are located very close to human settlements. Consequently, Javan Plovers may reach a much lower density in some coastal areas. This estimate does not include the part of the population which occurs at fishponds, which may represent an important artificial habitat for this species. The species does not yet seem to be endangered, nevertheless its populations have to be carefully monitored due to the risk of further coastal development and intensification of fishpond industry becoming a serious threat to the species

The Nascent Kuroshio of Lamon Bay

A northward flowing current, emanating from the North Equatorial Current (NEC) bifurcation at the Philippine margin, enters Lamon Bay along Luzon's eastern coast. There the NEC tropical water masses merge with subtropical water of the western North Pacific to form the Kuroshio. A northward flowing western boundary current is first observed near 16.5°N, marking the initiation of the Kuroshio. The current feeding into the nascent Kuroshio of Lamon Bay is bracketed by an anticyclonic dipole to its northeast and a cyclonic dipole to its southwest. Ship based observational programs in the spring seasons of 2011 and 2012, detect a shift of the Lamon Bay thermohaline stratification with marked enrichment of NEC tropical thermocline water in 2012 relative to a dominant western North Pacific subtropical stratification of 2011. Temperature - salinity time series from moorings spanning the two ship based observations, identify the timing of the transition as December 2011. The NEC bifurcation was further south in May 2012 than in May 2011. We suggest that the more southern bifurcation in May 2012 induced increased NEC thermocline water injection into Lamon Bay and nascent Kuroshio, increasing the linkage of the western North Pacific subtropical and tropical thermoclines. This connection was reduced in May 2011 as the NEC bifurcation shifted into a more northerly position and western North Pacific subtropical thermocline dominated Lamon Bay stratification

Can we detect submesoscale motions in drifter pair dispersion?

Author Posting. © American Meteorological Society, 2019. This article is posted here by permission of American Meteorological Society for personal use, not for redistribution. The definitive version was published in Journal of Physical Oceanography 49(9), (2019): 2237-2254, doi: 10.1175/JPO-D-18-0181.1.A cluster of 45 drifters deployed in the Bay of Bengal is tracked for a period of four months. Pair dispersion statistics, from observed drifter trajectories and simulated trajectories based on surface geostrophic velocity, are analyzed as a function of drifter separation and time. Pair dispersion suggests nonlocal dynamics at submesoscales of 1–20 km, likely controlled by the energetic mesoscale eddies present during the observations. Second-order velocity structure functions and their Helmholtz decomposition, however, suggest local dispersion and divergent horizontal flow at scales below 20 km. This inconsistency cannot be explained by inertial oscillations alone, as has been reported in recent studies, and is likely related to other nondispersive processes that impact structure functions but do not enter pair dispersion statistics. At scales comparable to the deformation radius LD, which is approximately 60 km, we find dynamics in agreement with Richardson’s law and observe local dispersion in both pair dispersion statistics and second-order velocity structure functions.This research was supported by the Air Sea Interaction Regional Initiative (ASIRI) under ONR Grant N00014-13-1-0451 (SE and AM) and ONR Grant N00014-13-1-0477 (VH and LC). Additionally, AM and SE thank NSF (Grant OCE-I434788) and ONR (Grant N00014-16-1-2470) for support; VH and LC were further supported by ONR Grant N00014-15-1-2286 and NOAA GDP Grant NA10OAR4320156. We thank Joe LaCasce, Dhruv Balwada, and one anonymous reviewer for helpful comments and discussions that significantly improved this manuscript. The authors thank the captain and crew of the R/V Roger Revelle. The SVP-type drifters are part of the Global Drifter Program and supported by ONR Grant N00014-15-1-2286 and NOAA GDP Grant NA10OAR4320156 and are available under http://www.aoml.noaa.gov/phod/dac/. The Ssalto/Duacs altimeter products were produced and distributed by the Copernicus Marine and Environment Monitoring Service (CMEMS, http://www.marine.copernicus.eu)

Coupling stem water potential and soil water potential on irrigated and not irrigated vines: preliminary results for Vitis vinifera L. cv Teroldego

Improving wine quality necessitates precise control over plant water stress, which requires accurate scheduling of irrigation based on the plant's water status and the soil's water availability. The aim of this experiment is to monitor the water status of grapevines and soil in both irrigated and not-irrigated conditions to quantify differences in the plant's physiological response and yield. In addition, novel microtensiometer probes for measuring continuously the Stem Water Potential were tested for efficacy. These probes were coupled with a handcrafted tensiometer to monitor the Soil Water status and at the end of the season all the yield was analyzed to determine the main oenological parameters driving the final quality of the musts. Initial findings indicate that the microtensiometers gave effective estimates of the vines’ water status, revealing rapid plant responses to water inputs and atmospheric changes. Notably for the experiment, soil moisture exceeded field capacity under irrigated vines before irrigation, suggesting potential water loss through deep percolation, and both the irrigated and not-irrigated vines were in water comfort for all the vegetative season without any detriment both in production and quality

Serum Albumin in Patients Affected by Gynecological Cancers: Can It Have a Future Role in Prognostic Index or Nomogram?

An interesting original research entitled "Serum albumin as a predictor of survival after interval debulking surgery for advanced ovarian cancer: a retrospective study" has been recently published ..