Comparison of Continuous Records of Near-Bottom Dissolved Oxygen from the Hypoxia Zone along the Louisiana Coast

Oxygen depletion is a seasonally dominant feature of the lower water column on the highly-stratified, riverine-influenced continental shelf of Louisiana. The areal extent of hypoxia (bottom waters ≤2 mg l−1 dissolved oxygen) in mid-summer may encompass up to 9,500 km2, from the Mississippi River delta to the upper Texas coast, with the spatial configuration of the zone varying interannually. We placed two continuously recording oxygen meters (Endeco 1184) within 1 m of the seabed in 20-m water depth at two locations 77 km apart where we previously documented midsummer bottom water hypoxia. The oxygen meters recorded considerably different oxygen conditions for a 4-mo deployment from mid-June through mid-October. At the station off Terrebonne Bay (C6A), bottom waters were severely depleted in dissolved oxygen and often anoxic for most of the record from mid-June through mid-August, and there were no strong diurnal or diel patterns. At the station 77 km to the east and closer to the Mississippi River delta (WD32E), hypoxia occurred for only 50% of the record, and there was a strong diurnal pattern in the oxygen time-series data. There was no statistically significant coherence between the oxygen time-series at the two stations. Coherence of the oxygen records with wind records was weak. The dominant coherence identified was between the diurnal peaks in the WD32E oxygen record and the bottom pressure record from a gauge located at the mouth of Terrebonne Bay, suggesting that the dissolved oxygen signal at WD32E was due principally to advection by tidal currents. Although the oxygen time-series were considerably different, they were consistent with the physical and biological processes that affect hypoxia on the Louisiana shelf. Differences in the time-series were most intimately tied to the topographic cross-shelf gradients in the two locations, that is, station C6A off Terrebonne Bay was in the middle of a broad, gradually sloping shelf and station WD32E in the Mississippi River Delta Bight was in an area with a steeper cross-shelf depth gradient and likely situated near the edge of a hypoxic water mass that was tidally advected across the study site

Compressibility effects on the longitudinal stability and control of a pursuit-type airplane as measured in flight

Measurements of the longitudinal stability and control of a pursuit-type airplane were made in flight up to a Mach number of 0.78. The data are presented in the form of curves showing the variation, with center-of-gravity position, dynamic pressure, and Mach number, of the stick-fixed and stick-free stability, control, and balance of the airplane

A technical framework to describe occupant behavior for building energy simulations

ABSTRACT Green buildings that fail to meet expected design performance criteria indicate that technology alone does not guarantee high performance. Human influences are quite often simplified and ignored in the design, construction, and operation of buildings. Energy-conscious human behavior has been demonstrated to be a significant positive factor for improving the indoor environment while reducing the energy use of buildings. In our study we developed a new technical framework to describe energyrelated human behavior in buildings. The energy-related behavior includes accounting for individuals and groups of occupants and their interactions with building energy services systems, appliances and facilities. The technical framework consists of four key components: i. the drivers behind energy-related occupant behavior, which are biological, societal, environmental, physical, and economical in nature ii. the needs of the occupants are based on satisfying criteria that are either physical (e.g. thermal, visual and acoustic comfort) or non-physical (e.g. entertainment, privacy, and social reward) iii. the actions that building occupants perform when their needs are not fulfilled iv. the systems with which an occupant can interact to satisfy their needs The technical framework aims to provide a standardized description of a complete set of human energyrelated behaviors in the form of an XML schema. For each type of behavior (e.g., occupants opening/closing windows, switching on/off lights etc.) we identify a set of common behaviors based on a literature review, survey data, and our own field study and analysis. Stochastic models are adopted or developed for each type of behavior to enable the evaluation of the impact of human behavior on energy use in buildings, during either the design or operation phase. We will also demonstrate the use of the technical framework in assessing the impact of occupancy behavior on energy saving technologies. The technical framework presented is part of our human behavior research, a 5-year program under the

Hydrographic, biological, and nutrient characteristics of the water column on the Louisiana shelf, July, 1987

Beginning in 1985, several research cruises were conducted by our research team to assess the spatial and temporal extent, intensity, and potential causes of oxygen depletion in the northern Gulf of Mexico. Hypoxic bottom waters were studied along two transects in and near the Mississippi River Delta Bight in 1985 and 1986. In addition, shelf-wide cruises were conducted from the Mississippi River to the Texas border during July of both years. The intent of these cruises was to provide comparative information on the temporal variability of oxygen-depleted bottom waters on the Louisiana shelf. The bi-weekly cruises along the southeastern Louisiana shelf were discontinued in 1987. A shelf-wide cruise, however, was conducted in July, 1987 to continue the studies of temporal variability on the Louisiana shelf. The cruise was conducted on the R/V Pelican from July 1 through July 5

Hydrographic, biological, and nutrient characteristics of the water column on the Louisiana shelf, July and September, 1985

In June 1985, a focused study was initiated to assess the spatial and temporal extent, intensity, and potential causes of oxygen depletion in the northern Gulf of Mexico. Two shelf-wide, quasi-synoptic cruises were conducted from the Mississippi River to the Texas border during mid-July and early September, 1985. Cruises were conducted aboard the R/V Pelican on 15-20 July and 10-13 September. Stations were occupied along ten transects in 5 to 80 m water depth. Stations for Pelican Cruise I extended farther offshore and farther to the west than those for Pelican Cruise II. In addition to these shelf-wide cruises, hypoxic bottom waters were studied more frequently along two transects in the Mississippi River Delta Bight area

Hydrographic, biological, and nutrient characteristics of the water column on the Louisiana shelf during 1988

Since 1985, several research cruises were conducted by our research team to assess the spatial and temporal extent, intensity, and potential causes of oxygen depletion in the northern Gulf of Mexico. Hypoxic bottom waters were studied along two transects in and near the Mississippi River Delta Bight in 1985 and 1986. In addition, shelf-wide cruises were conducted from the Mississippi River to the Texas border during July of 1985, 1986, and 1987. These cruises have provided us with exhaustive information concerning the temporal and spatial variability associated with the phenomenon of hypoxia on the Louisiana shelf. It was not our intent to continue assessment-type cruises during 1988. Opportunities existed, however, in conjunction with other research cruises and the LUMCON summer program to re-occupy stations along Transect C off Cat Island Pass near Cocodrie. In addition, the drought conditions in the upper Mississippi River basin during the spring and summer of 1988 resulted in a significant reduction in the flow rate of the Mississippi River. We were therefore compelled to conduct a shelf-wide cruise during mid-summer of 1988 to document the hydrographic conditions of the Louisiana shelf under low flow conditions of the Mississippi River and to assess the effects of this low flow on the phenomenon of hypoxia. The cruises along Transect C were conducted on board the R/V Pelican as part of a research effort named LaSER for data in April and as part of the LUMCON summer program for the remainder. The shelf-wide cruise was conducted on board the R/V Acadiana from August 12 through August 16, 1988

Hydrographic, biological, and nutrient characteristics of the water column in the Mississippi River Delta Bight, June, 1985 to December, 1985

In June 1985, a focused study was initiated to assess the spatial and temporal extent, intensity, and potential causes of oxygen depletion in the northern Gulf of Mexico. Hypoxic bottom waters were studied along two transects (one off Cat Island Pass near Cocodrie and one off Belle Pass off Port Fourchon) in the Mississippi River Delta Bight area. Eight 2-day cruises were conducted aboard the R/V R.J. Russell or the R/V Pelican along these two transects between mid-June and mid-October. Sampling was most intense (bi-weekly) from mid-June through early September. A reduced sampling scheme (4 stations along the Cat Island Pass transect) was continued through the end of the year. In addition, two shelf-wide cruises were conducted from the Mississippi River to the Texas border during July and September

Hydrographic, biological, and nutrient characteristics of the water column on the southeastern Louisiana coast, January, 1986 to November, 1986

In June 1985, a focused study was initiated to assess the spatial and temporal extent, intensity, and potential causes of oxygen depletion in the northern Gulf of Mexico. Hypoxic bottom waters were studied along two transects (one off Cat Island Pass near Cocodrie and one off Belle Pass near Port Fourchon). The number of transects was reduced to one in 1986 (Transect C off Cat Island Pass) and the number of sample periods increased. Sixteen cruises were conducted aboard the R/V Acadiana or the R/V Pelican between late January and mid-November, 1986. Sampling was most intense (bi-weekly) from mid-April through late September. A reduced sampling scheme (four stations) was followed for the first two cruises. In addition a shelf-wide cruise was conducted from the Mississippi River to the Texas border during July, 1986

A Preliminary Mass Balance Model of Primary Productivity and Dissolved Oxygen in the Mississippi River Plume/Inner Gulf Shelf Region

A deterministic, mass balance model for phytoplankton, nutrients, and dissolved oxygen was applied to the Mississippi River Plume/Inner Gulf Shelf (MRP/IGS) region. The model was calibrated to a comprehensive set of field data collected during July 1990 at over 200 sampling stations in the northern Gulf of Mexico. The spatial domain of the model is represented by a three-dimensional, 21-segment water-column .grid extending from the Mississippi River Delta west to the Louisiana-Texas border, and from the shoreline seaward to the 30-60 m bathymetric contours. Diagnostic analyses and numerical experiments were conducted with the calibrated model to better understand the environmental processes controlling primary productivity and dissolved oxygen dynamics in the MRP/IGS region. Underwater light attenuation appears relatively more important than nutrient limitation in controlling rates of primary productivity. Chemical-biological processes appear relatively more important than advective-dispersive transport processes in controlling bottom-water dissolved oxygen dynamics. Oxidation of carbonaceous material in the water column, phytoplankton respiration, and sediment oxygen demand all appear to contribute significantly to total oxygen depletion rates in bottom waters. The estimated contribution of sediment oxygen demand to total oxygen-depletion rates in bottom waters ranges from 22% to 30%. Primary productivity appears to he an important source of dissolved oxygen to bottom waters in the region of the Atchafalaya River discharge and further west along the Louisiana Inner Shelf. Dissolved oxygen concentrations appear very sensitive to changes in underwater light attenuation due to strong coupling between dissolved oxygen and primary productivity in bottom waters. The Louisiana Inner Shelf in the area of the Atchafalaya River discharge and further west to the Texas border appears to be characterized by significantly different light attent, ation-depth-primary productivity relationships than the area immediately west of the Mississippi Delta. Nutrient remineralization in the water column appears to contribute significantly to maintaining chlorophyll concentrations on the Louisiana Inner Shelf