Shelf MIxed Layer Experiment (SMILE) program description and coastal and moored array data report

The Shelf MIxed Layer Experiment (SMILE) was designed to study the response of the oceanic surface boundary layer over the continental shelf to atmospheric forcing. The SMILE field program was conducted over the northern California shelf between Pt. Arena and Pt. Reyes from mid-November 1988 to mid-May 1989. The field program consisted of five main components: (a) a long-term moored array to obtain current, temperature, and conductivity time series observations in the upper ocean over the shelf; (b) a short-term moored instrument deployment to measure the vertical current shear and stratification in the top 6 m of the water column; (c) shipboard CTD and acoustic Doppler current profiler (ADCP) surveys over the shelf and adjacent slope to map regional water property and current distributions; (d) a long-term moored and coastal meteorological array including one sounding station to obtain time series observations of the atmospheric surface forcing and monitor the structure of the marine boundary layer; and (e) overflights with an instrumented aircraft to measure the spatial structure of the surface wind, wind stress, and heat flux fields under different atmospheric conditions. This report has two objectives: (a) to describe the SMILE field program, including overviews of the five components, and (b) to present a statistical and graphical summary of the atmospheric (wind, air temperature, pressure, relative humidity, short- and longwave radiation) and oceanic (current, water temperature, and conductivity) long-term array measurements made as part of SMILE. A more detailed description of the instrumentation used in SMILE and an assessment of instrument performance and accuracy are presented separately by Dean et al. (1991).Funding was provided by the National Science Foundation through Grant No. OCE-87-16937

A multidisciplinary Amazon Shelf SEDiment Study (AmasSeds) : physical oceanography moored array component

A Multidisciplinary Amazon Shelf SEDiment Study (AmasSeds) is a cooperative research program by geological, chemical, physical, and biological oceanographers from Brazil and the United States to study sedimentary processes occurring over the continental shelf near the mouth of the Amazon River. The physical oceanography component of AmasSeds included a moored array deployed on the continental shelf approximately 300km northwest of the Amazon River mouth near 3.5°N. The moored array consisted of a cross-shelf transect of three mooring sites located on the 18-m, 65-m, and 103-m isobaths. The moored array was deployed for approximately 4 months, from early February, 1990 to mid-June, 1990, obtaining time series measurements of current, temperature, conductivity, and wind. This report describes the physical oceanography moored array component and provides a statistical and graphical summary of the moored observations.Funding was provided by the National Science Foundation through Grant Nos. OCE 88-12917 and OCE 91-15712

The 1995 Georges Bank Stratification Study and moored array measurements

The 1995 Geoges Bank Stratification Study (GBSS) was the first intensive process study conducted as part of the U.S. GLOBEC Northwest Atlantic/Georges Bank field program. The GBSS was designed to investigate the physical processes which control the seasonal development of stratification along the southern flank of Georges Bank during spring and summer. Past work suggested that during this period, larval cod and haddock tended to aggregate to the thermocline on the southern flank where higher concentrations of their copepod prey were found. A moored array was deployed as part of GBSS to observe the onset and evolution of sesonal stratification over the southern flank with sufficient vertical and horizontal resolution that key physical processes could be identified and quantified. Moored current, temperature, and conductivity (salinity) measurements were made at three sites along the southern flank, one on the crest, and one on the northeast peak of the bank. Moored surface meteorological measurements were also made at one southern flank site to determine the surface wind stress and heat and moisture fluxes. The oceanographic and meteorological data collected with the GBSS array during January-August 1995 are presented in this report. Meteorological data collected on National Data Buoy Center environmental buoys 44011 (Georges Bank), 44008 (Nantucket Shoals), and 44005 (Gulf of Maine) are included in this report for completeness and comparison with the GBSS southern flank meteorological measurements.Funding was provided by the National Science Foundation under Grant Numbers OCE-98-06379 and OCE-98-06445

Surface heat flux variability over the northern California shelf

Surface heat flux components are estimated at a midshelf site over the northern California shelf using moored measurements from the 1981-1982 Coastal Ocean Dynamics Experiment (CODE) and the 1988-1989 Shelf Mixed Layer Experiment (SMILE). Time series of estimated fluxes extend from early winter through summer upwelling conditions, allowing examination of seasonal variations as well as synoptic events. On a seasonal timescale, the surface heat flux is strongly influenced net surface heat flux are the annual variation in incident shortwave solar radiation (insolation) and the atmospheric spring transition. Between mid-November 1988 and late February 1989, insolation is weak and the Mean daily averaged heat flux is nearly zero (absolute value less than 10W m¯²), with a standard deviation of ~50 W m¯². Beginning in March, insolation increases markedly, and typical daily-average heat fluxes increase to greater than 100W m¯² by the spring transition in April or May. In June and July, the average heat flux is near 200 W m¯², with a standard deviation of ~90 W m¯². In winter, the daily-averaged heat flux varies on periods of several days. Net heat flux losses can range up to 130W m¯². These losses are not identified with any one type of event. For example, comparable heat flux losses can occur for very low relative humidities (RHs), moderate winds, and clear skies, and for high RHs, high winds, and cloudy skies. In summer, surface heat flux variability is strongly influenced by upwelling and relaxation events. Upwelling is characterized by clear skies and high equatorward winds, while relaxation is characterized by the presence of clouds and low or northward winds. These conditions lead to opposing changes in insolation and in longwave radiative cooling and latent heat flux. Variability in insolation dominates, and the daily-averaged heat flux into the ocean is greatest during upwellineg vents (up to 350W m¯² or more) and least during relaxation events (sometimes less than 100W m¯²)

Global Comparison of Core-Collapse Supernova Simulations in Spherical Symmetry

We present a comparison between several simulation codes designed to study the core-collapse supernova mechanism. We pay close attention to controlling the initial conditions and input physics in order to ensure a meaningful and informative comparison. Our goal is three-fold. First, we aim to demonstrate the current level of agreement between various groups studying the core-collapse supernova central engine. Second, we desire to form a strong basis for future simulation codes and methods to compare to. Lastly, we want this work to be a stepping stone for future work exploring more complex simulations of core-collapse supernovae, i.e., simulations in multiple dimensions and simulations with modern neutrino and nuclear physics. We compare the early (first ~500ms after core bounce) spherically-symmetric evolution of a 20 solar mass progenitor star from six different core-collapse supernovae codes: 3DnSNe-IDSA, AGILE-BOLTZTRAN, FLASH, F{\sc{ornax}}, GR1D, and PROMETHEUS-VERTEX. Given the diversity of neutrino transport and hydrodynamic methods employed, we find excellent agreement in many critical quantities, including the shock radius evolution and the amount of neutrino heating. Our results provide an excellent starting point from which to extend this comparison to higher dimensions and compare the development of hydrodynamic instabilities that are crucial to the supernova explosion mechanism, such as turbulence and convection.Comment: 24 pages, 7 figures, J. Phys. G focus issue on core-collapse supernovae. This document was written collaboratively on Authorea, comments welcome at https://www.authorea.com/users/1943/articles/167397-global-comparison-of-core-collapse-supernova-simulations-in-spherical-symmetr

CODE-2 : moored array and large-scale data report

The Coastal Ocean Dynamics Experiment (CODE) was undertaken to identify and study the important dynamical processes which govern the wind-driven motion of coastal water over the continental shelf. The initial effort in this multi-year, multi-institutional research program was to obtain high-quality data sets of all the relevant physical variables needed to construct accurate kinematic and dynamic descriptions of the response of shelf water to strong wind forcing in the 2 to 10 day band. A series of two small-scale, densely- instrumented field experiments of approximately four months duration (called CODE-1 and CODE-2) were designed to explore and to determine the kinematics and momentum and heat balances of the local wind-driven flow over a region of the northern California shelf which is characterized by both relatively simple bottom topography and large wind stress events in both winter and summer. A more lightly instrumented, long -term, large-scale component was designed to help separate the local wind-driven response in the region of the small-scale experiments from motions generated either offshore by the California Current system or in some distant region along the coast, and also to help determine the seasonal cycles of the atmospheric forcing, water structure, and coastal currents over the northern California shelf. The first small-scale experiment (CODE-1) was conducted between April and August, 1981 as a pilot study in "which primary emphasis was placed on characterizing the wind-driven "signal" and the "noise" from which this signal must be extracted. In particular, CODE-1 was designed to identify the key features of the circulation and its variability over the northern California shelf and to determine the important time and length scales of the wind-driven response. The second small-scale experiment (CODE-2) was conducted between April and August, 1982 and was designed to sample more carefully the mesoscale horizonta1 variability observed in CODE-1. This report presents a basic description of the moored array data and some other Eulerian data collected during CODE-2. A brief description of the CODE-2 field program is presented first, followed by a description of the common data analysis procedures used to produce the various data sets presented here. Then basic descriptions of the following data sets are presented: (a) the coastal and moored meteorological measurements, (b) the moored current measurements, (c) array plots of the surface wind stress and near-surface current measurements, (d) the moored temperature and conductivity observations, (e) the bottom pressure measurements, and (f) the wind and adjusted coastal sea level observations obtained as part of the CODE-2 large-scale component.This work has been supported by the National Science Foundation

Delta Narratives: Saving the Historical and Cultural Heritage of The Sacramento-San Joaquin Delta

From August 2014 through July 2015, the Delta Narratives project, on contract to the Delta Protection Commission, addressed two questions. First, in what ways does the historical experience of the Sacramento-San Joaquin Delta contribute to an understanding of key themes in regional and American history? Second, how might Delta stories gain wider appreciation within the region, throughout Northern California, and among people in the rest of California and beyond? Scholars on the project team documented ways the history of the Delta illustrates trends in land management and reclamation, technological shifts in transportation and agriculture, the impact of ethnicity and labor specialization on community building, and finally, the shifting visioning of America\u27s promise and fall from grace by artists and writers in response to the intense cultivation of the Delta and the conditions which workers there endured. Their essays testify to the intrinsic value of Delta stories and to the additional perspectives they bring to regional and national history. With these essays in hand, the project team investigated the current infrastructure for the preservation and dissemination of historical and cultural information in the Delta. It created a directory of institutions committed to promoting Delta stories. In order to stimulate conversations between these stakeholders, the team organized two workshops at which the scholars and archivists shared insights and invited commentary and conversation. Subsequently, with the support of the Center for California Studies at Sacramento State University, a conference entitled “More than H2O: Saving the History and Culture of the Sacramento-San Joaquin Delta” presented findings and discussed strategies with an audience of state and local stakeholders. Delta Narratives culminated with a conference organized around an American Assembly model. The conference generated a list of suggestions for further action regarding the recognition, preservation, and dissemination of Delta stories. High on the list of initiatives were adequate mapping of historically significant locations, an organization that would draw together the many cultural and historical groups in the Delta toward common action, the initiation of annual Delta Days to celebrate the region, and the creation of educational materials including web applications (apps), and a website devoted to the region

A Study of Carbon Features in Type Ia Supernova Spectra

One of the major differences between various explosion scenarios of Type Ia supernovae (SNe Ia) is the remaining amount of unburned (C+O) material and its velocity distribution within the expanding ejecta. While oxygen absorption features are not uncommon in the spectra of SNe Ia before maximum light, the presence of strong carbon absorption has been reported only in a minority of objects, typically during the pre-maximum phase. The reported low frequency of carbon detections may be due to low signal-to-noise data, low abundance of unburned material, line blending between C II 6580 and Si II 6355, ejecta temperature differences, asymmetrical distribution effects, or a combination of these. However, a survey of published pre-maximum spectra reveals that more SNe Ia than previously thought may exhibit C II 6580 absorption features and relics of line blending near 6300 Angstroms. Here we present new SN Ia observations where spectroscopic signatures of C II 6580 are detected, and investigate the presence of C II 6580 in the optical spectra of 19 SNe Ia using the parameterized spectrum synthesis code, SYNOW. Most of the objects in our sample that exhibit C II 6580 absorption features are of the low-velocity gradient subtype. Our study indicates that the morphology of carbon-rich regions is consistent with either a spherical distribution or a hemispheric asymmetry, supporting the recent idea that SN Ia diversity may be a result of off-center ignition coupled with observer line-of-sight effects.Comment: 10 papges, 9 figures, 3 table

Near-Ultraviolet Properties of a Large Sample of Type Ia Supernovae as Observed with the Swift UVOT

We present ultraviolet (UV) and optical photometry of 26 Type Ia supernovae (SNe~Ia) observed from March 2005 to March 2008 with the NASA {\it Swift} Ultraviolet and Optical Telescope (UVOT). The dataset consists of 2133 individual observations, making it by far the most complete study of the UV emission from SNe~Ia to date. Grouping the SNe into three subclasses as derived from optical observations, we investigate the evolution of the colors of these SNe, finding a high degree of homogeneity within the normal subclass, but dramatic differences between that group and the subluminous and SN 2002cx-like groups. For the normal events, the redder UV filters on UVOT ($u$, $uvw1$) show more homogeneity than do the bluer UV filters ($uvm2$, $uvw2$). Searching for purely UV characteristics to determine existing optically based groupings, we find the peak width to be a poor discriminant, but we do see a variation in the time delay between peak emission and the late, flat phase of the light curves. The UV light curves peak a few days before the $B$ band for most subclasses (as was previously reported by Jha et al. 2006a), although the SN 2002cx-like objects peak at a very early epoch in the UV. That group also features the bluest emission observed among SNe~Ia. As the observational campaign is ongoing, we discuss the critical times to observe, as determined by this study, in order to maximize the scientific output of future observations.Comment: Accepted to Astrophysical Journa