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

Variability of near-surface circulation and sea surface salinity observed from Lagrangian drifters in the northern Bay of Bengal during the Waning 2015 Southwest Monsoon

Author Posting. © The Oceanography Society, 2016. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 29, no. 2 (2016): 124–133, doi:10.5670/oceanog.2016.45.A dedicated drifter experiment was conducted in the northern Bay of Bengal during the 2015 waning southwest monsoon. To sample a variety of spatiotemporal scales, a total of 36 salinity drifters and 10 standard drifters were deployed in a tight array across a freshwater front. The salinity drifters carried for the first time a revised sensor algorithm, and its performance during the 2015 field experiment is very encouraging for future efforts. Most of the drifters were quickly entrained in a mesoscale feature centered at about 16.5°N, 89°E and stayed close together during the first month of observations. While the eddy was associated with rather homogeneous temperature and salinity characteristics, much larger variability was found outside of it toward the coastline, and some of the observed salinity patches had amplitudes in excess of 1.5 psu. To particularly quantify the smaller spatiotemporal scales, an autocorrelation analysis of the drifter salinities for the first two deployment days was performed, indicating not only spatial scales of less than 5 km but also temporal variations of the order of a few hours. The hydrographic measurements were complemented by first estimates of kinematic properties from the drifter clusters, however, more work is needed to link the different observed characteristics.VH and LR were supported by ONR grant N00014- 13-1-0477 and NOAA GDP grant NA10OAR4320156. AM and SE were funded by ONR grant N00014‑13-1- 0451, and ED by ONR grant N00014-14-1-0235. BPK acknowledges financial support from the Ministry of Earth Sciences (MoES, Government of India)

Simulation of High Conversion Efficiency and Open-circuit Voltages Of {\alpha}-si/poly-silicon Solar Cell

The P+ {\alpha}-Si /N+ polycrystalline solar cell is molded using the AMPS-1D device simulator to explore the new high efficiency thin film poly-silicon solar cell. In order to analyze the characteristics of this device and the thickness of N+ poly-silicon, we consider the impurity concentration in the N+ poly-silicon layer and the work function of transparent conductive oxide (TCO) in front contact in the calculation. The thickness of N+ poly-silicon has little impact on the device when the thickness varies from 20 {\mu}m to 300 {\mu}m. The effects of impurity concentration in polycrystalline are analyzed. The conclusion is drawn that the open-circuit voltage (Voc) of P+ {\alpha}-Si /N+ polycrystalline solar cell is very high, reaching 752 mV, and the conversion efficiency reaches 9.44%. Therefore, based on the above optimum parameters the study on the device formed by P+ {\alpha}-Si/N+ poly-silicon is significant in exploring the high efficiency poly-silicon solar cell.Comment: 8 pages 6figures, 1 table

A dataset of hourly sea surface temperature from drifting buoys

A dataset of sea surface temperature (SST) estimates is generated from the temperature observations of surface drifting buoys of NOAA’s Global Drifter Program. Estimates of SST at regular hourly time steps along drifter trajectories are obtained by fitting to observations a mathematical model representing simultaneously SST diurnal variability with three harmonics of the daily frequency, and SST low-frequency variability with a first degree polynomial. Subsequent estimates of non-diurnal SST, diurnal SST anomalies, and total SST as their sum, are provided with their respective standard uncertainties. This Lagrangian SST dataset has been developed to match the existing and on-going hourly dataset of position and velocity from the Global Drifter Program

Fabrication of improved SiGe alloys for an 18-couple module test

N- and p-type Si{sub 0.78}Ge{sub 0.22} alloys were fabricated to determine if recently reported improvements in the figure-of-merit, Z, could be realized in devices. These will be tested in an 18-couple module to directly compare the performance of these materials with that of standard coarse-grain SiGe used in flight programs. We describe the synthesis by vacuum casting and hot pressing p-type SiGe and mechanical alloying and hot-isostatic pressing n-type SiGe. Improved materials and standard materials are characterized and compared. The integrated average figures-of-merit (573--1273 K) of the improved materials were Z{sub p} = 0.59 {times} 10{sup {minus}3} K{sup {minus}1} and Z{sub n} = 0.85 {times} 10{sup {minus}3} K{sup {minus}1} compared with Z{sub p} = 0.52 {times} l0{sup {minus}3} K{sup {minus}1} and Z{sub n} = 0.76 {times} 10{sup {minus}3} K{sup {minus}1} for the standard materials. We also report the power factors for improved and standard materials removed from fabricated devices to gain insight as to how subsequent processing impacts performance

From salty to fresh—salinity processes in the Upper-ocean Regional Study-2 (SPURS-2) : diagnosing the physics of a rainfall-dominated salinity minimum

Author Posting. © The Oceanography Society, 2015. This article is posted here by permission of The Oceanography Society for personal use, not for redistribution. The definitive version was published in Oceanography 28, no. 1 (2015): 150-159, doi:10.5670/oceanog.2015.15.One of the notable features of the global ocean is that the salinity of the North Atlantic is about 1 psu higher than that of the North Pacific. This contrast is thought to be due to one of the large asymmetries in the global water cycle: the transport of water vapor by the trade winds across Central America and the lack of any comparable transport into the Atlantic from the Sahara Desert. Net evaporation serves to maintain high Atlantic salinities, and net precipitation lowers those in the Pacific. Because the effects on upper-ocean physics are markedly different in the evaporating and precipitating regimes, the next phase of research in the Salinity Processes in the Upper-ocean Regional Study (SPURS) must address a high rainfall region. It seemed especially appropriate to focus on the eastern tropical Pacific that is freshened by the water vapor carried from the Atlantic. In a sense, the SPURS-2 Pacific region will be looking at the downstream fate of the freshwater carried out of the SPURS-1 North Atlantic region. Rainfall tends to lower surface density and thus inhibit vertical mixing, leading to quite different physical structure and dynamics in the upper ocean. Here, we discuss the motivations for the location of SPURS-2 and the scientific questions we hope to address

Mixing to monsoons: Air-sea interactions in the bay of Bengal

More than 1 billion people depend on rainfall from the South Asian monsoon for their livelihoods. Summertime monsoonal precipitation is highly variable on intraseasonal time scales, with alternating "active" and "break" periods. These intraseasonal oscillations in large-scale atmospheric convection and winds are closely tied to 1°C-2°C variations of sea surface temperature in the Bay of Bengal

Diagnosing Frontal Dynamics From Observations Using a Variational Approach

Intensive hydrographic and horizontal velocity measurements collected in the Alboran Sea enabled us to diagnose the three-dimensional dynamics of a frontal system. The sampled domain was characterized by a 40 km diameter anticyclonic eddy, with an intense front on its eastern side, separating the Atlantic and Mediterranean waters. Here, we implemented a multi-variate variational analysis (VA) to reconstruct the hydrographic fields, combining the 1-km horizontal resolution of the Underway Conductivity-Temperature-Depth (CTD) system with information on the flow shape from the Acoustic Doppler Current Profiler velocities. One advantage of the VA is given by the physical constraint, which preserves fine-scale gradients better than the classical optimal interpolation (OI). A comparison between real drifter trajectories and virtual particles advected in the mapping quantified the improvements in the VA over the OI, with a 15% larger skill score. Quasi-geostrophic (QG) and semi-geostrophic (SG) omega equations enabled us to estimate the vertical velocity (w) which reached 40 m/day on the dense side of the front. How nutrients and other passive tracers leave the mixed-layer and subduct is estimated with 3D advection from the VA, which agreed with biological sampling from traditional CTD casts at two eddy locations. Downwelling warm filaments are further evidence of subduction, in line with the w from SG, but not with QG. SG better accounted for the along-isopycnal component of w in agreement with another analysis made on isopycnal coordinates. The multi-platform approach of this work and the use of variational methods improved the characterization and understanding of (sub)-mesoscale frontal dynamics.This research was supported by the Office of Naval Research Departmental Research Initiative CALYPSO under program officers Terri Paluszkiewicz and Scott Harper. The authors' ONR Grant are as follows: N000141613130 (AP, SR and AM), N000141812418 (PMP), S. Johnston N000141812416 (TMSJ), N000141812138 (TO), N000141712517 and N00014191269 (LRC), N000141812139 and N000141812420 (AS) and N000141812139and (EDA). This article is also a contribution to the PRE-SWOT project funded by the Spanish Research Agency and the European Regional Development Fund (AEI/FEDER, UE) under grant agreement (CTM2016-78607-P)