Distribution Of Curl Research Articles

Cyclonic circulation and climatology of SST, CHL and wind stress curl in a semi-enclosed bay (Bahía de La Paz, Gulf of California)

The first direct current observations (with LADCP and surface drifters) in Bahía de La Paz, a bay in the southwestern Gulf of California (GC), concur with previous reports that the main dynamical feature during summer is a closed cyclonic circulation. However, we found that geostrophic calculations overestimate the speed of the orbital velocity: actual speeds (0.20-0.25 m s-1) were ~25-40% lower than those estimated from geostrophic balance (0.25-0.35 m s-1). The reason is that the centrifugal force cannot be neglected in this case. The mean rotation period during ship-borne observations in August 2004 was ~1.4 days, but it varied during the time that surface drifters were inside the bay, from ~1-2 days in June-July to ~2.5-3 days in September-October. The analysis of satellite data (wind velocity, sea surface temperature and chlorophyll) show that from May to September the wind stress curl is strong and cyclonic, and the surface of the bay is cooler and richer than the adjacent Gulf of California waters, which could be attributed to the positive wind stress curl. This positive wind stress curl on the bay is part of a larger-scale positive wind stress curl distribution that surrounds the southern part of the Baja California Peninsula during summer, probably enhanced in the bay by local topography features. Although there is an exchange of water between the bay and the GC, its effect on the dynamics is poorly known.

Simulation of leaf curl disease dynamics in chili for strategic management options

Leaf curl, a whitefly-borne begomovirus disease, is the cause of frequent epidemic in chili. In the present study, transmission parameters involved in tripartite interaction are estimated to simulate disease dynamics in a population dynamics model framework. Epidemic is characterized by a rapid conversion rate of healthy host population into infectious type. Infection rate as basic reproduction number, R0 = 13.54, has indicated a high rate of virus transmission. Equilibrium population of infectious host and viruliferous vector are observed to be sensitive to the immigration parameter. A small increase in immigration rate of viruliferous vector increased the population of both infectious host and viruliferous vector. Migrant viruliferous vectors, acquisition, and transmission rates as major parameters in the model indicate leaf curl epidemic is predominantly a vector -mediated process. Based on underlying principles of temperature influence on vector population abundance and transmission parameters, spatio-temporal pattern of disease risk predicted is noted to correspond with leaf curl distribution pattern in India. Temperature in the range of 15–35 °C plays an important role in epidemic as both vector population and virus transmission are influenced by temperature. Assessment of leaf curl dynamics would be a useful guide to crop planning and evolution of efficient management strategies.

Effect of the Leveling Conditions on Residual Stress Evolution of Hot Rolled High Strength Steels for Cold Forming

In order to investigate the effect of leveling conditions on residual stress evolution during the leveling process of hot rolled high strength steels, the in-plane residual stresses of sheet processed under controlled conditions at skin-pass mill and levelers were measured by cutting method. The residual stress was localized near the edge of sheet. As the thickness of sheet was increased, the residual stress occurred region was expanded. The magnitude of residual stress within the sheet was reduced as increasing the deformation occurred during the leveling process. But the residual stress itself was not removed completely. The magnitude of camber occurred at cut plate was able to be predicted by the residual stress distribution. A numerical algorithm was developed for analysing the effect of leveling conditions on residual stress. It was able to implement the effect of plastic deformation in leveling, tension, work roll bending, and initial state of sheet (residual stress and curl distribution). The validity of simulated results was verified from comparison with the experimentally measured residual stress and curl in a sheet.

Wind-driven variability in sea surface temperature front distribution in the California Current System

Simultaneous satellite-derived observations from 2002 to 2009 are used to quantify the relation between sea surface temperature (SST) fronts and ocean winds in the California Current System (CCS). An edge-detection algorithm is applied to SST observations to generate monthly maps of frontal probabilities. Empirical orthogonal decompositions reveal that the seasonal evolution of fronts in the CCS is strongly related to the seasonal evolution of coastal alongshore wind stress. The seasonal development of SST fronts is remarkably different to the north and to the south of Cape Mendocino, however. While fronts to the north of the cape extend for hundreds of kilometers from the coast peaking during summer and fall, when upwelling winds are stronger off northern California and Oregon, the region to the south of Cape Mendocino is characterized by high frontal activity during spring in a much narrower band close to the coast. Throughout the region, anomalies in the intensity of upwelling-favorable wind stress are followed by anomalies in frontal activity. The width and speed of the widening of the region of high frontal activity are also related to coastal alongshore wind stress. Interannual variability in the timing of the widening of the region of high frontal activity in the lee of Cape Blanco compared to the timing of the spring transition to upwelling-favorable winds may be related to the wind stress curl distribution in the lee of the cape. Stronger upwelling-favorable wind stress curl anomalies lead to early widening of the region of high frontal activity.

New model for predicting tensile strength and density of eucalyptus handsheets based on an activation parameter calculated from fiber distribution characteristics

Abstract The activation parameter developed is based on the fiber wall thickness distribution, fiber curl distribution, and water retention value of the unrefined fibers. The mechanical properties of paper that contain chemical pulp depend, among other things, on the free fiber segment activation between fiber-fiber crossings that is created during drying. Experimental data revealed that the degree of fiber swelling is responsible together with the fiber shape factor (curl) and fiber wall thickness for the extent of fiber network activation. The amount of bonding between fibers also affects fiber segment activation. Based on the experimental data, it was deduced that interfiber bonding ability of fibers, characterized as the water retention value, was mainly responsible for the development of handsheet density. Tensile index development was more affected by the morphology of fibers, which was the main determinant for high activation potential of fibers. Factor analysis was used to identify the main causes of variation for a refining data set of 20 Eucalyptus grandis samples. Three independent descriptors were found to be responsible for the majority of the variation: the bonding and activation factor, the factor of microcompressions, and the factor of fiber wall thickness and fiber curl. The activation parameter developed in this study can be used to determine the effect of fiber segment activation and inter-fiber bonding on the inplane mechanical properties of paper.

Assimilation of altimeter data into a quasigeostrophic ocean model using optimal interpolation and eofs

Abstract An ensemble of fraternal-twin experiments is used to assess the utility of optimal interpolation and model-based vertical empirical orthogonal functions (eofs) of streamfunction variability to assimilate satellite altimeter data into ocean models. Simulated altimeter data are assimilated into a basin-wide 3-layer quasi-geostrophic model with a horizontal grid spacing of 15 km. The effects of bottom topography are included and the model is forced by a wind stress curl distribution which is constant in time. The simulated data are extracted, along altimeter tracks with spatial and temporal characteristics of Geosat, from a reference model ocean with a slightly different climatology from that generated by the model used for assimilation. The use of vertical eofs determined from the model-generated streamfunction variability is shown to be effective in aiding the model's dynamical extrapolation of the surface information throughout the rest of the water column. After a single repeat cycle (17 days), the analysis errors are reduced markedly from the initial level, by 52% in the surface layer, 41% in the second layer and 11% in the bottom layer. The largest differences between the assimilation analysis and the reference ocean are found in the nonlinear regime of the mid-latitude jet in all layers. After 100 days of assimilation, the error in the upper two layers has been reduced by over 50% and that in the bottom layer by 38%. The essence of the method is that the eofs capture the statistics of the dynamical balances in the model and ensure that this balance is not inappropriately disturbed during the assimilation process. This statistical balance includes any potential vorticity homogeneity which may be associated with the eddy stirring by mid-latitude surface jets.

Genetic Analyses of Fleece Characteristics of Swedish Peltsheep

Abstract The study was conducted using about 93 000 records from the Swedish Sheep Recording Scheme (SRS) during the years 1983, 1985 and 1987. Fleece characteristics studied were: colour of fleece, size of curl, scores for colour, curl distribution and firmness, quality of hair and hair density. Litter size and age of lamb at assessment influenced almost all the fleece traits, and this was consistent over the years. The heritabilities of the fleece characteristics varied between 0.11 and 0.62. No genetic relationships were found between lamb weight at assessment and fleece characteristics. Breeding for heavier lambs can therefore be done without impairing the fleece quality. No unfavourable genetic correlations between the fleece traits were found. The results suggest that the reliability of the fleece inspection from a genetic point of view has not changed much over the last 20 years, although the fleece characteristics have been improved considerably during this period.

A numerical study of wind stress curl effects on eddies and filaments off the northwest coast of the Iberian Peninsula

A high-resolution, multi-level, primitive equation ocean model is used to examine the response to the particular conditions of anticyclonic (negative) wind stress curl and equatorward (upwelling favorable) winds along the eastern ocean boundary off the northwest coast of the Iberian Peninsula in the vicinity of the highly productive rias. A band of steady equatorward winds, which are uniform alongshore but contain zonal variability (i.e., anticyclonic wind stress curl), results in an equatorward coastal surface current nearshore and a poleward surface current offshore. In time, the currents become unstable and lead to the development of anticyclonic warm core eddies. In addition, cold core filament formation occurs in areas where the anticyclones advect the upwelled coastal water offshore. The results from the experiments support the hypothesis that wind forcing, particularly the combination of anticyclonic (negative) wind stress curl and equatorward (upwelling favorable) winds, is an important mechanism for generating opposing alongshore surface currents, anticyclonic eddies, and filaments off the northwest coast of the Iberian Peninsula. In a sensitivity study, the results from three numerical experiments are examined to understand, in a limited way, the dependence of the generation of the surface currents on the boundary conditions (free slip and no slip), the use of wind band forcing and the imposed wind stress curl distribution. Results show that, regardless of whether free-slip or no-slip boundary conditions or wind band forcing are used, opposing alongshore surface currents are generated. Because such currents do not develop when there is no wind stress curl, the opposing currents are generated by the anticyclonic wind stress curl.