Showing papers presented at "OCEANS Conference in 1989"

High Frequency Sonar Equation Models For Bottom Backscatter And Forward Loss

Abstract: We define models for acoustic bottom reflection and backscattering at frequencies in the range 10-100 kHz and compare them with data from sites having sediment types ranging from sands through clays. The bottom is treated as a fluid without layering or gradients. The reflection loss model simply uses the Rayleigh reflection coefficient, for which the relevant properties of the bottom are summarized in three dimensionless parameters: the sediment/water density ratio, the sediment/water sound speed ratio, and the loss tangent. The backscattering model uses these parameters plus three more. One of these is related to the volume scattering strength of the sediment, and the other two define the power spectral density for bottom roughness. We find the agreement between models and data is generally satisfactory, but that, for soft sediments, the agreement is substantially improved if the density ratio is reduced compared to its measured value. This may indicate that the upper few centimeters of sediment are tenuous, (which is also supported by some detailed geoacoustical measurements), and control high frequency bottom interaction. Suggestions are made for geoacoustic measurements of the uppermost sediment layer and for the incorporation of gradients in future models.

An Acoustic Communication System for Subsea Robot

Abstract: F o r advanced unmanned untethered subsea robots, an acoustic communication system nust be required to transmit the high-definition and real-time video toward the operator on the support ship. Therefore, it is required to realized a high data rate and a low error rate for transmission of the digitized video. A prototype acoustic communication system applying 16-ary quadrature amplitude modulation (16-QAM) method has been developed to perform a capacity of 5 0 0 kbit/s at maximum transmission range of 60 meters. T o improve the quality o f transmission information, an adaptive equalization technique is also ntroduced in this system. The prototype sys em is briefly described and experimental resu ts are presented.

The Sonar Simulation Toolset

Abstract: The Sonar Simulation Toolset, or SST, is a set of object-oriented software components and software development tools for building sonar simulators -“artificial oceans” that sound like a real ocean as “heard” by an existing or proposed sonar system. SST-based simulators produce a digital representation of the predicted signal at a selected point in the receiver’s processing path (typically at each element or beam-former) for a given sonar and environment. The signal includes random fluctuations with controlled statistical properties. The SST is intended to enable a user (programmer) to build a wide variety of applications simply and quickly, with minimal duplication. Thus, the toolset must be highly flexible, modular, portable, reliable, efficient, and tolerant of change. To help achieve these attributes, the principles of object-oriented programming are used as the basis for a library of classes and objects. A class defines a data structure and associated operations; an object is an instance of a class structure containing a particular set of data. SST classes are implemented in C, using mechanisms similar to the X Windows Toolkit. SST objects are C structures initialized at compile time; they may be placed in libraries like subroutines, and configured into application programs at link time. Currently, the package includes models (classes) for several types of beam pattems, pulses, sound propagation, reverberation, scatterers, etc. One of the sound propagation models uses eigenray files produced by the Naval Underwater Systems Center’s Generic Sonar Model, using any of Generic’s sound propagation models. A simple program called REVGEN-SST, which generates a reverberation time series and writes it in a file, is intended as a starting point for userdesigned applications. The current release runs on VAXNMS, VAWNIX, PyramiWNIX, and Cray/CTSS systems.

6, 500m Deep Manned Research Submersible "SHINKAI 6500" System

Abstract: The 6,500m deep manned r e s e a r c h s u b m e r s i b l e " S H I N K A I 6500" and i t s suppor t vessel "YOKOSUKA" a r e now underway on the sea t r i a l s . Since t h e i r launchings they w e r e t e s t e d on t h e i r performances i n d i v i d u a l Iy. They w e r e combined each o t h e r on March 1989 and the sea t r i a l s had been s t a r t e d on A p r i l . The f i n a l sea t r i a l , t e s t d i v e t o the 6,500111 deep, i s scheduled t o be on August 1989 a t Japan Trench o f f Sanriku. T h i s p a p e r d i s c r i b e s t h e o u t l i n e s o f t he submersible and the suppor t vessel b r i e f l y , and then d i s c r i b e s t h e o u t l i n e s o f t h e t e s t r e s u l t s o b t a i n e d upto now.

Characteristics And Effects Of Contaminated Sediments From Southern California

Abstract: A multidisciplinary study of sediments from ten coastal sites in southern California was conducted in summer and fall of 1987. These sites included areas of high contamination near sewage outfalls and within harbors. Measurements were made of metal, chlorinated hydrocarbon, polynuclear aromatic hydrocarbon, and dissolved sulfide concentrations in the sediment surface layer. These sediment samples were also examined for toxicity using three different test methods (Microtox, amphipod survival, and sea urchin growth). Sediment samples were also taken for examination of the benthic macrofauna resident at each site (Fig. 1).

Digital Acoustic Telemetry of Color Video Information

Abstract: High-speed. and reliable telemetry of color video information from an underwater submersible to a support-ship has been developed for real-time deep-sea viewing. Narrow transmission bandwidth caused by low carrier frequency and comparative bandwidth of ultrasonic transducer make it difficult to transfer enormous color video information over long distances in a short time. Moreover, unsteady acoustic channel and Doppler shift make its reliability lower. High-speed and reliable acoustic telemetry with 4-PSK at 20kbitsisec for 25kHz carrier was realized through development of (i) Wideband Transducer with a single matching plate that more than doubles the bandwidth, (ii) Image Coding based on Discrete Cosine Transform(DCT) that reduce color video information to 2bits/pixel, and (iii) Adaptive Equalizer with Phase Controller that removes the intersymbol interference and compensates for the Doppler shift. A field experiment with the test system, beamwidth 35" for source, and 40" for receiver, has sucessfully achieved a 7 second transmission of 256x256 pixels color image at the range of 3,500m.

Light Scattering From Bubbles In Water

Abstract: Scattering properties pertinent to laser light and to optical detection of bubbles are summarized. Colored bands appearing in sunlit subsurface bubble clouds are also discussed. A bubble in water is an example of a scatterer for which the refractive index of the core (gas) is less than that of the surroundings. Bubbles in the ocean may be coated and stabilized by a surfactant film and they can be nonspherical, Bubbles exhibit scattering phenomena which differ significantly from those for drops in air or solid particles in water. Scattering properties were studied in three ways. Calculations were carried out for exact partial-wave (Mie) series solutions when available. Physical-optics approximations were developed for the salient phenomena. Observations were made of laser light scattered at various angles (backscattering, forward scattering, critical angle scattering, and Brewster angle scattering) for bubbles freely rising through water. The transition to total reflection associated with the critical angle and an enhancement of the backscattering analogous to the optical glory of drops were studied in detail. Bubbles sufficiently large to be oblate give rise to novel optical caustics. A minimum in the observed scattering of polarized light near the Brewster angle may be useful for optically discriminating bubbles from particles.

Zooplankton Abundance Measurements From Acoustic Doppler Current Profilers

Abstract: In a pilot intercomparison study, Flagg and :Smith (1989) showed for the first time that under optimal conditions acoustic Doppler current profilers could produce zooplanktonbiomass estimates with considera.ble accuracy and resolution. Optimal meant that the profiler was bottom-mounted and thus operated in a low noise environment, that the 307 kHz operating frequency was relatively high and thus more sensitive to small scatterers, and that there was little chance for variations in size class distributions over the short deployment interval. We have extended the investigation by increasing the data base for intercomparison with a long t:erm deployment during which t.here will be significant. size class changes and by an extension of the techniques to 150 kHz shipboard systems. Preliminary results confirm the pilot study for the bottom-mounted units. The 150 kHz shipboard units have also been shown to produce good results, although they appear to be less sensitive than the 307 kHz units. Progress on sensitivity to size class variations awaits further sample enumerations. INTRODUCTION The advent of the acoustic Doppler current profiler (ADCP) and its wide deployment on ships and moorings, has changed the way many physical and biological measurements are made. The increased vertical resolution of ADCPs and the ability to mount the units on ships have had a significant impact on physical oceanography, changing both the way measurements are made and the types of phenomena under study. Because of the substantially enhanced capabilities of the ADCP, there are now in the field more than 200 units from the major manufacturer, RD Instruments of San Diego. The majority of these are in the United States, and essentially all the major UNOLS vessels now are equipped with ADCPs. Although most of the units have been purchased, maintained, and used by physical oceanographers for water velocity measurements, their ability to monitor the acoustic backscatter, their general accessibility, and their ease of use (these are third or fourth generation instruments) have made them attractive to biological oceanographers for ecological studies. In fact, the ability of the instruments t o measure physical and biological parameters on the same time and space scales has helped foster a renewed interest in interdisciplinary studies. The original designed purpose for the ADCPs was to measure water velocity, and the system was optimized with this in mind. Because at the time there was concern about how t o distinguish the good data from those contaminated by a variety of sources, a number of diagnostic parameters were added to the suite of measured and recorded variables. The intensity of the backscattered signal was included in this list for the purpose of monitoring the signal-to-noise ratio. The fact that zooplankton were the primary acoustic scatterers at frequencies used by the ADCPs led to the recognition that relavant oceanographic information might be contained in the backscatter data. Anecdotal evidence from early ADCP deployments confirmed this concept with descriptions of diel migrations of scattering layers (Schott and Johns, 1987) and vertical distributions that appeared related to mixed layer and euphotic depths (Pettigrew and Irish, personal communication), These first qualitative results suggested changes in effective scatterer densities without providing a clear indication of what particles were actually responsible. The facility with which backscatter measurements were made and the availability of the instruments led to a the pilot study in the spring of 1987 under joint ONR and DOE sponsorship to address the quantitative ability of the ADCPs (Flagg and Smith, 1989, hereafter denoted F&S). To maximize the chance for success, the study plan called for near optimal conditions and modification of the ADCP to maximize its sensitivity. A 307 kHz RD Instruments ADCP was moored on the bottom in 150 meters of water on the shelf south of New England for three days during the spring bloom period of 1987. MOCNESS net tows were then made in a circular path about the 1318 mooring. The use of a bottom-mounted configuration during the study reduced or eliminated noise inherent aboard ship as a consequence of machinery, flow disturbances, bubbles entrained in the water under the ship, and spatial inhomogeneities. The spring period was chosen because of the well documented spring zooplankton bloom on the New England shelf dominated by a single species, Calanus finmarchicus (Smith and Lane, 1988). The horrendous weather limited the useful zooplankton samples to a total of eight which fortunately covered a fairly large dynamic range. The results demonstrated a clear relationship between acoustic backscatter intensity and zooplankton biomass (Figure 2), a finding directly related to the special care exercised in The success of the pilot study led us: 1) to expand the intercomparison data set for the 307 kHz units, 2) to explore the sensitivity of ADCPs to changes in size class distributions, and 3) to extend the study to the shipboard environment. At this writing, the data collection phases for these studies are still in progress. The first two questions are being addressed through a 15-month-long deployment on the shelf edge of the Mid-Atlantic Bight as part of the SEEP-I1 program. The shipboard investigation is part of the BioSYNOP program which focuses on the physical/biological interactions associated with meanders of the Gulf Stream east of Cape Hatteras. In addition to confirming the results of the pilot study, the data gathered thus far show that the shipboard units are capable of usefully resolving biomass changes. The results also indicate a clear decrease in sensitivity/resolution of the 150 kHz units as compared to those operating at 307 kHz. This paper is organized into four sections, geginning with ADCP operation regarding the backscattered signal. There follow a short discussion on techniques used to measure zooplankton abundance, a comparison of the data collected by ADCPs and the nets, and a discussion of the results and questions yet to answered. ADCP OPERATION Acoustic Doppler current profilers operate by emitting a narrow-band acoustic pulse usually from four transducers in a beam, typically 2' to 4' wide. The primary scatterers of the acoustic energy at these frequencies are zooplankton which can be treated in aggregate and over the time interval of the pulse as being passively collecting and processing the acoustic backscatter data. In particular, temperature calibration of the transducers and the associated electronics, and separate processing of each of the beams was clearly required. ~ 1319 advected by the water. Some of the acoustic energy is scattered back toward the ADCP's transducer and a profile through the water is obtained by range gating the return signal into bins. The Doppler shift of the returning signal yields the relative current velocity along the beam axis, while the intensity of the signal i s related to the scatterers' density and their effective acoustic cross-section (c.f. Holliday, 1977; Greenlaw, 1978; Richter, 1985). In our investigations the variable of interest is the backscattered acoustic signal intensity. In the RD Instruments literature the intensity of the return signal is referred to as the echo amplitude, a term that leads to some confusion. Amplitude and intensity are not the same, intensity being the square of the amplitude. The measure of intensity is usually given as 10 times the common logarithm of an intensity ratio, the units of which are decibels (dB) . For active sonars the ratio is usually formed from the return intensity divided by the transmitted intensity. Because the transmitted intensity is not measured in the RD Instrument ADCPs, the intensity ratio actually contains an arbitrary denominator. The backscattered intensity is a by-product of signal conditioning during which the voltage output from the transducers must be amplified to a constant level so that the Doppler processinghardware can function ( F & S ) . This amplification is done in the automatic gain control amplifier (AGC) which has a short response time compared to the usual bin sizes. Thus, the vertical sample interval for intensity is more closely proportional to the transmitted pulse length than to the sample bin size. The status of the AGC is sampled near the end of the bin which skews the location of the backscattered intensity estimate slightly relative to that of the velocity estimate. This slight difference should be taken into account when making attenuation corrections. The substantive difference between the ADCPs used in these studies and norma1 units is that the temperature dependence of the receiver gain has been measured. There are other possible variables which affect the gain, such as pressure, aging, and biofouling, but temperature is by far the most important. At this point it uncertain whether aging has any effect. Also, not all biofouling would measurably affect transducer sensitivity, and in many situations biofouling can be eliminated altogether with proper care. Pressure effects are expected to be small and for most installations would remain essentially constant. Conventional wisdom indicates that the temperature sensitivity of the ADCPs is centered in the analog electronics and not in the transducers themselves (R. Pinkel and F. Rowe, personal communications). For situ units the distinction is immaterial since the entire instrument operates at the same temperature. The same cannot be said for ship-mounted units because the transducers and their preamps are located on the ship bottom while most oE the electronics are in the deck unit and the temperatures at the two loc,itions are generally not the same. Furthermore, while temperature is monitored at the transducer head in order to make velocity of sound estimates, temperature is not measured in the deck unit. Temperature fluctuations of 3’ t

Tributyltin In The Environment: An Overview And Key Issues

Abstract: Tributyltin is an organometallic compound that finds many uses as a biocide. Its most frequent use is in antifoulant boatbottom paints where, occurring alone or usually mixed with copper, it can be extremely effective in preventing fouling of hulls. Its efficacy in controlling fouling results in multimillion dollar savings to the commercial shipping industry in reduced fuel costs and vessel maintenance.

San Francisco Estuary Project

Abstract: On February 24, 1988, the Administrator of the Environmental Protection Agency officially designated the San Francisco Estuary as part of the Agency's National Estuary Program. This action secured EPA support for an effort to address critical environmental problems in the largest estuary on the Pacific Coast of North America. The ultimate product of this effort will be a Comprehensive Conservation and Management Plan to improve the Estuary's water quality and living resources. Implementation of the Plan is scheduled to begin in November, 1992.

Modeling Towed Cable Systems Dynamics

Abstract: : A method for modeling the dynamics of towed cable systems is described. The cable system is assumed to be a multiple branched system with towed bodies. These bodies may be spheres or more general vehicles having a single plane of symmetry. The motion of the two points of the system is arbitrary. The cable is modeled by a series of rigid cylinders connected end-to- end by spherical joints. It is further assumed that the physical parameters of the system and the external forces acting on it can be lumped at the connecting joints. The towed vehicles are three-dimensional bodies with linear (about a steady-state configuration) time-domain analyses. Examples are used to illustrate the analyses.

Mortality, Growth And Bioaccumulation In Mussels Exposed To TBT: Differences Between The Laboratory And The Field

Abstract: Laboratory and field experiments with mussels exposed to TBT were reviewed and compared. Large differences in mussel mortality, growth and bioaccumulation were found. At similar mean TBT concentrations mussel survival in the field was much higher than measured or predicted in laboratory tests. Juvenile mussel growth in the field was about an order of magnitude higher than in the lab at similar concentrations. At concentrations an order of magnitude higher than the lab, growth in the field was about the same. Accumulation of TBT in mussel tissues was similar at high concentrations. At lower concentrations, BCF's calculated from field measurements were about an order of magnitude higher than for the lab. These differences could be attributed to differences in test species, test water, test conditions, and chemical measurements.

Overview Of The Argos System

Abstract: The' ARGOS system provides a satellite based means to collect, locate, and disseminate environmental data. System design allows a user to receive data transmitted from a remote, usually automated platform along with a computed position of that platform. Data is used to support research and applications in such fields as meteorology, oceanography, biology, and hydrology. Development of the system was achieved through a cooperative effort between Centre National d'Etudes Spatiales (CNES, the French Space Agency), NASA, and NOAA, beginning with an agreement signed in 1974. The system became operational in October 1978 with the successful launch of the protoflight satellite NOAA/TIROS-N. An updated bilateral agreement between CNES and NOAA signed in March 1986 insures continued joint cooperation through the rest of the TIROS series, or well into the late1990's. CNES is planning future joint space cooperation with NOAA involving possible additions to the NOAA/ TIROS-N series, and also succeeding generation polar orbiting space platforms.

The Autonomous Conductivity-Temperture Vehicle: First in the Seashuttle Family of Autonomous Underwater Vehicle's for Scientific Payloads

Abstract: The Mark 38 miniature, mobile, sonar target, originally developed for the Navy in 1973 as an expendable training aid for sonar operators, has been redesigned and reconfigured as a robotic underwater vehicle to carry scientific instruments for ocean research. The basic vehicle, named the SEASI-IUTTLE, is nominally 132 cm long, 8.9 cm in diameter and houses a microprocessor controlled guidance system that allows the vehicle to actively position its elevators and rudders in response to data from heading, pitch, roll, and pressure sensors. The vehicle can be programmed to follow complicated prescribed courses of action in five modes of operation: launch, mission, recovery, homing and homing search. It has a nominal speed of 4 kts, an endurance of 2 hrs, and depth tolerance to 250m. The vehicle is equipped with a homing system that returns it to an acoustic beacon, usually deployed at its launch point, at the end of its mission. The SEASHUTTLE provides power and control via a serial interface for instrumentation packages. The SEASHUTTLE has been fitted with a SeaBird CTD for measurements beneath the Arctic ice pack.

Possible Climate Change And Its Impact On Water Supply In California

Abstract: Forecasts of historically large climate changes are being made by global climate modelers with warming of 3 to 8 degrees Fahrenheit (1.5 to 4.5" Celsius) by the middle of the next century. These changes, if they occur, would have profound impact on California's water resources. A substantial shift in runoff patterns would be expected, with l o s s of a large fraction of spring snowmelt. This shift will make it difficult or impossible to fill major multipurpose reservoirs once the flood control season is past, with losses in current water project water yields and hydroelectric power. The predicted rise in sea level would cause problems in the SacramentoSan Joaquin Delta, the hub of major water transfer in the state. There would be increased risk of levee failures in the Delta and a potential increase in salinity intrusion from the ocean which could affect water supplies of the central and southern portions of the state.

32p-Postlabeling Of DNA: A Sensitive Method For Assessing Environmentally Induced Genotoxicity

Abstract: In contaminated environments organisms are exposed to complex mixtures of genotoxic compounds, many of which have not yet been identified. Moreover, for certain genotoxic compounds metabolism to a reactive metabolite(s) is necessary before binding to the genetic material, DNA, can occur. Thus, nonspecific procedures are needed that can detect damage to DNA by a variety of different compounds or their metabolites in animals exposed to these compounds in contaminated environments. The level of covalent binding of genotoxic compounds to DNA in organisms from highly contaminated areas, however, occurs at extremely low levels; thus, central issues for the use of any technique for measuring DNA adducts are the sensitivity of the assay and its applicability to animals exposed to complex mixtures. Presently, the 32P-postlabeling assay (1,2) shows particular promise, because it has a very low limit of detection (1 adduct in 109-1010 nucleotides) and does not require characterization of individual adducts before they are measured, which is an important feature for monitoring studies of marine organisms exposed to complex mixtures of contaminants. There are several versions of the 32P-postlabeling assay reported in the literature (I), and we have used the version that separates xenobiotic-modified nucleotides from normal nucleotides by n-butanol extraction (3 ) ; this increases the sensitivity of the assay by allowing analysis of larger quantities of DNA, and the recovery of adducts with this version of the assay is less dependent on the chemical nature of the adducts than in other versions (4).

Field Evaluation Of Real-Time XBT Systems

Abstract: The use of XBT's to measure the ocean's subsurface temperature has significantly increased over the past decade. NOAA is actively participating in an international effort to increase the number of subsurface temperature observations in support of global oceanographic and climate studies. NOAA's XBT program currently supports more than one hundred voluntary observing ships (VOS) . These vessels are responsible for more than 1 2 , 0 0 0 XBT observations each year. Determining the field performance of XBT data systems is an importance step in the quality control of these data. The purpose of this field test was to evaluate the performance of four XBT systems under field conditions. The systems evaluated were a SEAS I11 (Sippican's MK-9), a Bathy Systems' 810 XBT Controller, an ARGOS XBT system, and Oregon State University's (OSU) XBT Data Box.

Guidance and Control of Unmanned, Untethered Submersible for Rendezvous and Docking with Underwater Station

Abstract: This paper proposes a new concept of underwater unmanned survey system consisting of a mother ship, a launcher, an underwater station(UUS) and a group of unmanned, untethered submersibles (UROVs) t o perform autonomously distributed missions in massive, f a s t and precise manners. Especially, UUS has the autonomous missions of docking with UROVs, charging of those battcries, exchange of informations and watch of UROVs. A new type of UROV recently proposed by one of the authors is employed in this concept t o perform a s table oceanographic underwater investigation on a prearranged course. Control configured vehicle (CCV) techonology is adopted t o perform the swimming at t i tude control. Fuzzy algorithm is applied t o guidance of UROV on a prrearranged course t o reason the collision risk against sea bed and forward obstacles, and t o determine control magnitudes o f CCV modes. A s one of feasibility studies of the proposed underwater unmanned survey system, the guidance of UROV fo r rendezvous and docking with UUS, consisting of rough one t o the neighborhood of UUS, and precise one t o the entrance of UUS is numerically simulated taking the effect of t idal current into account.

Autonomous Long-Term In-Situ Particle Sizing Using A New Laser Diffraction Instrument

Abstract: A new sensor system is described for unattended long-term observation of particle size spectra in the sea. The instrument is based on the principle that, at small angles, scattering by a particle is substantially identical to diffraction through an aperture of equal diameter, regardless of the particle refractive index. A CCD array records near-forward scattering of light from a laser beam. The inversion of observed scattered intensity over a range of small angles is required to obtain size data. A survey of the inverse methods is included. The data from the CCD line array permits a new level of detail in analysis of the in-situ data. The sensor system can be easily programmed for an arbitrary schedule of sampling. Furthermore, by incorporating the concepts of a settling tube, the settling velocity spectrum of the particles can be determined independently.

Surface Wind Stress From Global Atmospheric Analyses

Abstract: Evaluations and comparisons of global analyses from the European Centre for Medium Range Weather Forecasts (ECMWF) and the U.S. National Meteorological Center (NMC) have allowed an appreciation to be gained of the characteristics, problems and errors in these data sets. For surface wind, the ECMWF 1000 mb analyses are regarded as most suitable for computing surface wind stresses over the global oceans because ship data were applied directly at 1000 mb prior to September 1986. The global analyses use a four-dimensional data assimilation system and have the advantage of high spatial and temporal (twice daily) resolution. New climatologies of surface wind stress, the curl of the wind stress, and the Sverdrup transport streamfunctions have been computed based on 1980-1986 analyses. The wind stress was computed using a wind speed and surface atmospheric stability dependent drag coefficient from Large and Pond, and the effective mean drag coefficient required to convert a pseudostress into a stress has been evaluated as a function of location and time of year. Comparisons with the Hellerman and Rosenstein wind stress climatology reveal surprising similarities overall in view of the different drag coefficients used, but there are also huge differences, especially over the entire southern oceans, where the new results are believed to be the best available. As well as the long-term annual and monthly means, interannual variations have also been analyzed.

An Autonomous Submersible Designed for Software Development

Abstract: 'Sea Grant College Program, Massachusetts Institute of Technology, 292 Main Street, Cambridge, Massachusetts 02139 Vharles Stark Draper Laboratory, 555 Technology Square, Cambridge, Massachusetts 02139 3Department of Ocean Engineering, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139 41nternationaI Submarine Engineering, I734 Broadway Street, Port Coquitlum, British Columbia, Canada V3C 2M8

Global Surface Wind Vectors Resulting From The Assimilation Of Satellite Wind Speed Data In Atmospheric General Circulation Models

Abstract: Methodology for assigning direction to satel l i te surface wind speed data has been developed and tested. Results from these tests show the relative accuracy of each approach and indicate that this methodology should enable the assimilation of currently available SMMR, SSM/I and Geosat wind speed observations.

Low Cost Rov's for Science

Abstract: NOAA's National Undersea Research Center at The University of Connecticut is the national center for test and evaluation of low cost remote operated vehicles (LCROV's) for scientific applications. Since 1984, we have evaluated and developed procedures and tools for utilizing LCROV technology to address a wide variety of sampling tasks. include: video transect calibration and enumeration techniques, volumetric plankton imaging, downweight/tool/sample receptacle, tube cores, scoop sampler integrated to a simple manipulator, water pump sampler, suction sampler, and several sensor packages. Examples of research missions that this technology addresses include: definition of juvenile finfish and crustacean micro-habitat requirements, studies of the horizontal distribution of demersal zooplankton, hypoxia and ocean dumping impacts, deep sound scattering layer definition, ground truthing of surficial geology from remote survey methods, and hydrothermal vent processes. We have conducted operations off the northeast coast of the U.S., the Laurentian Great Lakes, Gulf of Alaska, Hawaii, the Rift Lake Valley of East Africa, and Israel, demonstrating the utility of ROVs for use off vessels of opportunity and in remote areas. LCROV's are easily transportable and deployed undersea platforms that can deliver specially designed sampling devices and cameras to depths up to 330 meters.

Topographic Features Of The L'mafla Continental Shelf, Northern Gulf Of Mexico

Abstract: Topographic features of a hardbottom nature are common on the L'MAFLA shelf. They range from low relief (<2m) northwest trending linear ridges constructed of sand and shell gravel and occasional rock rubble to isolated outcrops or erosional remnants of indurated material on the inner shelf to low to high (up to 15-18m) relief patch reefs, linear ridges ann innacles on the outer shelf and shelf break. These hardgottom features provide substrate for sessile epifauna not ordinarily found on the more extensive areas of unconsolidated sediment on the L'MAFLA shelf.

Fate Of Tributyltin

Abstract: The degradation of TBT in natural waters is primarily due to biological processes resulting in TBT half-lives ranging from 4 to 14 days. In upper waters with high nutrient levels, microalgae or bottom plants can be important in TBT degradation. Biological TBT degradation in sunlight resulted in the production of various hydroxybutyldibutyltins. TBT half-life in sunlit estuarine water supplemented with nutrients was 1 day. Fine-grained sediments can catalyze the non-biological dealkylation of TBT to form monobutyltin and inorganic tin. The half-lives of TBT added to fine-grained sediments ranged from 2 to 4 days. Biological, i.e. microbial, degradation of TBT added to sandy sediments resulted in longer half-lives, e.g. 13 days for one sandy area. Further work is required to assess the fate of TBT in anaerobic sediments and the TBT associated with paint chips in the sediments. INTRODUCTION The fate of tributyltin, like other toxic organics, is determined by various physical, chemical and biological processes. Photolysis and biological degradation act to modify TBT in coastal waters. Some of the TBT adsorbs to suspended particulates and these particulates can be carried to the bottom by sedimentation. Chemical and biological degradation can degrade TBT in sediment to various metabolic products. Since the fate of TBT has recently been reviewed (Maguire, 1987; Seligman et al., 1989), this article briefly discusses processes affecting the fate of TBT and describes in more detail the latest work on TBT degradation in both sediment and water. Fate of TBT in Water At TBT concentrations of 1 pg/liter or less, there was biological degradation resulting in TBT half-lives of 414 days (Francois et al., 1989; Hattori et al., 1987; Hinga et a1.,1987; Olson and Brinckman, 1986; Seligman et al., 1989; Thain et al., 1987). At high TBT concentrations (= 1 mgfliter) degradation was very slow, presumably due to inhibition of TBT-degrading microorganisms (Seligman et al., 1986). In the dark bacteria and fungi are important in TBT degradation. Recent studies have shown that photosynthetic organisms in natural waters play an important role in TBT degradation (Francois et al., 1989; Lee et al., 1989; Olson and Brinkman, 1986). These studies demonstrated higher TBT degradation in sunlit estuarine water compared with dark degradation rates (Table l), production of hydroxybutyldibutyltins in the light but not in the dark (Table 2), and metabolism of TBT to dibutyltin and hydroxylated metabolites by cultures of diatoms and dinoflagellates (Table 3). Maguire et al. (1984) found that the freshwater green algae, Ankistrodesmus falcatus, degraded TBT to dibutyltin, a small amount of butyltin and inorganic tin. The marine green algae (Dunaliella tertiolecta) and chrysophytes (Isochrysis galbana and Cricosphuera ricoco) showed a very limited ability to degrade TBT (Table 2). Both diatom cultures and sunlit natural waters with added TBT produced hydroxybutyldibutyltin compounds, which included delta-hydroxybutyldibutyltin, gammahydroxybutyldibutyltin, and beta-hydroxybutyldibutyltin (Table 2). There was a significant increase in TBT when nitrate was added to estuarine water before light exposure. The TBT half-life was 1 day in nitrate supplemented water. There was no increase in TBT degradation when nitrate was added to water kept in the dark. Eel grass (Zostera marina) found in intertidal areas can degrade TBT to diand monobutyltin (Francois et al., 1989). The half-lives of TBT in eelgrass under light and dark were 6.7 days and 13.8 days, respectively. Sunlight photolysis of TBT was relatively slow (half-life = 90 days, Maguire et al., 1983), since TBT absorbs in the ultra-violet region. Sterilization of estuarine water before adding TBT followed by incubation under sunlight resulted in no significant degradation of TBT after 6 days (Lee et al., 1989). Possibly, TBT found in the surface microlayer (Maguire and Tkacz, 1987) could be more rapidly degraded by direct photolysis. Fate of TBT in Sediment TBT adsorbed to suspended particulates in the water can enter the bottom by sedimentation processes. The TBT can gradually desorb from these particles (Unger et al., 1988). In areas Table 1 Degradation of Radiolabeled and Nonlabeled Tributyltin (TBT) Added to Estuarine Water from Skidaway River (Savannah, GA) (Data from Lee et al., 1989) Initial TBT Month/ TBT Concentration Treatment Temperature Half-life (Witer) (days) 0.5 (unlabeled) Light Sept./28-29"C 6 0.91 (unlabeled) Dark SeptJ28-29OC 9 1.5 (labeled) Light AugJ29"C 6 1.5 (labeled) Dark Aug.129"C 10 1.30 (unlabeled) Light Feb./lZ"C 7 1.60 (unlabeled) Dark Feb.ll2OC 11 1.5 (labeled) Light Jan./l 1°C 8 1.5 (labeled) Dark Jan./l 1 "C 13 0.4 (labeled) Light July/28 "C 3 0.4 (labeled) Dark July128 "C 7 512

A Comparison Of Recursive Weighted Least Squares Estimation And Kalman Filtering For Source Dynamic Motion Evaluation

Abstract: The problem of compensating for underwater motion effects (heave component) arises in a number of areas of current interest. Two models of the heave process are discussed. In the first, frequency-response-based higher-order models, including lead-lag factors, are obtained as a prelude to the application of the standard Kalman filter to estimate the heave component. The second model involves the discrete autoregressive moving average with external variables (ARMAX) form. The author proposes the use of the recursive weighted least squares (RWLS) algorithm to solve the filtering problem on the basis of the ARMAX model. The algorithm is simpler than Kalman filtering in terms of the required knowledge of noise statistics, and thus provides an attractive alternative to Kalman filtering. The relation between the RWLS technique and Kalman filtering is explored. Computational results pertaining to the performance of the RWLS technique are given, and the effects of the method's weighting functions are discussed.