Wind interaction with buoyant plumes on the inner continental shelf

The characteristics and effects of intrusions of estuarine outflow over the inner shelf were examined, based on hydrographic and meteorological observations obtained during the Coastal Ocean Processes (CoOP\u2794) field experiment located off the Outer Banks at Duck, North Carolina. The episodic presence of distinct low salinity water masses issuing from the Chesapeake Bay created an intermittent baroclinic coastal current along the North Carolina coast. Under low wind conditions, this current occupied the upper half of the water column within 9 km of the coast. The plume was bounded by a distinct southward-propagating front, a region offshore of high horizontal salinity and velocity gradients, and a strong pycnocline underneath. The intrusion traveled along the coast at a speed comparable to the linear internal wave speed of a two-layer system. Intrusions were generally associated with southward winds (downwelling conditions); however, several observed events opposed northward wind-driven flow. The geometry and dynamics of the low salinity plume were strongly controlled by the local winds. Northward (upwelling) winds caused the plumes to widen offshore and thin vertically. Southward (downwelling) winds acted initially to speed the intrusions\u27 alongcoast movement and cause them to narrow and deepen. Under strong downwelling winds, however, the intrusions contacted the bottom. This greatly decreased their speeds and caused diffusive widening. Propagation speeds of all plumes were seen to slow steadily through the study region. This was attributed to the observed mixing with ambient water along the path of the intrusion which increased its salinity, thereby reducing the buoyancy forcing. Under the continued influence of upwelling winds, the low salinity intrusions moved rapidly away from the coast and formed shallow lenses floating over the ambient shelf water. These generally dissipated in 1 to 2 days. The theoretical offshore transport response to wind forcing was investigated, illustrating two dynamical behaviors of the plumes, depending on whether they occupied the entire water column or were vertically segregated by stratification. The meteorological control of Bay/shelf exchange was examined to better comprehend the pulsed timing of the low salinity intrusions, which occurred every 2 to 8 days. Estimates of volume flux were derived from temporal variations of waterlevel measurements within the Chesapeake Bay. The volume flux time series exhibited strong peaks of outflow, which preceded the low salinity events off Duck, N.C. by an average of 1.1 days, a time lag consistent with the observed alongcoast propagation speeds

Temporal and Spatial Variations in Chesapeake Bay Water Quality: A Video Data Report

Over the past two years we have been developing computer programs to investigate various scientific visualization techniques as applied to estuarine data. The original impetus was to be able to visualize the results of the three-dimensional hydrodynamic model under development at the Virginia Institute of Marine Science, College of William and Mary (VIMS). We quickly recognized the superior ability of certain graphic approaches, especially pseudocolor animation, to efficiently transmit a tremendous amount of information to the viewer, allowing the scientist to gain an insight into the dynamics of the data not otherwise available. We decided to apply this technique to the U.S. Environmental Protection Agency (EPA) Bay Monitoring data set, a field collection effort so large that it sometimes overwhelms our traditional information presentations. What we present here is an alternative way of presenting and archiving large amounts of field measurements. The Chesapeake Bay Program began its water quality monitoring in the summer of 1984. Data collection in the mainstem of the Bay was done by University of Maryland (UMD), VIMS, and Old Dominion University (ODU), supported by EPA, while state regulatory agencies have been responsible for water quality data from the Maryland and Virginia tributaries. More than 130 stations ( 49 in the Bay proper) were occupied over 120 times each during the water years 1985 through 1990 (Figure 1). This information has been brought together to create color contoured images of the 10 different physical and water quality parameters that were measured. Each parameter for each month is summarized in a color image that shows the map-view surface and bottom distributions plus a vertical North-South section running down the natural channel from the Susquehanna to the mouth of the Bay, Each pixel in the map-view represents a lkm X lkm area. Although a certain amount of data manipulation must occur between the original logged measurements and these images, the distributions shown should best be understood as raw snapshots of what was present in the Chesapeake during that month. No data analysis or interpretation is attempted in this report

Simple Parameterized Models for Predicting Mobility, Burial and re-exposure of underwater munitions. SERDP Final Report MR-2224

A compilation of 761 observations of scour-induced burial and 406 observations of initiation of motion of UXO-like objects are presented. The main factors that increase the scour-induced burial-to-diameter ratio (B/D) under (i) currents and (ii) waves are the (i) Shields parameter (S) and (ii) Keulegan-Carpenter number. For cylinders under waves, B/D additionally increases as the current component parallel to wave orbitals decreases, as S increases, and as the angle between wave orbitals and a cylinder’s axis increases. Cylinders bury most, then spheres, and conical frustums bury least. Simple models dependent on these variables explain 85% of observed variance in B/D. Onset of motion is parameterized by fi S_Ucrit, where S_Ucrit is the critical object mobility parameter, and fi accounts for inertia forces from time-varying pressure gradients. S_Ucrit is observed to decrease systematically as D/k increases, where k is the bed roughness. Theory combined with observations lead to fi S_Ucrit = a1(D/k)^b1. Observations give a1 = 1.75 and b1 = - 0.72, which explains 89% of the observed variance in fi S_Ucrit

Hidden costs: The ethics of cost-effectiveness analyses for health interventions in resource-limited settings

Cost-effectiveness analysis (CEA) is an increasingly appealing tool for evaluating and comparing health-related interventions in resource-limited settings. The goal is to inform decision-makers regarding the health benefits and associated costs of alternative interventions, helping guide allocation of limited resources by prioritizing interventions that offer the most health for the least money. Although only one component of a more complex decision-making process, CEAs influence the distribution of healthcare resources, directly influencing morbidity and mortality for the world’s most vulnerable populations. However, CEA-associated measures are frequently setting-specific valuations, and CEA outcomes may violate ethical principles of equity and distributive justice. We examine the assumptions and analytical tools used in CEAs that may conflict with societal values. We then evaluate contextual features unique to resource-limited settings, including the source of health-state utilities and disability weights; implications of CEA thresholds in light of economic uncertainty; and the role of external donors. Finally, we explore opportunities to help align interpretation of CEA outcomes with values and budgetary constraints in resource-limited settings. The ethical implications of CEAs in resource-limited settings are vast. It is imperative that CEA outcome summary measures and implementation thresholds adequately reflect societal values and ethical priorities in resource-limited settings

COMAP Early Science: VI. A First Look at the COMAP Galactic Plane Survey

We present early results from the COMAP Galactic Plane Survey conducted between June 2019 and April 2021, spanning $20^\circ<\ell<40^\circ$ in Galactic longitude and |b|<1.\!\!^{\circ}5 in Galactic latitude with an angular resolution of $4.5^{\prime}$. The full survey will span $\ell \sim 20^{\circ}$- $220^{\circ}$ and will be the first large-scale radio continuum survey at $30$ GHz with sub-degree resolution. We present initial results from the first part of the survey, including diffuse emission and spectral energy distributions (SEDs) of HII regions and supernova remnants. Using low and high frequency surveys to constrain free-free and thermal dust emission contributions, we find evidence of excess flux density at $30\,$GHz in six regions that we interpret as anomalous microwave emission. Furthermore we model UCHII contributions using data from the $5\,$GHz CORNISH catalogue and reject this as the cause of the $30\,$GHz excess. Six known supernova remnants (SNR) are detected at $30\,$GHz, and we measure spectral indices consistent with the literature or show evidence of steepening. The flux density of the SNR W44 at $30\,$GHz is consistent with a power-law extrapolation from lower frequencies with no indication of spectral steepening in contrast with recent results from the Sardinia Radio Telescope. We also extract five hydrogen radio recombination lines to map the warm ionized gas, which can be used to estimate electron temperatures or to constrain continuum free-free emission. The full COMAP Galactic plane survey, to be released in 2023/2024, will be an invaluable resource for Galactic astrophysics.Comment: Paper 6 of 7 in series. 28 pages, 10 figures, submitted to Ap

COMAP Early Science: IV. Power Spectrum Methodology and Results

We present the power spectrum methodology used for the first-season COMAP analysis, and assess the quality of the current data set. The main results are derived through the Feed-feed Pseudo-Cross-Spectrum (FPXS) method, which is a robust estimator with respect to both noise modeling errors and experimental systematics. We use effective transfer functions to take into account the effects of instrumental beam smoothing and various filter operations applied during the low-level data processing. The power spectra estimated in this way have allowed us to identify a systematic error associated with one of our two scanning strategies, believed to be due to residual ground or atmospheric contamination. We omit these data from our analysis and no longer use this scanning technique for observations. We present the power spectra from our first season of observing and demonstrate that the uncertainties are integrating as expected for uncorrelated noise, with any residual systematics suppressed to a level below the noise. Using the FPXS method, and combining data on scales $k=0.051-0.62 \,\mathrm{Mpc}^{-1}$ we estimate $P_\mathrm{CO}(k) = -2.7 \pm 1.7 \times 10^4\mu\textrm{K}^2\mathrm{Mpc}^3$, the first direct 3D constraint on the clustering component of the CO(1-0) power spectrum in the literature.Comment: Paper 4 of 7 in series. 18 pages, 11 figures, as accepted in Ap

COMAP Early Science: III. CO Data Processing

We describe the first season COMAP analysis pipeline that converts raw detector readouts to calibrated sky maps. This pipeline implements four main steps: gain calibration, filtering, data selection, and map-making. Absolute gain calibration relies on a combination of instrumental and astrophysical sources, while relative gain calibration exploits real-time total-power variations. High efficiency filtering is achieved through spectroscopic common-mode rejection within and across receivers, resulting in nearly uncorrelated white noise within single-frequency channels. Consequently, near-optimal but biased maps are produced by binning the filtered time stream into pixelized maps; the corresponding signal bias transfer function is estimated through simulations. Data selection is performed automatically through a series of goodness-of-fit statistics, including $\chi^2$ and multi-scale correlation tests. Applying this pipeline to the first-season COMAP data, we produce a dataset with very low levels of correlated noise. We find that one of our two scanning strategies (the Lissajous type) is sensitive to residual instrumental systematics. As a result, we no longer use this type of scan and exclude data taken this way from our Season 1 power spectrum estimates. We perform a careful analysis of our data processing and observing efficiencies and take account of planned improvements to estimate our future performance. Power spectrum results derived from the first-season COMAP maps are presented and discussed in companion papers.Comment: Paper 3 of 7 in series. 26 pages, 23 figures, submitted to Ap

COMAP Early Science: V. Constraints and Forecasts at z∼3z \sim 3

We present the current state of models for the $z\sim3$ carbon monoxide (CO) line-intensity signal targeted by the CO Mapping Array Project (COMAP) Pathfinder in the context of its early science results. Our fiducial model, relating dark matter halo properties to CO luminosities, informs parameter priors with empirical models of the galaxy-halo connection and previous CO(1-0) observations. The Pathfinder early science data spanning wavenumbers $k=0.051$-$0.62\,$Mpc$^{-1}$ represent the first direct 3D constraint on the clustering component of the CO(1-0) power spectrum. Our 95% upper limit on the redshift-space clustering amplitude $A_{\rm clust}\lesssim70\,\mu$K$^2$ greatly improves on the indirect upper limit of $420\,\mu$K$^2$ reported from the CO Power Spectrum Survey (COPSS) measurement at $k\sim1\,$Mpc$^{-1}$. The COMAP limit excludes a subset of models from previous literature, and constrains interpretation of the COPSS results, demonstrating the complementary nature of COMAP and interferometric CO surveys. Using line bias expectations from our priors, we also constrain the squared mean line intensity-bias product, $\langle{Tb}\rangle^2\lesssim50\,\mu$K$^2$, and the cosmic molecular gas density, $\rho_\text{H2}<2.5\times10^8\,M_\odot\,$Mpc$^{-3}$ (95% upper limits). Based on early instrument performance and our current CO signal estimates, we forecast that the five-year Pathfinder campaign will detect the CO power spectrum with overall signal-to-noise of 9-17. Between then and now, we also expect to detect the CO-galaxy cross-spectrum using overlapping galaxy survey data, enabling enhanced inferences of cosmic star-formation and galaxy-evolution history.Comment: Paper 5 of 7 in series. 17 pages + appendix and bibliography (30 pages total); 15 figures, 6 tables; accepted for publication in ApJ; v3 reflects the accepted version with minor changes and additions to tex

COMAP Early Science: II. Pathfinder Instrument

Line intensity mapping (LIM) is a new technique for tracing the global properties of galaxies over cosmic time. Detection of the very faint signals from redshifted carbon monoxide (CO), a tracer of star formation, pushes the limits of what is feasible with a total-power instrument. The CO Mapping Project (COMAP) Pathfinder is a first-generation instrument aiming to prove the concept and develop the technology for future experiments, as well as delivering early science products. With 19 receiver channels in a hexagonal focal plane arrangement on a 10.4 m antenna, and an instantaneous 26-34 GHz frequency range with 2 MHz resolution, it is ideally suited to measuring CO($J$=1-0) from $z\sim3$. In this paper we discuss strategies for designing and building the Pathfinder and the challenges that were encountered. The design of the instrument prioritized LIM requirements over those of ancillary science. After a couple of years of operation, the instrument is well understood, and the first year of data is already yielding useful science results. Experience with this Pathfinder will drive the design of the next generations of experiments.Comment: Paper 2 of 7 in series. 27 pages, 28 figures, submitted to Ap

COMAP Early Science: VII. Prospects for CO Intensity Mapping at Reionization

We introduce COMAP-EoR, the next generation of the Carbon Monoxide Mapping Array Project aimed at extending CO intensity mapping to the Epoch of Reionization. COMAP-EoR supplements the existing 30 GHz COMAP Pathfinder with two additional 30 GHz instruments and a new 16 GHz receiver. This combination of frequencies will be able to simultaneously map CO(1--0) and CO(2--1) at reionization redshifts ($z\sim5-8$) in addition to providing a significant boost to the $z\sim3$ sensitivity of the Pathfinder. We examine a set of existing models of the EoR CO signal, and find power spectra spanning several orders of magnitude, highlighting our extreme ignorance about this period of cosmic history and the value of the COMAP-EoR measurement. We carry out the most detailed forecast to date of an intensity mapping cross-correlation, and find that five out of the six models we consider yield signal to noise ratios (S/N) $\gtrsim20$ for COMAP-EoR, with the brightest reaching a S/N above 400. We show that, for these models, COMAP-EoR can make a detailed measurement of the cosmic molecular gas history from $z\sim2-8$, as well as probe the population of faint, star-forming galaxies predicted by these models to be undetectable by traditional surveys. We show that, for the single model that does not predict numerous faint emitters, a COMAP-EoR-type measurement is required to rule out their existence. We briefly explore prospects for a third-generation Expanded Reionization Array (COMAP-ERA) capable of detecting the faintest models and characterizing the brightest signals in extreme detail.Comment: Paper 7 of 7 in series. 19 pages, 10 figures, to be submitted to Ap