Advances in satellite oceanography

NASA Technical Reports Server (NTRS)

Brown, O. B.; Cheney, R. E.

1983-01-01

Technical advances and recent applications of active and passive satellite remote sensing techniques to the study of oceanic processes are summarized. The general themes include infrared and visible radiometry, active and passive microwave sensors, and buoy location systems. The surface parameters of sea surface temperature, windstream, sea state, altimetry, color, and ice are treated as applicable under each of the general methods.

FIRE_AX_PSU_MALBAL

Atmospheric Science Data Center

2015-11-24

... Parameters:  Clouds Irradiance Latent Heat Flux Liquid Water Content Precipitation Rate Sea Surface ... Solar Transmittance Specific Humidity Surface Stress System Optical Depth Temperature Wind Direction Wind Speed ...

Dynamic sea surface topography from GEOS-3 altimetry - Determination of some dominant parameters

NASA Technical Reports Server (NTRS)

Mather, R. S.; Lerch, F. J.; Rizos, C.; Masters, E. G.; Hirsch, B.

1979-01-01

The second, third and fourth degree zonal harmonics of the quasi-stationary dynamic sea surface topography can be recovered from the GEOS-3 altimetry despite the adverse levels of noise indicated by the crossover discrepancies generated from the best orbits available at the end of 1977 and the GEOS-3 altimetry. Techniques for modelling the global sea surface topography are discussed along with methods for signal recovery in the presence of significant levels of noise. The analysis also provides a means of defining the geocentricity of the system of reference used in preparing the GEOS-3 ephemeris.

Current Status and Future Plan of Arctic Sea Ice monitoring in South Korea

NASA Astrophysics Data System (ADS)

Shin, J.; Park, J.

2016-12-01

Arctic sea ice is one of the most important parameters in climate. For monitoring of sea ice changes, the National Meteorological Satellite Center (NMSC) of Korea Metrological Administration has developed the "Arctic sea ice monitoring system" to retrieve the sea ice extent and surface roughness using microwave sensor data, and statistical prediction model for Arctic sea ice extent. This system has been implemented to the web site for real-time public service. The sea ice information can be retrieved using the spaceborne microwave sensor-Special Sensor Microwave Imager/Sounder (SSMI/S). The sea ice information like sea ice extent, sea ice surface roughness, and predictive sea ice extent are produced weekly base since 2007. We also publish the "Analysis report of the Arctic sea ice" twice a year. We are trying to add more sea ice information into this system. Details of current status and future plan of Arctic sea ice monitoring and the methodology of the sea ice information retrievals will be presented in the meeting.

Determining wave direction using curvature parameters.

PubMed

de Queiroz, Eduardo Vitarelli; de Carvalho, João Luiz Baptista

2016-01-01

The curvature of the sea wave was tested as a parameter for estimating wave direction in the search for better results in estimates of wave direction in shallow waters, where waves of different sizes, frequencies and directions intersect and it is difficult to characterize. We used numerical simulations of the sea surface to determine wave direction calculated from the curvature of the waves. Using 1000 numerical simulations, the statistical variability of the wave direction was determined. The results showed good performance by the curvature parameter for estimating wave direction. Accuracy in the estimates was improved by including wave slope parameters in addition to curvature. The results indicate that the curvature is a promising technique to estimate wave directions.•In this study, the accuracy and precision of curvature parameters to measure wave direction are analyzed using a model simulation that generates 1000 wave records with directional resolution.•The model allows the simultaneous simulation of time-series wave properties such as sea surface elevation, slope and curvature and they were used to analyze the variability of estimated directions.•The simultaneous acquisition of slope and curvature parameters can contribute to estimates wave direction, thus increasing accuracy and precision of results.

Land-Sea relationships of climate-related records: example of the Holocene in the eastern Canadian Arctic and Greenland

NASA Astrophysics Data System (ADS)

de Vernal, Anne; Fréchette, Bianca; Hillaire-Marcel, Claude

2017-04-01

Anne de Vernal, Bianca Fréchette, Claude Hillaire-Marcel Important progresses have been made to reconstruct climate and ocean changes through time. However, there is often a hiatus between the land-based climate reconstructions and paleoceanographical data. The reconstructed parameters are not the same (e.g. surface air temperature vs. sea-surface temperature). Moreover, the spatial (local to regional) and temporal dimensions (seasonal, annual to multi-decadal) of proxy-data are often inconsistent, thus preventing direct correlation of time series and often leading to uncertainties in multi-site, multi-proxy compilations. Here, we address the issue of land-sea relationships in the eastern Canadian Arctic-Baffin Bay-Labrador Sea-western Greenland based on the examination of different climate-related information from marine cores (dinocysts) collected nearshore vs. offshore, ice cores (isotopes), fjord and lake data (pollen). The combined information tends to indicate that "climate" changes are not easily neither adequately captured by temperature and temperature shifts. However, the seasonal contrast of temperatures seems to be a key parameter. Whereas it is often attenuated offshore, it is generally easy to reconstruct nearshore, where water stratification is usually stronger. The confrontation of data also shows a relationship between ice core data and sea-ice cover and/or sea-surface salinity, suggesting that air-sea exchanges in basins surrounding ice sheets play a significant role with respect to their isotopic composition. On the whole, combined onshore-offshore data consistently suggest a two-step shift towards optimal summer and winter conditions the circum Baffin Bay and northern Labrador Sea at 7.5 and 6 ka BP. These delayed optimal conditions seem to result from ice-meltwater discharges maintaining low salinity conditions in marine surface waters and thus a strong seasonality.

On the relationship between water vapor over the oceans and sea surface temperature

NASA Technical Reports Server (NTRS)

Stephens, Graeme L.

1990-01-01

Monthly mean precipitable water data obtained from passive microwave radiometry were correlated with the National Meteorological Center (NMC) blended sea surface temperature data. It is shown that the monthly mean water vapor content of the atmosphere above the oceans can generally be prescribed from the sea surface temperature with a standard deviation of 0.36 g/sq cm. The form of the relationship between precipitable water and sea surface temperature in the range T (sub s) greater than 18 C also resembles that predicted from simple arguments based on the Clausius-Clapeyron relationship. The annual cycle of the globally integrated mass of Scanning Multichannel Microwave Radiometer (SMMR) water vapor is shown to differ from analyses of other water vapor data in both phase and amplitude and these differences point to a significant influence of the continents on water vapor. Regional scale analyses of water vapor demonstrate that monthly averaged water vapor data, when contrasted with the bulk sea surface temperature relationship developed in this study, reflect various known characteristics of the time mean large-scale circulation over the oceans. A water vapor parameter is introduced to highlight the effects of large-scale motion on atmospheric water vapor. Based on the magnitude of this parameter, it is shown that the effects of large-scale flow on precipitable water vapor are regionally dependent, but for the most part, the influence of circulation is generally less than about + or - 20 percent of the seasonal mean.

On the relationship between water vapor over the oceans and sea surface temperature

NASA Technical Reports Server (NTRS)

Stephens, Graeme L.

1989-01-01

Monthly mean precipitable water data obtained from passive microwave radiometry were correlated with the National Meteorological Center (NMC) blended sea surface temperature data. It is shown that the monthly mean water vapor content of the atmosphere above the oceans can generally be prescribed from the sea surface temperature with a standard deviation of 0.36 g/sq cm. The form of the relationship between precipitable water and sea surface temperature in the range T(sub s) greater than 18 C also resembles that predicted from simple arguments based on the Clausius-Clapeyron relationship. The annual cycle of the globally integrated mass of Scanning Multichannel Microwave Radiometer (SMMR) water vapor is shown to differ from analyses of other water vapor data in both phase and amplitude and these differences point to a significant influence of the continents on water vapor. Regional scale analyses of water vapor demonstrate that monthly averaged water vapor data, when contrasted with the bulk sea surface temperature relationship developed in this study, reflect various known characteristics of the time mean large-scale circulation over the oceans. A water vapor parameter is introduced to highlight the effects of large-scale motion on atmospheric water vapor. Based on the magnitude of this parameter, it is shown that the effects of large-scale flow on precipitable water vapor are regionally dependent, but for the most part, the influence of circulation is generally less than about + or - 20 percent of the seasonal mean.

Characteristics of ocean-reflected short radar pulses with application to altimetry and surface roughness determination

NASA Technical Reports Server (NTRS)

Miller, L. S.; Hayne, G. S.

1972-01-01

Current work related to geodetic altimetry is summarized. Special emphasis is placed on the effects of pulse length on both altimetry and sea-state estimation. Some discussion is also given of system tradeoff parameters and sea truth requirements to support scattering studies. The problem of analyzing signal characteristics and altimeter waveforms arising from rough surface backscattering is also considered.

The annual and interannual variabilities of precipitable water, surface wind speed, and sea surface temperature over the tropical Pacific

NASA Technical Reports Server (NTRS)

Liu, W. Timothy

1989-01-01

The Nimbus-7 Scanning Multichannel Microwave Radiometer (SSMR) provided simultaneous measurements of three geophysical parameters, each of which describing a certain aspect of the evolution of the 1982-1983 ENSO: the sea-surface temperature (T), precipitable water (W), and surface-wind speed (U). In this paper, values derived from the SSMR were compared with in situ measurements from ships, research buoys, and operational island stations in the tropical Pacific between January 1980 and October 1983, demonstrating the temporal and spatial coherence of the SSMR measurements. The results show that the variabilities of the surface convergence, sea surface temperature, and precipitable water are related. It was found that W anomalies were not always colocated with T anomalies, and that W anomalies were often associated with negative U anomalies, interpreted as surface convergence.

X-Band wave radar system for monitoring and risk management of the coastal infrastructures

NASA Astrophysics Data System (ADS)

Ludeno, Giovanni; Soldovieri, Francesco; Serafino, Francesco

2017-04-01

The presence of the infrastructures in coastal region entails an increase of the sea level and the shift of the sediment on the bottom with a continuous change of the coastline. In order to preserve the coastline, it has been necessary to resort the use of applications coastal engineering, as the construction of the breakwaters for preventing the coastal erosion. In this frame, the knowledge of the sea state parameters, as wavelength, period and significant wave height and of surface current and bathymetry can be used for the harbor operations and to prevent environmental disasters. In the last years, the study of the coastal phenomena and monitoring of the sea waves impact on the coastal infrastructures through the analysis of images acquired by marine X-band radars is of great interest [1-3]. The possibility to observe the sea surface from radar images is due to the fact that the X-band electromagnetic waves interact with the sea capillary waves (Bragg resonance), which ride on the gravity waves. However, the image acquired by a X-band radar is not the direct representation of the sea state, but it represents the sea surface as seen by the radar. Accordingly, to estimate the sea state parameters as, direction, wavelength, period of dominant waves, the significant wave height as well as the bathymetry and surface current, through a time stack of radar data are required advanced data processing procedures. In particular, in the coastal areas due to the non-uniformity of sea surface current and bathymetry fields is necessary a local analysis of the sea state parameters. In order to analyze the data acquired in coastal area an inversion procedure defined "Local Method" is adopted, which is based on the spatial partitioning of the investigated area in partially overlapping sub-areas. In addition, the analysis of the sea spectrum of each sub-area allows us to retrieve the local sea state parameters. In particular, this local analysis allows us to detect the reflected waves from the coastal infrastructures, e.g. from the harbor jetties. In fact, the reflected waves may significantly complicate the harbour activities (e.g., berthing operations), as they interfere with the oncoming waves thus creating a confused sea [2]. References [1] G. Ludeno, C. Brandini, C. Lugni, D. Arturi, A. Natale, F. Soldovieri, B. Gozzini, F. Serafino, "Remocean System for the Detection of the Reflected Waves from the Costa Concordia Ship Wreck", IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, Vol.7, no.3, pp.3011-3018, July 2014. [2] G. Ludeno, F. Reale, F. Dentale, E. Pugliese Carratelli, A. Natale, F. Soldovieri, F. Serafino "An X-Band Radar System for Bathymetry and Wave Field Analysis in Harbor Area", Sensors, Vol.15, no.1, pp. 1691-1707, January 2015. [3] F. Raffa, G. Ludeno, B. Patti, F. Soldovieri, S. Mazzola, and F. Serafino, "X-band wave radar for coastal upwelling detection off the southern coast of Sicily.", Journal of Atmospheric and Oceanic Technology, January 2017, Vol. 34, No. 1, Published online on 22 Dec 2016.

An observational philosophy for GEOS-C satellite altimetry

NASA Technical Reports Server (NTRS)

Weiffenbach, G. C.

1972-01-01

The parameters necessary for obtaining a 10 cm accuracy for GEOS-C satellite altimetry are outlined. These data include oceanographic parameters, instrument calibration, pulse propagation, sea surface effects, and optimum design.

Results of the Second SeaWiFS Data Analysis Round Robin, March 2000 (DARR-00)

NASA Technical Reports Server (NTRS)

Hooker, Stanford B. (Editor); Firestone, Elaine R. (Editor); Zibordi, Giuseppe; Berthon, Jean-Francois; D'Alimonte, Davide; Maritorena, Stephane; McLean, Scott; Sildam, Juri; McClain, Charles R. (Technical Monitor)

2001-01-01

The accurate determination of upper ocean apparent optical properties (AOPs) is essential for the vicarious calibration of the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) instrument and the validation of the derived data products. To evaluate the importance of data analysis methods upon derived AOP values, the Second Data Analysis Round Robin (DARR-00) activity was planned during the latter half of 1999 and executed during March 2000. The focus of the study was the intercomparison of several standard AOP parameters: (1) the upwelled radiance immediately below the sea surface, L(sub u)(0(-),lambda); (2) the downward irradiance immediately below the sea surface, E(sub d)(0(-),lambda); (3) the diffuse attenuation coefficients from the upwelling radiance and the downward irradiance profiles, L(sub L)(lambda) and K(sub d)(lambda), respectively; (4) the incident solar irradiance immediately above the sea surface, E(sub d)(0(+),lambda); (5) the remote sensing reflectance, R(sub rs)(lambda); (6) the normalized water-leaving radiance, [L(sub W)(lambda)](sub N); (7) the upward irradiance immediately below the sea surface, E(sub u)(0(-)), which is used with the upwelled radiance to derive the nadir Q-factor immediately below the sea surface, Q(sub n)(0(-),lambda); and (8) ancillary parameters like the solar zenith angle, theta, and the total chlorophyll concentration, C(sub Ta), derived from the optical data through statistical algorithms. In the results reported here, different methodologies from three research groups were applied to an identical set of 40 multispectral casts in order to evaluate the degree to which differences in data analysis methods influence AOP estimation, and whether any general improvements can be made. The overall results of DARR-00 are presented in Chapter 1 and the individual methods used by the three groups and their data processors are presented in Chapters 2-4.

Contents of the JPL Distributed Active Archive Center (DAAC) archive, version 2-91

NASA Technical Reports Server (NTRS)

Smith, Elizabeth A. (Editor); Lassanyi, Ruby A. (Editor)

1991-01-01

The Distributed Active Archive Center (DAAC) archive at the Jet Propulsion Laboratory (JPL) includes satellite data sets for the ocean sciences and global change research to facilitate multidisciplinary use of satellite ocean data. Parameters include sea surface height, surface wind vector, sea surface temperature, atmospheric liquid water, and surface pigment concentration. The Jet Propulsion Laboratory DAAC is an element of the Earth Observing System Data and Information System (EOSDIS) and will be the United States distribution site for the Ocean Topography Experiment (TOPEX)/POSEIDON data and metadata.

Sea Oil Spill Detection Using Self-Similarity Parameter of Polarimetric SAR Data

NASA Astrophysics Data System (ADS)

Tong, S.; Chen, Q.; Liu, X.

2018-04-01

The ocean oil spills cause serious damage to the marine ecosystem. Polarimetric Synthetic Aperture Radar (SAR) is an important mean for oil spill detections on sea surface. The major challenge is how to distinguish oil slicks from look-alikes effectively. In this paper, a new parameter called self-similarity parameter, which is sensitive to the scattering mechanism of oil slicks, is introduced to identify oil slicks and reduce false alarm caused by look-alikes. Self-similarity parameter is small in oil slicks region and it is large in sea region or look-alikes region. So, this parameter can be used to detect oil slicks from look-alikes and water. In addition, evaluations and comparisons were conducted with one Radarsat-2 image and two SIR-C images. The experimental results demonstrate the effectiveness of the self-similarity parameter for oil spill detection.

Optimisation of sea surface current retrieval using a maximum cross correlation technique on modelled sea surface temperature

NASA Astrophysics Data System (ADS)

Heuzé, Céline; Eriksson, Leif; Carvajal, Gisela

2017-04-01

Using sea surface temperature from satellite images to retrieve sea surface currents is not a new idea, but so far its operational near-real time implementation has not been possible. Validation studies are too region-specific or uncertain, due to the errors induced by the images themselves. Moreover, the sensitivity of the most common retrieval method, the maximum cross correlation, to the three parameters that have to be set is unknown. Using model outputs instead of satellite images, biases induced by this method are assessed here, for four different seas of Western Europe, and the best of nine settings and eight temporal resolutions are determined. For all regions, tracking a small 5 km pattern from the first image over a large 30 km region around its original location on a second image, separated from the first image by 6 to 9 hours returned the most accurate results. Moreover, for all regions, the problem is not inaccurate results but missing results, where the velocity is too low to be picked by the retrieval. The results are consistent both with limitations caused by ocean surface current dynamics and with the available satellite technology, indicating that automated sea surface current retrieval from sea surface temperature images is feasible now, for search and rescue operations, pollution confinement or even for more energy efficient and comfortable ship navigation.

Ocean Surface Carbon Dioxide Fugacity Observed from Space

NASA Technical Reports Server (NTRS)

Liu, W. Timothy; Xie, Xiaosu

2014-01-01

We have developed and validated a statistical model to estimate the fugacity (or partial pressure) of carbon dioxide (CO2) at sea surface (pCO2sea) from space-based observations of sea surface temperature (SST), chlorophyll, and salinity. More than a quarter million in situ measurements coincident with satellite data were compiled to train and validate the model. We have produced and made accessible 9 years (2002-2010) of the pCO2sea at 0.5 degree resolutions daily over the global ocean. The results help to identify uncertainties in current JPL Carbon Monitoring System (CMS) model-based and bottom-up estimates over the ocean. The utility of the data to reveal multi-year and regional variability of the fugacity in relation to prevalent oceanic parameters is demonstrated.

Improving NOAA's NWLON Through Enhanced Data Inputs from NASA's Ocean Surface Topography

NASA Technical Reports Server (NTRS)

Guest, DeNeice C.

2010-01-01

This report assesses the benefit of incorporating NASA's OSTM (Ocean Surface Topography Mission) altimeter data (C- and Ku-band) into NOAA's (National Oceanic and Atmospheric Administration) NWLON (National Water Level Observation Network) DSS (Decision Support System). This data will enhance the NWLON DSS by providing additional inforrnation because not all stations collect all meteorological parameters (sea-surface height, ocean tides, wave height, and wind speed over waves). OSTM will also provide data where NWLON stations are not present. OSTM will provide data on seasurface heights for determining sea-level rise and ocean circulation. Researchers and operational users currently use satellite altimeter data products with the GSFCOO NASA data model to obtain sea-surface height and ocean circulation inforrnation. Accurate and tirnely inforrnation concerning sea-level height, tide, and ocean currents is needed to irnprove coastal tidal predictions, tsunarni and storm surge warnings, and wetland restoration.

The conservative behavior of dissolved organic carbon in surface waters of the southern Chukchi Sea, Arctic Ocean, during early summer

PubMed Central

Tanaka, Kazuki; Takesue, Nobuyuki; Nishioka, Jun; Kondo, Yoshiko; Ooki, Atsushi; Kuma, Kenshi; Hirawake, Toru; Yamashita, Youhei

2016-01-01

The spatial distribution of dissolved organic carbon (DOC) concentrations and the optical properties of dissolved organic matter (DOM) determined by ultraviolet-visible absorbance and fluorescence spectroscopy were measured in surface waters of the southern Chukchi Sea, western Arctic Ocean, during the early summer of 2013. Neither the DOC concentration nor the optical parameters of the DOM correlated with salinity. Principal component analysis using the DOM optical parameters clearly separated the DOM sources. A significant linear relationship was evident between the DOC and the principal component score for specific water masses, indicating that a high DOC level was related to a terrigenous source, whereas a low DOC level was related to a marine source. Relationships between the DOC and the principal component scores of the surface waters of the southern Chukchi Sea implied that the major factor controlling the distribution of DOC concentrations was the mixing of plural water masses rather than local production and degradation. PMID:27658444

The Relationship Between Arctic Sea Ice Albedo and the Geophysical Parameters of the Ice Cover

NASA Astrophysics Data System (ADS)

Riihelä, A.

2015-12-01

The Arctic sea ice cover is thinning and retreating. Remote sensing observations have also shown that the mean albedo of the remaining ice cover is decreasing on decadal time scales, albeit with significant annual variability (Riihelä et al., 2013, Pistone et al., 2014). Attribution of the albedo decrease between its different drivers, such as decreasing ice concentration and enhanced surface melt of the ice, remains an important research question for the forecasting of future conditions of the ice cover. A necessary step towards this goal is understanding the relationships between Arctic sea ice albedo and the geophysical parameters of the ice cover. Particularly the question of the relationship between sea ice albedo and ice age is both interesting and not widely studied. The recent changes in the Arctic sea ice zone have led to a substantial decrease of its multi-year sea ice, as old ice melts and is replaced by first-year ice during the next freezing season. It is generally known that younger sea ice tends to have a lower albedo than older ice because of several reasons, such as wetter snow cover and enhanced melt ponding. However, the quantitative correlation between sea ice age and sea ice albedo has not been extensively studied to date, excepting in-situ measurement based studies which are, by necessity, focused on a limited area of the Arctic Ocean (Perovich and Polashenski, 2012).In this study, I analyze the dependencies of Arctic sea ice albedo relative to the geophysical parameters of the ice field. I use remote sensing datasets such as the CM SAF CLARA-A1 (Karlsson et al., 2013) and the NASA MeaSUREs (Anderson et al., 2014) as data sources for the analysis. The studied period is 1982-2009. The datasets are spatiotemporally collocated and analysed. The changes in sea ice albedo as a function of sea ice age are presented for the whole Arctic Ocean and for potentially interesting marginal sea cases. This allows us to see if the the albedo of the older sea ice in the central parts of the Arctic Ocean is resistant to the decreasing overall trend.A similar analysis is also extended to ice concentration, melt season length and other appropriate parameters describing the surface conditions. The results of the analyses are summed up to provide an assessment of the relative impact strengths of the ice field parameters on the albedo.

Estimation of Global Subsurface Thermal Structure from Satellite Remote Sensing Observations Based on Machine Learning

NASA Astrophysics Data System (ADS)

Su, H.; Yan, X. H.

2017-12-01

Subsurface thermal structure of the global ocean is a key factor that reflects the impact of the global climate variability and change. Accurately determining and describing the global subsurface and deeper ocean thermal structure from satellite measurements is becoming even more important for understanding the ocean interior anomaly and dynamic processes during recent global warming and hiatus. It is essential but challenging to determine the extent to which such surface remote sensing observations can be used to develop information about the global ocean interior. This study proposed a Support Vector Regression (SVR) method to estimate Subsurface Temperature Anomaly (STA) in the global ocean. The SVR model can well estimate the global STA upper 1000 m through a suite of satellite remote sensing observations of sea surface parameters (including Sea Surface Height Anomaly (SSHA), Sea Surface Temperature Anomaly (SSTA), Sea Surface Salinity Anomaly (SSSA) and Sea Surface Wind Anomaly (SSWA)) with in situ Argo data for training and testing at different depth levels. Here, we employed the MSE and R2 to assess SVR performance on the STA estimation. The results from the SVR model were validated for the accuracy and reliability using the worldwide Argo STA data. The average MSE and R2 of the 15 levels are 0.0090 / 0.0086 / 0.0087 and 0.443 / 0.457 / 0.485 for 2-attributes (SSHA, SSTA) / 3-attributes (SSHA, SSTA, SSSA) / 4-attributes (SSHA, SSTA, SSSA, SSWA) SVR, respectively. The estimation accuracy was improved by including SSSA and SSWA for SVR input (MSE decreased by 0.4% / 0.3% and R2 increased by 1.4% / 4.2% on average). While, the estimation accuracy gradually decreased with the increase of the depth from 500 m. The results showed that SSSA and SSWA, in addition to SSTA and SSHA, are useful parameters that can help estimate the subsurface thermal structure, as well as improve the STA estimation accuracy. In future, we can figure out more potential and useful sea surface parameters from satellite remote sensing as input attributes so as to further improve the STA sensing accuracy from machine learning. This study can provide a helpful technique for studying thermal variability in the ocean interior which has played an important role in recent global warming and hiatus from satellite observations over global scale.

Estimating temporal and spatial variation of ocean surface pCO2 in the North Pacific using a self-organizing map neural network technique

NASA Astrophysics Data System (ADS)

Nakaoka, S.; Telszewski, M.; Nojiri, Y.; Yasunaka, S.; Miyazaki, C.; Mukai, H.; Usui, N.

2013-09-01

This study uses a neural network technique to produce maps of the partial pressure of oceanic carbon dioxide (pCO2sea) in the North Pacific on a 0.25° latitude × 0.25° longitude grid from 2002 to 2008. The pCO2sea distribution was computed using a self-organizing map (SOM) originally utilized to map the pCO2sea in the North Atlantic. Four proxy parameters - sea surface temperature (SST), mixed layer depth, chlorophyll a concentration, and sea surface salinity (SSS) - are used during the training phase to enable the network to resolve the nonlinear relationships between the pCO2sea distribution and biogeochemistry of the basin. The observed pCO2sea data were obtained from an extensive dataset generated by the volunteer observation ship program operated by the National Institute for Environmental Studies (NIES). The reconstructed pCO2sea values agreed well with the pCO2sea measurements, with the root-mean-square error ranging from 17.6 μatm (for the NIES dataset used in the SOM) to 20.2 μatm (for independent dataset). We confirmed that the pCO2sea estimates could be improved by including SSS as one of the training parameters and by taking into account secular increases of pCO2sea that have tracked increases in atmospheric CO2. Estimated pCO2sea values accurately reproduced pCO2sea data at several time series locations in the North Pacific. The distributions of pCO2sea revealed by 7 yr averaged monthly pCO2sea maps were similar to Lamont-Doherty Earth Observatory pCO2sea climatology, allowing, however, for a more detailed analysis of biogeochemical conditions. The distributions of pCO2sea anomalies over the North Pacific during the winter clearly showed regional contrasts between El Niño and La Niña years related to changes of SST and vertical mixing.

Estimation of Surface Seawater Fugacity of Carbon Dioxide Using Satellite Data and Machine Learning

NASA Astrophysics Data System (ADS)

Jang, E.; Im, J.; Park, G.; Park, Y.

2016-12-01

The ocean controls the climate of Earth by absorbing and releasing CO2 through the carbon cycle. The amount of CO2 in the ocean has increased since the industrial revolution. High CO2 concentration in the ocean has a negative influence to marine organisms and reduces the ability of absorbing CO2 in the ocean. This study estimated surface seawater fugacity of CO2 (fCO2) in the East Sea of Korea using Geostationary Ocean Color Imager (GOCI) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data, and Hybrid Coordinate Ocean Model (HYCOM) reanalysis data. GOCI is the world first geostationary ocean color observation satellite sensor, and it provides 8 images with 8 bands hourly per day from 9 am to 4 pm at 500m resolution. Two machine learning approaches (i.e., random forest and support vector regression) were used to model fCO2 in this study. While most of the existing studies used multiple linear regression to estimate the pressure of CO2 in the ocean, machine learning may handle more complex relationship between surface seawater fCO2 and ocean parameters in a dynamic spatiotemporal environment. Five ocean related parameters, colored dissolved organic matter (CDOM), chlorophyll-a (chla), sea surface temperature (SST), sea surface salinity (SSS), and mixed layer depth (MLD), were used as input variables. This study examined two schemes, one with GOCI-derived products and the other with MODIS-derived ones. Results show that random forest performed better than support vector regression regardless of satellite data used. The accuracy of GOCI-based estimation was higher than MODIS-based one, possibly thanks to the better spatiotemporal resolution of GOCI data. MLD was identified the most contributing parameter in estimating surface seawater fCO2 among the five ocean related parameters, which might be related with an active deep convection in the East Sea. The surface seawater fCO2 in summer was higher in general with some spatial variation than the other seasons because of higher SST.

Calculations of the heights, periods, profile parameters, and energy spectra of wind waves

NASA Technical Reports Server (NTRS)

Korneva, L. A.

1975-01-01

Sea wave behavior calculations require the precalculation of wave elements as well as consideration of the spectral functions of ocean wave formation. The spectrum of the random wave process is largely determined by the distribution of energy in the actual wind waves observed on the surface of the sea as expressed in statistical and spectral characteristics of the sea swell.

Contents of the NASA ocean data system archive, version 11-90

NASA Technical Reports Server (NTRS)

Smith, Elizabeth A. (Editor); Lassanyi, Ruby A. (Editor)

1990-01-01

The National Aeronautics and Space Administration (NASA) Ocean Data System (NODS) archive at the Jet Propulsion Laboratory (JPL) includes satellite data sets for the ocean sciences and global-change research to facilitate multidisciplinary use of satellite ocean data. Parameters include sea-surface height, surface-wind vector, sea-surface temperature, atmospheric liquid water, and surface pigment concentration. NODS will become the Data Archive and Distribution Service of the JPL Distributed Active Archive Center for the Earth Observing System Data and Information System (EOSDIS) and will be the United States distribution site for Ocean Topography Experiment (TOPEX)/POSEIDON data and metadata.

Data catalog for JPL Physical Oceanography Distributed Active Archive Center (PO.DAAC)

NASA Technical Reports Server (NTRS)

Digby, Susan

1995-01-01

The Physical Oceanography Distributed Active Archive Center (PO.DAAC) archive at the Jet Propulsion Laboratory contains satellite data sets and ancillary in-situ data for the ocean sciences and global-change research to facilitate multidisciplinary use of satellite ocean data. Geophysical parameters available from the archive include sea-surface height, surface-wind vector, surface-wind speed, surface-wind stress vector, sea-surface temperature, atmospheric liquid water, integrated water vapor, phytoplankton pigment concentration, heat flux, and in-situ data. PO.DAAC is an element of the Earth Observing System Data and Information System and is the United States distribution site for TOPEX/POSEIDON data and metadata.

JPL Physical Oceanography Distributed Active Archive Center (PO.DAAC) data availability, version 1-94

NASA Technical Reports Server (NTRS)

1994-01-01

The Physical Oceanography Distributed Active Archive Center (PO.DAAC) archive at the Jet Propulsion Laboratory (JPL) includes satellite data sets for the ocean sciences and global-change research to facilitate multidisciplinary use of satellite ocean data. Parameters include sea-surface height, surface-wind vector, sea-surface temperature, atmospheric liquid water, and integrated water vapor. The JPL PO.DAAC is an element of the Earth Observing System Data and Information System (EOSDIS) and is the United States distribution site for Ocean Topography Experiment (TOPEX)/POSEIDON data and metadata.

Oceanic influence on seasonal malaria outbreaks over Senegal and Sahel

NASA Astrophysics Data System (ADS)

Diouf, Ibrahima; Rodríguez de Fonseca, Belen; Deme, Abdoulaye; Cisse Cisse, Moustapha; Ndione Ndione, Jaques-Andre; Gaye, Amadou T.; Suarez, Roberto

2015-04-01

Beyond assessment and analysis of observed and simulated malaria parameters, this study is furthermore undertaken in the framework of predictability of malaria outbreaks in Senegal and remote regions in Sahel, which are found to take place two months after the rainy season. The predictors are the sea surface temperature anomalous patterns at different ocean basins mainly over the Pacific and Atlantic as they are related to changes in air temperature, humidity, rainfall and wind. A relationship between El Niño and anomalous malaria parameters is found. The malaria parameters are calculated with the Liverpool Malaria Model (LMM) using meteorological datasets from different reanalysis products. A hindcast of these parameters is performed using the Sea Surface temperature based Statistical Seasonal ForeCAST (S4CAST) model developed at UCM in order to predict malaria parameters some months in advance. The results of this work will be useful for decision makers to better access to climate forecasts and application on malaria transmission risk.

Analysis of the surface heat balance over the world ocean

NASA Technical Reports Server (NTRS)

Esbenson, S. K.

1981-01-01

The net surface heat fluxes over the global ocean for all calendar months were evaluated. To obtain a formula in the form Qs = Q2(T*A - Ts), where Qs is the net surface heat flux, Ts is the sea surface temperature, T*A is the apparent atmospheric equilibrium temperature, and Q2 is the proportionality constant. Here T*A and Q2, derived from the original heat flux formulas, are functions of the surface meteorological parameters (e.g., surface wind speed, air temperature, dew point, etc.) and the surface radiation parameters. This formulation of the net surface heat flux together with climatological atmospheric parameters provides a realistic and computationally efficient upper boundary condition for oceanic climate modeling.

Observing the seasonal cycle of the upper ocean in the Ross Sea, Antarctica, with autonomous profiling floats

NASA Astrophysics Data System (ADS)

Porter, D. F.; Springer, S. R.; Padman, L.; Fricker, H. A.; Bell, R. E.

2017-12-01

The upper layers of the Southern Ocean where it meets the Antarctic ice sheet undergoes a large seasonal cycle controlled by surface radiation and by freshwater fluxes, both of which are strongly influenced by sea ice. In regions where seasonal sea ice and icebergs limit use of ice-tethered profilers and conventional moorings, autonomous profiling floats can sample the upper ocean. The deployment of seven Apex floats (by sea) and six ALAMO floats (by air) provides unique upper ocean hydrographic data in the Ross Sea close to the Ross Ice Shelf front. A novel choice of mission parameters - setting parking depth deeper than the seabed - limits their drift, allowing us to deploy the floats close to the ice shelf front, while sea ice avoidance algorithms allow the floats to to sample through winter under sea ice. Hydrographic profiles show the detailed development of the seasonal mixed layer close to the Ross front, and interannual variability of the seasonal mixed layer and deeper water masses on the central Ross Sea continental shelf. After the sea ice breakup in spring, a warm and fresh surface mixed layer develops, further warming and deepening throughout the summer. The mixed layer deepens, with maximum temperatures exceeding 0ºC in mid-February. By March, the surface energy budget becomes negative and sea ice begins to form, creating a cold, saline and dense surface layer. Once these processes overcome the stable summer stratification, convection erodes the surface mixed layer, mixing some heat downwards to deeper layers. There is considerable interannual variability in the evolution and strength of the surface mixed layer: summers with shorter ice-free periods result in a cooler and shallower surface mixed layer, which accumulates less heat than the summers with longer ice-free periods. Early ice breakup occurred in all floats in 2016/17 summer, enhancing the absorbed solar flux leading to a warmer surface mixed layer. Together, these unique measurements from autonomous profilers provide insight into the hydrographic state of the Ross Sea at the start of the spring period of sea-ice breakup, and how ocean mixing and sea ice interact to initiate the summer open-water season.

Estimation of sea level variations with GPS/GLONASS-reflectometry technique

NASA Astrophysics Data System (ADS)

Padokhin, A. M.; Kurbatov, G. A.; Andreeva, E. S.; Nesterov, I. A.; Nazarenko, M. O.; Berbeneva, N. A.; Karlysheva, A. V.

2017-11-01

In the present paper we study GNSS - reflectometry methods for estimation of sea level variations using a single GNSSreceiver, which are based on the multipath propagation effects caused by the reflection of navigational signals from the sea surface. Such multipath propagation results in the appearance of the interference pattern in the Signal-to-Noise Ratio (SNR) of GNSS signals at small satellite elevation angles, which parameters are determined by the wavelength of the navigational signal and height of the antenna phase center above the reflecting sea surface. In current work we used GPS and GLONASS signals and measurements at two working frequencies of both systems to study sea level variations which almost doubles the amount of observations compared to GPS-only tide gauge. For UNAVCO sc02 station and collocated Friday Harbor NOAA tide gauge we show good agreement between GNSS-reflectometry and traditional mareograph sea level data.

On the classification of mixed floating pollutants on the Yellow Sea of China by using a quad-polarized SAR image

NASA Astrophysics Data System (ADS)

Wang, Xiaochen; Shao, Yun; Tian, Wei; Li, Kun

2018-06-01

This study explored different methodologies using a C-band RADARSAT-2 quad-polarized Synthetic Aperture Radar (SAR) image located over China's Yellow Sea to investigate polarization decomposition parameters for identifying mixed floating pollutants from a complex ocean background. It was found that solitary polarization decomposition did not meet the demand for detecting and classifying multiple floating pollutants, even after applying a polarized SAR image. Furthermore, considering that Yamaguchi decomposition is sensitive to vegetation and the algal variety Enteromorpha prolifera, while H/A/alpha decomposition is sensitive to oil spills, a combination of parameters which was deduced from these two decompositions was proposed for marine environmental monitoring of mixed floating sea surface pollutants. A combination of volume scattering, surface scattering, and scattering entropy was the best indicator for classifying mixed floating pollutants from a complex ocean background. The Kappa coefficients for Enteromorpha prolifera and oil spills were 0.7514 and 0.8470, respectively, evidence that the composite polarized parameters based on quad-polarized SAR imagery proposed in this research is an effective monitoring method for complex marine pollution.

High resolution sea ice modeling for the region of Baffin Bay and the Labrador Sea

NASA Astrophysics Data System (ADS)

Zakharov, I.; Prasad, S.; McGuire, P.

2016-12-01

A multi-category numerical sea ice model (CICE) with a data assimilation module was implemented to derive sea ice parameters in the region of Baffin Bay and the Labrador Sea with resolution higher than 10 km. The model derived ice parameters include concentration, ridge keel measurement, thickness and freeboard. The module for assimilation of ice concentration uses data from the Advance Microwave Scanning Radiometer (AMSR-E) and OSI SAF data. The sea surface temperature (SST) data from AMSRE-AVHRR and Operational SST and Sea Ice Analysis (OSTIA) system were used to correct the SST computed by a mixed layer slab ocean model that is used to determine the growth and melt of sea ice. The ice thickness parameter from the model was compared with the measurements from Soil Moisture Ocean Salinity - Microwave Imaging Radiometer using Aperture Synthesis (SMOS-MIRAS). The freeboard measures where compared with the Cryosat-2 measurements. A spatial root mean square error computed for freeboard measures was found to be within the uncertainty limits of the observation. The model was also used to estimate the correlation parameter between the ridge and the ridge keel measurements in the region of Makkovik Bank. Also, the level ice draft estimated from the model was in good agreement with the ice draft derived from the upward looking sonar (ULS) instrument deployed in the Makkovik bank. The model corrected with ice concentration and SST from remote sensing data demonstrated significant improvements in accuracy of the estimated ice parameters. The model can be used for operational forecast and climate research.

Trace Elements in the Sea Surface Microlayer: Results from a Two Year Study in the Florida Keys

NASA Astrophysics Data System (ADS)

Ebling, A. M.; Westrich, J. R.; Lipp, E. K.; Mellett, T.; Buck, K. N.; Landing, W. M.

2016-02-01

Natural and anthropogenic aerosols are a significant source of trace elements to oligotrophic ocean surface waters, where they provide episodic pulses of limiting micronutrients for the microbial community. Opportunistic bacteria have been shown to experience rapid growth during deposition events. However, little is known about the fate of trace elements at the air-sea interface, i.e. the sea surface microlayer. It has been hypothesized that dust particles would be retained in the sea surface microlayer long enough to undergo chemical and physical changes that would affect the bioavailability of trace elements. In this study, aerosols, sea surface microlayer, and underlying water column samples were collected in the Florida Keys in July 2014 and May 2015 at various locations and analyzed for a suite of dissolved and particulate trace elements. Sea surface microlayer samples ( 50 μm) were collected using a cylinder of ultra-pure quartz glass; a novel adaptation of the glass plate technique. Sampling sites ranged from a more pristine environment approximately ten kilometers offshore to a more anthropogenic environment within a shallow bay a few hundred meters offshore. While it was clear from the results that dust deposition events played a large role in the chemical composition of the sea surface microlayer (elevated concentrations in dissolved and particulate trace elements associated with dust deposition), the location where the samples were collected also had a large impact on the sea surface microlayer as well as the underlying water column. The results were compared with other parameters analyzed such as Vibrio cultures as well as iron speciation, providing an important step towards our goal of understanding of the fate of trace elements in the sea surface microlayer as well as the specific effects of aeolian dust deposition on heterotrophic microbes in the upper ocean.

Glistening-region model for multipath studies

NASA Astrophysics Data System (ADS)

Groves, Gordon W.; Chow, Winston C.

1998-07-01

The goal is to achieve a model of radar sea reflection with improved fidelity that is amenable to practical implementation. The geometry of reflection from a wavy surface is formulated. The sea surface is divided into two components: the smooth `chop' consisting of the longer wavelengths, and the `roughness' of the short wavelengths. Ordinary geometric reflection from the chop surface is broadened by the roughness. This same representation serves both for forward scatter and backscatter (sea clutter). The `Road-to-Happiness' approximation, in which the mean sea surface is assumed cylindrical, simplifies the reflection geometry for low-elevation targets. The effect of surface roughness is assumed to make the sea reflection coefficient depending on the `Deviation Angle' between the specular and the scattering directions. The `specular' direction is that into which energy would be reflected by a perfectly smooth facet. Assuming that the ocean waves are linear and random allows use of Gaussian statistics, greatly simplifying the formulation by allowing representation of the sea chop by three parameters. An approximation of `low waves' and retention of the sea-chop slope components only through second order provides further simplification. The simplifying assumptions make it possible to take the predicted 2D ocean wave spectrum into account in the calculation of sea-surface radar reflectivity, to provide algorithms for support of an operational system for dealing with target tracking in the presence of multipath. The product will be of use in simulated studies to evaluate different trade-offs in alternative tracking schemes, and will form the basis of a tactical system for ship defense against low flyers.

TRICAINE METHANESULFONATE (MS-222) SEDATION AND ANESTHESIA IN THE PURPLE-SPINED SEA URCHIN (ARBACIA PUNCTULATA).

PubMed

Applegate, Jeffrey R; Dombrowski, Daniel S; Christian, Larry Shane; Bayer, Meredith P; Harms, Craig A; Lewbart, Gregory A

2016-12-01

The purple-spined sea urchin ( Arbacia punctulata ) is commonly found in shallow waters of the western Atlantic Ocean from the New England area of the United States to the Caribbean. Sea urchins play a major role in ocean ecology, echinoculture, and biomedical research. Additionally, sea urchins are commonly displayed in public aquaria. Baseline parameters were developed in unanesthetized urchins for righting reflex (time to regain oral recumbency) and spine response time to tactile stimulus. Tricaine methanesulfonate (MS-222) was used to sedate and anesthetize purple-spined sea urchins and assess sedation and anesthetic parameters, including adhesion to and release from a vertical surface, times to loss of response to tactile stimulus and recovery of righting reflex, and qualitative observations of induction of spawning and position of spines and pseudopodia. Sedation and anesthetic parameters were evaluated in 11 individuals in three circumstances: unaltered aquarium water for baseline behaviors, 0.4 g/L MS-222, and 0.8 g/L MS-222. Induction was defined as the release from a vertical surface with the loss of righting reflex, sedation as loss of righting reflex with retained tactile spine response, anesthesia as loss of righting reflex and loss of tactile spine response, and recovery as voluntary return to oral recumbency. MS-222 proved to be an effective sedative and anesthetic for the purple-spined sea urchin at 0.4 and 0.8 g/L, respectively. Sodium bicarbonate used to buffer MS-222 had no measurable sedative effects when used alone. Anesthesia was quickly reversed with transfer of each individual to anesthesia-free seawater, and no anesthetic-related mortality occurred. The parameters assessed in this study provide a baseline for sea urchin anesthesia and may provide helpful comparisons to similar species and populations that are in need of anesthesia for surgical procedures or research.

Satellite altimetry in sea ice regions - detecting open water for estimating sea surface heights

NASA Astrophysics Data System (ADS)

Müller, Felix L.; Dettmering, Denise; Bosch, Wolfgang

2017-04-01

The Greenland Sea and the Farm Strait are transporting sea ice from the central Arctic ocean southwards. They are covered by a dynamic changing sea ice layer with significant influences on the Earth climate system. Between the sea ice there exist various sized open water areas known as leads, straight lined open water areas, and polynyas exhibiting a circular shape. Identifying these leads by satellite altimetry enables the extraction of sea surface height information. Analyzing the radar echoes, also called waveforms, provides information on the surface backscatter characteristics. For example waveforms reflected by calm water have a very narrow and single-peaked shape. Waveforms reflected by sea ice show more variability due to diffuse scattering. Here we analyze altimeter waveforms from different conventional pulse-limited satellite altimeters to separate open water and sea ice waveforms. An unsupervised classification approach employing partitional clustering algorithms such as K-medoids and memory-based classification methods such as K-nearest neighbor is used. The classification is based on six parameters derived from the waveform's shape, for example the maximum power or the peak's width. The open-water detection is quantitatively compared to SAR images processed while accounting for sea ice motion. The classification results are used to derive information about the temporal evolution of sea ice extent and sea surface heights. They allow to provide evidence on climate change relevant influences as for example Arctic sea level rise due to enhanced melting rates of Greenland's glaciers and an increasing fresh water influx into the Arctic ocean. Additionally, the sea ice cover extent analyzed over a long-time period provides an important indicator for a globally changing climate system.

Goddard Laboratory for Atmospheric Sciences physical retrieval system for remote determination of weather and climate parameter from HIRS2 and MSU observations

NASA Technical Reports Server (NTRS)

Susskind, J.

1984-01-01

At the Goddard Laboratory for Atmospheric Sciences (GLAS) a physically based satellite temperature sounding retrieval system, involving the simultaneous analysis of HIRS2 and MSU sounding data, was developed for determining atmospheric and surface conditions which are consistent with the observed radiances. In addition to determining accurate atmospheric temperature profiles even in the presence of cloud contamination, the system provides global estimates of day and night sea or land surface temperatures, snow and ice cover, and parameters related to cloud cover. Details of the system are described elsewhere. A brief overview of the system is presented, as well as recent improvements and previously unpublished results, relating to the sea-surface intercomparison workshop, the diurnal variation of ground temperatures, and forecast impact tests.

Innovative eco-friendly bio- solvent for combating sea surface and sedimented oil pollution

NASA Astrophysics Data System (ADS)

Theodorou, Paraskevas

2017-04-01

The combating of oil spill at sea surface by chemical dispersants accelerates the evaporation and disperse the oil into the water column, where it is broken down by natural processes and/or is sedimented at the sea bottom, especially at near coastal shallow areas, ports and marinas. The usual methodology for cleaning the sedimented oil from the sea bottom is mainly carried out via excavation and dumping of the polluted sediment into deeper sea areas, where the contamination is transferred from one area to another. The eco-friendly bio-solvent MSL Aqua 250 is an innovative new solution based mainly on natural constituents. The action mechanism and the effectiveness of this eco-friendly solvent is based on the high surface tension process. Organic compounds, including hydrocarbons upon coming in contact with MSL Aqua 250 solvent generate a significant surface tension reaction, which is able to alter the organic compounds to liquid form and then to drastically evaporate it. The use of MSL Aqua 250 solvent, both at sea surface and at the bottom, has the following advantages compared to the dispersants: • Efficient solution without transferring the pollution from sea surface to the water column and to the bottom or disturbing the Aquatic Eco System. • Non-Toxic. • Environmentally friendly with a restoration of marine life in the Eco System. • Cost effective. The MSL Aqua 250 solvent has been tested in cooperation with the Cyprus Department of Fisheries and Marine Research and the Technological University of Cyprus and used during the years 2015 and 2016 in marinas and fishing shelters in Cyprus faced oil pollution, with high concentration in the sea water and at the sea bottom of chemical parameters (BOD5, COD, FOG, TKN, TP, TPH), with excellent results.

An evaluation of the use of remotely sensed parameters for prediction of incidence and risk associated with Vibrio parahaemolyticus in Gulf Coast oysters (Crassostrea virginica).

PubMed

Phillips, A M B; Depaola, A; Bowers, J; Ladner, S; Grimes, D J

2007-04-01

The U.S. Food and Drug Administration recently published a Vibrio parahaemolyticus risk assessment for consumption of raw oysters that predicts V. parahaemolyticus densities at harvest based on water temperature. We retrospectively compared archived remotely sensed measurements (sea surface temperature, chlorophyll, and turbidity) with previously published data from an environmental study of V. parahaemolyticus in Alabama oysters to assess the utility of the former data for predicting V. parahaemolyticus densities in oysters. Remotely sensed sea surface temperature correlated well with previous in situ measurements (R(2) = 0.86) of bottom water temperature, supporting the notion that remotely sensed sea surface temperature data are a sufficiently accurate substitute for direct measurement. Turbidity and chlorophyll levels were not determined in the previous study, but in comparison with the V. parahaemolyticus data, remotely sensed values for these parameters may explain some of the variation in V. parahaemolyticus levels. More accurate determination of these effects and the temporal and spatial variability of these parameters may further improve the accuracy of prediction models. To illustrate the utility of remotely sensed data as a basis for risk management, predictions based on the U.S. Food and Drug Administration V. parahaemolyticus risk assessment model were integrated with remotely sensed sea surface temperature data to display graphically variations in V. parahaemolyticus density in oysters associated with spatial variations in water temperature. We believe images such as these could be posted in near real time, and that the availability of such information in a user-friendly format could be the basis for timely and informed risk management decisions.

Sea wind parameters retrieval using Y-configured Doppler navigation system data. Performance and accuracy

NASA Astrophysics Data System (ADS)

Khachaturian, A. B.; Nekrasov, A. V.; Bogachev, M. I.

2018-05-01

The authors report the results of the computer simulations of the performance and accuracy of the sea wind speed and direction retrieval. The analyzed measurements over the sea surface are made by the airborne microwave Doppler navigation system (DNS) with three Y-configured beams operated as a scatterometer enhancing its functionality. Single- and double-stage wind measurement procedures are proposed and recommendations for their implementation are described.

FIRE_AX_SOF_SUR_MET

Atmospheric Science Data Center

2015-11-25

... Buoy Instrument:  Barometer Sonic Anemometer Thermistor Spatial Coverage:  (34.60, ... Earthdata Search Parameters:  Dry Bulb Temperature Pressure Sea Surface Temperature Wet Bulb Temperature ...

A Genesis Potential Index for Tropical Cyclone by Using Oceanic Parameters

NASA Astrophysics Data System (ADS)

Zhou, L.; Zhang, M.; Chen, D.; Wang, C.

2015-12-01

This study attempts to create a tropical cyclone (TC) genesis potential index (GPI) by considering oceanic parameters and necessary atmospheric parameters at the sea surface. Based on the general understanding of oceanic impacts on the TC genesis, many candidate factors are evaluated and discriminated, resulting in a new GPI index called GPIocean. GPIocean includes (1) the absolute vorticity at 1000 hPa, (2) the net sea surface longwave radiation, (3) the mean ocean temperature in the upper mixed layer, and (4) the depth of the 26°C isotherm. GPIocean is comparable to the existing GPIs in representing the TC genesis over the western North Pacific on climatological, interannual, and seasonal time scales. In the context of climate change, this new index is expected to be useful for evaluating the oceanic influences on the TC genesis, using ocean reanalysis products and/or climate model outputs.

A summary of selected early results from the ERTS-1 menhaden experiment

NASA Technical Reports Server (NTRS)

Stevenson, W. H. (Principal Investigator); Kemmerer, A. J.; Benigno, J. A.; Reese, G. B.; Minkler, F. C.

1973-01-01

The author has identified the following significant results. Imagery from ERTS-1 satellite was used in conjunction with aerial photographically-sensed menhaden distribution information, sea truth oceanographic measurements, and commercial fishing information from a 8685 square kilometer study area in the north-central portion of the Gulf of Mexico to demonstrate relationships between selected oceanographic parameters and menhaden distribution, ERTS-1 imagery and menhaden distribution, and ERTS-1 imagery and oceanographic parameters. ERTS-1, MSS band 5 imagery density levels correlated with photographically detected menhaden distribution patterns and could be explained based on sea truth Secchi disc transparency and water depth measurements. These two parameters, together with surface salinity, Forel-Ule color, and chlorophyll-a also were found to correlate significantly with menhaden distribution. Eight empirical models were developed which provided menhaden distribution predictions for the study area on combinations of Secchi disc transparency, water depth, surface salinity, and Forel-Ule color measurements.

Attitude angle effects on Nimbus-7 Scanning Multichannel Microwave Radiometer radiances and geophysical parameter retrievals

NASA Technical Reports Server (NTRS)

Macmillan, Daniel S.; Han, Daesoo

1989-01-01

The attitude of the Nimbus-7 spacecraft has varied significantly over its lifetime. A summary of the orbital and long-term behavior of the attitude angles and the effects of attitude variations on Scanning Multichannel Microwave Radiometer (SMMR) brightness temperatures is presented. One of the principal effects of these variations is to change the incident angle at which the SMMR views the Earth's surface. The brightness temperatures depend upon the incident angle sensitivities of both the ocean surface emissivity and the atmospheric path length. Ocean surface emissivity is quite sensitive to incident angle variation near the SMMR incident angle, which is about 50 degrees. This sensitivity was estimated theoretically for a smooth ocean surface and no atmosphere. A 1-degree increase in the angle of incidence produces a 2.9 C increase in the retrieved sea surface temperature and a 5.7 m/sec decrease in retrieved sea surface wind speed. An incident angle correction is applied to the SMMR radiances before using them in the geophysical parameter retrieval algorithms. The corrected retrieval data is compared with data obtained without applying the correction.

Evaluation and source attribution of freshwater contributions to Kinvarra Bay, Ireland, using (222)Rn, EC and stable isotopes as natural indicators.

PubMed

Schubert, Michael; Knoeller, Kay; Rocha, Carlos; Einsiedl, Florian

2015-03-01

Freshwater discharge into the coastal sea is of general interest for two reasons: (i) It acts as vehicle for the transport of contaminants or nutrients into the ocean, and (ii) it indicates the loss of significant volumes of freshwater that might be needed for irrigation or drinking water supply. Due to the large-scale and long-term nature of the related hydrological processes, locating and quantitatively assessing freshwater discharge into the sea require naturally occurring tracers that allow fast, inexpensive and straightforward detection. In several studies, the standard water parameters electrical conductivity (EC) and pH have proven their suitability in this regard. However, while distribution patterns of EC and pH in the coastal sea indicate freshwater discharge in general, a separation between discharging surface water and submarine groundwater discharge (SGD) is not possible with these alone. The naturally occurring radionuclide radon-222 has been shown to be useful in the quantification of SGD and its distinction from surface runoff. This study aimed to evaluate and compare the informative value of the three parameters-EC, pH and radon concentration-in detecting and quantifying SGD by carrying out a case study in a bay located in western Ireland. The results reveal that radon activity is the most sensitive parameter for detecting SGD. However, only the combined evaluation of radon, EC and pH allows a quantitative allocation of groundwater and surface water contributions to the overall freshwater discharge into the sea. This conclusion is independently supported by stable isotope data measured on selected samples.

Short pulse radar used to measure sea surface wind speed and SWH. [Significant Wave Height

NASA Technical Reports Server (NTRS)

Hammond, D. L.; Mennella, R. A.; Walsh, E. J.

1977-01-01

A joint airborne measurement program is being pursued by NRL and NASA Wallops Flight Center to determine the extent to which wind speed and sea surface significant wave height (SWH) can be measured quantitatively and remotely with a short pulse (2 ns), wide-beam (60 deg), nadir-looking 3-cm radar. The concept involves relative power measurements only and does not need a scanning antenna, Doppler filters, or absolute power calibration. The slopes of the leading and trailing edges of the averaged received power for the pulse limited altimeter are used to infer SWH and surface wind speed. The interpretation is based on theoretical models of the effects of SWH on the leading edge shape and rms sea-surface slope on the trailing-edge shape. The models include the radar system parameters of antenna beam width and pulsewidth.

Investigation of the spectral reflectance and bidirectional reflectance distribution function of sea foam layer by the Monte Carlo method.

PubMed

Ma, L X; Wang, F Q; Wang, C A; Wang, C C; Tan, J Y

2015-11-20

Spectral properties of sea foam greatly affect ocean color remote sensing and aerosol optical thickness retrieval from satellite observation. This paper presents a combined Mie theory and Monte Carlo method to investigate visible and near-infrared spectral reflectance and bidirectional reflectance distribution function (BRDF) of sea foam layers. A three-layer model of the sea foam is developed in which each layer is composed of large air bubbles coated with pure water. A pseudo-continuous model and Mie theory for coated spheres is used to determine the effective radiative properties of sea foam. The one-dimensional Cox-Munk surface roughness model is used to calculate the slope density functions of the wind-blown ocean surface. A Monte Carlo method is used to solve the radiative transfer equation. Effects of foam layer thickness, bubble size, wind speed, solar zenith angle, and wavelength on the spectral reflectance and BRDF are investigated. Comparisons between previous theoretical results and experimental data demonstrate the feasibility of our proposed method. Sea foam can significantly increase the spectral reflectance and BRDF of the sea surface. The absorption coefficient of seawater near the surface is not the only parameter that influences the spectral reflectance. Meanwhile, the effects of bubble size, foam layer thickness, and solar zenith angle also cannot be obviously neglected.

Earth Survey Applications Division. [a bibliography

NASA Technical Reports Server (NTRS)

Carpenter, L. (Editor)

1981-01-01

Accomplishments of research and data analysis conducted to study physical parameters and processes inside the Earth and on the Earth's surface, to define techniques and systems for remotely sensing the processes and measuring the parameters of scientific and applications interest, and the transfer of promising operational applications techniques to the user community of Earth resources monitors, managers, and decision makers are described. Research areas covered include: geobotany, magnetic field modeling, crustal studies, crustal dynamics, sea surface topography, land resources, remote sensing of vegetation and soils, and hydrological sciences. Major accomplishments include: production of global maps of magnetic anomalies using Magsat data; computation of the global mean sea surface using GEOS-3 and Seasat altimetry data; delineation of the effects of topography on the interpretation of remotely-sensed data; application of snowmelt runoff models to water resources management; and mapping of snow depth over wheat growing areas using Nimbus microwave data.

Functional Metagenomic Investigations of Microbial Communities in a Shallow-Sea Hydrothermal System

PubMed Central

Tang, Kai; Liu, Keshao; Jiao, Nianzhi; Zhang, Yao; Chen, Chen-Tung Arthur

2013-01-01

Little is known about the functional capability of microbial communities in shallow-sea hydrothermal systems (water depth of <200 m). This study analyzed two high-throughput pyrosequencing metagenomic datasets from the vent and the surface water in the shallow-sea hydrothermal system offshore NE Taiwan. This system exhibited distinct geochemical parameters. Metagenomic data revealed that the vent and the surface water were predominated by Epsilonproteobacteria (Nautiliales-like organisms) and Gammaproteobacteria ( Thiomicrospira -like organisms), respectively. A significant difference in microbial carbon fixation and sulfur metabolism was found between the vent and the surface water. The chemoautotrophic microorganisms in the vent and in the surface water might possess the reverse tricarboxylic acid cycle and the Calvin−Bassham−Benson cycle for carbon fixation in response to carbon dioxide highly enriched in the environment, which is possibly fueled by geochemical energy with sulfur and hydrogen. Comparative analyses of metagenomes showed that the shallow-sea metagenomes contained some genes similar to those present in other extreme environments. This study may serve as a basis for deeply understanding the genetic network and functional capability of the microbial members of shallow-sea hydrothermal systems. PMID:23940820

Radial orbit error reduction and sea surface topography determination using satellite altimetry

NASA Technical Reports Server (NTRS)

Engelis, Theodossios

1987-01-01

A method is presented in satellite altimetry that attempts to simultaneously determine the geoid and sea surface topography with minimum wavelengths of about 500 km and to reduce the radial orbit error caused by geopotential errors. The modeling of the radial orbit error is made using the linearized Lagrangian perturbation theory. Secular and second order effects are also included. After a rather extensive validation of the linearized equations, alternative expressions of the radial orbit error are derived. Numerical estimates for the radial orbit error and geoid undulation error are computed using the differences of two geopotential models as potential coefficient errors, for a SEASAT orbit. To provide statistical estimates of the radial distances and the geoid, a covariance propagation is made based on the full geopotential covariance. Accuracy estimates for the SEASAT orbits are given which agree quite well with already published results. Observation equations are develped using sea surface heights and crossover discrepancies as observables. A minimum variance solution with prior information provides estimates of parameters representing the sea surface topography and corrections to the gravity field that is used for the orbit generation. The simulation results show that the method can be used to effectively reduce the radial orbit error and recover the sea surface topography.

Simple rules govern the patterns of Arctic sea ice melt ponds

NASA Astrophysics Data System (ADS)

Popovic, P.; Cael, B. B.; Abbot, D. S.; Silber, M.

2017-12-01

Climate change, amplified in the far north, has led to a rapid sea ice decline in recent years. Melt ponds that form on the surface of Arctic sea ice in the summer significantly lower the ice albedo, thereby accelerating ice melt. Pond geometry controls the details of this crucial feedback. However, currently it is unclear how to model this intricate geometry. Here we show that an extremely simple model of voids surrounding randomly sized and placed overlapping circles reproduces the essential features of pond patterns. The model has only two parameters, circle scale and the fraction of the surface covered by voids, and we choose them by comparing the model to pond images. Using these parameters the void model robustly reproduces all of the examined pond features such as the ponds' area-perimeter relationship and the area-abundance relationship over nearly 7 orders of magnitude. By analyzing airborne photographs of sea ice, we also find that the typical pond scale is surprisingly constant across different years, regions, and ice types. These results demonstrate that the geometric and abundance patterns of Arctic melt ponds can be simply described, and can guide future models of Arctic melt ponds to improve predictions of how sea ice will respond to Arctic warming.

Polarimetric Remote Sensing of Geophysical Medium Structures

NASA Technical Reports Server (NTRS)

Nghiem, S. V.; Yueh, S. H.; Kwok, R.; Nguyen, D. T.

1993-01-01

Polarimetric remote sensing of structures in geophysical media is studied in this paper based on their symmetry properties. Orientations of spheroidal scatterers described by spherical, uniform, planophile, plagiothile, erectophile, and extremophile distributions are considered to derive their polarimetric backscattering characteristics. These distributions can be identified from the observed scattering coefficients by comparison with theoretical symmetry calculations. A new parameter is defined to study scattering structures in geophysical media. Experimental observations from polarimetric data acquired by the Jet Propulsion Laboratory airborne synthetic aperture radar over forests, sea ice, and sea surface are presented to illustrate the use of symmetry properties. For forests, the coniferous forest in Mount Shasta area and mixed forests neir Presque Isle show evidence of the centrical symmetry at C band. In sea ice from the Beaufort Sea, multiyear sea ice has a cross-polarized ratio e close to e(sub 0), calculated from symmetry, due to the randomness in the scattering structure. For first-year sea ice, e is much smaller than e(sub 0) as a result of preferential alignment of the columnar structure of the ice. From polarimetric data of a sea surface in the Bering sea, it is observed that e and e(sub 0) are increasing with incident angle and e is greater than e(sub 0) at L band because of the directional feature of sea surface waves. Use of symmetry properties of geophysical media for polarimetric radar calibration is also suggested.

Relationships between carapace sizes and plasma major and trace element status in captive hawksbill sea turtles (Eretmochelys imbricata).

PubMed

Suzuki, Kazuyuki; Noda, Jun; Yanagisawa, Makio; Kawazu, Isao; Sera, Kouichiro; Fukui, Daisuke; Asakawa, Mitsuhiko; Yokota, Hiroshi

2012-12-01

The aim of this study was to evaluate the relationships between carapace parameters as indicators of age and plasma elements in 25 captive hawksbill sea turtles. Particle-induced X-ray emission allowed detection of 23 trace and major elements. There were significant but weak correlations between the virtual carapace surface area and plasma bromide (r = -0.552, P<0.01), phosphorus (r = 0.547, P<0.01), lead (r =-0.434, P<0.05) and strontium (r = 0.599, P<0.01), while there were no significant correlations with other elements. These results suggest that major and trace plasma elements in captive sea turtles show almost no variation with carapace parameters, suggesting that the increase in plasma elements seen in wild sea turtles might be the result of marine pollution.

An improved empirical dynamic control system model of global mean sea level rise and surface temperature change

NASA Astrophysics Data System (ADS)

Wu, Qing; Luu, Quang-Hung; Tkalich, Pavel; Chen, Ge

2018-04-01

Having great impacts on human lives, global warming and associated sea level rise are believed to be strongly linked to anthropogenic causes. Statistical approach offers a simple and yet conceptually verifiable combination of remotely connected climate variables and indices, including sea level and surface temperature. We propose an improved statistical reconstruction model based on the empirical dynamic control system by taking into account the climate variability and deriving parameters from Monte Carlo cross-validation random experiments. For the historic data from 1880 to 2001, we yielded higher correlation results compared to those from other dynamic empirical models. The averaged root mean square errors are reduced in both reconstructed fields, namely, the global mean surface temperature (by 24-37%) and the global mean sea level (by 5-25%). Our model is also more robust as it notably diminished the unstable problem associated with varying initial values. Such results suggest that the model not only enhances significantly the global mean reconstructions of temperature and sea level but also may have a potential to improve future projections.

Relationship between RADARSAT-2 Derived Snow Thickness on Winter First Year Sea-Ice and Aerial Melt-Pond Distribution using Geostatistics and GLCM Texture

NASA Astrophysics Data System (ADS)

Ramjan, S.; Geldsetzer, T.; Yackel, J.

2016-12-01

A contemporary shift from primarily thicker, older multi-year sea ice (MYI) to thinner, smoother first-year sea ice (FYI) has been attributed to increased atmospheric and oceanic warming in the Arctic, with a steady diminishing of Arctic sea ice thickness due to a reduction of thick MYI compared to FYI. With an increase in FYI fraction, increased melting takes place during the summer months, exposing the sea ice to additional incoming solar radiation. With this change, an increase in melt pond fraction has been observed during the summer melt season. Prior research advocated that thin/thick snow leads to dominant surface flooding/snow patches during summer because of an enhanced ice-albedo feedback. For instance, thin snow cover areas form melt ponds first. Therefore, aerial measurements of melt pond fraction provide a proxy for relative snow thickness. RADARSAT-2 polarimetric SAR data can provide enhanced information about both surface scattering and volume scattering mechanisms, as well as recording the phase difference between polarizations. These polarimetric parameters can be computed that have a useful physical interpretation. The principle research focus is to establish a methodology to determine the relationship between selected geostatistics and image texture measures of pre-melt RADARSAT-2 parameters and aerially-measured melt pond fraction. Overall, the notion of this study is to develop an algorithm to estimate relative snow thickness variability in winter through an integrated approach utilizing SAR polarimetric parameters, geostatistical analysis and texture measures. Results are validated with test sets of melt pond fractions, and in situ snow thickness measurements. Preliminary findings show significant correlations with pond fraction for the standard deviation of HH and HV parameters at small incidence angles, and for the mean of the co-pol phase difference parameter at large incidence angles.

Bibliography of Soviet Laser Developments, Number 88, March - April 1987.

DTIC Science & Technology

1988-03-03

IPG. Trudy, no. 67, 1986, 123-128. 67 560. Kublashvili, G.S. ). Laser probe measurement of sea wave parameters near shore. SAKNA, vol. 125, no. 3, 1987...RZFZA, 87/4L838). 562. Lezhen, A.S.; Sviridov, S.A.; Stemkovskiy, A.I. (IOAN; SimGU). Method and device to determine rises and gradients of the sea ...podstilayushchey poverkhnosti. IOA. Novosibirsk, Nauka, 1987, 223-239. 573. Shevchenko, T.B.; Shugan, I.V. 0. Laser probing of the sea surface from aircraft

Assessing the Dynamics of Organic Aerosols over the North Atlantic Ocean

PubMed Central

Kasparian, Jérôme; Hassler, Christel; Ibelings, Bas; Berti, Nicolas; Bigorre, Sébastien; Djambazova, Violeta; Gascon-Diez, Elena; Giuliani, Grégory; Houlmann, Raphaël; Kiselev, Denis; de Laborie, Pierric; Le, Anh-Dao; Magouroux, Thibaud; Neri, Tristan; Palomino, Daniel; Pfändler, Stéfanie; Ray, Nicolas; Sousa, Gustavo; Staedler, Davide; Tettamanti, Federico; Wolf, Jean-Pierre; Beniston, Martin

2017-01-01

The influence of aerosols on climate is highly dependent on the particle size distribution, concentration, and composition. In particular, the latter influences their ability to act as cloud condensation nuclei, whereby they impact cloud coverage and precipitation. Here, we simultaneously measured the concentration of aerosols from sea spray over the North Atlantic on board the exhaust-free solar-powered vessel “PlanetSolar”, and the sea surface physico-chemical parameters. We identified organic-bearing particles based on individual particle fluorescence spectra. Organic-bearing aerosols display specific spatio-temporal distributions as compared to total aerosols. We propose an empirical parameterization of the organic-bearing particle concentration, with a dependence on water salinity and sea-surface temperature only. We also show that a very rich mixture of organic aerosols is emitted from the sea surface. Such data will certainly contribute to providing further insight into the influence of aerosols on cloud formation, and be used as input for the improved modeling of aerosols and their role in global climate processes. PMID:28361985

Analysis of X-band radar images for the detection of the reflected and diffracted waves in coastal zones

NASA Astrophysics Data System (ADS)

Ludeno, Giovanni; Natale, Antonio; Soldovieri, Francesco; Vicinanza, Diego; Serafino, Francesco

2014-05-01

The observation of nearshore waves and the knowledge of the sea state parameters can play a crucial role for the safety of harbors and ocean engineering. In the last two decades, different algorithms for the estimation of sea state parameters, surface currents and bathymetry from X-band radar data have been developed and validated [1, 2]. The retrieval of ocean wave parameters such as significant height, period, direction and wavelength of the dominant wave is based on the spectral analysis of data sequences collected by nautical X-band radars [3]. In particular, the reconstruction of the wave motion is carried out through the inversion procedure explained in [1-3], which exploits the dispersion relationship to define a band pass filter used to separate the energy associated with the ocean waves from the background noise. It is worth to note that the shape of such a band pass filter depends upon the value of both the surface currents and bathymetry; in our reconstruction algorithm these parameters are estimated through the (Normalized Scalar Product) procedure [1], which outperforms other existing methods (e.g., the Least Squares) [4]. From the reconstructed wave elevation sequences we can get the directional spectrum that provides useful information (i.e., wavelength, period, direction and amplitude) relevant to the main waves contributing to the wave motion. Of course, in coastal zones a number of diffraction and reflection phenomena can be observed, due to sea-waves impinging obstacles as jetties, breakwaters and boats. In the present paper we want to show the capability to detect reflected and diffracted sea-waves offered by the processing of X-band radar data. Further details relevant to the obtained results will be provided in the full paper and at the conference time. References [1] F. Serafino, C. Lugni, F. Soldovieri, "A novel strategy for the surface current determination from marine X-Band radar data", IEEE Geosci. and Remote Sensing Letters, vol. 7, no.2, pp. 231-235, April 2010. [2] Senet, C. M., Seemann, J., Flampouris, S., and Ziemer, F. (2008). Determination of bathymetric and current maps by the method DiSC based on the analysis of nautical X-Band radar image sequences of the sea surface (November 2007). IEEE Trans. on Geoscience and Remote Sensing, 46(8), 2267-2279. [3] F. Ziemer, and W. Rosenthal, "Directional spectra from shipboard navigation radar during LEWEX". Directional Ocean Wave Spectra: Measuring, Modeling, Predicting, and Applying, 1991 R. C. Beal, Ed., The Johns Hopkins University Press, pp. 125-127. [4] Weimin Huang ; Gill, E.," Surface Current Measurement Under Low Sea State Using Dual Polarized X-Band Nautical Radar", Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of, vol. 5, no.6, page 186-1873, 2012.

Application of new parameterizations of gas transfer velocity and their impact on regional and global marine CO 2 budgets

NASA Astrophysics Data System (ADS)

Fangohr, Susanne; Woolf, David K.

2007-06-01

One of the dominant sources of uncertainty in the calculation of air-sea flux of carbon dioxide on a global scale originates from the various parameterizations of the gas transfer velocity, k, that are in use. Whilst it is undisputed that most of these parameterizations have shortcomings and neglect processes which influence air-sea gas exchange and do not scale with wind speed alone, there is no general agreement about their relative accuracy. The most widely used parameterizations are based on non-linear functions of wind speed and, to a lesser extent, on sea surface temperature and salinity. Processes such as surface film damping and whitecapping are known to have an effect on air-sea exchange. More recently published parameterizations use friction velocity, sea surface roughness, and significant wave height. These new parameters can account to some extent for processes such as film damping and whitecapping and could potentially explain the spread of wind-speed based transfer velocities published in the literature. We combine some of the principles of two recently published k parameterizations [Glover, D.M., Frew, N.M., McCue, S.J. and Bock, E.J., 2002. A multiyear time series of global gas transfer velocity from the TOPEX dual frequency, normalized radar backscatter algorithm. In: Donelan, M.A., Drennan, W.M., Saltzman, E.S., and Wanninkhof, R. (Eds.), Gas Transfer at Water Surfaces, Geophys. Monograph 127. AGU,Washington, DC, 325-331; Woolf, D.K., 2005. Parameterization of gas transfer velocities and sea-state dependent wave breaking. Tellus, 57B: 87-94] to calculate k as the sum of a linear function of total mean square slope of the sea surface and a wave breaking parameter. This separates contributions from direct and bubble-mediated gas transfer as suggested by Woolf [Woolf, D.K., 2005. Parameterization of gas transfer velocities and sea-state dependent wave breaking. Tellus, 57B: 87-94] and allows us to quantify contributions from these two processes independently. We then apply our parameterization to a monthly TOPEX altimeter gridded 1.5° × 1.5° data set and compare our results to transfer velocities calculated using the popular wind-based k parameterizations by Wanninkhof [Wanninkhof, R., 1992. Relationship between wind speed and gas exchange over the ocean. J. Geophys. Res., 97: 7373-7382.] and Wanninkhof and McGillis [Wanninkhof, R. and McGillis, W., 1999. A cubic relationship between air-sea CO2 exchange and wind speed. Geophys. Res. Lett., 26(13): 1889-1892]. We show that despite good agreement of the globally averaged transfer velocities, global and regional fluxes differ by up to 100%. These discrepancies are a result of different spatio-temporal distributions of the processes involved in the parameterizations of k, indicating the importance of wave field parameters and a need for further validation.

Distribution of Surface pH and Total Alkalinity at the Sea of Okhotsk and the East Sea in October 2007

NASA Astrophysics Data System (ADS)

Shim, J.; Kang, D.; Jin, Y.; Obzhirov, A.

2008-12-01

Surface pH, total alkalinity, temperature and salinity were measured at the Sea of Okhotsk and the East Sea (along a track from Vladivostok to the northeastern slope of Sakhalin Island through Soya Strait: 42°N, 132°E - 55°N, 145°E) in October 2007. Continuous pH measurements were conducted using an underway potentiometric pH system modified from Tishchenko et al. (2002) and discrete total alkalinity measurements were made by direct titration with hydrochloric acid. Warm saline surface waters were observed in the East Sea (from Vladivostok to Soya Strait), and relatively cold less-saline waters were observed in the Sea of Okhotsk (at the eastern slopes of Sakhalin Island). In the East Sea and the Sea of Okhotsk, surface pH ranged from 8.063 to 8.158 and 8.047 to 8.226, and total alkalinity normalized to salinity 35 ranged from 2323 to 2344 μmol kg-1 and 2367 to 2422 μmol kg-1, respectively. Due to the freshwater input from rivers and geochemical activity in the water column and sediment, the Sea of Okhotsk generally showed much wider ranges of water properties and richer in carbonate parameters than those of the East Sea. Particularly, water properties changed dramatically at the eastern slopes of Sakhalin Island; surface salinity decreased southward by about 0.5-1 psu and pH and normalized total alkalinity increased southward by about 0.05-0.1 and 20-50 μmol kg-1, respectively. Thus, pCO2 concentration calculated from pH and total alkalinity, ranged from 350-375 μatm in the north to 280-300 μatm in the south of the Okhotsk Sea. The high pH and normalized total alkalinity, and low pCO2 and salinity in the south might be the result of surface water mixing with fresh water discharge from rivers and/or the results of massive primary production along the eastern coast of Sakhalin Island. In the most study area, surface pCO2 ranged from 280 to 370 μatm and was undersaturated relative to atmosphere. Therefore, the Sea of Okhotsk and the East Sea acted as effective CO2 sinks during the study period

Simulation of oceanic whitecaps and their reflectance characteristics in the short wavelength infrared.

PubMed

Schwenger, Frédéric; Repasi, Endre

2017-02-20

The knowledge of the spatial energy (or power) distribution of light beams reflected at the dynamic sea surface is of great practical interest in maritime environments. For the estimation of the light energy reflected into a specific spatial direction a lot of parameters need to be taken into account. Both whitecap coverage and its optical properties have a large impact upon the calculated value. In published literature, for applications considering vertical light propagation paths, such as bathymetric lidar, the reflectance of sea surface and whitecaps are approximated by constant values. For near-horizontal light propagation paths the optical properties of the sea surface and the whitecaps must be considered in greater detail. The calculated light energy reflected into a specific direction varies statistically and depends largely on the dynamics of the wavy sea surface and the dynamics of whitecaps. A 3D simulation of the dynamic sea surface populated with whitecaps is presented. The simulation considers the evolution of whitecaps depending on wind speed and fetch. The radiance calculation of the maritime scene (open sea/clear sky) populated with whitecaps is done in the short wavelength infrared spectral band. Wave hiding and shadowing, especially occurring at low viewing angles, are considered. The specular reflection of a light beam at the sea surface in the absence of whitecaps is modeled by an analytical statistical bidirectional reflectance distribution function (BRDF) of the sea surface. For whitecaps, a specific BRDF is used by taking into account their shadowing function. To ensure the credibility of the simulation, the whitecap coverage is determined from simulated image sequences for different wind speeds and compared to whitecap coverage functions from literature. The impact of whitecaps on the radiation balance for bistatic configuration of light source and receiver is calculated for a different incident (zenith/azimuth angles) of the light beam and is presented for two different wind speeds.

File Specification for the MERRA Aerosol Reanalysis (MERRAero): MODIS AOD Assimilation based on a MERRA Replay

NASA Technical Reports Server (NTRS)

Da Silva, A. M.; Randles, C. A.; Buchard, V.; Darmenov, A.; Colarco, P. R.; Govindaraju, R.

2015-01-01

This document describes the gridded output files produced by the Goddard Earth Observing System version 5 (GEOS-5) Goddard Aerosol Assimilation System (GAAS) from July 2002 through December 2014. The MERRA Aerosol Reanalysis (MERRAero) is produced with the hydrostatic version of the GEOS-5 Atmospheric Global Climate Model (AGCM). In addition to standard meteorological parameters (wind, temperature, moisture, surface pressure), this simulation includes 15 aerosol tracers (dust, sea-salt, sulfate, black and organic carbon), ozone, carbon monoxide and carbon dioxide. This model simulation is driven by prescribed sea-surface temperature and sea-ice, daily volcanic and biomass burning emissions, as well as high-resolution inventories of anthropogenic emission sources. Meteorology is replayed from the MERRA Reanalysis.

Microwave properties of sea ice in the marginal ice zone

NASA Technical Reports Server (NTRS)

Onstott, R. G.; Larson, R. W.

1986-01-01

Active microwave properties of summer sea ice were measured. Backscatter data were acquired at frequencies from 1 to 17 GHz, at angles from 0 to 70 deg from vertical, and with like and cross antenna polarizations. Results show that melt-water, snow thickness, snowpack morphology, snow surface roughness, ice surface roughness, and deformation characteristics are the fundamental scene parameters which govern the summer sea ice backscatter response. A thick, wet snow cover dominates the backscatter response and masks any ice sheet features below. However, snow and melt-water are not distributed uniformly and the stage of melt may also be quite variable. These nonuniformities related to ice type are not necessarily well understood and produce unique microwave signature characteristics.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dong, B.; Valdes, P.J.

The U.K. University Global Atmospheric Modeling Programme GCM is used to investigate whether the growth of Northern Hemisphere ice sheets could have been initiated by changes of orbital parameters and sea surface temperatures. Two different orbital configurations, corresponding to the present day and 115 kyr BP are used. The reduced summer solar insolation in the Northern Hemisphere results in a decrease of the surface temperature by 4{degrees} to 10{degrees}C in the northern continents and to perennial snow in some high-latitude regions. Therefore, the model results support the hypothesis that a deficit of summer insolation can create conditions favorable for initiationmore » of ice sheet growth in the Northern Hemisphere. A decreased sea surface temperature northward of 65{degrees}N during the Northern Hemisphere summer may contribute to the maintenance of ice sheets. A simple mixed-layer ocean model coupled to the GCM indicates that the changes of sea surface temperature and extension of sea ice due to insolation changes play an important role in inception of the Fennoscandian, Laurentide, and Cordilleran ice sheets. The model results suggest that the regions of greatest sensitivity for ice initiation are the Canadian Archipelago, Baffin Island, Tibetan Plateau, Scandinavia, Siberia, Alaska, and Keewatin, where changing orbital parameters to 115 kyr BP results in the snow cover remaining throughout the warmer summer, leading to long-term snow accumulation. The model results are in general agreement with geological evidence and are the first time that a GCM coupled with a mixed layer ocean has reproduced the inception of the Northern Hemisphere ice sheets. 69 refs., 21 figs., 3 tabs.« less

Study on wind wave variability by inhomogeneous currents in the closed seas

NASA Astrophysics Data System (ADS)

Bakhanov, Victor V.; Bogatov, Nikolai A.; Ermoshkin, Aleksei V.; Ivanov, Andrei Yu.; Kemarskaya, Olga N.; Titov, Victor I.

2012-09-01

Complex experiments were performed in the north-eastern part of the Black Sea and in the south-eastern part of the White Sea to study variability of the current fields and other characteristics of the sea, wind waves, and parameters of the near-surface atmospheric layer. Measurements were carried out from the onboard of the scientific research vessels by optical, radar and acoustic sensors. The heterogeneity of bottom topography in Black Sea had quasi-one-dimensional character. The case of the two-dimensionally heterogeneous relief of the bottom was investigated in the White Sea. The peculiarity of these experiments was simultaneous measurements from onboard of vessel synchronously with acquisitions of synthetic aperture radar (SAR) images of the Envisat and TerraSAR-X satellites. We have detected for the case of the quasi-one-dimensionally heterogeneous current a difference between the sea surface roughness above the shelf zone and the roughness at the deep bottom. We found that the inhomogeneities of the bottom topography can manifest as a change not only in the amplitude of different characteristics of surface wave and atmospheric near-water layer, but also in their frequency spectrum. In White Sea the special features of the flow of the powerful tidal current (up to 1 m/s) around the secluded underwater elevation and the spatial structure of surface anomalies in the field of these two-dimensional-heterogeneous currents are analyzed. The numerical simulation of the wind wave transformation in the field of two-dimensional- heterogeneous flows is carried out. The qualitative agreement of the calculation results with the experimental data is shown.

Solvothermal synthesis and high optical performance of three-dimensional sea-urchin-like TiO{sub 2}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Yi, E-mail: zhouyihn@163.com; Wang, Yutang; Li, Mengyao

Graphical abstract: I–V characteristics of different TiO{sub 2} microspheres based DSSCs (a) 3D sphere-like, (b) 3D flower-like, (c) 3D sea-urchin-like. - Highlights: • 3D sea-urchin-like TiO{sub 2} was synthesized by solvothermal method. • The effects of preparation parameters on the microstructure of the microspheres were investigated. • The photoelectric properties of 3D sea-urchin-like TiO{sub 2} were studied upon DSSCs. • The PCE of the 3D sea-urchin-like TiO{sub 2} was higher than that of other morphologies. - Abstract: Three-dimensional (3D) sea-urchin-like TiO{sub 2} microspheres were successfully synthesised by solvothermal method. The effects of preparation parameters including reaction temperature, concentration and massmore » fraction of precursor, and solvent volume on the microstructure of the microspheres were investigated. Results of scanning electron microscopy showed that the preparation parameters played a critical role in the morphology of 3D sea-urchin-like TiO{sub 2}. In addition, when the sea-urchin-like TiO{sub 2} nanostructures were used as the dye-sensitized solar cells (DSSCs) anode, the power-conversion efficiency was higher than that of other morphologies, which was due to the special 3D hierarchical nanostructure, large specific surface area, and enhanced absorption of UV–vis of the TiO{sub 2} nanostructures.« less

Simple heterogeneity parametrization for sea surface temperature and chlorophyll

NASA Astrophysics Data System (ADS)

Skákala, Jozef; Smyth, Timothy J.

2016-06-01

Using satellite maps this paper offers a complex analysis of chlorophyll & SST heterogeneity in the shelf seas around the southwest of the UK. The heterogeneity scaling follows a simple power law and is consequently parametrized by two parameters. It is shown that in most cases these two parameters vary only relatively little with time. The paper offers a detailed comparison of field heterogeneity between different regions. How much heterogeneity is in each region preserved in the annual median data is also determined. The paper explicitly demonstrates how one can use these results to calculate representative measurement area for in situ networks.

A simple model for the evolution of melt pond coverage on permeable Arctic sea ice

NASA Astrophysics Data System (ADS)

Popović, Predrag; Abbot, Dorian

2017-05-01

As the melt season progresses, sea ice in the Arctic often becomes permeable enough to allow for nearly complete drainage of meltwater that has collected on the ice surface. Melt ponds that remain after drainage are hydraulically connected to the ocean and correspond to regions of sea ice whose surface is below sea level. We present a simple model for the evolution of melt pond coverage on such permeable sea ice floes in which we allow for spatially varying ice melt rates and assume the whole floe is in hydrostatic balance. The model is represented by two simple ordinary differential equations, where the rate of change of pond coverage depends on the pond coverage. All the physical parameters of the system are summarized by four strengths that control the relative importance of the terms in the equations. The model both fits observations and allows us to understand the behavior of melt ponds in a way that is often not possible with more complex models. Examples of insights we can gain from the model are that (1) the pond growth rate is more sensitive to changes in bare sea ice albedo than changes in pond albedo, (2) ponds grow slower on smoother ice, and (3) ponds respond strongest to freeboard sinking on first-year ice and sidewall melting on multiyear ice. We also show that under a global warming scenario, pond coverage would increase, decreasing the overall ice albedo and leading to ice thinning that is likely comparable to thinning due to direct forcing. Since melt pond coverage is one of the key parameters controlling the albedo of sea ice, understanding the mechanisms that control the distribution of pond coverage will help improve large-scale model parameterizations and sea ice forecasts in a warming climate.

Estimation of sea surface temperature from remote measurements in the 11-13 micron window region

NASA Technical Reports Server (NTRS)

Prabhakara, C.; Conrath, B. J.; Kunde, V. G.

1972-01-01

The Nimbus-4 IRIS data was examined in the spectral region 775 to 1250/cm (8-13 microns) for useful information to determine the sea surface temperature. The high spectral resolution data of IRIS was degraded to low resolution by averaging to simulate a multi-channel radiometer in the window region. These simulated data show that within the region 775-975/cm (12.9-10.25 microns) the brightness temperatures are linearly related to the absorption parameters. Such a linear relationship is observed over cloudy as well as clear regions and over a wide range of latitudes. From this linear relationship it is feasible to correct for the atmospheric attenuation and get the sea surface temperature, accurate to within 1 K, in a cloud free field of view. The information about the cloud cover is taken from the TV pictures and BUV albedo measurements on board the Nimbus-4 satellite.

Sedimentology and geochemistry of mud volcanoes in the Anaximander Mountain Region from the Eastern Mediterranean Sea.

PubMed

Talas, Ezgi; Duman, Muhammet; Küçüksezgin, Filiz; Brennan, Michael L; Raineault, Nicole A

2015-06-15

Investigations carried out on surface sediments collected from the Anaximander mud volcanoes in the Eastern Mediterranean Sea to determine sedimentary and geochemical properties. The sediment grain size distribution and geochemical contents were determined by grain size analysis, organic carbon, carbonate contents and element analysis. The results of element contents were compared to background levels of Earth's crust. The factors that affect element distribution in sediments were calculated by the nine push core samples taken from the surface of mud volcanoes by the E/V Nautilus. The grain size of the samples varies from sand to sandy silt. Enrichment and Contamination factor analysis showed that these analyses can also be used to evaluate of deep sea environmental and source parameters. It is concluded that the biological and cold seep effects are the main drivers of surface sediment characteristics from the Anaximander mud volcanoes. Copyright © 2015 Elsevier Ltd. All rights reserved.

Estimation of mean sea surfaces in the north Atlantic, the Pacific and the Indian Ocean using GEOS-3 altimeter data

NASA Technical Reports Server (NTRS)

Marsh, J. G.; Martin, T. V.; Mccarthy, J. J.; Chovitz, P. S.

1979-01-01

The mean surfaces of several regions of the world's oceans were estimated using GEOS-3 altimeter data. The northwest Atlantic, the northeast Pacific off the coast of California, the Indian Ocean, the southwest Pacific, and the Phillipine Sea are included. These surfaces have been oriented with respect to a common earth center-of-mass system by constraining the separate solutions to conform to precisely determined laser reference control orbits. The same reference orbits were used for all regions assuring continuity of the separate solutions. Radial accuracies of the control orbits were in the order of one meter. The altimeter measured sea surface height crossover differences were minimized by the adjustment of tilt and bias parameters for each pass with the exception of laser reference control passes. The tilt and bias adjustments removed long wavelength errors which were primarily due to orbit error. Ocean tides were evaluated. The resolution of the estimated sea surfaces varied from 0.25 degrees off the east coast of the United States to about 2 degrees in part of the Indian Ocean near Australia. The rms crossover discrepancy after adjustment varied from 30 cm to 70 cm depending upon geographic location. Comparisons of the altimeter derived mean sea surface in the North Atlantic with the 5 feet x 5 feet GEM-8 detailed gravimetric geoid indicated a relative consistency of better than a meter.

Discrete-Element bonded-particle Sea Ice model DESIgn, version 1.3a - model description and implementation

NASA Astrophysics Data System (ADS)

Herman, Agnieszka

2016-04-01

This paper presents theoretical foundations, numerical implementation and examples of application of the two-dimensional Discrete-Element bonded-particle Sea Ice model - DESIgn. In the model, sea ice is represented as an assemblage of objects of two types: disk-shaped "grains" and semi-elastic bonds connecting them. Grains move on the sea surface under the influence of forces from the atmosphere and the ocean, as well as interactions with surrounding grains through direct contact (Hertzian contact mechanics) and/or through bonds. The model has an experimental option of taking into account quasi-three-dimensional effects related to the space- and time-varying curvature of the sea surface, thus enabling simulation of ice breaking due to stresses resulting from bending moments associated with surface waves. Examples of the model's application to simple sea ice deformation and breaking problems are presented, with an analysis of the influence of the basic model parameters ("microscopic" properties of grains and bonds) on the large-scale response of the modeled material. The model is written as a toolbox suitable for usage with the open-source numerical library LIGGGHTS. The code, together with full technical documentation and example input files, is freely available with this paper and on the Internet.

Arctic Ocean CO2 uptake: an improved multiyear estimate of the air-sea CO2 flux incorporating chlorophyll a concentrations

NASA Astrophysics Data System (ADS)

Yasunaka, Sayaka; Siswanto, Eko; Olsen, Are; Hoppema, Mario; Watanabe, Eiji; Fransson, Agneta; Chierici, Melissa; Murata, Akihiko; Lauvset, Siv K.; Wanninkhof, Rik; Takahashi, Taro; Kosugi, Naohiro; Omar, Abdirahman M.; van Heuven, Steven; Mathis, Jeremy T.

2018-03-01

We estimated monthly air-sea CO2 fluxes in the Arctic Ocean and its adjacent seas north of 60° N from 1997 to 2014. This was done by mapping partial pressure of CO2 in the surface water (pCO2w) using a self-organizing map (SOM) technique incorporating chlorophyll a concentration (Chl a), sea surface temperature, sea surface salinity, sea ice concentration, atmospheric CO2 mixing ratio, and geographical position. We applied new algorithms for extracting Chl a from satellite remote sensing reflectance with close examination of uncertainty of the obtained Chl a values. The overall relationship between pCO2w and Chl a was negative, whereas the relationship varied among seasons and regions. The addition of Chl a as a parameter in the SOM process enabled us to improve the estimate of pCO2w, particularly via better representation of its decline in spring, which resulted from biologically mediated pCO2w reduction. As a result of the inclusion of Chl a, the uncertainty in the CO2 flux estimate was reduced, with a net annual Arctic Ocean CO2 uptake of 180 ± 130 Tg C yr-1. Seasonal to interannual variation in the CO2 influx was also calculated.

Impact of water depth on the distribution of iGDGTs in the surface sediments from the northern South China Sea: applicability of TEX86 in marginal seas

NASA Astrophysics Data System (ADS)

Chen, Jiali; Hu, Pengju; Li, Xing; Yang, Yang; Song, Jinming; Li, Xuegang; Yuan, Huamao; Li, Ning; Lü, Xiaoxia

2018-03-01

The TEX 86 H paleothermometer on the base of isoprenoid glycerol dialkyl glycerol tetraethers (iGDGTs) has been widely applied to various marine settings to reconstruct past sea surface temperatures (SSTs). However, it remains uncertain how well this proxy reconstructs SSTs in marginal seas. In this study, we analyze the environmental factors governing distribution of iGDGTs in surface sediments to assess the applicability of TEX 86 H paleothermometer in the South China Sea (SCS). Individual iGDGT concentrations increase gradually eastwards. Redundancy analysis based on the relative abundance of an individual iGDGT compound and environmental parameters suggests that water depth is the most influential factor to the distribution of iGDGTs, because thaumarchaeota communities are water-depth dependent. Interestingly, the SST difference (Δ T) between TEX 86 H derived temperature and remote-sensing SST is less than 1°C in sediments with water depth>200 m, indicating that TEX 86 H was the robust proxy to trace the paleo-SST in the region if water depth is greater than 200 m.

Evaluation of geophysical parameters measured by the Nimbus-7 microwave radiometer for the TOGA Heat Exchange Project

NASA Technical Reports Server (NTRS)

Liu, W. Timothy; Mock, Donald R.

1986-01-01

The data distributed by the National Space Science Data Center on the Geophysical parameters of precipitable water, sea surface temperature, and surface-level wind speed, measured by the Scanning Multichannel Microwave Radiometer (SMMR) on Nimbus-7, are evaluated with in situ measurements between Jan. 1980 and Oct. 1983 over the tropical oceans. In tracking annual cycles and the 1982-83 E1 Nino/Southern Oscillation episode, the radiometer measurements are coherent with sea surface temperatures and surface-level wind speeds measured at equatorial buoys and with precipitable water derived from radiosonde soundings at tropical island stations. However, there are differences between SMMR and in situ measurements. Corrections based on radiosonde and ship data were derived supplementing correction formulae suggested in the databook. This study is the initial evaluation of the data for quantitative description of the 1982-83 E1 Nino/Southern Oscillation episode. It paves the way for determination of the ocean-atmosphere moisture and latent heat exchanges, a priority of the Tropical Ocean and Global Atmosphere (TOGA) Heat Exchange Program.

Environmental studies of the Arabian Sea using remote sensing and GIS

NASA Astrophysics Data System (ADS)

Saxena, Ashlesha; Menezes, Andrew

2006-12-01

The Arabian Sea, situated in the western part of the northern Indian Ocean is a tropical basin. It is bounded on the east by the Indian peninsula, on the north by Baluchistan and Sindh provinces of Pakistan and on the west by the landmass of Arabia and Africa. The environmental factors that influence this tropical basin are the seasonally changing winds from the northeast during winter (November-February) and southwest during summer (June to September). Accordingly, the waters of the basin will experience seasonal variations. The study aims at understanding the seasonal and inter-annual variation of the Arabian Sea using satellite-derived data. The spatial domain selected for the present study is 40 degrees E and 78 degrees E longitude and equator to 30 degrees N. The remote sensing data with respect to sea surface temperature (SST), sea surface wind, sea surface height (SSH), and chlorophyll pigment concentration during January 2002 to December 2005 were used to understand the spatio-temporal variability of the Arabian Sea. The monthly mean SST data was obtained from Modis aqua, winds from Quikscat and chlorophyll pigment concentration from SeaWiFS. The SSH anomaly data was obtained from the merged product - Topex/Poseidon ERS 1/2 satellite which is 7-day snapshot. The spatial resolution of these data is 0.3 degrees latitude x 0.3 degrees longitude. Geographical information system (GIS) was used for processing and analysing the above parameters to determine the variability and detection of oceanic processes that are responsible for such variability.The study showed a very strong inverse correlation between SST and chlorophyll concentrations. Arabian Sea undergoes cooling during summer due to upwelling and advection, and in winter due to surface cooling under reduced solar heating. Upwelling along the coasts of Somalia, Arabia, and the west coast of India brings cold and nutrient rich sub-surface waters to the surface, which supports the observed high chlorophyll concentrations. During winter the convective mixing in the northern Arabian Sea supports high chlorophyll pigment concentrations. Due to strong solar heating, SST was warmest in spring (April), which supported least chlorophyll concentration.llite

The characteristics of dissolved organic matter (DOM) and chromophoric dissolved organic matter (CDOM) in Antarctic sea ice

NASA Astrophysics Data System (ADS)

Norman, Louiza; Thomas, David N.; Stedmon, Colin A.; Granskog, Mats A.; Papadimitriou, Stathys; Krapp, Rupert H.; Meiners, Klaus M.; Lannuzel, Delphine; van der Merwe, Pier; Dieckmann, Gerhard S.

2011-05-01

An investigation of coloured dissolved organic matter (CDOM) and its relationships to physical and biogeochemical parameters in Antarctic sea ice and oceanic water have indicated that ice melt may both alter the spectral characteristics of CDOM in Antarctic surface waters and serve as a likely source of fresh autochthonous CDOM and labile DOC. Samples were collected from melted bulk sea ice, sea ice brines, surface gap layer waters, and seawater during three expeditions: one during the spring to summer and two during the winter to spring transition period. Variability in both physical (temperature and salinity) and biogeochemical parameters (dissolved and particulate organic carbon and nitrogen, as well as chlorophyll a) was observed during and between studies, but CDOM absorption coefficients measured at 375 nm (a 375) did not differ significantly. Distinct peaked absorption spectra were consistently observed for bulk ice, brine, and gap water, but were absent in the seawater samples. Correlation with the measured physical and biogeochemical parameters could not resolve the source of these peaks, but the shoulders and peaks observed between 260 and 280 nm and between 320 to 330 nm respectively, particularly in the samples taken from high light-exposed gap layer environment, suggest a possible link to aromatic and mycosporine-like amino acids. Sea ice CDOM susceptibility to photo-bleaching was demonstrated in an in situ 120 hour exposure, during which we observed a loss in CDOM absorption of 53% at 280 nm, 58% at 330 nm, and 30% at 375 nm. No overall coincidental loss of DOC or DON was measured during the experimental period. A relationship between the spectral slope (S) and carbon-specific absorption (a *375) indicated that the characteristics of CDOM can be described by the mixing of two broad end-members; and aged material, present in brine and seawater samples characterised by high S values and low a *375; and a fresh material, due to elevated in situ production, present in the bulk ice samples characterised by low S and high a *375. The DOC data reported here have been used to estimate that approximately 8 Tg C yr -1 (˜11% of annual sea ice algae primary production) may be exported to the surface ocean during seasonal sea ice melt in the form of DOC.

Symmetry in polarimetric remote sensing

NASA Technical Reports Server (NTRS)

Nghiem, S. V.; Yueh, S. H.; Kwok, R.

1993-01-01

Relationships among polarimetric backscattering coefficients are derived from the viewpoint of symmetry groups. For both reciprocal and non-reciprocal media, symmetry encountered in remote sensing due to reflection, rotation, azimuthal, and centrical symmetry groups is considered. The derived properties are general and valid to all scattering mechanisms, including volume and surface scatterings and their interactions, in a given symmetrical configuration. The scattering coefficients calculated from theoretical models for layer random media and rough surfaces are shown to obey the symmetry relations. Use of symmetry properties in remote sensing of structural and environmental responses of scattering media is also discussed. Orientations of spheroidal scatterers described by spherical, uniform, planophile, plagiothile, erectophile, and extremophile distributions are considered to derive their polarimetric backscattering characteristics. These distributions can be identified from the observed scattering coefficients by comparison with theoretical symmetry calculations. A new parameter is then defined to study scattering structures in geophysical media. Observations from polarimetric data acquired by the Jet Propulsion Laboratory airborne synthetic aperture radar over forests, sea ice, and sea surface are presented. Experimental evidences of the symmetry relationships are shown and their use in polarimetric remote sensing is illustrated. For forests, the coniferous forest in Mt. Shasta area (California) and mixed forest near Presque Isle (Maine) exhibit characteristics of the centrical symmetry at C-band. For sea ice in the Beaufort Sea, multi-year sea ice has a cross-polarized ratio e close to e(sub 0), calculated from symmetry, due to the randomness in the scattering structure. First-year sea ice has e much smaller than e(sub 0) due to the preferential alignment of the columnar structure of the ice. From polarimetric data of a sea surface in the Bering Sea, it is observed that e and e(sub 0) are increasing with incident angle and e is greater than e(sub 0) at L-band because of the directional feature of sea surface waves. Symmetry properties of geophysical media can also be used to calibrate polarimetric radars.

Pattern Analysis of El Nino and La Nina Phenomenon Based on Sea Surface Temperature (SST) and Rainfall Intensity using Oceanic Nino Index (ONI) in West Java Area

NASA Astrophysics Data System (ADS)

Prasetyo, Yudo; Nabilah, Farras

2017-12-01

Climate change occurs in 1998-2016 brings significant alteration in the earth surface. It is affects an extremely anomaly temperature such as El Nino and La Nina or mostly known as ENSO (El Nino Southern Oscillation). West Java is one of the regions in Indonesia that encounters the impact of this phenomenon. Climate change due to ENSO also affects food production and other commodities. In this research, processing data method is conducted using programming language to process SST data and rainfall data from 1998 to 2016. The data are sea surface temperature from NOAA satellite, SST Reynolds (Sea Surface Temperature) and daily rainfall temperature from TRMM satellite. Data examination is done using analysis of rainfall spatial pattern and sea surface temperature (SST) where is affected by El Nino and La Nina phenomenon. This research results distribution map of SST and rainfall for each season to find out the impacts of El Nino and La Nina around West Java. El Nino and La Nina in Java Sea are occurring every August to February. During El Nino, sea surface temperature is between 27°C - 28°C with average temperature on 27.71°C. Rainfall intensity is 1.0 mm/day - 2.0 mm/day and the average are 1.63 mm/day. During La Nina, sea surface temperature is between 29°C - 30°C with average temperature on 29.06°C. Rainfall intensity is 9.0 mm/day - 10 mm/day, and the average is 9.74 mm/day. The correlation between rainfall and SST is 0,413 which is expresses a fairly strong correlation between parameters. The conclusion is, during La Nina SST and rainfall increase. While during El Nino SST and rainfall decrease. Hopefully this research could be a guideline to plan disaster mitigation in West Java region that is related extreme climate change.

Problems in Assessment of the UV Penetration into Natural Waters from Space-based Measurements

NASA Technical Reports Server (NTRS)

Vasilkov, Alexander P.; Herman, Jay; Krotkov, Nickolay A.; Kahru, Mati; Mitchell, B. Greg; Hsu, Christina; Bhartia, P. K. (Technical Monitor)

2002-01-01

Satellite instruments currently provide global maps of surface UV (ultraviolet) irradiance by combining backscattered radiance data with radiative transfer models. The models are often limited by uncertainties in physical input parameters of the atmosphere and surface. Global mapping of the underwater UV irradiance creates further challenges for the models. The uncertainties in physical input parameters become more serious because of the presence of absorbing and scattering quantities caused by biological processes within the oceans. In this paper we summarize the problems encountered in the assessment of the underwater UV irradiance from space-based measurements, and propose approaches to resolve the problems. We have developed a radiative transfer scheme for computation of the UV irradiance in the atmosphere-ocean system. The scheme makes use of input parameters derived from satellite instruments such as TOMS (Total Ozone Mapping Spectrometer) and SeaWiFS (Sea-viewing Wide Field-of-view Sensor). The major problem in assessment of the surface UV irradiance is to accurately quantify the effects of clouds. Unlike the standard TOMS UV algorithm, we use the cloud fraction products available from SeaWiFS and MODIS (Moderate Resolution Imaging Spectrometer) to calculate instantaneous surface flux at the ocean surface. Daily UV doses can be calculated by assuming a model of constant cloudiness throughout the day. Both SeaWiFS and MODIS provide some estimates of seawater optical properties in the visible. To calculate the underwater UV flux the seawater optical properties must be extrapolated down to shorter wavelengths. Currently, the problem of accurate extrapolation of visible data down to the UV spectral range is not solved completely, and there are few available measurements. The major difficulty is insufficient correlation between photosynthetic and photoprotective pigments of phytoplankton absorbing in the visible and UV respectively. We propose to empirically parameterize seawater absorption in the UV on a basis of available data sets of bio-optical measurements from a variety of ocean waters. Another problem is the lack of reliable data on pure seawater absorption in the UV. Laboratory measurements of the UV absorption of both pure water and pure seawater are required.

Fault Slip Distribution and Optimum Sea Surface Displacement of the 2017 Tehuantepec Earthquake in Mexico (Mw 8.2) Estimated from Tsunami Waveforms

NASA Astrophysics Data System (ADS)

Gusman, A. R.; Satake, K.; Mulia, I. E.

2017-12-01

An intraplate normal fault earthquake (Mw 8.2) occurred on 8 September 2017 in the Tehuantepec seismic gap of the Middle America Trench. The submarine earthquake generated a tsunami which was recorded by coastal tide gauges and offshore DART buoys. We used the tsunami waveforms recorded at 16 stations to estimate the fault slip distribution and an optimum sea surface displacement of the earthquake. A steep fault dipping to the northeast with strike of 315°, dip of 73°and rake of -96° based on the USGS W-phase moment tensor solution was assumed for the slip inversion. To independently estimate the sea surface displacement without assuming earthquake fault parameters, we used the B-spline function for the unit sources. The distribution of the unit sources was optimized by a Genetic Algorithm - Pattern Search (GA-PS) method. Tsunami waveform inversion resolves a spatially compact region of large slip (4-10 m) with a dimension of 100 km along the strike and 80 km along the dip in the depth range between 40 km and 110 km. The seismic moment calculated from the fault slip distribution with assumed rigidity of 6 × 1010 Nm-2 is 2.46 × 1021 Nm (Mw 8.2). The optimum displacement model suggests that the sea surface was uplifted up to 0.5 m and subsided down to -0.8 m. The deep location of large fault slip may be the cause of such small sea surface displacements. The simulated tsunami waveforms from the optimum sea surface displacement can reproduce the observations better than those from fault slip distribution; the normalized root mean square misfit for the sea surface displacement is 0.89, while that for the fault slip distribution is 1.04. We simulated the tsunami propagation using the optimum sea surface displacement model. Large tsunami amplitudes up to 2.5 m were predicted to occur inside and around a lagoon located between Salina Cruz and Puerto Chiapas. Figure 1. a) Sea surface displacement for the 2017 Tehuantepec earthquake estimated by tsunami waveforms. b) Map of simulated maximum tsunami amplitude and comparison between observed (blue circles) and simulated (red circles) tsunami maximum amplitude along the coast.

Determination of some dominant parameters of the global dynamic sea surface topography from GEOS-3 altimetry

NASA Technical Reports Server (NTRS)

Mather, R. S.; Lerch, F. J.; Rizos, C.; Masters, E. G.; Hirsch, B.

1978-01-01

The 1977 altimetry data bank is analyzed for the geometrical shape of the sea surface expressed as surface spherical harmonics after referral to the higher reference model defined by GEM 9. The resulting determination is expressed as quasi-stationary dynamic SST. Solutions are obtained from different sets of long arcs in the GEOS-3 altimeter data bank as well as from sub-sets related to the September 1975 and March 1976 equinoxes assembled with a view to minimizing seasonal effects. The results are compared with equivalent parameters obtained from the hydrostatic analysis of sporadic temperature, pressure and salinity measurements of the oceans and the known major steady state current systems with comparable wavelengths. The most clearly defined parameter (the zonal harmonic of degree 2) is obtained with an uncertainty of + or - 6 cm. The preferred numerical value is smaller than the oceanographic value due to the effect of the correction for the permanent earth tide. Similar precision is achieved for the zonal harmonic of degree 3. The precision obtained for the fourth degree zonal harmonic reflects more closely the accuracy expected from the level of noise in the orbital solutions.

State of the Oceans: A Satellite Data Processing System for Visualizing Near Real-Time Imagery on Google Earth

NASA Astrophysics Data System (ADS)

Thompson, C. K.; Bingham, A. W.; Hall, J. R.; Alarcon, C.; Plesea, L.; Henderson, M. L.; Levoe, S.

2011-12-01

The State of the Oceans (SOTO) web tool was developed at NASA's Physical Oceanography Distributed Active Archive Center (PO.DAAC) at the Jet Propulsion Laboratory (JPL) as an interactive means for users to visually explore and assess ocean-based geophysical parameters extracted from the latest archived data products. The SOTO system consists of four extensible modules, a data polling tool, a preparation and imaging package, image server software, and the graphical user interface. Together, these components support multi-resolution visualization of swath (Level 2) and gridded Level 3/4) data products as either raster- or vector- based KML layers on Google Earth. These layers are automatically updated periodically throughout the day. Current parameters available include sea surface temperature, chlorophyll concentration, ocean winds, sea surface height anomaly, and sea surface temperature anomaly. SOTO also supports mash-ups, allowing KML feeds from other sources to be overlaid directly onto Google Earth such as hurricane tracks and buoy data. A version of the SOTO software has also been installed at Goddard Space Flight Center (GSFC) to support the Land Atmosphere Near real-time Capability for EOS (LANCE). The State of the Earth (SOTE) has similar functionality to SOTO but supports different data sets, among them the MODIS 250m data product.

Observational Studies of Parameters Influencing Air-sea Gas Exchange

NASA Astrophysics Data System (ADS)

Schimpf, U.; Frew, N. M.; Bock, E. J.; Hara, T.; Garbe, C. S.; Jaehne, B.

A physically-based modeling of the air-sea gas transfer that can be used to predict the gas transfer rates with sufficient accuracy as a function of micrometeorological parameters is still lacking. State of the art are still simple gas transfer rate/wind speed relationships. Previous measurements from Coastal Ocean Experiment in the Atlantic revealed positive correlations between mean square slope, near surface turbulent dis- sipation, and wind stress. It also demonstrated a strong negative correlation between mean square slope and the fluorescence of surface-enriched colored dissolved organic matter. Using heat as a proxy tracer for gases the exchange process at the air/water interface and the micro turbulence at the water surface can be investigated. The anal- ysis of infrared image sequences allow the determination of the net heat flux at the ocean surface, the temperature gradient across the air/sea interface and thus the heat transfer velocity and gas transfer velocity respectively. Laboratory studies were carried out in the new Heidelberg wind-wave facility AELOTRON. Direct measurements of the Schmidt number exponent were done in conjunction with classical mass balance methods to estimate the transfer velocity. The laboratory results allowed to validate the basic assumptions of the so called controlled flux technique by applying differ- ent tracers for the gas exchange in a large Schmidt number regime. Thus a modeling of the Schmidt number exponent is able to fill the gap between laboratory and field measurements field. Both, the results from the laboratory and the field measurements should be able to give a further understanding of the mechanisms controlling the trans- port processes across the aqueous boundary layer and to relate the forcing functions to parameters measured by remote sensing.

A two-scale scattering model with application to the JONSWAP '75 aircraft microwave scatterometer experiment

NASA Technical Reports Server (NTRS)

Wentz, F. J.

1977-01-01

The general problem of bistatic scattering from a two scale surface was evaluated. The treatment was entirely two-dimensional and in a vector formulation independent of any particular coordinate system. The two scale scattering model was then applied to backscattering from the sea surface. In particular, the model was used in conjunction with the JONSWAP 1975 aircraft scatterometer measurements to determine the sea surface's two scale roughness distributions, namely the probability density of the large scale surface slope and the capillary wavenumber spectrum. Best fits yield, on the average, a 0.7 dB rms difference between the model computations and the vertical polarization measurements of the normalized radar cross section. Correlations between the distribution parameters and the wind speed were established from linear, least squares regressions.

Remote sensing the sea surface CO2 of the Baltic Sea using the SOMLO methodology

NASA Astrophysics Data System (ADS)

Parard, G.; Charantonis, A. A.; Rutgerson, A.

2015-06-01

Studies of coastal seas in Europe have noted the high variability of the CO2 system. This high variability, generated by the complex mechanisms driving the CO2 fluxes, complicates the accurate estimation of these mechanisms. This is particularly pronounced in the Baltic Sea, where the mechanisms driving the fluxes have not been characterized in as much detail as in the open oceans. In addition, the joint availability of in situ measurements of CO2 and of sea-surface satellite data is limited in the area. In this paper, we used the SOMLO (self-organizing multiple linear output; Sasse et al., 2013) methodology, which combines two existing methods (i.e. self-organizing maps and multiple linear regression) to estimate the ocean surface partial pressure of CO2 (pCO2) in the Baltic Sea from the remotely sensed sea surface temperature, chlorophyll, coloured dissolved organic matter, net primary production, and mixed-layer depth. The outputs of this research have a horizontal resolution of 4 km and cover the 1998-2011 period. These outputs give a monthly map of the Baltic Sea at a very fine spatial resolution. The reconstructed pCO2 values over the validation data set have a correlation of 0.93 with the in situ measurements and a root mean square error of 36 μatm. Removing any of the satellite parameters degraded this reconstructed CO2 flux, so we chose to supply any missing data using statistical imputation. The pCO2 maps produced using this method also provide a confidence level of the reconstruction at each grid point. The results obtained are encouraging given the sparsity of available data, and we expect to be able to produce even more accurate reconstructions in coming years, given the predicted acquisition of new data.

Reconstructing past sea ice cover of the Northern Hemisphere from dinocyst assemblages: status of the approach

NASA Astrophysics Data System (ADS)

de Vernal, Anne; Rochon, André; Fréchette, Bianca; Henry, Maryse; Radi, Taoufik; Solignac, Sandrine

2013-11-01

Dinocysts occur in a wide range of environmental conditions, including polar areas. We review here their use for the reconstruction of paleo sea ice cover in such environments. In the Arctic Ocean and subarctic seas characterized by dense sea ice cover, Islandinium minutum, Islandinium? cezare, Echinidinium karaense, Polykrikos sp. var. Arctic, Spiniferites elongatus-frigidus and Impagidinium pallidum are common and often occur with more cosmopolitan taxa such as Operculodinium centrocarpum sensu Wall & Dale, cyst of Pentapharsodinium dalei and Brigantedinium spp. Canonical correspondence analyses conducted on dinocyst assemblages illustrate relationships with sea surface parameters such as salinity, temperature, and sea ice cover. The application of the modern analogue technique permits quantitative reconstruction of past sea ice cover, which is expressed in terms of seasonal extent of sea ice cover (months per year with more than 50% of sea ice concentration) or mean annual sea ice concentration (in tenths). The accuracy of reconstructions or root mean square error of prediction (RMSEP) is ±1.1 over 10, which corresponds to perennial sea ice. Such an error is close to the interannual variability (standard deviation) of observed sea ice cover. Mismatch between the time interval of instrumental data used as reference (1953-2000) and the time interval represented by dinocyst populations in surface sediment samples, which may cover decades if not centuries, is another source of error. Despite uncertainties, dinocyst assemblages are useful for making quantitative reconstruction of seasonal sea ice cover.

Dimethylsulfide model calibration and parametric sensitivity analysis for the Greenland Sea

NASA Astrophysics Data System (ADS)

Qu, Bo; Gabric, Albert J.; Zeng, Meifang; Xi, Jiaojiao; Jiang, Limei; Zhao, Li

2017-09-01

Sea-to-air fluxes of marine biogenic aerosols have the potential to modify cloud microphysics and regional radiative budgets, and thus moderate Earth's warming. Polar regions play a critical role in the evolution of global climate. In this work, we use a well-established biogeochemical model to simulate the DMS flux from the Greenland Sea (20°W-10°E and 70°N-80°N) for the period 2003-2004. Parameter sensitivity analysis is employed to identify the most sensitive parameters in the model. A genetic algorithm (GA) technique is used for DMS model parameter calibration. Data from phase 5 of the Coupled Model Intercomparison Project (CMIP5) are used to drive the DMS model under 4 × CO2 conditions. DMS flux under quadrupled CO2 levels increases more than 300% compared with late 20th century levels (1 × CO2). Reasons for the increase in DMS flux include changes in the ocean state-namely an increase in sea surface temperature (SST) and loss of sea ice-and an increase in DMS transfer velocity, especially in spring and summer. Such a large increase in DMS flux could slow the rate of warming in the Arctic via radiative budget changes associated with DMS-derived aerosols.

Key parameters of the sediment surface morphodynamics in an estuary - An assessment of model solutions

NASA Astrophysics Data System (ADS)

Sampath, D. M. R.; Boski, T.

2018-05-01

Large-scale geomorphological evolution of an estuarine system was simulated by means of a hybrid estuarine sedimentation model (HESM) applied to the Guadiana Estuary, in Southwest Iberia. The model simulates the decadal-scale morphodynamics of the system under environmental forcing, using a set of analytical solutions to simplified equations of tidal wave propagation in shallow waters, constrained by empirical knowledge of estuarine sedimentary dynamics and topography. The key controlling parameters of the model are bed friction (f), current velocity power of the erosion rate function (N), and sea-level rise rate. An assessment of sensitivity of the simulated sediment surface elevation (SSE) change to these controlling parameters was performed. The model predicted the spatial differentiation of accretion and erosion, the latter especially marked in the mudflats within mean sea level and low tide level and accretion was mainly in a subtidal channel. The average SSE change mutually depended on both the friction coefficient and power of the current velocity. Analysis of the average annual SSE change suggests that the state of intertidal and subtidal compartments of the estuarine system vary differently according to the dominant processes (erosion and accretion). As the Guadiana estuarine system shows dominant erosional behaviour in the context of sea-level rise and sediment supply reduction after the closure of the Alqueva Dam, the most plausible sets of parameter values for the Guadiana Estuary are N = 1.8 and f = 0.8f0, or N = 2 and f = f0, where f0 is the empirically estimated value. For these sets of parameter values, the relative errors in SSE change did not exceed ±20% in 73% of simulation cells in the studied area. Such a limit of accuracy can be acceptable for an idealized modelling of coastal evolution in response to uncertain sea-level rise scenarios in the context of reduced sediment supply due to flow regulation. Therefore, the idealized but cost-effective HESM model will be suitable for estimating the morphological impacts of sea-level rise on estuarine systems on a decadal timescale.

The role of sea surface circulation and hydrographic processes in anchovy spawning and larvae distribution in the Strait of Sicily (Central Mediterranean).

NASA Astrophysics Data System (ADS)

Falcini, Federico; Palatella, Luigi; Cuttitta, Angela; Bignami, Francesco; Patti, Bernardo; Santoleri, Rosalia; Fiorentino, Fabio

2014-05-01

The European Anchovy (Engraulis encrasicolus, Linnaeus, 1758) is one of the most important resources of the Mediterranean Sea. Despite its abundance and relevance, the anchovy population off the Mediterranean coasts exhibits a patchy distribution. Moreover, its biology and the influence of environment on its variability is poorly known. We here use data from ichthyoplankton-surveys carried out during the peak spawning season in order to analyze abundance and age of anchovy larvae in the Strait of Sicily, with respect to sea surface dynamic and hydrographic parameter patterns. The Strait of Sicily dynamics is characterized by upwelling regions, fronts, vortices, and filaments, with a consequent complexity in the spatial distribution of oceanographic parameters and anchovy larvae. To investigate the role of mesoscale features and oceanographic environment on the latter, anchovy larvae observations were paired to remote sensing data (such as sea surface temperature, chlorophyll, primary production, surface wind speed as well as light attenuation, absorption, and particle backscattering coefficients) and Lagrangian and Eulerian numerical simulations results for ocean currents and larval transport. The subsequent analysis shows and quantifies how the Atlantic Ionian Stream (AIS, a meandering current of Atlantic origin) path and variability, as well as the upwelling-induced south Sicilian coastal current, have consequences for anchovy spawning and larvae distribution. These currents transport anchovy larvae towards the Sicilian coast's south-eastern tip, where larvae are then retained in a frontal structure. However, significant cross-shore transport events due to relatively cold filament-like baroclinic instabilities generated by wind-induced coastal upwelling were also observed. Finally, the larval age distribution qualitatively agrees well with this transport pattern.

Extratropical Influence of Sea Surface Temperature and Wind on Water Recycling Rate Over Oceans and Coastal Lands

NASA Technical Reports Server (NTRS)

Hu, Hua; Liu, W. Timothy

1999-01-01

Water vapor and precipitation are two important parameters confining the hydrological cycle in the atmosphere and over the ocean surface. In the extratropical areas, due to variations of midlatitude storm tracks and subtropical jetstreams, water vapor and precipitation have large variability. Recently, a concept of water recycling rate defined previously by Chahine et al. (GEWEX NEWS, August, 1997) has drawn increasing attention. The recycling rate of moisture is calculated as the ratio of precipitation to total precipitable water (its inverse is the water residence time). In this paper, using multi-sensor spacebased measurements we will study the role of sea surface temperature and ocean surface wind in determining the water recycling rate over oceans and coastal lands. Response of water recycling rate in midlatitudes to the El Nino event will also be discussed. Sea surface temperature data are derived from satellite observations from the Advanced Very High Resolution Radiometer (AVHRR) blended with in situ measurements, available for the period 1982-1998. Global sea surface wind observations are obtained from spaceborne scatterometers aboard on the European Remote-Sensing Satellite (ERS1 and 2), available for the period 1991-1998. Global total precipitable water provided by the NASA Water Vapor Project (NVAP) is available for the period 1988-1995. Global monthly mean precipitation provided by the Global Precipitation Climatology Project (GPCP) is available for the period 1987-1998.

Satellite-derived ice data sets no. 2: Arctic monthly average microwave brightness temperatures and sea ice concentrations, 1973-1976

NASA Technical Reports Server (NTRS)

Parkinson, C. L.; Comiso, J. C.; Zwally, H. J.

1987-01-01

A summary data set for four years (mid 70's) of Arctic sea ice conditions is available on magnetic tape. The data include monthly and yearly averaged Nimbus 5 electrically scanning microwave radiometer (ESMR) brightness temperatures, an ice concentration parameter derived from the brightness temperatures, monthly climatological surface air temperatures, and monthly climatological sea level pressures. All data matrices are applied to 293 by 293 grids that cover a polar stereographic map enclosing the 50 deg N latitude circle. The grid size varies from about 32 X 32 km at the poles to about 28 X 28 km at 50 deg N. The ice concentration parameter is calculated assuming that the field of view contains only open water and first-year ice with an ice emissivity of 0.92. To account for the presence of multiyear ice, a nomogram is provided relating the ice concentration parameter, the total ice concentration, and the fraction of the ice cover which is multiyear ice.

Metagenomic covariation along densely sampled environmental gradients in the Red Sea

PubMed Central

Thompson, Luke R; Williams, Gareth J; Haroon, Mohamed F; Shibl, Ahmed; Larsen, Peter; Shorenstein, Joshua; Knight, Rob; Stingl, Ulrich

2017-01-01

Oceanic microbial diversity covaries with physicochemical parameters. Temperature, for example, explains approximately half of global variation in surface taxonomic abundance. It is unknown, however, whether covariation patterns hold over narrower parameter gradients and spatial scales, and extending to mesopelagic depths. We collected and sequenced 45 epipelagic and mesopelagic microbial metagenomes on a meridional transect through the eastern Red Sea. We asked which environmental parameters explain the most variation in relative abundances of taxonomic groups, gene ortholog groups, and pathways—at a spatial scale of <2000 km, along narrow but well-defined latitudinal and depth-dependent gradients. We also asked how microbes are adapted to gradients and extremes in irradiance, temperature, salinity, and nutrients, examining the responses of individual gene ortholog groups to these parameters. Functional and taxonomic metrics were equally well explained (75–79%) by environmental parameters. However, only functional and not taxonomic covariation patterns were conserved when comparing with an intruding water mass with different physicochemical properties. Temperature explained the most variation in each metric, followed by nitrate, chlorophyll, phosphate, and salinity. That nitrate explained more variation than phosphate suggested nitrogen limitation, consistent with low surface N:P ratios. Covariation of gene ortholog groups with environmental parameters revealed patterns of functional adaptation to the challenging Red Sea environment: high irradiance, temperature, salinity, and low nutrients. Nutrient-acquisition gene ortholog groups were anti-correlated with concentrations of their respective nutrient species, recapturing trends previously observed across much larger distances and environmental gradients. This dataset of metagenomic covariation along densely sampled environmental gradients includes online data exploration supplements, serving as a community resource for marine microbial ecology. PMID:27420030

Emperor penguins and climate change.

PubMed

Barbraud, C; Weimerskirch, H

2001-05-10

Variations in ocean-atmosphere coupling over time in the Southern Ocean have dominant effects on sea-ice extent and ecosystem structure, but the ultimate consequences of such environmental changes for large marine predators cannot be accurately predicted because of the absence of long-term data series on key demographic parameters. Here, we use the longest time series available on demographic parameters of an Antarctic large predator breeding on fast ice and relying on food resources from the Southern Ocean. We show that over the past 50 years, the population of emperor penguins (Aptenodytes forsteri) in Terre Adélie has declined by 50% because of a decrease in adult survival during the late 1970s. At this time there was a prolonged abnormally warm period with reduced sea-ice extent. Mortality rates increased when warm sea-surface temperatures occurred in the foraging area and when annual sea-ice extent was reduced, and were higher for males than for females. In contrast with survival, emperor penguins hatched fewer eggs when winter sea-ice was extended. These results indicate strong and contrasting effects of large-scale oceanographic processes and sea-ice extent on the demography of emperor penguins, and their potential high susceptibility to climate change.

Application of MIMO Techniques in sky-surface wave hybrid networking sea-state radar system

NASA Astrophysics Data System (ADS)

Zhang, L.; Wu, X.; Yue, X.; Liu, J.; Li, C.

2016-12-01

The sky-surface wave hybrid networking sea-state radar system contains of the sky wave transmission stations at different sites and several surface wave radar stations. The subject comes from the national 863 High-tech Project of China. The hybrid sky-surface wave system and the HF surface wave system work simultaneously and the HF surface wave radar (HFSWR) can work in multi-static and surface-wave networking mode. Compared with the single mode radar system, this system has advantages of better detection performance at the far ranges in ocean dynamics parameters inversion. We have applied multiple-input multiple-output(MIMO) techniques in this sea-state radar system. Based on the multiple channel and non-causal transmit beam-forming techniques, the MIMO radar architecture can reduce the size of the receiving antennas and simplify antenna installation. Besides, by efficiently utilizing the system's available degrees of freedom, it can provide a feasible approach for mitigating multipath effect and Doppler-spread clutter in Over-the-horizon Radar. In this radar, slow-time phase-coded MIMO method is used. The transmitting waveforms are phase-coded in slow-time so as to be orthogonal after Doppler processing at the receiver. So the MIMO method can be easily implemented without the need to modify the receiver hardware. After the radar system design, the MIMO experiments of this system have been completed by Wuhan University during 2015 and 2016. The experiment used Wuhan multi-channel ionospheric sounding system(WMISS) as sky-wave transmitting source and three dual-frequency HFSWR developed by the Oceanography Laboratory of Wuhan University. The transmitter system located at Chongyang with five element linear equi-spaced antenna array and Wuhan with one log-periodic antenna. The RF signals are generated by synchronized, but independent digital waveform generators - providing complete flexibility in element phase and amplitude control, and waveform type and parameters. The field experimental results show the presented method is effective. The echoes are obvious and distinguishable both in co-located MIMO mode and widely distributed MIMO mode. Key words: sky-surface wave hybrid networking; sea-state radar; MIMO; phase-coded

Surface and atmosphere parameter maps from earth-orbiting radiometers

NASA Technical Reports Server (NTRS)

Gloersen, P.

1976-01-01

Earlier studies have shown that an earth-orbiting electrically scanned microwave radiometer (ESMR) is capable of inferring the extent, concentration, and age of sea ice; the extent, concentration, and thickness of lake ice; rainfall rates over oceans; surface wind speeds over open water; particle size distribution in the deep snow cover of continental ice sheets; and soil moisture content in unvegetated fields. Most other features of the surface of the earth and its atmosphere require multispectral imaging techniques to unscramble the combined contributions of the atmosphere and the surface. Multispectral extraction of surface parameters is analyzed on the basis of a pertinent equation in terms of the observed brightness temperature, the emissivity of the surface which depends on wavelength and various parameters, the sensible temperature of the surface, and the total atmospheric opacity which is also wavelength dependent. Implementation of the multispectral technique is examined. Properties of the surface of the earth and its atmosphere to be determined from a scanning multichannel microwave radiometer are tabulated.

Ocean acidification state in western Antarctic surface waters: drivers and interannual variability

NASA Astrophysics Data System (ADS)

Mattsdotter Björk, M.; Fransson, A.; Chierici, M.

2013-05-01

Each December during four years from 2006 to 2010, the surface water carbonate system was measured and investigated in the Amundsen Sea and Ross Sea, western Antarctica as part of the Oden Southern Ocean expeditions (OSO). The I/B Oden started in Punta Arenas in Chile and sailed southwest, passing through different regimes such as, the marginal/seasonal ice zone, fronts, coastal shelves, and polynyas. Discrete surface water was sampled underway for analysis of total alkalinity (AT), total dissolved inorganic carbon (CT) and pH. Two of these parameters were used together with sea-surface temperature (SST), and salinity to obtain a full description of the surface water carbonate system, including pH in situ and calcium carbonate saturation state of aragonite (ΩAr) and calcite (ΩCa). Multivariate analysis was used to investigate interannual variability and the major controls (sea-ice concentration, SST, salinity and chlorophyll a) on the variability in the carbonate system and Ω. This analysis showed that SST and chlorophyll a were the major drivers of the Ω variability in both the Amundsen and Ross seas. In 2007, the sea-ice edge was located further south and the area of the open polynya was relatively small compared to 2010. We found the lowest pH in situ (7.932) and Ω = 1 values in the sea-ice zone and in the coastal Amundsen Sea, nearby marine out flowing glaciers. In 2010, the sea-ice coverage was the largest and the areas of the open polynyas were the largest for the whole period. This year we found the lowest salinity and AT, coinciding with highest chl a. This implies that the highest ΩAr in 2010 was likely an effect of biological CO2 drawdown, which out-competed the dilution of carbonate ion concentration due to large melt water volumes. We predict and discuss future Ω values, using our data and reported rates of oceanic uptake of anthropogenic CO2, suggesting that the Amundsen Sea will become undersaturated with regard to aragonite about 20 yr sooner than predicted by models.

Calibration of sea ice dynamic parameters in an ocean-sea ice model using an ensemble Kalman filter

NASA Astrophysics Data System (ADS)

Massonnet, F.; Goosse, H.; Fichefet, T.; Counillon, F.

2014-07-01

The choice of parameter values is crucial in the course of sea ice model development, since parameters largely affect the modeled mean sea ice state. Manual tuning of parameters will soon become impractical, as sea ice models will likely include more parameters to calibrate, leading to an exponential increase of the number of possible combinations to test. Objective and automatic methods for parameter calibration are thus progressively called on to replace the traditional heuristic, "trial-and-error" recipes. Here a method for calibration of parameters based on the ensemble Kalman filter is implemented, tested and validated in the ocean-sea ice model NEMO-LIM3. Three dynamic parameters are calibrated: the ice strength parameter P*, the ocean-sea ice drag parameter Cw, and the atmosphere-sea ice drag parameter Ca. In twin, perfect-model experiments, the default parameter values are retrieved within 1 year of simulation. Using 2007-2012 real sea ice drift data, the calibration of the ice strength parameter P* and the oceanic drag parameter Cw improves clearly the Arctic sea ice drift properties. It is found that the estimation of the atmospheric drag Ca is not necessary if P* and Cw are already estimated. The large reduction in the sea ice speed bias with calibrated parameters comes with a slight overestimation of the winter sea ice areal export through Fram Strait and a slight improvement in the sea ice thickness distribution. Overall, the estimation of parameters with the ensemble Kalman filter represents an encouraging alternative to manual tuning for ocean-sea ice models.

Vertical spatial coherence model for a transient signal forward-scattered from the sea surface

USGS Publications Warehouse

Yoerger, E.J.; McDaniel, S.T.

1996-01-01

The treatment of acoustic energy forward scattered from the sea surface, which is modeled as a random communications scatter channel, is the basis for developing an expression for the time-dependent coherence function across a vertical receiving array. The derivation of this model uses linear filter theory applied to the Fresnel-corrected Kirchhoff approximation in obtaining an equation for the covariance function for the forward-scattered problem. The resulting formulation is used to study the dependence of the covariance on experimental and environmental factors. The modeled coherence functions are then formed for various geometrical and environmental parameters and compared to experimental data.

A first course in optimum design of yacht sails

NASA Astrophysics Data System (ADS)

Sugimoto, Takeshi

1993-03-01

The optimum sail geometry is analytically obtained for the case of maximizing the thrust under equality and inequality constraints on the lift and the heeling moment. A single mainsail is assumed to be set close-hauled in uniform wind and upright on the flat sea surface. The governing parameters are the mast height and the gap between the sail foot and the sea surface. The lifting line theory is applied to analyze the aerodynamic forces acting on a sail. The design method consists of the variational principle and a feasibility study. Almost triangular sails are found to be optimum. Their advantages are discussed.

A network model for characterizing brine channels in sea ice

NASA Astrophysics Data System (ADS)

Lieblappen, Ross M.; Kumar, Deip D.; Pauls, Scott D.; Obbard, Rachel W.

2018-03-01

The brine pore space in sea ice can form complex connected structures whose geometry is critical in the governance of important physical transport processes between the ocean, sea ice, and surface. Recent advances in three-dimensional imaging using X-ray micro-computed tomography have enabled the visualization and quantification of the brine network morphology and variability. Using imaging of first-year sea ice samples at in situ temperatures, we create a new mathematical network model to characterize the topology and connectivity of the brine channels. This model provides a statistical framework where we can characterize the pore networks via two parameters, depth and temperature, for use in dynamical sea ice models. Our approach advances the quantification of brine connectivity in sea ice, which can help investigations of bulk physical properties, such as fluid permeability, that are key in both global and regional sea ice models.

Arctic melt ponds and bifurcations in the climate system

NASA Astrophysics Data System (ADS)

Sudakov, I.; Vakulenko, S. A.; Golden, K. M.

2015-05-01

Understanding how sea ice melts is critical to climate projections. In the Arctic, melt ponds that develop on the surface of sea ice floes during the late spring and summer largely determine their albedo - a key parameter in climate modeling. Here we explore the possibility of a conceptual sea ice climate model passing through a bifurcation point - an irreversible critical threshold as the system warms, by incorporating geometric information about melt pond evolution. This study is based on a bifurcation analysis of the energy balance climate model with ice-albedo feedback as the key mechanism driving the system to bifurcation points.

The Hygroscopicity Parameter of Marine Organics in Sea Spray Aerosols

NASA Astrophysics Data System (ADS)

Boyer, M.; Chang, R. Y. W.

2015-12-01

The effects of aerosols on climate are poorly understood, specifically with respect to their influence on cloud properties. Since oceans cover >70% of Earth's surface, sea spray aerosols (SSA), which act efficiently as cloud condensation nuclei (CCN), may have important implications on Earth's radiation budget. Surface active organic species readily accumulate in the sea surface microlayer (SML), located at the ocean-atmosphere interface, and transfer onto nascent SSA. While it is understood that SSA are commonly enriched with organics, the resulting effect of the organic content on CCN activation remains unresolved. The hygroscopicity parameter, kappa (k), allows for the cloud nucleating properties of individual components to be predicted in particles of mixed composition; however, most studies typically infer k from ambient measurements without assessing the contribution of the individual components to the overall k. In this study, a method for quantifying the cloud nucleating properties of the organic species in surface seawater using k-Kohler theory is proposed. Ambient SML and bulk water samples will be collected and atomized to generate particles such that the overall k can be inferred from CCN measurements. The inorganic and organic components will be quantified, and the organic component will be separated so that the hygroscopicity of only the organic constituents can be determined. By comparing the inferred k values for the samples before and after removal of the inorganic component, the hygroscopicity of the organic constituents alone can be calculated, providing insight on the effect of organic species on CCN activation in SSA.

Sensitivity of open-water ice growth and ice concentration evolution in a coupled atmosphere-ocean-sea ice model

NASA Astrophysics Data System (ADS)

Shi, Xiaoxu; Lohmann, Gerrit

2017-09-01

A coupled atmosphere-ocean-sea ice model is applied to investigate to what degree the area-thickness distribution of new ice formed in open water affects the ice and ocean properties. Two sensitivity experiments are performed which modify the horizontal-to-vertical aspect ratio of open-water ice growth. The resulting changes in the Arctic sea-ice concentration strongly affect the surface albedo, the ocean heat release to the atmosphere, and the sea-ice production. The changes are further amplified through a positive feedback mechanism among the Arctic sea ice, the Atlantic Meridional Overturning Circulation (AMOC), and the surface air temperature in the Arctic, as the Fram Strait sea ice import influences the freshwater budget in the North Atlantic Ocean. Anomalies in sea-ice transport lead to changes in sea surface properties of the North Atlantic and the strength of AMOC. For the Southern Ocean, the most pronounced change is a warming along the Antarctic Circumpolar Current (ACC), owing to the interhemispheric bipolar seasaw linked to AMOC weakening. Another insight of this study lies on the improvement of our climate model. The ocean component FESOM is a newly developed ocean-sea ice model with an unstructured mesh and multi-resolution. We find that the subpolar sea-ice boundary in the Northern Hemisphere can be improved by tuning the process of open-water ice growth, which strongly influences the sea ice concentration in the marginal ice zone, the North Atlantic circulation, salinity and Arctic sea ice volume. Since the distribution of new ice on open water relies on many uncertain parameters and the knowledge of the detailed processes is currently too crude, it is a challenge to implement the processes realistically into models. Based on our sensitivity experiments, we conclude a pronounced uncertainty related to open-water sea ice growth which could significantly affect the climate system sensitivity.

Satellite Data Sets in the Polar Regions

NASA Technical Reports Server (NTRS)

Comiso, Josefino C.; Busalacchi, Antonio J. (Technical Monitor)

2000-01-01

We have generated about two decades of consistently derived geophysical parameters in the polar regions. The key parameters are sea ice concentration, surface temperature, albedo, and cloud cover statistics. Sea ice concentrations were derived from the Scanning Multichannel Microwave Radiometer (SMMR) data and the Special Scanning Cl Microwave Imager (SSM/I) data from several platforms using the enhanced Bootstrap Algorithm for the period 1978 through 1999. The new algorithm reduces the errors associated with spatial and temporal variations in the emissivity and surface temperatures of sea ice. Also, bad data at ocean/land interfaces are identified and deleted in an unsupervised manner. Surface ice temperature, albedo and cloud cover statistics are derived simultaneously from the Advanced Very High Resolution Radiometer (AVHRR) data from 1981 through 1999 and mapped at a higher resolution but the same format as the ice concentration data. The technique makes use these co-registered ice concentration maps to enable cloud masking to be done separately for open ocean, sea ice and land areas. The effect of inversion is minimized by taking into consideration the expected changes in the effect of inversion with altitude, especially in the Antarctic. A technique for ice type regional classification has also been developed using multichannel cluster analysis and a neural network. This provide a means to identify large areas of thin ice, first year ice, and older ice types. The data sets have been shown to be coherent with each other and provide a powerful tool for in depth studies of the currently changing Arctic and Antarctic environment.

Temporal and Spatial Variability of the Ras Al-Hadd Jet/Front in the Northwest Arabian Sea

NASA Astrophysics Data System (ADS)

Al Shaqsi, Hilal Mohamed Said

Thirteen years of 1.1 km resolution daily satellites remote sensing sea surface temperature datasets (2002-2014), sea surface winds, sea surface height, Argo floats, daily three-hour interval wind datasets, and hourly records of oceanography physical parameters from mooring current meters were processed and analyzed to investigate the dynamics, temporal and spatial variability of the Ras Al-Hadd Jet off the northwest Arabian Sea. Cayula and Cornillon single image edge detection algorithm was used to detect these thermal fronts. The Ras Al-Hadd thermal front was found to have two seasonal peaks. The first peak occurred during the intensified southwest monsoon period (July/August), while the second peak was clearly observed during the transitional period or the Post-Southwest monsoon (September-October). Interannual and intraseasonal variability showed the occurrence of the Ras Al-Hadd thermal fronts in the northwest Arabian Sea. The southwest monsoon winds, the Somalia Current, the East Arabian Current, and the warmer high salinity waters from the Sea of Oman are the main factors influencing the creation of the Ras Al-Hadd Jet. Based on direct observations, current velocity in the Cape Ras Al-Hadd Jet exceeded 120 cms-1, and the wind speed was over 12 ms-1 during the southwest monsoon seasons. The mean width and the mean length of the Jet were approximately 40 km and 260 km, respectively. Neither the winter monsoon, nor the Pre-Southwest monsoon seasons showed signs of the Ras Al-Hadd Jet or fronts in the northwest Arabian Sea.

Reconstruction from EOF analysis of SMOS salinity data in Mediterranean Sea

NASA Astrophysics Data System (ADS)

Parard, Gaelle; Alvera-Azcárate, Aida; Barth, Alexander; Olmedo, Estrella; Turiel, Antonio; Becker, Jean-Marie

2017-04-01

Sea Surface Salinity (SSS) data from the Soil Moisture and Ocean Salinity (SMOS) mission is reconstructed in the North Atlantic and the Mediterranean Sea using DINEOF (Data Interpolating Empirical Orthogonal Functions). We used the satellite data Level 2 from SMOS Barcelona Expert Centre between 2011 and 2015. DINEOF is a technique that reconstructs missing data and removes noise by retaining only an optimal set of EOFs. DINEOF analysis is used to detect and remove outliers from the SMOS SSS daily field. The gain obtained with DINEOF method and L2 SMOS data give a higher spatial and temporal resolution between 2011 and 2015, allow to study the SSS variability from daily to seasonal resolution. In order to improve the SMOS salinity data reconstruction we combine with other parameters measured from satellite such chlorophyll, sea surface temperature, precipitation and CDOM variability. After a validation of the SMOS satellite data reconstruction with in situ data (CTD, Argo float salinity measurement) in the North Atlantic and Mediterranean Sea, the main SSS processes and their variability are studied. The gain obtained with the higher spatial and temporal resolution with SMOS salinity data give assess to study the characteristics of oceanic structures in North Atlantic and Mediterranean Sea.

Area Estimation of Deep-Sea Surfaces from Oblique Still Images

PubMed Central

Souto, Miguel; Afonso, Andreia; Calado, António; Madureira, Pedro; Campos, Aldino

2015-01-01

Estimating the area of seabed surfaces from pictures or videos is an important problem in seafloor surveys. This task is complex to achieve with moving platforms such as submersibles, towed or remotely operated vehicles (ROV), where the recording camera is typically not static and provides an oblique view of the seafloor. A new method for obtaining seabed surface area estimates is presented here, using the classical set up of two laser devices fixed to the ROV frame projecting two parallel lines over the seabed. By combining lengths measured directly from the image containing the laser lines, the area of seabed surfaces is estimated, as well as the camera’s distance to the seabed, pan and tilt angles. The only parameters required are the distance between the parallel laser lines and the camera’s horizontal and vertical angles of view. The method was validated with a controlled in situ experiment using a deep-sea ROV, yielding an area estimate error of 1.5%. Further applications and generalizations of the method are discussed, with emphasis on deep-sea applications. PMID:26177287

Effects of High Hydrostatic Pressure on Coastal Bacterial Community Abundance and Diversity

PubMed Central

Marietou, Angeliki

2014-01-01

Hydrostatic pressure is an important parameter influencing the distribution of microbial life in the ocean. In this study, the response of marine bacterial populations from surface waters to pressures representative of those under deep-sea conditions was examined. Southern California coastal seawater collected 5 m below the sea surface was incubated in microcosms, using a range of temperatures (16 to 3°C) and hydrostatic pressure conditions (0.1 to 80 MPa). Cell abundance decreased in response to pressure, while diversity increased. The morphology of the community also changed with pressurization to a predominant morphotype of small cocci. The pressure-induced community changes included an increase in the relative abundance of Alphaproteobacteria, Gammaproteobacteria, Actinobacteria, and Flavobacteria largely at the expense of Epsilonproteobacteria. Culturable high-pressure-surviving bacteria were obtained and found to be phylogenetically similar to isolates from cold and/or deep-sea environments. These results provide novel insights into the response of surface water bacteria to changes in hydrostatic pressure. PMID:25063663

Inversion Schemes to Retrieve Atmospheric and Oceanic Parameters from SeaWiFS Data

NASA Technical Reports Server (NTRS)

Deschamps, P.-Y.; Frouin, R.

1997-01-01

The investigation focuses on two key issues in satellite ocean color remote sensing, namely the presence of whitecaps on the sea surface and the validity of the aerosol models selected for the atmospheric correction of SeaWiFS data. Experiments were designed and conducted at the Scripps Institution of Oceanography to measure the optical properties of whitecaps and to study the aerosol optical properties in a typical mid-latitude coastal environment. CIMEL Electronique sunphotometers, now integrated in the AERONET network, were also deployed permanently in Bermuda and in Lanai, calibration/validation sites for SeaWiFS and MODIS. Original results were obtained on the spectral reflectance of whitecaps and on the choice of aerosol models for atmospheric correction schemes and the type of measurements that should be made to verify those schemes. Bio-optical algorithms to remotely sense primary productivity from space were also evaluated, as well as current algorithms to estimate PAR at the earth's surface.

The deeper structure of the southern Dead Sea basin derived from neural network analysis of velocity and attenuation tomography

NASA Astrophysics Data System (ADS)

Braeuer, Benjamin; Haberland, Christian; Bauer, Klaus; Weber, Michael

2014-05-01

The Dead Sea basin is a pull-apart basin at the Dead Sea transform fault, the boundary between the African and the Arabian plates. Though the DSB has been studied for a long time, the available knowledge - based mainly on surface geology, drilling and seismic reflection surveys - gives only a partial picture of its shallow structure. Therefore, within the framework of the international DESIRE (DEad Sea Integrated REsearch) project, a dense temporary local seismological network was operated in the southern Dead Sea area. Within 18 month of recording 650 events were detected. In addition to an already published tomography study revealing the distribution of P velocities and the Vp/Vs ratios a 2D P-wave attenuation tomography (parameter Qp) was performed. The neural network technique of Self-organizing maps (SOM) is used for the joint interpretation of these three parameters (Vp, Vp/Vs, Qp). The resulting clusters in the petrophysical parameter space are assigned to the main lithological units below the southern part of the Dead Sea basin: (1) The basin sediments characterized by strong attenuation, high vp/vs ratios and low P velocities. (2) The pre-basin sediments characterized by medium to strong attenuation, low Vp/Vs ratios and medium P velocities. (3) The basement characterized by low to moderate attenuation, medium vp/vs ratios and high P velocities. Thus, the asymmetric southern Dead Sea basin is filled with basin sediments down to depth of 7 to 12 km. Below the basin sediments, the pre-basin sediments are extending to a depth between 13 and 18 km.

Underwater sky image as remote sensing instrument of sea roughness parameters and its variability

NASA Astrophysics Data System (ADS)

Molkov, Alexander A.; Dolin, Lev S.; Kapustin, Ivan A.; Sergievskaya, Irina A.; Shomina, Olga V.

2016-10-01

At present a sufficient amount of methods is offered for determining the characteristics of sea roughness in accordance with optical images of wavy water surface obtained from different near-shore constructions, sea platforms, vessels, aircraft and satellites. The most informative elements in this case are solar path and peripheral areas of the image free from sun glitters. However, underwater images of the surface obtained with the help of optical receiver located at a certain depth contain apart from the mentioned elements one more informative element- Snell's window. It is an underwater sky image which distortions of border contain information on roughness characteristics and serve as the indicator of its variability. The research offers the method for determining energy spectra of wind waves in accordance with the second statistical moment of Snell's window image. The results of testing of the offered method are provided based on natural images registered in the course of trip to the Black Sea under conditions of different wind and wave environment for clear surface and surface covered by surfactant films. For both cases frequency spectra of surface slopes are recovered and their good coincidence to the spectra received by processing of signals from a string wave recorder is established. Efficiency of application of the offered method for tasks of remote monitoring and environmental control of natural reservoirs is shown.

Variability of three-dimensional sea breeze structure in southern France: observations and evaluation of empirical scaling laws

NASA Astrophysics Data System (ADS)

Drobinski, P.; Bastin, S.; Dabas, A.; Delville, P.; Reitebuch, O.

2006-08-01

Sea-breeze dynamics in southern France is investigated using an airborne Doppler lidar, a meteorological surface station network and radiosoundings, in the framework of the ESCOMPTE experiment conducted during summer 2001 in order to evaluate the role of thermal circulations on pollutant transport and ventilation. The airborne Doppler lidar WIND contributed to three-dimensional (3-D) mapping of the sea breeze circulation in an unprecedented way. The data allow access to the onshore and offshore sea breeze extents (xsb), and to the sea breeze depth (zsb) and intensity (usb). They also show that the return flow of the sea breeze circulation is very seldom seen in this area due to (i) the presence of a systematic non zero background wind, and (ii) the 3-D structure of the sea breeze caused by the complex coastline shape and topography. A thorough analysis is conducted on the impact of the two main valleys (Rhône and Durance valleys) affecting the sea breeze circulation in the area.

Finally, this dataset also allows an evaluation of the existing scaling laws used to derive the sea breeze intensity, depth and horizontal extent. The main results of this study are that (i) latitude, cumulative heating and surface friction are key parameters of the sea breeze dynamics; (ii) in presence of strong synoptic flow, all scaling laws fail in predicting the sea breeze characteristics (the sea breeze depth, however being the most accurately predicted); and (iii) the ratio zsb/usb is approximately constant in the sea breeze flow.

Biogeography of dinoflagellate cysts in northwest Atlantic ...

EPA Pesticide Factsheets

Few biogeographic studies of dinoflagellate cysts include the near-shore estuarine environment. We determine the effect of estuary type, biogeography, and water quality on the spatial distribution of organic-walled dinoflagellate cysts from the Northeast USA (Maine to Delaware) and Canada (Prince Edward Island). A total of 69 surface sediment samples were collected from 27 estuaries, from sites with surface salinities >20. Dinoflagellate cysts were examined microscopically and compared to environmental parameters using multivariate ordination techniques. The spatial distribution of cyst taxa reflects biogeographic provinces established by other marine organisms, with Cape Cod separating the northern Acadian Province from the southern Virginian Province. Species such as Lingulodinium machaerophorum and Polysphaeridinium zoharyi were found almost exclusively in the Virginian Province, while others such as Dubridinium spp. and Islandinium? cezare were more abundant in the Acadian Province. Tidal range, sea surface temperature (SST), and sea surface salinity (SSS) are statistically significant parameters influencing cyst assemblages. Samples from the same type of estuary cluster together in canonical correspondence analysis when the estuaries are within the same biogeographic province. The large geographic extent of this study, encompassing four main estuary types (riverine, lagoon, coastal embayment, and fjord), allowed us to determine that the type of estuary has

Extreme storm surge modelling in the North Sea. The role of the sea state, forcing frequency and spatial forcing resolution

NASA Astrophysics Data System (ADS)

Ridder, Nina; de Vries, Hylke; Drijfhout, Sybren; van den Brink, Henk; van Meijgaard, Erik; de Vries, Hans

2018-02-01

This study shows that storm surge model performance in the North Sea is mostly unaffected by the application of temporal variations of surface drag due to changes in sea state provided the choice of a suitable constant Charnock parameter in the sea-state-independent case. Including essential meteorological features on smaller scales and minimising interpolation errors by increasing forcing data resolution are shown to be more important for the improvement of model performance particularly at the high tail of the probability distribution. This is found in a modelling study using WAQUA/DCSMv5 by evaluating the influence of a realistic air-sea momentum transfer parameterization and comparing it to the influence of changes in the spatial and temporal resolution of the applied forcing fields in an effort to support the improvement of impact and climate analysis studies. Particular attention is given to the representation of extreme water levels over the past decades based on the example of the Netherlands. For this, WAQUA/DCSMv5 is forced with ERA-Interim reanalysis data. Model results are obtained from a set of different forcing fields, which either (i) include a wave-state-dependent Charnock parameter or (ii) apply a constant Charnock parameter ( α C h = 0.032) tuned for young sea states in the North Sea, but differ in their spatial and/or temporal resolution. Increasing forcing field resolution from roughly 79 to 12 km through dynamically downscaling can reduce the modelled low bias, depending on coastal station, by up to 0.25 m for the modelled extreme water levels with a 1-year return period and between 0.1 m and 0.5 m for extreme surge heights.

The Thermocline Layer and Chlorophyll-a Concentration Variability during Southeast Monsoon in the Banda Sea

NASA Astrophysics Data System (ADS)

Pusparini, Nikita; Prasetyo, Budi; Ambariyanto; Widowati, Ita

2017-02-01

Thermocline layer and chlorophyll-a concentration can be used to investigate the upwelling region. This investigation is focused in the Banda Sea because the upwelling event in this area is quite large and has a longer upwelling duration than other waters in Indonesia. In addition, Banda Sea is also influenced by climatic factors such as monsoon. The aim of this research is to determine the validation of secondary data (from satellite imagery data and model) and in situ observation data (from research cruise) and to determine the variability of thermocline layer and chlorophyll-a concentration during Southeast Monsoon in the Banda Sea. The data used in this study were chlorophyll-a concentration, seawater vertical temperature at depths 0-400 meters, and sea surface temperature from remote sensing and in situ data. Spatial and temporal analysis of all parameters was conducted by quantitative descriptive method. The results showed that the variability of thermocline layer and the chlorophyll-a distribution were strongly related to seasonal pattern. In most cases, the estimates of thermocline layer and chlorophyll-a concentration using remote sensing algorithm were higher than in situ measured values. The greatest variability occurred in the eastern Banda Sea during the Southeast Monsoon with shallower thermocline layer, more abundance of chlorophyll-a concentration, and lower sea surface temperature.

Evaluating coastal sea surface heights based on a novel sub-waveform approach using sparse representation and conditional random fields

NASA Astrophysics Data System (ADS)

Uebbing, Bernd; Roscher, Ribana; Kusche, Jürgen

2016-04-01

Satellite radar altimeters allow global monitoring of mean sea level changes over the last two decades. However, coastal regions are less well observed due to influences on the returned signal energy by land located inside the altimeter footprint. The altimeter emits a radar pulse, which is reflected at the nadir-surface and measures the two-way travel time, as well as the returned energy as a function of time, resulting in a return waveform. Over the open ocean the waveform shape corresponds to a theoretical model which can be used to infer information on range corrections, significant wave height or wind speed. However, in coastal areas the shape of the waveform is significantly influenced by return signals from land, located in the altimeter footprint, leading to peaks which tend to bias the estimated parameters. Recently, several approaches dealing with this problem have been published, including utilizing only parts of the waveform (sub-waveforms), estimating the parameters in two steps or estimating additional peak parameters. We present a new approach in estimating sub-waveforms using conditional random fields (CRF) based on spatio-temporal waveform information. The CRF piece-wise approximates the measured waveforms based on a pre-derived dictionary of theoretical waveforms for various combinations of the geophysical parameters; neighboring range gates are likely to be assigned to the same underlying sub-waveform model. Depending on the choice of hyperparameters in the CRF estimation, the classification into sub-waveforms can either be more fine or coarse resulting in multiple sub-waveform hypotheses. After the sub-waveforms have been detected, existing retracking algorithms can be applied to derive water heights or other desired geophysical parameters from particular sub-waveforms. To identify the optimal heights from the multiple hypotheses, instead of utilizing a known reference height, we apply a Dijkstra-algorithm to find the "shortest path" of all possible heights. We apply our approach to Jason-2 data in different coastal areas, such as the Bangladesh coast or in the North Sea and compare our sea surface heights to various existing retrackers. Using the sub-waveform approach, we are able to derive meaningful water heights up to a few kilometers off the coast, where conventional retrackers, such as the standard ocean retracker, no longer provide useful data.

Retrieve sea surface salinity using principal component regression model based on SMOS satellite data

NASA Astrophysics Data System (ADS)

Zhao, Hong; Li, Changjun; Li, Hongping; Lv, Kebo; Zhao, Qinghui

2016-06-01

The sea surface salinity (SSS) is a key parameter in monitoring ocean states. Observing SSS can promote the understanding of global water cycle. This paper provides a new approach for retrieving sea surface salinity from Soil Moisture and Ocean Salinity (SMOS) satellite data. Based on the principal component regression (PCR) model, SSS can also be retrieved from the brightness temperature data of SMOS L2 measurements and Auxiliary data. 26 pair matchup data is used in model validation for the South China Sea (in the area of 4°-25°N, 105°-125°E). The RMSE value of PCR model retrieved SSS reaches 0.37 psu (practical salinity units) and the RMSE of SMOS SSS1 is 1.65 psu when compared with in-situ SSS. The corresponding Argo daily salinity data during April to June 2013 is also used in our validation with RMSE value 0.46 psu compared to 1.82 psu for daily averaged SMOS L2 products. This indicates that the PCR model is valid and may provide us with a good approach for retrieving SSS from SMOS satellite data.

The Algorithm Theoretical Basis Document for the Derivation of Range and Range Distributions from Laser Pulse Waveform Analysis for Surface Elevations, Roughness, Slope, and Vegetation Heights

NASA Technical Reports Server (NTRS)

Brenner, Anita C.; Zwally, H. Jay; Bentley, Charles R.; Csatho, Bea M.; Harding, David J.; Hofton, Michelle A.; Minster, Jean-Bernard; Roberts, LeeAnne; Saba, Jack L.; Thomas, Robert H.;

Comparison of the ocean surface vector winds over the Nordic Seas and their application for ocean modeling

NASA Astrophysics Data System (ADS)

Dukhovskoy, Dmitry; Bourassa, Mark

2017-04-01

Ocean processes in the Nordic Seas and northern North Atlantic are strongly controlled by air-sea heat and momentum fluxes. The predominantly cyclonic, large-scale atmospheric circulation brings the deep ocean layer up to the surface preconditioning the convective sites in the Nordic Seas for deep convection. In winter, intensive cooling and possibly salt flux from newly formed sea ice erodes the near-surface stratification and the mixed layer merges with the deeper domed layer, exposing the very weakly stratified deep water mass to direct interaction with the atmosphere. Surface wind is one of the atmospheric parameters required for estimating momentum and turbulent heat fluxes to the sea ice and ocean surface. In the ocean models forced by atmospheric analysis, errors in surface wind fields result in errors in air-sea heat and momentum fluxes, water mass formation, ocean circulation, as well as volume and heat transport in the straits. The goal of the study is to assess discrepancies across the wind vector fields from reanalysis data sets and scatterometer-derived gridded products over the Nordic Seas and northern North Atlantic and to demonstrate possible implications of these differences for ocean modeling. The analyzed data sets include the reanalysis data from the National Center for Environmental Prediction Reanalysis 2 (NCEPR2), Climate Forecast System Reanalysis (CFSR), Arctic System Reanalysis (ASR) and satellite wind products Cross-Calibrated Multi-Platform (CCMP) wind product version 1.1 and recently released version 2.0, and Remote Sensing Systems QuikSCAT data. Large-scale and mesoscale characteristics of winds are compared at interannual, seasonal, and synoptic timescales. Numerical sensitivity experiments are conducted with a coupled ice-ocean model forced by different wind fields. The sensitivity experiments demonstrate differences in the net surface heat fluxes during storm events. Next, it is hypothesized that discrepancies in the wind vorticity fields should manifest different behaviors of the isopycnals in the Nordic Seas. Time evolution of isopycnal depths in the sensitivity experiments forced by different wind fields is discussed. Results of these sensitivity experiments demonstrate a relationship between the isopycnal surfaces and the wind stress curl. The numerical experiments are also analyzed to investigate the relationship between the East Greenland Current and the wind stress curl over the Nordic Seas. The transport of the current at this location has substantial contribution from wind-driven large-scale circulation. This wind-driven part of the East Greenland Current is a western-intensified return flow of a wind-driven cyclonic gyre in the central Nordic Seas. The numerical experiments with different wind fields reveal notable sensitivity of the East Greenland Current to differences in the wind forcing.

Developments in Earth observation for the assessment and monitoring of inland, transitional, coastal and shelf-sea waters.

PubMed

Tyler, Andrew N; Hunter, Peter D; Spyrakos, Evangelos; Groom, Steve; Constantinescu, Adriana Maria; Kitchen, Jonathan

2016-12-01

The Earth's surface waters are a fundamental resource and encompass a broad range of ecosystems that are core to global biogeochemical cycling and food and energy production. Despite this, the Earth's surface waters are impacted by multiple natural and anthropogenic pressures and drivers of environmental change. The complex interaction between physical, chemical and biological processes in surface waters poses significant challenges for in situ monitoring and assessment and often limits our ability to adequately capture the dynamics of aquatic systems and our understanding of their status, functioning and response to pressures. Here we explore the opportunities that Earth observation (EO) has to offer to basin-scale monitoring of water quality over the surface water continuum comprising inland, transition and coastal water bodies, with a particular focus on the Danube and Black Sea region. This review summarises the technological advances in EO and the opportunities that the next generation satellites offer for water quality monitoring. We provide an overview of algorithms for the retrieval of water quality parameters and demonstrate how such models have been used for the assessment and monitoring of inland, transitional, coastal and shelf-sea systems. Further, we argue that very few studies have investigated the connectivity between these systems especially in large river-sea systems such as the Danube-Black Sea. Subsequently, we describe current capability in operational processing of archive and near real-time satellite data. We conclude that while the operational use of satellites for the assessment and monitoring of surface waters is still developing for inland and coastal waters and more work is required on the development and validation of remote sensing algorithms for these optically complex waters, the potential that these data streams offer for developing an improved, potentially paradigm-shifting understanding of physical and biogeochemical processes across large scale river-sea systems including the Danube-Black Sea is considerable. Copyright © 2016. Published by Elsevier B.V.

Process evaluation of sea salt aerosol concentrations at remote marine locations

NASA Astrophysics Data System (ADS)

Struthers, H.; Ekman, A. M.; Nilsson, E. D.

2011-12-01

Sea salt, an important natural aerosol, is generated by bubbles bursting at the surface of the ocean. Sea salt aerosol contributes significantly to the global aerosol burden and radiative budget and are a significant source of cloud condensation nuclei in remote marine areas (Monahan et al., 1986). Consequently, changes in marine aerosol abundance is expected to impact on climate forcing. Estimates of the atmospheric burden of sea salt aerosol mass derived from chemical transport and global climate models vary greatly both in the global total and the spatial distribution (Texor et al. 2006). This large uncertainty in the sea salt aerosol distribution in turn contributes to the large uncertainty in the current estimates of anthropogenic aerosol climate forcing (IPCC, 2007). To correctly attribute anthropogenic climate change and to veraciously project future climate, natural aerosols including sea salt must be understood and accurately modelled. In addition, the physical processes that determine the sea salt aerosol concentration are susceptible to modification due to climate change (Carslaw et al., 2010) which means there is the potential for feedbacks within the climate/aerosol system. Given the large uncertainties in sea salt aerosol modelling, there is an urgent need to evaluate the process description of sea salt aerosols in global models. An extremely valuable source of data for model evaluation is the long term measurements of PM10 sea salt aerosol mass available from a number of remote marine observation sites around the globe (including the GAW network). Sea salt aerosol concentrations at remote marine locations depend strongly on the surface exchange (emission and deposition) as well as entrainment or detrainment to the free troposphere. This suggests that the key parameters to consider in any analysis include the sea surface water temperature, wind speed, precipitation rate and the atmospheric stability. In this study, the sea salt aerosol observations are analysed to quantify the key sensitivities of the processes connecting the physical drivers of sea salt aerosol to the mass tendency. The analysis employs a semi-empirical model based on the time-tendency of the aerosol mass. This approach of focusing on the time-tendency of the sea salt aerosol concentration provides a framework for the process evaluation of sea salt aerosol concentrations in global models. The same analysis methodology can be applied to output from global models. A process of comparing the sensitivity parameters derived from observations and models will reveal model inadequacies and thus guide model improvements. Carslaw, K. S., Boucher, O., Spracklen, D. V., Mann G. W., Rae, J. G. L, Woodward, S., Kulmala, M. (2010). Atmos. Chem. Phys., 10, 1701-1737 IPCC (2007). Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Solomon, S., D. Monahan, E. C., Spiel, D. E., Davidson, K. L. (1986) Oceanic Whitecaps ed. Monahan E. C. & MacNiochaill, D. Reidel, Norwell, Mass. Texor, C., et al. (2006) Atmos. Chem. Phys., 6, 1777-1813.

Optimization of subcritical water extraction parameters of antioxidant polyphenols from sea buckthorn (Hippophaë rhamnoides L.) seed residue.

PubMed

Gong, Ying; Zhang, Xiaofei; He, Li; Yan, Qiuli; Yuan, Fang; Gao, Yanxiang

2015-03-01

Polyphenols was extracted with subcritical water from the sea buckthorn seed residue (after oil recovery), and the extraction parameters were optimized using response surface methodology (RSM). The independent processing variables were extraction temperature, extraction time and the ratio of water to solid. The optimal extraction parameters for the extracts with highest ABTS radical scavenging activity were 120 °C, 36 min and the water to solid ratio of 20, and the maximize antioxidant capacity value was 32.42 mmol Trolox equivalent (TE)/100 g. Under the optimal conditions, the yield of total phenolics, total flavonoids and proanthocyanidins was 36.62 mg gallic acid equivalents (GAE)/g, 19.98 mg rutin equivalent (RE)/g and 10.76 mg catechin equivalents (CE)/g, respectively.

Oceanographic, Air-sea Interaction, and Environmental Aspects of Artificial Upwelling Produced by Wave-Inertia Pumps for Potential Hurricane Intensity Mitigation

NASA Astrophysics Data System (ADS)

Soloviev, A.; Dean, C.

2017-12-01

The artificial upwelling system consisting of the wave-inertia pumps driven by surface waves can produce flow of cold deep water to the surface. One of the recently proposed potential applications of the artificial upwelling system is the hurricane intensity mitigation. Even relatively small reduction of intensity may provide significant benefits. The ocean heat content (OHC) is the "fuel" for hurricanes. The OHC can be reduced by mixing of the surface layer with the cold water produced by wave-inertia pumps. Implementation of this system for hurricane mitigation has several oceanographic and air-sea interaction aspects. The cold water brought to the surface from a deeper layer has higher density than the surface water and, therefore, tends to sink back down. The mixing of the cold water produced by artificial upwelling depends on environmental conditions such as stratification, regional ocean circulation, and vertical shear. Another aspect is that as the sea surface temperature drops below the air temperature, the stable stratification develops in the atmospheric boundary layer. The stable atmospheric stratification suppresses sensible and latent heat air-sea fluxes and reduces the net longwave irradiance from the sea surface. As a result, the artificial upwelling may start increasing the OHC (though still reducing the sea surface temperature). In this work, the fate of the cold water in the stratified environment with vertical shear has been studied using computational fluid dynamics (CFD) tools. A 3D large eddy simulation model is initialized with observational temperature, salinity, and current velocity data from a sample location in the Straits of Florida. A periodic boundary condition is set along the direction of the current, which allows us to simulate infinite fetch. The model results indicate that the cold water brought to the sea surface by a wave-inertia pump forms a convective jet. This jet plunges into the upper ocean mixed layer and penetrates the thermocline. On the way down, the jet partially mixes with the surrounding water reducing the temperature of the upper ocean. The OHC thus can either reduce or increase, depending on the wave-inertia pump parameters. Based on the model results, we discuss feasibility of the implementation of the artificial upwelling system for hurricane intensity mitigation.

Derive Arctic Sea-ice Freeboard and Thickness from NASA's LVIS Observations

NASA Astrophysics Data System (ADS)

Yi, D.; Hofton, M. A.; Harbeck, J.; Cornejo, H.; Kurtz, N. T.

2015-12-01

The sea-ice freeboard and thickness are derived from the six sea-ice flights of NASA's IceBridge Land, Vegetation, and Ice Sensor (LVIS) over the Arctic from 2009 to 2013. The LVIS is an airborne scanning laser altimeter. It can operate at an altitude up to 10 km above the ground and produce a data swath up to 2 km wide with 20-m wide footprints. The laser output wavelength is 1064 nm and pulse repetition rate is 1000 Hz. The LVIS L2 geolocated surface elevation product and Level-1b waveform product (http://nsidc.org/data/ilvis2.html and http://nsidc.org/data/ilvis1b.html) at National Snow and Ice Data Center, USA (NSIDC) are used in this study. The elevations are referenced to a geoid with tides and dynamic atmospheric corrections applied. The LVIS waveforms were fitted with Gaussian curves to calculate pulse width, peak location, pulse amplitude, and signal baseline. For each waveform, the centroid, skewness, kurtosis, and pulse area were also calculated. The waveform parameters were calibrated based on laser off pointing angle and laser channels. Calibrated LVIS waveform parameters show a coherent response to variations in surface features along their ground tracks. These parameters, combined with elevation, can be used to identify leads, enabling the derivation of sea-ice freeboard and thickness without relying upon visual images. Preliminary results show that the elevations in some of the LVIS campaigns may vary with laser incident angle; this can introduce an elevation bias if not corrected. Further analysis of the LVIS data shown that the laser incident angle related elevation bias can be removed empirically. The sea-ice freeboard and thickness results from LVIS are compared with NASA's Airborne Topographic Mapper (ATM) for an April 20, 2010 flight, when both LVIS and ATM sensors were on the same aircraft and made coincidental measurements along repeat ground tracks.

Polarimetric Signatures of Sea Ice. Part 1; Theoretical Model

NASA Technical Reports Server (NTRS)

Nghiem, S. V.; Kwok, R.; Yueh, S. H.; Drinkwater, M. R.

1995-01-01

Physical, structural, and electromagnetic properties and interrelating processes in sea ice are used to develop a composite model for polarimetric backscattering signatures of sea ice. Physical properties of sea ice constituents such as ice, brine, air, and salt are presented in terms of their effects on electromagnetic wave interactions. Sea ice structure and geometry of scatterers are related to wave propagation, attenuation, and scattering. Temperature and salinity, which are determining factors for the thermodynamic phase distribution in sea ice, are consistently used to derive both effective permittivities and polarimetric scattering coefficients. Polarimetric signatures of sea ice depend on crystal sizes and brine volumes, which are affected by ice growth rates. Desalination by brine expulsion, drainage, or other mechanisms modifies wave penetration and scattering. Sea ice signatures are further complicated by surface conditions such as rough interfaces, hummocks, snow cover, brine skim, or slush layer. Based on the same set of geophysical parameters characterizing sea ice, a composite model is developed to calculate effective permittivities and backscattering covariance matrices at microwave frequencies for interpretation of sea ice polarimetric signatures.

Atmospheric model development in support of SEASAT. Volume 2: Analysis models

NASA Technical Reports Server (NTRS)

Langland, R. A.

1977-01-01

As part of the SEASAT program of NASA, two sets of analysis programs were developed for the Jet Propulsion Laboratory. One set of programs produce 63 x 63 horizontal mesh analyses on a polar stereographic grid. The other set produces 187 x 187 third mesh analyses. The parameters analyzed include sea surface temperature, sea level pressure and twelve levels of upper air temperature, height and wind analyses. The analysis output is used to initialize the primitive equation forecast models.

An investigation of the observability of ocean-surface parameters using GEOS-3 backscatter data

NASA Technical Reports Server (NTRS)

Miller, L. S.; Priester, R. W.

1978-01-01

The degree to which ocean surface roughness can be synoptically observed through use of the information extracted from the GEOS-3 backscattered waveform data was evaluated. Algorithms are given for use in estimating the radar sensed waveheight distribution or ocean-surface impulse response. Other factors discussed include comparisons between theoretical and experimental radar cross section values, sea state bias effects, spatial variability of significant waveheight data, and sensor-related considerations.

Sea-level and solid-Earth deformation feedbacks in ice sheet modelling

NASA Astrophysics Data System (ADS)

Konrad, Hannes; Sasgen, Ingo; Klemann, Volker; Thoma, Malte; Grosfeld, Klaus; Martinec, Zdeněk

2014-05-01

The interactions of ice sheets with the sea level and the solid Earth are important factors for the stability of the ice shelves and the tributary inland ice (e.g. Thomas and Bentley, 1978; Gomez et al, 2012). First, changes in ice extent and ice thickness induce viscoelastic deformation of the Earth surface and Earth's gravity field. In turn, global and local changes in sea level and bathymetry affect the grounding line and, subsequently, alter the ice dynamic behaviour. Here, we investigate these feedbacks for a synthetic ice sheet configuration as well as for the Antarctic ice sheet using a three-dimensional thermomechanical ice sheet and shelf model, coupled to a viscoelastic solid-Earth and gravitationally self-consistent sea-level model. The respective ice sheet undergoes a forcing from rising sea level, warming ocean, and/or changing surface mass balance. The coupling is realized by exchanging ice thickness, Earth surface deformation and sea level periodically. We apply several sets of viscoelastic Earth parameters to our coupled model, e.g. simulating a low-viscous upper mantle present at the Antarctic Peninsula (Ivins et al., 2011). Special focus of our study lies on the evolution of Earth surface deformation and local sea level changes, as well as on the accompanying grounding line evolution. N. Gomez, D. Pollard, J. X. Mitrovica, P. Huybers, and P. U. Clark 2012. Evolution of a coupled marine ice sheet-sea level model, J. Geophys. Res., 117, F01013, doi:10.1029/2011JF002128. E. R. Ivins, M. M. Watkins, D.-N. Yuan, R. Dietrich, G. Casassa, and A. Rülke 2011. On-land ice loss and glacial isostatic adjustment at the Drake Passage: 2003-2009, J. Geophys. Res. 116, B02403, doi: 10.1029/2010JB007607 R. H. Thomas and C. R. Bentley 1978. A model for Holocene retreat of the West Antarctic Ice Sheet, Quaternary Research, 10 (2), pages 150-170, doi: 10.1016/0033-5894(78)90098-4.

Field Observations of Coastal Air-Sea Interaction

NASA Astrophysics Data System (ADS)

Ortiz-Suslow, D. G.; Haus, B. K.; Williams, N. J.; Graber, H. C.

2016-12-01

In the nearshore zone wind, waves, and currents generated from different forcing mechanisms converge in shallow water. This can profoundly affect the physical nature of the ocean surface, which can significantly modulate the exchange of momentum, heat, and mass across the air-sea interface. For decades, the focus of air-sea interaction research has been on the open ocean while the shallow water regime has been relatively under-explored. This bears implications for efforts to understand and model various coastal processes, such as mixing, surface transport, and air-sea gas flux. The results from a recent study conducted at the New River Inlet in North Carolina showed that directly measured air-sea flux parameters, such as the atmospheric drag coefficient, are strong functions of space as well as the ambient conditions (i.e. wind speed and direction). The drag is typically used to parameterize the wind stress magnitude. It is generally assumed that the wind direction is the direction of the atmospheric forcing (i.e. wind stress), however significant wind stress steering off of the azimuthal wind direction was observed and was found to be related to the horizontal surface current shear. The authors have just returned from a field campaign carried out within Monterey Bay in California. Surface observations made from two research vessels were complimented by an array of beach and inland flux stations, high-resolution wind forecasts, and satellite image acquisitions. This is a rich data set and several case studies will be analyzed to highlight the importance of various processes for understanding the air-sea fluxes. Preliminary findings show that interactions between the local wind-sea and the shoaling, incident swell can have a profound effect on the wind stress magnitude. The Monterey Bay coastline contains a variety of topographical features and the importance of land-air-sea interactions will also be investigated.

Validation of Cloud Optical Parameters from Passive Remote Sensing in the Arctic by using the Aircraft Measurements

NASA Astrophysics Data System (ADS)

Chen, H.; Schmidt, S.; Coddington, O.; Wind, G.; Bucholtz, A.; Segal-Rosenhaimer, M.; LeBlanc, S. E.

2017-12-01

Cloud Optical Parameters (COPs: e.g., cloud optical thickness and cloud effective radius) and surface albedo are the most important inputs for determining the Cloud Radiative Effect (CRE) at the surface. In the Arctic, the COPs derived from passive remote sensing such as from the Moderate Resolution Imaging Spectroradiometer (MODIS) are difficult to obtain with adequate accuracy owing mainly to insufficient knowledge about the snow/ice surface, but also because of the low solar zenith angle. This study aims to validate COPs derived from passive remote sensing in the Arctic by using aircraft measurements collected during two field campaigns based in Fairbanks, Alaska. During both experiments, ARCTAS (Arctic Research of the Composition of the Troposphere from Aircraft and Satellites) and ARISE (Arctic Radiation-IceBridge Sea and Ice Experiment), the Solar Spectral Flux Radiometer (SSFR) measured upwelling and downwelling shortwave spectral irradiances, which can be used to derive surface and cloud albedo, as well as the irradiance transmitted by clouds. We assess the variability of the Arctic sea ice/snow surfaces albedo through these aircraft measurements and incorporate this variability into cloud retrievals for SSFR. We then compare COPs as derived from SSFR and MODIS for all suitable aircraft underpasses of the satellites. Finally, the sensitivities of the COPs to surface albedo and solar zenith angle are investigated.

Ocean colour remote sensing in the southern Laptev Sea: evaluation and applications

NASA Astrophysics Data System (ADS)

Heim, B.; Abramova, E.; Doerffer, R.; Günther, F.; Hölemann, J.; Kraberg, A.; Lantuit, H.; Loginova, A.; Martynov, F.; Overduin, P. P.; Wegner, C.

2014-08-01

Enhanced permafrost warming and increased Arctic river discharges have heightened concern about the input of terrigenous matter into Arctic coastal waters. We used optical operational satellite data from the ocean colour sensor MERIS (Medium-Resolution Imaging Spectrometer) aboard the ENVISAT satellite mission for synoptic monitoring of the pathways of terrigenous matter on the shallow Laptev Sea shelf. Despite the high cloud coverage in summer that is inherent to this Arctic region, time series from MERIS satellite data from 2006 on to 2011 could be acquired and were processed using the Case-2 Regional Processor (C2R) for optically complex surface waters installed in the open-source software ESA BEAM-VISAT. Since optical remote sensing using ocean colour satellite data has seen little application in Siberian Arctic coastal and shelf waters, we assess the applicability of the calculated MERIS C2R parameters with surface water sampling data from the Russian-German ship expeditions LENA2008, LENA2010 and TRANSDRIFT-XVII taking place in August 2008 and August and September 2010 in the southern Laptev Sea. The shallow Siberian shelf waters are optically not comparable to the deeper, more transparent waters of the Arctic Ocean. The inner-shelf waters are characterized by low transparencies, due to turbid river water input, terrestrial input by coastal erosion, resuspension events and, therefore, high background concentrations of suspended particulate matter and coloured dissolved organic matter. We compared the field-based measurements with the satellite data that are closest in time. The match-up analyses related to LENA2008 and LENA2010 expedition data show the technical limits of matching in optically highly heterogeneous and dynamic shallow inner-shelf waters. The match-up analyses using the data from the marine TRANSDRIFT expedition were constrained by several days' difference between a match-up pair of satellite-derived and in situ parameters but are also based on the more stable hydrodynamic conditions of the deeper inner- and the outer-shelf waters. The relationship of satellite-derived turbidity-related parameters versus in situ suspended matter from TRANSDRIFT data shows that the backscattering coefficient C2R_bb_spm can be used to derive a Laptev-Sea-adapted SPM algorithm. Satellite-derived Chl a estimates are highly overestimated by a minimum factor of 10 if applied to the inner-shelf region due to elevated concentrations of terrestrial organic matter. To evaluate the applicability of ocean colour remote sensing, we include the visual analysis of lateral hydrographical features. The mapped turbidity-related MERIS C2R parameters show that the Laptev Sea is dominated by resuspension above submarine shallow banks and by frontal instabilities such as frontal meanders with amplitudes up to 30 km and eddies and filaments with horizontal scales up to 100 km that prevail throughout the sea-ice-free season. The widespread turbidity above submarine shallow banks indicates inner-shelf vertical mixing that seems frequently to reach down to submarine depths of a minimum of 10 m. The resuspension events and the frontal meanders, filaments and eddies indicate enhanced vertical mixing being widespread on the inner shelf. It is a new finding for the Laptev Sea that numerous frontal instabilities are made visible, and how highly time-dependent and turbulent the Laptev Sea shelf is. The meanders, filaments and eddies revealed by the ocean colour parameters indicate the lateral transportation pathways of terrestrial and living biological material in surface waters.

The Sulu Sea as Carbon Dioxide Sink

NASA Astrophysics Data System (ADS)

Ferrera, C. M.; Jacinto, G. S.; Chen, C. T. A.

2016-12-01

The Sulu Sea, one of the marginal seas in the West Pacific and the largest internal sea in the Philippines, is characterized by its unique deep water ventilation pattern and high sediment organic carbon and CaCO3 content. Studies on the dissolved CO2 system in the Sulu Sea have remarkably shown that anthropogenic CO2 has already penetrated to the bottom of this 5km-deep basin, albeit limited to a dataset from a single station in December 1996. To further understand the role of this tropical marginal sea as CO2 sink and to assess its behavior as a CO2 sink during the 11-year period, water samples for dissolved CO2 parameters from two deep stations of high productivity and low productivity were collected in December 2007/January 2008 and were compared with the 1996 data. Results suggest that the surface waters in the low productivity region might have been acidifying at a rate of -0.0012 pH unit yr-1. Atmospheric CO2 increased at +1.9 ppmv yr-1 and seawater fCO2 at +3.30 μatm yr-1. Through deep water ventilation, anthropogenic CO2 has penetrated the water column thereby making the deeper waters a sink of anthropogenic CO2. But then the presence and dissolution of CaCO3 deposits at the sea floor and along the Sulu Sea slopes as a result of the reaction with this anthropogenic CO2 probably neutralizes the acidification at depths as shown by the increase in total alkalinity (+0.57 μmol kg-1 yr-1), and facilitates further uptake of CO2 from the atmosphere. Therefore, productivity at Sulu Sea surface waters results to sequestration of CO2 from the atmosphere to the sediment sink through organic carbon and CaCO3 deposits. While high temperature and low productivity surface waters make the Sulu Sea a source of CO2 to the atmosphere, ventilation patterns make the deep waters of the Sulu Sea an efficient sink for anthropogenic CO2. Given the larger area occupied by the CO2 sink deep waters compared to the CO2 source surface waters including an upwelling area, the Sulu Sea could possibly be a "net" CO2 sink, an important contribution to the otherwise underestimated inventory of CO2 from marginal seas.

Land-Sea-Atmosphere Interaction and Their Association with Drought Conditions

NASA Astrophysics Data System (ADS)

Singh, R. P.; Nath, A.

2017-12-01

Detailed analysis of satellite data for the period 2002-2016 provides an understanding of the land-sea interaction and its association with the vegetation conditions over the Indian continent. The Indian Ocean dipole (IOD) phenomenon is also considered to understand the atmospheric dynamics and meteorological parameters. GPS water vapor and meteorological parameters (relative humidity and water vapor) from the Indian Institute of Science (IISC) Bangalore have been considered for meteorological data for the period 2008-2016. Atmospheric parameters (water vapor, precipitation rate, land temperature, total ozone column) have been considered using through NASA Giovanni portal and GPS water vapor through SoumiNet data to study relation between Sea Surface temperature (SST) from Indian Ocean, Bay of Bengal and Arabian Sea. Our detailed analysis shows that SST has strong impact on the NDVI at different locations, the maximum impact of SST is observed at lower latitudes. The NDVI over the central and northern India (Indo-Gangetic plains (IGP) is not affected. The SST and NDVI shows high correlation in the central and northern parts, whereas the correlation is poor in the southern parts i.e. close to the ocean. The detailed analysis of NDVI data provides progression of the drought conditions especially in the southern parts of India and also shows impact of the El Nino during 2015-2016.

On the use of QuikSCAT data for assessing wind energy resources

NASA Astrophysics Data System (ADS)

Karagali, I.; Peña, A.; Hahmann, A. N.; Hasager, C.; Badger, M.

2011-12-01

As the land space suitable for wind turbine installations becomes saturated, the focus is on offshore sites. Advantages of such a transition include increased power production, smaller environmental and social impact and extended availability of prospective areas. Until recently installation of wind turbines was limited in coastal areas. Nowadays, the search for suitable sites is extended beyond shallow waters, in locations far offshore where available measurements of various environmental parameters are limited. Space-borne observations are ideal due to their global spatial coverage, providing information where in-situ measurements are impracticable. The most widely used satellite observations for wind vector information are obtained by scatterometers; active radars that relate radiation backscattered from the sea surface to wind. SeaWinds, the scatterometer on board the QuikSCAT platform, launched by NASA in 1999 provided information with global coverage until 2009. The potential use of this 10-year long dataset is evaluated in the present study for the characterization of wind resources in the North and Baltic Seas, where most of Europe's offshore wind farms are located. Long-term QuikSCAT data have been extensively and positively validated in open ocean and in enclosed seas. In the present study QuikSCAT rain-free observations are compared with in-situ observations from three locations in the North Sea. As the remotely sensed observations refer to neutral atmospheric stratification, the impact of stability is assessed. Mean wind characteristics along with the Weibull A and k parameters are estimated in order to obtain information regarding the variation of wind. The numerical weather prediction (NWP) model WRF (Weather Research & Forecasting) is used for comparisons against QuikSCAT. Surface winds derived from long-term WRF simulations are compared against QuikSCAT data to evaluate differences in the spatial extend. Preliminary results indicate very good agreement between satellite and in-situ observations. The mean annual wind speed at 10 meters above the sea surface is found significantly higher in the North Sea when compared to the Baltic Sea. Strong lee effects on the 10m wind speeds are observed, in particular the reduced wind speed on the east side of the British Isles as opposed to the west coast of Denmark. An intense flow channelling in the English Channel and the Baltic Sea is highlighted, along with various other effects. Comparisons between WRF and QuikSCAT show biases in the order of 0.4 m/s or lower in extended spatial scales. Higher negative biases, indicating higher QuikSCAT wind speed than the WRF-derived, are observed mainly in coastal areas where representativeness errors due to surface roughness changes are significant.

Basic research and data analysis for the earth and ocean physics applications program and for the National Geodetic Satellite program

NASA Technical Reports Server (NTRS)

1975-01-01

Data acquisition using single image and seven image data processing is used to provide a precise and accurate geometric description of the earth's surface. Transformation parameters and network distortions are determined, Sea slope along the continental boundaries of the U.S. and earth rotation are examined, along with close grid geodynamic satellite system. Data are derived for a mathematical description of the earth's gravitational field; time variations are determined for geometry of the ocean surface, the solid earth, gravity field, and other geophysical parameters.

Decadal increase in seagrass biomass and temperature at the CARICOMP site in Bocas del Toro, Panama.

PubMed

López-Calderón, Jorge M; Guzmán, Hector M; Jácome, Gabriel E; Barnes, Penélope A G

2013-12-01

The Caribbean Coastal Marine Productivity Program (CARICOMP) was launched in 1993 to study regional long-term interactions between land and sea, taking standardized measurements of productivity and biomass of mangroves, coral reefs and seagrasses. Since 1999 continuous measurements of seagrass (Thalassia testudinum) parameters as well as environmental data have been recorded in Caribbean Panama. Replicate stations were selected near the Smithsonian Tropical Research Institute in Bocas del Toro. Sediment cores and quadrants were placed there to estimate biomass and productivity, respectively. Mean values for productivity, standing crop, turnover rate, total dry biomass, and Leaf Area Index were 1.74 gDW/m2/d, 66.6 gDW/m2, 2.62%/d, 1481 gDW/m2, and 4.65, respectively. Total dry biomass (shoots, rhizomes and roots) and LAI of T. testudinum increased significantly during the study period. Mean values for total rainfall, Secchi disk depth, sea surface temperature, and salinity were 3498 mm, 8.24 m, 28.79 degrees C, and 32.26 psu, respectively. Sea surface temperature was the only environmental variable with a statistically significant change, increasing from 1999 to 2010. Correlation between sea surface temperature and 7 testudinum parameters (total biomass and LAI) were both positive and significant. Human population has increased dramatically over the last ten years in Bocas del Toro region, increasing pressure (deforestation, runoff, wastewater) over coastal ecosystems (seagrasses, mangroves, coral reefs). Change in the abundance of 7 testudinum may be linked to ocean warming, as a consequence to satisfy plant's metabolic requirements, although other local factors need to be analyzed (reduced grazing and increased eutrophication). A further warming of the ocean could have a negative effect on T. testudinum population, increasing respiratory demands and microbial metabolism.

Retrieval of the thickness of undeformed sea ice from C-band compact polarimetric SAR images

NASA Astrophysics Data System (ADS)

Zhang, X.; Dierking, W.; Zhang, J.; Meng, J. M.; Lang, H. T.

2015-10-01

In this paper we introduce a parameter for the retrieval of the thickness of undeformed first-year sea ice that is specifically adapted to compact polarimetric SAR images. The parameter is denoted as "CP-Ratio". In model simulations we investigated the sensitivity of CP-Ratio to the dielectric constant, thickness, surface roughness, and incidence angle. From the results of the simulations we deduced optimal conditions for the thickness retrieval. On the basis of C-band CTLR SAR data, which were generated from Radarsat-2 quad-polarization images acquired jointly with helicopter-borne sea ice thickness measurements in the region of the Sea of Labrador, we tested empirical equations for thickness retrieval. An exponential fit between CP-Ratio and ice thickness provides the most reliable results. Based on a validation using other compact polarimetric SAR images from the same region we found a root mean square (rms) error of 8 cm and a maximum correlation coefficient of 0.92 for the retrieval procedure when applying it on level ice of 0.9 m mean thickness.

Advances in land modeling of KIAPS based on the Noah Land Surface Model

NASA Astrophysics Data System (ADS)

Koo, Myung-Seo; Baek, Sunghye; Seol, Kyung-Hee; Cho, Kyoungmi

2017-08-01

As of 2013, the Noah Land Surface Model (LSM) version 2.7.1 was implemented in a new global model being developed at the Korea Institute of Atmospheric Prediction Systems (KIAPS). This land surface scheme is further refined in two aspects, by adding new physical processes and by updating surface input parameters. Thus, the treatment of glacier land, sea ice, and snow cover are addressed more realistically. Inconsistencies in the amount of absorbed solar flux at ground level by the land surface and radiative processes are rectified. In addition, new parameters are available by using 1-km land cover data, which had usually not been possible at a global scale. Land surface albedo/emissivity climatology is newly created using Moderate-Resolution Imaging Spectroradiometer (MODIS) satellitebased data and adjusted parameterization. These updates have been applied to the KIAPS-developed model and generally provide a positive impact on near-surface weather forecasting.

Remote sensing algorithm for sea surface CO2 in the Baltic Sea

NASA Astrophysics Data System (ADS)

Parard, G.; Charantonis, A. A.; Rutgerson, A.

2014-08-01

Studies of coastal seas in Europe have brought forth the high variability in the CO2 system. This high variability, generated by the complex mechanisms driving the CO2 fluxes makes their accurate estimation an arduous task. This is more pronounced in the Baltic Sea, where the mechanisms driving the fluxes have not been as highly detailed as in the open oceans. In adition, the joint availability of in-situ measurements of CO2 and of sea-surface satellite data is limited in the area. In this paper, a combination of two existing methods (Self-Organizing-Maps and Multiple Linear regression) is used to estimate ocean surface pCO2 in the Baltic Sea from remotely sensed surface temperature, chlorophyll, coloured dissolved organic matter, net primary production and mixed layer depth. The outputs of this research have an horizontal resolution of 4 km, and cover the period from 1998 to 2011. The reconstructed pCO2 values over the validation data set have a correlation of 0.93 with the in-situ measurements, and a root mean square error is of 38 μatm. The removal of any of the satellite parameters degraded this reconstruction of the CO2 flux, and we chose therefore to complete any missing data through statistical imputation. The CO2 maps produced by this method also provide a confidence level of the reconstruction at each grid point. The results obtained are encouraging given the sparsity of available data and we expect to be able to produce even more accurate reconstructions in the coming years, in view of the predicted acquisitions of new data.

Effects of Atmospheric Water and Surface Wind on Passive Microwave Retrievals of Sea Ice Concentration: a Simulation Study

NASA Astrophysics Data System (ADS)

Shin, D.; Chiu, L. S.; Clemente-Colon, P.

2006-05-01

The atmospheric effects on the retrieval of sea ice concentration from passive microwave sensors are examined using simulated data typical for the Arctic summer. The simulation includes atmospheric contributions of cloud liquid water, water vapor and surface wind on the microwave signatures. A plane parallel radiative transfer model is used to compute brightness temperatures at SSM/I frequencies over surfaces that contain open water, first-year (FY) ice and multi-year (MY) ice and their combinations. Synthetic retrievals in this study use the NASA Team (NT) algorithm for the estimation of sea ice concentrations. This study shows that if the satellite sensor's field of view is filled with only FY ice the retrieval is not much affected by the atmospheric conditions due to the high contrast between emission signals from FY ice surface and the signals from the atmosphere. Pure MY ice concentration is generally underestimated due to the low MY ice surface emissivity that results in the enhancement of emission signals from the atmospheric parameters. Simulation results in marginal ice areas also show that the atmospheric effects from cloud liquid water, water vapor and surface wind tend to degrade the accuracy at low sea ice concentration. FY ice concentration is overestimated and MY ice concentration is underestimated in the presence of atmospheric water and surface wind at low ice concentration. This compensating effect reduces the retrieval uncertainties of total (FY and MY) ice concentration. Over marginal ice zones, our results suggest that strong surface wind is more important than atmospheric water in contributing to the retrieval errors of total ice concentrations in the normal ranges of these variables.

Information content in reflected signals during GPS Radio Occultation observations

NASA Astrophysics Data System (ADS)

Aparicio, Josep M.; Cardellach, Estel; Rodríguez, Hilda

2018-04-01

The possibility of extracting useful information about the state of the lower troposphere from the surface reflections that are often detected during GPS radio occultations (GPSRO) is explored. The clarity of the reflection is quantified, and can be related to properties of the surface and the low troposphere. The reflected signal is often clear enough to show good phase coherence, and can be tracked and processed as an extension of direct non-reflected GPSRO atmospheric profiles. A profile of bending angle vs. impact parameter can be obtained for these reflected signals, characterized by impact parameters that are below the apparent horizon, and that is a continuation at low altitude of the standard non-reflected bending angle profile. If there were no reflection, these would correspond to tangent altitudes below the local surface, and in particular below the local mean sea level. A forward operator is presented, for the evaluation of the bending angle of reflected GPSRO signals, given atmospheric properties as described by a numerical weather prediction system. The operator is an extension, at lower impact parameters, of standard bending angle operators, and reproduces both the direct and reflected sections of the measured profile. It can be applied to the assimilation of the reflected section of the profile as supplementary data to the direct section. Although the principle is also applicable over land, this paper is focused on ocean cases, where the topographic height of the reflecting surface, the sea level, is better known a priori.

The impact of marine surface organic enrichment on the measured hygroscopicity parameter of laboratory generated sea-spray aerosols

NASA Astrophysics Data System (ADS)

Schill, S.; Novak, G.; Zimmermann, K.; Bertram, T. H.

2014-12-01

The ocean serves as a major source for atmospheric aerosol particles, yet the chemicophysical properties of sea spray aerosol to date are not well characterized. Understanding the transfer of organic compounds, present in the sea surface microlayer (SSML), to sea-spray particles and their resulting impact on cloud formation is important for predicting aerosol impact on climate in remote marine environments. Here, we present a series of laboratory experiments designed to probe the fractionation of select organic molecules during wave breaking. We use a representative set of organic mimics (e.g. sterols, sugars, lipids, proteins, fatty acids) to test a recent physically based model of organic enrichment in sea-spray aerosol [Burrows et al., 2014] that is based on Langmuir absorption equilibria. Experiments were conducted in the UCSD Marine Aerosol Reference Tank (MART) permitting accurate representation of wave breaking processes in the laboratory. We report kappa values for the resulting sea-spray aerosols and compare them to a predictions made using Kappa-Köhler Theory driven by a linear combination of the pure component kappa values. Hygroscopicity determinations made using the model systems are discussed within the context of measurements of CCN activity made using natural, coastal water.

Spatio-temporal variability of lightning and convective activity over South/South-East Asia with an emphasis during El Niño and La Niña

NASA Astrophysics Data System (ADS)

Saha, Upal; Siingh, Devendraa; Midya, S. K.; Singh, R. P.; Singh, A. K.; Kumar, S.

2017-11-01

The present analysis investigates the spatio-temporal variability of the convective parameters and associated lightning flash rates during the period 1997-2013 including the El Niño and La Niña episode. It reveals that north-western and north-eastern part along the foothills of Himalayas as well as Indo-China peninsular region and South China Sea are much convective prone zones over the South/South-East Asia. The terrain/orography of the Himalayan range, the influence of cross-equatorial low-level jet and large-scale circulation during pre-monsoon and active phase of monsoon, the western Pacific Warm Pool with increased sea surface temperature as well as the solar-heating-originated local instability instigate the convective anomaly to propagate over the north-western and north eastern Indian sub-continent along with the Indo-China peninsula and South China Sea respectively. The land surfaces of the Indian sub-continent and the sea surface of South China Sea possesses significant correlation with lightning flash rates and convective parameters whereas the sea surface surrounding Indian sub-continent do not show such good correlations among them. Although, the occurrence of convective activities during the El Niño (La Niña) gets reduced (increased), the occurrence of lightning flashes gets enhanced (diminished) during this period which may be the direct consequence of warming atmosphere in relation to changing patterns of regional climate. Fig. S2 Spatial trend distribution per year of (a) LFR, (b) CAPE, (c) SCP, (d) LI, (e) CINE and (f) AT anomaly over South/South-East Asia during January-December for the years 1997-2013 (Trend is significant at 95% confidence level). Fig. S3 Correlation maps of LFR with (a) CAPE, (b) SCP, (c) CINE and (d) LI over South/South-East Asia during January-December for the years 1997-2013. Fig. S4 Synoptic wind direction patterns during (a)-(b) El Niño (May 2002 - February 2003) conditions and (c)-(d) La Niña (July 1998 - March 2001) conditions at 1000 hPa and 850 hPa pressure levels respectively over South/South-East Asia region.

Latitudinal and Longitudinal Basin-scale Surface Salinity Contrasts and Freshwater Transport by Ocean Thermohaline Circulation

NASA Astrophysics Data System (ADS)

Seidov, D.; Haupt, B. J.

2003-12-01

The role of sea surface salinity (SSS) contrasts in maintaining vigorous global ocean thermohaline circulation (THC) is revisited. Relative importance of different generalizations of sea surface conditions in climate studies is explored. In numerical experiments using an ocean general circulation model, we have aggregated the observed sea surface temperature (SST) and SSS in several different ways: we used observed unchanged SST with SSS taken as constant (34.25 psu) everywhere; SST unchanged, and SSS zonally averaged globally, i.e., in the whole World Ocean; SST averaged globally, and SSS unchanged; SST zonally averaged globally and SSS zonally averaged basin-wide in individual basins, i.e., in the Atlantic, Indian, Pacific, and Southern Oceans separately; and, finally, both SST and SSS zonally averaged in individual basins. Global zonal averaging removes all longitudinal differences in sea surface climatology among ocean basins. However, latitudinal profiles of zonally averaged parameters preserve the main character of large-scale equator-to-pole sea surface variability. Basin-wide zonal averaging does an even better job of preserving latitudinal distributions within each basin. The results of the experiments could hardly be anticipated a priory. Surprisingly, SST could be used as a 2-D field, or as a zonally-averaged field without much difference in the THC dynamics. Moreover, SST could be averaged either globally, or basin-wide, and it also did not change the overall character of THC. At the same time, THC responded vigorously to how the SSS has been changed. It appeared that the THC structure with the globally averaged SST and basin-wide averaged SSS was very close to the one obtained in the control run (control run operates with 2-D observed SST and SSS). Our main conclusion is that ocean-wide inter-basin sea surface salinity contrasts serve as the major controlling element in global thermohaline circulation. Thermal inter-basin contrasts, as well as longitudinal variation in SSS, are less important than latitudinal thermal gradients and inter-basin salinity contrasts. Details of SSS also decrease in importance as soon as its inter-basin contrasts are retained. This is especially important for paleoclimate and future climate simulations, as only the large-scale inter-basin contrasts of the sea surface conditions really matter.

Controlling Structure and Properties of High Surface Area Nonwoven Materials via Hydroentangling

NASA Astrophysics Data System (ADS)

Luzius, Dennis

Hydroentangling describes a technique using a series of high-velocity water jets to mechanically interlock and entangle fibers. Over the last decades researchers worked on a fundamental understanding of the process and the factors influencing the properties of the final nonwoven material. Recent studies discovered hydroentangling to be capable to create unique, knot-like structures characterized by high- and low density regions, which are believed to have interesting properties for filtration applications. However, just little is known about the impact of hydroentangling parameters on the properties of filtration media to this day. In this study we report on the effect of various hydroentangling parameters, such as jet spacing, manifold pressure, number of manifolds but also specific energy on the structure and properties of high surface area nonwoven materials. Latter was achieved by different bicomponent fiber technologies and subsequent treatments removing the sacrificial compound from the structure. The highest BET surface area was measured to be 3.5 m2 g-1 and the smallest mean fiber size about 0.5 mum. Hydroentangling with large jet spacing was found to be a parameter significantly enhancing the filtration properties of caustic-treated island-in-the-sea nonwoven materials. Moreover, improved capture efficiencies and reduced pressure drops were achieved by reducing the manifold pressure and therefore specific energy during hydroentangling. Jet spacing but not island count was found to be the dominant factor influencing the structure and properties of island-in-the-sea nonwovens. Contrary to our initial expectations increasing the island count and thus decreasing the fiber size did not result in better filtration properties. Mixed media nonwoven structures made from homocomponent and island-in-the-sea fibers were found to have lower densities, higher air permeabilities and better quality factors compared to island-in-the-sea structures hydroentangled under the exact same conditions. Study showed the specific energy to not be an adequate measure for describing the process-structure relationship in hydroentangling. Hydroentangling with same specific energy but different manifold pressures revealed the structure and properties to be different and the peak manifold pressure to be the dominant parameter. It was further shown that hydroentangling with multiple manifolds but same water pressure influences the structure and properties of mono- and bicomponent nonwoven materials. Hydroentangling with three manifolds having the same water pressure resulted in stronger, less permeable fabrics compared to two manifolds or one manifold with the same water pressure. Necessary hydroentangling intensity for winged and island-in-the-sea nonwoven materials was found to be different. Winged fiber nonwovens required higher manifold pressures and a different energy ratio than island-in-in-the-sea nonwovens. Hydroentangling winged fiber webs with jet spacing larger than 600 mum resulted in materials too weak to withstand the caustic-treatment. Study indicated the charging potential of winged fiber nonwovens to be superior compared to island-in-the-sea-structures. In contrast to winged fiber nonwovens, island-in-the-sea structures showed higher pressure drops after corona discharge. Loading winged fiber nonwovens with potassium chloride revealed caustic-treated, IPA discharged materials to show the highest loading capacity.

Global climatology and variability of potential new production estimated from remote sensing of sea-surface temperature

NASA Technical Reports Server (NTRS)

Dugdale, Richard C.; Wilkerson, Frances P.

1995-01-01

During this project we have collected numerous shipboard data-bases of oceanic nitrate and silicate versus temperature for both equatorial and coastal upwelling regions. These cruises all have accompanying N-15 measurements of new production. The inverse relationships between nutrients and temperatures have been determined and are being used to obtain surface nutrient fields from sea surface temperatures measured remotely by satellite borne sensors- i.e. AVHRR data from NOAA satellites contained in the MCSST data set for the world ocean provided by the University of Miami. The images and data derived from space in this way show the strong seasonal fluctuations and interannual el Nino fluctuations of the nitrate field. the nitrate data has been used to make estimates of new production for the equatorial pacific which are compared with shipboard measurements when available. The importance of silicate as a nutrient driving new production and the ratio of nitrate to silicate has been discovered to be crucial to better understand the causes of new production variability, so we have added these parameters to our study and have begun to make estimates of these for the equatorial Pacific, derived from the weekly averaged sea surface temperatures (SSTs).

How does the Redi parameter for mesoscale mixing impact global climate in an Earth System Model?

NASA Astrophysics Data System (ADS)

Pradal, Marie-Aude; Gnanadesikan, Anand

2014-09-01

A coupled climate model is used to examine the impact of an increase in the mixing due to mesoscale eddies on the global climate system. A sixfold increase in the Redi mixing coefficient ARedi, which is within the admissible range of variation, has the overall effect of warming the global-mean surface air and sea surface temperatures by more than 1°C. Locally, sea surface temperatures increase by up to 7°C in the North Pacific and by up to 4°C in the Southern Ocean, with corresponding impacts on the ice concentration and ice extent in polar regions. However, it is not clear that the changes in heat transport from tropics to poles associated with changing this coefficient are primarily responsible for these changes. We found that the changes in the transport of heat are often much smaller than changes in long-wave trapping and short-wave absorption. Additionally, changes in the advective and diffusive transport of heat toward the poles often oppose each other. However, we note that the poleward transport of salt increases near the surface as ARedi increases. We suggest a causal chain in which enhanced eddy stirring leads to increased high-latitude surface salinity reducing salt stratification and water column stability and enhancing convection, triggering two feedback loops. In one, deeper convection prevents sea ice formation, which decreases albedo, which increases SW absorption, further increasing SST and decreasing sea ice formation. In the other, increased SST and reduced sea ice allow for more water vapor in the atmosphere, trapping long-wave radiation. Destratifying the polar regions is thus a potential way in which changes in ocean circulation might warm the planet.

The influence of larval migration and dispersal depth on potential larval trajectories of a deep-sea bivalve

NASA Astrophysics Data System (ADS)

McVeigh, Doreen M.; Eggleston, David B.; Todd, Austin C.; Young, Craig M.; He, Ruoying

2017-09-01

Many fundamental questions in marine ecology require an understanding of larval dispersal and connectivity, yet direct observations of larval trajectories are difficult or impossible to obtain. Although biophysical models provide an alternative approach, in the deep sea, essential biological parameters for these models have seldom been measured empirically. In this study, we used a biophysical model to explore the role of behaviorally mediated migration from two methane seep sites in the Gulf of Mexico on potential larval dispersal patterns and population connectivity of the deep-sea mussel ;Bathymodiolus; childressi, a species for which some biological information is available. Three possible larval dispersal strategies were evaluated for larvae with a Planktonic Larval Duration (PLD) of 395 days: (1) demersal drift, (2) dispersal near the surface early in larval life followed by an extended demersal period before settlement, and (3) dispersal near the surface until just before settlement. Upward swimming speeds varied in the model based on the best data available. Average dispersal distances for simulated larvae varied between 16 km and 1488 km. Dispersal in the upper water column resulted in the greatest dispersal distance (1173 km ± 2.00), followed by mixed dispersal depth (921 km ± 2.00). Larvae originating in the Gulf of Mexico can potentially seed most known seep metapopulations on the Atlantic continental margin, whereas larvae drifting demersally cannot (237 km ± 1.43). Depth of dispersal is therefore shown to be a critical parameter for models of deep-sea connectivity.

SEAHT: A computer program for the use of intersecting arcs of altimeter data for sea surface height refinement

NASA Technical Reports Server (NTRS)

Allen, C. P.; Martin, C. F.

1977-01-01

The SEAHT program is designed to process multiple passes of altimeter data with intersecting ground tracks, with the estimation of corrections for orbital errors to each pass such that the data has the best overall agreement at the crossover points. Orbit error for each pass is modeled as a polynomial in time, with optional orders of 0, 1, or 2. One or more passes may be constrained in the adjustment process, thus allowing passes with the best orbits to provide the overall level and orientation of the estimated sea surface heights. Intersections which disagree by more than an input edit level are not used in the error parameter estimation. In the program implementation, passes are grouped into South-North passes and North-South passes, with the North-South passes partitioned out for the estimation of orbit error parameters. Computer core utilization is thus dependent on the number of parameters estimated for the set of South-North arcs, but is independent on the number of North-South passes. Estimated corrections for each pass are applied to the data at its input data rate and an output tape is written which contains the corrected data.

Numerical study of electromagnetic scattering from one-dimensional nonlinear fractal sea surface

NASA Astrophysics Data System (ADS)

Xie, Tao; He, Chao; William, Perrie; Kuang, Hai-Lan; Zou, Guang-Hui; Chen, Wei

2010-02-01

In recent years, linear fractal sea surface models have been developed for the sea surface in order to establish an electromagnetic backscattering model. Unfortunately, the sea surface is always nonlinear, particularly at high sea states. We present a nonlinear fractal sea surface model and derive an electromagnetic backscattering model. Using this model, we numerically calculate the normalized radar cross section (NRCS) of a nonlinear sea surface. Comparing the averaged NRCS between linear and nonlinear fractal models, we show that the NRCS of a linear fractal sea surface underestimates the NRCS of the real sea surface, especially for sea states with high fractal dimensions, and for dominant ocean surface gravity waves that are either very short or extremely long.

A study of sea lion hydrodynamics using a robotic foreflipper platform

NASA Astrophysics Data System (ADS)

Kulkarni, Aditya A.; Patel, Rahi K.; Leftwich, Megan C.

2016-11-01

Unlike most fish and mammals-that utilize BCF swimming-sea lions rely on their foreflippers to generate thrust without a characteristic flapping frequency. This unique swimming style allows the sea lion to be highly maneuverable, while also producing high amounts of thrust. To explore this motion, and the physics that underlies it, we use novel markerless tracking techniques on untrained sea lions at the Smithsonian National Zoo in Washington, D.C to get the complete motion during different maneuvers. High speed video and three-dimensional surface reconstruction techniques are used to extract the foreflippers kinematics during the thrust phase. Using this data, pitch angle is calculated with respect to the base of the flipper to build a scaled robotic flipper. Dye visualization is carried out in a water channel by injecting dye upstream of the leading edge of the flipper with flow speed set to explore different parameters, like Reynolds number or angular velocity. Results show low pressure on the upper surface of the flipper causes the fluid to be pulled around the flipper forming a vortex that moves fully out of the plane.

The Aquarius Salinity Retrieval Algorithm

NASA Technical Reports Server (NTRS)

Meissner, Thomas; Wentz, Frank; Hilburn, Kyle; Lagerloef, Gary; Le Vine, David

2012-01-01

The first part of this presentation gives an overview over the Aquarius salinity retrieval algorithm. The instrument calibration [2] converts Aquarius radiometer counts into antenna temperatures (TA). The salinity retrieval algorithm converts those TA into brightness temperatures (TB) at a flat ocean surface. As a first step, contributions arising from the intrusion of solar, lunar and galactic radiation are subtracted. The antenna pattern correction (APC) removes the effects of cross-polarization contamination and spillover. The Aquarius radiometer measures the 3rd Stokes parameter in addition to vertical (v) and horizontal (h) polarizations, which allows for an easy removal of ionospheric Faraday rotation. The atmospheric absorption at L-band is almost entirely due to molecular oxygen, which can be calculated based on auxiliary input fields from numerical weather prediction models and then successively removed from the TB. The final step in the TA to TB conversion is the correction for the roughness of the sea surface due to wind, which is addressed in more detail in section 3. The TB of the flat ocean surface can now be matched to a salinity value using a surface emission model that is based on a model for the dielectric constant of sea water [3], [4] and an auxiliary field for the sea surface temperature. In the current processing only v-pol TB are used for this last step.

A Metagenomics Transect into the Deepest Point of the Baltic Sea Reveals Clear Stratification of Microbial Functional Capacities

PubMed Central

Poole, Anthony M.; Sjöberg, Britt-Marie; Sjöling, Sara

2013-01-01

The Baltic Sea is characterized by hyposaline surface waters, hypoxic and anoxic deep waters and sediments. These conditions, which in turn lead to a steep oxygen gradient, are particularly evident at Landsort Deep in the Baltic Proper. Given these substantial differences in environmental parameters at Landsort Deep, we performed a metagenomic census spanning surface to sediment to establish whether the microbial communities at this site are as stratified as the physical environment. We report strong stratification across a depth transect for both functional capacity and taxonomic affiliation, with functional capacity corresponding most closely to key environmental parameters of oxygen, salinity and temperature. We report similarities in functional capacity between the hypoxic community and hadal zone communities, underscoring the substantial degree of eutrophication in the Baltic Proper. Reconstruction of the nitrogen cycle at Landsort deep shows potential for syntrophy between archaeal ammonium oxidizers and bacterial denitrification at anoxic depths, while anaerobic ammonium oxidation genes are absent, despite substantial ammonium levels below the chemocline. Our census also reveals enrichment in genetic prerequisites for a copiotrophic lifestyle and resistance mechanisms reflecting adaptation to prevalent eutrophic conditions and the accumulation of environmental pollutants resulting from ongoing anthropogenic pressures in the Baltic Sea. PMID:24086414

An ensemble of eddy-permitting global ocean reanalyses from the MyOcean project

NASA Astrophysics Data System (ADS)

Masina, Simona; Storto, Andrea; Ferry, Nicolas; Valdivieso, Maria; Haines, Keith; Balmaseda, Magdalena; Zuo, Hao; Drevillon, Marie; Parent, Laurent

2017-08-01

A set of four eddy-permitting global ocean reanalyses produced in the framework of the MyOcean project have been compared over the altimetry period 1993-2011. The main differences among the reanalyses used here come from the data assimilation scheme implemented to control the ocean state by inserting reprocessed observations of sea surface temperature (SST), in situ temperature and salinity profiles, sea level anomaly and sea-ice concentration. A first objective of this work includes assessing the interannual variability and trends for a series of parameters, usually considered in the community as essential ocean variables: SST, sea surface salinity, temperature and salinity averaged over meaningful layers of the water column, sea level, transports across pre-defined sections, and sea ice parameters. The eddy-permitting nature of the global reanalyses allows also to estimate eddy kinetic energy. The results show that in general there is a good consistency between the different reanalyses. An intercomparison against experiments without data assimilation was done during the MyOcean project and we conclude that data assimilation is crucial for correctly simulating some quantities such as regional trends of sea level as well as the eddy kinetic energy. A second objective is to show that the ensemble mean of reanalyses can be evaluated as one single system regarding its reliability in reproducing the climate signals, where both variability and uncertainties are assessed through the ensemble spread and signal-to-noise ratio. The main advantage of having access to several reanalyses differing in the way data assimilation is performed is that it becomes possible to assess part of the total uncertainty. Given the fact that we use very similar ocean models and atmospheric forcing, we can conclude that the spread of the ensemble of reanalyses is mainly representative of our ability to gauge uncertainty in the assimilation methods. This uncertainty changes a lot from one ocean parameter to another, especially in global indices. However, despite several caveats in the design of the multi-system ensemble, the main conclusion from this study is that an eddy-permitting multi-system ensemble approach has become mature and our results provide a first step towards a systematic comparison of eddy-permitting global ocean reanalyses aimed at providing robust conclusions on the recent evolution of the oceanic state.

High frequency acoustic propagation under variable sea surfaces

NASA Astrophysics Data System (ADS)

Senne, Joseph

This dissertation examines the effects of rough sea surfaces and sub-surface bubbles on high frequency acoustic transmissions. Owing to the strong attenuation of electromagnetic waves in seawater, acoustic waves are used in the underwater realm much in the same way that electromagnetic waves are used in the atmosphere. The transmission and reception of acoustic waves in the underwater environment is important for a variety of fields including navigation, ocean observation, and real-time communications. Rough sea surfaces and sub-surface bubbles alter the acoustic signals that are received not only in the near-surface water column, but also at depth. This dissertation demonstrates that surface roughness and sub-surface bubbles notably affect acoustic transmissions with frequency ranges typical of underwater communications systems (10-50 kHz). The influence of rough surfaces on acoustic transmissions is determined by modeling forward propagation subject to sea surface dynamics that vary with time scales of less than a second to tens of seconds. A time-evolving rough sea surface model is combined with a rough surface formulation of a parabolic equation model for predicting time-varying acoustic fields. Linear surface waves are generated from surface wave spectra, and evolved in time using a Runge-Kutta integration technique. This evolving, range-dependent surface information is combined with other environmental parameters and fed into the acoustic model, giving an approximation of the time-varying acoustic field. The wide-angle parabolic equation model manages the rough sea surfaces by molding them into the boundary conditions for calculations of the near-surface acoustic field. The influence of sub-surface bubbles on acoustic transmissions is determined by modeling the population of bubbles near the surface and using those populations to approximate the effective changes in sound speed and attenuation. Both range-dependent and range-independent bubble models are considered, with the range-dependent model varying over the same time scales as the sea surface model and the range-independent model invariant over time. The bubble-induced sound speed and attenuation fluctuations are read in by the parabolic equation model, which allows for the effects of surface roughness and sub-surface bubbles to be computed separately or together. These merged acoustic models are validated using concurrently-collected acoustic and environmental information, including surface wave spectra. Data to model comparisons demonstrate that the models are able to approximate the ensemble-averaged acoustic intensity at ranges of at least a kilometer for acoustic signals of 10-20 kHz. The rough surface model is shown to capture variations due to surface fluctuations occurring over time scales of less than a second to tens of seconds. The separate bubble models demonstrate the abilities to account for the intermittency of bubble plumes and to determine overall effect of bubbly layers, respectively. The models are shown to capture variations in the acoustic field occurring over time scales of less than a second to tens of seconds. Comparisons against data demonstrate the ability of the model to track acoustic transmissions under evolving sea surfaces. The effects of the evolving bubble field are demonstrated through the use of idealized test cases. For frequency ranges important to communications, surface roughness is shown to have the more dominant effect, with bubbles having an ancillary effect.

Temporal variatiions of Sea ice cover in the Baltic Sea derived from operational sea ice products used in NWP.

NASA Astrophysics Data System (ADS)

Lange, Martin; Paul, Gerhard; Potthast, Roland

2014-05-01

Sea ice cover is a crucial parameter for surface fluxes of heat and moisture over water areas. The isolating effect and the much higher albedo strongly reduces the turbulent exchange of heat and moisture from the surface to the atmosphere and allows for cold and dry air mass flow with strong impact on the stability of the whole boundary layer and consequently cloud formation as well as precipitation in the downstream regions. Numerical weather centers as, ECMWF, MetoFrance or DWD use external products to initialize SST and sea ice cover in their NWP models. To the knowledge of the author there are mainly two global sea ice products well established with operational availability, one from NOAA NCEP that combines measurements with satellite data, and the other from OSI-SAF derived from SSMI/S sensors. The latter one is used in the Ostia product. DWD additionally uses a regional product for the Baltic Sea provided by the national center for shipping and hydrografie which combines observations from ships (and icebreakers) for the German part of the Baltic Sea and model analysis from the hydrodynamic HIROMB model of the Swedish meteorological service for the rest of the domain. The temporal evolution of the three different products are compared for a cold period in Februar 2012. Goods and bads will be presented and suggestions for a harmonization of strong day to day jumps over large areas are suggested.

Reproductive performance and diving behaviour share a common sea-ice concentration optimum in Adélie penguins (Pygoscelis adeliae).

PubMed

Le Guen, Camille; Kato, Akiko; Raymond, Ben; Barbraud, Christophe; Beaulieu, Michaël; Bost, Charles-André; Delord, Karine; MacIntosh, Andrew J J; Meyer, Xavier; Raclot, Thierry; Sumner, Michael; Takahashi, Akinori; Thiebot, Jean-Baptiste; Ropert-Coudert, Yan

2018-06-29

The Southern Ocean is currently experiencing major environmental changes, including in sea-ice cover. Such changes strongly influence ecosystem structure and functioning and affect the survival and reproduction of predators such as seabirds. These effects are likely mediated by reduced availability of food resources. As such, seabirds are reliable eco-indicators of environmental conditions in the Antarctic region. Here, based on nine years of sea-ice data, we found that the breeding success of Adélie penguins (Pygoscelis adeliae) reaches a peak at intermediate sea-ice cover (ca. 20%). We further examined the effects of sea-ice conditions on the foraging activity of penguins, measured at multiple scales from individual dives to foraging trips. Analysis of temporal organisation of dives, including fractal and bout analyses, revealed an increasingly consistent behaviour during years with extensive sea-ice cover. The relationship between several dive parameters and sea-ice cover in the foraging area appears to be quadratic. In years of low and high sea-ice cover, individuals adjusted their diving effort by generally diving deeper, more frequently and by resting at the surface between dives for shorter periods of time than in years with intermediate sea-ice cover. Our study therefore suggests that sea-ice cover is likely to affect the reproductive performance of Adélie penguins through its effects on foraging behaviour, as breeding success and most diving parameters share a common optimum. Some years, however, deviated from this general trend, suggesting that other factors (e.g. precipitation during the breeding season) might sometimes become preponderant over the sea-ice effects on breeding and foraging performance. Our study highlights the value of monitoring fitness parameters and individual behaviour concomitantly over the long term to better characterize optimal environmental conditions and potential resilience of wildlife. Such an approach is crucial if we want to anticipate the effects of environmental change on Antarctic penguin populations. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Improving Wind Predictions in the Marine Atmospheric Boundary Layer Through Parameter Estimation in a Single Column Model

DOE PAGES

Lee, Jared A.; Hacker, Joshua P.; Monache, Luca Delle; ...

2016-08-03

A current barrier to greater deployment of offshore wind turbines is the poor quality of numerical weather prediction model wind and turbulence forecasts over open ocean. The bulk of development for atmospheric boundary layer (ABL) parameterization schemes has focused on land, partly due to a scarcity of observations over ocean. The 100-m FINO1 tower in the North Sea is one of the few sources worldwide of atmospheric profile observations from the sea surface to turbine hub height. These observations are crucial to developing a better understanding and modeling of physical processes in the marine ABL. In this paper we usemore » the WRF single column model (SCM), coupled with an ensemble Kalman filter from the Data Assimilation Research Testbed (DART), to create 100-member ensembles at the FINO1 location. The goal of this study is to determine the extent to which model parameter estimation can improve offshore wind forecasts. Combining two datasets that provide lateral forcing for the SCM and two methods for determining z 0, the time-varying sea-surface roughness length, we conduct four WRF-SCM/DART experiments over the October-December 2006 period. The two methods for determining z 0 are the default Fairall-adjusted Charnock formulation in WRF, and using parameter estimation techniques to estimate z 0 in DART. Using DART to estimate z 0 is found to reduce 1-h forecast errors of wind speed over the Charnock-Fairall z 0 ensembles by 4%–22%. Finally, however, parameter estimation of z 0 does not simultaneously reduce turbulent flux forecast errors, indicating limitations of this approach and the need for new marine ABL parameterizations.« less

Role of North Indian Ocean Air-Sea Interaction in Summer Monsoon Intraseasonal Oscillation

NASA Astrophysics Data System (ADS)

Zhang, L.; Han, W.; Li, Y.

2017-12-01

Air-sea coupling processes over the North Indian Ocean associated with Indian summer monsoon intraseasonal oscillation (MISO) are analyzed. Observations show that MISO convection anomalies affect underlying sea surface temperature (SST) through changes in surface shortwave radiation (via cloud cover change) and surface latent heat flux (associated with surface wind speed change). In turn, SST anomalies determine the changing rate of MISO precipitation (dP/dt): warm (cold) SST anomalies cause increasing (decreasing) precipitation rate through increasing (decreasing) surface convergence. Air-sea interaction gives rise to a quadrature relationship between MISO precipitation and SST anomalies. A local air-sea coupling model (LACM) is established based on these observed physical processes, which is a damped oscillatory system with no external forcing. The period of LACM is proportional to the square root of mean state mixed layer depth , assuming other physical parameters remain unchanged. Hence, LACM predicts a relatively short (long) MISO period over the North Indian Ocean during the May-June monsoon developing (July-August mature) phase when is shallow (deep). This result is consistent with observed MISO statistics. An oscillatory external forcing of a typical 30-day period is added to LACM, representing intraseasonal oscillations originated from the equatorial Indian Ocean and propagate into the North Indian Ocean. The period of LACM is then determined by both the inherent period associated with local air-sea coupling and the period of external forcing. It is found that resonance occurs when , amplifying the MISO in situ. This result explains the larger MISO amplitude during the monsoon developing phase compared to the mature phase, which is associated with seasonal cycle of . LACM, however, fails to predict the observed small MISO amplitude during the September-October monsoon decaying phase, when is also shallow. This deficiency might be associated with the neglect of oceanic processes in LACM.

Greenland Ice Sheet Surface Temperature, Melt, and Mass Loss: 2000-2006

NASA Technical Reports Server (NTRS)

Hall, Dorothy K.; Williams, Richard S., Jr.; Luthcke, Scott B.; DiGirolamo, Nocolo

2007-01-01

Extensive melt on the Greenland Ice Sheet has been documented by a variety of ground and satellite measurements in recent years. If the well-documented warming continues in the Arctic, melting of the Greenland Ice Sheet will likely accelerate, contributing to sea-level rise. Modeling studies indicate that an annual or summer temperature rise of 1 C on the ice sheet will increase melt by 20-50% therefore, surface temperature is one of the most important ice-sheet parameters to study for analysis of changes in the mass balance of the ice-sheet. The Greenland Ice Sheet contains enough water to produce a rise in eustatic sea level of up to 7.0 m if the ice were to melt completely. However, even small changes (centimeters) in sea level would cause important economic and societal consequences in the world's major coastal cities thus it is extremely important to monitor changes in the ice-sheet surface temperature and to ultimately quantify these changes in terms of amount of sea-level rise. We have compiled a high-resolution, daily time series of surface temperature of the Greenland Ice Sheet, using the I-km resolution, clear-sky land-surface temperature (LST) standard product from the Moderate-Resolution Imaging Spectroradiometer (MODIS), from 2000 - 2006. We also use Gravity Recovery and Climate Experiment (GRACE) data, averaged over 10-day periods, to measure change in mass of the ice sheet as it melt and snow accumulates. Surface temperature can be used to determine frequency of surface melt, timing of the start and the end of the melt season, and duration of melt. In conjunction with GRACE data, it can also be used to analyze timing of ice-sheet mass loss and gain.

GNSS as a sea ice sensor - detecting coastal freeze states with ground-based GNSS-R

NASA Astrophysics Data System (ADS)

Strandberg, Joakim; Hobiger, Thomas; Haas, Rüdiger

2017-04-01

Based on the idea of using freely available signals for remote sensing, ground-based GNSS-reflectometry (GNSS-R) has found more and more applications in hydrology, oceanography, agriculture and other Earth sciences. GNSS-R is based on analysing the elevation dependent SNR patterns of GNSS signals, and traditionally only the oscillation frequency and phase have been studied to retrieve parameters from the reflecting surfaces. However, recently Strandberg et al. (2016) developed an inversion algorithm that has changed the paradigms of ground-based GNSS-R as it enables direct access to the radiometric properties of the reflector. Using the signal envelope and the rate at which the magnitude of the SNR oscillations are damped w.r.t. satellite elevation, the algorithm retrieves the roughness of the reflector surface amongst other parameters. Based on this idea, we demonstrate for the first time that a GNSS installation situated close to the coastline can detect the presence of sea-ice unambiguously. Using data from the GTGU antenna at the Onsala Space Observatory, Sweden, the time series of the derived damping parameter clearly matches the occurrence of ice in the bay where the antenna is situated. Our results were validated against visual inspection logs as well as with the help of ice charts from the Swedish Meteorological and Hydrological Institute. Our method is even sensitive to partial and intermediate ice formation stages, with clear difference in response between frazil ice and both open and solidly frozen water surfaces. As the GTGU installation is entirely built with standard geodetic equipment, the method can be applied directly to any coastal GNSS site, allowing analysis of both new and historical data. One can use the method as an automatic way of retrieving independent ground truth data for ice extent measurements for use in hydrology, cryosphere studies, and even societal interest fields such as sea transportation. Finally, the new method opens up for further studies in the response of GNSS-R to ice-related parameters, as periods of ice can easily be detected in both historical and new GNSS data. Strandberg J., T. Hobiger, and Rüdiger Haas (2016), Improving GNSS-R sea level determination through inverse modeling of SNR data, Radio Science, 51(8), 1286-1296, doi:10.1002/2016RS006057.

Operational Monitoring and Forecasting in Regional Seas: the Aegean Sea example

NASA Astrophysics Data System (ADS)

Nittis, K.; Perivoliotis, L.; Zervakis, V.; Papadopoulos, A.; Tziavos, C.

2003-04-01

The increasing economic activities in the coastal zone and the associated pressure on the marine environment have raised the interest on monitoring systems able to provide supporting information for its effective management and protection. Such an integrated monitoring, forecasting and information system is being developed during the past years in the Aegean Sea. Its main component is the POSEIDON network that provides real-time data for meteorological and surface oceanographic parameters (waves, currents, hydrological and biochemical data) from 11 fixed oceanographic buoys. The numerical forecasting system is composed by an ETA atmospheric model, a WAM wave model and a POM hydrodynamic model that provide every day 72 hours forecasts. The system is operational since May 2000 and its products are published through Internet while a sub-set is also available through cellular telephony. New type of observing platforms will be available in the near future through a number of EU funded research projects. The Mediterranean Moored Multi-sensor Array (M3A) that was developed for the needs of the Mediterranean Forecasting System and was tested during 2000-2001 will be operational in 2004 during the MFSTEP project. The M3A system incorporates sensors for optical and chemical measurements (Oxygen, Turbidity, Chlorophyll-a, Nutrients and PAR) in the euphotic zone (0-100m) together with sensors for physical parameters (Temperature, Salinity, Current speed and direction) at the 0-500m layer. A Ferry-Box system will also operate during 2004 in the southern Aegean Sea, providing surface data for physical and bio-chemical properties. The ongoing modeling efforts include coupling with larger scale circulation models of the Mediterranean, high-resolution downscaling to coastal areas of the Aegean Sea and development of multi-variate data assimilation methods.

Sensitivities of Modeled Tropical Cyclones to Surface Friction and the Coriolis Parameter

NASA Technical Reports Server (NTRS)

Chao, Winston C.; Chen, Baode; Tao, Wei-Kuo; Lau, William K. M. (Technical Monitor)

2002-01-01

In this investigation the sensitivities of a 2-D tropical cyclone (TC) model to surface frictional coefficient and the Coriolis parameter are studied and their implication is discussed. The model used is an axisymmetric version of the latest version of the Goddard cloud ensemble model. The model has stretched vertical grids with 33 levels varying from 30 m near the bottom to 1140 m near the top. The vertical domain is about 21 km. The horizontal domain covers a radius of 962 km (770 grids) with a grid size of 1.25 km. The time step is 10 seconds. An open lateral boundary condition is used. The sea surface temperature is specified at 29C. Unless specified otherwise, the Coriolis parameter is set at its value at 15 deg N. The Newtonian cooling is used with a time scale of 12 hours. The reference vertical temperature profile used in the Newtonian cooling is that of Jordan. The Newtonian cooling models not only the effect of radiative processes but also the effect of processes with scale larger than that of TC. Our experiments showed that if the Newtonian cooling is replaced by a radiation package, the simulated TC is much weaker. The initial condition has a temperature uniform in the radial direction and its vertical profile is that of Jordan. The initial winds are a weak Rankin vortex in the tangential winds superimposed on a resting atmosphere. The initial sea level pressure is set at 1015 hPa everywhere. Since there is no surface pressure perturbation, the initial condition is not in gradient balance. This initial condition is enough to lead to cyclogenesis, but the initial stage (say, the first 24 hrs) is not considered to resemble anything observed. The control experiment reaches quasi-equilibration after about 10 days with an eye wall extending from 15 to 25 km radius, reasonable comparing with the observations. The maximum surface wind of more than 70 m/s is located at about 18 km radius. The minimum sea level pressure on day 10 is about 886 hPa. Thus the overall simulation is considered successful and the model is considered adequate for our investigation.

September Arctic Sea Ice minimum prediction - a new skillful statistical approach

NASA Astrophysics Data System (ADS)

Ionita-Scholz, Monica; Grosfeld, Klaus; Scholz, Patrick; Treffeisen, Renate; Lohmann, Gerrit

2017-04-01

Sea ice in both Polar Regions is an important indicator for the expression of global climate change and its polar amplification. Consequently, a broad interest exists on sea ice, its coverage, variability and long term change. Knowledge on sea ice requires high quality data on ice extent, thickness and its dynamics. However, its predictability is complex and it depends on various climate and oceanic parameters and conditions. In order to provide insights into the potential development of a monthly/seasonal signal of sea ice evolution, we developed a robust statistical model based on ocean heat content, sea surface temperature and different atmospheric variables to calculate an estimate of the September Sea ice extent (SSIE) on monthly time scale. Although previous statistical attempts at monthly/seasonal forecasts of SSIE show a relatively reduced skill, we show here that more than 92% (r = 0.96) of the September sea ice extent can be predicted at the end of May by using previous months' climate and oceanic conditions. The skill of the model increases with a decrease in the time lag used for the forecast. At the end of August, our predictions are even able to explain 99% of the SSIE. Our statistical model captures both the general trend as well as the interannual variability of the SSIE. Moreover, it is able to properly forecast the years with extreme high/low SSIE (e.g. 1996/ 2007, 2012, 2013). Besides its forecast skill for SSIE, the model could provide a valuable tool for identifying relevant regions and climate parameters that are important for the sea ice development in the Arctic and for detecting sensitive and critical regions in global coupled climate models with focus on sea ice formation.

The impact of the snow cover on sea-ice thickness products retrieved by Ku-band radar altimeters

NASA Astrophysics Data System (ADS)

Ricker, R.; Hendricks, S.; Helm, V.; Perovich, D. K.

2015-12-01

Snow on sea ice is a relevant polar climate parameter related to ocean-atmospheric interactions and surface albedo. It also remains an important factor for sea-ice thickness products retrieved from Ku-band satellite radar altimeters like Envisat or CryoSat-2, which is currently on its mission and the subject of many recent studies. Such satellites sense the height of the sea-ice surface above the sea level, which is called sea-ice freeboard. By assuming hydrostatic equilibrium and that the main scattering horizon is given by the snow-ice interface, the freeboard can be transformed into sea-ice thickness. Therefore, information about the snow load on hemispherical scale is crucial. Due to the lack of sufficient satellite products, only climatological values are used in current studies. Since such values do not represent the high variability of snow distribution in the Arctic, they can be a substantial contributor to the total sea-ice thickness uncertainty budget. Secondly, recent studies suggest that the snow layer cannot be considered as homogenous, but possibly rather featuring a complex stratigraphy due to wind compaction and/or ice lenses. Therefore, the Ku-band radar signal can be scattered at internal layers, causing a shift of the main scattering horizon towards the snow surface. This alters the freeboard and thickness retrieval as the assumption that the main scattering horizon is given by the snow-ice interface is no longer valid and introduces a bias. Here, we present estimates for the impact of snow depth uncertainties and snow properties on CryoSat-2 sea-ice thickness retrievals. We therefore compare CryoSat-2 freeboard measurements with field data from ice mass-balance buoys and aircraft campaigns from the CryoSat Validation Experiment. This unique validation dataset includes airborne laser scanner and radar altimeter measurements in spring coincident to CryoSat-2 overflights, and allows us to evaluate how the main scattering horizon is altered by the presence of a complex snow stratigraphy.

Assimilation of seasonal chlorophyll and nutrient data into an adjoint three-dimensional ocean carbon cycle model: Sensitivity analysis and ecosystem parameter optimization

NASA Astrophysics Data System (ADS)

Tjiputra, Jerry F.; Polzin, Dierk; Winguth, Arne M. E.

2007-03-01

An adjoint method is applied to a three-dimensional global ocean biogeochemical cycle model to optimize the ecosystem parameters on the basis of SeaWiFS surface chlorophyll observation. We showed with identical twin experiments that the model simulated chlorophyll concentration is sensitive to perturbation of phytoplankton and zooplankton exudation, herbivore egestion as fecal pellets, zooplankton grazing, and the assimilation efficiency parameters. The assimilation of SeaWiFS chlorophyll data significantly improved the prediction of chlorophyll concentration, especially in the high-latitude regions. Experiments that considered regional variations of parameters yielded a high seasonal variance of ecosystem parameters in the high latitudes, but a low variance in the tropical regions. These experiments indicate that the adjoint model is, despite the many uncertainties, generally capable to optimize sensitive parameters and carbon fluxes in the euphotic zone. The best fit regional parameters predict a global net primary production of 36 Pg C yr-1, which lies within the range suggested by Antoine et al. (1996). Additional constraints of nutrient data from the World Ocean Atlas showed further reduction in the model-data misfit and that assimilation with extensive data sets is necessary.

Mapping Environmental Suitability for Malaria Transmission, Greece

PubMed Central

Sudre, Bertrand; Rossi, Massimiliano; Van Bortel, Wim; Danis, Kostas; Baka, Agoritsa; Vakalis, Nikos

2013-01-01

During 2009–2012, Greece experienced a resurgence of domestic malaria transmission. To help guide malaria response efforts, we used spatial modeling to characterize environmental signatures of areas suitable for transmission. Nonlinear discriminant analysis indicated that sea-level altitude and land-surface temperature parameters are predictive in this regard. PMID:23697370

New Theory for Tsunami Propagation and Estimation of Tsunami Source Parameters

NASA Astrophysics Data System (ADS)

Mindlin, I. M.

2007-12-01

In numerical studies based on the shallow water equations for tsunami propagation, vertical accelerations and velocities within the sea water are neglected, so a tsunami is usually supposed to be produced by an initial free surface displacement in the initially still sea. In the present work, new theory for tsunami propagation across the deep sea is discussed, that accounts for the vertical accelerations and velocities. The theory is based on the solutions for the water surface displacement obtained in [Mindlin I.M. Integrodifferential equations in dynamics of a heavy layered liquid. Moscow: Nauka*Fizmatlit, 1996 (Russian)]. The solutions are valid when horizontal dimensions of the initially disturbed area in the sea surface are much larger than the vertical displacement of the surface, which applies to the earthquake tsunamis. It is shown that any tsunami is a combination of specific basic waves found analytically (not superposition: the waves are nonlinear), and consequently, the tsunami source (i.e., the initially disturbed body of water) can be described by the numerable set of the parameters involved in the combination. Thus the problem of theoretical reconstruction of a tsunami source is reduced to the problem of estimation of the parameters. The tsunami source can be modelled approximately with the use of a finite number of the parameters. Two-parametric model is discussed thoroughly. A method is developed for estimation of the model's parameters using the arrival times of the tsunami at certain locations, the maximum wave-heights obtained from tide gauge records at the locations, and the distances between the earthquake's epicentre and each of the locations. In order to evaluate the practical use of the theory, four tsunamis of different magnitude occurred in Japan are considered. For each of the tsunamis, the tsunami energy (E below), the duration of the tsunami source formation T, the maximum water elevation in the wave originating area H, mean radius of the area R, and the average magnitude of the sea surface displacement at the margin of the wave originating area h are estimated using tide gauges records. The results are compared (and, in the author's opinion, are in line) with the estimates known in the literature. Compared to the methods employed in the literature, there is no need to use bathymetry (and, consequently, refraction diagrams) for the estimations. The present paper follows closely earlier works [Mindlin I.M., 1996; Mindlin I.M. J. Appl. Math. Phys. (ZAMP), 2004, vol.55, pp. 781-799] and adds to their theoretical results. Example. The Hiuganada earthquake of 1968, April, 1, 9h 42m JST. A tsunami of moderate size arrived at the coast of the south-western part of Shikoku and the eastern part of Kyushu, Japan. Tsunami parameters listed above are estimated with the theory being discussed for two models of tsunami generation: (a) by initial free surface displacement (the case for numerical studies): E=1.91· 1012J, R=22km, h=17.2cm; and (b) by a sudden change in the velocity field of initially still water: E=8.78· 1012J, R=20.4km, h=9.2cm. These values are in line with known estimates [Soloviev S.L., Go Ch.N. Catalogue of tsunami in the West of Pacific Ocean. Moscow, 1974]: E=1.3· 1013J (attributed to Hatori), E=(1.4 - 2.2)· 1012J (attributed to Aida), R=21.2km, h=20cm [Hatory T., Bull. Earthq. Res. Inst., Tokyo Univ., 1969, vol. 47, pp. 55-63]. Also, estimates are obtained for the values that could not be found based on shallow water wave theory: (a) H=3.43m and (b) H=1.38m, T=16.4sec.

Blood biochemistry reference values for wild juvenile loggerhead sea turtles (Caretta caretta) from Madeira archipelago.

PubMed

Delgado, Cláudia; Valente, Ana; Quaresma, Isabel; Costa, Margarida; Dellinger, Thomas

2011-07-01

Standard biochemical parameters were determined in wild juvenile loggerhead sea turtles Caretta caretta living offshore Madeira Island, northeast Atlantic. We analyzed the influence of age, sex, sea surface temperature, and body condition index on biochemical parameters including uric acid, total bilirubin, total cholesterol, creatinine kinase (CK), glucose, total protein, urea nitrogen, lactate dehydrogenase, aspartate aminotranspherase (AST), gamma-glutamyl transferase (GGT), albumin, alkaline phosphatase (ALP), sodium (NA), potassium (K), chloride, calcium, phosphorus, and magnesium. Significant positive correlations were found between turtle body size and total cholesterol, total protein, and albumin. Total protein and the enzymes AST and CK were lower than reported levels in adults. Calcium levels were lower than those reported in adult or captive turtles, but similar to wild juveniles from Australian waters, and were interpreted as normal for this age category. These data may be useful to evaluate the health status of stranded or injured animals and to improve veterinary care at rehabilitation centers.

Models and observations of Arctic melt ponds

NASA Astrophysics Data System (ADS)

Golden, K. M.

2016-12-01

During the Arctic melt season, the sea ice surface undergoes a striking transformation from vast expanses of snow covered ice to complex mosaics of ice and melt ponds. Sea ice albedo, a key parameter in climate modeling, is largely determined by the complex evolution of melt pond configurations. In fact, ice-albedo feedback has played a significant role in the recent declines of the summer Arctic sea ice pack. However, understanding melt pond evolution remains a challenge to improving climate projections. It has been found that as the ponds grow and coalesce, the fractal dimension of their boundaries undergoes a transition from 1 to about 2, around a critical length scale of 100 square meters in area. As the ponds evolve they take complex, self-similar shapes with boundaries resembling space-filling curves. I will outline how mathematical models of composite materials and statistical physics, such as percolation and Ising models, are being used to describe this evolution and predict key geometrical parameters that agree very closely with observations.

Reconstruction of the sea surface elevation from the analysis of the data collected by a wave radar system

NASA Astrophysics Data System (ADS)

Ludeno, Giovanni; Soldovieri, Francesco; Serafino, Francesco; Lugni, Claudio; Fucile, Fabio; Bulian, Gabriele

2016-04-01

X-band radar system is able to provide information about direction and intensity of the sea surface currents and dominant waves in a range of few kilometers from the observation point (up to 3 nautical miles). This capability, together with their flexibility and low cost, makes these devices useful tools for the sea monitoring either coastal or off-shore area. The data collected from wave radar system can be analyzed by using the inversion strategy presented in [1,2] to obtain the estimation of the following sea parameters: peak wave direction; peak period; peak wavelength; significant wave height; sea surface current and bathymetry. The estimation of the significant wave height represents a limitation of the wave radar system because of the radar backscatter is not directly related to the sea surface elevation. In fact, in the last period, substantial research has been carried out to estimate significant wave height from radar images either with or without calibration using in-situ measurements. In this work, we will present two alternative approaches for the reconstruction of the sea surface elevation from wave radar images. In particular, the first approach is based on the basis of an approximated version of the modulation transfer function (MTF) tuned from a series of numerical simulation, following the line of[3]. The second approach is based on the inversion of radar images using a direct regularised least square technique. Assuming a linearised model for the tilt modulation, the sea elevation has been reconstructed as a least square fitting of the radar imaging data[4]. References [1]F. Serafino, C. Lugni, and F. Soldovieri, "A novel strategy for the surface current determination from marine X-band radar data," IEEE Geosci.Remote Sens. Lett., vol. 7, no. 2, pp. 231-235, Apr. 2010. [2]Ludeno, G., Brandini, C., Lugni, C., Arturi, D., Natale, A., Soldovieri, F., Serafino, F. (2014). Remocean System for the Detection of the Reflected Waves from the Costa Concordia Ship Wreck. IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing, 7(7). [3]Nieto Borge, J., Rodriguez, G.R., Hessner, K., González, P.I., (2004). Inversion of Marine Radar Images for Surface Wave Analysis. J. Atmos. Oceanic Technol. 21, 1291-1300. [4] Fucile, F., Ludeno, G., Serafino, F.,Bulian, G., Soldovieri, F., Lugni, C. "Some challenges in recovering wave features from a wave radar system". Paper submitted to the International Ocean and Polar Engineering Conference, ISOPE, Rhodes 2016

Resolution Enhancement of Spaceborne Radiometer Images

NASA Technical Reports Server (NTRS)

Krim, Hamid

2001-01-01

Our progress over the last year has been along several dimensions: 1. Exploration and understanding of Earth Observatory System (EOS) mission with available data from NASA. 2. Comprehensive review of state of the art techniques and uncovering of limitations to be investigated (e.g. computational, algorithmic ...). and 3. Preliminary development of resolution enhancement algorithms. With the advent of well-collaborated satellite microwave radiometers, it is now possible to obtain long time series of geophysical parameters that are important for studying the global hydrologic cycle and earth radiation budget. Over the world's ocean, these radiometers simultaneously measure profiles of air temperature and the three phases of atmospheric water (vapor, liquid, and ice). In addition, surface parameters such as the near surface wind speed, the sea surface temperature, and the sea ice type and concentration can be retrieved. The special sensor microwaves imager SSM/I has wide application in atmospheric remote sensing over the ocean and provide essential inputs to numerical weather-prediction models. SSM/I data has also been used for land and ice studies, including snow cover classification measurements of soil and plant moisture contents, atmospheric moisture over land, land surface temperature and mapping polar ice. The brightness temperature observed by SSM/I is function of the effective brightness temperature of the earth's surface and the emission scattering and attenuation of the atmosphere. Advanced Microwave Scanning Radiometer (AMSR) is a new instrument that will measure the earth radiation over the spectral range from 7 to 90 GHz. Over the world's ocean, it will be possible to retrieve the four important geographical parameters SST, wind speed, vertically integrated water vapor, vertically integrated cloud liquid water L.

On the influence of ocean waves on simulated GNSS-R delay-doppler maps

NASA Astrophysics Data System (ADS)

Clarizia, M. P.; di Bisceglie, M.; Galdi, C.; Gommenginger, C.; Srokosz, M.

2012-04-01

Global Navigation Satellite System-Reflectometry (GNSS-R), is an established technique that exploits GNSS signals of opportunity reflected from the surface of the ocean, to look primarily at the ocean surface roughness. The strength of this technique, and the primary motivation to carry it forward, is in the fact that GNSS signals are available globally, all the time and over the long term, and could help dramatically improve the monitoring of ocean wind and waves. GNSS-R offers the prospect of high density global measurements of directional sea surface roughness, which are essential for scientific purposes (i.e. quantifying the air-sea exchanges of gases), operational weather and ocean forecasting (i.e. prediction of high winds, dangerous sea states, risk of flooding and storm surges) and to support important climate-relevant Earth Observation techniques (IR SST, or surface salinity retrieval). The retrieval of ocean roughness from GNSS-R data has now been demonstrated with a reasonable level of accuracy from both airborne [1] and spaceborne [2] platforms. In both cases, Directional Mean Square Slopes (DMSS) of the ocean surface have been retrieved from GNSS-R data, in the form of Delay-Doppler Maps (DDMs), using an established theoretical scattering model by Zavorotny and Voronovich (Z-V) [3]. The need for a better assessment of the way the ocean waves influence the scattering of GPS signals has recently led to a different approach, consisting of simulating the scattering of such signals, using a more sophisticated large-scale scattering model than Z-V, and explicit simulations of realistic seas. Initial results produced from these simulations have been recently published in [4], where the emphasis has been put on the effects of different sea states on Radar Cross Section (RCS) and Polarization Ratio (PR) in space domain. Linear wind wave surfaces have been simulated using the Elfouhaily wind wave spectrum [5], for different wind speeds and directions, and with or without a superimposed swell. Then, the scattering from such surfaces has been computed using the innovative Facet Approach (FA), which approximates the surface through a number of rectangular facets, differently oriented, and calculates the surface scattering as the ensemble of the signals scattered from all the facets. Here we proceed with the next step of the GPS-Reflectometry simulator, through investigation of the results in Delay- Doppler (DD) domain. Changes and variations of the DDMs, computed using the FA scattering model, are investigated for a variety of wind and wave conditions of the underlying sea surfaces simulated. Results are analysed for changing wind speed and direction of the waves, presence of a swell component superimposed on wind waves, and changing parameters (wavelength, amplitude, direction) of the swell, revealing some degree of sensitivity of these maps to different sea states. The effect of polarization is also taken into account, through an analysis of PR in DD domain. Finally, an initial investigation into the effect of nonlinearities on the sea surface in DD domain is carried out, by looking at DDMs of the signal scattered from non linear non gaussian sea surfaces explicitly simulated.

A joint method to retrieve directional ocean wave spectra from SAR and wave spectrometer data

NASA Astrophysics Data System (ADS)

Ren, Lin; Yang, Jingsong; Zheng, Gang; Wang, Juan

2016-07-01

This paper proposes a joint method to simultaneously retrieve wave spectra at different scales from spaceborne Synthetic Aperture Radar (SAR) and wave spectrometer data. The method combines the output from the two different sensors to overcome retrieval limitations that occur in some sea states. The wave spectrometer sensitivity coefficient is estimated using an effective significant wave height (SWH), which is an average of SAR-derived and wave spectrometer-derived SWH. This averaging extends the area of the sea surface sampled by the nadir beam of the wave spectrometer to improve the accuracy of the estimated sensitivity coefficient in inhomogeneous sea states. Wave spectra are then retrieved from SAR data using wave spectrometer-derived spectra as first guess spectra to complement the short waves lost in SAR data retrieval. In addition, the problem of 180° ambiguity in retrieved spectra is overcome using SAR imaginary cross spectra. Simulated data were used to validate the joint method. The simulations demonstrated that retrieved wave parameters, including SWH, peak wave length (PWL), and peak wave direction (PWD), agree well with reference parameters. Collocated data from ENVISAT advanced SAR (ASAR), the airborne wave spectrometer STORM, the PHAROS buoy, and the European Centre for Medium-Range Weather Forecasting (ECMWF) were then used to verify the proposed method. Wave parameters retrieved from STORM and two ASAR images were compared to buoy and ECMWF wave data. Most of the retrieved parameters were comparable to reference parameters. The results of this study show that the proposed joint retrieval method could be a valuable complement to traditional methods used to retrieve directional ocean wave spectra, particularly in inhomogeneous sea states.

Assessing the Internal Consistency of the Marine Carbon Dioxide System at High Latitudes: The Labrador Sea AR7W Line Study Case

NASA Astrophysics Data System (ADS)

Raimondi, L.; Azetsu-Scott, K.; Wallace, D.

2016-02-01

This work assesses the internal consistency of ocean carbon dioxide through the comparison of discrete measurements and calculated values of four analytical parameters of the inorganic carbon system: Total Alkalinity (TA), Dissolved Inorganic Carbon (DIC), pH and Partial Pressure of CO2 (pCO2). The study is based on 486 seawater samples analyzed for TA, DIC and pH and 86 samples for pCO2 collected during the 2014 Cruise along the AR7W line in Labrador Sea. The internal consistency has been assessed using all combinations of input parameters and eight sets of thermodynamic constants (K1, K2) in calculating each parameter through the CO2SYS software. Residuals of each parameter have been calculated as the differences between measured and calculated values (reported as ΔTA, ΔDIC, ΔpH and ΔpCO2). Although differences between the selected sets of constants were observed, the largest were obtained using different pairs of input parameters. As expected the couple pH-pCO2 produced to poorest results, suggesting that measurements of either TA or DIC are needed to define the carbonate system accurately and precisely. To identify signature of organic alkalinity we isolated the residuals in the bloom area. Therefore only ΔTA from surface waters (0-30 m) along the Greenland side of the basin were selected. The residuals showed that no measured value was higher than calculations and therefore we could not observe presence of organic bases in the shallower water column. The internal consistency in characteristic water masses of Labrador Sea (Denmark Strait Overflow Water, North East Atlantic Deep Water, Newly-ventilated Labrador Sea Water, Greenland and Labrador Shelf waters) will also be discussed.

Phytoplankton in the Beaufort and Chukchi Seas: Distributions, Dynamics and Environmental Forcing

NASA Technical Reports Server (NTRS)

Wang, Jian; Cota, Glenn F.; Comiso, Josefino C.

2005-01-01

Time-series of remotely sensed distributions of phytoplankton, sea ice, surface temperature, albedo, and clouds were examined to evaluate the impact of the variability of environmental conditions and physical forcing on the phytoplankton distribution in the Beaufort and Chukchi Seas. Large-scale distributions of these parameters were studied for the first time using weekly and monthly composites from April 1998 through September 2002. The basic data set used in this study are phytoplankton pigment concentration derived from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS), ice concentration obtained from the Special Sensor Microwave Imager (SSM/I) and surface temperature, cloud cover, and albedo derived from the Advanced Very High Resolution Radiometer (AVHRR). Seasonal variations of the sea ice cover was observed to be the dominant environmental factor as the ice edge blooms followed the retreating marginal ice zones northward. Blooms were most prominent in the southwestern Chukchi Sea, and were especially persistent immediately north of the Bering Strait in nutrient- rich Anadyr water and in some fronts. Chlorophyll concentrations are shown to increase from a nominal value during onset of melt in April to a maximum value in mid-spring or summer depending on location. Large interannual variability of ice cover and phytoplankton distributions was observed with the year 1998 being uniquely associated with an early season occurrence of a massive bloom. This is postulated to be caused in part by a rapid response of phytoplankton to an early retreat of the sea ice cover in the Beaufort Sea region. Correlation analyses showed relatively high negative correlation between chlorophyll and ice concentration with the correlation being highest in May, the correlation coefficient being -0.45. 1998 was also the warmest among the five years globally and the sea ice cover was least extensive in the Beaufort-Khukchi Sea region, partly because of the 1997-98 El Nino. Strong correlations were noted between ice extent and surface temperature, the correlation coefficient being highest at - 0.79 in April, during the onset of the bloom period

Using geometry to improve model fitting and experiment design for glacial isostasy

NASA Astrophysics Data System (ADS)

Kachuck, S. B.; Cathles, L. M.

2017-12-01

As scientists we routinely deal with models, which are geometric objects at their core - the manifestation of a set of parameters as predictions for comparison with observations. When the number of observations exceeds the number of parameters, the model is a hypersurface (the model manifold) in the space of all possible predictions. The object of parameter fitting is to find the parameters corresponding to the point on the model manifold as close to the vector of observations as possible. But the geometry of the model manifold can make this difficult. By curving, ending abruptly (where, for instance, parameters go to zero or infinity), and by stretching and compressing the parameters together in unexpected directions, it can be difficult to design algorithms that efficiently adjust the parameters. Even at the optimal point on the model manifold, parameters might not be individually resolved well enough to be applied to new contexts. In our context of glacial isostatic adjustment, models of sparse surface observations have a broad spread of sensitivity to mixtures of the earth's viscous structure and the surface distribution of ice over the last glacial cycle. This impedes precise statements about crucial geophysical processes, such as the planet's thermal history or the climates that controlled the ice age. We employ geometric methods developed in the field of systems biology to improve the efficiency of fitting (geodesic accelerated Levenberg-Marquardt) and to identify the maximally informative sources of additional data to make better predictions of sea levels and ice configurations (optimal experiment design). We demonstrate this in particular in reconstructions of the Barents Sea Ice Sheet, where we show that only certain kinds of data from the central Barents have the power to distinguish between proposed models.

Ensemble data assimilation in the Red Sea: sensitivity to ensemble selection and atmospheric forcing

NASA Astrophysics Data System (ADS)

Toye, Habib; Zhan, Peng; Gopalakrishnan, Ganesh; Kartadikaria, Aditya R.; Huang, Huang; Knio, Omar; Hoteit, Ibrahim

2017-07-01

We present our efforts to build an ensemble data assimilation and forecasting system for the Red Sea. The system consists of the high-resolution Massachusetts Institute of Technology general circulation model (MITgcm) to simulate ocean circulation and of the Data Research Testbed (DART) for ensemble data assimilation. DART has been configured to integrate all members of an ensemble adjustment Kalman filter (EAKF) in parallel, based on which we adapted the ensemble operations in DART to use an invariant ensemble, i.e., an ensemble Optimal Interpolation (EnOI) algorithm. This approach requires only single forward model integration in the forecast step and therefore saves substantial computational cost. To deal with the strong seasonal variability of the Red Sea, the EnOI ensemble is then seasonally selected from a climatology of long-term model outputs. Observations of remote sensing sea surface height (SSH) and sea surface temperature (SST) are assimilated every 3 days. Real-time atmospheric fields from the National Center for Environmental Prediction (NCEP) and the European Center for Medium-Range Weather Forecasts (ECMWF) are used as forcing in different assimilation experiments. We investigate the behaviors of the EAKF and (seasonal-) EnOI and compare their performances for assimilating and forecasting the circulation of the Red Sea. We further assess the sensitivity of the assimilation system to various filtering parameters (ensemble size, inflation) and atmospheric forcing.

Predicting the ocurrence probability of freak waves baed on buoy data and non-stationary extreme value models

NASA Astrophysics Data System (ADS)

Tomas, A.; Menendez, M.; Mendez, F. J.; Coco, G.; Losada, I. J.

2012-04-01

In the last decades, freak or rogue waves have become an important topic in engineering and science. Forecasting the occurrence probability of freak waves is a challenge for oceanographers, engineers, physicists and statisticians. There are several mechanisms responsible for the formation of freak waves, and different theoretical formulations (primarily based on numerical models with simplifying assumption) have been proposed to predict the occurrence probability of freak wave in a sea state as a function of N (number of individual waves) and kurtosis (k). On the other hand, different attempts to parameterize k as a function of spectral parameters such as the Benjamin-Feir Index (BFI) and the directional spreading (Mori et al., 2011) have been proposed. The objective of this work is twofold: (1) develop a statistical model to describe the uncertainty of maxima individual wave height, Hmax, considering N and k as covariates; (2) obtain a predictive formulation to estimate k as a function of aggregated sea state spectral parameters. For both purposes, we use free surface measurements (more than 300,000 20-minutes sea states) from the Spanish deep water buoy network (Puertos del Estado, Spanish Ministry of Public Works). Non-stationary extreme value models are nowadays widely used to analyze the time-dependent or directional-dependent behavior of extreme values of geophysical variables such as significant wave height (Izaguirre et al., 2010). In this work, a Generalized Extreme Value (GEV) statistical model for the dimensionless maximum wave height (x=Hmax/Hs) in every sea state is used to assess the probability of freak waves. We allow the location, scale and shape parameters of the GEV distribution to vary as a function of k and N. The kurtosis-dependency is parameterized using third-order polynomials and the model is fitted using standard log-likelihood theory, obtaining a very good behavior to predict the occurrence probability of freak waves (x>2). Regarding the second objective of this work, we apply different algorithms using three spectral parameters (wave steepness, directional dispersion, frequential dispersion) as predictors, to estimate the probability density function of the kurtosis for a given sea state. ACKNOWLEDGMENTS The authors thank to Puertos del Estado (Spanish Ministry of Public Works) for providing the free surface measurement database.

An analysis of organic matter sources for surface sediments in the central South Yellow Sea, China: evidence based on macroelements and n-alkanes.

PubMed

Zhang, Shengyin; Li, Shuanglin; Dong, Heping; Zhao, Qingfang; Lu, Xinchuan; Shi, Ji'an

2014-11-15

By analyzing the composition of n-alkane and macroelements in the surface sediments of the central South Yellow Sea of China, we evaluated the influencing factors on the distribution of organic matter. The analysis indicates that the distribution of total organic carbon (TOC) was low in the west and high in the east, and TOC was more related to Al2O3 content than medium diameter (MD). The composition of n-alkanes indicated the organic matter was mainly derived from terrestrial higher plants. Contributions from herbaceous plants and woody plants were comparable. The comprehensive analysis of the parameters of macroelements and n-alkanes showed the terrestrial organic matter in the central South Yellow Sea was mainly from the input of the modern Yellow River and old Yellow River. However, some samples exhibited evident input characteristics from petroleum sources, which changed the original n-alkanes of organic matter in sediments. Copyright © 2014 Elsevier Ltd. All rights reserved.

Natural radionuclides tracing in marine surface waters along the northern coast of Oman Sea by combining the radioactivity analysis, oceanic currents and the SWAN model results.

PubMed

Zare, Mohammad Reza; Mostajaboddavati, Mojtaba; Kamali, Mahdi; Tari, Marziyeh; Mosayebi, Sanaz; Mortazavi, Mohammad Seddigh

2015-03-15

This study aims to establish a managed sampling plan for rapid estimate of natural radio-nuclides diffusion in the northern coast of the Oman Sea. First, the natural radioactivity analysis in 36 high volume surface water samples was carried out using a portable high-resolution gamma-ray spectrometry. Second, the oceanic currents in the northern coast were investigated. Then, the third generation spectral SWAN model was utilized to simulate wave parameters. Direction of natural radioactivity propagation was coupled with the preferable wave vectors and oceanic currents direction that face to any marine pollution, these last two factors will contribute to increase or decrease of pollution in each grid. The results were indicated that the natural radioactivity concentration between the grids 8600 and 8604 is gathered in the grid 8600 and between the grids 8605 and 8608 is propagated toward middle part of Oman Sea. Copyright © 2014 Elsevier Ltd. All rights reserved.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jared A.; Hacker, Joshua P.; Monache, Luca Delle

A current barrier to greater deployment of offshore wind turbines is the poor quality of numerical weather prediction model wind and turbulence forecasts over open ocean. The bulk of development for atmospheric boundary layer (ABL) parameterization schemes has focused on land, partly due to a scarcity of observations over ocean. The 100-m FINO1 tower in the North Sea is one of the few sources worldwide of atmospheric profile observations from the sea surface to turbine hub height. These observations are crucial to developing a better understanding and modeling of physical processes in the marine ABL. In this paper we usemore » the WRF single column model (SCM), coupled with an ensemble Kalman filter from the Data Assimilation Research Testbed (DART), to create 100-member ensembles at the FINO1 location. The goal of this study is to determine the extent to which model parameter estimation can improve offshore wind forecasts. Combining two datasets that provide lateral forcing for the SCM and two methods for determining z 0, the time-varying sea-surface roughness length, we conduct four WRF-SCM/DART experiments over the October-December 2006 period. The two methods for determining z 0 are the default Fairall-adjusted Charnock formulation in WRF, and using parameter estimation techniques to estimate z 0 in DART. Using DART to estimate z 0 is found to reduce 1-h forecast errors of wind speed over the Charnock-Fairall z 0 ensembles by 4%–22%. Finally, however, parameter estimation of z 0 does not simultaneously reduce turbulent flux forecast errors, indicating limitations of this approach and the need for new marine ABL parameterizations.« less

Retrieval of the thickness of undeformed sea ice from simulated C-band compact polarimetric SAR images

NASA Astrophysics Data System (ADS)

Zhang, Xi; Dierking, Wolfgang; Zhang, Jie; Meng, Junmin; Lang, Haitao

2016-07-01

In this paper we introduce a parameter for the retrieval of the thickness of undeformed first-year sea ice that is specifically adapted to compact polarimetric (CP) synthetic aperture radar (SAR) images. The parameter is denoted as the "CP ratio". In model simulations we investigated the sensitivity of the CP ratio to the dielectric constant, ice thickness, ice surface roughness, and radar incidence angle. From the results of the simulations we deduced optimal sea ice conditions and radar incidence angles for the ice thickness retrieval. C-band SAR data acquired over the Labrador Sea in circular transmit and linear receive (CTLR) mode were generated from RADARSAT-2 quad-polarization images. In comparison with results from helicopter-borne measurements, we tested different empirical equations for the retrieval of ice thickness. An exponential fit between the CP ratio and ice thickness provides the most reliable results. Based on a validation using other compact polarimetric SAR images from the same region, we found a root mean square (rms) error of 8 cm and a maximum correlation coefficient of 0.94 for the retrieval procedure when applying it to level ice between 0.1 and 0.8 m thick.

A Preliminary Assessment of the S-3A SRAL Performances in SAR Mode

NASA Astrophysics Data System (ADS)

Dinardo, Salvatore; Scharroo, Remko; Bonekamp, Hans; Lucas, Bruno; Loddo, Carolina; Benveniste, Jerome

2016-08-01

The present work aims to assess and characterize the S3-A SRAL Altimeter performance in closed-loop tracking mode and in open ocean conditions. We have processed the Sentinel-3 SAR data products from L0 until L2 using an adaptation of the ESRIN GPOD CryoSat-2 Processor SARvatore.During the Delay-Doppler processing, we have chosen to activate the range zero-padding option.The L2 altimetric geophysical parameters, that are to be validated, are the sea surface height above the ellipsoid (SSH), sea level anomaly (SLA), the significant wave height (SWH) and wind speed (U10), all estimated at 20 Hz.The orbit files are the POD MOE, while the geo- corrections are extracted from the RADS database.In order to assess the accuracy of the wave&wind products, we have been using an ocean wave&wind speed model output (wind speed at 10 meter high above the sea surface) from the ECMWF.We have made a first order approximation of the sea state bias as -4.7% of the SWH.In order to assess the precision performance of SRAL SAR mode, we compute the level of instrumental noise (range, wave height and wind speed) for different conditions of sea state.

Observations and Modeling of Turbulent Air-Sea Coupling in Coastal and Strongly Forced Condition

NASA Astrophysics Data System (ADS)

Ortiz-Suslow, David G.

The turbulent fluxes of momentum, mass, and energy across the ocean-atmosphere boundary are fundamental to our understanding of a myriad of geophysical processes, such as wind-wave generation, oceanic circulation, and air-sea gas transfer. In order to better understand these fluxes, empirical relationships were developed to quantify the interfacial exchange rates in terms of easily observed parameters (e.g., wind speed). However, mounting evidence suggests that these empirical formulae are only valid over the relatively narrow parametric space, i.e. open ocean conditions in light to moderate winds. Several near-surface processes have been observed to cause significant variance in the air-sea fluxes not predicted by the conventional functions, such as a heterogeneous surfaces, swell waves, and wave breaking. Further study is needed to fully characterize how these types of processes can modulate the interfacial exchange; in order to achieve this, a broad investigation into air-sea coupling was undertaken. The primary focus of this work was to use a combination of field and laboratory observations and numerical modeling, in regimes where conventional theories would be expected to breakdown, namely: the nearshore and in very high winds. These seemingly disparate environments represent the marine atmospheric boundary layer at its physical limit. In the nearshore, the convergence of land, air, and sea in a depth-limited domain marks the transition from a marine to a terrestrial boundary layer. Under extreme winds, the physical nature of the boundary layer remains unknown as an intermediate substrate layer, sea spray, develops between the atmosphere and ocean surface. At these ends of the MABL physical spectrum, direct measurements of the near-surface processes were made and directly related to local sources of variance. Our results suggest that the conventional treatment of air-sea fluxes in terms of empirical relationships developed from a relatively narrow set of environmental conditions do not generalize to the coastal and extreme wind environments. This body of work represents a multi-faceted approach to understanding physical air-sea interactions in varied regimes and using a wide array of investigatory methods.

Spatial patterns of water quality parameters in upper layer of the Kara Sea in summer 2016 based on laser remote sensing

NASA Astrophysics Data System (ADS)

Osokina, Varvara; Pelevin, Vadim; Shatravin, Alexander; Belyaev, Nikolay; Demidov, Andrey; Redzhepova, Zuleyha

2017-04-01

The paper represents results of remote sensing by means of Laser Induced Fluorescence LiDAR during the expedition in Kara Sea in summer 2016. The expedition took place in Western and Southern parts of Kara Sea including Ob and Yenisei areas from June, 14 to August, 20 2016. The LiDAR observations were obtained from the research vessel Mstislav Keldysh and included 4600 km of almost continuous measurements and 94 complex stations. As a result now there is a vast LiDAR database available for scientific purposes. The data were processed and recalculated providing a set of high resolution maps of distribution of main oceanographic water quality parameters including chlorophyll "a", total organic carbon and total suspended matter in surface layer. The proceeded maps give a precise information about the location of frontal zones between Ob and Yenisei waters and Kara Sea waters, provide a detailed picture of complex surface water structure in central Kara Sea and other locations and present data about spatial distinction of concentrations of measured water parameters. The LiDAR measurements were afterwards compared to data, obtained by underway flow-through CTD measuring system and satellite images providing adjunct information on water parameters' distribution features. The instruments of UFL (Ultraviolet fluorescent LiDAR) series were developed by the Shirshov Institute of Oceanology, Moscow, Russia, and have been successfully used in lots of scientific expeditions in different water areas. UFL LiDARs take measurements with sampling rate up to 2 Hz from the vessel under way in any weather or sunlight conditions. The measurements are linked to a GPS, and so all data are geo-tagged and can be used to create interpolated maps of the measured parameters. The instrument analyses backward signal from dual excitation (355, 532 nm) laser pulses emitted at 2 Hz. The signal is detected across 11 bands in series (355, 385, 404, 424, 440, 460, 499, 532, 620, 651, 685 nm) on stations, and across 4 bands at the same time (355, 404, 440, 685 nm) in transect mode while the vessel is moving. Fluorescence intensities at 440 and 685 nm and backscattering of the 355 nm laser pulse are normalized to Raman scattering at 404 nm, and then calibrated using a set of laboratory-measured concentrations to derive total organic carbon, chlorophyll a and total suspended matter concentrations.

Intrareef variations in Li/Mg and Sr/Ca sea surface temperature proxies in the Caribbean reef-building coral Siderastrea siderea

NASA Astrophysics Data System (ADS)

Fowell, Sara E.; Sandford, Kate; Stewart, Joseph A.; Castillo, Karl D.; Ries, Justin B.; Foster, Gavin L.

2016-10-01

Caribbean sea surface temperatures (SSTs) have increased at a rate of 0.2°C per decade since 1971, a rate double that of the mean global change. Recent investigations of the coral Siderastrea siderea on the Belize Mesoamerican Barrier Reef System (MBRS) have demonstrated that warming over the last 30 years has had a detrimental impact on calcification. Instrumental temperature records in this region are sparse, making it necessary to reconstruct longer SST records indirectly through geochemical temperature proxies. Here we investigate the skeletal Sr/Ca and Li/Mg ratios of S. siderea from two distinct reef zones (forereef and backreef) of the MBRS. Our field calibrations of S. siderea show that Li/Mg and Sr/Ca ratios are well correlated with temperature, although both ratios are 3 times more sensitive to temperature change in the forereef than in the backreef. These differences suggest that a secondary parameter also influences these SST proxies, highlighting the importance for site- and species-specific SST calibrations. Application of these paleothermometers to downcore samples reveals highly uncertain reconstructed temperatures in backreef coral, but well-matched reconstructed temperatures in forereef coral, both between Sr/Ca-SSTs and Li/Mg-SSTs, and in comparison to the Hadley Centre Sea Ice and Sea Surface Temperature record. Reconstructions generated from a combined Sr/Ca and Li/Mg multiproxy calibration improve the precision of these SST reconstructions. This result confirms that there are circumstances in which both Li/Mg and Sr/Ca are reliable as stand-alone and combined proxies of sea surface temperature. However, the results also highlight that high-precision, site-specific calibrations remain critical for reconstructing accurate SSTs from coral-based elemental proxies.

Global Mapping of Underwater UV Irradiances and DNA-Weighted Exposures using TOMS and SeaWiFS Data Products

NASA Technical Reports Server (NTRS)

Vasilkov, Alexander; Krotkov, Nickolay; Herman, Jay; McClain, Charles; Arrigo, Kevin; Robinson, Wayne

1999-01-01

The global stratospheric ozone-layer depletion results In an increase in biologically harmful ultraviolet (UV) radiation reaching the surface and penetrating to ecologically significant depths in natural waters. Such an increase can be estimated on a global scale by combining satellite estimates of UV irradiance at the ocean surface from the Total Ozone Mapping Spectrometer (TOMS) satellite instrument with the SeaWIFS satellite ocean-color measurements in the visible spectral region. In this paper we propose a model of seawater optical properties in the UV spectral region based on the Case I water model in the visible range. The inputs to the model are standard monthly SeaWiFS products: chlorophyll concentration and the diffuse attenuation coefficient at 490nm. Penetration of solar UV radiation to different depths in open ocean waters is calculated using the RT (radiative transfer) quasi-single scattering approximation (QSSA). The accuracy of the QSSA approximation in the water is tested using more accurate codes. The sensitivity study of the underwater UV irradiance to atmospheric and oceanic optical properties have shown that the main environmental parameters controlling the absolute levels of the UVB (280-320nm) and DNA-weighted irradiance underwater are: solar-zenith angle, cloud transmittance, water optical properties, and total ozone. Weekly maps of underwater UV irradiance and DNA-weighted exposure are calculated using monthly-mean SeaWiFS chlorophyll and diffuse attenuation coefficient products, daily SeaWiFS cloud fraction data, and the TOMS-derived surface UV irradiance daily maps. The final products include global maps of weekly-average UVB irradiance and DNA-weighted daily exposures at 3m and 10m, and depths where the UVB irradiance and DNA-weighted dose rate at local noon are equal to 10% of their surface values.

Ocean Acidification from space: recent advances

NASA Astrophysics Data System (ADS)

Sabia, Roberto; Shutler, Jamie; Land, Peter; Fernandez-Prieto, Diego; Donlon, Craig; Reul, Nicolas

2017-04-01

The phenomenon referred to as Ocean Acidification (OA) is gathering increasing attention as one of the major foci of climate-related research, for its profound impact at scientific and socio-economic level. To date, the majority of the scientific studies into the potential impacts of OA have focused on in-situ measurements, laboratory-controlled experiments and models simulations. Satellite remote sensing technology have yet to be fully exploited, despite it has been stressed it could play a significant role by providing synoptic and frequent measurements for investigating globally OA processes, also extending in-situ carbonate chemistry measurements on different spatial/temporal scales [1,2]. Within this context, the purpose of the recently completed ESA "Pathfinders - Ocean Acidification" project was to quantitatively and routinely estimate OA-related parameters by means of a blending of satellite observations and model outputs in five case-study regions (global ocean, Amazon plume, Barents sea, Greater Caribbean and Bay of Bengal). Satellite Ocean Colour, Sea Surface Temperature (SST) and Sea Surface Salinity (SSS) have been exploited, with an emphasis on the latter being the latest addition to the portfolio of satellite measured parameters. A proper merging of these different satellites products allows computing at least two independent proxies among the seawater carbonate system parameters: the partial pressure of CO2 in surface seawater (pCO2); the total Dissolved Inorganic Carbon (DIC), the total alkalinity (TA) and the surface ocean pH. In the project, efforts have been devoted to a systematic characterization of TA and DIC from space in the mentioned case-study regions; in this paper, also through the knowledge of these parameters, the objective is to come up with the currently best educated guess of the surface ocean pH [3] and Aragonite saturation state. This will also include an estimation of the achievable accuracy by propagating the errors in the satellite data sources. The overarching long-term objectives are to develop new algorithms and data processing strategies to overcome the relative immaturity of OA satellite products currently available, and to produce a global, temporally evolving, quasi-operational suite of OA satellite-derived data. References: [1] Land, P., J. Shutler, H. Findlay, F. Girard-Ardhuin, R. Sabia, N. Reul, J.-F. Piolle, B. Chapron, Y. Quilfen, J. Salisbury, D. Vandemark, R. Bellerby, and P. Bhadury, "Salinity from space unlocks satellite-based assessment of ocean acidification", Environmental Science & Technology, DOI: 10.1021/es504849s, Publication Date (Web): January 8, 2015 [2] Salisbury, J., D. Vandemark, B. Jönsson, W. Balch, S. Chakraborty, S. Lohrenz, B. Chapron, B. Hales, A. Mannino, J.T. Mathis, N. Reul, S.R. Signorini, R. Wanninkhof, and K.K. Yates. 2015. How can present and future satellite missions support scientific studies that address ocean acidification? Oceanography 28(2):108-121, http://dx.doi.org/10.5670/oceanog.2015.35. [3] Sabia R., D. Fernández-Prieto, J. Shutler, C. Donlon, P. Land, N. Reul, Remote Sensing of Surface Ocean pH Exploiting Sea Surface Salinity Satellite Observations, IGARSS '15 (International Geoscience and Remote Sensing Symposium), Milano, Italy, July 27 -31, 2015.

Constraining Future Sea Level Rise Estimates from the Amundsen Sea Embayment, West Antarctica

NASA Astrophysics Data System (ADS)

Nias, I.; Cornford, S. L.; Edwards, T.; Gourmelen, N.; Payne, A. J.

2016-12-01

The Amundsen Sea Embayment (ASE) is the primary source of mass loss from the West Antarctic Ice Sheet. The catchment is particularly susceptible to grounding line retreat, because the ice sheet is grounded on bedrock that is below sea level and deepening towards its interior. Mass loss from the ASE ice streams, which include Pine Island, Thwaites and Smith glaciers, is a major uncertainty on future sea level rise, and understanding the dynamics of these ice streams is essential to constraining this uncertainty. The aim of this study is to construct a distribution of future ASE sea level contributions from an ensemble of ice sheet model simulations and observations of surface elevation change. A 284 member ensemble was performed using BISICLES, a vertically-integrated ice flow model with adaptive mesh refinement. Within the ensemble parameters associated with basal traction, ice rheology and sub-shelf melt rate were perturbed, and the effect of bed topography and sliding law were also investigated. Initially each configuration was run to 50 model years. Satellite observations of surface height change were then used within a Bayesian framework to assign likelihoods to each ensemble member. Simulations that better reproduced the current thinning patterns across the catchment were given a higher score. The resulting posterior distribution of sea level contributions is narrower than the prior distribution, although the central estimates of sea level rise are similar between the prior and posterior. The most extreme simulations were eliminated and the remaining ensemble members were extended to 200 years, using a simple melt rate forcing.

Timing of sea ice retreat can alter phytoplankton community structure in the western Arctic Ocean

NASA Astrophysics Data System (ADS)

Fujiwara, A.; Hirawake, T.; Suzuki, K.; Imai, I.; Saitoh, S.-I.

2014-04-01

This study assesses the response of phytoplankton assemblages to recent climate change, especially with regard to the shrinking of sea ice in the northern Chukchi Sea of the western Arctic Ocean. Distribution patterns of phytoplankton groups in the late summers of 2008-2010 were analysed based on HPLC pigment signatures and, the following four major algal groups were inferred via multiple regression and cluster analyses: prasinophytes, diatoms, haptophytes and dinoflagellates. A remarkable interannual difference in the distribution pattern of the groups was found in the northern basin area. Haptophytes dominated and dispersed widely in warm surface waters in 2008, whereas prasinophytes dominated in cold water in 2009 and 2010. A difference in the onset date of sea ice retreat was evident among years-the sea ice retreat in 2008 was 1-2 months earlier than in 2009 and 2010. The spatial distribution of early sea ice retreat matched the areas in which a shift in algal community composition was observed. Steel-Dwass's multiple comparison tests were used to assess the physical, chemical and biological parameters of the four clusters. We found a statistically significant difference in temperature between the haptophyte-dominated cluster and the other clusters, suggesting that the change in the phytoplankton communities was related to the earlier sea ice retreat in 2008 and the corollary increase in sea surface temperatures. Longer periods of open water during the summer, which are expected in the future, may affect food webs and biogeochemical cycles in the western Arctic due to shifts in phytoplankton community structure.

Timing of sea ice retreat can alter phytoplankton community structure in the western Arctic Ocean

NASA Astrophysics Data System (ADS)

name prefix surname suffix, given; Fujiwara, A.; Hirawake, T.; Suzuki, K.; Imai, I.; Saitoh, S.-I.

2013-09-01

This study assesses the response of phytoplankton assemblages to recent climate change, especially with regard to the shrinking of sea ice in the northern Chukchi Sea of the western Arctic Ocean. Distribution patterns of phytoplankton groups in the late summers of 2008-2010 were analyzed based on HPLC pigment signatures and, the following four major algal groups were inferred via multiple regression and cluster analyses: prasinophytes, diatoms, haptophytes and dinoflagellates. A remarkable interannual difference in the distribution pattern of the groups was found in the northern basin area. Haptophytes dominated and dispersed widely in warm surface waters in 2008, whereas prasinophytes dominated in cold water in 2009 and 2010. A difference in the onset date of sea ice retreat was evident among years - the sea ice retreat in 2008 was 1-2 months earlier than in 2009 and 2010. The spatial distribution of early sea ice retreat matched the areas in which a shift in algal community composition was observed. Steel-Dwass's multiple comparison tests were used to assess the physical, chemical and biological parameters of the four clusters. We found a statistically significant difference in temperature between the haptophyte-dominated cluster and the other clusters, suggesting that the change in the phytoplankton communities was related to the earlier sea ice retreat in 2008 and the corollary increase in sea surface temperatures. Longer periods of open water during the summer, which are expected in the future, may affect food webs and biogeochemical cycles in the western Arctic due to shifts in phytoplankton community structure.

A Stokes drift approximation based on the Phillips spectrum

NASA Astrophysics Data System (ADS)

Breivik, Øyvind; Bidlot, Jean-Raymond; Janssen, Peter A. E. M.

2016-04-01

A new approximation to the Stokes drift velocity profile based on the exact solution for the Phillips spectrum is explored. The profile is compared with the monochromatic profile and the recently proposed exponential integral profile. ERA-Interim spectra and spectra from a wave buoy in the central North Sea are used to investigate the behavior of the profile. It is found that the new profile has a much stronger gradient near the surface and lower normalized deviation from the profile computed from the spectra. Based on estimates from two open-ocean locations, an average value has been estimated for a key parameter of the profile. Given this parameter, the profile can be computed from the same two parameters as the monochromatic profile, namely the transport and the surface Stokes drift velocity.

Effect of reflected and refracted signals on coherent underwater acoustic communication: results from the Kauai experiment (KauaiEx 2003).

PubMed

Rouseff, Daniel; Badiey, Mohsen; Song, Aijun

2009-11-01

The performance of a communications equalizer is quantified in terms of the number of acoustic paths that are treated as usable signal. The analysis uses acoustical and oceanographic data collected off the Hawaiian Island of Kauai. Communication signals were measured on an eight-element vertical array at two different ranges, 1 and 2 km, and processed using an equalizer based on passive time-reversal signal processing. By estimating the Rayleigh parameter, it is shown that all paths reflected by the sea surface at both ranges undergo incoherent scattering. It is demonstrated that some of these incoherently scattered paths are still useful for coherent communications. At range of 1 km, optimal communications performance is achieved when six acoustic paths are retained and all paths with more than one reflection off the sea surface are rejected. Consistent with a model that ignores loss from near-surface bubbles, the performance improves by approximately 1.8 dB when increasing the number of retained paths from four to six. The four-path results though are more stable and require less frequent channel estimation. At range of 2 km, ray refraction is observed and communications performance is optimal when some paths with two sea-surface reflections are retained.

Seasonal variations in physico-chemical characteristics of Tuticorin coastal waters, southeast coast of India

NASA Astrophysics Data System (ADS)

Balakrishnan, S.; Chelladurai, G.; Mohanraj, J.; Poongodi, J.

2017-07-01

Physico-chemical parameters were determined along the Vellapatti, Tharuvaikulam and Threspuram coastal waters, southeast coast of India. All the physico-chemical parameters such as sea surface temperature, salinity, pH, total alkalinity, total suspended solids, dissolved oxygen and nutrients like nitrate, nitrite, inorganic phosphate and reactive silicate were studied for a period of 12 months (June 2014-May 2015). Sea surface temperature varied from 26.4 to 29.7 °C. Salinity varied from 26.1 and 36.2 ‰, hydrogen ion concentration ranged between 8.0 and 8.5. Variation in dissolved oxygen content was from 4.125 to 4.963 mg l-1. Total alkalinity ranged from 64 to 99 mg/l. Total suspended solids ranged from 24 to 97 mg/l. Concentrations of nutrients, viz. nitrates (2.047-4.007 μM/l), nitrites (0.215-0.840 μM/l), phosphates (0.167-0.904 µM/l), total phosphorus (1.039-3.479 μM/l), reactive silicates (3.737-8.876 μM/l) ammonia (0.078-0.526 μM/l) and also varied independently.

Bacterial Communities of Surface Mixed Layer in the Pacific Sector of the Western Arctic Ocean during Sea-Ice Melting

PubMed Central

Ha, Ho Kyung; Kim, Hyun Cheol; Kim, Ok-Sun; Lee, Bang Yong; Cho, Jang-Cheon; Hur, Hor-Gil; Lee, Yoo Kyung

2014-01-01

From July to August 2010, the IBRV ARAON journeyed to the Pacific sector of the Arctic Ocean to monitor bacterial variation in Arctic summer surface-waters, and temperature, salinity, fluorescence, and nutrient concentrations were determined during the ice-melting season. Among the measured physicochemical parameters, we observed a strong negative correlation between temperature and salinity, and consequently hypothesized that the melting ice decreased water salinity. The bacterial community compositions of 15 samples, includicng seawater, sea-ice, and melting pond water, were determined using a pyrosequencing approach and were categorized into three habitats: (1) surface seawater, (2) ice core, and (3) melting pond. Analysis of these samples indicated the presence of local bacterial communities; a deduction that was further corroborated by the discovery of seawater- and ice-specific bacterial phylotypes. In all samples, the Alphaproteobacteria, Flavobacteria, and Gammaproteobacteria taxa composed the majority of the bacterial communities. Among these, Alphaproteobacteria was the most abundant and present in all samples, and its variation differed among the habitats studied. Linear regression analysis suggested that changes in salinity could affect the relative proportion of Alphaproteobacteria in the surface water. In addition, the species-sorting model was applied to evaluate the population dynamics and environmental heterogeneity in the bacterial communities of surface mixed layer in the Arctic Ocean during sea-ice melting. PMID:24497990

Bacterial communities of surface mixed layer in the Pacific sector of the western Arctic Ocean during sea-ice melting.

PubMed

Han, Dukki; Kang, Ilnam; Ha, Ho Kyung; Kim, Hyun Cheol; Kim, Ok-Sun; Lee, Bang Yong; Cho, Jang-Cheon; Hur, Hor-Gil; Lee, Yoo Kyung

2014-01-01

From July to August 2010, the IBRV ARAON journeyed to the Pacific sector of the Arctic Ocean to monitor bacterial variation in Arctic summer surface-waters, and temperature, salinity, fluorescence, and nutrient concentrations were determined during the ice-melting season. Among the measured physicochemical parameters, we observed a strong negative correlation between temperature and salinity, and consequently hypothesized that the melting ice decreased water salinity. The bacterial community compositions of 15 samples, includicng seawater, sea-ice, and melting pond water, were determined using a pyrosequencing approach and were categorized into three habitats: (1) surface seawater, (2) ice core, and (3) melting pond. Analysis of these samples indicated the presence of local bacterial communities; a deduction that was further corroborated by the discovery of seawater- and ice-specific bacterial phylotypes. In all samples, the Alphaproteobacteria, Flavobacteria, and Gammaproteobacteria taxa composed the majority of the bacterial communities. Among these, Alphaproteobacteria was the most abundant and present in all samples, and its variation differed among the habitats studied. Linear regression analysis suggested that changes in salinity could affect the relative proportion of Alphaproteobacteria in the surface water. In addition, the species-sorting model was applied to evaluate the population dynamics and environmental heterogeneity in the bacterial communities of surface mixed layer in the Arctic Ocean during sea-ice melting.

Problems inherent in using aircraft for radio oceanography studies

NASA Technical Reports Server (NTRS)

Walsh, E. J.

1977-01-01

Some of the disadvantages relating to altitude stability and proximity to the ocean are described for radio oceanography studies using aircraft. The random oscillatory motion introduced by the autopilot in maintaining aircraft altitude requires a more sophisticated range tracker for a radar altimeter than would be required in a satellite application. One-dimensional simulations of the sea surface (long-crested waves) are performed using both the JONSWAP spectrum and the Pierson-Moskowitz spectrum. The results of the simulation indicate that care must be taken in trying to experimentally verify instrument measurement accuracy. Because of the relatively few wavelengths examined from an aircraft due to proximity to the ocean and low velocity compared to a satellite, the random variation in the sea surface parameters being measured can far exceed an instrument's ability to measure them.

Simulation of an oil film at the sea surface and its radiometric properties in the SWIR

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Van Eijk, Alexander M. J.

2017-10-01

The knowledge of the optical contrast of an oil layer on the sea under various surface roughness conditions is of great interest for oil slick monitoring techniques. This paper presents a 3D simulation of a dynamic sea surface contaminated by a floating oil film. The simulation considers the damping influence of oil on the ocean waves and its physical properties. It calculates the radiance contrast of the sea surface polluted by the oil film in relation to a clean sea surface for the SWIR spectral band. Our computer simulation combines the 3D simulation of a maritime scene (open clear sea/clear sky) with an oil film at the sea surface. The basic geometry of a clean sea surface is modeled by a composition of smooth wind driven gravity waves. Oil on the sea surface attenuates the capillary and short gravity waves modulating the wave power density spectrum of these waves. The radiance of the maritime scene is calculated in the SWIR spectral band with the emitted sea surface radiance and the specularly reflected sky radiance as components. Wave hiding and shadowing, especially occurring at low viewing angles, are considered. The specular reflection of the sky radiance at the clean sea surface is modeled by an analytical statistical bidirectional reflectance distribution function (BRDF) of the sea surface. For oil at the sea surface, a specific BRDF is used influenced by the reduced surface roughness, i.e., the modulated wave density spectrum. The radiance contrast of an oil film in relation to the clean sea surface is calculated for different viewing angles, wind speeds, and oil types characterized by their specific physical properties.

Development of An Autonomous Underwater Glider for Observing Physical Ocean Parameters in Indonesian Seas

NASA Astrophysics Data System (ADS)

Ajie Linarka, Utoyo; Riyanto Trilaksono, Bambang; Sagala, M. Faisal; Hidayat, Egi; Sopaheluwakan, Ardhasena; Rizal, Jose; Heriyanto, Eko; Amsal Harapan, Ferdika; Eka Syahputra Makmur, Erwin

2017-04-01

Conducting a sustained monitoring and surveying of physical ocean parameters for research or operational purposes using moorings and ships would require high cost. Development of an inexpensive instrument capable to perform such tasks not only could reduce cost and risks but also increase cruising range and depth. For that reason, a prototype of underwater glider was developed, named "GaneshBlue". GaneshBlue works based on gliding principles which utilizes pitch angle and buoyancy control for moving. For one gliding movement, GaneshBlue passed through 5 phases of surface, descent, transition, ascent and back to surface. The glider is equipped with basic navigation system and remote control, programmable survey planning, temperature and salinity sampling instruments, lithium batteries for power supply, and information processing software. A field test at the shallow water showed that GaneshBule has successfully demonstrated gliding and surfacing movements with surge motion speed reaching 20 cm s-1and 20 m in depths. During the field test the glider was also equipped with three instruments, i.e. Inertial Measurement Unit (IMU) to estimate glider's speed and orientation; MiniCT to acquire temperature and conductivity data; and Altisounder to determine its distance to sea surface and to seabed. In general, all the instruments performed well but filter algorithm needs to be implemented on data collection procedure to remove data outliers.

Towards uncertainty estimation for operational forecast products - a multi-model-ensemble approach for the North Sea and the Baltic Sea

NASA Astrophysics Data System (ADS)

Golbeck, Inga; Li, Xin; Janssen, Frank

2014-05-01

Several independent operational ocean models provide forecasts of the ocean state (e.g. sea level, temperature, salinity and ice cover) in the North Sea and the Baltic Sea on a daily basis. These forecasts are the primary source of information for a variety of information and emergency response systems used e.g. to issue sea level warnings or carry out oil drift forecast. The forecasts are of course highly valuable as such, but often suffer from a lack of information on their uncertainty. With the aim of augmenting the existing operational ocean forecasts in the North Sea and the Baltic Sea by a measure of uncertainty a multi-model-ensemble (MME) system for sea surface temperature (SST), sea surface salinity (SSS) and water transports has been set up in the framework of the MyOcean-2 project. Members of MyOcean-2, the NOOS² and HIROMB/BOOS³ communities provide 48h-forecasts serving as inputs. Different variables are processed separately due to their different physical characteristics. Based on the so far collected daily MME products of SST and SSS, a statistical method, Empirical Orthogonal Function (EOF) analysis is applied to assess their spatial and temporal variability. For sea surface currents, progressive vector diagrams at specific points are consulted to estimate the performance of the circulation models especially in hydrodynamic important areas, e.g. inflow/outflow of the Baltic Sea, Norwegian trench and English Channel. For further versions of the MME system, it is planned to extend the MME to other variables like e.g. sea level, ocean currents or ice cover based on the needs of the model providers and their customers. It is also planned to include in-situ data to augment the uncertainty information and for validation purposes. Additionally, weighting methods will be implemented into the MME system to develop more complex uncertainty measures. The methodology used to create the MME will be outlined and different ensemble products will be presented. In addition, some preliminary results based on the statistical analysis of the uncertainty measures provide first estimates of the regional and temporal performance of the ocean models for each parameter. ²Northwest European Shelf Operational Oceanography System ³High-resolution Operational Model of the Baltic / Baltic Operational Oceanographic System

Understanding Climate Change and Sea Level: A Case Study of Middle School Student Comprehension and An Evaluation of Tide Gauges off the Panama Canal in the Pacific Ocean and Caribbean Sea

NASA Astrophysics Data System (ADS)

Millan-Otoya, Juan C.

The present study had two main objectives. The first was to determine the degree of understanding of climate change, sea level and sea level rise among middle school students. Combining open-ended questions with likert-scaled questions, we identified student conceptions on these topics in 86 students from 7th and 8th grades during 2012 and 2013 before and after implementing a Curriculum Unit (CU). Additional information was obtained by adding drawings to the open-ended questions during the second year to gauge how student conceptions varied from a verbal and a visual perspective. Misconceptions were identified both pre- and post-CU among all the topics taught. Students commonly used climate and climate change as synonyms, sea level was often defined as water depth, and several students failed to understand the complexities that determine changes in sea level due to wind, tides, and changes in sea surface temperature. In general, 8th grade students demonstrated a better understanding of these topics, as reflected in fewer apparent misconceptions after the CU. No previous study had reported such improvement. This showed the value of implementing short lessons. Using Piaget's theories on cognitive development, the differences between 7th and 8th grade students reflect a transition to a more mature level which allowed students to comprehend more complex concepts that included multiple variables. The second objective was to determine if the frequency of sea level maxima not associated with tides over the last 100 years increased in two tide gauges located on the two extremes of the Panama canal, i.e. Balboa in the Pacific Ocean and Cristobal in the Caribbean Sea. These records were compared to time series of regional sea surface temperature, wind speed, atmospheric pressure, and El Nino-Southern Oscillation (ENSO), to determine if these played a role as physical drivers of sea level at either location. Neither record showed an increase in the frequency of sea level maxima events. No parameter analyzed explained variability in sea level maxima in Cristobal. There was a significant correlation between the zonal component of the wind and sea level at Balboa for the early record (r=0.153; p-value<0.05), but for the most part the p-values did not support the hypothesis of a correlation. Similarly, sea surface temperature had an effect on sea level at Balboa, but the null hypothesis that there is no correlation could not be rejected (p-value>0.05). There was a clear relationship between sea level maxima and ENSO. 70% of the years with higher counts of higher sea level events corresponded to El Nino years. A randomization test with 1000 iterations, shuffling the El Nino years, showed most of these randomizations grouped between 14-35% of the events occurring during a randomized El Nino year. In no iteration did the percentage of events that occurred during El Nino years rise above 65%. The correlation with zonal wind and the probable correlation with sea surface temperature can be linked via ENSO, since ENSO is associated with changes in the strength of the Trade Winds and positive anomalies in the sea surface temperature of the tropical Pacific Ocean.

Occurrence and Turnover of Biogenic Sulfur in the Bering Sea During Summer

NASA Astrophysics Data System (ADS)

Li, Cheng-Xuan; Wang, Bao-Dong; Yang, Gui-Peng; Wang, Zi-Cheng; Chen, Jian-Fang; Lyu, Yang

2017-11-01

The horizontal/geographical variations in dissolved dimethylsulfide (DMS), its precursor dimethylsulfoniopropionate (DMSPd and DMSPp), and chlorophyll a (Chl a), as well as the oceanographic parameters influencing the concentrations of dimethylated sulfur compounds, were investigated in the Bering Sea from July to August 2012. Similar to Chl a, the surface DMS and DMSPp levels, as well as DMS(P) production and consumption rates, exhibited a declining gradient from the central basin to the continental shelf, with high-value areas appearing in the central basin, the slope regions, and Anadyr Strait but a low-value area occurring on the outer-middle continental shelf. Considerably high values of DMS and DMSP were measured in the saline Bering Sea Basin Deep Water (>2,000 m) located at the southwest of the Bering Basin because of the release of resuspension in 2,000 m depth and the DMSP production from endogenous benthic bacteria and cyanobacteria population. Chl a was positively correlated with DMSPp and DMS in the surface waters and the upper water of the basin, whereas significant negative correlations were found between DMS and nutrients (dissolved inorganic nitrogen [DIN], phosphorus, and silicate) in the inner shelf of the Bering Sea. DMS microbial consumption was approximately 6.26 times faster than the DMS sea-air exchange, demonstrating that the major loss of DMS in the surface water occurred through biological consumption relative to evasion into the atmosphere. Average sea-to-air DMS fluxes were estimated to be 4.66 μmol/(m2·d), and consequently oceanic biogenic DMS emission had a dominant contribution to the sulfur budget over the observational area.

Sea-State Dependence of Aerosol Concentration in the Marine Atmospheric Boundary Layer

NASA Astrophysics Data System (ADS)

Lenain, L.; Melville, W. K.

2016-02-01

While sea spray aerosols represent a large portion of the aerosols present in the marine environment, and despite evidence of the importance of surface wave and wave-breaking related processes in the coupling of the ocean with the atmosphere, sea spray source generation functions are traditionally parameterized by the wind speed at 10m. It is clear that unless the wind and wave field are fully developed, the source function will be a function of both wind and wave parameters. In this study, we report on an air-sea interaction experiment, the ONR phase-resolved High-Resolution Air-Sea Interaction experiments (HIRES), conducted off the coast of Northern California in June 2010. Detailed measurements of aerosol number concentration in the Marine Atmospheric Boundary Layer (MABL), at altitudes ranging from as low as 30m and up to 800m AMSL over a broad range of environmental conditions (significant wave height, Hs, of 2 to 4.5m and wind speed at 10m height, U10, of 10 to 18 m/s) collected from an instrumented research aircraft, are presented. Aerosol number densities and volume are computed over a range of particle diameters from 0.1 to 200 µm, while the surface conditions, i.e. significant wave height, moments of the breaker length distribution Λ(c), and wave breaking dissipation, were measured by a suite of electro-optical sensors that included the NASA Airborne Topographic Mapper (ATM). The sea-state dependence of the aerosol concentration in the MABL is evident, ultimately stressing the need to incorporate wave and wave kinematics in the spray source generation functions that are traditionally primarily parameterized by surface winds. A scaling of the measured aerosol volume distribution by wave and atmospheric state variables is proposed.

Coast Salish and U.S. Geological Survey 2009 Tribal Journey water quality project

USGS Publications Warehouse

Akin, Sarah K.; Grossman, Eric E.

2010-01-01

The Salish Sea, contained within the United States and British Columbia, Canada, is the homeland of the Coast Salish Peoples and contains a diverse array of marine resources unique to this area that have sustained Coast Salish cultures and traditions for millennia. In July 2009, the Coast Salish People and U.S. Geological Survey conducted a second water quality study of the Salish Sea to examine spatial and temporal variability of environmental conditions of these surface waters as part of the annual Tribal Journey. Six canoes of approximately 100 towed multi parameter water-quality sondes as the Salish People traveled their ancestral waters during the middle of summer. Sea surface temperature, salinity, pH, dissolved oxygen, and turbidity were measured simultaneously at ten-second intervals, and more than 54,000 data points spanning 1,300 kilometers of the Salish Sea were collected. The project also synthesized Coast Salish ecological knowledge and culture with scientific monitoring to better understand and predict the response of coastal habitats and marine resources. Comparisons with data collected in 2008 reveal significantly higher mean surface-water temperatures in most subbasins in 2009 linked to record air temperatures that affected the Pacific Northwest in July 2009. Through large-scale spatial measurements collected each summer, the project helps to identify patterns in summer water quality, areas of water-quality impairment, and trends occurring through time.

Light induced fluorescence lidar developed and employed at the National Aviation Academy of Azerbaijan

NASA Astrophysics Data System (ADS)

Pashayev, Arif M.; Allahverdiyev, Kerim R.; Tagiyev, Bahadir G.; Sadikhov, Ilham A.

2016-01-01

A new laser induced fluorescence (LIF) KA-14 LIDAR (Light Identification Detection and Ranging) system for detecting of oil spills on the sea surface was developed and employed at the National Aviation Academy of Azerbaijan. Laser's parameters used in LIDAR are as follows: •laser CFR 200- type QUANTEL, λ = 355 nm, beam ∅ = 5.35 mm, f = 20 Hz, pulse duration and power τ = 7 ns and 60 mJ, respectively. The first results of measurements in the laboratory and the results of measurements at natural environment from distances up to 200 m revealed perspectives for using this LIDAR for detection of oil contaminations on sea as well as on earth surfaces (these measurements have been performed at Pirallahi Oil-Gas Production Company, Absheron peninsula, Baku, Azerbaijan). In the present work the results of emission spectra of crude oils taken from different regions of Absheron peninsula as well as the emission spectra of the oil spills on the surface of Caspian sea will be reported and discussed. These measurements open perspectives for using developed LIDAR for determination of place of oil-gas production company from which leakage takes place.

Rogue waves and large deviations in deep sea.

PubMed

Dematteis, Giovanni; Grafke, Tobias; Vanden-Eijnden, Eric

2018-01-30

The appearance of rogue waves in deep sea is investigated by using the modified nonlinear Schrödinger (MNLS) equation in one spatial dimension with random initial conditions that are assumed to be normally distributed, with a spectrum approximating realistic conditions of a unidirectional sea state. It is shown that one can use the incomplete information contained in this spectrum as prior and supplement this information with the MNLS dynamics to reliably estimate the probability distribution of the sea surface elevation far in the tail at later times. Our results indicate that rogue waves occur when the system hits unlikely pockets of wave configurations that trigger large disturbances of the surface height. The rogue wave precursors in these pockets are wave patterns of regular height, but with a very specific shape that is identified explicitly, thereby allowing for early detection. The method proposed here combines Monte Carlo sampling with tools from large deviations theory that reduce the calculation of the most likely rogue wave precursors to an optimization problem that can be solved efficiently. This approach is transferable to other problems in which the system's governing equations contain random initial conditions and/or parameters.

Speleothem records of western Mediterranean. Hydrological variability along the Last Interglacial Period and marine linkages

NASA Astrophysics Data System (ADS)

Torner, Judit; Cacho, Isabel; Moreno, Ana; Stoll, Heather; Belmonte, Anchel; Sierro, Francisco J.; Frigola, Jaime; Martrat, Belen; Fornós, Joan; Arnau Fernández, Pedro; Hellstrom, John; Cheng, Hai; Edwards, R. Lawrence

2016-04-01

This study aims to identify and characterize regional hydrological variability in the western Mediterranean region in base to different geochemical parameters (δ18O, δ13C, and Mg/Ca ratios). Speleothems have been recovered from several caves located in southern central Pyrenees one and the others form the Balearic Islands. Their chronologies have been constructed in base on U/Th absolute dating and indicate that the speleothem sequences cover the end of the last interglacial and the glacial inception. One of the most remarkable features of the records is the intense and abrupt shift toward more arid conditions that marks the end of the last interglacial (MIS 5e). Furthermore, our speleothem records also show relatively humid but highly variable hydrological conditions during the interstadial periods from MIS 5c to 5a. These speleothem records have been compared with new generated western Mediterranean marine records from the Balearic Sea (MD99-2343) and Alboran Sea (OPD-977). Marine records include (1) proxies of sea surface temperature and changes in evaporation-precipitation rates based on pair analysis of δ18O and the Mg/Ca ratios in planktonic foraminifera Globigerina bulloides; (2) proxies of deep-water currents associated with the Western Mediterranean Deep Water (WMDW) based on grain size analyses. The results reveal that arid conditions on land were coeval with cold sea surface sub-stages (MIS 5b and 5d), and also with increases in the intensity of the WMDW-related currents. By contrast, humid and hydrological unstable atmosphere conditions were synchronous with sea surface warm sub-stages, and lower WMDW-related currents intensities (MIS 5a, c and e). Consequently, our results highly evidence a strong atmospheric-oceanic coupling, involving parallel changes in both surface but also deep western Mediterranean Sea conditions during the last interglacial period and the glacial inception.

Remote sensing observations of phytoplankton increases triggered by successive typhoons

NASA Astrophysics Data System (ADS)

Huang, Lei; Zhao, Hui; Pan, Jiayi; Devlin, Adam

2017-12-01

Phytoplankton blooms in the Western North Pacific, triggered by two successive typhoons with different intensities and translation speeds under different pre-existing oceanic conditions, were observed and analyzed using remotely sensed chlorophyll-a (Chl-a), sea surface temperature (SST), and sea surface height anomaly (SSHA) data, as well as typhoon parameters and CTD (conductivity, temperature, and depth) profiles. Typhoon Sinlaku, with relatively weaker intensity and slower translation speed, induced a stronger phytoplankton bloom than Jangmi with stronger intensity and faster translation speed (Chl-a>0.18 mg·m‒3 versus Chl-a<0.15 mg·m‒3) east of Taiwan Island. Translation speed may be one of the important mechanisms that affect phytoplankton blooms in the study area. Pre-existing cyclonic circulations provided a relatively unstable thermodynamic structure for Sinlaku, and therefore cold water with rich nutrients could be brought up easily. The mixed-layer deepening caused by Typhoon Sinlaku, which occurred first, could have triggered an unfavorable condition for the phytoplankton bloom induced by Typhoon Jangmi which followed afterwards. The sea surface temperature cooling by Jangmi was suppressed due to the presence of the thick upper-ocean mixed-layer, which prevented the deeper cold water from being entrained into the upper-ocean mixed layer, leading to a weaker phytoplankton augment. The present study suggests that both wind (including typhoon translation speed and intensity) and pre-existing conditions (e.g., mixed-layer depths, eddies, and nutrients) play important roles in the strong phytoplankton bloom, and are responsible for the stronger phytoplankton bloom after Sinlaku's passage than that after Jangmi's passage. A new typhoon-influencing parameter is introduced that combines the effects of the typhoon forcing (including the typhoon intensity and translation speed) and the oceanic pre-condition. This parameter shows that the forcing effect of Sinlaku was stronger than that of Jangmi.

Assimilation of Sea Color Data Into A Three Dimensional Biogeochemical Model: Sensitivity Experiments

NASA Astrophysics Data System (ADS)

Echevin, V.; Levy, M.; Memery, L.

The assimilation of two dimensional sea color data fields into a 3 dimensional coupled dynamical-biogeochemical model is performed using a 4DVAR algorithm. The biogeochemical model includes description of nitrates, ammonium, phytoplancton, zooplancton, detritus and dissolved organic matter. A subset of the biogeochemical model poorly known parameters (for example,phytoplancton growth, mortality,grazing) are optimized by minimizing a cost function measuring misfit between the observations and the model trajectory. Twin experiments are performed with an eddy resolving model of 5 km resolution in an academic configuration. Starting from oligotrophic conditions, an initially unstable baroclinic anticyclone splits into several eddies. Strong vertical velocities advect nitrates into the euphotic zone and generate a phytoplancton bloom. Biogeochemical parameters are perturbed to generate surface pseudo-observations of chlorophyll,which are assimilated in the model in order to retrieve the correct parameter perturbations. The impact of the type of measurement (quasi-instantaneous, daily mean, weekly mean) onto the retrieved set of parameters is analysed. Impacts of additional subsurface measurements and of errors in the circulation are also presented.

Distribution Patterns of Microbial Community Structure Along a 7000-Mile Latitudinal Transect from the Mediterranean Sea Across the Atlantic Ocean to the Brazilian Coastal Sea.

PubMed

Zhou, Jin; Song, Xiao; Zhang, Chun-Yun; Chen, Guo-Fu; Lao, Yong-Min; Jin, Hui; Cai, Zhong-Hua

2018-02-14

A central goal in marine microecology is to understand the ecological factors shaping spatiotemporal microbial patterns and the underlying processes. We hypothesized that abiotic and/or biotic interactions are probably more important for explaining the distribution patterns of marine bacterioplankton than environmental filtering. In this study, surface seawater samples were collected about 7000 miles from the Mediterranean Sea, transecting the North Atlantic Ocean, to the Brazilian marginal sea. In bacterial biosphere, SAR11, SAR86, Rhodobacteraceae, and Rhodospiriaceae were predominant in the Mediterranean Sea; Prochlorococcus was more frequent in Atlantic Ocean; whereas in the Brazilian coastal sea, the main bacterial members were Synechococcus and SAR11. With respect to archaea, Euryarchaeota were predominant in the Atlantic Ocean and Thaumarchaeota in the Mediterranean Sea. With respect to the eukaryotes, Syndiniales, Spumellaria, Cryomonadida, and Chlorodendrales were predominant in the open ocean, while diatoms and microzooplankton were dominant in the coastal sea. Distinct clusters of prokaryotes and eukaryotes displayed clear spatial heterogeneity. Among the environmental parameters measured, temperature and salinity were key factors controlling bacterial and archaeal community structure, respectively, whereas N/P/Si contributed to eukaryotic variation. The relative contribution of environmental parameters to the microbial distribution pattern was 45.2%. Interaction analysis showed that Gammaproteobacteria, Alphaproteobacteria, and Flavobacteriia were the keystone taxa within the positive-correlation network, while Thermoplasmata was the main contributor in the negative-correlation network. Our study demonstrated that microbial communities are co-governed by environmental filtering and biotic interactions, which are the main deterministic driving factors modulating the spatiotemporal patterns of marine plankton synergistically at the regional or global levels.

The distribution and utility of sea-level indicators in Eurasian sub-Arctic salt marshes (White Sea, Russia).

NASA Astrophysics Data System (ADS)

Nikitina, Daria; Kemp, Andrew; Horton, Benjamin; Van, Christopher; Potapova, Marina; Culver, Stephen; Repkina, Tatyana; Hill, David

2017-04-01

We investigated the utility of foraminifera, diatoms and bulk-sediment geochemistry (δ13C and parameters measured by RockEval pyrolysis) as sea-level indicators in Eurasian sub-Arctic salt marshes. At three salt marshes in Dvina Bay (White Sea, Russia), we collected surface sediment samples along transects sequentially crossing sub-tidal, tidal-flat, salt-marsh and Taiga forest environments. Foraminifera formed bipartite assemblages, where elevations below mean high higher water (MHHW) were dominated by Miliammina spp. and elevations between MHHW and the highest occurrence of foraminifera were dominated by Jadammina macrescens and Balticammina pseudomacrescens. Both assemblages existed on all three transects and we conclude that foraminifera are sea-level indicators in Eurasian sub-Arctic salt marshes. Five, high-diversity groups of diatoms were identified and they displayed geographic variability among the study sites (<15 km apart). RockEval pyrolysis and δ13C measurements recognized two groups (clastic-dominated environments below MHHW and organic-rich environments above MHHW). Since one group included sub-tidal elevations and the other supra-tidal elevations, we conclude that the measured geochemical parameters do not meet the criteria for being stand-alone sea-level indicators. Core JT2012 captured a regressive sediment sequence of clastic, tidal-flat sediment overlain by salt-marsh organic silt and freshwater peat. The salt-marsh sediment accumulated at 2804 ± 52 years BP years before present and preserved foraminifera (J. macrescens and B. pseudomacrescens) with a high degree of analogy to modern assemblages indicating that relative sea level was 2.60 ± 0.47 m above present at this time. Diatoms confirm that marine influence decreased through time, but the lack of analogy between modern and core assemblages limits their utility as sea-level indicators in this setting.

Sensitivity study of a dynamic thermodynamic sea ice model

NASA Astrophysics Data System (ADS)

Holland, David M.; Mysak, Lawrence A.; Manak, Davinder K.; Oberhuber, Josef M.

1993-02-01

A numerical simulation of the seasonal sea ice cover in the Arctic Ocean and the Greenland, Iceland, and Norwegian seas is presented. The sea ice model is extracted from Oberhuber's (1990) coupled sea ice-mixed layer-isopycnal general circulation model and is written in spherical coordinates. The advantage of such a model over previous sea ice models is that it can be easily coupled to either global atmospheric or ocean general circulation models written in spherical coordinates. In this model, the thermodynamics are a modification of that of Parkinson and Washington (1979), while the dynamics use the full Hibler (1979) viscous-plastic rheology. Monthly thermodynamic and dynamic forcing fields for the atmosphere and ocean are specified. The simulations of the seasonal cycle of ice thickness, compactness, and velocity, for a control set of parameters, compare favorably with the known seasonal characteristics of these fields. A sensitivity study of the control simulation of the seasonal sea ice cover is presented. The sensitivity runs are carried out under three different themes, namely, numerical conditions, parameter values, and physical processes. This last theme refers to experiments in which physical processes are either newly added or completely removed from the model. Approximately 80 sensitivity runs have been performed in which a change from the control run environment has been implemented. Comparisons have been made between the control run and a particular sensitivity run based on time series of the seasonal cycle of the domain-averaged ice thickness, compactness, areal coverage, and kinetic energy. In addition, spatially varying fields of ice thickness, compactness, velocity, and surface temperature for each season are presented for selected experiments. A brief description and discussion of the more interesting experiments are presented. The simulation of the seasonal cycle of Arctic sea ice cover is shown to be robust.

Abrupt warming of the Red Sea

NASA Astrophysics Data System (ADS)

Raitsos, D. E.; Hoteit, I.; Prihartato, P. K.; Chronis, T.; Triantafyllou, G.; Abualnaja, Y.

2011-07-01

Coral reef ecosystems, often referred to as “marine rainforests,” concentrate the most diverse life in the oceans. Red Sea reef dwellers are adapted in a very warm environment, fact that makes them vulnerable to further and rapid warming. The detection and understanding of abrupt temperature changes is an important task, as ecosystems have more chances to adapt in a slowly rather than in a rapid changing environment. Using satellite derived sea surface and ground based air temperatures, it is shown that the Red Sea is going through an intense warming initiated in the mid-90s, with evidence for an abrupt increase after 1994 (0.7°C difference pre and post the shift). The air temperature is found to be a key parameter that influences the Red Sea marine temperature. The comparisons with Northern Hemisphere temperatures revealed that the observed warming is part of global climate change trends. The hitherto results also raise additional questions regarding other broader climatic impacts over the area.

Physicochemical signatures of natural surfactant sea films from coastal Middle Adriatic stations

NASA Astrophysics Data System (ADS)

Frka, Sanja; Pogorzelski, Stanislaw; Kozarac, Zlatica; Ćosović, Božena

2013-04-01

Boundary layers between different environmental compartments represent critical interfaces for biological, chemical and physical processes. The sea surface microlayer (SSM) as a top layer of the sea surface represents natural interface between the atmosphere and ocean. Although < 1 mm in thickness the SML plays a key role in the global biogeochemical cycling because all gaseous, liquid and particulate materials must pass through this interface when exchanging between the ocean and the atmosphere. The SSM thus represents a very important driver enhancing air-water exchange processes. A variety of natural and anthropogenic organic compounds, particularly those which are surface active (SA) are generally enriched in the SML. It is widely acknowledged that the SSM is complex matrix of SA organics as carbohydrates, proteins, lipids and humic substances. Although lipid material is much less abundant than carbohydrates and proteins in the SML, their contribution to surface activity may be disproportionately large. The surfactant films at the air-sea interface change its physicochemical properties reducing air-sea exchange possesses by impeding molecular diffusion across the interface and influencing the hydrodynamic characteristics of water motion at the interface. Various biological, chemical and physical processes lead to the alteration of the film chemical composition, surface physical properties, surface concentration and spatial distribution of film-forming components. Instead of analyzing its chemical composition, it should be possible to scale the SML surface pressure-area (π-A) isotherms in terms of structural parameters which appear to be a sensitive and quantitative measure of the film physicochemical composition, surface concentration and miscibility of its film-forming components. We will present a large data set obtained by electrochemical and monolayer techniques, accompanied with the novel scaling approach for physicochemical characterization of SA substances of the natural microlayers from coastal Middle Adriatic stations including saline Rogoznica Lake and Krka river estuarine station. Higher primary production during late spring-early autumn is reflected in the presence of microlayers of higher surfactant activity containing on average molecules of lower molecular masses (Mw=0.65±0.27 kDa) and higher miscibility (y=6.46±1.33) and elasticity (E=18.33±2.02 mN/m) modulus in comparison to structural parameters (average Mw=2.15±1.58 kDa; y=3.51±1.46; E=6.41±1.97 mN/m) obtained for microlayers from period of lower organic matter production. Higher inhibition effect on the reduction process of cadmium ions is observed for natural microlayers abundant with SA material from more productive period. This kind of distribution is explained as the consequence of competitive adsorption of hydrophobic lipid-like substances of lower Mw which highly influence the surface structural properties of natural air-water interface forming there segregated surface films during more productive period. This study will offer different perspective on contemporary SML concept taking into account the lipids that act as end-members highly influencing seasonal change of SA concentration and surface structural properties of natural films at the air-water interface.

Sea Surface Temperature and Ocean Color Variability in the South China Sea

NASA Astrophysics Data System (ADS)

Conaty, A. P.

2001-12-01

The South China Sea is a marginal sea in the Southeast Asian region whose surface circulation is driven by monsoons and whose surface currents have complex seasonal patterns. Its rich natural resources and strategic location have made its small islands areas of political dispute among the neighboring nations. This study aims to show the seasonal and interannual variability of sea surface temperature and ocean color in South China Sea. It makes use of NOAA's Advanced Very High Resolution Radiometer (AVHRR) satellite data sets on sea surface temperature for the period 1981-2000 and NASA's Nimbus-7 Coastal Zone Color Scanner (CZCS) and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite data sets on pigment concentration (ocean color) for the period 1981-1996 and 1997-2000, respectively. Transect lines were drawn along several potential hotspot areas to show the variability in sea surface temperature and pigment concentration through time. In-situ data on sea surface temperature along South China Sea were likewise plotted to see the variability with time. Higher seasonal variability in sea surface temperature was seen at higher latitudes. Interannual variability was within 1-3 Kelvin. In most areas, pigment concentration was higher during northern hemisphere winter and autumn, after the monsoon rains, with a maximum of 30 milligrams per cubic meter.

The effect of artificial rain on backscattered acoustic signal: first measurements

NASA Astrophysics Data System (ADS)

Titchenko, Yuriy; Karaev, Vladimir; Meshkov, Evgeny; Goldblat, Vladimir

The problem of rain influencing on a characteristics of backscattered ultrasonic and microwave signal by water surface is considered. The rain influence on backscattering process of electromagnetic waves was investigated in laboratory and field experiments, for example [1-3]. Raindrops have a significant impact on backscattering of microwave and influence on wave spectrum measurement accuracy by string wave gauge. This occurs due to presence of raindrops in atmosphere and modification of the water surface. For measurements of water surface characteristics during precipitation we propose to use an acoustic system. This allows us obtaining of the water surface parameters independently on precipitation in atmosphere. The measurements of significant wave height of water surface using underwater acoustical systems are well known [4, 5]. Moreover, the variance of orbital velocity can be measure using these systems. However, these methods cannot be used for measurements of slope variance and the other second statistical moments of water surface that required for analyzing the radar backscatter signal. An original design Doppler underwater acoustic wave gauge allows directly measuring the surface roughness characteristics that affect on electromagnetic waves backscattering of the same wavelength [6]. Acoustic wave gauge is Doppler ultrasonic sonar which is fixed near the bottom on the floating disk. Measurements are carried out at vertically orientation of sonar antennas towards water surface. The first experiments were conducted with the first model of an acoustic wave gauge. The acoustic wave gauge (8 mm wavelength) is equipped with a transceiving antenna with a wide symmetrical antenna pattern. The gauge allows us to measure Doppler spectrum and cross section of backscattered signal. Variance of orbital velocity vertical component can be retrieved from Doppler spectrum with high accuracy. The result of laboratory and field experiments during artificial rain is presented. The estimates of roughness parameters variability during precipitation are obtained. The first measurements of rain influencing on cross section and Doppler spectrum of backscattered acoustic signal was carried out. The obtained results were compared with calculations based on the theoretical model. Acknowledgments. The reported study was supported by RFBR, research project No. 14-05-31517 mol_a. References 1. Bliven Larry, Branger Hubert, Sobieski Piotr, Giovanangeli Jean-Paul, An analysis of scatterometer returns from a water surface agitated by artificial rain : evidence that ring-waves are the mean feature, Intl. Jl. of Remote Sensing, Vol. 14, n 12, 1993, pp. 2315-2329, 1993 2. Sobieski Piotr, Craeye Christophe, Bliven Larry, A Relationship Between Rain Radar Reflectivity and Height Elevation Variance of Ringwaves due to the Impact of Rain on the Sea Surface, Radio Science, AGU, 44, RS3005, 1-20, 2009 3. Weissman, D. E., and M. A. Bourassa, Measurements of the Effect of Rain-induced Sea Surface Roughness on the Satellite Scatterometer Radar Cross Section, IEEE Trans. Geosci. Remote Sens., 46, 2882-2894, 2008 4. B. Brumley, La Jolla, E.Terray, B.String, «System and method for measuring wave directional spectrum and wave height», USA Patent N US 2004/0184350 A1,23 September 2004 5. James H. Churchill, Albert J. Plueddemann, Stephen M. Faluotico, «Extracting Wind Sea and Swell from Directional Wave Spectra derived from a bottom-mounted ADCP», Woods Hole Oceanographic Institution, Technical Report WHOI-2006-13 6. V. Yu. Karaev, M. B. Kanevsky, E. M. Meshkov, Measuring the parameters of sea-surface roughness by underwater acoustic systems: discussion of the device concept, Radiophysics and Quantum Electronics, V. 53, I. 9-10. pp. 569-579, 2011

Diversity and community structure of pelagic cnidarians in the Celebes and Sulu Seas, southeast Asian tropical marginal seas

NASA Astrophysics Data System (ADS)

Grossmann, Mary M.; Nishikawa, Jun; Lindsay, Dhugal J.

2015-06-01

The Sulu Sea is a semi-isolated, marginal basin surrounded by high sills that greatly reduce water inflow at mesopelagic depths. For this reason, the entire water column below 400 m is stable and homogeneous with respect to salinity (ca. 34.00) and temperature (ca. 10 °C). The neighbouring Celebes Sea is more open, and highly influenced by Pacific waters at comparable depths. The abundance, diversity, and community structure of pelagic cnidarians was investigated in both seas in February 2000. Cnidarian abundance was similar in both sampling locations, but species diversity was lower in the Sulu Sea, especially at mesopelagic depths. At the surface, the cnidarian community was similar in both marginal seas, but, at depth, community structure was dependent first on sampling location and then on depth within each Sea. Cnidarians showed different patterns of dominance at the two sampling locations, with Sulu Sea communities often dominated by species that are rare elsewhere in the Indo-Pacific. Mesopelagic and bathypelagic species recorded in the Sulu Sea did not have significantly different vertical distributions in the Celebes Sea. However, some deep mesopelagic genera were absent from the Sulu Sea in the sampled depth range. These results suggest that a combination of environmental and physiological parameters determine the distribution and dominance of pelagic cnidarians.

Climatology of Global Swell-Atmosphere Interaction

NASA Astrophysics Data System (ADS)

Semedo, Alvaro

2016-04-01

At the ocean surface wind sea and swell waves coexist. Wind sea waves are locally generated growing waves strongly linked to the overlaying wind field. Waves that propagate away from their generation area, throughout entire ocean basins, are called swell. Swell waves do not receive energy from local wind. Ocean wind waves can be seen as the "gearbox" between the atmosphere and the ocean, and are of critical importance to the coupled atmosphere-ocean system, since they modulate most of the air-sea interaction processes and exchanges, particularly the exchange of momentum. This modulation is most of the times sea-state dependent, i.e., it is a function of the prevalence of one type of waves over the other. The wave age parameter, defined as the relative speed between the peak wave and the wind (c_p⁄U_10), has been largely used in different aspects of the air-sea interaction theory and in practical modeling solutions of wave-atmosphere coupled model systems. The wave age can be used to assess the development of the sea state but also the prevalence (domination) of wind sea or swell waves at the ocean surface. The presence of fast-running waves (swell) during light winds (at high wave age regimes) induces an upward momentum flux, directed from the water surface to the atmosphere. This upward directed momentum has an impact in the lower marine atmospheric boundary layer (MABL): on the one hand it changes the vertical wind speed profile by accelerating the flow at the first few meters (inducing the so called "wave-driven wind"), and on the other hand it changes the overall MABL turbulence structure by limiting the wind shear - in some observed and modeled situations the turbulence is said to have "collapse". The swell interaction with the lower MABL is a function of the wave age but also of the swell steepness, since steeper waves loose more energy into the atmosphere as their energy attenuates. This interaction can be seen as highest in areas where swells are steepest, but also where the wind speed is lowest and consequently the wave age is high. A detailed global climatology of the wave age and swell steepness parameters, based on the ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-Interim reanalysis is presented. It will be shown, in line with previous studies, that the global climatological patterns of the wave age confirm the global dominance of the World Ocean by swell waves. The areas of the ocean where the highest interaction of swell waves and the lower atmosphere can be expected are also presented.

Statistical approaches for studying the wave climate of crossing-sea states

NASA Astrophysics Data System (ADS)

Barbariol, Francesco; Portilla, Jesus; Benetazzo, Alvise; Cavaleri, Luigi; Sclavo, Mauro; Carniel, Sandro

2017-04-01

Surface waves are an important feature of the world's oceans and seas. Their role in the air-sea exchanges is well recognized, together with their effects on the upper ocean and lower atmosphere dynamics. Physical processes involving surface waves contribute in driving the Earth's climate that, while experiencing changes at global and regional scales, in turn affects the surface waves climate over the oceans. The assessment of the wave climate at specific locations of the ocean is fruitful for many research fields in marine and atmospheric sciences and also for the human activities in the marine environment. Very often, wind generated waves (wind-sea) and one or more swell systems occur simultaneously, depending on the complexity of the atmospheric conditions that force the waves. Therefore, a wave climate assessed from the statistical analysis of long time series of integral wave parameters, can hardly say something about the frequency of occurrence of the so-called crossing-seas, as well as of their features. Directional wave spectra carry such information but proper statistical methods to analyze them are needed. In this respect, in order to identify the crossing sea states within the spectral time series and to assess their frequency of occurrence we exploit two advanced statistical techniques. First, we apply the Spectral Partitioning, a well-established method based on a two-step partitioning of the spectrum that allows to identify the individual wave systems and to compute their probability of occurrence in the frequency/direction space. Then, we use the Self-Organizing Maps, an unsupervised neural network algorithm that quantize the time series by autonomously identifying an arbitrary (small) number of wave spectra representing the whole wave climate, each with its frequency of occurrence. This method has been previously applied to time series of wave parameters and for the first time is applied to directional wave spectra. We analyze the wave climate of one of the most severe regions of the Mediterranean Sea, between north-west Sardinia and the Gulf of Lion, where quite often wave systems coming from different directions superpose. Time series for the analysis is taken from the ERA-Interim Reanalysis dataset, which provides global directional wave spectra at 1° resolution, starting from 1979 up to the present. Results from the two techniques are shown to be consistent, and their comparison points out the contribution that each technique can provide for a more detailed interpretation of the wave climate.

Influences of terrestrial inorganic carbon on carbonate system in China Seas and the implication for China Seas' vulnerabilities to potentially negative effects of ocean acidification

NASA Astrophysics Data System (ADS)

Guo, X.; Zhai, W. D.; Guo, L. G.; Jiang, Z. P.; Qi, D.; Xu, Y.; Huang, X.

2017-12-01

We investigated sea surface carbonate system and ancillary parameters in the northern South China Sea (SCS), East China Sea (ECS), Yellow Sea, and Bohai Sea during a single cruise from late April to June 2011. In this transitional season between the dry/cold and wet/warm seasons, we observed ubiquitous terrestrial inorganic carbon signals in the Yellow Sea and Bohai Sea, as indicated by excess total alkalinity (TAlk) from 150 to 450 μmol kg-1 and excess Ca concentrations from 100 to 470 μmol kg-1, associated with relatively high DIC/TAlk ratios from 0.88 to 0.92. In contrast, these terrestrial inorganic carbon signals were limited to nearshore areas in the southern ECS and northern SCS. These results suggested that the Yellow Sea and Bohai Sea were dominated by terrestrial inputs all over the year, while the terrestrial signals in the southern ECS and northern SCS were highly diminished in dry seasons through water mixing with open ocean waters (likely introduced by Kuroshio). This study also showed that the terrestrial inorganic carbon inputs had diminished carbonate ion concentrations and CaCO3 saturation states in the Yellow Sea and Bohai Sea. This may contribute to recent findings that the North Yellow Sea represents one of the systems in the China seas most vulnerable to the potentially negative effects of ocean acidification.

Sensitivity of grounding line dynamics to viscoelastic deformation of the solid Earth: Inferences from a fully coupled ice sheet - solid Earth model

NASA Astrophysics Data System (ADS)

Konrad, H.; Sasgen, I.; Thoma, M.; Klemann, V.; Grosfeld, K.; Martinec, Z.

2013-12-01

The interactions of ice sheets with the sea level and the solid Earth are important factors for the stability of the ice shelves and the tributary inland ice (e.g. Thomas and Bentley, 1978; Gomez et al, 2012). First, changes in ice extent and ice thickness induce viscoelastic deformation of the Earth surface and Earth's gravity field. In turn, global and local changes in sea level and bathymetry affect the grounding line and, subsequently, alter the ice dynamic behaviour. Here, we investigate these feedbacks for a synthetic ice sheet configuration as well as for the Antarctic ice sheet using a three-dimensional thermomechanical ice sheet and shelf model, coupled to a viscoelastic solid-Earth and gravitationally self-consistent sea-level model. The respective ice sheet undergoes a forcing from rising sea level, warming ocean, and/or changing surface mass balance. The coupling is realized by exchanging ice thickness, Earth surface deformation, and sea level periodically. We apply several sets of viscoelastic Earth parameters to our coupled model, e.g. simulating a low-viscous upper mantle present at the Antarctic Peninsula (Ivins et al., 2011). Special focus of our study lies on the evolution of Earth surface deformation and local sea level changes, as well as on the accompanying grounding line evolution. N. Gomez, D. Pollard, J. X. Mitrovica, P. Huybers, and P. U. Clark 2012. Evolution of a coupled marine ice sheet-sea level model, J. Geophys. Res., 117, F01013, doi:10.1029/2011JF002128. E. R. Ivins, M. M. Watkins, D.-N. Yuan, R. Dietrich, G. Casassa, and A. Rülke 2011. On-land ice loss and glacial isostatic adjustment at the Drake Passage: 2003-2009, J. Geophys. Res. 116, B02403, doi: 10.1029/2010JB007607 R. H. Thomas and C. R. Bentley 1978. A model for Holocene retreat of the West Antarctic Ice Sheet, Quaternary Research, 10 (2), pages 150-170, doi: 10.1016/0033-5894(78)90098-4.

A model of air-sea gas exchange incorporating the physics of the turbulent boundary layer and the properties of the sea surface

NASA Astrophysics Data System (ADS)

Soloviev, Alexander; Schluessel, Peter

The model presented contains interfacial, bubble-mediated, ocean mixed layer, and remote sensing components. The interfacial (direct) gas transfer dominates under conditions of low and—for quite soluble gases like CO2—moderate wind speeds. Due to the similarity between the gas and heat transfer, the temperature difference, ΔT, across the thermal molecular boundary layer (cool skin of the ocean) and the interfacial gas transfer coefficient, Kint are presumably interrelated. A coupled parameterization for ΔT and Kint has been derived in the context of a surface renewal model [Soloviev and Schluessel, 1994]. In addition to the Schmidt, Sc, and Prandtl, Pr, numbers, the important parameters are the surface Richardson number, Rƒ0, and the Keulegan number, Ke. The more readily available cool skin data are used to determine the coefficients that enter into both parameterizations. At high wind speeds, the Ke-number dependence is further verified with the formula for transformation of the surface wind stress to form drag and white capping, which follows from the renewal model. A further extension of the renewal model includes effects of solar radiation and rainfall. The bubble-mediated component incorporates the Merlivat et al. [1993] parameterization with the empirical coefficients estimated by Asher and Wanninkhof [1998]. The oceanic mixed layer component accounts for stratification effects on the air-sea gas exchange. Based on the example of GasEx-98, we demonstrate how the results of parameterization and modeling of the air-sea gas exchange can be extended to the global scale, using remote sensing techniques.

Community composition of ammonia-oxidizing archaea from surface and anoxic depths of oceanic oxygen minimum zones.

PubMed

Peng, Xuefeng; Jayakumar, Amal; Ward, Bess B

2013-01-01

Ammonia-oxidizing archaea (AOA) have been reported at high abundance in much of the global ocean, even in environments, such as pelagic oxygen minimum zones (OMZs), where conditions seem unlikely to support aerobic ammonium oxidation. Due to the lack of information on any potential alternative metabolism of AOA, the AOA community composition might be expected to differ between oxic and anoxic environments. This hypothesis was tested by evaluating AOA community composition using a functional gene microarray that targets the ammonia monooxygenase gene subunit A (amoA). The relationship between environmental parameters and the biogeography of the Arabian Sea and the Eastern Tropical South Pacific (ETSP) AOA assemblages was investigated using principal component analysis (PCA) and redundancy analysis (RDA). In both the Arabian Sea and the ETSP, AOA communities within the core of the OMZ were not significantly different from those inhabiting the oxygenated surface waters above the OMZ. The AOA communities in the Arabian Sea were significantly different from those in the ETSP. In both oceans, the abundance of archaeal amoA gene in the core of the OMZ was higher than that in the surface waters. Our results indicate that AOA communities are distinguished by their geographic origin. RDA suggested that temperature (higher in the Arabian Sea than in the ETSP) was the main factor that correlated with the differences between the AOA communities. Physicochemical properties that characterized the different environments of the OMZ and surface waters played a less important role, than did geography, in shaping the AOA community composition.

Climate in the absence of ocean heat transport

NASA Astrophysics Data System (ADS)

Rose, B. E. J.

2017-12-01

The energy transported by the oceans to mid- and high latitudes is small compared to the atmosphere, yet exerts an outsized influence on climate. A key reason is the strong interaction between ocean heat transport (OHT) and sea ice extent. I quantify the absolute climatic impact of OHT using the state-of-the-art CESM simulations by comparing a realistic control climate against a slab ocean simulation in which OHT is disabled. The absence of OHT leads to a massive expansion of sea ice into the subtropics in both hemispheres, and a 24 K global cooling. Analysis of the transient simulation after setting the OHT to zero reveals a global cooling process fueled by a runaway sea ice albedo feedback. This process is eventually self-limiting in the cold climate due to a combination of subtropical cloud feedbacks and surface wind effects that are both connected to a massive spin-up of the atmospheric Hadley circulation. A parameter sensitivity study shows that the simulated climate is far more sensitive to small changes in ice surface albedo in the absence of OHT. I conclude that the oceans are responsible for an enormous global warming by mitigating an otherwise very potent sea ice albedo feedback, but that the magnitude of this effect is rather uncertain. These simulations provide a graphic illustration of how the intimate coupling between sea ice and ocean circulation governs the present-day climate, and by extension, highlight the importance of modeling ocean - sea ice interaction with high fidelity.

Polarization Rotation and the Third Stokes Parameter: The Effects of Spacecraft Attitude and Faraday Rotation

NASA Technical Reports Server (NTRS)

Meissner, Thomas; Wentz, Frank J.

2006-01-01

The third Stokes parameter of ocean surface brightness temperatures measured by the WindSat instrument is sensitive to the rotation angle between the polarization vectors at the ocean surface and the instrument. This rotation angle depends on the spacecraft attitude (roll, pitch, yaw) as well as the Faraday rotation of the electromagnetic radiation passing through the Earth's ionosphere. Analyzing the WindSat antenna temperatures, we find biases in the third Stokes parameter as function of the along-scan position of up to 1.5 K in all feedhorns. This points to a misspecification of the reported spacecraft attitude. A single attitude correction of -0.16deg roll and 0.18deg pitch for the whole instrument eliminates all the biases. We also study the effect of Faraday rotation at 10.7 GHz on the accuracy of the third Stokes parameter and the sea surface wind direction retrieval and demonstrate how this error can be corrected using values from the International Reference Ionosphere for the total electron content when computing Faraday rotation.

Subsurface Scattered Photons: Friend or Foe? Improving visible light laser altimeter elevation estimates, and measuring surface properties using subsurface scattered photons

NASA Astrophysics Data System (ADS)

Greeley, A.; Kurtz, N. T.; Neumann, T.; Cook, W. B.; Markus, T.

2016-12-01

Photon counting laser altimeters such as MABEL (Multiple Altimeter Beam Experimental Lidar) - a single photon counting simulator for ATLAS (Advanced Topographical Laser Altimeter System) - use individual photons with visible wavelengths to measure their range to target surfaces. ATLAS, the sole instrument on NASA's upcoming ICESat-2 mission, will provide scientists a view of Earth's ice sheets, glaciers, and sea ice with unprecedented detail. Precise calibration of these instruments is needed to understand rapidly changing parameters such as sea ice freeboard, and to measure optical properties of surfaces like snow covered ice sheets using subsurface scattered photons. Photons that travel through snow, ice, or water before scattering back to an altimeter receiving system travel farther than photons taking the shortest path between the observatory and the target of interest. These delayed photons produce a negative elevation bias relative to photons scattered directly off these surfaces. We use laboratory measurements of snow surfaces using a flight-tested laser altimeter (MABEL), and Monte Carlo simulations of backscattered photons from snow to estimate elevation biases from subsurface scattered photons. We also use these techniques to demonstrate the ability to retrieve snow surface properties like snow grain size.

Analysis of reactive bromine production and ozone depletion in the Arctic boundary layer using 3-D simulations with GEM-AQ: inference from synoptic-scale patterns

NASA Astrophysics Data System (ADS)

Toyota, K.; McConnell, J. C.; Lupu, A.; Neary, L.; McLinden, C. A.; Richter, A.; Kwok, R.; Semeniuk, K.; Kaminski, J. W.; Gong, S.-L.; Jarosz, J.; Chipperfield, M. P.; Sioris, C. E.

2011-04-01

Episodes of high bromine levels and surface ozone depletion in the springtime Arctic are simulated by an online air-quality model, GEM-AQ, with gas-phase and heterogeneous reactions of inorganic bromine species and a simple scheme of air-snowpack chemical interactions implemented for this study. Snowpack on sea ice is assumed to be the only source of bromine to the atmosphere and to be capable of converting relatively stable bromine species to photolabile Br2 via air-snowpack interactions. A set of sensitivity model runs are performed for April 2001 at a horizontal resolution of approximately 100 km×100 km in the Arctic, to provide insights into the effects of temperature and the age (first-year, FY, versus multi-year, MY) of sea ice on the release of reactive bromine to the atmosphere. The model simulations capture much of the temporal variations in surface ozone mixing ratios as observed at stations in the high Arctic and the synoptic-scale evolution of areas with enhanced BrO column amount ("BrO clouds") as estimated from satellite observations. The simulated "BrO clouds" are in modestly better agreement with the satellite measurements when the FY sea ice is assumed to be more efficient at releasing reactive bromine to the atmosphere than on the MY sea ice. Surface ozone data from coastal stations used in this study are not sufficient to evaluate unambiguously the difference between the FY sea ice and the MY sea ice as a source of bromine. The results strongly suggest that reactive bromine is released ubiquitously from the snow on the sea ice during the Arctic spring while the timing and location of the bromine release are largely controlled by meteorological factors. It appears that a rapid advection and an enhanced turbulent diffusion associated with strong boundary-layer winds drive transport and dispersion of ozone to the near-surface air over the sea ice, increasing the oxidation rate of bromide (Br-) in the surface snow. Also, if indeed the surface snowpack does supply most of the reactive bromine in the Arctic boundary layer, it appears to be capable of releasing reactive bromine at temperatures as high as -10 °C, particularly on the sea ice in the central and eastern Arctic Ocean. Dynamically-induced BrO column variability in the lowermost stratosphere appears to interfere with the use of satellite BrO column measurements for interpreting BrO variability in the lower troposphere but probably not to the extent of totally obscuring "BrO clouds" that originate from the surface snow/ice source of bromine in the high Arctic. A budget analysis of the simulated air-surface exchange of bromine compounds suggests that a "bromine explosion" occurs in the interstitial air of the snowpack and/or is accelerated by heterogeneous reactions on the surface of wind-blown snow in ambient air, both of which are not represented explicitly in our simple model but could have been approximated by a parameter adjustment for the yield of Br2 from the trigger.

Estimation of Melt Pond Fractions on First Year Sea Ice Using Compact Polarization SAR

NASA Astrophysics Data System (ADS)

Li, Haiyan; Perrie, William; Li, Qun; Hou, Yijun

2017-10-01

Melt ponds are a common feature on Arctic sea ice. They are linked to the sea ice surface albedo and transmittance of energy to the ocean from the atmosphere and thus constitute an important process to parameterize in Arctic climate models and simulations. This paper presents a first attempt to retrieve the melt pond fraction from hybrid-polarized compact polarization (CP) SAR imagery, which has wider swath and shorter revisit time than the quad-polarization systems, e.g., from RADARSAT-2 (RS-2). The co-polarization (co-pol) ratio has been verified to provide estimates of melt pond fractions. However, it is a challenge to link CP parameters and the co-pol ratio. The theoretical possibility is presented, for making this linkage with the CP parameter C22/C11 (the ratio between the elements of the coherence matrix of CP SAR) for melt pond detection and monitoring with the tilted-Bragg scattering model for the ocean surface. The empirical transformed formulation, denoted as the "compact polarization and quad-pol" ("CPQP") model, is proposed, based on 2062 RS-2 quad-pol SAR images, collocated with in situ measurements. We compared the retrieved melt pond fraction with CP parameters simulated from quad-pol SAR data with results retrieved from the co-pol ratio from quad-pol SAR observations acquired during the Arctic-Ice (Arctic-Ice Covered Ecosystem in a Rapidly Changing Environment) field project. The results are shown to be comparable for observed melt pond measurements in spatial and temporal distributions. Thus, the utility of CP mode SAR for melt pond fraction estimation on first year level ice is presented.

Sensitivity analysis of sea level rise contribution depending on external forcing: A case study of Victoria Land, East Antarctica.

NASA Astrophysics Data System (ADS)

Park, I. W.; Lee, S. H.; Lee, W. S.; Lee, C. K.; Lee, K. K.

2017-12-01

As global mean temperature increases, it affects increase in polar glacier melt and thermal expansion of sea, which contributed to global sea level rise. Unlike large sea level rise contributors in Western Antarctica (e. g. Pine island glacier, Thwaites glacier), glaciers in East Antarctica shows relatively stable and slow ice velocity. However, recent calving events related to increase of supraglacier lake in Nansen ice shelf arouse the questions in regards to future evolution of ice dynamics at Victoria Land, East Antarctica. Here, using Ice Sheet System Model (ISSM), a series of numerical simulations were carried out to investigate ice dynamics evolution (grounding line migration, ice velocity) and sea level rise contribution in response to external forcing conditions (surface mass balance, floating ice melting rate, and ice front retreat). In this study, we used control method to set ice dynamic properties (ice rigidity and friction coefficient) with shallow shelf approximation model and check each external forcing conditions contributing to sea level change. Before 50-year transient simulations were conducted based on changing surface mass balance, floating ice melting rate, and ice front retreat of Drygalski ice tongue and Nansen ice shelf, relaxation was performed for 10 years to reduce non-physical undulation and it was used as initial condition. The simulation results showed that sea level rise contribution were expected to be much less compared to other fast glaciers. Floating ice melting rate was most sensitive parameter to sea level rise, while ice front retreat of Drygalski tongue was negligible. The regional model will be further updated utilizing ice radar topography and measured floating ice melting rate.

The association of Antarctic krill Euphausia superba with the under-ice habitat.

PubMed

Flores, Hauke; van Franeker, Jan Andries; Siegel, Volker; Haraldsson, Matilda; Strass, Volker; Meesters, Erik Hubert; Bathmann, Ulrich; Wolff, Willem Jan

2012-01-01

The association of Antarctic krill Euphausia superba with the under-ice habitat was investigated in the Lazarev Sea (Southern Ocean) during austral summer, autumn and winter. Data were obtained using novel Surface and Under Ice Trawls (SUIT), which sampled the 0-2 m surface layer both under sea ice and in open water. Average surface layer densities ranged between 0.8 individuals m(-2) in summer and autumn, and 2.7 individuals m(-2) in winter. In summer, under-ice densities of Antarctic krill were significantly higher than in open waters. In autumn, the opposite pattern was observed. Under winter sea ice, densities were often low, but repeatedly far exceeded summer and autumn maxima. Statistical models showed that during summer high densities of Antarctic krill in the 0-2 m layer were associated with high ice coverage and shallow mixed layer depths, among other factors. In autumn and winter, density was related to hydrographical parameters. Average under-ice densities from the 0-2 m layer were higher than corresponding values from the 0-200 m layer collected with Rectangular Midwater Trawls (RMT) in summer. In winter, under-ice densities far surpassed maximum 0-200 m densities on several occasions. This indicates that the importance of the ice-water interface layer may be under-estimated by the pelagic nets and sonars commonly used to estimate the population size of Antarctic krill for management purposes, due to their limited ability to sample this habitat. Our results provide evidence for an almost year-round association of Antarctic krill with the under-ice habitat, hundreds of kilometres into the ice-covered area of the Lazarev Sea. Local concentrations of postlarval Antarctic krill under winter sea ice suggest that sea ice biota are important for their winter survival. These findings emphasise the susceptibility of an ecological key species to changing sea ice habitats, suggesting potential ramifications on Antarctic ecosystems induced by climate change.

The Association of Antarctic Krill Euphausia superba with the Under-Ice Habitat

PubMed Central

Flores, Hauke; van Franeker, Jan Andries; Siegel, Volker; Haraldsson, Matilda; Strass, Volker; Meesters, Erik Hubert; Bathmann, Ulrich; Wolff, Willem Jan

2012-01-01

The association of Antarctic krill Euphausia superba with the under-ice habitat was investigated in the Lazarev Sea (Southern Ocean) during austral summer, autumn and winter. Data were obtained using novel Surface and Under Ice Trawls (SUIT), which sampled the 0–2 m surface layer both under sea ice and in open water. Average surface layer densities ranged between 0.8 individuals m−2 in summer and autumn, and 2.7 individuals m−2 in winter. In summer, under-ice densities of Antarctic krill were significantly higher than in open waters. In autumn, the opposite pattern was observed. Under winter sea ice, densities were often low, but repeatedly far exceeded summer and autumn maxima. Statistical models showed that during summer high densities of Antarctic krill in the 0–2 m layer were associated with high ice coverage and shallow mixed layer depths, among other factors. In autumn and winter, density was related to hydrographical parameters. Average under-ice densities from the 0–2 m layer were higher than corresponding values from the 0–200 m layer collected with Rectangular Midwater Trawls (RMT) in summer. In winter, under-ice densities far surpassed maximum 0–200 m densities on several occasions. This indicates that the importance of the ice-water interface layer may be under-estimated by the pelagic nets and sonars commonly used to estimate the population size of Antarctic krill for management purposes, due to their limited ability to sample this habitat. Our results provide evidence for an almost year-round association of Antarctic krill with the under-ice habitat, hundreds of kilometres into the ice-covered area of the Lazarev Sea. Local concentrations of postlarval Antarctic krill under winter sea ice suggest that sea ice biota are important for their winter survival. These findings emphasise the susceptibility of an ecological key species to changing sea ice habitats, suggesting potential ramifications on Antarctic ecosystems induced by climate change. PMID:22384073

Time evolution of atmospheric parameters and their influence on sea level pressure over the head Bay of Bengal

NASA Astrophysics Data System (ADS)

Patra, Anindita; Bhaskaran, Prasad K.; Jose, Felix

2018-06-01

A zonal dipole in the observed trends of wind speed and significant wave height over the Head Bay of Bengal region was recently reported in the literature attributed due to the variations in sea level pressure (SLP). The SLP in turn is governed by prevailing atmospheric conditions such as local temperature, humidity, rainfall, atmospheric pressure, wind field distribution, formation of tropical cyclones, etc. The present study attempts to investigate the inter-annual variability of atmospheric parameters and its role on the observed zonal dipole trend in sea level pressure, surface wind speed and significant wave height. It reports on the aspects related to linear trend as well as its spatial variability for several atmospheric parameters: air temperature, geopotential height, omega (vertical velocity), and zonal wind, over the head Bay of Bengal, by analyzing National Centers for Environmental Prediction (NCEP) Reanalysis 2 dataset covering a period of 38 years (1979-2016). Significant warming from sea level to 200 mb pressure level and thereafter cooling above has been noticed during all the seasons. Warming within the troposphere exhibits spatial difference between eastern and western side of the domain. This led to fall in lower tropospheric geopotential height and its east-west variability, exhibiting a zonal dipole pattern across the Head Bay. In the upper troposphere, uplift in geopotential height was found as a result of cooling in higher levels (10-100 mb). Variability in omega also substantiated the observed variations in geopotential height. The study also finds weakening in the upper level westerlies and easterlies. Interestingly, a linear trend in lower tropospheric u-wind component also reveals an east-west dipole pattern over the study region. Further, the study corroborates the reported dipole in trends of sea level pressure, wind speed and significant wave height by evaluating the influence of atmospheric variability on these parameters.

From monsoon to marine productivity in the Arabian Sea: insights from glacial and interglacial climates

NASA Astrophysics Data System (ADS)

Le Mézo, Priscilla; Beaufort, Luc; Bopp, Laurent; Braconnot, Pascale; Kageyama, Masa

2017-07-01

The current-climate Indian monsoon is known to boost biological productivity in the Arabian Sea. This paradigm has been extensively used to reconstruct past monsoon variability from palaeo-proxies indicative of changes in surface productivity. Here, we test this paradigm by simulating changes in marine primary productivity for eight contrasted climates from the last glacial-interglacial cycle. We show that there is no straightforward correlation between boreal summer productivity of the Arabian Sea and summer monsoon strength across the different simulated climates. Locally, productivity is fuelled by nutrient supply driven by Ekman dynamics. Upward transport of nutrients is modulated by a combination of alongshore wind stress intensity, which drives coastal upwelling, and by a positive wind stress curl to the west of the jet axis resulting in upward Ekman pumping. To the east of the jet axis there is however a strong downward Ekman pumping due to a negative wind stress curl. Consequently, changes in coastal alongshore stress and/or curl depend on both the jet intensity and position. The jet position is constrained by the Indian summer monsoon pattern, which in turn is influenced by the astronomical parameters and the ice sheet cover. The astronomical parameters are indeed shown to impact wind stress intensity in the Arabian Sea through large-scale changes in the meridional gradient of upper-tropospheric temperature. However, both the astronomical parameters and the ice sheets affect the pattern of wind stress curl through the position of the sea level depression barycentre over the monsoon region (20-150° W, 30° S-60° N). The combined changes in monsoon intensity and pattern lead to some higher glacial productivity during the summer season, in agreement with some palaeo-productivity reconstructions.

A noncoherent model for microwave emissions and backscattering from the sea surface

NASA Technical Reports Server (NTRS)

Wu, S. T.; Fung, A. K.

1973-01-01

The two-scale (small irregularities superimposed upon large undulations) scattering theory proposed by Semyonov was extended and used to compute microwave apparent temperature and the backscattering cross section from ocean surfaces. The effect of the small irregularities upon the scattering characteristics of the large undulations is included by modifying the Fresnel reflection coefficients; whereas the effect of the large undulations upon those of the small irregularities is taken into account by averaging over the surface normals of the large undulations. The same set of surface parameters is employed for a given wind speed to predict both the scattering and the emission characteristics at both polarizations.

Airborne geophysics for mesoscale observations of polar sea ice in a changing climate

NASA Astrophysics Data System (ADS)

Hendricks, S.; Haas, C.; Krumpen, T.; Eicken, H.; Mahoney, A. R.

2016-12-01

Sea ice thickness is an important geophysical parameter with a significant impact on various processes of the polar energy balance. It is classified as Essential Climate Variable (ECV), however the direct observations of the large ice-covered oceans are limited due to the harsh environmental conditions and logistical constraints. Sea-ice thickness retrieval by the means of satellite remote sensing is an active field of research, but current observational capabilities are not able to capture the small scale variability of sea ice thickness and its evolution in the presence of surface melt. We present an airborne observation system based on a towed electromagnetic induction sensor that delivers long range measurements of sea ice thickness for a wide range of sea ice conditions. The purpose-built sensor equipment can be utilized from helicopters and polar research aircraft in multi-role science missions. While airborne EM induction sounding is used in sea ice research for decades, the future challenge is the development of unmanned aerial vehicle (UAV) platform that meet the requirements for low-level EM sea ice surveys in terms of range and altitude of operations. The use of UAV's could enable repeated sea ice surveys during the the polar night, when manned operations are too dangerous and the observational data base is presently very sparse.

Water Constituents in the North-western Black Sea from Optical Remote Sensing and In situ Data

NASA Astrophysics Data System (ADS)

Barale, V.; Cipollini, P.; Davidov, A.; Melin, F.

2002-03-01

Satellite-based optical observations of surface waters have been used to assess the main environmental interactions in the north-western Black Sea, as a contribution to the EROS 21 project. Such observations allow evaluations of the presence and abundance of water constituents (primarily phytoplankton pigments), providing essential information on the processes which are taking place in the area and on their spatial and temporal scales. An analysis of ocean colour imagery was performed, using historical data collected by the CZCS (1978-1986), and by the MOS before, during and after the EROS 21 oceanographic cruise which took place in April/May 1997. The time series of CZCS-derived parameters (i.e. chlorophyll-like pigment concentration) originates from the archive generated by the OCEAN project. The MOS data were processed to apply sensor calibration, to correct for atmospheric contamination so as to assess water-leaving radiances for each visible channel, and to estimate geophysical parameters such as pigment concentration and in-water optical depth, which is correlated to suspended matter concentration. The atmospheric correction was performed with a novel algorithm developed especially for MOS application. The bio-optical algorithms used to derive in-water parameters were obtained by comparison with the concurrent in situ measurements of optically active parameters collected in the north-western Black Sea in the framework of the EROS 21 project. The multi-satellite data set highlights the differences between western and eastern sub-basins, inshore and offshore domains, northern and southern near-coastal areas. In the Danube delta area, the water constituents trace complex interactions of near-coastal and basin-wide features of the Black Sea.

Surface Emissivity Effects on Thermodynamic Retrieval of IR Spectral Radiance

NASA Technical Reports Server (NTRS)

Zhou, Daniel K.; Larar, Allen M.; Smith, William L.; Liu, Xu

2006-01-01

The surface emissivity effect on the thermodynamic parameters (e.g., the surface skin temperature, atmospheric temperature, and moisture) retrieved from satellite infrared (IR) spectral radiance is studied. Simulation analysis demonstrates that surface emissivity plays an important role in retrieval of surface skin temperature and terrestrial boundary layer (TBL) moisture. NAST-I ultraspectral data collected during the CLAMS field campaign are used to retrieve thermodynamic properties of the atmosphere and surface. The retrievals are then validated by coincident in-situ measurements, such as sea surface temperature, radiosonde temperature and moisture profiles. Retrieved surface emissivity is also validated by that computed from the observed radiance and calculated emissions based on the retrievals of surface temperature and atmospheric profiles. In addition, retrieved surface skin temperature and emissivity are validated together by radiance comparison between the observation and retrieval-based calculation in the window region where atmospheric contribution is minimized. Both simulation and validation results have lead to the conclusion that variable surface emissivity in the inversion process is needed to obtain accurate retrievals from satellite IR spectral radiance measurements. Retrieval examples are presented to reveal that surface emissivity plays a significant role in retrieving accurate surface skin temperature and TBL thermodynamic parameters.

Ecology of Vibrio parahaemolyticus and Vibrio vulnificus in the Coastal and Estuarine Waters of Louisiana, Maryland, Mississippi, and Washington (United States)

PubMed Central

Bowers, John C.; Griffitt, Kimberly J.; Molina, Vanessa; Clostio, Rachel W.; Pei, Shaofeng; Laws, Edward; Paranjpye, Rohinee N.; Strom, Mark S.; Chen, Arlene; Hasan, Nur A.; Huq, Anwar; Noriea, Nicholas F.; Grimes, D. Jay; Colwell, Rita R.

2012-01-01

Vibrio parahaemolyticus and Vibrio vulnificus, which are native to estuaries globally, are agents of seafood-borne or wound infections, both potentially fatal. Like all vibrios autochthonous to coastal regions, their abundance varies with changes in environmental parameters. Sea surface temperature (SST), sea surface height (SSH), and chlorophyll have been shown to be predictors of zooplankton and thus factors linked to vibrio populations. The contribution of salinity, conductivity, turbidity, and dissolved organic carbon to the incidence and distribution of Vibrio spp. has also been reported. Here, a multicoastal, 21-month study was conducted to determine relationships between environmental parameters and V. parahaemolyticus and V. vulnificus populations in water, oysters, and sediment in three coastal areas of the United States. Because ecologically unique sites were included in the study, it was possible to analyze individual parameters over wide ranges. Molecular methods were used to detect genes for thermolabile hemolysin (tlh), thermostable direct hemolysin (tdh), and tdh-related hemolysin (trh) as indicators of V. parahaemolyticus and the hemolysin gene vvhA for V. vulnificus. SST and suspended particulate matter were found to be strong predictors of total and potentially pathogenic V. parahaemolyticus and V. vulnificus. Other predictors included chlorophyll a, salinity, and dissolved organic carbon. For the ecologically unique sites included in the study, SST was confirmed as an effective predictor of annual variation in vibrio abundance, with other parameters explaining a portion of the variation not attributable to SST. PMID:22865080

Mean gravity anomalies and sea surface heights derived from GEOS-3 altimeter data

NASA Technical Reports Server (NTRS)

Rapp, R. H.

1978-01-01

Approximately 2000 GEOS-3 altimeter arcs were analyzed to improve knowledge of the geoid and gravity field. An adjustment procedure was used to fit the sea surface heights (geoid undulations) in an adjustment process that incorporated cross-over constraints. The error model used for the fit was a one or two parameter model which was designed to remove altimeter bias and orbit error. The undulations on the adjusted arcs were used to produce geoid maps in 20 regions. The adjusted data was used to derive 301 5 degree equal area anomalies and 9995 1 x 1 degree anomalies in areas where the altimeter data was most dense, using least squares collocation techniques. Also emphasized was the ability of the altimeter data to imply rapid anomaly changes of up to 240 mgals in adjacent 1 x 1 degree blocks.

Application of Conjugate Gradient methods to tidal simulation

USGS Publications Warehouse

Barragy, E.; Carey, G.F.; Walters, R.A.

1993-01-01

A harmonic decomposition technique is applied to the shallow water equations to yield a complex, nonsymmetric, nonlinear, Helmholtz type problem for the sea surface and an accompanying complex, nonlinear diagonal problem for the velocities. The equation for the sea surface is linearized using successive approximation and then discretized with linear, triangular finite elements. The study focuses on applying iterative methods to solve the resulting complex linear systems. The comparative evaluation includes both standard iterative methods for the real subsystems and complex versions of the well known Bi-Conjugate Gradient and Bi-Conjugate Gradient Squared methods. Several Incomplete LU type preconditioners are discussed, and the effects of node ordering, rejection strategy, domain geometry and Coriolis parameter (affecting asymmetry) are investigated. Implementation details for the complex case are discussed. Performance studies are presented and comparisons made with a frontal solver. ?? 1993.

Modelling oil plumes from subsurface spills.

PubMed

Lardner, Robin; Zodiatis, George

2017-11-15

An oil plume model to simulate the behavior of oil from spills located at any given depth below the sea surface is presented, following major modifications to a plume model developed earlier by Malačič (2001) and drawing on ideas in a paper by Yapa and Zheng (1997). The paper presents improvements in those models and numerical testing of the various parameters in the plume model. The plume model described in this paper is one of the numerous modules of the well-established MEDSLIK oil spill model. The deep blowout scenario of the MEDEXPOL 2013 oil spill modelling exercise, organized by REMPEC, has been applied using the improved oil plume module of the MEDSLIK model and inter-comparison with results having the oil spill source at the sea surface are discussed. Copyright © 2017 Elsevier Ltd. All rights reserved.

Overseas trip report, CV 990 underflight mission. [Norwegian Sea, Greenland ice sheet, and Alaska

NASA Technical Reports Server (NTRS)

Gloersen, P.; Crawford, J.; Hardis, L.

1980-01-01

The scanning microwave radiometer-7 simulator, the ocean temperature scanner, and an imaging scatterometer/altimeter operating at 14 GHz were carried onboard the NASA CV-990 over open oceans, sea ice, and continental ice sheets to gather surface truth information. Data flights were conducted over the Norwegian Sea to map the ocean polar front south and west of Bear Island and to transect several Nimbus-7 footprints in a rectangular pattern parallel to the northern shoreline of Norway. Additional flights were conducted to obtain correlative data on the cryosphere parameters and characteristics of the Greenland ice sheet, and study the frozen lakes near Barrow. The weather conditions and flight path way points for each of the nineteen flights are presented in tables and maps.

Turbulent boundary layer on the surface of a sea geophysical antenna

NASA Astrophysics Data System (ADS)

Smol'Yakov, A. V.

2010-11-01

A theory is constructed that makes it possible to calculate the initial parameters necessary for calculating the hydrodynamic (turbulent) noise, which is a handicap to the operation of sea geophysical antennas. Algorithms are created for calculating the profile and defect of the average speed, displacement thickness, momentum thickness, and friction resistance in a turbulent boundary layer on a cylinder in its axial flow. Results of calculations using the developed theory are compared to experimental data. As the diameter of the cylinder tends to infinity, all relations of the theory pass to known relations for the boundary layer on a flat plate. The developed theory represents the initial stage of creating a method to calculate hydrodynamic noise, which is handicap to the operation of sea geophysical antennas.

An 800-year record of terrestrial organic matter from the East China Sea shelf break: Links to climate change and human activity in the Changjiang Basin

NASA Astrophysics Data System (ADS)

Li, Zhong Qiao; Wu, Ying; Liu, Su Mei; Du, Jin Zhou; Zhang, Jing

2016-02-01

The East China Sea (ECS) is a large river dominated marginal sea and receives massive volumes of terrestrial material from the Changjiang (Yangtze River). As the ECS preserves a record of terrestrial material derived from the Changjiang Basin, cores collected from this region can be used to reconstruct paleoclimate change and human disturbance in the watershed. A core (P4) was collected from the ECS shelf break and analyzed for bulk parameters (organic carbon (OC), total nitrogen (TN), and stable carbon isotopes (δ13C)), lignin phenols, and 3,5-dihydroxy benzoic acid (DHBA). The depth profiles of these parameters indicate stable and consistent marine production. The lignin source indices, cinnamyl phenols vs. vanillyl phenols (C/V) and syringyl phenols vs. vanillyl phenols (S/V), were in agreement with previously reported results from ECS surface sediments, but differed markedly from Bohai Sea surface sediments. The ratio of acid to aldehyde in vanillyl phenols ((Ad/Al)v) indicated the terrestrial OC in this core was refractory. At the same time, the variation in lignin phenols is positively correlated with the strength of the Indian Summer Monsoon (ISM) over the last 800 years (p<0.001). This is because most sediment is delivered from the upper reaches of the Changjiang Basin, where the ISM is the key control on precipitation. Two extreme drought events, around 1580 A.D. and 1770 A.D. were also identified in the core based on the extremely low C/V, S/V, lignin phenol vegetation index (LPVI), and DHBA values. Furthermore, the significant shift in C/V and S/V since 1880 A.D. is probably a reflection of increased human activity in the upper Changjiang Basin over this period.

A review of applications of microwave radiometry to oceanography

NASA Technical Reports Server (NTRS)

Wilheit, T. T., Jr.

1978-01-01

Following a review of the essential physics of microwave radiative transfer, oceanographic applications of this background physics are discussed using data from electrically scanning microwave radiometers on the Nimbus 5 and 6 satellites operating at 1.55-cm and 8-mm wavelengths, respectively. These data are interpreted in terms of rain rate, ice coverage, and first-year versus multiyear ice determination. It is shown that multifrequency radiometer measurements make it possible to separate the surface and atmospheric effects and to obtain useful measurements of sea surface temperature, surface wind speed, and atmospheric parameters along with improved measurements of rain and ice.

A model for the estimation of the surface fluxes of momentum, heat and moisture of the cloud topped marine atmospheric boundary layer from satellite measurable parameters. M.S. Thesis

NASA Technical Reports Server (NTRS)

Allison, D. E.

1984-01-01

A model is developed for the estimation of the surface fluxes of momentum, heat, and moisture of the cloud topped marine atmospheric boundary layer by use of satellite remotely sensed parameters. The parameters chosen for the problem are the integrated liquid water content, q sub li, the integrated water vapor content, q sub vi, the cloud top temperature, and either a measure of the 10 meter neutral wind speed or the friction velocity at the surface. Under the assumption of a horizontally homogeneous, well-mixed boundary layer, the model calculates the equivalent potential temperature and total water profiles of the boundary layer along with the boundary layer height from inputs of q sub li, q sub vi, and cloud top temperature. These values, along with the 10m neutral wind speed or friction velocity and the sea surface temperature are then used to estimate the surface fluxes. The development of a scheme to parameterize the integrated water vapor outside of the boundary layer for the cases of cold air outbreak and California coastal stratus is presented.

Late Quaternary paleoceanographic changes in the southwestern Okhotsk Sea: Evidence from geochemical, radiolarian, and diatom records

NASA Astrophysics Data System (ADS)

Okazaki, Yusuke; Takahashi, Kozo; Katsuki, Kota; Ono, Ayumu; Hori, Joichi; Sakamoto, Tatsuhiko; Uchida, Masao; Shibata, Yasuyuki; Ikehara, Minoru; Aoki, Kaori

2005-08-01

High-resolution analyses of geochemical parameters (biogenic opal, calcium carbonate, organic carbon, and nitrogen) and microfossil assemblages (diatoms and radiolarians) on Core MD01-2412 clarified detailed paleoceanographic changes such as sea-ice cover and biological production in the southwestern Okhotsk Sea during the last 115 kyr. An age model of Core MD01-2412 was established based on δ 18O stratigraphy, accelerator mass spectrometer (AMS) 14C, and tephrochronology. Sea-ice history reconstructed by siliceous microplankton records indicated that the present sea-ice condition was formed during the last 8 kyr. Only during Marine Isotope Stage (MIS) 2 was the duration of sea-ice cover in this region much longer than that of today (4-5 months a year). Two diatom species, Thalassionema nitzschioides and Fragilariopsis doliolus, revealed that the Soya Warm Current Water (SWCW) flowed into the Okhotsk Sea near the site of Core MD01-2412 during the last 12-14 kyr and during MIS 5a, and was associated with sea-level rise. Biological productivity rapidly increased during MIS 1, associated with sea-ice retreat. Two major increases of organic carbon (OC) contents (wt%) and C org/N ratios were observed, and the timings of these events were 15.8-16.7 ka (Event 1) and 13.1-13.6 ka (Event 2). Corresponding to these events, the abundance of Cycladophora davisiana, an intermediate water dwelling radiolarian species, increased. This high C. davisiana abundance can be correlated to the input of terrestrial organic matter from the submerged shelf to the intermediate water. Apart from the radiolarians, the production of diatoms in the surface waters was suppressed by the development of well-stratified surface water along with sea-ice melting during the early Holocene. Diatom production increased gradually during the last 10 kyr with enhanced vertical mixing.

Individual dietary specialization and dive behaviour in the California sea otter: Using archival time depth data to detect alternative foraging strategies

NASA Astrophysics Data System (ADS)

Tinker, M. T.; Costa, D. P.; Estes, J. A.; Wieringa, N.

2007-02-01

The existence of individual prey specializations has been reported for an ever-growing number of taxa, and has important ramifications for our understanding of predator-prey dynamics. We use the California sea otter population as a case study to validate the use of archival time-depth data to detect and measure differences in foraging behaviour and diet. We collected observational foraging data from radio-tagged sea otters that had been equipped with Mk9 time depth recorders (TDRs, Wildlife Computers, Redmond, WA). After recapturing the study animals and retrieving the TDRs it was possible to compare the two data types, by matching individual dives from the TDR record with observational data and thus examining behavioural correlates of capture success and prey species. Individuals varied with respect to prey selection, aggregating into one of three distinct dietary specializations. A number of TDR-derived parameters, particularly dive depth and post-dive surface interval, differed predictably between specialist types. A combination of six dive parameters was particularly useful for discriminating between specialist types, and when incorporated into a multivariate cluster analysis, these six parameters resulted in classification of 13 adult female sea otters into three clusters that corresponded almost perfectly to the diet-based classification (1 out of 13 animals was misclassified). Thus based solely on quantifiable traits of time-depth data that have been collected over an appropriate period (in this case 1 year per animal), it was possible to assign female sea otters to diet type with >90% accuracy. TDR data can thus be used as a tool to measure the degree of individual specialization in sea otter populations, a conclusion that will likely apply to other diving marine vertebrates as well. Our ultimate goals must be both to understand the causes of individual specialization, and to incorporate such variation into models of population- and community-level food web dynamics.

Individual dietary specialization and dive behaviour in the California sea otter: Using archival time-depth data to detect alternative foraging strategies

USGS Publications Warehouse

Tinker, M.T.; Costa, D.P.; Estes, J.A.; Wieringa, N.

2007-01-01

The existence of individual prey specializations has been reported for an ever-growing number of taxa, and has important ramifications for our understanding of predator-prey dynamics. We use the California sea otter population as a case study to validate the use of archival time-depth data to detect and measure differences in foraging behaviour and diet. We collected observational foraging data from radio-tagged sea otters that had been equipped with Mk9 time depth recorders (TDRs, Wildlife Computers, Redmond, WA). After recapturing the study animals and retrieving the TDRs it was possible to compare the two data types, by matching individual dives from the TDR record with observational data and thus examining behavioural correlates of capture success and prey species. Individuals varied with respect to prey selection, aggregating into one of three distinct dietary specializations. A number of TDR-derived parameters, particularly dive depth and post-dive surface interval, differed predictably between specialist types. A combination of six dive parameters was particularly useful for discriminating between specialist types, and when incorporated into a multivariate cluster analysis, these six parameters resulted in classification of 13 adult female sea otters into three clusters that corresponded almost perfectly to the diet-based classification (1 out of 13 animals was misclassified). Thus based solely on quantifiable traits of time-depth data that have been collected over an appropriate period (in this case 1 year per animal), it was possible to assign female sea otters to diet type with >90% accuracy. TDR data can thus be used as a tool to measure the degree of individual specialization in sea otter populations, a conclusion that will likely apply to other diving marine vertebrates as well. Our ultimate goals must be both to understand the causes of individual specialization, and to incorporate such variation into models of population- and community-level food web dynamics. ?? 2007 Elsevier Ltd. All rights reserved.

Sea-town interactions over Marseille: 3D urban boundary layer and thermodynamic fields near the surface

NASA Astrophysics Data System (ADS)

Lemonsu, A.; Pigeon, G.; Masson, V.; Moppert, C.

2006-02-01

3D numerical simulations with the Meso-NH atmospheric model including the Town Energy Balance urban parameterization, are conducted over the south-east of France and the one million inhabitants city of Marseille in the frameworks of the ESCOMPTE-UBL program. The geographic situation of the area is relatively complex, because of the proximity of the Mediterranean Sea and the presence of numerous massifs, inducing complex meteorological flows. The present work is focused on six days of the campaign, characterized by the development of strong summer sea-breeze circulations. A complete evaluation of the model is initially realized at both regional- and city-scales, by using the large available database. The regional evaluation shows a good behavior of the model, during the six days of simulation, either for the parameters near the surface or for the vertical profiles describing the structure of the atmosphere. The urban-scale evaluation indicates that the fine structure of the horizontal fields of air temperature above the city is correctly simulated by the model. A specific attention is then pointed to the 250-m horizontal resolution outputs, focused on the Marseille area, for two days of the campaign. From the study of the vertical structure of the Urban Boundary Layer and the thermodynamic fields near the surface, one underscores the important differences due to the regional and local flows, and the complex interactions that occur between the urban effects and the effects of sea breezes.

Successes and Challenges in Linking Observations and Modeling of Marine and Terrestrial Cryospheric Processes

NASA Astrophysics Data System (ADS)

Herzfeld, U. C.; Hunke, E. C.; Trantow, T.; Greve, R.; McDonald, B.; Wallin, B.

2014-12-01

Understanding of the state of the cryosphere and its relationship to other components of the Earth system requires both models of geophysical processes and observations of geophysical properties and processes, however linking observations and models is far from trivial. This paper looks at examples from sea ice and land ice model-observation linkages to examine some approaches, challenges and solutions. In a sea-ice example, ice deformation is analyzed as a key process that indicates fundamental changes in the Arctic sea ice cover. Simulation results from the Los Alamos Sea-Ice Model CICE, which is also the sea-ice component of the Community Earth System Model (CESM), are compared to parameters indicative of deformation as derived from mathematical analysis of remote sensing data. Data include altimeter, micro-ASAR and image data from manned and unmanned aircraft campaigns (NASA OIB and Characterization of Arctic Sea Ice Experiment, CASIE). The key problem to linking data and model results is the derivation of matching parameters on both the model and observation side.For terrestrial glaciology, we include an example of a surge process in a glacier system and and example of a dynamic ice sheet model for Greenland. To investigate the surge of the Bering Bagley Glacier System, we use numerical forward modeling experiments and, on the data analysis side, a connectionist approach to analyze crevasse provinces. In the Greenland ice sheet example, we look at the influence of ice surface and bed topography, as derived from remote sensing data, on on results from a dynamic ice sheet model.

Investigation using data from ERTS-1 to develop and implement utilization of living marine resources. [availability and distribution of menhaden fish in Mississippi Sound and Gulf waters

NASA Technical Reports Server (NTRS)

Stevenson, W. H. (Principal Investigator); Pastula, E. J., Jr.

1973-01-01

The author has identified the following significant results. This 15-month ERTS-1 investigation produced correlations between satellite, aircraft, menhaden fisheries, and environmental sea truth data from the Mississippi Sound. Selected oceanographic, meteorological, and biological parameters were used as indirect indicators of the menhaden resource. Synoptic and near real time sea truth, fishery, satellite imagery, aircraft acquired multispectral, photo and thermal IR information were acquired as data inputs. Computer programs were developed to manipulate these data according to user requirements. Preliminary results indicate a correlation between backscattered light with chlorophyll concentration and water transparency in turbid waters. Eight empirical menhaden distribution models were constructed from combinations of four fisheries-significant oceanographic parameters: water depth, transparency, color, and surface salinity. The models demonstrated their potential for management utilization in areas of resource assessment, prediction, and monitoring.

Spatially-resolved mean flow and turbulence help explain observed erosion and deposition patterns of snow over Antarctic sea ice

NASA Astrophysics Data System (ADS)

Trujillo, E.; Giometto, M. G.; Leonard, K. C.; Maksym, T. L.; Meneveau, C. V.; Parlange, M. B.; Lehning, M.

2014-12-01

Sea ice-atmosphere interactions are major drivers of patterns of sea ice drift and deformations in the Polar regions, and affect snow erosion and deposition at the surface. Here, we combine analyses of sea ice surface topography at very high-resolutions (1-10 cm), and Large Eddy Simulations (LES) to study surface drag and snow erosion and deposition patterns from process scales to floe scales (1 cm - 100 m). The snow/ice elevations were obtained using a Terrestrial Laser Scanner during the SIPEX II (Sea Ice Physics and Ecosystem eXperiment II) research voyage to East Antarctica (September-November 2012). LES are performed on a regular domain adopting a mixed pseudo-spectral/finite difference spatial discretization. A scale-dependent dynamic subgrid-scale model based on Lagrangian time averaging is adopted to determine the eddy-viscosity in the bulk of the flow. Effects of larger-scale features of the surface on wind flows (those features that can be resolved in the LES) are accounted for through an immersed boundary method. Conversely, drag forces caused by subgrid-scale features of the surface should be accounted for through a parameterization. However, the effective aerodynamic roughness parameter z0 for snow/ice is not known. Hence, a novel dynamic approach is utilized, in which z0 is determined using the constraint that the total momentum flux (drag) must be independent on grid-filter scale. We focus on three ice floe surfaces. The first of these surfaces (October 6, 2012) is used to test the performance of the model, validate the algorithm, and study the spatial distributed fields of resolved and modeled stress components. The following two surfaces, scanned at the same location before and after a snow storm event (October 20/23, 2012), are used to propose an application to study how spatially resolved mean flow and turbulence relates to observed patterns of snow erosion and deposition. We show how erosion and deposition patterns are correlated with the computed stresses, with modeled stresses having higher explanatory power. Deposition is mainly occurring in wake regions of specific ridges that strongly affect wind flow patterns. These larger ridges also lock in place elongated streaks of relatively high speeds with axes along the stream-wise direction, and which are largely responsible for the observed erosion.

Fully reprocessed ERS-1 altimeter data from 1992 to 1995: Feasibility of the detection of long term sea level change

NASA Astrophysics Data System (ADS)

Anzenhofer, M.; Gruber, T.

1998-04-01

Global mean sea level observations are necessary to answer the urgent questions about climate changes and their impact on socio-economy. At GeoForschungsZentrum/Geman Processing and Archiving Facility ERS altimeter data is used to systematically generate geophysical products such as sea surface topography, high-resolution geoid and short- and long-period sea surface height models. On the basis of this experience, fully reprocessed ERS-1 altimeter data is used to generated a time series of monthly sea surface height models from April 1992 to April 1995. The reprocessing consists of improved satellite ephemerides, merging of Grenoble tidal model, and application of range corrections due to timing errors. With the new data set the TOPEX/POSEIDON prelaunch accuracy requirements are fulfilled. The 3-year time series is taken to estimate the rate of change of global mean sea level. A careful treatment of seasonal effects is considered. A masking of continents, sea ice, and suspect sea surface heights is chosen that is common for all sea surface height models. The obtained rate of change is compared to external results from tide gauge records and TOPEX/POSEIDON data. The relation of sea level changes and sea surface temperature variations is examined by means of global monthly sea surface temperature maps. Both global wind speed and wave height maps are investigated and correlated with sea surface heights and sea surface temperatures in order to find other indicators of climate variations. The obtained rate of changes of the various global maps is compared to an atmospheric CO2 anomaly record, which is highly correlated to El Niño events. The relatively short period of 3 years, however, does not allow definite conclusions with respect to possible long-term climate changes.

Waves on Seas of Mars and Titan: Wind-Tunnel Experiments on Wind-Wave Generation in Extraterrestrial Atmospheres

NASA Technical Reports Server (NTRS)

Lorenz, R. D.; Kraal, E. R.; Eddlemon, E. E.; Cheney, J.; Greeley, R.

2004-01-01

The generation of waves by winds across Earth's water oceans is a topic of enduring fascination. However, the physics of the problem are rather forbidding and thus the relationships between real-world windspeed and sea state tend to be empirical. Such empirical relations are of limited utility in environments where the physical parameters are different, such as the surfaces of other planets. These environments have only recently come to oceanographers attention, with the discovery of ancient shorelines and lakes on Mars, and the prospects for and recent evidence of lakes and seas of liquid hydrocarbons on Saturn's moon Titan. We are aware of only one other published experimental wind-water tunnel study where the fluid parameters have been varied. This used artificially-generated mm-scale waves at 3.8-7.6 Hz in water, glycerol solutions (higher viscosity) and surfactant solutions (lower surface tension). Lower viscosity solutions had higher wave growth rates: surprisingly, higher surface tension led to more rapid wave growth. The liquid density was not appreciably varied, and 1 bar air was used throughout.We used the MARSWIT (Mars Wind Tunnel) operated by ASU at NASA Ames. A fiberglass tray (5 cm x 120 cm x 75 cm) was installed in the tunnel, with an approx. 1:5 ramp to prevent strong flow separation. The tray was filled to a depth of about 4 cm. Sensors were clamped to the tray itself or held by a steel and aluminium frame just above the water level. A towel was draped on the water surface at the downwind end of the tray to act as a damper to suppress wave reflection. Position-sensitive infrared (IR) reflection sensors (Sharp GP12D02) and ultrasonic rangers (Devantech DF-04) used in mobile robotics were used as water level sensors. The tray was observed with a video camera, whose output could be viewed on a monitor and recorded on VHS tape.

Automated parameter tuning applied to sea ice in a global climate model

NASA Astrophysics Data System (ADS)

Roach, Lettie A.; Tett, Simon F. B.; Mineter, Michael J.; Yamazaki, Kuniko; Rae, Cameron D.

2018-01-01

This study investigates the hypothesis that a significant portion of spread in climate model projections of sea ice is due to poorly-constrained model parameters. New automated methods for optimization are applied to historical sea ice in a global coupled climate model (HadCM3) in order to calculate the combination of parameters required to reduce the difference between simulation and observations to within the range of model noise. The optimized parameters result in a simulated sea-ice time series which is more consistent with Arctic observations throughout the satellite record (1980-present), particularly in the September minimum, than the standard configuration of HadCM3. Divergence from observed Antarctic trends and mean regional sea ice distribution reflects broader structural uncertainty in the climate model. We also find that the optimized parameters do not cause adverse effects on the model climatology. This simple approach provides evidence for the contribution of parameter uncertainty to spread in sea ice extent trends and could be customized to investigate uncertainties in other climate variables.

On the relationships of gas transfer velocity with turbulent kinetic energy dissipation rate and wind waves

NASA Astrophysics Data System (ADS)

Zhao, D.

2012-12-01

The exchange of carbon dioxide across the air-sea interface is an important component of the atmospheric CO2 budget. Understanding how future changes in climate will affect oceanic uptake and releaser CO2 requires accurate estimation of air-sea CO2 flux. This flux is typically expressed as the product of gas transfer velocity, CO2 partial pressure difference in seawater and air, and the CO2 solubility. As the key parameter, gas transfer velocity has long been known to be controlled by the near-surface turbulence in water, which is affected by many factors, such as wind forcing, ocean waves, water-side convection and rainfall. Although the wind forcing is believed as the major factor dominating the near-surface turbulence, many studies have shown that the wind waves and their breaking would greatly enhance turbulence compared with the classical solid wall theory. Gas transfer velocity has been parameterized in terms of wind speed, turbulent kinetic energy dissipation rate, and wave parameters on the basis of observational data or theoretical analysis. However, great discrepancies, as large as one order, exist among these formulas. In this study, we will systematically analyze the differences of gas transfer velocity proposed so far, and try to find the reason that leads to their uncertainties. Finally, a new formula for gas transfer velocity will be given in terms of wind speed and wind wave parameter.

Marine ARM GPCI Investigation of Clouds Infrared Sea Surface Temperature Autonomous Radiometer (ISAR) Field Campaign Report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Reynolds, R. Michael; Long, Charles N.

Sea surface temperature (SST) is one of the most appropriate and important climate parameters: a widespread increase is an indicator of global warming and modifications of the geographical distribution of SST are an extremely sensitive indicator of climate change. There is high demand for accurate, reliable, high-spatial-and-temporal-resolution SST measurements for the parameterization of ocean-atmosphere heat, momentum, and gas (SST is therefore critical to understanding the processes controlling the global carbon dioxide budget) fluxes, for detailed diagnostic and process-orientated studies to better understand the behavior of the climate system, as model boundary conditions, for assimilation into climate models, and for themore » rigorous validation of climate model output. In order to achieve an overall net flux uncertainty < 10 W/m 2 (Bradley and Fairall, 2006), the sea surface (skin) temperature (SSST) must be measured to an error < 0.1 C and a precision of 0.05 C. Anyone experienced in shipboard meteorological measurements will recognize this is a tough specification. These demands require complete confidence in the content, interpretation, accuracy, reliability, and continuity of observational SST data—criteria that can only be fulfilled by the successful implementation of an ongoing data product validation strategy.« less

Distribution of CO2 parameters in the Western Tropical Atlantic Ocean

NASA Astrophysics Data System (ADS)

Araujo, Moacyr; Bonou, Frédéric; Noriega, Carlos; Lefèvre, Nathalie

2016-04-01

The variability of sea surface Total Alkalinity (TA) and sea surface Total Inorganic Carbon (CT) is examined using all available data in the western tropical Atlantic (WTA: 20° S-20° N, 60° W-20° W). Lowest TA and CTare observed for the region located between 0°N-15°N/60°W-50°W and are explained by the influence of the Amazon plume during boreal summer. In the southern part of the area, 20°S-10°S/40°W-60°W, the highest values of TA and CTare linked to the CO2-rich waters due to the equatorial upwelling, which are transported by the South Equatorial Current (SEC) flowing from the African coast to the Brazilian shore. An increase of CT of 0.9 ± 0.3 μmol kg-1yr-1has been observed in the SEC region and is consistent with previous published estimates. A revised CT-Sea Surface Salinity (SSS) relationship is proposed for the WTA to take into account the variability of CT at low salinities. This new CT-SSS relationship together with a published TA-SSS relationship allow to calculate pCO2 values that compare well with observed pCO2 (R2=0.90).

Distribution of CO2 parameters in the Western Tropical Atlantic Ocean

NASA Astrophysics Data System (ADS)

Bonou, Frédéric Kpèdonou; Noriega, Carlos; Lefèvre, Nathalie; Araujo, Moacyr

2016-03-01

The variability of sea surface Total Alkalinity (TA) and sea surface Total Inorganic Carbon (CT) is examined using all available data in the western tropical Atlantic (WTA: 20°S-20°N, 60°W-20°W). Lowest TA and CT are observed for the region located between 0°N-15°N/60°W-50°W and are explained by the influence of the Amazon plume during boreal summer. In the southern part of the area, 20°S-10°S/40°W-60°W, the highest values of TA and CT are linked to the CO2-rich waters due to the equatorial upwelling, which are transported by the South Equatorial Current (SEC) flowing from the African coast to the Brazilian shore. An increase of CT of 0.9 ± 0.3 μmol kg-1yr-1 has been observed in the SEC region and is consistent with previous published estimates. A revised CT-Sea Surface Salinity (SSS) relationship is proposed for the WTA to take into account the variability of CT at low salinities. This new CT-SSS relationship together with a published TA-SSS relationship allow to calculate pCO2 values that compare well with observed pCO2 (R2 = 0.90).

A CCIR aeronautical mobile satellite report

NASA Technical Reports Server (NTRS)

Davarian, Faramaz; Bishop, Dennis; Rogers, David; Smith, Ernest K.

1989-01-01

Propagation effects in the aeronautical mobile-satellite service differ from those in the fixed-satellite service and other mobile-satellite services because: small antennas are used on aircraft, and the aircraft body may affect the performance of the antenna; high aircraft speeds cause large Doppler spreads; aircraft terminals must accommodate a large dynamic range in transmission and reception; and due to their high speeds, banking maneuvers, and three-dimensional operation, aircraft routinely require exceptionally high integrity of communications, making even short-term propagation effects very important. Data and models specifically required to characterize the path impairments are discussed, which include: tropospheric effects, including gaseous attenuation, cloud and rain attenuation, fog attenuation, refraction and scintillation; surface reflection (multipath) effects; ionospheric effects such as scintillation; and environmental effects (aircraft motion, sea state, land surface type). Aeronautical mobile-satellite systems may operate on a worldwide basis, including propagation paths at low elevation angles. Several measurements of multipath parameters over land and sea were conducted. In some cases, laboratory simulations are used to compare measured data and verify model parameters. The received signals is considered in terms of its possible components: a direct wave subject to atmospheric effects, and a reflected wave, which generally contains mostly a diffuse component.

Both natural selection and isolation by distance explain phenotypic divergence in bill size and body mass between South Australian little penguin colonies.

PubMed

Colombelli-Négrel, Diane

2016-11-01

Morphological variation between populations of the same species can arise as a response to genetic variation, local environmental conditions, or a combination of both. In this study, I examined small-scale geographic variation in bill size and body mass in little penguins ( Eudyptula minor ) across five breeding colonies in South Australia separated by <150 km. To help understand patterns driving the differences, I investigated these variations in relation to environmental parameters (air temperature, sea surface temperature, and water depth) and geographic distances between the colonies. I found substantial morphological variation among the colonies for body mass and bill measurements (except bill length). Colonies further located from each other showed greater morphological divergence overall than adjacent colonies. In addition, phenotypic traits were somewhat correlated to environmental parameters. Birds at colonies surrounded by hotter sea surface temperatures were heavier with longer and larger bills. Birds with larger and longer bills were also found at colonies surrounded by shallower waters. Overall, the results suggest that both environmental factors (natural selection) and interpopulation distances (isolation by distance) are causes of phenotypic differentiation between South Australian little penguin colonies.

The multi-parameter borehole system and high resolution seismic studies in the western part of the main Marmara Fault in the frame of MARSITE Project.

NASA Astrophysics Data System (ADS)

Ozel, Oguz; Guralp, Cansun; Tunc, Suleyman; Yalcinkaya, Esref

2016-04-01

The main objective of this study is to install a multi-parameter borehole system and surface array as close to the main Marmara Fault (MMF) in the western Marmara Sea as possible, and measure continuously the evolution of the state of the fault zone surrounding the MMF and to detect any anomaly or change, which may occur before earthquakes by making use of the data from the arrays already running in the eastern part of the Marmara Sea. The multi-parameter borehole system is composed of very wide dynamic range and stable borehole (VBB) broad band seismic sensor, and incorporate strain meter, tilt meter, and temperature and local hydrostatic pressure measuring devices. The borehole seismic station uses the latest update technologies and design ideas to record "Earth tides" signals to the smallest magnitude -3 events. Additionally, a surface microearthquake observation array, consisting of 8-10 seismometers around the borehole is established to obtain continuous high resolution locations of micro-seismicity and to better understand the existing seismically active structures and their roles in local tectonic settings.Bringing face to face the seismograms of microearthquakes recorded by borehole and surface instruments portrays quite different contents. The shorter recording duration and nearly flat frequency spectrum up to the Nyquist frequencies of borehole records are faced with longer recording duration and rapid decay of spectral amplitudes at higher frequencies of a surface seismogram. The main causative of the observed differences are near surface geology effects that mask most of the source related information the seismograms include, and that give rise to scattering, generating longer duration seismograms. In view of these circumstances, studies on microearthquakes employing surface seismograms may bring on misleading results. Particularly, the works on earthquake physics and nucleation process of earthquakes requires elaborate analysis of tiny events. It is obvious from the studies on the nucleation process of the 1999 earthquake that tens of minutes before the major rupture initiate noteworthy microearthquake activity happened. The starting point of the 1999 rupture was a site of swarm activity noticed a few decades prior the main shock. Nowadays, analogous case is probable in western Marmara Sea region, prone to a major event in near future where the seismic activity is prevailing along the impending rupture zone. Deploying a borehole system eastern end of the Ganos fault zone may yield invaluable data to closely inspect and monitor the last stages of the preparation stage of major rupture.

SeaWiFS Technical Report Series. Volume 38; SeaWiFS Calibration and Validation Quality Control Procedures

NASA Technical Reports Server (NTRS)

Hooker, Stanford B. (Editor); Firestone, Elaine R. (Editor); McClain, Charles R.; Darzi, Michael; Barnes, Robert A.; Eplee, Robert E.; Firestone, James K.; Patt, Frederick S.; Robinson, Wayne D.; Schieber, Brian D.;

Developing Integrated Remote Sensing and Geographical Information Sciences Procedures to Assess Impacts of Climate Variations on Spatio-Temporal Distribution of Mangroves

NASA Astrophysics Data System (ADS)

Qaisar, Maha

2016-07-01

Pakistan's periled treasures of mangroves require protection from devastating anthropogenic activities, which can only be achieved through the identification and management of this habitat. The primary objective of this study is to identify the potential habitat of mangroves along the coastline of Pakistan with the help of Remote Sensing (RS) and Geographical Information System (GIS) techniques. Once the mangroves were identified, species of mangroves need to be separated through Object Based Image Analysis (OBIA) which gave the area of mangroves and non mangroves sites. Later other parameters of Sea Surface Temperature, Sea Surface Salinity, chlorophyll-a along with altimetry data were used to assess the climatic variations on the spatio-temporal distribution of mangroves. Since mangroves provide economical, ecological, biological indication of Coastal Change or Sea Level Rise. Therefore, this provides a strong platform to assess the climatic variations which are posing negative impacts on the mangroves ecosystem. The results indicate that mangroves are present throughout along the coastline, proving that Pakistan is rich in these diverse ecosystems. Pakistan being at important geo strategic position can also benefit from its vast mangroves and other coastal resources such as coral reefs and fish varieties. Moreover, coastal zone management through involvement of the local community and establishment of Marine Protected Area (MPA) is the need of the hour to avoid deforestation of mangroves, which can prove to be deadly damaging for the fish populace since it provides habitats to various marine animals. However, the established relationship among SST, SSS, chlorophyll-a and altimetry data assisted to know the suitable sites for mangroves. But due to enhanced climatic impacts these relationships are distorted which has posed devastating effects on the growth and distribution of mangroves. Study area was Karachi Coast, Pakistan. The total area of Karachi is about 70 km long with vital importance of ecological, economical and biological indication of sea level rise. The desktop work was started with the acquisition of Landsat 8 image then pre-processing was applied, that includes stacking of bands, digitizing of study area and latterly sub setting of this area. Now spectral indices were applied to enhance water and vegetation. Normalized Difference Vegetative Index (NDVI) and Normalized Difference Water Index (NDWI) were calculated. Object Based Image Analysis (OBIA) was performed on land covers to get the land cover maps. However, other parameters of SST, chlorophyll-a of the study area were also estimated using MODIS products to establish the relationship for ascertaining the mangroves growth and distribution. Whereas, sea level in relation with mangroves has a substantial correlation i.e. when the sea level is not changing relative to the mangrove surface, mangrove position remains generally stable. Whereas, if the sea level is falling relative to the mangrove surface, mangrove margins migrate seaward and possibly laterally if these areas adjacent to the mangrove develop conditions suitable for mangrove establishment. Moreover, if sea-level is rising relative to the elevation of the mangrove sediment surface, the mangrove's seaward and landward margins retreat landward as the mangrove species maintain their preferred hydro period. The mangrove may also expand laterally into areas of higher elevation. Therefore, the study of altimetry provides a milestone in the spatio-temporal growth and distribution of mangrove. Thus, this established study can help coastal related agencies to work more efficiently in the field of research and even for the welfare of the coastal community so that the risk of climate variability on the mangrove ecosystem can be minimized.

Sea ice-atmosphere interaction. Application of multispectral satellite data in polar surface energy flux estimates

NASA Technical Reports Server (NTRS)

Steffen, Konrad; Key, Jeff; Maslanik, Jim; Haefliger, Marcel; Fowler, Chuck

1992-01-01

Satellite data for the estimation of radiative and turbulent heat fluxes is becoming an increasingly important tool in large-scale studies of climate. One parameter needed in the estimation of these fluxes is surface temperature. To our knowledge, little effort has been directed to the retrieval of the sea ice surface temperature (IST) in the Arctic, an area where the first effects of a changing climate are expected to be seen. The reason is not one of methodology, but rather our limited knowledge of atmospheric temperature, humidity, and aerosol profiles, the microphysical properties of polar clouds, and the spectral characteristics of the wide variety of surface types found there. We have developed a means to correct for the atmospheric attenuation of satellite-measured clear sky brightness temperatures used in the retrieval of ice surface temperature from the split-window thermal channels of the advanced very high resolution radiometer (AVHRR) sensors on-board three of the NOAA series satellites. These corrections are specified for three different 'seasons' and as a function of satellite viewing angle, and are expected to be applicable to the perennial ice pack in the central Arctic Basin.

Key roles of sea ice in inducing contrasting modes of glacial AMOC and climate

NASA Astrophysics Data System (ADS)

Sherriff-Tadano, S.; Abe-Ouchi, A.

2017-12-01

Gaining a better understanding of glacial Atlantic meridional overturning circulation (AMOC) is important to interpret the glacial climate changes such as the Heinrich event. Recent studies suggest that changes in sea ice over the North Atlantic largely affect the surface wind. Since changes in surface wind have a large impact on the AMOC, this implies a role of sea ice in modifying the AMOC though surface wind. However, the impact of sea ice on the surface winds and the impact of changes in the winds on the AMOC remain unclear. In this study, we first assess the impact of sea ice expansion on the winds. We then explore whether the changes in winds play a role in modifying the AMOC and climate. For this purpose, results from MIROC4m are analyzed (Kawamura et al. 2017). To clarify the impact of changes in sea ice on the surface wind, sensitivity experiments are conducted with an atmospheric general circulation model (AGCM). In the AGCM experiments, we modify the sea ice to extract the impact of sea ice on the winds. Partial decouple experiments are conducted with the coupled model MIROC4m, which we modify the surface winds to assess the impact of changes in the surface wind due to sea ice expansion on the AMOC. Results show that expansion of sea ice substantially weakens the surface wind over the northern North Atlantic. AGCM experiments show that a drastic decrease in surface temperature duo to a suppression of sensible heat flux plays a dominant role in weakening the surface winds through increasing the static stability of the air column near the surface. Partial decouple experiments with MIROC4m show that the weakening of the surface wind due to the expansion of sea ice plays an important role in maintaining the weak AMOC. Thus, these experiments show that the weakening of the surface winds due to sea ice expansion plays a role in stabilizing the AMOC.

Numerical 3D modelling of oil dispersion in the sea due to different accident scenarios

NASA Astrophysics Data System (ADS)

Guandalini, Roberto; Agate, Giordano; Moia, Fabio

2017-04-01

The purpose of the study has been the development of a methodology, based on a numerical 3D approach, for the analysis of oil dispersion in the sea, in order to simulate with a high level of accuracy the dynamic behavior of the oil plume and its displacement in the environment. As a matter of fact, the numerical simulation is the only approach currently able to analyse in detail possible accident scenarios, even with an high degree of complexity, of different type and intensity, allowing to follow their evolution both in time and space, and to evaluate the effectiveness of suggested prevention or recovery actions. The software for these calculations is therefore an essential tool in order to simulate the impact effects in the short, medium and long period, able to account for the complexity of the sea system involved in the dispersion process and its dependency on the meteorological, marine and morphological local conditions. This software, generally based on fluid dynamic 3D simulators and modellers, is therefore extremely specialized and requires expertise for an appropriate usage, but at the same time it allows detailed scenario analyses and design verifications. It takes into account different parameters as the sea current field and its turbulence, the wind acting on the sea surface, the salinity and temperature gradients, the local coastal morphology, the seabed bathymetry and the tide. The applied methodology is based on the Integrated Fluid Dynamic Simulation System HyperSuite developed by RSE. This simulation system includes the consideration of all the parameters previously listed, in the frame of a 3D Eulerian finite element fluid dynamic model, which accuracy is guaranteed by a very detailed spatial mesh and by an automatically optimized time step management. In order to assess the methodology features, an area of more than 2500 km2 and depth of 200 m located in the middle Adriatic Sea has been modelled. The information required for the simulation in different environmental conditions, have been collected from RSE proprietary and public databases directly connected to the model. Finally, the possible pollution source has been chosen in correspondence with the offshore drilling wells for the exploitation of the "Ombrina Mare" oil field, located at a distance of 6 km from the coast, and the project includes a FPSO unit. A number of different scenarios have been simulated using the 3D model created by HyperSuite, in different environmental conditions and considering emission events of low intensity and long period or of high intensity and short period, located near the sea surface or near the sea bottom. For each scenario, a preliminary initialization in the fluid dynamic unperturbed conditions at the starting date has been carried out, from which the emission period followed by a properly duration of diffusion period of the pollutant has been simulated. The results allowed to evaluate the relevance of the effects due to the environmental parameters as the wind, sea current and tide, putting in evidence the capability of the methodology to support the safety requirements in the frame of off shore oil exploitation provided that a dynamic characterization of the environment parameters is accounted for a sufficient detail.

Characterizing overwater roughness Reynolds number during hurricanes

NASA Astrophysics Data System (ADS)

Hsu, S. A.; Shen, Hui; He, Yijun

2017-11-01

The Reynolds number, which is the dimensionless ratio of the inertial force to the viscous force, is of great importance in the theory of hydrodynamic stability and the origin of turbulence. To investigate aerodynamically rough flow over a wind sea, pertinent measurements of wind and wave parameters from three data buoys during Hurricanes Kate, Lili, Ivan, Katrina, Rita, and Wilma are analyzed. It is demonstrated that wind seas prevail when the wind speed at 10 m and the wave steepness exceed 9 m s-1 and 0.020, respectively. It is found that using a power law the roughness Reynolds number is statistically significantly related to the significant wave height instead of the wind speed as used in the literature. The reason for this characterization is to avoid any self-correlation between Reynolds number and the wind speed. It is found that although most values of R_{*} were below 500, they could reach to approximately 1000 near the radius of maximum wind. It is shown that, when the significant wave height exceeds approximately 2 m in a wind sea, the air flow over that wind sea is already under the fully rough condition. Further analysis of simultaneous measurements of wind and wave parameters using the logarithmic law indicates that the estimated overwater friction velocity is consistent with other methods including the direct (eddy-covariance flux) measurements, the atmospheric vorticity approach, and the sea-surface current measurements during four slow moving super typhoons with wind speed up to 70 m s-1.

In Situ Global Sea Surface Salinity and Variability from the NCEI Global Thermosalinograph Database

NASA Astrophysics Data System (ADS)

Wang, Z.; Boyer, T.; Zhang, H. M.

2017-12-01

Sea surface salinity (SSS) plays an important role in the global ocean circulations. The variations of sea surface salinity are key indicators of changes in air-sea water fluxes. Using nearly 30 years of in situ measurements of sea surface salinity from thermosalinographs, we will evaluate the variations of the sea surface salinity in the global ocean. The sea surface salinity data used are from our newly-developed NCEI Global Thermosalinograph Database - NCEI-TSG. This database provides a comprehensive set of quality-controlled in-situ sea-surface salinity and temperature measurements collected from over 340 vessels during the period 1989 to the present. The NCEI-TSG is the world's most complete TSG dataset, containing all data from the different TSG data assembly centers, e.g. COAPS (SAMOS), IODE (GOSUD) and AOML, with more historical data from NCEI's archive to be added. Using this unique dataset, we will investigate the spatial variations of the global SSS and its variability. Annual and interannual variability will also be studied at selected regions.

Simulation of laser beam reflection at the sea surface

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Repasi, Endre

2011-05-01

A 3D simulation of the reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation is suitable for both the calculation of images of SWIR (short wave infrared) imaging sensor and for determination of total detected power of reflected laser light for a bistatic configuration of laser source and receiver at different atmospheric conditions. Our computer simulation comprises the 3D simulation of a maritime scene (open sea/clear sky) and the simulation of laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. The propagation model for water waves is applied for sea surface animation. To predict the view of a camera in the spectral band SWIR the sea surface radiance must be calculated. This is done by considering the emitted sea surface radiance and the reflected sky radiance, calculated by MODTRAN. Additionally, the radiances of laser light specularly reflected at the wind-roughened sea surface are modeled in the SWIR band considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). This BRDF model considers the statistical slope statistics of waves and accounts for slope-shadowing of waves that especially occurs at flat incident angles of the laser beam and near horizontal detection angles of reflected irradiance at rough seas. Simulation results are presented showing the variation of the detected laser power dependent on the geometric configuration of laser, sensor and wind characteristics.

Classifying and retracking altimeter waveforms over wetlands: A case study in the Hsiang-Shan wetland, Taiwan

NASA Astrophysics Data System (ADS)

Huan Chin, K.; Wei Ming, C.; Chung-Yen, K.; Tseng, K. H.; Shum, C. K.; Hwang, C.; Cheng, K. C.

2017-12-01

A coastal wetland is an area saturated with fresh to saline water, and has a distinct ecological system. Taiwan has abundant wetlands, and some of them contain altimeter measurements from the Enivsat and TOPEX/Poseidon series of satellites. Typically, such measurements are refined to provide additional sea level measurements over tide gauge data. Often, here the refinements have limitations because of the contaminations of altimeter waveforms and improper geophysical corrections. In this study, we classify Envisat and SARAL/Altika waveforms over coastal areas of Taiwan using the Linear Discriminant Analysis (LDA). Three types of waveforms are identified: coastal ocean, wetland and land-noise waveforms. We carry out a case study over Hsinchu's Hsiang-Shan wetland in northern Taiwan. The coastal ocean and wetland waveforms, are retracked by two different retrackers, with the main objective of improving the accuracy of sea surface height measurements. The result is then assessed by measurements from a nearby tide gauge and modeled geoidal heights from EGM2008. Some of the parameters in our retrackers are associated with the surface and sub-surface properties of the Hsiang-Shan wetland. The space-time evolutions of these parameters can reflect wetland changes due to factors such as changes in sedimentation and soil moisture. This presentation will show how coastal altimeter data can benefit wetland studies.

Hydrochemistry of the Tumen River Estuary, Sea of Japan

NASA Astrophysics Data System (ADS)

Tishchenko, P. Ya.; Semkin, P. Yu.; Pavlova, G. Yu.; Tishchenko, P. P.; Lobanov, V. B.; Marjash, A. A.; Mikhailik, T. A.; Sagalaev, S. G.; Sergeev, A. F.; Tibenko, E. Yu.; Khodorenko, N. D.; Chichkin, R. V.; Shvetsova, M. G.; Shkirnikova, E. M.

2018-03-01

The hydrological and hydrochemical parameters of the Tumen River estuary were collected at 13 stations in May and October 2015. Vertical temperature, conductivity, dissolved oxygen, chlorophyll fluorescence, and turbidity profiles were obtained. Water was sampled from the surface and bottom layer. The water samples were analyzed for major ions, pH, salinity, concentrations of dissolved oxygen, major nutrients, dissolved organic carbon, humic matter, and δ18O and δD isotopes. This estuary is attributed to microtidal type with a flushing time of about 10 h. A phytoplakton bloom occurred in the top layer of the estuary. For surface horizons, the hydrochemical parameters show a linear correlation with salinity. In the bottom horizons, all these parameters, except for major ions and δ18O and δD isotopes, reveal substantial nonconservative behavior. The nonconservative behavior of the hydrochemical parameters in the bottom waters was mainly caused by degradation of the phytoplankton biomass at the water/sediment interface. Hypoxic conditions were established in the bottom waters of the estuary in May.

The spatial and interannual dynamics of the surface water carbonate system and air-sea CO2 fluxes in the outer shelf and slope of the Eurasian Arctic Ocean

NASA Astrophysics Data System (ADS)

Pipko, Irina I.; Pugach, Svetlana P.; Semiletov, Igor P.; Anderson, Leif G.; Shakhova, Natalia E.; Gustafsson, Örjan; Repina, Irina A.; Spivak, Eduard A.; Charkin, Alexander N.; Salyuk, Anatoly N.; Shcherbakova, Kseniia P.; Panova, Elena V.; Dudarev, Oleg V.

2017-11-01

The Arctic is undergoing dramatic changes which cover the entire range of natural processes, from extreme increases in the temperatures of air, soil, and water, to changes in the cryosphere, the biodiversity of Arctic waters, and land vegetation. Small changes in the largest marine carbon pool, the dissolved inorganic carbon pool, can have a profound impact on the carbon dioxide (CO2) flux between the ocean and the atmosphere, and the feedback of this flux to climate. Knowledge of relevant processes in the Arctic seas improves the evaluation and projection of carbon cycle dynamics under current conditions of rapid climate change. Investigation of the CO2 system in the outer shelf and continental slope waters of the Eurasian Arctic seas (the Barents, Kara, Laptev, and East Siberian seas) during 2006, 2007, and 2009 revealed a general trend in the surface water partial pressure of CO2 (pCO2) distribution, which manifested as an increase in pCO2 values eastward. The existence of this trend was defined by different oceanographic and biogeochemical regimes in the western and eastern parts of the study area; the trend is likely increasing due to a combination of factors determined by contemporary change in the Arctic climate, each change in turn evoking a series of synergistic effects. A high-resolution in situ investigation of the carbonate system parameters of the four Arctic seas was carried out in the warm season of 2007; this year was characterized by the next-to-lowest historic sea-ice extent in the Arctic Ocean, on satellite record, to that date. The study showed the different responses of the seawater carbonate system to the environment changes in the western vs. the eastern Eurasian Arctic seas. The large, open, highly productive water area in the northern Barents Sea enhances atmospheric CO2 uptake. In contrast, the uptake of CO2 was strongly weakened in the outer shelf and slope waters of the East Siberian Arctic seas under the 2007 environmental conditions. The surface seawater appears in equilibrium or slightly supersaturated by CO2 relative to atmosphere because of the increasing influence of river runoff and its input of terrestrial organic matter that mineralizes, in combination with the high surface water temperature during sea-ice-free conditions. This investigation shows the importance of processes that vary on small scales, both in time and space, for estimating the air-sea exchange of CO2. It stresses the need for high-resolution coverage of ocean observations as well as time series. Furthermore, time series must include multi-year studies in the dynamic regions of the Arctic Ocean during these times of environmental change.

Climate and infectious disease: use of remote sensing for detection of Vibrio cholerae by indirect measurement

NASA Technical Reports Server (NTRS)

Lobitz, B.; Beck, L.; Huq, A.; Wood, B.; Fuchs, G.; Faruque, A. S.; Colwell, R.

2000-01-01

It has long been known that cholera outbreaks can be initiated when Vibrio cholerae, the bacterium that causes cholera, is present in drinking water in sufficient numbers to constitute an infective dose, if ingested by humans. Outbreaks associated with drinking or bathing in unpurified river or brackish water may directly or indirectly depend on such conditions as water temperature, nutrient concentration, and plankton production that may be favorable for growth and reproduction of the bacterium. Although these environmental parameters have routinely been measured by using water samples collected aboard research ships, the available data sets are sparse and infrequent. Furthermore, shipboard data acquisition is both expensive and time-consuming. Interpolation to regional scales can also be problematic. Although the bacterium, V. cholerae, cannot be sensed directly, remotely sensed data can be used to infer its presence. In the study reported here, satellite data were used to monitor the timing and spread of cholera. Public domain remote sensing data for the Bay of Bengal were compared directly with cholera case data collected in Bangladesh from 1992-1995. The remote sensing data included sea surface temperature and sea surface height. It was discovered that sea surface temperature shows an annual cycle similar to the cholera case data. Sea surface height may be an indicator of incursion of plankton-laden water inland, e.g., tidal rivers, because it was also found to be correlated with cholera outbreaks. The extensive studies accomplished during the past 25 years, confirming the hypothesis that V. cholerae is autochthonous to the aquatic environment and is a commensal of zooplankton, i.e., copepods, when combined with the findings of the satellite data analyses, provide strong evidence that cholera epidemics are climate-linked.

Post-fledging dispersal of king penguins (Aptenodytes patagonicus) from two breeding sites in the South Atlantic.

PubMed

Pütz, Klemens; Trathan, Phil N; Pedrana, Julieta; Collins, Martin A; Poncet, Sally; Lüthi, Benno

2014-01-01

Most studies concerning the foraging ecology of marine vertebrates are limited to breeding adults, although other life history stages might comprise half the total population. For penguins, little is known about juvenile dispersal, a period when individuals may be susceptible to increased mortality given their naïve foraging behaviour. Therefore, we used satellite telemetry to study king penguin fledglings (n = 18) from two sites in the Southwest Atlantic in December 2007. The two sites differed with respect to climate and proximity to the Antarctic Polar Front (APF), a key oceanographic feature generally thought to be important for king penguin foraging success. Accordingly, birds from both sites foraged predominantly in the vicinity of the APF. Eight king penguins were tracked for periods greater than 120 days; seven of these (three from the Falkland Islands and four from South Georgia) migrated into the Pacific. Only one bird from the Falkland Islands moved into the Indian Ocean, visiting the northern limit of the winter pack-ice. Three others from the Falkland Islands migrated to the eastern coast of Tierra del Fuego before travelling south. Derived tracking parameters describing their migratory behaviour showed no significant differences between sites. Nevertheless, generalized linear habitat modelling revealed that juveniles from the Falkland Islands spent more time in comparatively shallow waters with low sea surface temperature, sea surface height and chlorophyll variability. Birds from South Georgia spent more time in deeper waters with low sea surface temperature and sea surface height, but high concentrations of chlorophyll. Our results indicate that inexperienced king penguins, irrespective of the location of their natal site in relation to the position of the APF, develop their foraging skills progressively over time, including specific adaptations to the environment around their prospective breeding site.

Post-Fledging Dispersal of King Penguins (Aptenodytes patagonicus) from Two Breeding Sites in the South Atlantic

PubMed Central

Pütz, Klemens; Trathan, Phil N.; Pedrana, Julieta; Collins, Martin A.; Poncet, Sally; Lüthi, Benno

2014-01-01

Most studies concerning the foraging ecology of marine vertebrates are limited to breeding adults, although other life history stages might comprise half the total population. For penguins, little is known about juvenile dispersal, a period when individuals may be susceptible to increased mortality given their naïve foraging behaviour. Therefore, we used satellite telemetry to study king penguin fledglings (n = 18) from two sites in the Southwest Atlantic in December 2007. The two sites differed with respect to climate and proximity to the Antarctic Polar Front (APF), a key oceanographic feature generally thought to be important for king penguin foraging success. Accordingly, birds from both sites foraged predominantly in the vicinity of the APF. Eight king penguins were tracked for periods greater than 120 days; seven of these (three from the Falkland Islands and four from South Georgia) migrated into the Pacific. Only one bird from the Falkland Islands moved into the Indian Ocean, visiting the northern limit of the winter pack-ice. Three others from the Falkland Islands migrated to the eastern coast of Tierra del Fuego before travelling south. Derived tracking parameters describing their migratory behaviour showed no significant differences between sites. Nevertheless, generalized linear habitat modelling revealed that juveniles from the Falkland Islands spent more time in comparatively shallow waters with low sea surface temperature, sea surface height and chlorophyll variability. Birds from South Georgia spent more time in deeper waters with low sea surface temperature and sea surface height, but high concentrations of chlorophyll. Our results indicate that inexperienced king penguins, irrespective of the location of their natal site in relation to the position of the APF, develop their foraging skills progressively over time, including specific adaptations to the environment around their prospective breeding site. PMID:24828545

The Potentials Of Gnss-R For Sea Hazard Monitoring

NASA Astrophysics Data System (ADS)

Clarizia, Maria Paola; Toffoli, Alessandro

2013-04-01

GNSS-Reflectometry represents a new and innovative approach for ocean remote sensing. This technique exploits signals of opportunity from GNSS constellations (i.e. GPS, Glonass, Galileo etc.), reflected off the surface of the ocean, and uses these reflections to retrieve useful geophysical parameters of the ocean surface. GNSS-R is generating an increasing attention from the Remote Sensing community, especially in recent years, due to its numerous advantages compared to other classical remote sensing techniques. The exploitation of long-term, ubiquitous signals of opportunity freely available, the high space-time sampling capabilities and the ability of its L-band signals to penetrate well through rain all contribute to make this technique very attractive. An additional and very important strength of GNSS-R is the need for simple, low-cost/low-power GNSS receivers, that could be easily piggybacked on other satellites to form a constellation of receivers. These recognized potentials of GNSS-R have been recently led to the approval of the NASA EV-2 Cyclone Global Navigation Satellite System (CYGNSS), a spaceborne mission focused on tropical cyclone (TC) inner core process studies. GNSS-R can be used for both scatterometric applications (i.e. wind and wave monitoring) and altimetric applications (i.e. measurements of sea surface height). In particular, its ability to collect multiple GPS reflections anywhere on the globe and at any time (due to the ubiquity of GPS signals) using a large constellation of simple GNSS receivers, makes is very suitable for Real-Time (RT) and Near-Real Time (NRT) applications. These are particularly crucial for monitoring sea hazards related to ship operations and operational oceanography in general. For scatterometric purposes, GNSS-R can potentially detect high wind and waves in RT and NRT, as well as oil spills on the surface of the ocean, through its measurements of the sea surface roughness. In addition to that, GNSS-R could provide densely spaced Sea Surface Height (SSH) measurements, by collecting a number of reflections from different satellites within a field point of view. A number of sea hazards like tsunamis, high tides, storm surges of simply very high solitary waves in the ocean can be easily detected with GNSS-R measurements of SSH. The precision in the SSH measurement that can be achieved with GNSS-R is still considerably lower than that obtained with operational conventional altimetry. For this reason, GNSS-R is currently more suitable to detect large waves, since they generate a large signal in the data that allows for a better detection. The increase in the number of GNSS constellations and signals, and the improvements that the new signals will have (larger bandwidth, longer codes etc.) should ultimately lead to an overcome of the current limitations of GNSS for sea surface altimetry applications.

New data on earthquake focal mechanisms in the Laptev Sea region of the Arctic-Asian seismic belt

NASA Astrophysics Data System (ADS)

Seredkina, Alena I.; Melnikova, Valentina I.

2018-05-01

We consider 16 earthquakes with M w = 4.2-5.2 that occurred in the south-eastern part of the Laptev Sea shelf, Lena River Delta, and North Verkhoyanye (Russia) in 1990-2014. Focal mechanisms, scalar seismic moments, moment magnitudes, and hypocentral depths of the seismic events have been calculated from the data on amplitude spectra of surface waves and P wave first-motion polarities. The obtained results sufficiently implement the existing dataset on reliable earthquake source parameters for the study region and prove the change of the stress-strain state of the crust from extension on the Laptev Sea shelf to compression on the continent providing finer spatial details of the deformation field in the transition zones such as Buor-Khaya Bay and the Lena River Delta.

Distribution of sea anemones (Cnidaria, Actiniaria) in Korea analyzed by environmental clustering

USGS Publications Warehouse

Cha, H.-R.; Buddemeier, R.W.; Fautin, D.G.; Sandhei, P.

2004-01-01

Using environmental data and the geospatial clustering tools LOICZView and DISCO, we empirically tested the postulated existence and boundaries of four biogeographic regions in the southern part of the Korean peninsula. Environmental variables used included wind speed, sea surface temperature (SST), salinity, tidal amplitude, and the chlorophyll spectral signal. Our analysis confirmed the existence of four biogeographic regions, but the details of the borders between them differ from those previously postulated. Specimen-level distribution records of intertidal sea anemones were mapped; their distribution relative to the environmental data supported the importance of the environmental parameters we selected in defining suitable habitats. From the geographic coincidence between anemone distribution and the clusters based on environmental variables, we infer that geospatial clustering has the power to delimit ranges for marine organisms within relatively small geographical areas.

Increasing cloudiness in Arctic damps the increase in phytoplankton primary production due to sea ice receding

NASA Astrophysics Data System (ADS)

Bélanger, S.; Babin, M.; Tremblay, J.-É.

2013-06-01

The Arctic Ocean and its marginal seas are among the marine regions most affected by climate change. Here we present the results of a diagnostic model used to assess the primary production (PP) trends over the 1998-2010 period at pan-Arctic, regional and local (i.e. 9.28 km resolution) scales. Photosynthetically active radiation (PAR) above and below the sea surface was estimated using precomputed look-up tables of spectral irradiance, taking as input satellite-derived cloud optical thickness and cloud fraction parameters from the International Satellite Cloud Climatology Project (ISCCP) and sea ice concentration from passive microwaves data. A spectrally resolved PP model, designed for optically complex waters, was then used to assess the PP trends at high spatial resolution. Results show that PP is rising at a rate of +2.8 TgC yr-1 (or +14% decade-1) in the circum-Arctic and +5.1 TgC yr-1 when sub-Arctic seas are considered. In contrast, incident PAR above the sea surface (PAR(0+)) has significantly decreased over the whole Arctic and sub-Arctic Seas, except over the perennially sea-ice covered waters of the Central Arctic Ocean. This fading of PAR(0+) (-8% decade-1) was caused by increasing cloudiness during summer. Meanwhile, PAR penetrating the ocean (PAR(0-)) increased only along the sea ice margin over the large Arctic continental shelf where sea ice concentration declined sharply since 1998. Overall, PAR(0-) slightly increased in the circum-Arctic (+3.4% decade-1), while it decreased when considering both Arctic and sub-Arctic Seas (-3% decade-1). We showed that rising phytoplankton biomass (i.e. chlorophyll a) normalized by the diffuse attenuation of photosynthetically usable radiation (PUR), accounted for a larger proportion of the rise in PP than did the increase in light availability due to sea-ice loss in several sectors, and particularly in perennially and seasonally open waters. Against a general backdrop of rising productivity over Arctic shelves, significant negative PP trends and the timing of phytoplankton spring-summer bloom were observed in regions known for their great biological importance such as the coastal polynyas of northern Greenland.

Dinoflagellate and calcareous nannofossil response to sea-level change in Cretaceous-Tertiary boundary sections

DOE Office of Scientific and Technical Information (OSTI.GOV)

Habib, D.; Moshkovitz, S.; Kramer, C.

1992-02-01

Stratigraphic sections in south-central Alabama were studied to test palynological evidence of sea-level change across the Cretaceous-Tertiary boundary. New evidence from both calcareous nannofossils and dinoflagellate cysts places the regional disconformity in Alabama (Type 1 sequence boundary) virtually at the K-T boundary. This suggests that sea-level fall may have contributed to mass-extinction event. Dinoflagellate diversity varies between systems tract components of coastal onlap. This parameter is useful for interpreting sea-level change in this part of the section, because dinoflagellates did not participate in the mass extinction. The iridium spikes in the roadcut near Braggs are of earliest Danian age andmore » correlate in relative magnitude with the lower values reported from directly above the K-T boundary in the Gubbio stratotype section. Iridium was concentrated in marine flooding surfaces in episodes of higher productivity of algal organic matter at the time when the iridium-enriched ocean encroached on the shelf during the first Cenozoic episode of sea-level rise.« less

Wintertime Air-Sea Gas Transfer Rates and Air Injection Fluxes at Station Papa in the NE Pacific

NASA Astrophysics Data System (ADS)

McNeil, C.; Steiner, N.; Vagle, S.

2008-12-01

In recent studies of air-sea fluxes of N2 and O2 in hurricanes, McNeil and D'Asaro (2007) used a simplified model formulation of air-sea gas flux to estimate simultaneous values of gas transfer rate, KT, and air injection flux, VT. The model assumes air-sea gas fluxes at high to extreme wind speeds can be explained by a combination of two processes: 1) air injection, by complete dissolution of small bubbles drawn down into the ocean boundary layer by turbulent currents, and 2) near-surface equilibration processes, such as occurs within whitecaps. This analysis technique relies on air-sea gas flux estimates for two gases, N2 and O2, to solve for the two model parameters, KT and VT. We present preliminary results of similar analysis of time series data collected during winter storms at Station Papa in the NE Pacific during 2003/2004. The data show a clear increase in KT and VT with increasing NCEP derived wind speeds and acoustically measured bubble penetration depth.

Short-term Influences on Suspended Particulate Matter Distribution in the Northern Gulf of Mexico: Satellite and Model Observations.

PubMed

D'Sa, Eurico J; Ko, Dong S

2008-07-15

Energetic meteorological events such as frontal passages and hurricanes often impact coastal regions in the northern Gulf of Mexico that influence geochemical processes in the region. Satellite remote sensing data such as winds from QuikSCAT, suspended particulate matter (SPM) concentrations derived from SeaWiFS and the outputs (sea level and surface ocean currents) of a nested navy coastal ocean model (NCOM) were combined to assess the effects of frontal passages between 23-28 March 2005 on the physical properties and the SPM characteristics in the northern Gulf of Mexico. Typical changes in wind speed and direction associated with frontal passages were observed in the latest 12.5 km wind product from QuikSCAT with easterly winds before the frontal passage undergoing systematic shifts in direction and speed and turning northerly, northwesterly during a weak and a strong front on 23 and 27 March, respectively. A quantitative comparison of model sea level results with tide gauge observations suggest better correlations near the delta than in the western part of the Gulf with elevated sea levels along the coast before the frontal passage and a large drop in sea level following the frontal passage on 27 March. Model results of surface currents suggested strong response to wind forcing with westward and onshore currents before the frontal passage reversing into eastward, southeastward direction over a six day period from 23 to 28 March 2005. Surface SPM distribution derived from SeaWiFS ocean color data for two clear days on 23 and 28 March 2005 indicated SPM plumes to be oriented with the current field with increasing concentrations in nearshore waters due to resuspension and discharge from the rivers and bays and its seaward transport following the frontal passage. The backscattering spectral slope γ, a parameter sensitive to particle size distribution also indicated lower γ values (larger particles) in nearshore waters that decreased offshore (smaller particles). The use of both satellite and model results revealed the strong interactions between physical processes and the surface particulate field in response to the frontal passage in a large riverdominated coastal margin.

Sun-stirred Kraken Mare: Circulation in Titan's seas induced by solar heating and methane precipitation

NASA Astrophysics Data System (ADS)

Tokano, Tetsuya; Lorenz, Ralph D.

2016-05-01

Density-driven circulation in Titan's seas forced by solar heating and methane evaporation/precipitation is simulated by an ocean circulation model. If the sea is transparent to sunlight, solar heating can induce anti-clockwise gyres near the sea surface and clockwise gyres near the sea bottom. The gyres are in geostrophic balance between the radially symmetric pressure gradient force and Coriolis force. If instead the sea is turbid and most sunlight is absorbed near the sea surface, the sea gets stratified in warm seasons and the circulation remains weak. Precipitation causes compositional stratification of the sea to an extent that the sea surface temperature can be lower than the sea interior temperature without causing a convective overturning. Non-uniform precipitation can also generate a latitudinal gradient in the methane mole fraction and density, which drives a meridional overturning with equatorward currents near the sea surface and poleward currents near the sea bottom. However, gyres are more ubiquitous than meridional overturning.

The Impact of Sea Surface Temperature Front on Stratus-Sea Fog over the Yellow and East China Seas

NASA Astrophysics Data System (ADS)

Zhang, S.; Li, M.; Liu, F.

2013-12-01

A stratus-sea fog event occurred on 3 June 2011 over the Yellow and East China Seas (as shown in figure) is investigated observationally and numerically. Emphasis is put on the influences of the sea surface temperature front (SSTF) and of the synoptic circulations on the transition of stratus to sea fog. The southerly winds from a synoptic high pressure transport water vapor from the East China Sea to the Yellow Sea, while the subsidence induced by the high contributes to the formation of the temperature inversion on the top of the stratus or stratocumulus that appears mainly over the warm flank of a sea surface temperature front in the East China Sea. Forced by the SSTF, there is a secondary cell within the atmospheric boundary layer (ABL), with a sinking branch on the cold flank and a rising one on the warm flank of the SSTF. This sinking branch, in phase with the synoptic subsidence, forces the stratus or stratocumulus to lower in the elevation getting close to the sea surface as these clouds move northward driven by the southerly winds. The cloud droplets can either reach to the sea surface directly or evaporate into water vapor that may condense again when coming close to the cold sea surface to form fog. In this later case, the stratus and fog may separate. The cooling effect of cold sea surface counteracts the adiabatic heating induced by the subsidence and thus helps the transition of stratus to sea fog in the southern Yellow Sea. By smoothing the SSTF in the numerical experiment, the secondary cell weakens and the sea fog patches shrink obviously over the cold flank of the SSTF though the synoptic subsidence and moist advection still exist. A conceptual model is suggested for the transition of stratus to sea fog in the Yellow and East China Seas, which is helpful for the forecast of sea fog over these areas. The satellite visible image of the stratus-fog event. The fog appears in the Yellow Sea and the stratocumulus in the East China Sea.

Effects of Sea-Surface Waves and Ocean Spray on Air-Sea Momentum Fluxes

NASA Astrophysics Data System (ADS)

Zhang, Ting; Song, Jinbao

2018-04-01

The effects of sea-surface waves and ocean spray on the marine atmospheric boundary layer (MABL) at different wind speeds and wave ages were investigated. An MABL model was developed that introduces a wave-induced component and spray force to the total surface stress. The theoretical model solution was determined assuming the eddy viscosity coefficient varied linearly with height above the sea surface. The wave-induced component was evaluated using a directional wave spectrum and growth rate. Spray force was described using interactions between ocean-spray droplets and wind-velocity shear. Wind profiles and sea-surface drag coefficients were calculated for low to high wind speeds for wind-generated sea at different wave ages to examine surface-wave and ocean-spray effects on MABL momentum distribution. The theoretical solutions were compared with model solutions neglecting wave-induced stress and/or spray stress. Surface waves strongly affected near-surface wind profiles and sea-surface drag coefficients at low to moderate wind speeds. Drag coefficients and near-surface wind speeds were lower for young than for old waves. At high wind speeds, ocean-spray droplets produced by wind-tearing breaking-wave crests affected the MABL strongly in comparison with surface waves, implying that wave age affects the MABL only negligibly. Low drag coefficients at high wind caused by ocean-spray production increased turbulent stress in the sea-spray generation layer, accelerating near-sea-surface wind. Comparing the analytical drag coefficient values with laboratory measurements and field observations indicated that surface waves and ocean spray significantly affect the MABL at different wind speeds and wave ages.

Measurements of CO{sub 2} fluxes and bubbles from a tower during ASGASEX

DOE Office of Scientific and Technical Information (OSTI.GOV)

Leeuw, G. de; Kunz, G.J.; Larsen, S.E.

1994-12-31

The Air-Sea Gas Exchange experiment ASGASEX was conducted from August 30 until October 1st from the Meetpost Noordwijk (MPN), a research tower in the North Sea at 9 km from the Dutch coast. The objective of ASGASEX was a study of parameters affecting the air-sea exchange of gases, and a comparison of experimental methods to derive the exchange coefficient for CO{sub 2}. A detailed description of the ASGASEX experiment is presented in Oost. The authors` contribution to ASGASEX was a micro-meteorological package to measure the fluxes of CO{sub 2}, momentum, heat and water vapor, and an instrument to measure themore » size distribution of bubbles just below the sea surface. In this contribution the authors report preliminary results from the CO{sub 2} flux measurements and the bubble measurements. The latter was made as part of a larger study on the influence of bubbles on gas exchange in cooperation with the University of Southampton and the University of Galway.« less

Sensitivity of the sea ice concentration over the Kara-Barents Sea in autumn to the winter temperature variability over East Asia

NASA Astrophysics Data System (ADS)

Cho, K. H.; Chang, E. C.

2017-12-01

In this study, we performed sensitivity experiments by utilizing the Global/Regional Integrated Model system with different conditions of the sea ice concentration over the Kara-Barents (KB) Sea in autumn, which can affect winter temperature variability over East Asia. Prescribed sea ice conditions are 1) climatological autumn sea ice concentration obtained from 1982 to 2016, 2) reduced autumn sea ice concentration by 50% of the climatology, and 3) increased autumn sea ice concentration by 50% of climatology. Differently prescribed sea ice concentration changes surface albedo, which affects surface heat fluxes and near-surface air temperature. The reduced (increased) sea ice concentration over the KB sea increases (decreases) near-surface air temperature that leads the lower (higher) sea level pressure in autumn. These patterns are maintained from autumn to winter season. Furthermore, it is shown that the different sea ice concentration over the KB sea has remote effects on the sea level pressure patterns over the East Asian region. The lower (higher) sea level pressure over the KB sea by the locally decreased (increased) ice concentration is related to the higher (lower) pressure pattern over the Siberian region, which induces strengthened (weakened) cold advection over the East Asian region. From these sensitivity experiments it is clarified that the decreased (increased) sea ice concentration over the KB sea in autumn can lead the colder (warmer) surface air temperature over East Asia in winter.

The mean sea surface height and geoid along the Geosat subtrack from Bermuda to Cape Cod

NASA Astrophysics Data System (ADS)

Kelly, Kathryn A.; Joyce, Terrence M.; Schubert, David M.; Caruso, Michael J.

1991-07-01

Measurements of near-surface velocity and concurrent sea level along an ascending Geosat subtrack were used to estimate the mean sea surface height and the Earth's gravitational geoid. Velocity measurements were made on three traverses of a Geosat subtrack within 10 days, using an acoustic Doppler current profiler (ADCP). A small bias in the ADCP velocity was removed by considering a mass balance for two pairs of triangles for which expendable bathythermograph measurements were also made. Because of the large curvature of the Gulf Stream, the gradient wind balance was used to estimate the cross-track component of geostrophic velocity from the ADCP vectors; this component was then integrated to obtain the sea surface height profile. The mean sea surface height was estimated as the difference between the instantaneous sea surface height from ADCP and the Geosat residual sea level, with mesoscale errors reduced by low-pass filtering. The error estimates were divided into a bias, tilt, and mesoscale residual; the bias was ignored because profiles were only determined within a constant of integration. The calculated mean sea surface height estimate agreed with an independent estimate of the mean sea surface height from Geosat, obtained by modeling the Gulf Stream as a Gaussian jet, within the expected errors in the estimates: the tilt error was 0.10 m, and the mesoscale error was 0.044 m. To minimize mesoscale errors in the estimate, the alongtrack geoid estimate was computed as the difference between the mean sea level from the Geosat Exact Repeat Mission and an estimate of the mean sea surface height, rather than as the difference between instantaneous profiles of sea level and sea surface height. In the critical region near the Gulf Stream the estimated error reduction using this method was about 0.07 m. Differences between the geoid estimate and a gravimetric geoid were not within the expected errors: the rms mesoscale difference was 0.24 m rms.

Spatio-temporal reproducibility of the microbial food web structure associated with the change in temperature: Long-term observations in the Adriatic Sea

NASA Astrophysics Data System (ADS)

Šolić, Mladen; Grbec, Branka; Matić, Frano; Šantić, Danijela; Šestanović, Stefanija; Ninčević Gladan, Živana; Bojanić, Natalia; Ordulj, Marin; Jozić, Slaven; Vrdoljak, Ana

2018-02-01

Global and atmospheric climate change is altering the thermal conditions in the Adriatic Sea and, consequently, the marine ecosystem. Along the eastern Adriatic coast sea surface temperature (SST) increased by an average of 1.03 °C during the period from 1979 to 2015, while in the recent period, starting from 2008, a strong upward almost linear trend of 0.013 °C/month was noted. Being mainly oligotrophic, the middle Adriatic Sea is characterized by the important role played by the microbial food web in the production and transfer of biomass and energy towards higher trophic levels. It is very important to understand the effect of warming on microbial communities, since small temperature increases in surface seawater can greatly modify the microbial role in the global carbon cycle. In this study, the Self-Organizing Map (SOM) procedure was used to analyse the time series of a number of microbial parameters at two stations with different trophic status in the central Adriatic Sea. The results show that responses of the microbial food web (MFW) structure to temperature changes are reproducible in time. Furthermore, qualitatively similar changes in the structure of the MFW occurred regardless of the trophic status. The rise in temperature was associated with: (1) the increasing importance of microbial heterotrophic activities (increase bacterial growth and bacterial predator abundance, particularly heterotrophic nanoflagellates) and (2) the increasing importance of autotrophic picoplankton (APP) in the MFW.

Improvement of the AeroClipper system for cyclones monitoring

NASA Astrophysics Data System (ADS)

Vargas, André; Philippe, Duvel Jean

2016-07-01

The AeroClipper developed by the French space agency (Centre National d'Études Spatiales, CNES) is a quasi-lagrangian device drifting with surface wind at about 20-30m above the ocean surface. It is a new and original device for real-time and continuous observation of air-sea surface parameters in open ocean remote regions. This device enables the sampling of the variability of surface parameters in particular under convective systems toward which it is attracted. The AeroClipper is therefore an ideal instrument to monitor Tropical Cyclones (TCs) in which they are likely to converge and provide original observations to evaluate and improve our current understanding and diagnostics of TCs as well as their representation in numerical models. In 2008, the AeroClipper demonstrates its capability to be captured by an Ocean Indian cyclone, as two models have converged, without damages, in the eye of Dora cyclone during the 2008 VASCO campaign. This paper will present the improvements of this balloon system for the international project 'the Year of Maritime Continent'.

Enhancing the Arctic Mean Sea Surface and Mean Dynamic Topography with CryoSat-2 Data

NASA Astrophysics Data System (ADS)

Stenseng, Lars; Andersen, Ole B.; Knudsen, Per

2014-05-01

A reliable mean sea surface (MSS) is essential to derive a good mean dynamic topography (MDT) and for the estimation of short and long-term changes in the sea surface. The lack of satellite radar altimetry observations above 82 degrees latitude means that existing mean sea surface models have been unreliable in the Arctic Ocean. We here present the latest DTU mean sea surface and mean dynamic topography models that includes CryoSat-2 data to improve the reliability in the Arctic Ocean. In an attempt to extrapolate across the gap above 82 degrees latitude the previously models included ICESat data, gravimetrical geoids, ocean circulation models and various combinations hereof. Unfortunately cloud cover and the short periods of operation has a negative effect on the number of ICESat sea surface observations. DTU13MSS and DTU13MDT are the new generation of state of the art global high-resolution models that includes CryoSat-2 data to extend the satellite radar altimetry coverage up to 88 degrees latitude. Furthermore the SAR and SARin capability of CryoSat-2 dramatically increases the amount of useable sea surface returns in sea-ice covered areas compared to conventional radar altimeters like ENVISAT and ERS-1/2. With the inclusion of CryoSat-2 data the new mean sea surface is improved by more than 20 cm above 82 degrees latitude compared with the previous generation of mean sea surfaces.

Aerosol direct effect on solar radiation over the eastern Mediterranean Sea based on AVHRR satellite measurements

NASA Astrophysics Data System (ADS)

Georgakaki, Paraskevi; Papadimas, Christos D.; Hatzianastassiou, Nikos; Fotiadi, Aggeliki; Matsoukas, Christos; Stackhouse, Paul; Kanakidou, Maria; Vardavas, Ilias M.

2017-04-01

Despite the improved scientific understanding of the direct effect of aerosols on solar radiation (direct radiative effect, DRE) improvements are necessary, for example regarding the accuracy of the magnitude of estimated DREs and their spatial and temporal variability. This variability cannot be ensured by in-situ surface and airborne measurements, while it is also relatively difficult to capture through satellite observations. This becomes even more difficult when complete spatial coverage of extended areas is required, especially concerning areas that host various aerosol types with variable physico-chemical and optical aerosol properties. Better assessments of aerosol DREs are necessary, relying on aerosol optical properties with high spatial and temporal variation. The present study aims to provide a refined, along these lines, assessment of aerosol DREs over the eastern Mediterranean (EM) Sea, which is a key area for aerosol studies. Daily DREs are computed for 1˚ x1˚ latitude-longitude grids with the FORTH detailed spectral radiation transfer model (RTM) using input data for various atmospheric and surface parameters, such as clouds, water vapor, ozone and surface albedo, taken from the NASA-Langley Global Earth Observing System (GEOS) database. The model spectral aerosol optical depth (AOD), single scattering albedo and asymmetry parameter are taken from the Global Aerosol Data Set and the NOAA Climate Data Record (CDR) version 2 of Advanced Very High resolution Radiometer (AVHRR) AOD dataset which is available over oceans at 0.63 microns and at 0.1˚ x0.1˚ . The aerosol DREs are computed at the surface, the top-of-atmosphere and within the atmosphere, over the period 1985-1995. Preliminary model results for the period 1990-1993 reveal a significant spatial and temporal variability of DREs over the EM Sea, for example larger values over the Aegean and Black Seas, surrounded by land areas with significant anthropogenic aerosol sources, and over the southernmost parts of EM Sea, affected by frequent Saharan dust export. The mean regional annual AODs range from 0.17±0.05 to 0.23±0.06. The corresponding regional annual DREs at surface range from -14±3 to -18±4 W/m2 (surface radiative cooling), while in the atmosphere they vary between 7±2 and 10±2 W/m2 (atmospheric heating), yielding a planetary cooling above the EM Sea between -6±1 and -8±2 W/m2. However, these AOD and DRE values vary depending on the criteria of data spatial and temporal availability applied in the AOD and DRE calculation, because of the limited availability of retrieved AVHRR AOD over specific areas and in specific days. The DREs reach larger magnitudes at pixel-level; for example the surface DREs slightly exceed -30 W/m2, whereas they take larger values (magnitudes larger than -50 W/m2 in summer) when computed on a monthly basis, and even larger values on daily basis. The model results underline the high spatial and temporal variability of aerosol DREs, and the care that must be taken when averaging over space and time. It also points to the need for availability of aerosol data with concurrent high spatial and temporal coverage and resolution, which should be sought in ongoing and future satellite missions.

Polarimetric Doppler spectrum of backscattered echoes from nonlinear sea surface damped by natural slicks

NASA Astrophysics Data System (ADS)

Yang, Pengju; Guo, Lixin

2016-11-01

Based on the Lombardini et al. model that can predict the hydrodynamic damping of rough sea surfaces in the presence of monomolecular slicks and the "choppy wave" model (CWM) that can describe the nonlinear interactions between ocean waves, the modeling of time-varying nonlinear sea surfaces damped by natural or organic sea slicks is presented in this paper. The polarimetric scattering model of second-order small-slope approximation (SSA-II) with tapered wave incidence is utilized for evaluating co- and cross-polarized backscattered echoes from clean and contaminated CWM nonlinear sea surfaces. The influence of natural sea slicks on Doppler shift and spectral bandwidth of radar sea echoes is investigated in detail by comparing the polarimetric Doppler spectra of contaminated sea surfaces with those of clean sea surfaces. A narrowing of Doppler spectra in the presence of oil slicks is observed for both co- and cross-polarization, which is qualitatively consistent with wave-tank measurements. Simulation results also show that the Doppler shifts in slicks can increase or decrease, depending on incidence angles and polarizations.

Using a 4D-Variational Method to Optimize Model Parameters in an Intermediate Coupled Model of ENSO

NASA Astrophysics Data System (ADS)

Gao, C.; Zhang, R. H.

2017-12-01

Large biases exist in real-time ENSO prediction, which is attributed to uncertainties in initial conditions and model parameters. Previously, a four dimentional variational (4D-Var) data assimilation system was developed for an intermediate coupled model (ICM) and used to improve ENSO modeling through optimized initial conditions. In this paper, this system is further applied to optimize model parameters. In the ICM used, one important process for ENSO is related to the anomalous temperature of subsurface water entrained into the mixed layer (Te), which is empirically and explicitly related to sea level (SL) variation, written as Te=αTe×FTe (SL). The introduced parameter, αTe, represents the strength of the thermocline effect on sea surface temperature (SST; referred as the thermocline effect). A numerical procedure is developed to optimize this model parameter through the 4D-Var assimilation of SST data in a twin experiment context with an idealized setting. Experiments having initial condition optimized only and having initial condition plus this additional model parameter optimized both are compared. It is shown that ENSO evolution can be more effectively recovered by including the additional optimization of this parameter in ENSO modeling. The demonstrated feasibility of optimizing model parameter and initial condition together through the 4D-Var method provides a modeling platform for ENSO studies. Further applications of the 4D-Var data assimilation system implemented in the ICM are also discussed.

Detailed real-time infrared radiation simulation applied to the sea surface

NASA Astrophysics Data System (ADS)

Zhang, Xuemin; Wu, Limin; Long, Liang; Zhang, Lisha

2018-01-01

In this paper, the infrared radiation characteristics of sea background have been studied. First, MODTRAN4.0 was used to calculate the transmittance of mid-infrared and far-infrared, and the solar spectral irradiance, the atmospheric and sea surface radiation. Secondly, according to the JONSWAP sea spectrum model, the different sea conditions grid model based on gravity wave theory was generated. The spectral scattering of the sun and the atmospheric background radiation was studied. The total infrared radiation of the sea surface was calculated. Finally, the infrared radiation of a piece of sea surface was mapped to each pixel of the detector, and the infrared radiation is simulated. The conclusion is that solar radiance has a great influence on the infrared radiance. When the detector angle is close to the sun's height angle, there will be bright spots on the sea surface.

Simple Rules Govern the Patterns of Arctic Sea Ice Melt Ponds

NASA Astrophysics Data System (ADS)

Popović, Predrag; Cael, B. B.; Silber, Mary; Abbot, Dorian S.

2018-04-01

Climate change, amplified in the far north, has led to rapid sea ice decline in recent years. In the summer, melt ponds form on the surface of Arctic sea ice, significantly lowering the ice reflectivity (albedo) and thereby accelerating ice melt. Pond geometry controls the details of this crucial feedback; however, a reliable model of pond geometry does not currently exist. Here we show that a simple model of voids surrounding randomly sized and placed overlapping circles reproduces the essential features of pond patterns. The only two model parameters, characteristic circle radius and coverage fraction, are chosen by comparing, between the model and the aerial photographs of the ponds, two correlation functions which determine the typical pond size and their connectedness. Using these parameters, the void model robustly reproduces the ponds' area-perimeter and area-abundance relationships over more than 6 orders of magnitude. By analyzing the correlation functions of ponds on several dates, we also find that the pond scale and the connectedness are surprisingly constant across different years and ice types. Moreover, we find that ponds resemble percolation clusters near the percolation threshold. These results demonstrate that the geometry and abundance of Arctic melt ponds can be simply described, which can be exploited in future models of Arctic melt ponds that would improve predictions of the response of sea ice to Arctic warming.

Biogeochemical regions of the Mediterranean Sea: An objective multidimensional and multivariate environmental approach

NASA Astrophysics Data System (ADS)

Reygondeau, Gabriel; Guieu, Cécile; Benedetti, Fabio; Irisson, Jean-Olivier; Ayata, Sakina-Dorothée; Gasparini, Stéphane; Koubbi, Philippe

2017-02-01

When dividing the ocean, the aim is generally to summarise a complex system into a representative number of units, each representing a specific environment, a biological community or a socio-economical specificity. Recently, several geographical partitions of the global ocean have been proposed using statistical approaches applied to remote sensing or observations gathered during oceanographic cruises. Such geographical frameworks defined at a macroscale appear hardly applicable to characterise the biogeochemical features of semi-enclosed seas that are driven by smaller-scale chemical and physical processes. Following the Longhurst's biogeochemical partitioning of the pelagic realm, this study investigates the environmental divisions of the Mediterranean Sea using a large set of environmental parameters. These parameters were informed in the horizontal and the vertical dimensions to provide a 3D spatial framework for environmental management (12 regions found for the epipelagic, 12 for the mesopelagic, 13 for the bathypelagic and 26 for the seafloor). We show that: (1) the contribution of the longitudinal environmental gradient to the biogeochemical partitions decreases with depth; (2) the partition of the surface layer cannot be extrapolated to other vertical layers as the partition is driven by a different set of environmental variables. This new partitioning of the Mediterranean Sea has strong implications for conservation as it highlights that management must account for the differences in zoning with depth at a regional scale.

Simple Rules Govern the Patterns of Arctic Sea Ice Melt Ponds.

PubMed

Popović, Predrag; Cael, B B; Silber, Mary; Abbot, Dorian S

2018-04-06

Climate change, amplified in the far north, has led to rapid sea ice decline in recent years. In the summer, melt ponds form on the surface of Arctic sea ice, significantly lowering the ice reflectivity (albedo) and thereby accelerating ice melt. Pond geometry controls the details of this crucial feedback; however, a reliable model of pond geometry does not currently exist. Here we show that a simple model of voids surrounding randomly sized and placed overlapping circles reproduces the essential features of pond patterns. The only two model parameters, characteristic circle radius and coverage fraction, are chosen by comparing, between the model and the aerial photographs of the ponds, two correlation functions which determine the typical pond size and their connectedness. Using these parameters, the void model robustly reproduces the ponds' area-perimeter and area-abundance relationships over more than 6 orders of magnitude. By analyzing the correlation functions of ponds on several dates, we also find that the pond scale and the connectedness are surprisingly constant across different years and ice types. Moreover, we find that ponds resemble percolation clusters near the percolation threshold. These results demonstrate that the geometry and abundance of Arctic melt ponds can be simply described, which can be exploited in future models of Arctic melt ponds that would improve predictions of the response of sea ice to Arctic warming.

Preliminary results of fisheries investigation associated with Skylab-3

NASA Technical Reports Server (NTRS)

Savastano, K.; Pastula, E., Jr.; Woods, G.; Faller, K.

1974-01-01

The purpose of the 15-month investigation now in the analysis phase is to establish the feasibility of utilizing remotely sensed data acquired from aircraft and satellite platforms to provide information concerning the distribution and abundance of oceanic gamefish. Data from the test area, jointly acquired by private and professional fishermen and NASA and NOAA/NMFS elements, in the northeastern Gulf of Mexico has made possible the identification of significant environmental parameters for white marlin. Predictive models based on catch data and surface truth information have been developed and have demonstrated potential for reducing search significantly by identifying areas which have a high probability of being productive. Three of the parameters utilized by the model, chlorophyll-a, sea surface temperature and turbidity have been inferred from aircraft sensor data.

An Investigation of the Radiative Effects and Climate Feedbacks of Sea Ice Sources of Sea Salt Aerosol

NASA Astrophysics Data System (ADS)

Horowitz, H. M.; Alexander, B.; Bitz, C. M.; Jaegle, L.; Burrows, S. M.

2017-12-01

In polar regions, sea ice is a major source of sea salt aerosol through lofting of saline frost flowers or blowing saline snow from the sea ice surface. Under continued climate warming, an ice-free Arctic in summer with only first-year, more saline sea ice in winter is likely. Previous work has focused on climate impacts in summer from increasing open ocean sea salt aerosol emissions following complete sea ice loss in the Arctic, with conflicting results suggesting no net radiative effect or a negative climate feedback resulting from a strong first aerosol indirect effect. However, the radiative forcing from changes to the sea ice sources of sea salt aerosol in a future, warmer climate has not previously been explored. Understanding how sea ice loss affects the Arctic climate system requires investigating both open-ocean and sea ice sources of sea-salt aerosol and their potential interactions. Here, we implement a blowing snow source of sea salt aerosol into the Community Earth System Model (CESM) dynamically coupled to the latest version of the Los Alamos sea ice model (CICE5). Snow salinity is a key parameter affecting blowing snow sea salt emissions and previous work has assumed constant regional snow salinity over sea ice. We develop a parameterization for dynamic snow salinity in the sea ice model and examine how its spatial and temporal variability impacts the production of sea salt from blowing snow. We evaluate and constrain the snow salinity parameterization using available observations. Present-day coupled CESM-CICE5 simulations of sea salt aerosol concentrations including sea ice sources are evaluated against in situ and satellite (CALIOP) observations in polar regions. We then quantify the present-day radiative forcing from the addition of blowing snow sea salt aerosol with respect to aerosol-radiation and aerosol-cloud interactions. The relative contributions of sea ice vs. open ocean sources of sea salt aerosol to radiative forcing in polar regions is discussed.

Influence of the Surface and Cloud Nonuniformities in the Solar Energy Fluxes in the Arctic

NASA Technical Reports Server (NTRS)

Rozwadowska, A.; Cahalan, R. F.; Einaudi, Franco (Technical Monitor)

2000-01-01

Solar energy fluxes reaching the surface and absorbed by it are basic components of the energy balance of the Arctic. They depend mainly on the solar zenith angle, a state of the atmosphere, especially the cloudiness, and the surface albedo. However, they can also be modified by variabilities in the surface albedo and cloud optical thickness. The surface of the Arctic can be highly nonuniform. The surface of the Arctic Ocean, which covers the huge part of the Arctic can be view as a mosaic of sea water, sea ice, snow and, in the melting period, melting ponds. In our paper, results are presented of Monte Carlo simulations of the expected influence of nonuniform cloud structure and nonuniform surface albedo on radiative fluxes at the Arctic surface. In particular, the plane parallel biases in the surface absorptance and atmospheric transmittance are studied. The bias is defined as the difference between the real absorptance or transmittance (i.e. nonuniform conditions) averaged over a given area, and the uniform or plane parallel case with the same mean cloud optical thickness and the same mean surface albedo. The dependence of the biases is analysed with respect to the following: domain averaged values of the cloud optical thickness and surface albedo, scales of their spatial variabilities, correlation between cloud optical thickness and cloud albedo variabilities, cloud height, and the solar zenith angle. Ranges of means and standard deviations of the input parameters typical of Arctic conditions are obtained from the SHEBA experiment.

Sea-surface temperature gradients across blue whale and sea turtle foraging trajectories off the Baja California Peninsula, Mexico

NASA Astrophysics Data System (ADS)

Etnoyer, Peter; Canny, David; Mate, Bruce R.; Morgan, Lance E.; Ortega-Ortiz, Joel G.; Nichols, Wallace J.

2006-02-01

Sea-surface temperature (SST) fronts are integral to pelagic ecology in the North Pacific Ocean, so it is necessary to understand their character and distribution, and the way these features influence the behavior of endangered and highly migratory species. Here, telemetry data from sixteen satellite-tagged blue whales ( Balaenoptera musculus) and sea turtles ( Caretta caretta, Chelonia mydas, and Lepidochelys olivacea) are employed to characterize 'biologically relevant' SST fronts off Baja California Sur. High residence times are used to identify presumed foraging areas, and SST gradients are calculated across advanced very high resolution radiometer (AVHRR) images of these regions. The resulting values are compared to classic definitions of SST fronts in the oceanographic literature. We find subtle changes in surface temperature (between 0.01 and 0.10 °C/km) across the foraging trajectories, near the lowest end of the oceanographic scale (between 0.03 and 0.3 °C/km), suggesting that edge-detection algorithms using gradient thresholds >0.10 °C/km may overlook pelagic habitats in tropical waters. We use this information to sensitize our edge-detection algorithm, and to identify persistent concentrations of subtle SST fronts in the Northeast Pacific Ocean between 2002 and 2004. The lower-gradient threshold increases the number of fronts detected, revealing more potential habitats in different places than we find with a higher-gradient threshold. This is the expected result, but it confirms that pelagic habitat can be overlooked, and that the temperature gradient parameter is an important one.

Elements of the tsunami precursors' detection physics

NASA Astrophysics Data System (ADS)

Novik, Oleg; Ruzhin, Yuri; Ershov, Sergey; Volgin, Max; Smirnov, Fedor

In accordance with the main physical principles and geophysical data, we formulated a nonlinear mathematical model of seismo-hydro-electromagnetic (EM) geophysical field interaction and calculated generation and propagation of elastic, EM, temperature and hydrodynamic seismically generated disturbances (i.e. signals) in the basin of a marginal sea. We show transferring of seismic and electromagnetic (EM) energy from the upper mantle beneath the sea into its depths and EM emission from the sea surface into the atmosphere. Basing on the calculated characteristics of the signals of different physical nature (computations correspond to measurements of other authors) we develop the project of a Lithosphere-Ocean-Atmosphere Monitoring System (LOAMS) including: a bottom complex, a moored ocean surface buoy complex, an observational balloon complex, and satellite complex. The underwater stations of the bottom complex of the LOAMS will record the earlier signals of seismic activation beneath a seafloor (the ULF EM signals outrun seismic ones, according to the above calculations) and localize the seafloor epicenter of an expected seaquake. These stations will be equipped, in particular, with: magnetometers, the lines for the electric field measurements, and magneto-telluric blocks to discover dynamics of physical parameters beneath a sea floor as signs of a seaquake and/or tsunami preparation process. The buoy and balloon complexes of the LOAMS will record the meteorological and oceanographic parameters' variations including changes of reflection from a sea surface (tsunami ‘shadows’) caused by a tsunami wave propagation. Cables of the balloon and moored buoy will be used as receiving antennas and for multidisciplinary measurements including gradients of the fields (we show the cases are possible when the first seismic EM signal will be registered by an antenna above a sea). Also, the project includes radio-tomography with satellite instrumentation and sounding of the ionosphere from the buoy, balloon and satellite complexes. The balloon and buoy complexes will transmit data to a shore station over satellite link. The frequency ranges and sensitivity thresholds of all of the sensors of the LOAMS will be adapted to the characteristics of expected seismic signals according to the numerical research above. Computational methods and statistical analysis (e.g. seismic changes of coherence of spatially distributed sensors of different nature) of the recorded multidimensional time series will be used for prognostic interpretation. The multilevel recordings will provide a stable noise (e.g. ionosphere Pc pulsations, hard sea, industry) and seismic event detection. An intensive heat flow typical for tectonically active lithosphere zones may be considered as an energy source for advanced modifications of the LOAMS. The latter may be used as a warning system for continental and marine technologies, e.g. a sea bottom geothermal energy production. Indeed, seismic distraction of the nuclear power station Fukushima I demonstrates that similar technology hardly is able to solve the energy problems in seismically active regions. On the other hand, the LOAMS may be considered as a scientific observatory for development of the seaquake/tsunami precursor physics, i.e. seismo-hydro-electromagnetics.

Seasonal Ice Zone Reconnaissance Surveys Coordination

DTIC Science & Technology

2014-09-30

profiler (AXCP) ocean velocity shear (Morison), UpTempO buoy measurements of sea surface temperature (SST), sea level atmospheric pressure ( SLP ), and...and prediction…. Steele UpTempO buoy drops for SLP , SST, SSS, & surface velocity Visible and Thermal Images of the SIZ from the Coast Guard...Expendable CTD, AXCP= Air Expendable Current Profiler, SLP = Sea Level atmospheric Pressure, SST= Seas Surface Temperature, A/C= aircraft, SIC=Sea Ice

Simulation of a class of hazardous situations in the ICS «INM RAS - Baltic Sea»

NASA Astrophysics Data System (ADS)

Zakharova, Natalia; Agoshkov, Valery; Aseev, Nikita; Parmuzin, Eugene; Sheloput, Tateana; Shutyaev, Victor

2017-04-01

Development of Informational Computational Systems (ICS) for data assimilation procedures is one of multidisciplinary problems. To study and solve these problems one needs to apply modern results from different disciplines and recent developments in mathematical modeling, theory of adjoint equations and optimal control, inverse problems, numerical methods theory, numerical algebra, scientific computing and processing of satellite data. In this work the results on the ICS development for PC-ICS "INM RAS - Baltic Sea" are presented. We discuss practical problems studied by ICS. The System includes numerical model of the Baltic Sea thermodynamics, the new oil spill model describing the propagation of a slick at the Sea surface (Agoshkov, Aseev et al., 2014) and the optimal ship route calculating block (Agoshkov, Zayachkovsky et al., 2014). The ICS is based on the INMOM numerical model of the Baltic Sea thermodynamics (Zalesny et al., 2013). It is possible to calculate main hydrodynamic parameters (temperature, salinity, velocities, sea level) using user-friendly interface of the ICS. The System includes data assimilation procedures (Agoshkov, 2003, Parmuzin, Agoshkov, 2012) and one can use the block of variational assimilation of the sea surface temperature in order to obtain main hydrodynamic parameters. Main possibilities of the ICS and several numerical experiments are presented in the work. By the problem of risk control is meant a problem of determination of optimal resources quantity which are necessary for decreasing the risk to some acceptable value. Mass of oil slick is chosen as a function of control. For the realization of the random variable the quadratic "functional of cost" is introduced. It comprises cleaning costs and deviation of damage of oil pollution from its acceptable value. The problem of minimization of this functional is solved based on the methods of optimal control and the theory of adjoint equations. The solution of this problem is explicitly found. The study was supported by the Russian Foundation for Basic Research (project 16-31-00510) and by the Russian Science Foundation (project №14-11-00609). V. I. Agoshkov, Methods of Optimal Control and Adjoint Equations in Problems of Mathematical Physics. INM RAS, Moscow, 2003 (in Russian). V. B. Zalesny, A. V. Gusev, V. O. Ivchenko, R. Tamsalu, and R. Aps, Numerical model of the Baltic Sea circulation. Russ. J. Numer. Anal. Math. Modelling 28 (2013), No. 1, 85-100. V.I. Agoshkov, A.O. Zayachkovskiy, R. Aps, P. Kujala, and J. Rytkönen. Risk theory based solution to the problem of optimal vessel route // Russian Journal of Numerical Analysis and Mathematical Modelling. 2014. Volume 29, Issue 2, Pages 69-78. Agoshkov, V., Aseev, N., Aps, R., Kujala, P., Rytkönen, J., Zalesny, V. The problem of control of oil pollution risk in the Baltic Sea // Russian Journal of Numerical Analysis and Mathematical Modelling. 2014. Volume 29, Issue 2, Pages 93-105. E. I. Parmuzin and V. I. Agoshkov, Numerical solution of the variational assimilation problem for sea surface temperature in the model of the Black Sea dynamics. Russ. J. Numer. Anal. Math. Modelling 27 (2012), No. 1, 69-94. Olof Liungman and Johan Mattsson. Scientic Documentation of Seatrack Web; physical processes, algorithms and references, 2011.

Modeling sea-surface temperature and its variability

NASA Technical Reports Server (NTRS)

Sarachik, E. S.

1985-01-01

A brief review is presented of the temporal scales of sea surface temperature variability. Progress in modeling sea surface temperature, and remaining obstacles to the understanding of the variability is discussed.

Ocean Wave Studies with Applications to Ocean Modeling and Improvement of Satellite Altimeter Measurements

NASA Technical Reports Server (NTRS)

Glazman, Roman E.

1999-01-01

Combining analysis of satellite data (altimeter, scatterometer, high-resolution visible and infrared images, etc.) with mathematical modeling of non-linear wave processes, we investigate various ocean wave fields (on scales from capillary to planetary), their role in ocean dynamics and turbulent transport (of heat and biogeochemical quantities), and their effects on satellite altimeter measuring accuracy. In 1998 my attention was focused on long internal gravity waves (10 to 1000 km), known also as baroclinic inertia-gravity (BIG) waves. We found these waves to be a major factor of altimeter measurements "noise," resulting in a greater uncertainty [up to 10 cm in terms of sea surface height (SSH) amplitude] in the measured SSH signal than that caused by the sea state bias variations (up to 5 cm or so). This effect still remains largely overlooked by the satellite altimeter community. Our studies of BIG waves address not only their influence on altimeter measurements but also their role in global ocean dynamics and in transport and turbulent diffusion of biogeochemical quantities. In particular, in collaboration with Prof Peter Weichman, Caltech, we developed a theory of turbulent diffusion caused by wave motions of most general nature. Applied to the problem of horizontal turbulent diffusion in the ocean, the theory yielded the effective diffusion coefficient as a function of BIG wave parameters obtainable from satellite altimeter data. This effort, begun in 1997, has been successfully completed in 1998. We also developed a theory that relates spatial fluctuations of scalar fields (such as sea surface temperature, chlorophyll concentration, drifting ice concentration, etc.) to statistical characteristics of BIG waves obtainable from altimeter measurements. A manuscript is in the final stages of preparation. In order to verify the theoretical predictions and apply them to observations, we are now analyzing Sea-viewing Wide Field of view Sensor (SeaWiFS) and Field of view Sensor (SeaWiFS) and Advanced Very High-Resolution Radiometer (AVHRR) data on sea surface temperature (SST) and chlorophyll concentration jointly with TOPEX/POSEIDON data on SSH variations.

Post-glacial sea-level history for NE Ireland (Belfast Lough) based on offshore evidence

NASA Astrophysics Data System (ADS)

Quinn, R.; Plets, R. M.; Callard, L.; Cooper, A.; Long, A. J.; Belknap, D. F.; Edwards, R.; Jackson, D.; Kelley, J. T.; Long, D.; Milne, G. A.; Monteys, X.

2013-12-01

Glacio-isostatic adjustment (GIA) models suggest a complex relative sea-level (RSL) pattern around the Irish Sea Basin after the Last Glacial Maximum (LGM), with modelled sea-level lowstands ranging from -12 m in the north to greater than -60 m in the south of the Basin. However, these GIA models are poorly constrained by observational data offshore. Belfast Lough, on the NE coast of Ireland, is one of seven sites chosen to investigate this complex RSL history as part of the project ';Late Glacial Sea level minima in the Western British Isles' (NERC NE/H024301/1). Belfast Lough was chosen as one of the candidate sites on the basis of location (at the northern end of the Irish Sea Basin), sedimentary environment (grossly depositional) and the fact that the lowstand predicted for the Belfast Lough area by a recent version of the GIA model (-16.5 m) differs significantly from the (limited) extant observational data, which interprets the lowstand at -30 m. In 2011 and 2012 we gathered new multi-beam echo-sounder data, >200 km trackline pinger- and boomer- seismic reflection data and 46 vibrocores in Belfast Lough. Radiocarbon dating and palaeoenvironmental analysis are used to constrain the interpretation of the seismic and sediment data. Five seismo-stratigraphic units are interpreted, with a distinct erosional surface between U3 and U4 interpreted as a transgressive surface associated with sea level rise post-dating a RSL lowstand. Foraminiferal evidence indicates an increase in marine species (from lagoonal/estuarine to fully marine) from U4 to U5. Integration of the seismic and core data indicate an erosional event prior to 12.7 cal yr BP resulting in a planated surface in the inner Lough and wave-eroded drumlins at the mouth of the Lough between -15 and -22 m, interpreted as a possible slowstand. On the basis of seismic evidence in the outer Lough, an as yet undated lowstand at -42 m is tentatively interpreted to pre-date this stillstand. These results will be used to tune the Earth and ice model parameters in a new run of the GIA model.

Post-glacial sea-level history for NE Ireland (Belfast Lough) based on offshore evidence

NASA Astrophysics Data System (ADS)

Quinn, Rory; Plets, Ruth; Callard, Louise; Cooper, Andrew; Antony, Long; Daniel, Belknap; Robin, Edwards; Derek, Jackson; Joseph, Kelley; David, Long; Glenn, Milne; Xavier, Monteys

2014-05-01

Glacio-isostatic adjustment (GIA) models suggest a complex relative sea-level (RSL) pattern around the Irish Sea Basin after the Last Glacial Maximum (LGM), with modelled sea-level lowstands ranging from -12 m in the north to greater than -60 m in the south of the Basin. However, these GIA models are poorly constrained by observational data offshore. Belfast Lough, on the NE coast of Ireland, is one of seven sites chosen to investigate this complex RSL history as part of the project 'Late Glacial Sea level minima in the Western British Isles' (NERC NE/H024301/1). Belfast Lough was chosen as one of the candidate sites on the basis of location (at the northern end of the Irish Sea Basin), sedimentary environment (grossly depositional) and the fact that the lowstand predicted for the Belfast Lough area by a recent version of the GIA model (-16.5 m) differs significantly from the (limited) extant observational data, which interprets the lowstand at -30 m. In 2011 and 2012 we gathered new multi-beam echo-sounder data, >200 km trackline pinger- and boomer- seismic reflection data and 46 vibrocores in Belfast Lough. Radiocarbon dating and palaeoenvironmental analysis are used to constrain the interpretation of the seismic and sediment data. Five seismo-stratigraphic units are interpreted, with a distinct erosional surface between U3 and U4 interpreted as a transgressive surface associated with sea level rise post-dating a RSL lowstand. Foraminiferal evidence indicates an increase in marine species (from lagoonal/estuarine to fully marine) from U4 to U5. Integration of the seismic and core data indicate an erosional event prior to 12.7 cal yr BP resulting in a planated surface in the inner Lough and wave-eroded drumlins at the mouth of the Lough between -15 and -22 m, interpreted as a possible slowstand. On the basis of seismic evidence in the outer Lough, an as yet undated lowstand at -42 m is tentatively interpreted to pre-date this stillstand. These results will be used to tune the Earth and ice model parameters in a new run of the GIA model.

Influence of El Niño–Southern Oscillation (ENSO) events on the evolution of central California's shoreline

USGS Publications Warehouse

Storlazzi, Curt D.; Griggs, Gary B.

2000-01-01

Significant sea-cliff erosion and storm damage occurred along the central coast of California during the 1982–1983 and 1997–1998 El Niño winters. This generated interest among scientists and land-use planners in how historic El Niño–Southern Oscillation (ENSO) winters have affected the coastal climate of central California. A relative ENSO intensity index based on oceanographic and meteorologic data defines the timing and magnitude of ENSO events over the past century. The index suggests that five higher intensity (relative values 4–6) and 17 lower intensity (relative values 1–3) ENSO events took place between 1910 and 1995. The ENSO intensity index correlates with fluctuations in the time series of cyclone activity, precipitation, detrended sea level, wave height, sea-surface temperature, and sea-level barometric pressure. Wave height, sea level, and precipitation, which are the primary external forcing parameters in sea-cliff erosion, increase nonlinearly with increasing relative ENSO event intensity. The number of storms that caused coastal erosion or storm damage and the historic occurrence of large-scale sea-cliff erosion along the central coast also increase nonlinearly with increasing relative event intensity. These correlations and the frequency distribution of relative ENSO event intensities indicate that moderate- to high-intensity ENSO events cause the most sea-cliff erosion and shoreline recession over the course of a century.

Uncertainty quantification and global sensitivity analysis of the Los Alamos sea ice model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urrego-Blanco, Jorge Rolando; Urban, Nathan Mark; Hunke, Elizabeth Clare

Changes in the high-latitude climate system have the potential to affect global climate through feedbacks with the atmosphere and connections with midlatitudes. Sea ice and climate models used to understand these changes have uncertainties that need to be characterized and quantified. We present a quantitative way to assess uncertainty in complex computer models, which is a new approach in the analysis of sea ice models. We characterize parametric uncertainty in the Los Alamos sea ice model (CICE) in a standalone configuration and quantify the sensitivity of sea ice area, extent, and volume with respect to uncertainty in 39 individual modelmore » parameters. Unlike common sensitivity analyses conducted in previous studies where parameters are varied one at a time, this study uses a global variance-based approach in which Sobol' sequences are used to efficiently sample the full 39-dimensional parameter space. We implement a fast emulator of the sea ice model whose predictions of sea ice extent, area, and volume are used to compute the Sobol' sensitivity indices of the 39 parameters. Main effects and interactions among the most influential parameters are also estimated by a nonparametric regression technique based on generalized additive models. A ranking based on the sensitivity indices indicates that model predictions are most sensitive to snow parameters such as snow conductivity and grain size, and the drainage of melt ponds. Lastly, it is recommended that research be prioritized toward more accurately determining these most influential parameter values by observational studies or by improving parameterizations in the sea ice model.« less

Uncertainty quantification and global sensitivity analysis of the Los Alamos sea ice model

DOE PAGES

Urrego-Blanco, Jorge Rolando; Urban, Nathan Mark; Hunke, Elizabeth Clare; ...

2016-04-01

Changes in the high-latitude climate system have the potential to affect global climate through feedbacks with the atmosphere and connections with midlatitudes. Sea ice and climate models used to understand these changes have uncertainties that need to be characterized and quantified. We present a quantitative way to assess uncertainty in complex computer models, which is a new approach in the analysis of sea ice models. We characterize parametric uncertainty in the Los Alamos sea ice model (CICE) in a standalone configuration and quantify the sensitivity of sea ice area, extent, and volume with respect to uncertainty in 39 individual modelmore » parameters. Unlike common sensitivity analyses conducted in previous studies where parameters are varied one at a time, this study uses a global variance-based approach in which Sobol' sequences are used to efficiently sample the full 39-dimensional parameter space. We implement a fast emulator of the sea ice model whose predictions of sea ice extent, area, and volume are used to compute the Sobol' sensitivity indices of the 39 parameters. Main effects and interactions among the most influential parameters are also estimated by a nonparametric regression technique based on generalized additive models. A ranking based on the sensitivity indices indicates that model predictions are most sensitive to snow parameters such as snow conductivity and grain size, and the drainage of melt ponds. Lastly, it is recommended that research be prioritized toward more accurately determining these most influential parameter values by observational studies or by improving parameterizations in the sea ice model.« less

Uncertainty quantification and global sensitivity analysis of the Los Alamos sea ice model

NASA Astrophysics Data System (ADS)

Urrego-Blanco, Jorge R.; Urban, Nathan M.; Hunke, Elizabeth C.; Turner, Adrian K.; Jeffery, Nicole

2016-04-01

Changes in the high-latitude climate system have the potential to affect global climate through feedbacks with the atmosphere and connections with midlatitudes. Sea ice and climate models used to understand these changes have uncertainties that need to be characterized and quantified. We present a quantitative way to assess uncertainty in complex computer models, which is a new approach in the analysis of sea ice models. We characterize parametric uncertainty in the Los Alamos sea ice model (CICE) in a standalone configuration and quantify the sensitivity of sea ice area, extent, and volume with respect to uncertainty in 39 individual model parameters. Unlike common sensitivity analyses conducted in previous studies where parameters are varied one at a time, this study uses a global variance-based approach in which Sobol' sequences are used to efficiently sample the full 39-dimensional parameter space. We implement a fast emulator of the sea ice model whose predictions of sea ice extent, area, and volume are used to compute the Sobol' sensitivity indices of the 39 parameters. Main effects and interactions among the most influential parameters are also estimated by a nonparametric regression technique based on generalized additive models. A ranking based on the sensitivity indices indicates that model predictions are most sensitive to snow parameters such as snow conductivity and grain size, and the drainage of melt ponds. It is recommended that research be prioritized toward more accurately determining these most influential parameter values by observational studies or by improving parameterizations in the sea ice model.

Black sea surface temperature anomaly on 5th August 1998 and the ozone layer thickness

NASA Astrophysics Data System (ADS)

Manev, A.; Palazov, K.; Raykov, St.; Ivanov, V.

2003-04-01

BLACK SEA SURFACE TEMPERATURE ANOMALY ON 5th AUGUST 1998 AND THE OZONE LAYER THICKNESS A. Manev , K. Palazov , St. Raykov, V. Ivanov Solar Terrestrial Influences Laboratory, Bulgarian Academy of Sciences amanev@abv.bg This paper focuses on the peculiarities of the Black Sea surface temperature anomaly on 05.08.1998. Researching the daily temperature changes in a number of control fields in the course of 8-10 years, we have found hidden correlations and anomalous deviations in the sea surface temperatures on a global scale. Research proves the statistical reliability of the temperature anomaly on the entire Black Sea surface registered on 04.-05.08.1998. In the course of six days around these dates the temperatures are up to 2°C higher than the maximum temperatures in this period in the other seven years. A more detailed analysis of the dynamics of the anomaly required the investigation of five Black Sea surface characteristic zones of 75x75 km. The analysis covers the period 20 days - 10 days before and 10 days after the anomaly. Investigations aimed at interpreting the reasons for the anomalous heating of the surface waters. We have tried to analyze the correlation between sea surface temperature and the global ozone above the Black Sea by using simultaneously data from the two satellite systems NOAA and TOMS. Methods of processing and comparing the data from the two satellite systems are described. The correlation coefficients values for the five characteristic zones are very high and close, which proves that the character of the correlation ozone - sea surface temperature is the same for the entire Black Sea surface. Despite the high correlation coefficient, we have proved that causality between the two phenomena at the time of the anomaly does not exit.

Analyses of Sea Surface Height, Bottom Pressure and Acoustic Travel Time in the Japan/East Sea

DTIC Science & Technology

2006-01-01

ANALYSES OF SEA SURFACE HEIGHT, BOTTOM PRESSURE AND ACOUSTIC TRAVEL TIME IN THE JAPAN/EAST SEA BY YONGSHENG XU A DISSERTATION SUBMITTED IN PARTIAL...COVERED 00-00-2006 to 00-00-2006 4. TITLE AND SUBTITLE Analyses of Sea Surface Height, Bottom Pressure and Acoustic Travel Time in the Japan/East Sea...1999 to July 2001. The PIESs recorded hourly vertical acoustic travel time and pressure, which are respectively good proxies of baroclinic and

A survey of the summer coccolithophore community in the western Barents Sea

NASA Astrophysics Data System (ADS)

Giraudeau, Jacques; Hulot, Vivien; Hanquiez, Vincent; Devaux, Ludovic; Howa, Hélène; Garlan, Thierry

2016-06-01

The Barents Sea is particularly vulnerable to large-scale hydro-climatic changes associated with the polar amplification of climate change. Key oceanographical variables in this region are the seasonal development of sea-ice and the location and strength of physico-chemical gradients in the surface and subsurface water layers induced by the convergence of Arctic- and Atlantic-derived water masses. Remote sensing imagery have highlighted the increasing success of calcifying haptophytes (coccolithophores) in the summer phytoplankton production of the Barents Sea over the last 20 years, as a response to an overall larger contribution of Atlantic waters to surface and sub-surface waters, as well as to enhanced sea-ice melt-induced summer stratification of the photic layer. The present study provides a first thorough description of coccolithophore standing stocks and diversity over the shelf and slope of the western Barents Sea from two sets of surface and water column samples collected during August-September 2014 from northern Norway to southern Svalbard. The abundance and composition of coccolithophore cells and skeletal remains (coccoliths) are discussed in view of the physical-chemical-biological status of the surface waters and water column based on in-situ (temperature, salinity, fluorescence) and shore-based (microscope enumerations, chemotaxonomy) measurements, as well as satellite-derived data (Chl a and particulate inorganic carbon contents). The coccolithophore population is characterized by a low species diversity and the overwhelming dominance of Emiliania huxleyi. Coccolithophores are abundant both within the well stratified, Norwegian coastal water - influenced shallow mixed layer off northern Norway, as well as within well-mixed cool Atlantic water in close vicinity of the Polar Front. Bloom concentrations with standing stocks larger than 4 million cells/l are recorded in the latter area north of 75°N. Our limited set of chemotaxonomic data suggests that coccolithophores contribute substantially (ca. 20% of the total Chl a) to the summer phytoplankton community which is made essentially of small-sized algal groups. Excluding the bloom area, coccolith calcite accounts for an average of 20% to the bulk particulate inorganic carbon content in the surface waters, and explains to some extent the satellite-derived spatial distribution of this parameter. Deep water living coccolithophore species thriving below the pycnocline as well as populations present in well-mixed cool Atlantic water are rapidly transferred to depth in the form of intact coccospheres down to at least 200 m. High amplitude internal waves which, according to our observations, affect a wide range of water depth up to the lower photic zone, might strengthen the vertical transfer of this sinking population.

Bag-breakup control of surface drag in hurricanes

NASA Astrophysics Data System (ADS)

Troitskaya, Yuliya; Zilitinkevich, Sergej; Kandaurov, Alexander; Ermakova, Olga; Kozlov, Dmitry; Sergeev, Daniil

2016-04-01

Air-sea interaction at extreme winds is of special interest now in connection with the problem of the sea surface drag reduction at the wind speed exceeding 30-35 m/s. This phenomenon predicted by Emanuel (1995) and confirmed by a number of field (e.g., Powell, et al, 2003) and laboratory (Donelan et al, 2004) experiments still waits its physical explanation. Several papers attributed the drag reduction to spume droplets - spray turning off the crests of breaking waves (e.g., Kudryavtsev, Makin, 2011, Bao, et al, 2011). The fluxes associated with the spray are determined by the rate of droplet production at the surface quantified by the sea spray generation function (SSGF), defined as the number of spray particles of radius r produced from the unit area of water surface in unit time. However, the mechanism of spume droplets' formation is unknown and empirical estimates of SSGF varied over six orders of magnitude; therefore, the production rate of large sea spray droplets is not adequately described and there are significant uncertainties in estimations of exchange processes in hurricanes. Herewith, it is unknown what is air-sea interface and how water is fragmented to spray at hurricane wind. Using high-speed video, we observed mechanisms of production of spume droplets at strong winds by high-speed video filming, investigated statistics and compared their efficiency. Experiments showed, that the generation of the spume droplets near the wave crest is caused by the following events: bursting of submerged bubbles, generation and breakup of "projections" and "bag breakup". Statistical analysis of results of these experiments showed that the main mechanism of spray-generation is attributed to "bag-breakup mechanism", namely, inflating and consequent blowing of short-lived, sail-like pieces of the water-surface film. Using high-speed video, we show that at hurricane winds the main mechanism of spray production is attributed to "bag-breakup", namely, inflating and consequent breaking of short-lived, sail-like pieces of the water-surface film - "bags". On the base of general principles of statistical physics (model of a canonical ensemble) we developed statistics of the "bag-breakup" events: their number and statistical distribution of geometrical parameters depending on wind speed. Basing on the developed statistics, we estimated the surface stress caused by bags as the average sum of stresses caused by individual bags depending on their eometrical parameters. The resulting stress is subjected to counteracting impacts of the increasing wind speed: the increasing number of bags, and their decreasing sizes and life times and the balance yields a peaking dependence of the bag resistance on the wind speed: the share of bag-stress peaks at U10  35 m/s and then reduces. Peaking of surface stress associated with the "bag-breakup" explains seemingly paradoxical non-monotonous wind-dependence of surface drag coefficient peaking at winds about 35 m/s. This work was supported by the Russian Foundation of Basic Research (14-05-91767, 13-05-12093, 16-05-00839, 14-05-91767, 16-55-52025, 15-35-20953) and experiment and equipment was supported by Russian Science Foundation (Agreements 14-17-00667 and 15-17-20009 respectively), Yu.Troitskaya, A.Kandaurov and D.Sergeev were partially supported by FP7 Collaborative Project No. 612610.

[Design and experimentation of marine optical buoy].

PubMed

Yang, Yue-Zhong; Sun, Zhao-Hua; Cao, Wen-Xi; Li, Cai; Zhao, Jun; Zhou, Wen; Lu, Gui-Xin; Ke, Tian-Cun; Guo, Chao-Ying

2009-02-01

Marine optical buoy is of important value in terms of calibration and validation of ocean color remote sensing, scientific observation, coastal environment monitoring, etc. A marine optical buoy system was designed which consists of a main and a slave buoy. The system can measure the distribution of irradiance and radiance over the sea surface, in the layer near sea surface and in the euphotic zone synchronously, during which some other parameters are also acquired such as spectral absorption and scattering coefficients of the water column, the velocity and direction of the wind, and so on. The buoy was positioned by GPS. The low-power integrated PC104 computer was used as the control core to collect data automatically. The data and commands were real-timely transmitted by CDMA/GPRS wireless networks or by the maritime satellite. The coastal marine experimentation demonstrated that the buoy has small pitch and roll rates in high sea state conditions and thus can meet the needs of underwater radiometric measurements, the data collection and remote transmission are reliable, and the auto-operated anti-biofouling devices can ensure that the optical sensors work effectively for a period of several months.

Interaction of marine geodesy, satellite technology and ocean physics

NASA Technical Reports Server (NTRS)

Mourad, A. G.; Fubara, D. M. J.

1972-01-01

The possible applications of satellite technology in marine geodesy and geodetic related ocean physics were investigated. Four major problems were identified in the areas of geodesy and ocean physics: (1) geodetic positioning and control establishment; (2) sea surface topography and geoid determination; (3) geodetic applications to ocean physics; and (4) ground truth establishment. It was found that satellite technology can play a major role in their solution. For solution of the first problem, the use of satellite geodetic techniques, such as Doppler and C-band radar ranging, is demonstrated to fix the three-dimensional coordinates of marine geodetic control if multi-satellite passes are used. The second problem is shown to require the use of satellite altimetry, along with accurate knowledge of ocean-dynamics parameters such as sea state, ocean tides, and mean sea level. The use of both conventional and advanced satellite techniques appeared to be necessary to solve the third and fourth problems.

Sun glitter imaging of submarine sand waves on the Taiwan Banks: Determination of the relaxation rate of short waves

NASA Astrophysics Data System (ADS)

Shao, Hao; Li, Yan; Li, Li

2011-06-01

Above sand waves on the seafloor, surface short waves, which are responsible for the radiance distribution in remote sensing imagery, are modulated gradually by the submarine topography. The relaxation rate μr characterizes the rate at which the short waves reach their saturation range after being disturbed. It is a key parameter in the weak hydrodynamic interaction theory and is also a most important parameter in the imaging mechanism used for mapping submarine bottom topography. In this study, a robust expression containing intensity and phase (advection effect) modulations of the perturbed action spectrum of short waves was deduced, by using the first-order weak hydrodynamic interaction theory. On the basis of the phase modulation, a method was developed to determine the relaxation rate in the Sun glitter imaging mechanism. The relaxation rates were estimated using in situ data measured on a cruise over the sand waves of the Taiwan Banks, a sea area between the East China Sea and the South China Sea, on 28-29 August 2006. Results showed that, under a wind speed of 5.0 m s-1, the relaxation rate of short waves was about 0.055 s-1 in response to current variations and about 0.025 s-1 equivalently in response to sea bottom topographic variations. The former value could be applied to interpret the amplitude of submarine topography by using satellite imagery, while the latter one (equivalent relaxation rate μ'r) could help to more accurately calibrate the spatial position of the retrieved sea bottom topography.

Large-eddy simulation of subtropical cloud-topped boundary layers: 1. A forcing framework with closed surface energy balance

NASA Astrophysics Data System (ADS)

Tan, Zhihong; Schneider, Tapio; Teixeira, João.; Pressel, Kyle G.

2016-12-01

Large-eddy simulation (LES) of clouds has the potential to resolve a central question in climate dynamics, namely, how subtropical marine boundary layer (MBL) clouds respond to global warming. However, large-scale processes need to be prescribed or represented parameterically in the limited-area LES domains. It is important that the representation of large-scale processes satisfies constraints such as a closed energy balance in a manner that is realizable under climate change. For example, LES with fixed sea surface temperatures usually do not close the surface energy balance, potentially leading to spurious surface fluxes and cloud responses to climate change. Here a framework of forcing LES of subtropical MBL clouds is presented that enforces a closed surface energy balance by coupling atmospheric LES to an ocean mixed layer with a sea surface temperature (SST) that depends on radiative fluxes and sensible and latent heat fluxes at the surface. A variety of subtropical MBL cloud regimes (stratocumulus, cumulus, and stratocumulus over cumulus) are simulated successfully within this framework. However, unlike in conventional frameworks with fixed SST, feedbacks between cloud cover and SST arise, which can lead to sudden transitions between cloud regimes (e.g., stratocumulus to cumulus) as forcing parameters are varied. The simulations validate this framework for studies of MBL clouds and establish its usefulness for studies of how the clouds respond to climate change.

Development of a Tsunami Scenario Database for Marmara Sea

NASA Astrophysics Data System (ADS)

Ozer Sozdinler, Ceren; Necmioglu, Ocal; Meral Ozel, Nurcan

2016-04-01

Due to the very short travel times in Marmara Sea, a Tsunami Early Warning System (TEWS) has to be strongly coupled with the earthquake early warning system and should be supported with a pre-computed tsunami scenario database to be queried in near real-time based on the initial earthquake parameters. To address this problem, 30 different composite earthquake scenarios with maximum credible Mw values based on 32 fault segments have been identified to produce a detailed scenario database for all possible earthquakes in the Marmara Sea with a tsunamigenic potential. The bathy/topo data of Marmara Sea was prepared using GEBCO and ASTER data, bathymetric measurements along Bosphorus, Istanbul and Dardanelle, Canakkale and the coastline digitized from satellite images. The coarser domain in 90m-grid size was divided into 11 sub-regions having 30m-grid size in order to increase the data resolution and precision of the calculation results. The analyses were performed in nested domains with numerical model NAMIDANCE using non-linear shallow water equations. In order to cover all the residential areas, industrial facilities and touristic locations, more than 1000 numerical gauge points were selected along the coasts of Marmara Sea, which are located at water depth of 5 to 10m in finer domain. The distributions of tsunami hydrodynamic parameters were investigated together with the change of water surface elevations, current velocities, momentum fluxes and other important parameters at the gauge points. This work is funded by the project MARsite - New Directions in Seismic Hazard assessment through Focused Earth Observation in the Marmara Supersite (FP7-ENV.2012 6.4-2, Grant 308417 - see NH2.3/GMPV7.4/SM7.7) and supported by SATREPS-MarDim Project (Earthquake and Tsunami Disaster Mitigation in the Marmara Region and Disaster Education in Turkey) and JICA (Japan International Cooperation Agency). The authors would like to acknowledge Ms. Basak Firat for her assistance in preparation of the database.

Hydrological state of the Large Aral Sea in the fall season of 2013

NASA Astrophysics Data System (ADS)

Izhitskiy, Alexander; Zavialov, Peter

2014-05-01

We report here the results of the latest expedition of the Shirshov Institute to the Aral Sea. The survey encompassed 8 field days in October-November, 2013. Direct measurements of thermohaline characteristics and water currents were conducted in the western basin of the Large Aral Sea during the expedition. Vertical profiles of temperature and salinity were obtained using a CTD profiler at 9 stations, situated on two cross-sections of the western basin. Four mooring stations equipped with current meters, as well as pressure gauges, were deployed for 4-6 days on the slopes of the deepest portion of the western basin. A portable automatic meteorological station, continuously recording the variability of wind and principal meteorological parameters, was installed near the mooring sites. Analysis of the current measurements data along with the meteorological data records demonstrated the current velocity and level anomalies responded energetically to winds. Correlation analysis of the velocity series versus the wind stress allowed to quantify the response of the system to the wind forcing. Together with the similar results of more earlier surveys, recently collected data shows that the mean surface circulation of the western basin remains anti-cyclonic under the predominant winds. Character of the interannual variability of salinity values in the Aral Sea water manifested increase in the surface layer during last 5 years. On the other hand, salinity values in the bottom layer appear to be decreased due to ceasing of the influence of the interbasin water exchange since 2010. Water level of the Large Aral Sea is still falling. Assessment of the on-going changes holds promise to help predicting the subsequent state of the Aral Sea region.

Biofilm-like properties of the sea surface and predicted effects on air-sea CO2 exchange

NASA Astrophysics Data System (ADS)

Wurl, Oliver; Stolle, Christian; Van Thuoc, Chu; The Thu, Pham; Mari, Xavier

2016-05-01

Because the sea surface controls various interactions between the ocean and the atmosphere, it has a profound function for marine biogeochemistry and climate regulation. The sea surface is the gateway for the exchange of climate-relevant gases, heat and particles. Thus, in order to determine how the ocean and the atmosphere interact and respond to environmental changes on a global scale, the characterization and understanding of the sea surface are essential. The uppermost part of the water column is defined as the sea-surface microlayer and experiences strong spatial and temporal dynamics, mainly due to meteorological forcing. Wave-damped areas at the sea surface are caused by the accumulation of surface-active organic material and are defined as slicks. Natural slicks are observed frequently but their biogeochemical properties are poorly understood. In the present study, we found up to 40 times more transparent exopolymer particles (TEP), the foundation of any biofilm, in slicks compared to the underlying bulk water at multiple stations in the North Pacific, South China Sea, and Baltic Sea. We found a significant lower enrichment of TEP (up to 6) in non-slick sea surfaces compared to its underlying bulk water. Moreover, slicks were characterized by a large microbial biomass, another shared feature with conventional biofilms on solid surfaces. Compared to non-slick samples (avg. pairwise similarity of 70%), the community composition of bacteria in slicks was increasingly (avg. pairwise similarity of 45%) different from bulk water communities, indicating that the TEP-matrix creates specific environments for its inhabitants. We, therefore, conclude that slicks can feature biofilm-like properties with the excessive accumulation of particles and microbes. We also assessed the potential distribution and frequency of slick-formation in coastal and oceanic regions, and their effect on air-sea CO2 exchange based on literature data. We estimate that slicks can reduce CO2 fluxes by up to 15%, and, therefore, play important local and regional roles in regulating air-sea interactions.

Sea level and turbidity controls on mangrove soil surface elevation change

USGS Publications Warehouse

Lovelock, Catherine E.; Fernanda Adame, Maria; Bennion, Vicki; Hayes, Matthew; Reef, Ruth; Santini, Nadia; Cahoon, Donald R.

2015-01-01

Increases in sea level are a threat to seaward fringing mangrove forests if levels of inundation exceed the physiological tolerance of the trees; however, tidal wetlands can keep pace with sea level rise if soil surface elevations can increase at the same pace as sea level rise. Sediment accretion on the soil surface and belowground production of roots are proposed to increase with increasing sea level, enabling intertidal habitats to maintain their position relative to mean sea level, but there are few tests of these predictions in mangrove forests. Here we used variation in sea level and the availability of sediments caused by seasonal and inter-annual variation in the intensity of La Nina-El Nino to assess the effects of increasing sea level on surface elevation gains and contributing processes (accretion on the surface, subsidence and root growth) in mangrove forests. We found that soil surface elevation increased with mean sea level (which varied over 250 mm during the study) and with turbidity at sites where fine sediment in the water column is abundant. In contrast, where sediments were sandy, rates of surface elevation gain were high, but not significantly related to variation in turbidity, and were likely to be influenced by other factors that deliver sand to the mangrove forest. Root growth was not linked to soil surface elevation gains, although it was associated with reduced shallow subsidence, and therefore may contribute to the capacity of mangroves to keep pace with sea level rise. Our results indicate both surface (sedimentation) and subsurface (root growth) processes can influence mangrove capacity to keep pace with sea level rise within the same geographic location, and that current models of tidal marsh responses to sea level rise capture the major feature of the response of mangroves where fine, but not coarse, sediments are abundant.

Nimbus 7 SMMR Derived Seasonal Variations in the Water Vapor, Liquid Water and Surface Winds over the Global Oceans

NASA Technical Reports Server (NTRS)

Prabhakara, C.; Short, D. A.

1984-01-01

Monthly mean distributions of water vapor and liquid water contained in a vertical column of the atmosphere and the surface wind speed were derived from Nimbus Scanning Multichannel Microwave Radiometer (SMMR) observations over the global oceans for the period November 1978 to November 1979. The remote sensing techniques used to estimate these parameters from SMMR are presented to reveal the limitations, accuracies, and applicability of the satellite-derived information for climate studies. On a time scale of the order of a month, the distribution of atmospheric water vapor over the oceans is controlled by the sea surface temperature and the large scale atmospheric circulation. The monthly mean distribution of liquid water content in the atmosphere over the oceans closely reflects the precipitation patterns associated with the convectively and baroclinically active regions. Together with the remotely sensed surface wind speed that is causing the sea surface stress, the data collected reveal the manner in which the ocean-atmosphere system is operating. Prominent differences in the water vapor patterns from one year to the next, or from month to month, are associated with anomalies in the wind and geopotential height fields. In association with such circulation anomalies the precipitation patterns deduced from the meteorological network over adjacent continents also reveal anomalous distributions.

Red Sea circulation during marine isotope stage 5e

NASA Astrophysics Data System (ADS)

Siccha, Michael; Biton, Eli; Gildor, Hezi

2015-04-01

We have employed a regional Massachusetts Institute of Technology oceanic general circulation model of the Red Sea to investigate its circulation during marine isotope stage (MIS) 5e, the peak of the last interglacial, approximately 125 ka before present. Compared to present-day conditions, MIS 5e was characterized by higher Northern Hemisphere summer insolation, accompanied by increases in air temperature of more than 2°C and global sea level approximately 8 m higher than today. As a consequence of the increased seasonality, intensified monsoonal conditions with increased winds, rainfall, and humidity in the Red Sea region are evident in speleothem records and supported by model simulations. To assess the dominant factors responsible for the observed changes, we conducted several sensitivity experiments in which the MIS 5 boundary conditions or forcing parameters were used individually. Overall, our model simulation for the last interglacial maximum reconstructs a Red Sea that is colder, less ventilated and probably more oligotrophic than at present day. The largest alteration in Red Sea circulation and properties was found for the simulation of the northward displacement and intensification of the African tropical rain belt during MIS 5e, leading to a notable increase in the fresh water flux into the Red Sea. Such an increase significantly reduced the Red Sea salinity and exchange volume of the Red Sea with the Gulf of Aden. The Red Sea reacted to the MIS 5e insolation forcing by the expected increase in seasonal sea surface temperature amplitude and overall cooling caused by lower temperatures during deep water formation in winter.

Arc program documentation

NASA Technical Reports Server (NTRS)

Mcmillan, J. D.

1976-01-01

A description of the input and output files and the data control cards for the altimeter residual computation (ARC) computer program is given. The program acts as the final altimeter preprocessor before the data is reformatted for external users. It calculates all parameters necessary for the computation of the altimeter observation residuals and the sea surface height. Mathematical models used for calculating tropospheric refraction, geoid height, tide height, ephemeris, and orbit geometry are described.

GNSS, Satellite Altimetry and Formosat-3/COSMIC for Determination of Ionosphere Parameters

NASA Astrophysics Data System (ADS)

Mahdi Alizadeh Elizei, M.; Schuh, Harald; Schmidt, Michael; Todorova, Sonya

The dispersion of ionosphere with respect to the microwave signals allows gaining information about the parameters of this medium in terms of the electron density (Ne), or the Total Elec-tron Content (TEC). In the last decade space geodetic techniques, such as Global Navigation Satellite System (GNSS), satellite altimetry missions, and Low Earth Orbiting (LEO) satel-lites have turned into a promising tool for remote sensing the ionosphere. The dual-frequency GNSS observations provide the main input data for development of Global Ionosphere Maps (GIM). However, the GNSS stations are heterogeneously distributed, with large gaps particu-larly over the sea surface, which lowers the precision of the GIM over these areas. Conversely, dual-frequency satellite altimetry missions provide information about the ionosphere precisely above the sea surface. In addition, LEO satellites such as Formosat-3/COSMIC (F-3/C) pro-vide well-distributed information of ionosphere around the world. In this study we developed GIMs of VTEC from combination of GNSS, satellite altimetry and F-3/C data with temporal resolution of 2 hours and spatial resolution of 5 degree in longitude and 2.5 degree in latitude. The combined GIMs provide a more homogeneous global coverage and higher precision and reliability than results of each individual technique.

Direct and semi-direct aerosol radiative effect on the Mediterranean climate variability using a coupled regional climate system model

NASA Astrophysics Data System (ADS)

Nabat, Pierre; Somot, Samuel; Mallet, Marc; Sevault, Florence; Chiacchio, Marc; Wild, Martin

2015-02-01

A fully coupled regional climate system model (CNRM-RCSM4) has been used over the Mediterranean region to investigate the direct and semi-direct effects of aerosols, but also their role in the radiation-atmosphere-ocean interactions through multi-annual ensemble simulations (2003-2009) with and without aerosols and ocean-atmosphere coupling. Aerosols have been taken into account in CNRM-RCSM4 through realistic interannual monthly AOD climatologies. An evaluation of the model has been achieved, against various observations for meteorological parameters, and has shown the ability of CNRM-RCSM4 to reproduce the main patterns of the Mediterranean climate despite some biases in sea surface temperature (SST), radiation and cloud cover. The results concerning the aerosol radiative effects show a negative surface forcing on average because of the absorption and scattering of the incident radiation. The SW surface direct effect is on average -20.9 Wm-2 over the Mediterranean Sea, -14.7 Wm-2 over Europe and -19.7 Wm-2 over northern Africa. The LW surface direct effect is weaker as only dust aerosols contribute (+4.8 Wm-2 over northern Africa). This direct effect is partly counterbalanced by a positive semi-direct radiative effect over the Mediterranean Sea (+5.7 Wm-2 on average) and Europe (+5.0 Wm-2) due to changes in cloud cover and atmospheric circulation. The total aerosol effect is consequently negative at the surface and responsible for a decrease in land (on average -0.4 °C over Europe, and -0.5 °C over northern Africa) and sea surface temperature (on average -0.5 °C for the Mediterranean SST). In addition, the latent heat loss is shown to be weaker (-11.0 Wm-2) in the presence of aerosols, resulting in a decrease in specific humidity in the lower troposphere, and a reduction in cloud cover and precipitation. Simulations also indicate that dust aerosols warm the troposphere by absorbing solar radiation, and prevent radiation from reaching the surface, thus stabilizing the troposphere. The comparison with the model response in atmosphere-only simulations shows that these feedbacks are attenuated if SST cannot be modified by aerosols, highlighting the importance of using coupled regional models over the Mediterranean. Oceanic convection is also strengthened by aerosols, which tends to reinforce the Mediterranean thermohaline circulation. In parallel, two case studies are presented to illustrate positive feedbacks between dust aerosols and regional climate. First, the eastern Mediterranean was subject to high dust aerosol loads in June 2007 which reduce land and sea surface temperature, as well as air-sea humidity fluxes. Because of northern wind over the eastern Mediterranean, drier and cooler air has been consequently advected from the sea to the African continent, reinforcing the direct dust effect over land. On the contrary, during the western European heat wave in June 2006, dust aerosols have contributed to reinforcing an important ridge responsible for dry and warm air advection over western Europe, and thus to increasing lower troposphere (+0.8 °C) and surface temperature (+0.5 °C), namely about 15 % of this heat wave.

Permittivity estimation over Mars by using SHARAD data: the Cerberus Palus area

NASA Astrophysics Data System (ADS)

Alberti, Giovanni; Castaldo, Luigi; Orosei, Roberto; Frigeri, Alessandro; Cirillo, Giuseppe

2012-09-01

Cerberus Palus is a thoroughly studied region of Mars, characterized by evident platy textures that were interpreted either as evidence for a frozen sea close to Mars' equator or as being resultant of lava, mud or ice-flows coming from Cerberus Fossae through Athabasca Valles. Radargrams provided by radar sounder SHARAD clearly show the presence of subsurface layers in the area. By exploiting the great amount of available data, authors have performed an accurate quantitative analysis aimed to estimate electromagnetic properties of surface and subsurface layers, in terms of permittivity and attenuation. To this aim, a simplified electromagnetic approach has been used, but taking into account effects of scattering due to surface roughness, for avoiding overestimated results. This has been done by using theory of electromagnetic scattering from fractal surfaces and by estimating needed parameters from topographic data provided by MOLA. Three distinct geologic formations have been analyzed, namely a part of Zephyria Planum, the Cerberus plains and the bedrock beneath the plains. The retrieved electromagnetic parameters have been also modeled as a mixture of volcanic rocks with either ice or air. The Zephyria Planum material was found to be significantly porous [50-60%] with an attenuation more likely compatible with empty pores. Ambiguous results were obtained for the plains material, being the resulting porosity high in both the cases of empty [40-50%] and of ice-filled [80%] pores. The obtained results do not allow for evidence of a frozen sea on Cerberus Palus area.

Sensitivity of Offshore Surface Fluxes and Sea Breezes to the Spatial Distribution of Sea-Surface Temperature

NASA Astrophysics Data System (ADS)

Lombardo, Kelly; Sinsky, Eric; Edson, James; Whitney, Michael M.; Jia, Yan

2018-03-01

A series of numerical sensitivity experiments is performed to quantify the impact of sea-surface temperature (SST) distribution on offshore surface fluxes and simulated sea-breeze dynamics. The SST simulations of two mid-latitude sea-breeze events over coastal New England are performed using a spatially-uniform SST, as well as spatially-varying SST datasets of 32- and 1-km horizontal resolutions. Offshore surface heat and buoyancy fluxes vary in response to the SST distribution. Local sea-breeze circulations are relatively insensitive, with minimal differences in vertical structure and propagation speed among the experiments. The largest thermal perturbations are confined to the lowest 10% of the sea-breeze column due to the relatively high stability of the mid-Atlantic marine atmospheric boundary layer (ABL) suppressing vertical mixing, resulting in the depth of the marine layer remaining unchanged. Minimal impacts on the column-averaged virtual potential temperature and sea-breeze depth translates to small changes in sea-breeze propagation speed. This indicates that the use of datasets with a fine-scale SST may not produce more accurate sea-breeze simulations in highly stable marine ABL regimes, though may prove more beneficial in less stable sub-tropical environments.

Enhanced Arctic Mean Sea Surface and Mean Dynamic Topography including retracked CryoSat-2 Data

NASA Astrophysics Data System (ADS)

Andersen, O. B.; Jain, M.; Stenseng, L.; Knudsen, P.

2014-12-01

A reliable mean sea surface (MSS) is essential to derive a good mean dynamic topography (MDT) and for the estimation of short and long-term changes in the sea surface. The lack of satellite radar altimetry observations above 82 degrees latitude means that existing mean sea surface models have been unreliable in the Arctic Ocean. We here present the latest DTU mean sea surface and mean dynamic topography models combining conventional altimetry with retracked CryoSat-2 data to improve the reliability in the Arctic Ocean. For the derivation of a mean dynamic topography the ESA GOCE derived geoid model have been used to constrain the longer wavelength. We present the retracking of C2 SAR data using various retrackes and how we have been able to combine data from various retrackers under various sea ice conditions. DTU13MSS and DTU13MDT are the newest state of the art global high-resolution models including CryoSat-2 data to extend the satellite radar altimetry coverage up to 88 degrees latitude and through combination with a GOCE geoid model completes coverage all the way to the North Pole. Furthermore the SAR and SARin capability of CryoSat-2 dramatically increases the amount of useable sea surface returns in sea-ice covered areas compared to conventional radar altimeters like ENVISAT and ERS-1/2. With the inclusion of CryoSat-2 data the new mean sea surface is improved by more than 20 cm above 82 degrees latitude compared with the previous generation of mean sea surfaces.

On the role of inter-basin surface salinity contrasts in global ocean circulation

NASA Astrophysics Data System (ADS)

Seidov, D.; Haupt, B. J.

2002-08-01

The role of sea surface salinity (SSS) contrasts in maintaining vigorous global ocean thermohaline circulation (TOC) is revisited. Relative importance of different generalizations of sea surface conditions in climate studies is explored. Ocean-wide inter-basin SSS contrasts serve as the major controlling element in global TOC. These contrasts are shown to be at least as important as high-latitudinal freshwater impacts. It is also shown that intra-basin longitudinal distribution of sea surface salinity, as well as intra- and inter-basin longitudinal distribution of sea surface temperature, is not crucial to conveyor functionality if only inter-basin contrasts in sea surface salinity are retained. This is especially important for paleoclimate and future climate simulations.

The Impact of Sea Ice Loss on Wave Dynamics and Coastal Erosion Along the Arctic Coast

NASA Astrophysics Data System (ADS)

Overeem, I.; Anderson, R. S.; Wobus, C. W.; Matell, N.; Urban, F. E.; Clow, G. D.; Stanton, T. P.

2010-12-01

The extent of Arctic sea ice has been shrinking rapidly over the past few decades, and attendant acceleration of erosion is now occurring along the Arctic coast. This both brings coastal infrastructure into harm’s way and promotes a complex response of the adjacent landscape to global change. We quantify the effects of declining sea ice extent on coastal erosion rates along a 75-km stretch of coastal permafrost bluffs adjacent to the Beaufort Sea, Alaska, where present-day erosion rates are among the highest in the world at ~14 m yr-1. Our own observations reinforce those of others, and suggest that the rate-limiting process is thermal erosion at the base of the several-meter tall bluffs. Here we focus on the interaction between the nearshore sea ice concentration, the location of the sea ice margin, and the fetch-limited, shallow water wave field, since these parameters ultimately control both sea surface temperatures and the height to which these waters can bathe the frozen bluffs. Thirty years of daily or bi-daily passive microwave data from Nimbus-7 SMMR and DMSP SSM/I satellites reveal that the nearshore open water season lengthened ~54 days over 1979-2009. The open water season, centered in August, expands more rapidly into the fall (September and October~0.92 day yr-1) than into the early summer (July~0.71 days yr-1). Average fetch, defined for our purposes as the distance from the sea ice margin to the coast over which the wind is blowing, increased by a factor 1.7 over the same time-span. Given these time series, we modeled daily nearshore wave heights during the open water season for each year, which we integrated to provide a quantitative metric for the annual exposure of the coastal bluffs to thermal erosion. This “annual wave exposure” increased by 250% during 1979-2009. In the same interval, coastal erosion rates reconstructed from satellite and aerial photo records show less acceleration. We attribute this to a disproportionate extension of the open-water season toward the fall than toward the early summer. This asymmetry fails to tap into the high insolation portion of the summer; expansion into the fall exerts less leverage on coastal change, as sea surface temperatures have significantly declined by late fall. Should the extension of ice-free conditions more strongly advance into the middle of summer, when insolation peaks, we suspect that sea surface temperatures will warm even faster and hence erosion may accelerate yet more strongly.

The dependence of sea surface slope on atmospheric stability and swell conditions

NASA Technical Reports Server (NTRS)

Hwang, Paul A.; Shemdin, Omar H.

1988-01-01

A tower-mounted optical device is used to measure the two-orthogonal components of the sea surface slope. The results indicate that an unstable stratification at the air-sea interface tends to enhance the surface roughness. The presence of a long ocean swell system steers the primary direction of shortwave propagation away from wind direction, and may increase or reduce the mean square slope of the sea surface.

Clear water radiances for atmospheric correction of coastal zone color scanner imagery

NASA Technical Reports Server (NTRS)

Gordon, H. R.; Clark, D. K.

1981-01-01

The possibility of computing the inherent sea surface radiance for regions of clear water from coastal zone color scanner (CZCS) imagery given only a knowledge of the local solar zenith angle is examined. The inherent sea surface radiance is related to the upwelling and downwelling irradiances just beneath the sea surface, and an expression is obtained for a normalized inherent sea surface radiance which is nearly independent of solar zenith angle for low phytoplankton pigment concentrations. An analysis of a data base consisting of vertical profiles of upwelled spectral radiance and pigment concentration, which was used in the development of the CZCS program, confirms the virtual constancy of the normalized inherent sea surface radiance at wavelengths of 520 and 550 nm for cases when the pigment concentration is less than 0.25 mg/cu m. A strategy is then developed for using the normalized inherent sea surface radiance in the atmospheric correction of CZCS imagery.

Mind the gut: genomic insights to population divergence and gut microbial composition of two marine keystone species.

PubMed

Fietz, Katharina; Rye Hintze, Christian Olaf; Skovrind, Mikkel; Kjærgaard Nielsen, Tue; Limborg, Morten T; Krag, Marcus A; Palsbøll, Per J; Hestbjerg Hansen, Lars; Rask Møller, Peter; Gilbert, M Thomas P

2018-05-02

Deciphering the mechanisms governing population genetic divergence and local adaptation across heterogeneous environments is a central theme in marine ecology and conservation. While population divergence and ecological adaptive potential are classically viewed at the genetic level, it has recently been argued that their microbiomes may also contribute to population genetic divergence. We explored whether this might be plausible along the well-described environmental gradient of the Baltic Sea in two species of sand lance (Ammodytes tobianus and Hyperoplus lanceolatus). Specifically, we assessed both their population genetic and gut microbial composition variation and investigated not only which environmental parameters correlate with the observed variation, but whether host genome also correlates with microbiome variation. We found a clear genetic structure separating the high-salinity North Sea from the low-salinity Baltic Sea sand lances. The observed genetic divergence was not simply a function of isolation by distance, but correlated with environmental parameters, such as salinity, sea surface temperature, and, in the case of A. tobianus, possibly water microbiota. Furthermore, we detected two distinct genetic groups in Baltic A. tobianus that might represent sympatric spawning types. Investigation of possible drivers of gut microbiome composition variation revealed that host species identity was significantly correlated with the microbial community composition of the gut. A potential influence of host genetic factors on gut microbiome composition was further confirmed by the results of a constrained analysis of principal coordinates. The host genetic component was among the parameters that best explain observed variation in gut microbiome composition. Our findings have relevance for the population structure of two commercial species but also provide insights into potentially relevant genomic and microbial factors with regards to sand lance adaptation across the North Sea-Baltic Sea environmental gradient. Furthermore, our findings support the hypothesis that host genetics may play a role in regulating the gut microbiome at both the interspecific and intraspecific levels. As sequencing costs continue to drop, we anticipate that future studies that include full genome and microbiome sequencing will be able to explore the full relationship and its potential adaptive implications for these species.

Global warming related transient albedo feedback in the Arctic and its relation to the seasonality of sea ice

NASA Astrophysics Data System (ADS)

Andry, Olivier; Bintanja, Richard; Hazeleger, Wilco

2015-04-01

The Arctic is warming two to three times faster than the global average. Arctic sea ice cover is very sensitive to this warming and has reached historic minima in late summer in recent years (i.e. 2007, 2012). Considering that the Arctic Ocean is mainly ice-covered and that the albedo of sea ice is very high compared to that of open water, the change in sea ice cover is very likely to have a strong impact on the local surface albedo feedback. Here we quantify the temporal changes in surface albedo feedback in response to global warming. Usually feedbacks are evaluated as being representative and constant for long time periods, but we show here that the strength of climate feedbacks in fact varies strongly with time. For instance, time series of the amplitude of the surface albedo feedback, derived from future climate simulations (CIMP5, RCP8.5 up to year 2300) using a kernel method, peaks around the year 2100. This maximum is likely caused by an increased seasonality in sea-ice cover that is inherently associated with sea ice retreat. We demonstrate that the Arctic average surface albedo has a strong seasonal signature with a maximum in spring and a minimum in late summer/autumn. In winter when incoming solar radiation is minimal the surface albedo doesn't have an important effect on the energy balance of the climate system. The annual mean surface albedo is thus determined by the seasonality of both downwelling shortwave radiation and sea ice cover. As sea ice cover reduces the seasonal signature is modified, the transient part from maximum sea ice cover to its minimum is shortened and sharpened. The sea ice cover is reduced when downwelling shortwave radiation is maximum and thus the annual surface albedo is drastically smaller. Consequently the change in annual surface albedo with time will become larger and so will the surface albedo feedback. We conclude that a stronger seasonality in sea ice leads to a stronger surface albedo feedback, which accelerates melting of sea ice. Hence, the change in seasonality and the associated change in feedback strength is an integral part of the positive surface albedo feedback leading to Arctic amplification and diminishing sea ice cover in the next century when global climate warms.

Ocean Classification of Dynamical Structures Detected by SAR and Spectral Methods

NASA Astrophysics Data System (ADS)

Redondo, J. M.; Martinez-Benjamin, J. J.; Tellez, J. D.; Jorge, J.; Diez, M.; Sekula, E.

2016-08-01

We discuss a taxonomy of different dynamical features in the ocean surface and provide some eddy and front statistics, as well as describing some events detected by several satellites and even with additional cruise observations and measurements, in the North-west Mediterranean Sea area between 1996 and 2012. The structure of the flows are presented using self-similar traces that may be used to parametrize mixing at both limits of the Rossby Deformation Radius scale, RL. Results show the ability to identify different SAR signatures and at the same time provide calibrations for the different local configurations of vortices, spirals, Langmuir cells, oil spills and tensioactive slicks that eventually allow the study of the self-similar structure of the turbulence. Depending on the surface wind and wave level, and also on the fetch. the bathimetry, the spiral parameters and the resolution of vortical features change. Previous descriptions did not include the new wind and buoyancy features. SAR images also show the turbulence structure of the coastal area and the Regions of Fresh Water Influence (ROFI). It is noteworthy tt such complex coastal field-dependent behavior is strongly influenced by stratification and rotation of the turbulence spectrum is observed only in the range smaller than the local Rossby deformation radius, RL. The measures of diffusivity from buoy or tracer experiments are used to calibrate the behavior of different tracers and pollutants, both natural and man-made in the NW Mediterranean Sea. Thanks to different polarization and intensity levels in ASAR satellite imagery, these can be used to distinguish between natural and man-made sea surface features due to their distinct self-similar and fractal as a function of spill and slick parameters, environmental conditions and history of both oil releases and weather conditions. Eddy diffusivity map derived from SAR measurements of the ocean surface, performing a feature spatial correlation of the available images of the region are presented. Both the multi fractal discrimination of the local features and the diffusivity measurements are important to evaluate the state of the environment. The distribution of meso-scale vortices of size, the Rossby deformation scale and other dominant features can be used to distinguish features in the ocean surface. Multi-fractal analysis is then very usefull. The SAR images exhibited a large variation of natural features produced by winds, internal waves, the bathymetric distribution, by convection, rain, etc as all of these produce variations in the sea surface roughness so that the topological changes may be studied and classified. In a similar way bathimetry may be studied with the methodology described here using the coastline and the thalwegs as generators of local vertical vorticity.

Equations for normal-mode statistics of sound scattering by a rough elastic boundary in an underwater waveguide, including backscattering.

PubMed

Morozov, Andrey K; Colosi, John A

2017-09-01

Underwater sound scattering by a rough sea surface, ice, or a rough elastic bottom is studied. The study includes both the scattering from the rough boundary and the elastic effects in the solid layer. A coupled mode matrix is approximated by a linear function of one random perturbation parameter such as the ice-thickness or a perturbation of the surface position. A full two-way coupled mode solution is used to derive the stochastic differential equation for the second order statistics in a Markov approximation.

BOREAS AES READAC Surface Meteorological Data

NASA Technical Reports Server (NTRS)

Atkinson, G. Barrie; Funk, Barry; Hall, Forrest G. (Editor); Knapp, David E. (Editor)

2000-01-01

Canadian AES personnel collected and processed data related to surface atmospheric meteorological conditions over the BOREAS region. This data set contains 15-minute meteorological data from one READAC meteorology station in Hudson Bay, Saskatchewan. Parameters include day, time, type of report, sky condition, visibility, mean sea level pressure, temperature, dewpoint, wind, altimeter, opacity, minimum and maximum visibility, station pressure, minimum and maximum air temperature, a wind group, precipitation, and precipitation in the last hour. The data were collected non-continuously from 24-May-1994 to 20-Sep-1994. The data are provided in tabular ASCII files, and are classified as AFM-Staff data.

Improving Wind Predictions in the Marine Atmospheric Boundary Layer through Parameter Estimation in a Single-Column Model

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Jared A.; Hacker, Joshua P.; Delle Monache, Luca

2016-12-14

A current barrier to greater deployment of offshore wind turbines is the poor quality of numerical weather prediction model wind and turbulence forecasts over open ocean. The bulk of development for atmospheric boundary layer (ABL) parameterization schemes has focused on land, partly due to a scarcity of observations over ocean. The 100-m FINO1 tower in the North Sea is one of the few sources worldwide of atmospheric profile observations from the sea surface to turbine hub height. These observations are crucial to developing a better understanding and modeling of physical processes in the marine ABL. In this study, we usemore » the WRF single column model (SCM), coupled with an ensemble Kalman filter from the Data Assimilation Research Testbed (DART), to create 100-member ensembles at the FINO1 location. The goal of this study is to determine the extent to which model parameter estimation can improve offshore wind forecasts.« less

Interpreting sea surface slicks on the basis of the normalized radar cross-section model using RADARSAT-2 copolarization dual-channel SAR images

NASA Astrophysics Data System (ADS)

Ivonin, D. V.; Skrunes, S.; Brekke, C.; Ivanov, A. Yu.

2016-03-01

A simple automatic multipolarization technique for discrimination of main types of thin oil films (of thickness less than the radio wave skin depth) from natural ones is proposed. It is based on a new multipolarization parameter related to the ratio between the damping in the slick of specially normalized resonant and nonresonant signals calculated using the normalized radar cross-section model proposed by Kudryavtsev et al. (2003a). The technique is tested on RADARSAT-2 copolarization (VV/HH) synthetic aperture radar images of slicks of a priori known provenance (mineral oils, e.g., emulsion and crude oil, and plant oil served to model a natural slick) released during annual oil-on-water exercises in the North Sea in 2011 and 2012. It has been shown that the suggested multipolarization parameter gives new capabilities in interpreting slicks visible on synthetic aperture radar images while allowing discrimination between mineral oil and plant oil slicks.

Physical-biogeochemical Interactions in Northwestern Mediterranean, using the Glider "Sea Explorer" fitted with a Newly Developed Fluorescence Sensor, the MiniFluo-UV.

NASA Astrophysics Data System (ADS)

Goutx, M.; Besson, F.; Bhairy, N.; Germain, C.; Guigue, C.; Wassouf, G.; Beguery, L.; Tedetti, M.

2016-02-01

From July 2014 to February 2015, we deployed the SeaExplorer glider (ALSEAMAR Company, Meyreuil, France) fitted with the 2 optical pathways tryptophan-like (TRY-) and phenanthrenes-like (PHE-) MiniFluo-UV fluorescence sensor (french CNRS patent) and other sensors for hydrological and biogeochemical parameters (T, S, Chla, turbidity, humic-like) along the shelf off Marseille and the northern Mediterranean coast. Our goal was to characterize the distributions of dissolved organic matter (DOM) to assess its spatial variability in relation with biological and hydrological features, and human pressure. Interestingly, TRY-like and PHE-like concentrations displayed independent behavior along the bay of Marseille transects whereas they co-varied with physical and other biogeochemical descriptors near the mouth of the Rhone River. Around this highly anthropogenised area, lower salinities and higher concentrations in Chla, TRY- and PHE-like materials were observed. After rainy weather, waters of low salinity and of higher Chla, TRY- and PHE-like concentrations extended further southwards. Tryptophan-like concentrations showed a significant correlation with salinity and Chla indicating a biological source of DOM related to the Rhône inputs. Phenanthrene has different atypical profiles of other parameters showing patches of high concentrations at the surface throughout the transect (shipping) and at depth (sediment resuspension). The distribution of humic acid was controlled by the photo-bleaching. Southeast of the bay, intrusion of low temperature high salinity water in the surface layer was the likely feature of upwelled waters from subjacent layers. This study highlights the interest of coupling the outstanding maneuverability of SeaExplorer for exploring shallow waters and highly dynamic river mouth to the MiniFluo-UV sensor for analyzing the fluorescence properties of sea water. This work received fundings from the European Union's FP7 program within the framework of "NeXOS" project, for research, technological development and demonstration under grant agreement No 614102, in collaboration with ALSEAMAR Company.

Distribution and sources of dissolved black carbon in surface waters of the Chukchi Sea, Bering Sea, and the North Pacific Ocean

NASA Astrophysics Data System (ADS)

Nakane, Motohiro; Ajioka, Taku; Yamashita, Youhei

2017-05-01

Pyrogenic carbon, also called black carbon (BC), is an important component in the global carbon cycle. BC produced by biomass burning or fossil fuel combustion is transported to oceans by the atmosphere or rivers. However, environmental dynamics (i.e., major sources and sinks) of BC in marine environments have not been well documented. In this study, dissolved BC (DBC) collected from surface waters of the Chukchi Sea, the Bering Sea, and the subarctic and subtropical North Pacific were analyzed using the benzene polycarboxylic acid (BPCA) method. The DBC concentration and the ratio of B5CA and B6CA to all BPCAs (an index of the DBC condensation degree) ranged from 4.8 to 15.5 µg-C L-1 and from 0.20 to 0.43, respectively, in surface waters of the Chukchi/Bering Seas and the North Pacific Ocean. The concentration and condensation degree of DBC in the Chukchi/Bering Seas were higher and more variable than those in the subarctic and subtropical North Pacific, which implies that the major factors controlling DBC distribution were different in these marine provinces. In the Chukchi/Bering Seas, the DBC concentration was negatively correlated to salinity but positively correlated to chromophoric dissolved organic matter (CDOM) quantity and total dissolved lignin phenol concentration estimated by CDOM parameters. These correlations indicated that the possible major source of DBC in the Chukchi/Bering Seas was Arctic rivers. However, in the North Pacific, where riverine inputs are negligible for most sampling sites, DBC was possibly derived from the atmosphere. Although spectral slopes of CDOM at 275-295 nm (an index of the photodegradation degree of CDOM) differed widely between the subarctic and subtropical North Pacific, the concentration and condensation degrees of DBC were similar between the subarctic and subtropical North Pacific, which suggests that photodegradation was not the only major factor controlling DBC distribution. Therefore, DBC distributions of the North Pacific Ocean were considered to be mainly controlled by atmospheric deposition of BC and subsequent losses by photodegradation and adsorption onto sinking particles. This study implies that the main influence on DBC distribution in the open ocean and the coastal ocean are atmospheric deposition and fluvial inputs, respectively.

Seasonal variability of the Red Sea, from GRACE time-variable gravity and altimeter sea surface height measurements

NASA Astrophysics Data System (ADS)

Wahr, John; Smeed, David; Leuliette, Eric; Swenson, Sean

2014-05-01

Seasonal variability of sea surface height and mass within the Red Sea, occurs mostly through the exchange of heat with the atmosphere and wind-driven inflow and outflow of water through the strait of Bab el Mandab that opens into the Gulf of Aden to the south. The seasonal effects of precipitation and evaporation, of water exchange through the Suez Canal to the north, and of runoff from the adjacent land, are all small. The flow through the Bab el Mandab involves a net mass transfer into the Red Sea during the winter and a net transfer out during the summer. But that flow has a multi-layer pattern, so that in the summer there is actually an influx of cool water at intermediate (~100 m) depths. Thus, summer water in the southern Red Sea is warmer near the surface due to higher air temperatures, but cooler at intermediate depths (especially in the far south). Summer water in the northern Red Sea experiences warming by air-sea exchange only. The temperature profile affects the water density, which impacts the sea surface height but has no effect on vertically integrated mass. Here, we study this seasonal cycle by combining GRACE time-variable mass estimates, altimeter (Jason-1, Jason-2, and Envisat) measurements of sea surface height, and steric sea surface height contributions derived from depth-dependent, climatological values of temperature and salinity obtained from the World Ocean Atlas. We find good consistency, particularly in the northern Red Sea, between these three data types. Among the general characteristics of our results are: (1) the mass contributions to seasonal SSHT variations are much larger than the steric contributions; (2) the mass signal is largest in winter, consistent with winds pushing water into the Red Sea through the Strait of Bab el Mandab in winter, and out during the summer; and (3) the steric signal is largest in summer, consistent with summer sea surface warming.

Effect of ENSO on the variability of SST and Chlorophyll-a in Java Sea

NASA Astrophysics Data System (ADS)

Wirasatriya, Anindya; Prasetyawan, Indra B.; Triyono, Chandra D.; Muslim; Maslukah, Lilik

2018-02-01

Sea surface temperature (SST) and chlorophyll-a (Chl-a) are two parameters often used for identifying the marine productivity. Located at the maritime continent, the variability of SST and Chl-a in the Indonesian seas is influenced by El Niño Southern Oscillation (ENSO). The previous studies showed that the effect of El Niño tend to decrease SST and increase Chl-a in the areas within the Indonesian seas. Using long time observation of satellite data (2003-2016), it was found different result in Java Sea. Since Java Sea has strong seasonal variability influenced by monsoon wind, the effect of ENSO depend on the season. During southeast monsoon season, El Niño (La Niña) tend to increase (decrease) the speed of southeasterly wind cause the decrease or increase of SST. On the contrary, during northwest monsoon season, El Niño (La Niña) tend to decrease (increase) the speed of northwesterly wind cause the increase (decrease) of SST. The dependence of Chl-a on wind speed is only observed in the off shore which exhibit the strong seasonal variation. However, the effect of ENSO on the variability of Chl-a is not robust since the effected amplitude is less than the RMSE of Chl-a data.

A Comprehensive Review on Water Quality Parameters Estimation Using Remote Sensing Techniques.

PubMed

Gholizadeh, Mohammad Haji; Melesse, Assefa M; Reddi, Lakshmi

2016-08-16

Remotely sensed data can reinforce the abilities of water resources researchers and decision makers to monitor waterbodies more effectively. Remote sensing techniques have been widely used to measure the qualitative parameters of waterbodies (i.e., suspended sediments, colored dissolved organic matter (CDOM), chlorophyll-a, and pollutants). A large number of different sensors on board various satellites and other platforms, such as airplanes, are currently used to measure the amount of radiation at different wavelengths reflected from the water's surface. In this review paper, various properties (spectral, spatial and temporal, etc.) of the more commonly employed spaceborne and airborne sensors are tabulated to be used as a sensor selection guide. Furthermore, this paper investigates the commonly used approaches and sensors employed in evaluating and quantifying the eleven water quality parameters. The parameters include: chlorophyll-a (chl-a), colored dissolved organic matters (CDOM), Secchi disk depth (SDD), turbidity, total suspended sediments (TSS), water temperature (WT), total phosphorus (TP), sea surface salinity (SSS), dissolved oxygen (DO), biochemical oxygen demand (BOD) and chemical oxygen demand (COD).

Preliminary results of fisheries investigation associated with Skylab-3. [remotely sensed distribution and abundance of gamefish in Gulf of Mexico

NASA Technical Reports Server (NTRS)

Savastano, K. J. (Principal Investigator); Pastula, E. J., Jr.; Woods, G.; Faller, K.

1974-01-01

The author has identified the following significant results. This investigation is to establish the feasibility of utilizing remotely sensed data acquired from aircraft and satellite platforms to provide information concerning the distribution and abundance of oceanic gamefish. Data from the test area in the northeastern Gulf of Mexico has made possible the identification of fisheries significant environmental parameters for white marlin. Predictive models based on catch data and surface truth information have been developed and have demonstrated potential for reducing search significantly by identifying areas which have a high probability of being productive. Three of the parameters utilized by the model, chlorophyll-a, sea surface temperature, and turbidity have been inferred from aircraft sensor data. Cloud cover and delayed receipt have inhibited the use of Skylab data. The first step toward establishing the feasibility of utilizing remotely sensed data to assess amd monitor the distribution of ocean gamefish has been taken with the successful identification of fisheries significant oceanographic parameters and the demonstration of the capability of measuring most of these parameters remotely.

A Comprehensive Review on Water Quality Parameters Estimation Using Remote Sensing Techniques

PubMed Central

Gholizadeh, Mohammad Haji; Melesse, Assefa M.; Reddi, Lakshmi

2016-01-01

Remotely sensed data can reinforce the abilities of water resources researchers and decision makers to monitor waterbodies more effectively. Remote sensing techniques have been widely used to measure the qualitative parameters of waterbodies (i.e., suspended sediments, colored dissolved organic matter (CDOM), chlorophyll-a, and pollutants). A large number of different sensors on board various satellites and other platforms, such as airplanes, are currently used to measure the amount of radiation at different wavelengths reflected from the water’s surface. In this review paper, various properties (spectral, spatial and temporal, etc.) of the more commonly employed spaceborne and airborne sensors are tabulated to be used as a sensor selection guide. Furthermore, this paper investigates the commonly used approaches and sensors employed in evaluating and quantifying the eleven water quality parameters. The parameters include: chlorophyll-a (chl-a), colored dissolved organic matters (CDOM), Secchi disk depth (SDD), turbidity, total suspended sediments (TSS), water temperature (WT), total phosphorus (TP), sea surface salinity (SSS), dissolved oxygen (DO), biochemical oxygen demand (BOD) and chemical oxygen demand (COD). PMID:27537896

The feasibility of utilizing remotely sensed data to assess and monitor oceanic gamefish

NASA Technical Reports Server (NTRS)

Savastano, K. J.; Leming, T. D.

1975-01-01

An investigation was conducted to establish the feasibility of utilizing remotely sensed data acquired from aircraft and satellite platforms to provide information concerning the distribution and abundance of oceanic gamefish. The data from the test area was jointly acquired by NASA, the Navy, the Air Force and NOAA/NMFS elements and private and professional fishermen in the northeastern Gulf of Mexico. The data collected has made it possible to identify fisheries significant environmental parameters for white marlin. Prediction models, based on catch data and surface truth information, were developed and demonstrated a potential for significantly reducing search by identifying areas that have a high probability of productivity. Three of the parameters utilized by the models, chlorophyll-a, sea surface temperature, and turbidity were inferred from aircraft sensor data and were tested. Effective use of Skylab data was inhibited by cloud cover and delayed delivery. Initial efforts toward establishing the feasibility of utilizing remotely sensed data to assess and monitor the distribution of oceanic gamefish has successfully identified fisheries significant oceanographic parameters and demonstrated the capability of remotely measuring most of the parameters.

Experimental sea slicks: Their practical applications and utilization for basic studies of air-sea interactions

NASA Astrophysics Data System (ADS)

Hühnerfuss, Heinrich; Garrett, W. D.

1981-01-01

Practical applications of organic surface films added to the sea surface date back to ancient times. Aristotle, Plutarch, and Pliny the Elder describe the seaman's practice of calming waves in a storm by pouring oil onto the sea [Scott, 1977]. It was also noted that divers released oil beneath the water surface so that it could rise and spread over the sea surface, thereby suppressing the irritating flicker associated with the passage of light through a rippled surface. From a scientific point of view, Benjamin Franklin was the first to perform experiments with oils on natural waters. His experiment with a `teaspoonful of oil' on Clapham pond in 1773 inspired many investigators to consider sea surface phenomena or to conduct experiments with oil films. This early research has been reviewed by Giles [1969], Giles and Forrester [1970], and Scott [1977]. Franklin's studies with experimental slicks can be regarded as the beginning of surface film chemistry. His speculations on the wave damping influence of oil induced him to perform the first qualitative experiment with artificial sea slicks at Portsmouth (England) in October of 1773. Although the sea was calmed and very few white caps appeared in the oil-covered area, the swell continued through the oiled area to Franklin's great disappointment.

Electromagnetic backscattering from one-dimensional drifting fractal sea surface II: Electromagnetic backscattering model

NASA Astrophysics Data System (ADS)

Tao, Xie; William, Perrie; Shang-Zhuo, Zhao; He, Fang; Wen-Jin, Yu; Yi-Jun, He

2016-07-01

Sea surface current has a significant influence on electromagnetic (EM) backscattering signals and may constitute a dominant synthetic aperture radar (SAR) imaging mechanism. An effective EM backscattering model for a one-dimensional drifting fractal sea surface is presented in this paper. This model is used to simulate EM backscattering signals from the drifting sea surface. Numerical results show that ocean currents have a significant influence on EM backscattering signals from the sea surface. The normalized radar cross section (NRCS) discrepancies between the model for a coupled wave-current fractal sea surface and the model for an uncoupled fractal sea surface increase with the increase of incidence angle, as well as with increasing ocean currents. Ocean currents that are parallel to the direction of the wave can weaken the EM backscattering signal intensity, while the EM backscattering signal is intensified by ocean currents propagating oppositely to the wave direction. The model presented in this paper can be used to study the SAR imaging mechanism for a drifting sea surface. Project supported by the National Natural Science Foundation of China (Grant No. 41276187), the Global Change Research Program of China (Grant No. 2015CB953901), the Priority Academic Program Development of Jiangsu Higher Education Institutions, China, the Program for the Innovation Research and Entrepreneurship Team in Jiangsu Province, China, the Canadian Program on Energy Research and Development, and the Canadian World Class Tanker Safety Service Program.

Towards quantifying uncertainty in Greenland's contribution to 21st century sea-level rise

NASA Astrophysics Data System (ADS)

Perego, M.; Tezaur, I.; Price, S. F.; Jakeman, J.; Eldred, M.; Salinger, A.; Hoffman, M. J.

2015-12-01

We present recent work towards developing a methodology for quantifying uncertainty in Greenland's 21st century contribution to sea-level rise. While we focus on uncertainties associated with the optimization and calibration of the basal sliding parameter field, the methodology is largely generic and could be applied to other (or multiple) sets of uncertain model parameter fields. The first step in the workflow is the solution of a large-scale, deterministic inverse problem, which minimizes the mismatch between observed and computed surface velocities by optimizing the two-dimensional coefficient field in a linear-friction sliding law. We then expand the deviation in this coefficient field from its estimated "mean" state using a reduced basis of Karhunen-Loeve Expansion (KLE) vectors. A Bayesian calibration is used to determine the optimal coefficient values for this expansion. The prior for the Bayesian calibration can be computed using the Hessian of the deterministic inversion or using an exponential covariance kernel. The posterior distribution is then obtained using Markov Chain Monte Carlo run on an emulator of the forward model. Finally, the uncertainty in the modeled sea-level rise is obtained by performing an ensemble of forward propagation runs. We present and discuss preliminary results obtained using a moderate-resolution model of the Greenland Ice sheet. As demonstrated in previous work, the primary difficulty in applying the complete workflow to realistic, high-resolution problems is that the effective dimension of the parameter space is very large.

Upwelling Dynamic Based on Satellite and INDESO Data in the Flores Sea

NASA Astrophysics Data System (ADS)

Kurniawan, Reski; Suriamihardja, D. A.; Hamzah Assegaf, Alimuddin

2018-03-01

Upwelling phenomenon is crucial to be forecasted, mainly concerning the information of potential fishery areas. Utilization of calibrated model for recorded upwelling such as INDESO gives benefit for historical result up to the present time. The aim of this study is to estimate areas and seasons of upwelling occurrences in the Flores Sea using data assimilation of satellite and modeling result. This study uses sea surface temperature, chlorophyll-a data from level 3 of MODIS image and sea surface height from satellite Jason-2 monthly for three years (2014-2016) and INDESO model data for sea surface temperature, sea surface height, and chlorophyll-a daily for three years (2014-2016). The upwelling is indicated by declining of sea surface temperature, sea surface height and increasing of chlorophyll-a. Verification is conducted by comparing the model result with recorded MODIS satellite image. The result shows that the area of southern Makassar Strait having occurrences of upwelling phenomenon every year starting in June, extended to July and August. The strongest upwelling occurred in 2015 covering more or less the area of 23,000 km2. The relation of monthly data of satellite has significantly correlated with daily data of INDESO model

Three modes of interdecadal trends in sea surface temperature and sea surface height

NASA Astrophysics Data System (ADS)

Gnanadesikan, A.; Pradal, M.

2013-12-01

It might be thought that sea surface height and sea surface temperature would be tightly related. We show that this is not necessarily the case on a global scale. We analysed this relationship in a suite of coupled climate models run under 1860 forcing conditions. The models are low-resolution variants of the GFDL Earth System Model, reported in Galbraith et al. (J. Clim. 2011). 1. Correlated changes in global sea surface height and global sea surface temperature. This mode corresponds to opening and closing of convective chimneys in the Southern Ocean. As the Southern Ocean destratifies, sea ice formation is suppressed during the winter and more heat is taken up during the summer. This mode of variability is highly correlated with changes in the top of the atmosphere radiative budget and weakly correlated with changes in the deep ocean circulation. 2. Uncorrelated changes in global sea surface height and global sea surface temperature. This mode of variability is associated with interdecadal variabliity in tropical winds. Changes in the advective flux of heat to the surface ocean play a critical role in driving these changes, which also result in significant local changes in sea level. Changes sea ice over the Southern Ocean still result in changes in solar absorption, but these are now largely cancelled by changes in outgoing longwave radiation. 3. Anticorrelated changes in global sea surface height and global sea surface temperatures. By varying the lateral diffusion coefficient in the ocean model, we are able to enhance and suppress convection in the Southern and Northern Pacific Oceans. Increasing the lateral diffusion coefficients shifts the balance sources of deep water away from the warm salty deep water of the North Atlantic and towards cold fresh deep water from the other two regions. As a result, even though the planet as a whole warms, the deep ocean cools and sea level falls, with changes of order 30 cm over 500 years. The increase in solar absorption in polar regions is more than compensated by an increase in outgoing longwave radiation. Relationship between global SSH trend over a decade and (A) local SSH change over a decade (m/m). (B) Global SST change over a decade (m/K) (C) Portion of decadal SST change correlated with net radiation at the top of the atmosphere (m/K) (D) Portion of decadal SST change not correlated with net radiation at the top of the atmosphere.

Quantifying thermohaline circulations: seawater isotopic compositions and salinity as proxies of the ratio between advection time and evaporation time

NASA Astrophysics Data System (ADS)

Paldor, N.; Berman, H.; Lazar, B.

2017-12-01

Uncertainties in quantitative estimates of the thermohaline circulation in any particular basin are large, partly due to large uncertainties in quantifying excess evaporation over precipitation and surface velocities. A single nondimensional parameter, γ=(qx)/(hu) is proposed to characterize the "strength" of the thermohaline circulation by combining the physical parameters of surface velocity (u), evaporation rate (q), mixed layer depth (h) and trajectory length (x). Values of g can be estimated directly from cross-sections of salinity or seawater isotopic composition (δ18O and δD). Estimates of q in the Red Sea and the South-West Indian Ocean are 0.1 and 0.02, respectively, which implies that the thermohaline contribution to the circulation in the former is higher than in the latter. Once the value of g has been determined in a particular basin, either q or u can be estimated from known values of the remaining parameters. In the studied basins such estimates are consistent with previous studies.

Assessing Air-Sea Interaction in the Evolving NASA GEOS Model

NASA Technical Reports Server (NTRS)

Clayson, Carol Anne; Roberts, J. Brent

2015-01-01

In order to understand how the climate responds to variations in forcing, one necessary component is to understand the full distribution of variability of exchanges of heat and moisture between the atmosphere and ocean. Surface heat and moisture fluxes are critical to the generation and decay of many coupled air-sea phenomena. These mechanisms operate across a number of scales and contain contributions from interactions between the anomalous (i.e. non-mean), often extreme-valued, flux components. Satellite-derived estimates of the surface turbulent and radiative heat fluxes provide an opportunity to assess results from modeling systems. Evaluation of only time mean and variability statistics, however only provides limited traceability to processes controlling what are often regime-dependent errors. This work will present an approach to evaluate the representation of the turbulent fluxes at the air-sea interface in the current and evolving Goddard Earth Observing System (GEOS) model. A temperature and moisture vertical profile-based clustering technique is used to identify robust weather regimes, and subsequently intercompare the turbulent fluxes and near-surface parameters within these regimes in both satellite estimates and GEOS-driven data sets. Both model reanalysis (MERRA) and seasonal-to-interannual coupled GEOS model simulations will be evaluated. Particular emphasis is placed on understanding the distribution of the fluxes including extremes, and the representation of near-surface forcing variables directly related to their estimation. Results from these analyses will help identify the existence and source of regime-dependent biases in the GEOS model ocean surface turbulent fluxes. The use of the temperature and moisture profiles for weather-state clustering will be highlighted for its potential broad application to 3-D output typical of model simulations.

Assessing air-sea interaction in the evolving NASA GEOS model

NASA Astrophysics Data System (ADS)

Clayson, C. A.; Roberts, J. B.

2014-12-01

In order to understand how the climate responds to variations in forcing, one necessary component is to understand the full distribution of variability of exchanges of heat and moisture between the atmosphere and ocean. Surface heat and moisture fluxes are critical to the generation and decay of many coupled air-sea phenomena. These mechanisms operate across a number of scales and contain contributions from interactions between the anomalous (i.e. non-mean), often extreme-valued, flux components. Satellite-derived estimates of the surface turbulent and radiative heat fluxes provide an opportunity to assess results from modeling systems. Evaluation of only time mean and variability statistics, however only provides limited traceability to processes controlling what are often regime-dependent errors. This work will present an approach to evaluate the representation of the turbulent fluxes at the air-sea interface in the current and evolving Goddard Earth Observing System (GEOS) model. A temperature and moisture vertical profile-based clustering technique is used to identify robust weather regimes, and subsequently intercompare the turbulent fluxes and near-surface parameters within these regimes in both satellite estimates and GEOS-driven data sets. Both model reanalysis (MERRA) and seasonal-to-interannual coupled GEOS model simulations will be evaluated. Particular emphasis is placed on understanding the distribution of the fluxes including extremes, and the representation of near-surface forcing variables directly related to their estimation. Results from these analyses will help identify the existence and source of regime-dependent biases in the GEOS model ocean surface turbulent fluxes. The use of the temperature and moisture profiles for weather-state clustering will be highlighted for its potential broad application to 3-D output typical of model simulations.

GNSS-Reflectometry aboard ISS with GEROS: Investigation of atmospheric propagation effects

NASA Astrophysics Data System (ADS)

Zus, F.; Heise, S.; Wickert, J.; Semmling, M.

2015-12-01

GEROS-ISS (GNSS rEflectometry Radio Occultation and Scatterometry) is an ESA mission aboard the International Space Station (ISS). The main mission goals are the determination of the sea surface height and surface winds. Secondary goals are monitoring of land surface parameters and atmosphere sounding using GNSS radio occultation measurements. The international scientific study GARCA (GNSS-Reflectometry Assessment of Requirements and Consolidation of Retrieval Algorithms), funded by ESA, is part of the preparations for GEROS-ISS. Major goals of GARCA are the development of an end2end Simulator for the GEROS-ISS measurements (GEROS-SIM) and the evaluation of the error budget of the GNSS reflectometry measurements. In this presentation we introduce some of the GARCA activities to quantify the influence of the ionized and neutral atmosphere on the altimetric measurements, which is a major error source for GEROS-ISS. At first, we analyse, to which extend the standard linear combination of interferometric paths at different carrier frequencies can be used to correct for the ionospheric propagation effects. Second, we make use of the tangent-linear version of our ray-trace algorithm to propagate the uncertainty of the underlying refractivity profile into the uncertainty of the interferometric path. For comparison the sensitivity of the interferometric path with respect to the sea surface height is computed. Though our calculations are based on a number of simplifying assumptions (the Earth is a sphere, the atmosphere is spherically layered and the ISS and GNSS satellite orbits are circular) some general conclusions can be drawn. In essence, for elevation angles above -5° at the ISS the higher-order ionospheric errors and the uncertaintiy of the inteferometric path due to the uncertainty of the underlying refractivity profile are small enough to distinguish a sea surface height of ± 0.5 m.

Sea surface temperature measurements with AIRS

NASA Technical Reports Server (NTRS)

Aumann, H.

2003-01-01

The comparison of global sea surface skin temperature derived from cloud-free AIRS super window channel at 2616 cm-1 (sst2616) with the Real-Time Global Sea Surface Temperature for September 2002 shows surprisingly small standard deviation of 0.44K.

Response of air-sea carbon fluxes and climate to orbital forcing changes in the Community Climate System Model

NASA Astrophysics Data System (ADS)

Jochum, M.; Peacock, S.; Moore, K.; Lindsay, K.

2010-07-01

A global general circulation model coupled to an ocean ecosystem model is used to quantify the response of carbon fluxes and climate to changes in orbital forcing. Compared to the present-day simulation, the simulation with the Earth's orbital parameters from 115,000 years ago features significantly cooler northern high latitudes but only moderately cooler southern high latitudes. This asymmetry is explained by a 30% reduction of the strength of the Atlantic Meridional Overturning Circulation that is caused by an increased Arctic sea ice export and a resulting freshening of the North Atlantic. The strong northern high-latitude cooling and the direct insolation induced tropical warming lead to global shifts in precipitation and winds to the order of 10%-20%. These climate shifts lead to regional differences in air-sea carbon fluxes of the same order. However, the differences in global net air-sea carbon fluxes are small, which is due to several effects, two of which stand out: first, colder sea surface temperature leads to a more effective solubility pump but also to increased sea ice concentration which blocks air-sea exchange, and second, the weakening of Southern Ocean winds that is predicted by some idealized studies occurs only in part of the basin, and is compensated by stronger winds in other parts.

Sea spray aerosol fluxes in the Baltic Sea region: Comparison of the WAM model with measurements

NASA Astrophysics Data System (ADS)

Markuszewski, Piotr; Kosecki, Szymon; Petelski, Tomasz

2017-08-01

Sea spray aerosol flux is an important element of sub-regional climate modeling. The majority of works related to this topic concentrate on open ocean research rather than on smaller, inland seas, e.g., the Baltic Sea. The Baltic Sea is one of the largest brackish inland seas by area, where major inflows of oceanic waters are rare. Furthermore, surface waves in the Baltic Sea have a relatively shorter lifespan in comparison with oceanic waves. Therefore, emission of sea spray aerosol may differ greatly from what is known from oceanic research and should be investigated. This article presents a comparison of sea spray aerosol measurements carried out on-board the s/y Oceania research ship with data calculated in accordance to the WAM model. The measurements were conducted in the southern region of the Baltic Sea during four scientific cruises. The gradient method was used to determinate aerosol fluxes. The fluxes were calculated for particles of diameter in range of 0.5-47 μm. The correlation between wind speed measured and simulated has a good agreement (correlation in range of 0.8). The comparison encompasses three different sea spray generation models. First, function proposed by Massel (2006) which is based only on wave parameters, such as significant wave height and peak frequency. Second, Callaghan (2013) which is based on Gong (2003) model (wind speed relation), and a thorough experimental analysis of whitecaps. Third, Petelski et al. (2014) which is based on in-situ gradient measurements with the function dependent on wind speed. The two first models which based on whitecaps analysis are insufficient. Moreover, the research shows strong relation between aerosol emission and wind speed history.

Numerical simulation of inter-annual variations in the properties of the upper mixed layer in the Black Sea over the last 34 years

NASA Astrophysics Data System (ADS)

Shapiro, Georgy I.; Wobus, Fred; Zatsepin, Andrei G.; Akivis, Tatiana M.; Zanacchi, Marcus; Stanichny, Sergey

2014-05-01

The Black Sea is a nearly land-locked basin where a combination of salt and heat budgets results in a unique thermohaline water mass structure. An important feature of the Black Sea is that oxygen is dissolved and rich sea life made possible only in the upper water levels. This is due to a strong pycnocline which cannot be mixed even by strong winds or winter convection (Shapiro, 2008). The upper mixed layer (UML) with a nearly uniform temperature profile and a very sharp seasonal thermocline at its lower boundary develops during the summer season (Sur & Ilyin, 1997). The deepening of the UML has an important effect on the supply of nutrients into the euphotic upper layer from the underlying nutrient-rich water mass. The temperature of the UML at any given location is dependent on the surface heat flux, horizontal advection of heat, the depth and the rate of deepening of the UML. In this study we use a 3D ocean circulation model, NEMO-SHELF (O'Dea et al, 2012) to simulate the parameters of the UML in the Black Sea over the last 34 years. The model has horizontal resolution of 1/12×1/16 degrees and 33 layers in the vertical. The vertical discretization uses a hybrid enveloped s-z grid developed in Shapiro et al. (2012). The model is spun up from climatology (Suvorov et al., 2004); it is forced by the Drakkar Forcing Set v5.2 (Brodeau et al., 2010, Meinvielle et al., 2013) and river discharges from 8 major rivers are included. For each year the model is run from 1st January and the data for the period April to October are used for analysis. The sea surface temperature produced by the model is compared with satellite data ( Modis-Aqua, 2013) to show a good agreement. The model simulations are validated against in-situ observations (BSERP-3, 2004; Piotukh et al., 2011). The analysis is performed for the deep basin where the depth of the sea is greater than 1000m. It clearly shows the inter-annual variations of both the SST and the depth of UML. The depth of UML is calculated using the method by Thomson (1976). It is highly dependent on the meteorological forcing, in particular the wind speed. The correlation between the variations of parameters of UML, the weather patterns, buoyancy fluxes and the kinetic energy of the UML circulation is analysed. This study was supported by EU FP7 PERSEUS and EU FP7 MyOcean2 projects. References BSERP-3. Black Sea Ecosystem Recovery Project. BSERP-3 cruise, May 2004. http://www.research.plymouth.ac.uk/shelf/projects/Black_sea/C_S_BSERP3_final.pdf, 2004. Brodeau, L., B. Barnier, A-M. Treguier, T. Penduff, S. Gulev : An ERA40-based atmospheric forcing for global ocean circulation models, Ocean Modelling, 31, (3-4), 88-104, 2010, http://dx.doi.org/10.1016/j.ocemod.2009.10.005 Meinvielle, M., Brankart, J.-M., Brasseur, P., Barnier, B., Dussin, R., and Verron, J.: Optimal adjustment of the atmospheric forcing parameters of ocean models using sea surface temperature data assimilation, Ocean Sci., 9, 867-883, doi:10.5194/os-9-867-2013, 2013. MODIS-AQUA. http://aqua.nasa.gov/science/images_data.php, 2013. O'Dea, E. J., While, J., Furner, R., Arnold, A., Hyder, P., Storkey, D., Edwards, K.P., Siddorn, J.R., Martin, M.J., Liu, H., Holt, J.T.: An operational ocean forecast system incorporating SST data assimilation for the tidally driven European North-West European shelf. Journal of Operational Oceanography, 5, 3-17, 2012. Piotukh V.B., Zatsepin A.G., Kazmin A.S., Yakubenko V.G.: Impact of the winter cooling on the variability of the thermohaline characteristics of the active layer in the Black Sea. Oceanology, 41, 2, 221-230, 2011 Shapiro, G.I.: Black Sea Circulation. In: Encyclopedia of Ocean Sciences (Second Edition). Eds: J. H. Steele, K. K. Turekian, and S. A. Thorpe. ISBN: 978-0-12-374473-9, P.3519-3532, 2008. Sur, H. I., and Y. P. Ilyin: Evolution of satellite derived mesoscale thermal patterns in the Black Sea, Prog. Oceanogr., 39, 109-151, 1997 Suvorov, A.M., Eremeev, V.N., Belokopytov, V.N., Khaliulin, A.H., Godin, E.A., Ingerov, A.V., Palmer, D.R. and Levitus, S.: Digital Atlas: Physical Oceanography of the Black Sea. (CD-ROM), Environmental Services Data and Information Management Program, Marine Hydrophysical Institute of the National Academy of Sciences of Ukraine, 2004. Thompson, R. O. R. Y.: Climatological numerical models of the surface mixed layer of the ocean, J. Phys. Oceanogr., 6, 496-603, 1976

Towards The Operational Oceanographic Model System In Estonian Coastal Sea, Baltic Sea

NASA Astrophysics Data System (ADS)

Kõuts, T.; Elken, J.; Raudsepp, U.

An integrated system of nested 2D and 3D hydrodynamic models together with real time forcing data asquisition is designed and set up in pre-operational mode in the Gulf of Finland and Gulf of Riga, the Baltic Sea. Along the Estonian coast, implicit time-stepping 3D models are used in the deep bays and 2D models in the shallow bays with ca 200 m horizontal grid step. Specific model setups have been verified by in situ current measurements. Optimum configuration of initial parameters has been found for certain critical locations, usually ports, oil terminals, etc. Operational system in- tegrates also section of historical database of most important hydrologic parameters in the region, allowing use of certain statistical analysis and proper setup of initial conditions for oceanographic models. There is large variety of applications for such model system, ranging from environmental impact assessment at local coastal sea pol- lution problems to forecast of offshore blue algal blooms. Most probable risk factor in the coastal sea engineering is oil pollution, therefore current operational model sys- tem has direct custom oriented output the oil spill forecast for critical locations. Oil spill module of the operational system consist the automatic weather and hydromet- ric station (distributed in real time to internet) and prognostic model of sea surface currents. System is run using last 48 hour wind data and wind forecast and estimates probable oil deposition areas on the shoreline under certain weather conditions. Cal- culated evolution of oil pollution has been compared with some real accidents in the past and there was found good agreement between model and measurements. Graphi- cal user interface of oil spill model is currently installed at location of port authorities (eg. Muuga port), so in case of accidents it could be used in real time supporting the rescue operations. In 2000 current pre-operational oceanographic model system has been sucessfully used to evaluate environmental impacts of three different deep-port construction options in Saaremaa, NW the Baltic Sea. Intensive campaign of field measurements, consisting the high-resolution surveys of thermohaline properties of water masses (CTD) and timeseries as well horisontal structure of currents were in good agreement with model calculations. Model system well simulated the transport of pollution by surface currents originating from potential port locations at NW coast of the Saaremaa. It allowed to choose the optimum location for port and give also some hindcasts for port construction and exploitation.

In situ observations of Arctic cloud properties across the Beaufort Sea marginal ice zone

NASA Astrophysics Data System (ADS)

Corr, C.; Moore, R.; Winstead, E.; Thornhill, K. L., II; Crosbie, E.; Ziemba, L. D.; Beyersdorf, A. J.; Chen, G.; Martin, R.; Shook, M.; Corbett, J.; Smith, W. L., Jr.; Anderson, B. E.

2016-12-01

Clouds play an important role in Arctic climate. This is particularly true over the Arctic Ocean where feedbacks between clouds and sea-ice impact the surface radiation budget through modifications of sea-ice extent, ice thickness, cloud base height, and cloud cover. This work summarizes measurements of Arctic cloud properties made aboard the NASA C-130 aircraft over the Beaufort Sea during ARISE (Arctic Radiation - IceBridge Sea&Ice Experiment) in September 2014. The influence of surface-type on cloud properties is also investigated. Specifically, liquid water content (LWC), droplet concentrations, and droplet size distributions are compared for clouds sampled over three distinct regimes in the Beaufort Sea: 1) open water, 2) the marginal ice zone, and 3) sea-ice. Regardless of surface type, nearly all clouds intercepted during ARISE were liquid-phase clouds. However, differences in droplet size distributions and concentrations were evident for the surface types; clouds over the MIZ and sea-ice generally had fewer and larger droplets compared to those over open water. The potential implication these results have for understanding cloud-surface albedo climate feedbacks in Arctic are discussed.

Quantifying Uncertainty in the Greenland Surface Mass Balance Elevation Feedback

NASA Astrophysics Data System (ADS)

Edwards, T.

2015-12-01

As the shape of the Greenland ice sheet responds to changes in surface mass balance (SMB) and dynamics, it affects the surface mass balance through the atmospheric lapse rate and by altering atmospheric circulation patterns. Positive degree day models include simplified representations of this feedback, but it is difficult to simulate with state-of-the-art models because it requires coupling of regional climate models with dynamical ice sheet models, which is technically challenging. This difficulty, along with the high computational expense of regional climate models, also drastically limits opportunities for exploring the impact of modelling uncertainties on sea level projections. We present a parameterisation of the SMB-elevation feedback in the MAR regional climate model that provides a far easier and quicker estimate than atmosphere-ice sheet model coupling, which can be used with any ice sheet model. This allows us to use ensembles of different parameter values and ice sheet models to assess the effect of uncertainty in the feedback and ice sheet model structure on future sea level projections. We take a Bayesian approach to uncertainty in the feedback parameterisation, scoring the results from multiple possible "SMB lapse rates" according to how well they reproduce a MAR simulation with altered ice sheet topography. We test the impact of the resulting parameterisation on sea level projections using five ice sheet models forced by MAR (in turned forced by two different global climate models) under the emissions scenario A1B. The estimated additional sea level contribution due to the SMB-elevation feedback is 4.3% at 2100 (95% credibility interval 1.8-6.9%), and 9.6% at 2200 (3.6-16.0%).

Bringing the Coastal Zone into Finer Focus

NASA Astrophysics Data System (ADS)

Guild, L. S.; Hooker, S. B.; Kudela, R. M.; Morrow, J. H.; Torres-Perez, J. L.; Palacios, S. L.; Negrey, K.; Dungan, J. L.

2015-12-01

Measurements over extents from submeter to 10s of meters are critical science requirements for the design and integration of remote sensing instruments for coastal zone research. Various coastal ocean phenomena operate at different scales (e.g. meters to kilometers). For example, river plumes and algal blooms have typical extents of 10s of meters and therefore can be resolved with satellite data, however, shallow benthic ecosystem (e.g., coral, seagrass, and kelp) biodiversity and change are best studied at resolutions of submeter to meter, below the pixel size of typical satellite products. The delineation of natural phenomena do not fit nicely into gridded pixels and the coastal zone is complicated by mixed pixels at the land-sea interface with a range of bio-optical signals from terrestrial and water components. In many standard satellite products, these coastal mixed pixels are masked out because they confound algorithms for the ocean color parameter suite. In order to obtain data at the land/sea interface, finer spatial resolution satellite data can be achieved yet spectral resolution is sacrificed. This remote sensing resolution challenge thwarts the advancement of research in the coastal zone. Further, remote sensing of benthic ecosystems and shallow sub-surface phenomena are challenged by the requirements to sense through the sea surface and through a water column with varying light conditions from the open ocean to the water's edge. For coastal waters, >80% of the remote sensing signal is scattered/absorbed due to the atmospheric constituents, sun glint from the sea surface, and water column components. In addition to in-water measurements from various platforms (e.g., ship, glider, mooring, and divers), low altitude aircraft outfitted with high quality bio-optical radiometer sensors and targeted channels matched with in-water sensors and higher altitude platform sensors for ocean color products, bridge the sea-truth measurements to the pixels acquired from satellite and high altitude platforms. We highlight a novel NASA airborne calibration, validation, and research capability for addressing the coastal remote sensing resolution challenge.

Leads Detection Using Mixture Statistical Distribution Based CRF Algorithm from Sentinel-1 Dual Polarization SAR Imagery

NASA Astrophysics Data System (ADS)

Zhang, Yu; Li, Fei; Zhang, Shengkai; Zhu, Tingting

2017-04-01

Synthetic Aperture Radar (SAR) is significantly important for polar remote sensing since it can provide continuous observations in all days and all weather. SAR can be used for extracting the surface roughness information characterized by the variance of dielectric properties and different polarization channels, which make it possible to observe different ice types and surface structure for deformation analysis. In November, 2016, Chinese National Antarctic Research Expedition (CHINARE) 33rd cruise has set sails in sea ice zone in Antarctic. Accurate leads spatial distribution in sea ice zone for routine planning of ship navigation is essential. In this study, the semantic relationship between leads and sea ice categories has been described by the Conditional Random Fields (CRF) model, and leads characteristics have been modeled by statistical distributions in SAR imagery. In the proposed algorithm, a mixture statistical distribution based CRF is developed by considering the contexture information and the statistical characteristics of sea ice for improving leads detection in Sentinel-1A dual polarization SAR imagery. The unary potential and pairwise potential in CRF model is constructed by integrating the posteriori probability estimated from statistical distributions. For mixture statistical distribution parameter estimation, Method of Logarithmic Cumulants (MoLC) is exploited for single statistical distribution parameters estimation. The iteration based Expectation Maximal (EM) algorithm is investigated to calculate the parameters in mixture statistical distribution based CRF model. In the posteriori probability inference, graph-cut energy minimization method is adopted in the initial leads detection. The post-processing procedures including aspect ratio constrain and spatial smoothing approaches are utilized to improve the visual result. The proposed method is validated on Sentinel-1A SAR C-band Extra Wide Swath (EW) Ground Range Detected (GRD) imagery with a pixel spacing of 40 meters near Prydz Bay area, East Antarctica. Main work is listed as follows: 1) A mixture statistical distribution based CRF algorithm has been developed for leads detection from Sentinel-1A dual polarization images. 2) The assessment of the proposed mixture statistical distribution based CRF method and single distribution based CRF algorithm has been presented. 3) The preferable parameters sets including statistical distributions, the aspect ratio threshold and spatial smoothing window size have been provided. In the future, the proposed algorithm will be developed for the operational Sentinel series data sets processing due to its less time consuming cost and high accuracy in leads detection.

Two centuries of observed atmospheric variability and change over the North Sea region

NASA Astrophysics Data System (ADS)

Stendel, Martin; van den Besselaar, Else; Hannachi, Abdel; Kent, Elizabeth; Lefebvre, Christiana; van Oldenborgh, Geert Jan; Rosenhagen, Gudrun; Schenk, Frederik; van der Schrier, Gerard

2015-04-01

Situated in northwestern Europe, the North Sea region is under influence of air masses from subtropical to arctic origin, and thus exhibits significant natural climate variability. As the land areas surrounding the North Sea are densely populated, climate change is an important issue in terms of e.g. coastal protection, fishery and trade. This study is part of the NOSCCA initiative (North Sea Region Climate Change Assessment) and presents observed variability and changes in atmospheric parameters during the last roughly 200 years. Circulation patterns show considerable decadal variability. In recent decades, a northward shift of storm tracks and increased cyclonic activity has been observed. There is also an indication of increased persistence of weather types. The wind climate is dominated by large multidecadal variability, and no robust long-term trends can be identified in the available datasets. There is a clear positive trend in near-surface temperatures, in particular during spring and winter. Over the region as a whole, no clear long-term precipitation trends are visible, although regional indications exist for an increased risk of extreme precipitation events.

The SeaFlux Turbulent Flux Dataset Version 1.0 Documentation

NASA Technical Reports Server (NTRS)

Clayson, Carol Anne; Roberts, J. Brent; Bogdanoff, Alec S.

2012-01-01

Under the auspices of the World Climate Research Programme (WCRP) Global Energy and Water cycle EXperiment (GEWEX) Data and Assessment Panel (GDAP), the SeaFlux Project was created to investigate producing a high-resolution satellite-based dataset of surface turbulent fluxes over the global oceans. The most current release of the SeaFlux product is Version 1.0; this represents the initial release of turbulent surface heat fluxes, associated near-surface variables including a diurnally varying sea surface temperature.

An alternative to reduction of surface pressure to sea level

NASA Technical Reports Server (NTRS)

Deardorff, J. W.

1982-01-01

The pitfalls of the present method of reducing surface pressure to sea level are reviewed, and an alternative, adjusted pressure, P, is proposed. P is obtained from solution of a Poisson equation over a continental region, using the simplest boundary condition along the perimeter or coastline where P equals the sea level pressure. The use of P would avoid the empiricisms and disadvantages of pressure reduction to sea level, and would produce surface pressure charts which depict the true geostrophic wind at the surface.

Visible and Thermal Imaging of Sea Ice and Open Water from Coast Guard Arctic Domain Awareness Flights

DTIC Science & Technology

2014-09-30

dropsondes, micro- aircraft), cloud top/base heights Arctic Ocean Surface Temperature project Steele Buoy drops for SLP , SST, SSS, & surface velocity...Colón & Vancas (NIC) Drop buoys for SLP , temperature and surface velocity Waves & Fetch in the MIZ Thompson SWIFTS buoys measuring wave energy...Expendable CTD, AXCP= Air Expendable Current Profiler, SLP = Sea Level atmospheric Pressure, SST= Seas Surface Temperature, A/C= aircraft, FSD= Floe Size Distribution, SIC=Sea Ice Concentration

An atlas of monthly mean distributions of GEOSAT sea surface height, SSMI surface wind speed, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1988

NASA Technical Reports Server (NTRS)

Halpern, D.; Zlotnicki, V.; Newman, J.; Brown, O.; Wentz, F.

1991-01-01

Monthly mean global distributions for 1988 are presented with a common color scale and geographical map. Distributions are included for sea surface height variation estimated from GEOSAT; surface wind speed estimated from the Special Sensor Microwave Imager on the Defense Meteorological Satellite Program spacecraft; sea surface temperature estimated from the Advanced Very High Resolution Radiometer on NOAA spacecrafts; and the Cartesian components of the 10m height wind vector computed by the European Center for Medium Range Weather Forecasting. Charts of monthly mean value, sampling distribution, and standard deviation value are displayed. Annual mean distributions are displayed.

Response surface optimization of extraction protocols to obtain phenolic rich antioxidant from sea buckthorn and their potential application into model meat system.

PubMed

Wagh, Rajesh V; Chatli, Manish K

2017-05-01

In the present study, processing parameters for the extraction of phenolic rich sea buckthorn seed (SBTE) extract were optimised using response surface method and subjected for in vitro efficacy viz. total phenolic, ABTS, DPPH and SASA activity. The optimised model depicted MeOH as a solvent at 60% concentration level with a reaction time of 20 min and extracting temperature of 55 °C for the highest yield and total phenolic content. The efficacy of different concentration of obtained SBT was evaluated in raw ground pork as a model meat system on the basis of various physico-chemical, microbiological, sensory quality characteristics. Addition of 0.3% SBTE significantly reduced the lipid peroxidation (PV, TBARS and FFA) and improved instrumental colour ( L* , a*, b* ) attributes of raw ground pork during refrigerated storage of 9 days. Results concluded that SBTE at 0.3% level can successfully improve the oxidative stability, microbial, sensory quality attributes in the meat model system.

Influence of turning Treatments on Al6061 by Offline Inspection Technique

NASA Astrophysics Data System (ADS)

Annigeri, Ulhas K.; Sandeep, K. L. G.; Prasanna Chaitanya, M.; Sairam Varma, G.; Datta, B. Arun

2018-02-01

Aluminium is mostly extracted from bauxite and is frequently being utilised in the manufacture of sea, land and air vehicles. Since, it has the merit of resistance to corrosion it is frequently being used in sea vehicles. Another outstanding merit of aluminium is its weight which is very less compared to other ferrous materials. In our study, we have selected Al6061 as the material and based on full factorial design the surface roughness has been observed with three base parameters speed, feed and depth of cut. A mathematical model has been developed to predict the surface roughness and also the dominant factor affecting the turning process has been determined. The plots such as main effects, interaction and Pareto chart have been analysed to give an effective conclusion to the process followed in the study. The purpose of these experiments to compare the effect of process treatments in all possible pairs to select the best treatment to the process has been done satisfactorily.

The Diversity of Cloud Responses to Twentieth Century Sea Surface Temperatures

NASA Astrophysics Data System (ADS)

Silvers, Levi G.; Paynter, David; Zhao, Ming

2018-01-01

Low-level clouds are shown to be the conduit between the observed sea surface temperatures (SST) and large decadal fluctuations of the top of the atmosphere radiative imbalance. The influence of low-level clouds on the climate feedback is shown for global mean time series as well as particular geographic regions. The changes of clouds are found to be important for a midcentury period of high sensitivity and a late century period of low sensitivity. These conclusions are drawn from analysis of amip-piForcing simulations using three atmospheric general circulation models (AM2.1, AM3, and AM4.0). All three models confirm the importance of the relationship between the global climate sensitivity and the eastern Pacific trends of SST and low-level clouds. However, this work argues that the variability of the climate feedback parameter is not driven by stratocumulus-dominated regions in the eastern ocean basins, but rather by the cloudy response in the rest of the tropics.

An Evaluation of Sea Surface Temperature as Measured by the Nimbus 1 High Resolution Infrared Radiometer

NASA Technical Reports Server (NTRS)

Allison, Lewis J.; Kennedy, James S.

1967-01-01

An analysis of Nimbus I HRIR data over various parts of the world indicated limited success in deriving sea surface temperatures to within 3 to 6 K of aircraft radiation measurements (8- 13 microns) and synoptic-climatological ship sea surface temperature data. The areas studied included the east, west and Gulf coasts of the United States, West Greenland, Nova Scotia, southern Japan, the eastern Mediterranean Sea, Caspian Sea, Persian Gulf, and the Indian Ocean. At night, thin clouds which may fill the radiometer's field of view make it difficult to interpret the absolute values of derived sea surface temperature. During the daytime, the HRIR data is unusable for oceanographic temperature analysis because the contamination by reflected solar radiation mixes with the emitted radiation. Future satellite instrumentation, consisting of a HFUR radiometer (10-11 microns) when used in conjunction with television. data, will delineate cloud free ocean areas and permit the daily derivation of sea surface temperatures from approximately 10 to 30 Percent of the world's oceanic regions.

Using state-space models to predict the abundance of juvenile and adult sea lice on Atlantic salmon.

PubMed

Elghafghuf, Adel; Vanderstichel, Raphael; St-Hilaire, Sophie; Stryhn, Henrik

2018-04-11

Sea lice are marine parasites affecting salmon farms, and are considered one of the most costly pests of the salmon aquaculture industry. Infestations of sea lice on farms significantly increase opportunities for the parasite to spread in the surrounding ecosystem, making control of this pest a challenging issue for salmon producers. The complexity of controlling sea lice on salmon farms requires frequent monitoring of the abundance of different sea lice stages over time. Industry-based data sets of counts of lice are amenable to multivariate time-series data analyses. In this study, two sets of multivariate autoregressive state-space models were applied to Chilean sea lice data from six Atlantic salmon production cycles on five isolated farms (at least 20 km seaway distance away from other known active farms), to evaluate the utility of these models for predicting sea lice abundance over time on farms. The models were constructed with different parameter configurations, and the analysis demonstrated large heterogeneity between production cycles for the autoregressive parameter, the effects of chemotherapeutant bath treatments, and the process-error variance. A model allowing for different parameters across production cycles had the best fit and the smallest overall prediction errors. However, pooling information across cycles for the drift and observation error parameters did not substantially affect model performance, thus reducing the number of necessary parameters in the model. Bath treatments had strong but variable effects for reducing sea lice burdens, and these effects were stronger for adult lice than juvenile lice. Our multivariate state-space models were able to handle different sea lice stages and provide predictions for sea lice abundance with reasonable accuracy up to five weeks out. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

Observing and modelling phytoplankton community structure in the North Sea

NASA Astrophysics Data System (ADS)

Ford, David A.; van der Molen, Johan; Hyder, Kieran; Bacon, John; Barciela, Rosa; Creach, Veronique; McEwan, Robert; Ruardij, Piet; Forster, Rodney

2017-03-01

Phytoplankton form the base of the marine food chain, and knowledge of phytoplankton community structure is fundamental when assessing marine biodiversity. Policy makers and other users require information on marine biodiversity and other aspects of the marine environment for the North Sea, a highly productive European shelf sea. This information must come from a combination of observations and models, but currently the coastal ocean is greatly under-sampled for phytoplankton data, and outputs of phytoplankton community structure from models are therefore not yet frequently validated. This study presents a novel set of in situ observations of phytoplankton community structure for the North Sea using accessory pigment analysis. The observations allow a good understanding of the patterns of surface phytoplankton biomass and community structure in the North Sea for the observed months of August 2010 and 2011. Two physical-biogeochemical ocean models, the biogeochemical components of which are different variants of the widely used European Regional Seas Ecosystem Model (ERSEM), were then validated against these and other observations. Both models were a good match for sea surface temperature observations, and a reasonable match for remotely sensed ocean colour observations. However, the two models displayed very different phytoplankton community structures, with one better matching the in situ observations than the other. Nonetheless, both models shared some similarities with the observations in terms of spatial features and inter-annual variability. An initial comparison of the formulations and parameterizations of the two models suggests that diversity between the parameter settings of model phytoplankton functional types, along with formulations which promote a greater sensitivity to changes in light and nutrients, is key to capturing the observed phytoplankton community structure. These findings will help inform future model development, which should be coupled with detailed validation studies, in order to help facilitate the wider application of marine biogeochemical modelling to user and policy needs.

Minimum and Maximum Potential Contributions to Future Sea Level Rise from Polar Ice Sheets

NASA Astrophysics Data System (ADS)

Deconto, R. M.; Pollard, D.

2017-12-01

New climate and ice-sheet modeling, calibrated to past changes in sea-level, is painting a stark picture of the future fate of the great polar ice sheets if greenhouse gas emissions continue unabated. This is especially true for Antarctica, where a substantial fraction of the ice sheet rests on bedrock more than 500-meters below sea level. Here, we explore the sensitivity of the polar ice sheets to a warming atmosphere and ocean under a range of future greenhouse gas emissions scenarios. The ice sheet-climate-ocean model used here considers time-evolving changes in surface mass balance and sub-ice oceanic melting, ice deformation, grounding line retreat on reverse-sloped bedrock (Marine Ice Sheet Instability), and newly added processes including hydrofracturing of ice shelves in response to surface meltwater and rain, and structural collapse of thick, marine-terminating ice margins with tall ice-cliff faces (Marine Ice Cliff Instability). The simulations improve on previous work by using 1) improved atmospheric forcing from a Regional Climate Model and 2) a much wider range of model physical parameters within the bounds of modern observations of ice dynamical processes (particularly calving rates) and paleo constraints on past ice-sheet response to warming. Approaches to more precisely define the climatic thresholds capable of triggering rapid and potentially irreversible ice-sheet retreat are also discussed, as is the potential for aggressive mitigation strategies like those discussed at the 2015 Paris Climate Conference (COP21) to substantially reduce the risk of extreme sea-level rise. These results, including physics that consider both ice deformation (creep) and calving (mechanical failure of marine terminating ice) expand on previously estimated limits of maximum rates of future sea level rise based solely on kinematic constraints of glacier flow. At the high end, the new results show the potential for more than 2m of global mean sea level rise by 2100, implying that physically plausible upper limits on future sea-level rise might need to be reconsidered.

Skin Temperature Processes in the Presence of Sea Ice

NASA Astrophysics Data System (ADS)

Brumer, S. E.; Zappa, C. J.; Brown, S.; McGillis, W. R.; Loose, B.

2013-12-01

Monitoring the sea-ice margins of polar oceans and understanding the physical processes at play at the ice-ocean-air interface is essential in the perspective of a changing climate in which we face an accelerated decline of ice caps and sea ice. Remote sensing and in particular InfraRed (IR) imaging offer a unique opportunity not only to observe physical processes at sea-ice margins, but also to measure air-sea exchanges near ice. It permits monitoring ice and ocean temperature variability, and can be used for derivation of surface flow field allowing investigating turbulence and shearing at the ice-ocean interface as well as ocean-atmosphere gas transfer. Here we present experiments conducted with the aim of gaining an insight on how the presence of sea ice affects the momentum exchange between the atmosphere and ocean and investigate turbulence production in the interplay of ice-water shear, convection, waves and wind. A set of over 200 high resolution IR imagery records was taken at the US Army Cold Regions Research and Engineering Laboratory (CRREL, Hanover NH) under varying ice coverage, fan and pump settings. In situ instruments provided air and water temperature, salinity, subsurface currents and wave height. Air side profiling provided environmental parameters such as wind speed, humidity and heat fluxes. The study aims to investigate what can be gained from small-scale high-resolution IR imaging of the ice-ocean-air interface; in particular how sea ice modulates local physics and gas transfer. The relationship between water and ice temperatures with current and wind will be addressed looking at the ocean and ice temperature variance. Various skin temperature and gas transfer parameterizations will be evaluated at ice margins under varying environmental conditions. Furthermore the accuracy of various techniques used to determine surface flow will be assessed from which turbulence statistics will be determined. This will give an insight on how ice presence may affect the dissipation of turbulent kinetic energy.

The Effect of Breaking Waves on CO_2 Air-Sea Fluxes in the Coastal Zone

NASA Astrophysics Data System (ADS)

Gutiérrez-Loza, Lucía; Ocampo-Torres, Francisco J.; García-Nava, Héctor

2018-03-01

The influence of wave-associated parameters controlling turbulent CO_2 fluxes through the air-sea interface is investigated in a coastal region. A full year of high-quality data of direct estimates of air-sea CO_2 fluxes based on eddy-covariance measurements is presented. The study area located in Todos Santos Bay, Baja California, Mexico, is a net sink of CO_2 with a mean flux of -1.3 μmol m^{-2}s^{-1} (-41.6 mol m^{-2}yr^{-1} ). The results of a quantile-regression analysis computed between the CO_2 flux and, (1) wind speed, (2) significant wave height, (3) wave steepness, and (4) water temperature, suggest that the significant wave height is the most correlated parameter with the magnitude of the flux but the behaviour of the relation varies along the probability distribution function, with the slopes of the regression lines presenting both positive and negative values. These results imply that the presence of surface waves in coastal areas is the key factor that promotes the increase of the flux from and into the ocean. Further analysis suggests that the local characteristics of the aqueous and atmospheric layers might determine the direction of the flux.

The Impact of Moisture Intrusions from Lower Latitudes on Arctic Net Surface Radiative Fluxes and Sea Ice Growth in Fall and Winter

NASA Astrophysics Data System (ADS)

Hegyi, B. M.; Taylor, P. C.

2017-12-01

The fall and winter seasons mark an important period in the evolution of Arctic sea ice, where energy is transferred away from the surface to facilitate the cooling of the surface and the growth of Arctic sea ice extent and thickness. Climatologically, these seasons are characterized by distinct periods of increased and reduced surface cooling and sea ice growth. Periods of reduced sea ice growth and surface cooling are associated with cloudy conditions and the transport of warm and moist air from lower latitudes, termed moisture intrusions. In the research presented, we explore the regional and Arctic-wide impact of moisture intrusions on the surface net radiative fluxes and sea ice growth for each fall and winter season from 2000/01-2015/16, utilizing MERRA2 reanalysis data, PIOMAS sea ice thickness data, and daily CERES radiative flux data. Consistent with previous studies, we find that positive anomalies in downwelling longwave surface flux are associated with increased temperature and water vapor content in the atmospheric column contained within the moisture intrusions. Interestingly, there are periods of increased downwelling LW flux anomalies that persist for one week or longer (i.e. longer than synoptic timescales) that are associated with persistent poleward flux of warm, moist air from lower latitudes. These persistent anomalies significantly reduce the regional growth of Arctic sea ice, and may in part explain the interannual variability of fall and winter Arctic sea ice growth.

Fundamentals of in Situ Digital Camera Methodology for Water Quality Monitoring of Coast and Ocean

PubMed Central

Goddijn-Murphy, Lonneke; Dailloux, Damien; White, Martin; Bowers, Dave

2009-01-01

Conventional digital cameras, the Nikon Coolpix885® and the SeaLife ECOshot®, were used as in situ optical instruments for water quality monitoring. Measured response spectra showed that these digital cameras are basically three-band radiometers. The response values in the red, green and blue bands, quantified by RGB values of digital images of the water surface, were comparable to measurements of irradiance levels at red, green and cyan/blue wavelengths of water leaving light. Different systems were deployed to capture upwelling light from below the surface, while eliminating direct surface reflection. Relationships between RGB ratios of water surface images, and water quality parameters were found to be consistent with previous measurements using more traditional narrow-band radiometers. This current paper focuses on the method that was used to acquire digital images, derive RGB values and relate measurements to water quality parameters. Field measurements were obtained in Galway Bay, Ireland, and in the Southern Rockall Trough in the North Atlantic, where both yellow substance and chlorophyll concentrations were successfully assessed using the digital camera method. PMID:22346729

An ocean scatter propagation model for aeronautical satellite communication applications

NASA Technical Reports Server (NTRS)

Moreland, K. W.

1990-01-01

In this paper an ocean scattering propagation model, developed for aircraft-to-satellite (aeronautical) applications, is described. The purpose of the propagation model is to characterize the behavior of sea reflected multipath as a function of physical propagation path parameters. An accurate validation against the theoretical far field solution for a perfectly conducting sinusoidal surface is provided. Simulation results for typical L band aeronautical applications with low complexity antennas are presented.

The Summer Monsoon of 1987.

NASA Astrophysics Data System (ADS)

Krishnamurti, T. N.; Bedi, H. S.; Subramaniam, M.

1989-04-01

In this paper we have examined the evolution of a number of parameters we believe were important for our understanding of the drought over India during the summer of 1987. The list of parameters includes monthly means or anomalies of the following fields: sea surface temperatures, divergent circulations, outgoing longwave radiation, streamfunction of the lower and upper troposphere, and monthly precipitation (expressed as a percentage departure from a long-term mean). The El Niño related warm sea surface temperature anomaly and a weaker warm sea surface temperature anomaly over the equatorial Indian Ocean provide sustained convection, as reflected by the negative values of the outgoing longwave radiation. With the seasonal heating, a pronounced planetary-scale divergent circulation evolved with a center along the western Pacific Ocean. The monsoonal divergent circulation merged with that related to the El Niño, maintaining most of the heavy rainfall activity between the equatorial Pacific Ocean and east Asia. Persistent convective activity continued south of India during the entire monsoon season. Strong Hadley type overturnings with rising motions over these warm SST anomaly regions and descent roughly near 20° to 25°S was evident as early as April 1987. The subtropical high pressure areas near 20° to 25°S showed stronger than normal circulations. This was revealed by the presence of a counterclockwise streamfunction anomaly at 850 mb during April 1987. With the seasonal heating, this anomaly moved northwards and was located over the Arabian Sea and India. This countermonsoon circulation anomaly at the low levels was associated with a weaker than normal Somali jet and Arabian Sea circulation throughout this summer. The monsoon remained active along northeast India, Bangladesh, northern lndochina, and central China during the summer monsoon season. This was related to the eastward shift of the divergent circulation. An eastward shift of the upper tropospheric anticyclone bell near 25° to 30°N resulted in the continued presence of a westerly wind anomaly north of India. The westerly winds brought in very dry air over the tropical upper troposphere. The dry air penetrated eastwards to central Uttar Pradesh and this seemed to have a major role in inhibiting organized deep convection over most of central, northern and western parts of the Indian subcontinent. The westward extension of the planetary-scale divergent circulation over North and South Africa and the continued drought over the regions are also briefly addressed.

Quantifying uncertainty and sensitivity in sea ice models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Urrego Blanco, Jorge Rolando; Hunke, Elizabeth Clare; Urban, Nathan Mark

The Los Alamos Sea Ice model has a number of input parameters for which accurate values are not always well established. We conduct a variance-based sensitivity analysis of hemispheric sea ice properties to 39 input parameters. The method accounts for non-linear and non-additive effects in the model.

Minimal nuclear energy density functional

NASA Astrophysics Data System (ADS)

Bulgac, Aurel; Forbes, Michael McNeil; Jin, Shi; Perez, Rodrigo Navarro; Schunck, Nicolas

2018-04-01

We present a minimal nuclear energy density functional (NEDF) called "SeaLL1" that has the smallest number of possible phenomenological parameters to date. SeaLL1 is defined by seven significant phenomenological parameters, each related to a specific nuclear property. It describes the nuclear masses of even-even nuclei with a mean energy error of 0.97 MeV and a standard deviation of 1.46 MeV , two-neutron and two-proton separation energies with rms errors of 0.69 MeV and 0.59 MeV respectively, and the charge radii of 345 even-even nuclei with a mean error ɛr=0.022 fm and a standard deviation σr=0.025 fm . SeaLL1 incorporates constraints on the equation of state (EoS) of pure neutron matter from quantum Monte Carlo calculations with chiral effective field theory two-body (NN ) interactions at the next-to-next-to-next-to leading order (N3LO) level and three-body (NNN ) interactions at the next-to-next-to leading order (N2LO) level. Two of the seven parameters are related to the saturation density and the energy per particle of the homogeneous symmetric nuclear matter, one is related to the nuclear surface tension, two are related to the symmetry energy and its density dependence, one is related to the strength of the spin-orbit interaction, and one is the coupling constant of the pairing interaction. We identify additional phenomenological parameters that have little effect on ground-state properties but can be used to fine-tune features such as the Thomas-Reiche-Kuhn sum rule, the excitation energy of the giant dipole and Gamow-Teller resonances, the static dipole electric polarizability, and the neutron skin thickness.

Minimal nuclear energy density functional

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bulgac, Aurel; Forbes, Michael McNeil; Jin, Shi

Inmore » this paper, we present a minimal nuclear energy density functional (NEDF) called “SeaLL1” that has the smallest number of possible phenomenological parameters to date. SeaLL1 is defined by seven significant phenomenological parameters, each related to a specific nuclear property. It describes the nuclear masses of even-even nuclei with a mean energy error of 0.97 MeV and a standard deviation of 1.46 MeV , two-neutron and two-proton separation energies with rms errors of 0.69 MeV and 0.59 MeV respectively, and the charge radii of 345 even-even nuclei with a mean error ε r = 0.022 fm and a standard deviation σ r = 0.025 fm . SeaLL1 incorporates constraints on the equation of state (EoS) of pure neutron matter from quantum Monte Carlo calculations with chiral effective field theory two-body ( NN ) interactions at the next-to-next-to-next-to leading order (N3LO) level and three-body ( NNN ) interactions at the next-to-next-to leading order (N2LO) level. Two of the seven parameters are related to the saturation density and the energy per particle of the homogeneous symmetric nuclear matter, one is related to the nuclear surface tension, two are related to the symmetry energy and its density dependence, one is related to the strength of the spin-orbit interaction, and one is the coupling constant of the pairing interaction. Finally, we identify additional phenomenological parameters that have little effect on ground-state properties but can be used to fine-tune features such as the Thomas-Reiche-Kuhn sum rule, the excitation energy of the giant dipole and Gamow-Teller resonances, the static dipole electric polarizability, and the neutron skin thickness.« less

Minimal nuclear energy density functional

DOE PAGES

Bulgac, Aurel; Forbes, Michael McNeil; Jin, Shi; ...

2018-04-17

Inmore » this paper, we present a minimal nuclear energy density functional (NEDF) called “SeaLL1” that has the smallest number of possible phenomenological parameters to date. SeaLL1 is defined by seven significant phenomenological parameters, each related to a specific nuclear property. It describes the nuclear masses of even-even nuclei with a mean energy error of 0.97 MeV and a standard deviation of 1.46 MeV , two-neutron and two-proton separation energies with rms errors of 0.69 MeV and 0.59 MeV respectively, and the charge radii of 345 even-even nuclei with a mean error ε r = 0.022 fm and a standard deviation σ r = 0.025 fm . SeaLL1 incorporates constraints on the equation of state (EoS) of pure neutron matter from quantum Monte Carlo calculations with chiral effective field theory two-body ( NN ) interactions at the next-to-next-to-next-to leading order (N3LO) level and three-body ( NNN ) interactions at the next-to-next-to leading order (N2LO) level. Two of the seven parameters are related to the saturation density and the energy per particle of the homogeneous symmetric nuclear matter, one is related to the nuclear surface tension, two are related to the symmetry energy and its density dependence, one is related to the strength of the spin-orbit interaction, and one is the coupling constant of the pairing interaction. Finally, we identify additional phenomenological parameters that have little effect on ground-state properties but can be used to fine-tune features such as the Thomas-Reiche-Kuhn sum rule, the excitation energy of the giant dipole and Gamow-Teller resonances, the static dipole electric polarizability, and the neutron skin thickness.« less

On The Computation Of The Best-fit Okada-type Tsunami Source

NASA Astrophysics Data System (ADS)

Miranda, J. M. A.; Luis, J. M. F.; Baptista, M. A.

2017-12-01

The forward simulation of earthquake-induced tsunamis usually assumes that the initial sea surface elevation mimics the co-seismic deformation of the ocean bottom described by a simple "Okada-type" source (rectangular fault with constant slip in a homogeneous elastic half space). This approach is highly effective, in particular in far-field conditions. With this assumption, and a given set of tsunami waveforms recorded by deep sea pressure sensors and (or) coastal tide stations it is possible to deduce the set of parameters of the Okada-type solution that best fits a set of sea level observations. To do this, we build a "space of possible tsunami sources-solution space". Each solution consists of a combination of parameters: earthquake magnitude, length, width, slip, depth and angles - strike, rake, and dip. To constrain the number of possible solutions we use the earthquake parameters defined by seismology and establish a range of possible values for each parameter. We select the "best Okada source" by comparison of the results of direct tsunami modeling using the solution space of tsunami sources. However, direct tsunami modeling is a time-consuming process for the whole solution space. To overcome this problem, we use a precomputed database of Empirical Green Functions to compute the tsunami waveforms resulting from unit water sources and search which one best matches the observations. In this study, we use as a test case the Solomon Islands tsunami of 6 February 2013 caused by a magnitude 8.0 earthquake. The "best Okada" source is the solution that best matches the tsunami recorded at six DART stations in the area. We discuss the differences between the initial seismic solution and the final one obtained from tsunami data This publication received funding of FCT-project UID/GEO/50019/2013-Instituto Dom Luiz.

Copper in the sediment and sea surface microlayer near a fallowed, open-net fish farm.

PubMed

Loucks, Ronald H; Smith, Ruth E; Fisher, Clyde V; Fisher, E Brian

2012-09-01

Sediment and sea surface microlayer samples near an open-net salmon farm in Nova Scotia, were analysed for copper. Copper is a constituent of the feed and is an active ingredient of anti-foulants. The salmon farm was placed in fallow after 15 years of production. Sampling was pursued over 27 months. Elevated copper concentrations in the sediments indicated the farm site as a source. Bubble flotation due to gas-emitting sediments from eutrophication is a likely process for accumulating copper in the sea surface microlayer at enriched concentrations. Elevated and enriched concentrations in the sea surface microlayer over distance from the farm site led, as a result of wind-drift, to an enlarged farm footprint. The levels of copper in both sediments and sea surface microlayer exceeded guidelines for protection of marine life. Over the 27 months period, copper levels persisted in the sediments and decreased gradually in the sea surface microlayer. Copyright © 2012 Elsevier Ltd. All rights reserved.

Radar sea reflection for low-e targets

NASA Astrophysics Data System (ADS)

Chow, Winston C.; Groves, Gordon W.

1998-09-01

Modeling radar signal reflection from a wavy sea surface uses a realistic characteristic of the large surface features and parameterizes the effect of the small roughness elements. Representation of the reflection coefficient at each point of the sea surface as a function of the Specular Deviation Angle is, to our knowledge, a novel approach. The objective is to achieve enough simplification and retain enough fidelity to obtain a practical multipath model. The 'specular deviation angle' as used in this investigation is defined and explained. Being a function of the sea elevations, which are stochastic in nature, this quantity is also random and has a probability density function. This density function depends on the relative geometry of the antenna and target positions, and together with the beam- broadening effect of the small surface ripples determined the reflectivity of the sea surface at each point. The probability density function of the specular deviation angle is derived. The distribution of the specular deviation angel as function of position on the mean sea surface is described.

Sun-stirred Kraken Mare: Circulation in Titan's seas induced by solar heating and methane precipitation

NASA Astrophysics Data System (ADS)

Tokano, T.; Lorenz, R. D.

2015-10-01

Density-driven circulation in Titan's seas forced by solar heating and methane evaporation/precipitation is simulated by an ocean circulation model. If the sea is transparent to sunlight, solar heating can induce anti-clockwise gyres near the sea surface and clockwise gyres near the sea bottom. The gyres are in geostrophic balance between the radially symmetric pressure gradient force and Coriolis force. If instead the sea is turbid and most sunlight is absorbed near the sea surface, the sea gets stratified in warm seasons and the circulation remains weak. Strong summer precipitation at high latitudes causes compositional stratification and increase of the nearsurface methane mole fraction towards the north pole. The resultant latitudinal density contrast drives a meridional overturning with equatorward currents near the sea surface and poleward currents near the sea bottom. Weak precipitation induces gyres rather than meridional overturning.

Real-Time Ocean Prediction System for the East Coast of India

NASA Astrophysics Data System (ADS)

Warrior, H. V.

2016-02-01

The primary objective of the research work reported in this abstract was to develop a Realtime Environmental model for Ocean Dispersion and Impact (as part of an already in-place Decision Support System) for the purpose of radiological safety for the area along Kalpakkam (East Indian) coast. This system involves combining real-time ocean observations with numerical models of ocean processes to provide hindcasts, nowcasts and forecasts of currents, tides and waves. In this work we present the development of an Automated Coupled Atmospheric - Ocean Model (we call it IIT-CAOM) used to forecast the sea surface currents, sea surface temperature (SST) and salinity etc of the Bay of Bengal region under the influence of transient and unsteady atmospheric conditions. This method uses a coupling of Atmosphere and Ocean model. The models used here are the WRF for atmospheric simulations and POM for the ocean counterpart. It has a 3 km X 3 km resolution. This Coupled Model uses GFS (Global Forecast System) Data or FNL (Final Analyses) Data as initial conditions for jump-starting the atmospheric model. The Atmospheric model is run first thus extracting air temperature, wind speed and relative humidity. The heat flux subroutine computes the net heat flux, using above mentioned parameters data. The net heat flux feeds to the ocean model by simply adding net heat flux subroutine to the ocean model code without changing the model original structure. The online forecast of the IIT-CAOM is currently available in the web. The whole system has been automized and runs without any more manual support. The IIT-CAOM simulations have been carried out for Kalpakkam region, which is located on the East coast of India, about 70 km south of Chennai in Tamilnadu State and a three day forecast of sea surface currents, sea surface temperature (SST) and salinity, etc have been obtained.

RFI and Remote Sensing of the Earth from Space

NASA Technical Reports Server (NTRS)

Le Vine, D. M.; Johnson, J. T.; Piepmeier, J.

2016-01-01

Passive microwave remote sensing of the Earth from space provides information essential for understanding the Earth's environment and its evolution. Parameters such as soil moisture, sea surface temperature and salinity, and profiles of atmospheric temperature and humidity are measured at frequencies determined by the physics (e.g. sensitivity to changes in desired parameters) and by the availability of suitable spectrum free from interference. Interference from manmade sources (radio frequency interference) is an impediment that in many cases limits the potential for accurate measurements from space. A review is presented here of the frequencies employed in passive microwave remote sensing of the Earth from space and the associated experience with RFI.

Low-Frequency Surface Backscattering Strengths Measured in the Critical Sea Test Experiments

DTIC Science & Technology

2017-01-19

Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/7160--17-9702 Low-Frequency Surface Backscattering Strengths Measured in the Critical Sea ...LIMITATION OF ABSTRACT Low-Frequency Surface Backscattering Strengths Measured in the Critical Sea Test Experiments Roger C. Gauss1 and Joseph M...significantly- updated results from 55 broadband SUS SSS measurements in 6 Critical Sea Test (CST) experiments. Since the time of the previously

Experimental Sea Slicks in the Marsen (Maritime Remote Sensing) Exercise.

DTIC Science & Technology

1980-10-30

Experimental slicks with various surface properties were generated in the North Sea as part of the MARSEN (Maritime Remote Sensing ) exercise. The one...with remote sensing instrumentation. Because of the numerous effects of surface films on air-sea interfacial processes, these experiments were designed...information was obtained on the influence of sea surface films on the interpretation of signals received by remote sensing systems. Criteria for the

Senstitivity analysis of horizontal heat and vapor transfer coefficients for a cloud-topped marine boundary layer during cold-air outbreaks. M.S. Thesis

NASA Technical Reports Server (NTRS)

Chang, Y. V.

1986-01-01

The effects of external parameters on the surface heat and vapor fluxes into the marine atmospheric boundary layer (MABL) during cold-air outbreaks are investigated using the numerical model of Stage and Businger (1981a). These fluxes are nondimensionalized using the horizontal heat (g1) and vapor (g2) transfer coefficient method first suggested by Chou and Atlas (1982) and further formulated by Stage (1983a). In order to simplify the problem, the boundary layer is assumed to be well mixed and horizontally homogeneous, and to have linear shoreline soundings of equivalent potential temperature and mixing ratio. Modifications of initial surface flux estimates, time step limitation, and termination conditions are made to the MABL model to obtain accurate computations. The dependence of g1 and g2 in the cloud topped boundary layer on the external parameters (wind speed, divergence, sea surface temperature, radiative sky temperature, cloud top radiation cooling, and initial shoreline soundings of temperature, and mixing ratio) is studied by a sensitivity analysis, which shows that the uncertainties of horizontal transfer coefficients caused by changes in the parameters are reasonably small.

The vertical correction of point cloud strips performed over the coastal zone of changing sea level

NASA Astrophysics Data System (ADS)

Gasińska-Kolyszko, Ewa; Furmańczyk, Kazimierz

2017-10-01

The main principle of LIDAR is to measure the accurate time of the laser pulses sent from the system to the target surface. In the operation, laser pulses gradually scan the water surface and in combination with aircraft speed they should perform almost simultaneous soundings of each strip. Vectors sent from aircraft to the Sea are linked to the position of the aircraft. Coordinates of the points - X, Y, Z, are calculated at the time of each measurement. LIDAR crosses the surface of the sea while other impulses pass through the water column and, depending on the depth of the water, reflect from the seabed. Optical receiver on board of the aircraft detects pulse reflections from the seabed and sea surface. On the tidal water basins lidar strips must be adjusted by the changes in sea level. The operation should be reduced to a few hours during low water level. Typically, a surface of 20 to 30 km2 should be covered in an hour. The Baltic Sea is an inland sea, and the surveyed area is located in its South - western part, where meteorological and hydrological conditions affect the sea level changes in a short period of time. A lidar measurement of sea surface, that was done within 2 days, in the coastal zone of the Baltic Sea and the sea level measured 6 times a day at 8, 12, 16, 20, 00, 04 by a water gauge located in the port of Dziwnów (Poland) were used for this study. On the basis of the lidar data, strips were compared with each other. Calculation of time measurement was made for each single line separately. Profiles showing the variability of sea level for each neighboring and overlapping strips were generated. Differences were calculated changes in sea level were identified and on such basis, an adjustment was possible to perform. Microstation software and terrasolid application were used during the research. The latter allowed automatically and manual classification of the point cloud. A sea surface class was distinguished that way. Point cloud was adjusted to flight lines in terms of time and then compared.

Mixed Layer Temperature Budget for the Northward Propagating Summer Monsoon Intraseasonal Oscillation (MISO) in the Central Bay of Bengal

NASA Astrophysics Data System (ADS)

Girishkumar, M. S.; Joseph, J.; Thangaprakash, V. P.; Pottapinjara, V.; McPhaden, M. J.

2017-11-01

Composite analyses of mixed layer temperature (MLT) budget terms from near-surface meteorological and oceanic observations in the central Bay of Bengal are utilized to evaluate the modulation of air-sea interactions and MLT processes in response to the summer monsoon intraseasonal oscillation (MISO). For this purpose, we use moored buoy data at 15°N, 12°N, and 8°N along 90°E together with TropFlux meteorological parameters and the Ocean Surface Current Analyses Real-time (OSCAR) current product. Our analysis shows a strong cooling tendency in MLT with maximum amplitude in the central and northern BoB during the northward propagation of enhanced convective activity associated with the active phase of the MISO; conversely, warming occurs during the suppressed phase of the MISO. The surface mixed layer is generally heated during convectively inactive phases of the MISO primarily due to increased net surface heat flux into the ocean. During convectively active MISO phases, the surface mixed layer is cooled by the combined influence of net surface heat loss to the atmosphere and entrainment cooling at the base of mixed layer. The variability of net surface heat flux is primarily due to modulation of latent heat flux and shortwave radiation. Shortwave is mostly controlled by an enhancement or reduction of cloudiness during the active and inactive MISO phases and latent heat flux is mostly controlled by variations in air-sea humidity difference.

Estimating the time of melt onset and freeze onset over Arctic sea-ice area using active and passive microwave data

USGS Publications Warehouse

Belchansky, Gennady I.; Douglas, David C.; Mordvintsev, Ilia N.; Platonov, Nikita G.

2004-01-01

Accurate calculation of the time of melt onset, freeze onset, and melt duration over Arctic sea-ice area is crucial for climate and global change studies because it affects accuracy of surface energy balance estimates. This comparative study evaluates several methods used to estimate sea-ice melt and freeze onset dates: (1) the melt onset database derived from SSM/I passive microwave brightness temperatures (Tbs) using Drobot and Anderson's [J. Geophys. Res. 106 (2001) 24033] Advanced Horizontal Range Algorithm (AHRA) and distributed by the National Snow and Ice Data Center (NSIDC); (2) the International Arctic Buoy Program/Polar Exchange at the Sea (IABP/POLES) surface air temperatures (SATs); (3) an elaborated version of the AHRA that uses IABP/POLES to avoid anomalous results (Passive Microwave and Surface Temperature Analysis [PMSTA]); (4) another elaborated version of the AHRA that uses Tb variance to avoid anomalous results (Mean Differences and Standard Deviation Analysis [MDSDA]); (5) Smith's [J. Geophys. Res. 103 (1998) 27753] vertically polarized Tb algorithm for estimating melt onset in multiyear (MY) ice (SSM/I 19V–37V); and (6) analyses of concurrent backscattering cross section (σ°) and brightness temperature (Tb) from OKEAN-01 satellite series. Melt onset and freeze onset maps were created and compared to understand how the estimates vary between different satellite instruments and methods over different Arctic sea-ice regions. Comparisons were made to evaluate relative sensitivities among the methods to slight adjustments of the Tbcalibration coefficients and algorithm threshold values. Compared to the PMSTA method, the AHRA method tended to estimate significantly earlier melt dates, likely caused by the AHRA's susceptibility to prematurely identify melt onset conditions. In contrast, the IABP/POLES surface air temperature data tended to estimate later melt and earlier freeze in all but perennial ice. The MDSDA method was least sensitive to small adjustments of the SMMR–SSM/I inter-satellite calibration coefficients. Differences among methods varied by latitude. Freeze onset dates among methods were most disparate in southern latitudes, and tended to converge northward. Surface air temperatures (IABP/POLES) indicated freeze onset well before the MDSDA method, especially in southern peripheral seas, while PMSTA freeze estimates were generally intermediate. Surface air temperature data estimated latest melt onset dates in southern latitudes, but earliest melt onset in northern latitudes. The PMSTA estimated earliest melt onset dates in southern regions, and converged with the MDSDA northward. Because sea-ice melt and freeze are dynamical transitional processes, differences among these methods are associated with differing sensitivities to changing stages of environmental and physical development. These studies contribute to the growing body of documentation about the levels of disparity obtained when Arctic seasonal transition parameters are estimated using various types of microwave data and algorithms.

Establishment of borehole observation system and high resolution seismic studies in the western part of the main Marmara Fault in the frame of MARSite Project

NASA Astrophysics Data System (ADS)

Ozel, A.; Yalcinkaya, E.; Guralp, C. M.; Tunc, S.; Meral Ozel, N.

2013-12-01

The main objective of this study is to install a multi-parameter borehole system and surface array as close to the main Marmara Fault (MMF) in the western Marmara Sea as possible, and measure continuously the evolution of the state of the fault zone surrounding the MMF and to detect any anomaly or change which may occur before earthquakes by making use of the data from the arrays already running in the eastern part of the Marmara Sea. The multi-parameter borehole system will be composed of very wide dynamic range and stable borehole (VBB) broad band seismic sensor, and incorporate 3-D strain meter, tilt meter, and temperature and local hydrostatic pressure measuring devices. The borehole seismic station will use the latest update technologies and design ideas to record 'Earth tides' signals to the smallest magnitude -3 events. Bringing face to face the seismograms of microearthquakes recorded by borehole and surface instruments portrays quite different contents. The shorter recording duration and nearly flat frequency spectrum up to the Nyquist frequencies of borehole records are faced with longer recording duration and rapid decay of spectral amplitudes at higher frequencies of a surface seismogram. The main causative of the observed differences are near surface geology effects that mask most of the source related information the seismograms include, and that give rise to scattering, generating longer duration seismograms. In view of these circumstances, studies on microearthquakes employing surface seismograms may bring on misleading results. Particularly, the works on earthquake physics and nucleation process of earthquakes requires elaborate analysis of tiny events. It is obvious from the studies on the nucleation process of the 1999 earthquake that tens of minutes before the major rupture initiate noteworthy microearthquake activity happened. The starting point of the 1999 rupture was a site of swarm activity noticed a few decades prior the main shock. Nowadays, analogous case is probable in western Marmara Sea region, prone to a major event in near future where the seismic activity is prevailing along the impending rupture zone. Deploying a borehole system eastern end of the Ganos fault zone may yield invaluable data to closely inspect and monitor the last stages of the preparation stage of major rupture. Keywords: Borehole seismometer; Ganos fault; microearthquakes; western Marmara

Seasonal and Interannual Variation of Currents and Water Properties off the Mid-East Coast of Korea

NASA Astrophysics Data System (ADS)

Park, J. H.; Chang, K. I.; Nam, S.

2016-02-01

Since 1999, physical parameters such as current, temperature, and salinity off the mid-east coast of Korea have been continuously observed from the long-term buoy station called `East-Sea Real-time Ocean monitoring Buoy (ESROB)'. Applying harmonic analysis to 6-year-long (2007-2012) depth-averaged current data from the ESROB, a mean seasonal cycle of alongshore currents, characterized by poleward current in average and equatorward current in summer, is extracted which accounts for 5.8% of the variance of 40 hours low-pass filtered currents. In spite of the small variance explained, a robust seasonality of summertime equatorward reversal typifies the low-passed alongshore currents along with low-density water. To reveal the dynamics underlying the seasonal variation, each term of linearized, depth-averaged momentum equations is estimated using the data from ESROB, adjacent tide gauge stations, and serial hydrographic stations. The result indicates that the reversal of alongshore pressure gradient is a major driver of the equatorward reversals in summer. The reanalysis wind product (MERRA) and satellite altimeter-derived sea surface height (AVISO) data show correlated features between positive (negative) wind stress curl and sea surface depression (uplift). Quantitative estimates reveal that the wind-stress curl accounts for 42% of alongshore sea level variation. Summertime low-density water originating from the northern coastal region is a footprint of the buoyancy-driven equatorward current. An interannual variation (anomalies from the mean seasonal cycle) of alongshore currents and its possible driving mechanisms will be discussed.

Modelling dengue fever risk in the State of Yucatan, Mexico using regional-scale satellite-derived sea surface temperature.

PubMed

Laureano-Rosario, Abdiel E; Garcia-Rejon, Julian E; Gomez-Carro, Salvador; Farfan-Ale, Jose A; Muller-Karger, Frank E

2017-08-01

Accurately predicting vector-borne diseases, such as dengue fever, is essential for communities worldwide. Changes in environmental parameters such as precipitation, air temperature, and humidity are known to influence dengue fever dynamics. Furthermore, previous studies have shown how oceanographic variables, such as El Niño Southern Oscillation (ENSO)-related sea surface temperature from the Pacific Ocean, influences dengue fever in the Americas. However, literature is lacking on the use of regional-scale satellite-derived sea surface temperature (SST) to assess its relationship with dengue fever in coastal areas. Data on confirmed dengue cases, demographics, precipitation, and air temperature were collected. Incidence of weekly dengue cases was examined. Stepwise multiple regression analyses (AIC model selection) were used to assess which environmental variables best explained increased dengue incidence rates. SST, minimum air temperature, precipitation, and humidity substantially explained 42% of the observed variation (r 2 =0.42). Infectious diseases are characterized by the influence of past cases on current cases and results show that previous dengue cases alone explained 89% of the variation. Ordinary least-squares analyses showed a positive trend of 0.20±0.03°C in SST from 2006 to 2015. An important element of this study is to help develop strategic recommendations for public health officials in Mexico by providing a simple early warning capability for dengue incidence. Copyright © 2017 Elsevier B.V. All rights reserved.

Ensemble assimilation of ARGO temperature profile, sea surface temperature, and altimetric satellite data into an eddy permitting primitive equation model of the North Atlantic Ocean

NASA Astrophysics Data System (ADS)

Yan, Y.; Barth, A.; Beckers, J. M.; Candille, G.; Brankart, J. M.; Brasseur, P.

2015-07-01

Sea surface height, sea surface temperature, and temperature profiles at depth collected between January and December 2005 are assimilated into a realistic eddy permitting primitive equation model of the North Atlantic Ocean using the Ensemble Kalman Filter. Sixty ensemble members are generated by adding realistic noise to the forcing parameters related to the temperature. The ensemble is diagnosed and validated by comparison between the ensemble spread and the model/observation difference, as well as by rank histogram before the assimilation experiments. An incremental analysis update scheme is applied in order to reduce spurious oscillations due to the model state correction. The results of the assimilation are assessed according to both deterministic and probabilistic metrics with independent/semiindependent observations. For deterministic validation, the ensemble means, together with the ensemble spreads are compared to the observations, in order to diagnose the ensemble distribution properties in a deterministic way. For probabilistic validation, the continuous ranked probability score (CRPS) is used to evaluate the ensemble forecast system according to reliability and resolution. The reliability is further decomposed into bias and dispersion by the reduced centered random variable (RCRV) score in order to investigate the reliability properties of the ensemble forecast system. The improvement of the assimilation is demonstrated using these validation metrics. Finally, the deterministic validation and the probabilistic validation are analyzed jointly. The consistency and complementarity between both validations are highlighted.

Forecasting decadal changes in sea surface temperatures and coral bleaching within a Caribbean coral reef

NASA Astrophysics Data System (ADS)

Li, Angang; Reidenbach, Matthew A.

2014-09-01

Elevated sea surface temperature (SST) caused by global warming is one of the major threats to coral reefs. While increased SST has been shown to negatively affect the health of coral reefs by increasing rates of coral bleaching, how changes to atmospheric heating impact SST distributions, modified by local flow environments, has been less understood. This study aimed to simulate future water flow patterns and water surface heating in response to increased air temperature within a coral reef system in Bocas del Toro, Panama, located within the Caribbean Sea. Water flow and SST were modeled using the Delft3D-FLOWcomputer simulation package. Locally measured physical parameters, including bathymetry, astronomic tidal forcing, and coral habitat distribution were input into the model and water flow, and SST was simulated over a four-month period under present day, as well as projected warming scenarios in 2020s, 2050s, and 2080s. Changes in SST, and hence the thermal stress to corals, were quantified by degree heating weeks. Results showed that present-day reported bleaching sites were consistent with localized regions of continuous high SST. Regions with highest SST were located within shallow coastal sites adjacent to the mainland or within the interior of the bay, and characterized by low currents with high water retention times. Under projected increases in SSTs, shallow reef areas in low flow regions were found to be hot spots for future bleaching.

Temporal variability and climatology of hydrodynamic, water property and water quality parameters in the West Johor Strait of Singapore.

PubMed

Behera, Manasa Ranjan; Chun, Cui; Palani, Sundarambal; Tkalich, Pavel

2013-12-15

The study presents a baseline variability and climatology study of measured hydrodynamic, water properties and some water quality parameters of West Johor Strait, Singapore at hourly-to-seasonal scales to uncover their dependency and correlation to one or more drivers. The considered parameters include, but not limited by sea surface elevation, current magnitude and direction, solar radiation and air temperature, water temperature, salinity, chlorophyll-a and turbidity. FFT (Fast Fourier Transform) analysis is carried out for the parameters to delineate relative effect of tidal and weather drivers. The group and individual correlations between the parameters are obtained by principal component analysis (PCA) and cross-correlation (CC) technique, respectively. The CC technique also identifies the dependency and time lag between driving natural forces and dependent water property and water quality parameters. The temporal variability and climatology of the driving forces and the dependent parameters are established at the hourly, daily, fortnightly and seasonal scales. Copyright © 2013 Elsevier Ltd. All rights reserved.

Resilience of Key Biological Parameters of the Senegalese Flat Sardinella to Overfishing and Climate Change.

PubMed

Ba, Kamarel; Thiaw, Modou; Lazar, Najih; Sarr, Alassane; Brochier, Timothée; Ndiaye, Ismaïla; Faye, Alioune; Sadio, Oumar; Panfili, Jacques; Thiaw, Omar Thiom; Brehmer, Patrice

2016-01-01

The stock of the Senegalese flat sardinella, Sardinella maderensis, is highly exploited in Senegal, West Africa. Its growth and reproduction parameters are key biological indicators for improving fisheries management. This study reviewed these parameters using landing data from small-scale fisheries in Senegal and literature information dated back more than 25 years. Age was estimated using length-frequency data to calculate growth parameters and assess the growth performance index. With global climate change there has been an increase in the average sea surface temperature along the Senegalese coast but the length-weight parameters, sex ratio, size at first sexual maturity, period of reproduction and condition factor of S. maderensis have not changed significantly. The above parameters of S. maderensis have hardly changed, despite high exploitation and fluctuations in environmental conditions that affect the early development phases of small pelagic fish in West Africa. This lack of plasticity of the species regarding of the biological parameters studied should be considered when planning relevant fishery management plans.

Uncertainty Quantification and Sensitivity Analysis in the CICE v5.1 Sea Ice Model

NASA Astrophysics Data System (ADS)

Urrego-Blanco, J. R.; Urban, N. M.

2015-12-01

Changes in the high latitude climate system have the potential to affect global climate through feedbacks with the atmosphere and connections with mid latitudes. Sea ice and climate models used to understand these changes have uncertainties that need to be characterized and quantified. In this work we characterize parametric uncertainty in Los Alamos Sea Ice model (CICE) and quantify the sensitivity of sea ice area, extent and volume with respect to uncertainty in about 40 individual model parameters. Unlike common sensitivity analyses conducted in previous studies where parameters are varied one-at-a-time, this study uses a global variance-based approach in which Sobol sequences are used to efficiently sample the full 40-dimensional parameter space. This approach requires a very large number of model evaluations, which are expensive to run. A more computationally efficient approach is implemented by training and cross-validating a surrogate (emulator) of the sea ice model with model output from 400 model runs. The emulator is used to make predictions of sea ice extent, area, and volume at several model configurations, which are then used to compute the Sobol sensitivity indices of the 40 parameters. A ranking based on the sensitivity indices indicates that model output is most sensitive to snow parameters such as conductivity and grain size, and the drainage of melt ponds. The main effects and interactions among the most influential parameters are also estimated by a non-parametric regression technique based on generalized additive models. It is recommended research to be prioritized towards more accurately determining these most influential parameters values by observational studies or by improving existing parameterizations in the sea ice model.

A study of the dynamics of droughts in Northern Brazil: Observations, theory, and numerical experiments with a global atmospheric circulation model

NASA Technical Reports Server (NTRS)

Shukla, J.; Moura, A. D.

1980-01-01

The monthly mean sea surface temperature anomalies over tropical Altantic and rainfall anomalies over two selected stations for 25 years (1948-1972) were examined. It is found that the most severe drought events are associated with the simultaneous occurrence of warm sea surface temperature anomalies over north and cold sea surface temperature anomalies over south tropical Atlantic. Simultaneous occurrences of warm sea surface temperature anomaly at 15 deg N, 45 deg W and cold sea surface temperature anomaly at 15 deg S, 5 deg W were always associated with negative anomalies of rainfall, and vice versa. A simple primitive equation model is used to calculate the frictionally controlled and thermally driven circulation due to a prescribed heating function in a resting atmosphere.

Investigation of microwave backscatter from the air-sea interface

NASA Technical Reports Server (NTRS)

Mcintosh, Robert E.; Carswell, James R.

1995-01-01

Monitoring the ocean surface winds and mean ocean surface level is essential for improving our knowledge of the climate. Two instruments that may provide us with this information are satellite-based scatterometers and altimeters. However, these instruments measure the backscatter characteristics of the ocean surface from which other physical parameters, such as the wind speed or ocean surface height, are derived. To improve the algorithms or models that relate the electromagnetic backscatter to the desired physical parameters, the University of Massachusetts (UMass) Microwave Remote Sensing Laboratory (MIRSL) designed and fabricated three airborne scatterometers: a C-band scatterometer (CSCAT), Ku-band scatterometer (KUSCAT) and C/Ku-band scatterometer (EMBR). One or more of these instruments participated in the Electromagnetic Bias experiment (EM Bias), Shelf Edge Exchange Processes experiment (SEEP), Surface Wave Dynamics Experiment (SWADE), Southern Ocean Wave Experiment (SOWEX), Hurricane Tina research flights, Tropical Ocean Global Atmosphere Coupled Ocean-Atmosphere Response Experiment (TOGA COARE), and Ladir In-space Technology Experiment (LITE). This document describes the three scatterometers, summarizes our measurement campaigns and major contributions to the scientific and engineering communities, lists the publications that resulted, and presents the degrees earned under the support of this NASA grant.

Seasonal signatures in SFG vibrational spectra of the sea surface nanolayer at Boknis Eck Time Series Station (SW Baltic Sea)

NASA Astrophysics Data System (ADS)

Laß, K.; Bange, H. W.; Friedrichs, G.

2013-02-01

The very thin sea surface nanolayer on top of the sea surface microlayer, sometimes just one monomolecular layer thick, forms the interface between ocean and atmosphere. Due to the small dimension and tiny amount of substance, knowledge about the development of the layer in the course of the year is scarce. In this work, the sea surface nanolayer at Boknis Eck Time Series Station (BE), southwestern Baltic Sea, has been investigated over a period of three and a half years. Surface water samples were taken monthly by screen sampling and were analyzed in terms of organic content and composition by sum frequency generation spectroscopy, which is specifically sensitive to interfacial layers. A yearly periodicity has been observed with a pronounced abundance of sea surface nanolayer material (such as carbohydrate-rich material) during the summer months. On the basis of our results we conclude that the abundance of organic material in the nanolayer at Boknis Eck is not directly related to phytoplankton abundance. We suggest that indeed sloppy feeding of zooplankton together with photochemical and/or microbial processing of organic precursor compounds are responsible for the pronounced seasonality.

Seasonal signatures in SFG vibrational spectra of the sea surface nanolayer at Boknis Eck Time Series Station (SW Baltic Sea)

NASA Astrophysics Data System (ADS)

Laß, K.; Bange, H. W.; Friedrichs, G.

2013-08-01

The very thin sea surface nanolayer on top of the sea surface microlayer, sometimes just one monomolecular layer thick, forms the interface between ocean and atmosphere. Due to the small dimension and tiny amount of substance, knowledge about the development of the layer in the course of the year is scarce. In this work, the sea surface nanolayer at Boknis Eck Time Series Station (BE), southwestern Baltic Sea, has been investigated over a period of three and a half years. Surface water samples were taken monthly by screen sampling and were analyzed in terms of organic content and composition by sum frequency generation spectroscopy, which is specifically sensitive to interfacial layers. A yearly periodicity has been observed with a pronounced abundance of sea surface nanolayer material (such as carbohydrate-rich material) during the summer months. On the basis of our results we conclude that the abundance of organic material in the nanolayer at Boknis Eck is not directly related to phytoplankton abundance alone. We speculate that indeed sloppy feeding of zooplankton together with photochemical and/or microbial processing of organic precursor compounds is responsible for the pronounced seasonality.

The role of horizontal exchanges on ventilation of the benthic boundary layer on the Black Sea shelf

NASA Astrophysics Data System (ADS)

Shapiro, Georgy; Wobus, Fred

2010-05-01

The state of the benthic component of the shelf ecosystem is strongly influenced by availability of dissolved oxygen. The chemical structure of the Black Sea waters is largely determined by the location and the strength of the pycnocline. Due to similarity in the mechanisms of vertical exchanges the oxycline and the chemocline occur at the same depth intervals as the halocline and pycnocline (Özsoy and Ünlüata, 1997). As the data for dissolved oxygen on the shelf is relatively sparse we assume that much abundant data on physical parameters (temperature and salinity) can be used as proxy in determining the location of the oxycline and hence the spatial extent of near-bottom waters depleted in oxygen. When the waters of the benthic boundary layers below the pycnocline are ‘locked' i.e. unable to mix vertically with surface then the biological pump and supply of oxygen are suppressed. However, the locked water can, in principle, move ‘horizontally', predominantly along the constant density levels and get ventilated via isopycnal exchanges. The isopycnals in the Black Sea have generally a dome-like structure, so that the isopycnal movements across the shelf break can ventilate bottom shelf waters with water masses from upper parts of the water column in the deep sea. We use the intra- and inter-annual variations in the near-bottom temperature as indicators for variability of physical conditions in the benthic boundary layer on the shelf. The physical reason for this is that interannual variations in the near-bottom temperature are directly related with the volume of cold waters (Ivanov et al., 2000) which are formed on the shelf and then exported into the deep sea, so that variations in temperature may indicate changes in the intensity of horizontal exchanges. In this paper we identified areas on the Black Sea margin where bottom waters can not be mixed vertically (‘locked' waters) during the winter months and locations to which the locked waters can move ‘horizontally'. The potential energy approach was used to identify the spatial and temporal variability of the areas and volumes occupied by the locked waters. This approach allows to assess a relative strength of the ability of locked waters to mix vertically with oxygen rich surface waters as compared to ‘horizontal' exchanges with the deep sea along isopycnic surfaces. Analysis of interannual variability of temperature showed that the period 1965-1983 was a warm period when the ‘summer' season ( May to November) temperatures of the benthic waters were higher than the average; to the contrary the period 1983-2001 (i.e. up to end of available data sets) was a cold period. Correlations between various time series of hydrographical and meteorological parameters were calculated to establish the relative importance of vertical versus horizontal exchanges in ventilation of the locked water masses. A low correlation (R=0.24) was obtained between the variation of the winter sea surface temperature on the shelf and the ‘summer' temperatures of locked waters. A higher correlation (R=0.56) was found between the summer temperatures of the Cold Intermediate Waters below the seasonal pycnocline in the deep sea (density range sigma-theta= 14.2-14.8) and the ‘summer' temperatures of the ‘locked' waters in the benthic boundary layer on the shelf. Analysis shows that the isopycnic exchanges with the deep sea are more important for ventilation of the benthic boundary layer on the shelf than winter convection on the shelf itself. This work was made possible via support from EU FP6 SESAME and EU FP7 MyOcean projects and NERC PhD studentship. References Özsoy, E. and Ünlüata, Ü., 1997. Oceanography of the Black Sea: a review of some recent results. Earth-Sci. Rev., 42(4): 231-272. Ivanov, L.I., Belokopytov, V.N., Özsoy, E. and Samodurov, A., 2000. Ventilation of the Black Sea pycnocline on seasonal and interannual time scales. Mediterr. Mar. Sci., 1/2: 61-74.

A Comparison of Sea Ice Type, Sea Ice Temperature, and Snow Thickness Distributions in the Arctic Seasonal Ice Zones with the DMSP SSM/I

NASA Technical Reports Server (NTRS)

St.Germain, Karen; Cavalieri, Donald J.; Markus, Thorsten

1997-01-01

Global climate studies have shown that sea ice is a critical component in the global climate system through its effect on the ocean and atmosphere, and on the earth's radiation balance. Polar energy studies have further shown that the distribution of thin ice and open water largely controls the distribution of surface heat exchange between the ocean and atmosphere within the winter Arctic ice pack. The thickness of the ice, the depth of snow on the ice, and the temperature profile of the snow/ice composite are all important parameters in calculating surface heat fluxes. In recent years, researchers have used various combinations of DMSP SSMI channels to independently estimate the thin ice type (which is related to ice thickness), the thin ice temperature, and the depth of snow on the ice. In each case validation efforts provided encouraging results, but taken individually each algorithm gives only one piece of the information necessary to compute the energy fluxes through the ice and snow. In this paper we present a comparison of the results from each of these algorithms to provide a more comprehensive picture of the seasonal ice zone using passive microwave observations.

Basin-scale observations of isoprene and monoterpenes in the Arctic and Atlantic Oceans

NASA Astrophysics Data System (ADS)

Carpenter, L.; Hackenberg, S.; Andrews, S.; Minaeian, J.; Chance, R.; Arnold, S.; Spracklen, D. V.; Walker, H.; Brewin, R. J.; Tarran, G.; Tilstone, G.; Small, A.; Bouman, H. A.

2016-12-01

We report surface ocean concentrations, atmospheric mixing ratios and calculated sea-to-air fluxes of isoprene and six monoterpenes (α- and β-pinene, myrcene, Δ 3-carene, ocimene, and limonene) spanning approximately 130 degrees of latitude (80 °N- 50 °S) in the Arctic and Atlantic Oceans. Oceanic isoprene concentrations showed covariance with a number of concurrently monitored biological parameters, and these relationships were dependent on sea surface temperatures. Parameterisations of isoprene seawater concentrations based on linear regression analyses of these relationships perform well for Arctic and Atlantic data. Levels of all monoterpenes were generally low, with oceanic concentrations ranging from below the detection limit of <1 pmol L-1 to 5 pmol L-1 . In air, monoterpene mixing ratios varied from below the detection limit ( 1 pptv) to 5 pptv, after careful filtering for ship-related contamination. Unlike in previous studies, no clear trends or relationships of the monoterpenes with biological data were found. Limonene showed generally the highest levels in water (up to 84 pmol L-1 in the Atlantic Ocean) and air; however this was attributed mostly to shipborne contamination. We calculate global sea-air fluxes of isoprene and monoterpenes based on this data and compare to previous estimates.

Faulting, Seismicity and Stress Interaction in the Salton Sea Region of Southern California

NASA Astrophysics Data System (ADS)

Kilb, D. L.; Brothers, D. S.; Lin, G.; Kent, G.; Newman, R. L.; Driscoll, N.

2009-12-01

The Salton Sea region in southern California provides an ideal location to study the relationship between transcurrent and extensional motion in the northern Gulf of California margin, allowing us to investigate the spatial and temporal interaction of faults in the area and better understand their kinematics. In this region, the San Andreas Fault (SAF) and Imperial Fault present two major transform faults separated by the Salton Sea transtensional domain. Earthquakes over magnitude 4 in this area almost always have associated aftershock sequences. Recent seismic reflection surveys in the Salton Sea reveal that the majority of faults under the southern Salton Sea trend ~N15°E, appear normal-dominant and have very minimal associated microseismicity. These normal faults rupture every 100-300 years in large earthquakes and most of the nearby microseismicity locates east of the mapped surface traces. For example, there is profuse microseismicity in the Brawley Seismic Zone (BSZ), which is coincident with the southern terminus of the SAF as it extends offshore into the Salton Sea. Earthquakes in the BSZ are dominantly swarm-like, occurring along short (<5 km) ~N45°E oriented sinistral and N35°W oriented dextral fault planes. This mapped seismicity makes a rung-and-ladder pattern. In an effort to reconcile differences between processes at the surface and those at seismogenic depths we integrate near surface fault kinematics, geometry and paleoseismic history with seismic data. We identify linear and planer trends in these data (20 near surface faults, >20,000 relocated earthquakes and >2,000 earthquake focal mechanisms) and when appropriate estimate the fault strike and dip using principal component analysis. With our more detailed image of the fault structure we assess how static stress changes imparted by magnitude ~6.0 ruptures along N15E oriented normal faults beneath the Salton Sea can modulate the stress field in the BSZ and along the SAF. These tests include exploring sensitivity of the results to parameter uncertainties. In general, we find rupture of the normal faults produces a butterfly pattern of static stress changes on the SAF with decreases along the southernmost portion below latitude 33.3±0.1 and increases on segments above these latitudes. Additionally, simulated ruptures on the normal faults predict optimally oriented sinistral faults that align with the “rungs” in the BSZ and optimally oriented dextral faults that are parallel to the SAF. Given these observations and results, we favor the scenario that normal faults beneath the Salton Sea accommodate most of the strain budget, rupturing as magnitude ~6.0-6.6 events every 100 years or so, and the consequent stress field generated within the relatively weak crust shapes the orientation of the short faults in the BSZ.

Predicting the Turbulent Air-Sea Surface Fluxes, Including Spray Effects, from Weak to Strong Winds

DTIC Science & Technology

2012-09-30

almost complete decoupling of the wind field from the sea surface . As a result of the weak surface stress, the flow becomes almost free from the...shore flow . In turn, wave growth and the associated surface roughness (z0) are limited. Consequently, the stability increases further in a...1 DISTRIBUTION STATEMENT A. Approved for public release; distribution is unlimited. Predicting the Turbulent Air-Sea Surface Fluxes

Low frequency microwave radiometer for N-ROSS

NASA Astrophysics Data System (ADS)

Hollinger, J. P.; Lo, R. C.

1984-01-01

The all weather, global determination of sea surface temperature (SST) has been identified as a requirement needed to support naval operations.The target SST accuracy is + or 1.0 K with a surface resolution of 10 km. Investigations of the phenomenology and technology of remote passive microwave sensing of the ocean environment over the past decade have demonstrated that this objective is presently attainable. Preliminary specification and trade off studies were conducted to define the frequency, polarization, scan geometry, antenna size, and other essential parameters of the low frequency microwave radiometer (LFMR). It will be a meter deployable mesh surface antenna. It is to be flown on the Navy-Remote Ocean Sensing System (N-ROSS) satellite scheduled to be launched in late 1988.

Input Uncertainty and its Implications on Parameter Assessment in Hydrologic and Hydroclimatic Modelling Studies

NASA Astrophysics Data System (ADS)

Chowdhury, S.; Sharma, A.

2005-12-01

Hydrological model inputs are often derived from measurements at point locations taken at discrete time steps. The nature of uncertainty associated with such inputs is thus a function of the quality and number of measurements available in time. A change in these characteristics (such as a change in the number of rain-gauge inputs used to derive spatially averaged rainfall) results in inhomogeneity in the associated distributional profile. Ignoring such uncertainty can lead to models that aim to simulate based on the observed input variable instead of the true measurement, resulting in a biased representation of the underlying system dynamics as well as an increase in both bias and the predictive uncertainty in simulations. This is especially true of cases where the nature of uncertainty likely in the future is significantly different to that in the past. Possible examples include situations where the accuracy of the catchment averaged rainfall has increased substantially due to an increase in the rain-gauge density, or accuracy of climatic observations (such as sea surface temperatures) increased due to the use of more accurate remote sensing technologies. We introduce here a method to ascertain the true value of parameters in the presence of additive uncertainty in model inputs. This method, known as SIMulation EXtrapolation (SIMEX, [Cook, 1994]) operates on the basis of an empirical relationship between parameters and the level of additive input noise (or uncertainty). The method starts with generating a series of alternate realisations of model inputs by artificially adding white noise in increasing multiples of the known error variance. The alternate realisations lead to alternate sets of parameters that are increasingly biased with respect to the truth due to the increased variability in the inputs. Once several such realisations have been drawn, one is able to formulate an empirical relationship between the parameter values and the level of additive noise present. SIMEX is based on theory that the trend in alternate parameters can be extrapolated back to the notional error free zone. We illustrate the utility of SIMEX in a synthetic rainfall-runoff modelling scenario and an application to study the dependence of uncertain distributed sea surface temperature anomalies with an indicator of the El Nino Southern Oscillation, the Southern Oscillation Index (SOI). The errors in rainfall data and its affect is explored using Sacramento rainfall runoff model. The rainfall uncertainty is assumed to be multiplicative and temporally invariant. The model used to relate the sea surface temperature anomalies (SSTA) to the SOI is assumed to be of a linear form. The nature of uncertainty in the SSTA is additive and varies with time. The SIMEX framework allows assessment of the relationship between the error free inputs and response. Cook, J.R., Stefanski, L. A., Simulation-Extrapolation Estimation in Parametric Measurement Error Models, Journal of the American Statistical Association, 89 (428), 1314-1328, 1994.

Potential Elevation Biases for Laser Altimeters from Subsurface Scattered Photons: Laboratory and Model Exploration of Green Light Scattering in Snow

NASA Astrophysics Data System (ADS)

Greeley, A.; Neumann, T.; Markus, T.; Kurtz, N. T.; Cook, W. B.

2015-12-01

Existing visible light laser altimeters such as MABEL (Multiple Altimeter Beam Experimental Lidar) - a single photon counting simulator for ATLAS (Advanced Topographic Laser Altimeter System) on NASA's upcoming ICESat-2 mission - and ATM (Airborne Topographic Mapper) on NASA's Operation IceBridge mission provide scientists a view of Earth's ice sheets, glaciers, and sea ice with unprecedented detail. Precise calibration of these instruments is needed to understand rapidly changing parameters like sea ice freeboard and to measure optical properties of surfaces like snow covered ice sheets using subsurface scattered photons. Photons travelling into snow, ice, or water before scattering back to the altimeter receiving system (subsurface photons) travel farther and longer than photons scattering off the surface only, causing a bias in the measured elevation. We seek to identify subsurface photons in a laboratory setting using a flight-tested laser altimeter (MABEL) and to quantify their effect on surface elevation estimates for laser altimeter systems. We also compare these estimates with previous laboratory measurements of green laser light transmission through snow, as well as Monte Carlo simulations of backscattered photons from snow.

The role of surface and subsurface processes in keeping pace with sea level rise in intertidal wetlands of Moreton Bay, Queensland, Australia

USGS Publications Warehouse

Lovelock, Catherine E.; Bennion, Vicki; Grinham, Alistair; Cahoon, Donald R.

2011-01-01

Increases in the elevation of the soil surfaces of mangroves and salt marshes are key to the maintenance of these habitats with accelerating sea level rise. Understanding the processes that give rise to increases in soil surface elevation provides science for management of landscapes for sustainable coastal wetlands. Here, we tested whether the soil surface elevation of mangroves and salt marshes in Moreton Bay is keeping up with local rates of sea level rise (2.358 mm y-1) and whether accretion on the soil surface was the most important process for keeping up with sea level rise. We found variability in surface elevation gains, with sandy areas in the eastern bay having the highest surface elevation gains in both mangrove and salt marsh (5.9 and 1.9 mm y-1) whereas in the muddier western bay rates of surface elevation gain were lower (1.4 and -0.3 mm y-1 in mangrove and salt marsh, respectively). Both sides of the bay had similar rates of surface accretion (~7–9 mm y-1 in the mangrove and 1–3 mm y-1 in the salt marsh), but mangrove soils in the western bay were subsiding at a rate of approximately 8 mm y-1, possibly due to compaction of organic sediments. Over the study surface elevation increments were sensitive to position in the intertidal zone (higher when lower in the intertidal) and also to variation in mean sea level (higher at high sea level). Although surface accretion was the most important process for keeping up with sea level rise in the eastern bay, subsidence largely negated gains made through surface accretion in the western bay indicating a high vulnerability to sea level rise in these forests.

The impact of land and sea surface variations on the Delaware sea breeze at local scales

NASA Astrophysics Data System (ADS)

Hughes, Christopher P.

The summertime climate of coastal Delaware is greatly influenced by the intensity, frequency, and location of the local sea breeze circulation. Sea breeze induced changes in temperature, humidity, wind speed, and precipitation influence many aspects of Delaware's economy by affecting tourism, farming, air pollution density, energy usage, and the strength, and persistence of Delaware's wind resource. The sea breeze front can develop offshore or along the coastline and often creates a near surface thermal gradient in excess of 5°C. The purpose of this dissertation is to investigate the dynamics of the Delaware sea breeze with a focus on the immediate coastline using observed and modeled components, both at high resolutions (~200m). The Weather Research and Forecasting model (version 3.5) was employed over southern Delaware with 5 domains (4 levels of nesting), with resolutions ranging from 18km to 222m, for June 2013 to investigate the sensitivity of the sea breeze to land and sea surface variations. The land surface was modified in the model to improve the resolution, which led to the addition of land surface along the coastline and accounted for recent urban development. Nine-day composites of satellite sea surface temperatures were ingested into the model and an in-house SST forcing dataset was developed to account for spatial SST variation within the inland bays. Simulations, which include the modified land surface, introduce a distinct secondary atmospheric circulation across the coastline of Rehoboth Bay when synoptic offshore wind flow is weak. Model runs using high spatial- and temporal-resolution satellite sea surface temperatures over the ocean indicate that the sea breeze landfall time is sensitive to the SST when the circulation develops offshore. During the summer of 2013 a field campaign was conducted in the coastal locations of Rehoboth Beach, DE and Cape Henlopen, DE. At each location, a series of eleven small, autonomous thermo-sensors (i-buttons) were placed along 1-km transects oriented perpendicular to the coastline where each sensor recorded temperatures at five-minute intervals. This novel approach allows for detailed characterization of the sea breeze front development over the immediate coastline not seen in previous studies. These observations provide evidence of significant variability in frontal propagation (advancing, stalling, and retrograding) within the first kilometer of the coast. Results from this observational study indicate that the land surface has the largest effect on the frontal location when the synoptic winds have a strong offshore component, which forces the sea breeze front to move slowly through the region. When this happens, the frequency of occurrence and sea breeze frontal speed decreases consistently across the first 500 m of Rehoboth Beach, after which, the differences become insignificant. At Cape Henlopen the decrease in intensity across the transect is much less evident and the reduction in frequency does not occur until after the front is 500 m from the coast. Under these conditions at Rehoboth Beach, the near surface air behind the front warms due to the land surface which, along with the large surface friction component of the urbanized land surface, causes the front to slow as it traverses the region. Observation and modeling results suggest that the influence of variations in the land and sea surface on the sea breeze circulation is complex and highly dependent on the regional synoptic wind regime. This result inspired the development of a sea breeze prediction algorithm using a generalized linear regression model which, incorporated real-time synoptic conditions to forecast the likelihood of a sea breeze front passing through a coastal station. The forecast skill increases through the morning hours after sunrise. The inland synoptic wind direction is the most influential variable utilized by the algorithm. Such a model could be enhanced to forecast local temperature with coonfidence, which could be useful in an economic or energy usage model.

METEOSAT studies of clouds and radiation budget

NASA Technical Reports Server (NTRS)

Saunders, R. W.

1982-01-01

Radiation budget studies of the atmosphere/surface system from Meteosat, cloud parameter determination from space, and sea surface temperature measurements from TIROS N data are all described. This work was carried out on the interactive planetary image processing system (IPIPS), which allows interactive manipulationion of the image data in addition to the conventional computational tasks. The current hardware configuration of IPIPS is shown. The I(2)S is the principal interactive display allowing interaction via a trackball, four buttons under program control, or a touch tablet. Simple image processing operations such as contrast enhancing, pseudocoloring, histogram equalization, and multispectral combinations, can all be executed at the push of a button.

Sea surface mean square slope from Ku-band backscatter data

NASA Technical Reports Server (NTRS)

Jackson, F. C.; Walton, W. T.; Hines, D. E.; Walter, B. A.; Peng, C. Y.

1992-01-01

A surface mean-square-slope parameter analysis is conducted for 14-GHz airborne radar altimeter near-nadir, quasi-specular backscatter data, which in raw form obtained by least-squares fitting of an optical scattering model to the return waveform show an approximately linear dependence over the 7-15 m/sec wind speed range. Slope data are used to draw inferences on the structure of the high-wavenumber portion of the spectrum. A directionally-integrated model height spectrum that encompasses wind speed-dependent k exp -5/2 and classical Phillips k exp -3 power laws subranges in the range of gravity waves is supported by the data.

The structure of the stably stratified internal boundary layer in offshore flow over the sea

NASA Astrophysics Data System (ADS)

Garratt, J. R.; Ryan, B. F.

1989-04-01

Observations obtained mainly from a research aircraft are presented of the mean and turbulent structure of the stably stratified internal boundary layer (IBL) over the sea formed by warm air advection from land to sea. The potential temperature and humidity fields reveal the vertical extent of the IBL, for fetches out to several hundred of kilometres, geostrophic winds of 20 25 m s-1, and potential temperature differences between undisturbed continental air and the sea surface of 7 to 17 K. The dependence of IBL depth on these external parameters is discussed in the context of the numerical results of Garratt (1987), and some discrepancies are noted. Wind observations show the development of a low-level wind maximum (wind component normal to the coast) and rotation of the wind to smaller cross-isobar flow angles. Potential temperature (θ) profiles within the IBL reveal quite a different structure to that found in the nocturnal boundary layer (NBL) over land. Over the sea, θ profiles have large positive curvature with vertical gradients increasing monotonically with height; this reflects the dominance of turbulent cooling within the layer. The behaviour is consistent with known behaviour in the NBL over land where curvature becomes negative (vertical gradients of θ decreasing with height) as radiative cooling becomes dominant. Turbulent properties are discussed in terms of non-dimensional quantities, normalised by the surface friction velocity, as functions of normalised height using the IBL depth. Vertical profiles of these and the normalised wavelength of the spectral maximum agree well with known results for the stable boundary layer over land (Caughey et al., 1979).

Simulation of laser beam reflection at the sea surface modeling and validation

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric; Repasi, Endre

2013-06-01

A 3D simulation of the reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation is suitable for the pre-calculation of images for cameras operating in different spectral wavebands (visible, short wave infrared) for a bistatic configuration of laser source and receiver for different atmospheric conditions. In the visible waveband the calculated detected total power of reflected laser light from a 660nm laser source is compared with data collected in a field trial. Our computer simulation comprises the 3D simulation of a maritime scene (open sea/clear sky) and the simulation of laser beam reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. To predict the view of a camera the sea surface radiance must be calculated for the specific waveband. Additionally, the radiances of laser light specularly reflected at the wind-roughened sea surface are modeled considering an analytical statistical sea surface BRDF (bidirectional reflectance distribution function). Validation of simulation results is prerequisite before applying the computer simulation to maritime laser applications. For validation purposes data (images and meteorological data) were selected from field measurements, using a 660nm cw-laser diode to produce laser beam reflection at the water surface and recording images by a TV camera. The validation is done by numerical comparison of measured total laser power extracted from recorded images with the corresponding simulation results. The results of the comparison are presented for different incident (zenith/azimuth) angles of the laser beam.

MMAB Operational Products

Science.gov Websites

Atlantic Real-Time Ocean Forecast System NOAA Wavewatch III® Ocean Wave Model Sea Ice Concentration Analysis Satellite Derived Ocean Surface Winds Daily Sea Surface Temperature Analysis Sea Ice Drift Model

Black Sea spectral bio-optical models based on satellite data and their applications for assessment of spatial and temporal variability in waters transparency, chlorophyll a content and primary production

NASA Astrophysics Data System (ADS)

Churilova, T.; Suslin, V.

2012-04-01

Satellite observations of ocean color provide a unique opportunity in oceanography to assess productivity of the sea on different spatial and temporal scales. However it has been shown that the standard SeaWiFS algorithm generally overestimates summer chlorophyll concentration and underestimates pigment content during spring phytoplankton bloom in comparison with in situ measurements. It is required to develop regional algorithms which are based on biooptical characteristics typical for the Sea and consequently could be used for correct transformation of spectral features of water-leaving radiance to chlorophyll a concentrations (Chl), light absorption features of suspended and dissolved organic matter (CDM), downwelling light attenuation coefficient/euphotic zone depth (PAR1%) and rate of primary synthesis of organic substances (PP). The numerous measurements of light absorption spectra of phytoplankton, non-algal particles and coloured dissolved organic matter carried out since 1996 in different seasons and regions of the Black Sea allowed to make a parameterization of the light absorption by all optically active components. Taking into account regional peculiarities of the biooptical parameters, their difference between seasons, shallow and deep-waters, their depth-dependent variability within photosynthetic zone regional spectral models for estimation of chlorophyll a concentration (Chl Model), colored dissolved and suspended organic matter absorption (CDM Model), downwelling irradiance (PAR Model) and primary production (PP Model) have been developed based on satellite data. Test of validation of models showed appropriate accuracy of the models. The developed models have been applied for estimation of spatial/temporal variability of chlorophyll a, dissolved organic matter concentrations, waters transparency, euphotic zone depth and primary production based on SeaWiFS data. Two weeks averaged maps of spatial distribution of these parameters have been composed for period from 1998 to 2009 (most of them presented on site http://blackseacolor.com/browser3.html). Comparative analysis of long-term series (since 1998) of these parameters with subsurface water temperature (SST) and solar radiance of the sea surface (PAR-0m) revealed the key factors determining the seasonal and inter-annual variations of Chl, PAR1%, CDM, PP. The seasonal dynamics of these parameters were more pronounced compared with inter-annual variability. The later was related to climate effect. In deep-waters region relatively lower SST during cold winters were forcing more intensive winter-spring phytoplankton bloom. In north-western shelf inter-annual variability in river (Danube) run off, which was related to climate change as well, determined year-to-year changing in Chl, CDM, PAR1%, and PP.

Validation of Airborne FMCW Radar Measurements of Snow Thickness Over Sea Ice in Antarctica

NASA Technical Reports Server (NTRS)

Galin, Natalia; Worby, Anthony; Markus, Thorsten; Leuschen, Carl; Gogineni, Prasad

2012-01-01

Antarctic sea ice and its snow cover are integral components of the global climate system, yet many aspects of their vertical dimensions are poorly understood, making their representation in global climate models poor. Remote sensing is the key to monitoring the dynamic nature of sea ice and its snow cover. Reliable and accurate snow thickness data are currently a highly sought after data product. Remotely sensed snow thickness measurements can provide an indication of precipitation levels, predicted to increase with effects of climate change in the polar regions. Airborne techniques provide a means for regional-scale estimation of snow depth and distribution. Accurate regional-scale snow thickness data will also facilitate an increase in the accuracy of sea ice thickness retrieval from satellite altimeter freeboard estimates. The airborne data sets are easier to validate with in situ measurements and are better suited to validating satellite algorithms when compared with in situ techniques. This is primarily due to two factors: better chance of getting coincident in situ and airborne data sets and the tractability of comparison between an in situ data set and the airborne data set averaged over the footprint of the antennas. A 28-GHz frequency modulated continuous wave (FMCW) radar loaned by the Center for Remote Sensing of Ice Sheets to the Australian Antarctic Division is used to measure snow thickness over sea ice in East Antarctica. Provided with the radar design parameters, the expected performance parameters of the radar are summarized. The necessary conditions for unambiguous identification of the airsnow and snowice layers for the radar are presented. Roughnesses of the snow and ice surfaces are found to be dominant determinants in the effectiveness of layer identification for this radar. Finally, this paper presents the first in situ validated snow thickness estimates over sea ice in Antarctica derived from an FMCW radar on a helicopterborne platform.

Fast ice in the Canadian Arctic: Climatology, Atmospheric Forcing and Relation to Bathymetry

NASA Astrophysics Data System (ADS)

Galley, R. J.; Barber, D. G.

2010-12-01

Mobile sea ice in the northern hemisphere has experienced significant reductions in both extent and thickness over the last thirty years, and global climate models agree that these decreases will continue. However, the Canadian Arctic Archipelago (CAA) creates a much different icescape than in the central Arctic Ocean due to its distinctive topographic, bathymetric and climatological conditions. Of particular interest is the continued viability of landfast sea ice as a means of transportation and platform for transportation and hunting for the Canadian Inuit that reside in the region, as is the possibility of the Northwest Passage becoming a viable shipping lane in the future. Here we determine the climatological average landfast ice conditions in the Canadian Arctic Archipelago over the last 27 years, we investigate variability and trends in these landfast ice conditions, and we attempt to elucidate the physical parameters conducive to landfast sea ice formation in sub-regions of the CAA during different times of the year. We use the Canadian Ice Service digital sea ice charts between 1983 and 2009 on a 2x2km grid to determine the sea ice concentration-by-type and whether the sea ice in a grid cell was landfast on a weekly, bi-weekly or monthly basis depending on the time of year. North American Regional Reanalysis (NARR) atmospheric data were used in this work, including air temperature, surface level pressure and wind speed and direction. The bathymetric data employed was from the International Bathymetric Chart of the Arctic Ocean. Results indicate that the CAA sea ice regime is not climatologically analogous to the mobile sea ice of the central Arctic Ocean. The sea ice and the atmospheric and bathymetric properties that control the amount and timing of landfast sea ice within the CAA are regionally variable.

Assessing environmental changes in Lake Shihwa, South Korea, based on distributions and stable carbon isotopic compositions of n-alkanes.

PubMed

Kim, Dahae; Kim, Jung-Hyun; Kim, Min-Seob; Ra, Kongtae; Shin, Kyung-Hoon

2018-05-04

We investigate historical environmental changes in an artificial lake, Lake Shihwa in South Korea, based on bulk (TOC, TN, C/N ratio, δ 13 C TOC , and δ 15 N TN ) and molecular (concentrations and δ 13 C of n-alkanes) parameters, by analyzing riverbank sediments (n = 12), lake surface sediments (n = 9), and lake core sediments (n = 108). Although the bulk organic parameters showed similar characteristics for all lake surface sediment samples, the distribution pattern and δ 13 C of n-alkanes revealed distinct differences between 2009 samples and 2012/2016 samples. This change of sedimentary organic matter characteristics can be attributed to operation of the tidal power plant that began in 2011, which improved lake water circulation and thus changed the lake sedimentary environment from anoxic to more oxic conditions. The vertical profiles of bulk and molecular lake sediment core records collected in 2009, especially at the site closest to the dike, showed a drastic shift around 1987, indicating that stronger anoxic sedimentary conditions prevailed after 1987. This is linked to sea dike construction in 1987, which prohibited sea-lake water exchange and thus deteriorated water quality in Lake Shihwa. We conclude that Lake Shihwa has experienced severe environmental changes due to human activities. Copyright © 2018 Elsevier Ltd. All rights reserved.

Radio emission of sea surface at centimeter wavelengths and is fluctuations

NASA Technical Reports Server (NTRS)

Tseytlin, N. M.; Shutko, A. M.; Zhislin, G. M.

1981-01-01

The eigen thermal radio emission of the sea was examined as well as the agitated surface of the sea when the reflection (scattering) is similar in nature to diffused scattering. The contribution of this emission to the total emission of the sea is practically constant in time, and the time fluctuations of the radio emissions of the sea are basically determined only by a change in the eigen emission of the sea, connected with the agitation.

The recovery of microwave scattering parameters from scatterometric measurements with special application to the sea

NASA Technical Reports Server (NTRS)

Claassen, J. P.; Fung, A. K.

1975-01-01

As part of an effort to demonstrate the value of the microwave scatterometer as a remote sea wind sensor, the interaction between an arbitrarily polarized scatterometer antenna and a noncoherent distributive target was derived and applied to develop a measuring technique to recover all the scattering parameters. The results are helpful for specifying antenna polarization properties for accurate retrieval of the parameters not only for the sea but also for other distributive scenes.

Southern Ocean Climate and Sea Ice Anomalies Associated with the Southern Oscillation

NASA Technical Reports Server (NTRS)

Kwok, R.; Comiso, J. C.

2001-01-01

The anomalies in the climate and sea ice cover of the Southern Ocean and their relationships with the Southern Oscillation (SO) are investigated using a 17-year of data set from 1982 through 1998. We correlate the polar climate anomalies with the Southern Oscillation index (SOI) and examine the composites of these anomalies under the positive (SOI > 0), neutral (0 > SOI > -1), and negative (SOI < -1) phases of SOL The climate data set consists of sea-level pressure, wind, surface air temperature, and sea surface temperature fields, while the sea ice data set describes its extent, concentration, motion, and surface temperature. The analysis depicts, for the first time, the spatial variability in the relationship of the above variables and the SOL The strongest correlation between the SOI and the polar climate anomalies are found in the Bellingshausen, Amundsen and Ross sea sectors. The composite fields reveal anomalies that are organized in distinct large-scale spatial patterns with opposing polarities at the two extremes of SOI, and suggest oscillating climate anomalies that are closely linked to the SO. Within these sectors, positive (negative) phases of the SOI are generally associated with lower (higher) sea-level pressure, cooler (warmer) surface air temperature, and cooler (warmer) sea surface temperature in these sectors. Associations between these climate anomalies and the behavior of the Antarctic sea ice cover are clearly evident. Recent anomalies in the sea ice cover that are apparently associated with the SOI include: the record decrease in the sea ice extent in the Bellingshausen Sea from mid- 1988 through early 199 1; the relationship between Ross Sea SST and ENSO signal, and reduced sea ice concentration in the Ross Sea; and, the shortening of the ice season in the eastern Ross Sea, Amundsen Sea, far western Weddell Sea, and the lengthening of the ice season in the western Ross Sea, Bellingshausen Sea and central Weddell Sea gyre over the period 1988-1994. Four ENSO episodes over the last 17 years contributed to a negative mean in the SOI (-0.5). In each of these episodes, significant retreats in the Bellingshausen/Amundsen Sea were observed providing direct confirmation of the impact of SO on the Antarctic sea ice cover.

Experiences in multiyear combined state-parameter estimation with an ecosystem model of the North Atlantic and Arctic Oceans using the Ensemble Kalman Filter

NASA Astrophysics Data System (ADS)

Simon, Ehouarn; Samuelsen, Annette; Bertino, Laurent; Mouysset, Sandrine

2015-12-01

A sequence of one-year combined state-parameter estimation experiments has been conducted in a North Atlantic and Arctic Ocean configuration of the coupled physical-biogeochemical model HYCOM-NORWECOM over the period 2007-2010. The aim is to evaluate the ability of an ensemble-based data assimilation method to calibrate ecosystem model parameters in a pre-operational setting, namely the production of the MyOcean pilot reanalysis of the Arctic biology. For that purpose, four biological parameters (two phyto- and two zooplankton mortality rates) are estimated by assimilating weekly data such as, satellite-derived Sea Surface Temperature, along-track Sea Level Anomalies, ice concentrations and chlorophyll-a concentrations with an Ensemble Kalman Filter. The set of optimized parameters locally exhibits seasonal variations suggesting that time-dependent parameters should be used in ocean ecosystem models. A clustering analysis of the optimized parameters is performed in order to identify consistent ecosystem regions. In the north part of the domain, where the ecosystem model is the most reliable, most of them can be associated with Longhurst provinces and new provinces emerge in the Arctic Ocean. However, the clusters do not coincide anymore with the Longhurst provinces in the Tropics due to large model errors. Regarding the ecosystem state variables, the assimilation of satellite-derived chlorophyll concentration leads to significant reduction of the RMS errors in the observed variables during the first year, i.e. 2008, compared to a free run simulation. However, local filter divergences of the parameter component occur in 2009 and result in an increase in the RMS error at the time of the spring bloom.

Spatial patterns of cryptobenthic coral-reef fishes in the Red Sea

NASA Astrophysics Data System (ADS)

Coker, Darren J.; DiBattista, Joseph D.; Sinclair-Taylor, Tane H.; Berumen, Michael L.

2018-03-01

Surveys to document coral-reef fish assemblages are often limited to visually conspicuous species, thus excluding a significant proportion of the biodiversity. Through standardized collections of cryptobenthic reef fishes in the central and southern Red Sea, a total of 238 species and operational taxonomic units (OTUs) from 35 families were collected. Abundance and species richness increased by 60 and 30%, respectively, from north to south, and fish community composition differed between the two regions and with proximity to shore in the central region. Models suggest regional influences in fish communities, with latitudinal patterns influenced by key coral groups ( Acropora, Pocilloporidae) and variation in environmental parameters (chlorophyll a, sea surface temperature, salinity). This study illustrates the limited taxonomic resolution in this group and in this region, and the need to expand baseline data for this under-studied assemblage. To assist in advancing this initiative, we have produced a catalogue of specimens, archived photographs, and established a DNA sequence library based on cytochrome-c oxidase subunit-I barcodes for all OTUs.

Sea Surface Salinity : Research Challenges and Opportunities

NASA Technical Reports Server (NTRS)

Halpern, David; Lagerloef, Gary; Font, Jordi

2012-01-01

Sea surface salinity (SSS) can be important in regulating sea surface temperature (SST). Two technological breakthrough satellite SSS missions, Aquarius and Soil Moisture and Ocean Salinity (SMOS), are currently producing high-quality SSS data. This paper provides an overview of the importance of SSS for weather and climate applications and describes the Aquarius and SMOS missions. The newness of adequately sampled SSS data prompted a first-time at-sea field campaign devoted to improved understanding of SSS variations.

Discriminating Sea Spikes in Incoherent Radar Measurements of Sea Clutter

DTIC Science & Technology

2008-03-01

het detecteren echter niet te verwachten dat bet gebruik van sea spikes te onderzoeken. Een van deze modellen zal leiden tot een Auteur (s) dergelijk...report I TNO-DV 2008 A067 6/33 Abbreviations CFAR Constant False-Alarm Rate CST Composite Surface Theory FFT Fast Fourier Transform PDF Probability Density...described by the composite surface theory (CST). This theory describes the sea surface as small Bragg-resonant capillary waves riding on top of

Using ship-borne GNSS data for geoid model validation at the Baltic Sea

NASA Astrophysics Data System (ADS)

Nordman, Maaria; Kuokkanen, Jaakko; Bilker-Koivula, Mirjam; Koivula, Hannu; Häkli, Pasi; Lahtinen, Sonja

2017-04-01

We present a study of geoid model validation using ship-borne GNSS data on the Bothnian Bay of the Baltic Sea. In autumn 2015 a dedicated gravity survey took place in the Bothnian Bay on board of the surveying vessel Airisto as a part of the FAMOS (Finalising surveys for the Baltic motorways of the sea) Freja project, which is supported by the European Commission with the Connecting Europe Facility. The gravity data was collected to test older existing gravity data in the area and to contribute to a new improved geoid model for the Baltic Sea. The raw GNSS and IMU data of the vessel were recorded in order to study the possibilities for validating geoid models at sea. In order to derive geoid heights from GNSS-measurements at sea, the GNSS measurements must first be reduced to sea level. The instant sea level, also called sea surface height, must then be modelled and removed in order to get the GNSS positions at the zero height. In theory, the resulting GNSS heights are the geoid heights, giving the distance between the ellipsoid and the geoid surface. There were altogether 46 lines measured during the campaign on the area. The 1 Hz GNSS-IMU observations were post-processed using the Applanix POSPac MMS 7.1 software. Different processing options were tested and the Single Base -solution was found to be the best strategy. There were some issues with the quality of the data and cycle slips and thus, 37 of the lines were of adequate quality for the geoid validation. The final coordinates were transferred to the coordinate systems related to the geoid models used. Translation of the processed heights to sea level was performed taking the pitch and roll effects of the vessel into account. Also the effects of static and dynamic draft (squat) were applied. For the reduction from sea surface to geoid surface, the sea surface heights were derived from tide gauge data and also from a physical model for the Baltic Sea. The residual errors between the GNSS-derived geoid heights and geoid heights from geoid models were as low as 2 mm on some lines. When the overall mean is taken from the mean of all lines, the lowest value of 2.1 cm, was achieved using a physical model for the sea surface and comparing with the NKG2015 geoid model. The NKG2015 model together with the tide gauge sea surface yield 3.1 cm. Comparing with Finnish geoid model gave 3.7 and 4.7 cm for the physical model and tide gauge surfaces, respectively. The mean standard deviations were below 5 cm, when the data was filtered with a 10 min. moving average. Thus, it can be said that with high quality GNSS solution and enough information on the coordinate systems, vessel movements and the sea surface heights, geoid heights can be recovered from GNSS observations at sea.

The seasonal and inter-annual variability of sea-ice, ocean circulation and marine ecosystems in the Barents Sea: model results against satellite data

NASA Astrophysics Data System (ADS)

Dvornikov, Anton; Sein, Dmitry; Ryabchenko, Vladimir; Gorchakov, Victor; Pugalova, Svetlana

2015-04-01

This study is aimed at modelling the seasonal and inter-annual variability of sea-ice, ocean circulation and marine ecosystems in the Barents Sea in the modern period. Adequate description of marine ecosystems in the ice-covered seas crucially depends on the accuracy in determining of thicknesses of ice and snow on the sea surface which control penetrating photosynthetically active radiation under the ice. One of the few models of ice able to adequately reproduce the dynamics of sea ice is the sea ice model HELMI [1], containing 7 different categories of ice. This model has been imbedded into the Princeton Ocean Model. With this coupled model 2 runs for the period 1998-2007 were performed under different atmospheric forcing prescribed from NCEP/NCAR and ERA-40 archives. For prescribing conditions at the open boundary, all the necessary information about the horizontal velocity, level, temperature and salinity of the water, ice thickness and compactness was taken from the results of the global ocean general circulation model of the Max Planck Institute for Meteorology (Hamburg, Germany) MPIOM [2]. The resulting solution with NCEP forcing with a high accuracy simulates the seasonal and inter-annual variability of sea surface temperature (SST) estimated from MODIS data. The maximum difference between the calculated and satellite-derived SSTs (averaged over 4 selected areas of the Barents Sea) during the period 2000-2007 does not exceed 1.5 °C. Seasonal and inter-annual variations in the area of ice cover are also in good agreement with satellite-derived estimates. Pelagic ecosystem model developed in [3] has been coupled into the above hydrodynamic model and used to calculate the changes in the characteristics of marine ecosystems under NCEP forcing. Preliminarily the ecosystem model has been improved by introducing a parameterization of detritus deposition on the bottom and through the selection of optimal parameters for photosynthesis and zooplankton grazing, providing a solution having acceptable agreement with SeaWiFS estimates of surface chlorophyll "a" concentration. The solution for the period 1998-2007 correctly reproduces the start and end of vegetation period, and, with satisfactory accuracy, the level of the spring phytoplankton bloom, but systematically overestimates the SeaWiFS chlorophyll concentrations in the northern part of the sea and in the summer everywhere except for the southern part. According to the results, the region of phytoplankton blooming during the spring outbreak is bounded by the western boundary of the sea and the edge of solid ice. This work was supported by RFBR project № 13-05-00652 References 1. Haapala, J., Lönnroth, N., Stössel, A., 2005. A numerical study of open water formation in sea ice. J. Geophys. Res., V. 110(C9). P.1-17: doi: 10.1029/2003JC002200. 2. Gröger M., E. Maier-Reimer, U. Mikolajewicz, A. Moll, and D. Sein, 2013. NW European shelf under climate warming: implications for open ocean - shelf exchange, primary production, and carbon absorption. Biogeosciences, vol.10, 3767-3792, doi:10.5194/bg-10-3767-2013. 3. Anderson T.R., V. A. Ryabchenko; M. J. Fasham; V. A. Gorchakov. Denitrification in the Arabian Sea: A 3D ecosystem modeling study. Deep-Sea Research, Part I, V. 54, Issue 12, 2007, 2082-2119

Impact of surface roughness on L-band emissivity of the sea ice

NASA Astrophysics Data System (ADS)

Miernecki, M.; Kaleschke, L.; Hendricks, S.; Søbjærg, S. S.

2015-12-01

In March 2014 a joint experiment IRO2/SMOSice was carried out in the Barents Sea. R/V Lance equipped with meteorological instruments, electromagnetic sea ice thickness probe and engine monitoring instruments, was performing a series of tests in different ice conditions in order to validate the ice route optimization (IRO) system, advising on his route through pack ice. In parallel cal/val activities for sea ice thickness product obtained from SMOS (Soil Moisture and Ocean Salinity mission) L-band radiometer were carried out. Apart from helicopter towing the EMbird thickness probe, Polar 5 aircraft was serving the area during the experiment with L-band radiometer EMIRAD2 and Airborne Laser Scanner (ALS) as primary instruments. Sea ice Thickness algorithm using SMOS brightness temperature developed at University of Hamburg, provides daily maps of thin sea ice (up to 0.5-1 m) in polar regions with resolution of 35-50 km. So far the retrieval method was not taking into account surface roughness, assuming that sea ice is a specular surface. Roughness is a stochastic process that can be characterized by standard deviation of surface height σ and by shape of the autocorrelation function R to estimate it's vertical and horizontal scales respectively. Interactions of electromagnetic radiation with the surface of the medium are dependent on R and σ and they scales with respect to the incident wavelength. During SMOSice the radiometer was observing sea ice surface at two incidence angles 0 and 40 degrees and simultaneously the surface elevation was scanned with ALS with ground resolution of ~ 0.25 m. This configuration allowed us to calculate σ and R from power spectral densities of surface elevation profiles and quantify the effect of surface roughness on the emissivity of the sea ice. First results indicate that Gaussian autocorrelation function is suitable for deformed ice, for other ice types exponential function is the best fit.

Coupling of WRF meteorological model to WAM spectral wave model through sea surface roughness at the Balearic Sea: impact on wind and wave forecasts

NASA Astrophysics Data System (ADS)

Tolosana-Delgado, R.; Soret, A.; Jorba, O.; Baldasano, J. M.; Sánchez-Arcilla, A.

2012-04-01

Meteorological models, like WRF, usually describe the earth surface characteristics by tables that are function of land-use. The roughness length (z0) is an example of such approach. However, over sea z0 is modeled by the Charnock (1955) relation, linking the surface friction velocity u*2 with the roughness length z0 of turbulent air flow, z0 = α-u2* g The Charnock coefficient α may be considered a measure of roughness. For the sea surface, WRF considers a constant roughness α = 0.0185. However, there is evidence that sea surface roughness should depend on wave energy (Donelan, 1982). Spectral wave models like WAM, model the evolution and propagation of wave energy as a function of wind, and include a richer sea surface roughness description. Coupling WRF and WAM is thus a common way to improve the sea surface roughness description of WRF. WAM is a third generation wave model, solving the equation of advection of wave energy subject to input/output terms of: wind growth, energy dissipation and resonant non-linear wave-wave interactions. Third generation models work on the spectral domain. WAM considers the Charnock coefficient α a complex yet known function of the total wind input term, which depends on the wind velocity and on the Charnock coefficient again. This is solved iteratively (Janssen et al., 1990). Coupling of meteorological and wave models through a common Charnock coefficient is operationally done in medium-range met forecasting systems (e.g., at ECMWF) though the impact of coupling for smaller domains is not yet clearly assessed (Warner et al, 2010). It is unclear to which extent the additional effort of coupling improves the local wind and wave fields, in comparison to the effects of other factors, like e.g. a better bathymetry and relief resolution, or a better circulation information which might have its influence on local-scale meteorological processes (local wind jets, local convection, daily marine wind regimes, etc.). This work, within the scope of the 7th EU FP Project FIELD_AC, assesses the impact of coupling WAM and WRF on wind and wave forecasts on the Balearic Sea, and compares it with other possible improvements, like using available high-resolution circulation information from MyOcean GMES core services, or assimilating altimeter data on the Western Mediterranean. This is done in an ordered fashion following statistical design rules, which allows to extract main effects of each of the factors considered (coupling, better circulation information, data assimilation following Lionello et al., 1992) as well as two-factor interactions. Moreover, the statistical significance of these improvements can be tested in the future, though this requires maximum likelihood ratio tests with correlated data. Charnock, H. (1955) Wind stress on a water surface. Quart.J. Row. Met. Soc. 81: 639-640 Donelan, M. (1982) The dependence of aerodynamic drag coefficient on wave parameters. Proc. 1st Int. Conf. on Meteorology and Air-Sea Interactions of teh Coastal Zone. The Hague (Netherlands). AMS. 381-387 Janssen, P.A.E.M., Doyle, J., Bidlot, J., Hansen, B., Isaksen, L. and Viterbo, P. (1990) The impact of oean waves on the atmosphere. Seminars of the ECMWF. Lionello, P., Günther, H., and Janssen P.A.E.M. (1992) Assimilation of altimeter data in a global third-generation wave model. Journal of Geophysical Research 97 (C9): 453-474. Warner, J., Armstrong, B., He, R. and Zambon, J.B. (2010) Development of a Coupled Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System. Ocean Modelling 35: 230-244.

Response of carbon fluxes and climate to orbital forcing changes in the Community Climate System Model

NASA Astrophysics Data System (ADS)

Jochum, M.; Peacock, S.; Moore, J. K.; Lindsay, K. T.

2009-12-01

A global general circulation model coupled to an ocean ecosystem model is used to quantify the response of carbon fluxes and climate to changes in orbital forcing. Compared to the present-day simulation, the simulation with the Earth's orbital parameters from 115,000 years ago features significantly cooler northern high latitudes, but only moderately cooler southern high latitudes. This asymmetry is explained by a 30% reduction of the strength of the Atlantic Meridional Overturning Circulation that is caused by an increased Arctic sea-ice export and a resulting freshening of the North Atlantic. The strong northern high-latitude cooling and the direct insolation induced tropical warming lead to global shifts in precipitation and winds to the order of 10-20%. These climate shifts lead to regional differences in air-sea carbon fluxes of the same order. However, the differences in global net carbon fluxes are insignificant. This surprising result is due to several effects, two of which stand out: Firstly, colder sea surface temperature leads to a more effective solubility pump but also to increased sea-ice concentration which blocks air-sea exchange; and secondly, the weakening of Southern Ocean winds, which is predicted by some idealized studies, is small compared to its interannual variability.

Sea Ice Detection Based on Differential Delay-Doppler Maps from UK TechDemoSat-1

PubMed Central

Zhu, Yongchao; Yu, Kegen; Zou, Jingui; Wickert, Jens

2017-01-01

Global Navigation Satellite System (GNSS) signals can be exploited to remotely sense atmosphere and land and ocean surface to retrieve a range of geophysical parameters. This paper proposes two new methods, termed as power-summation of differential Delay-Doppler Maps (PS-D) and pixel-number of differential Delay-Doppler Maps (PN-D), to distinguish between sea ice and sea water using differential Delay-Doppler Maps (dDDMs). PS-D and PN-D make use of power-summation and pixel-number of dDDMs, respectively, to measure the degree of difference between two DDMs so as to determine the transition state (water-water, water-ice, ice-ice and ice-water) and hence ice and water are detected. Moreover, an adaptive incoherent averaging of DDMs is employed to improve the computational efficiency. A large number of DDMs recorded by UK TechDemoSat-1 (TDS-1) over the Arctic region are used to test the proposed sea ice detection methods. Through evaluating against ground-truth measurements from the Ocean Sea Ice SAF, the proposed PS-D and PN-D methods achieve a probability of detection of 99.72% and 99.69% respectively, while the probability of false detection is 0.28% and 0.31% respectively. PMID:28704948

Southern Ocean Climate and Sea Ice Anomalies Associated with the Southern Oscillation.

NASA Astrophysics Data System (ADS)

Kwok, R.; Comiso, J. C.

2002-03-01

The anomalies in the climate and sea ice cover of the Southern Ocean and their relationships with the Southern Oscillation (SO) are investigated using a 17-yr dataset from 1982 to 1998. The polar climate anomalies are correlated with the Southern Oscillation index (SOI) and the composites of these anomalies are examined under the positive (SOI > 0), neutral (0 > SOI > 1), and negative (SOI < 1) phases of SOI. The climate dataset consists of sea level pressure, wind, surface air temperature, and sea surface temperature fields, while the sea ice dataset describes its extent, concentration, motion, and surface temperature. The analysis depicts, for the first time, the spatial variability in the relationship of the above variables with the SOI. The strongest correlation between the SOI and the polar climate anomalies are found in the Bellingshausen, Amundsen, and Ross Seas. The composite fields reveal anomalies that are organized in distinct large-scale spatial patterns with opposing polarities at the two extremes of SOI, and suggest oscillations that are closely linked to the SO. Within these sectors, positive (negative) phases of the SOI are generally associated with lower (higher) sea level pressure, cooler (warmer) surface air temperature, and cooler (warmer) sea surface temperature in these sectors. Associations between these climate anomalies and the behavior of the Antarctic sea ice cover are evident. Recent anomalies in the sea ice cover that are clearly associated with the SOI include the following: the record decrease in the sea ice extent in the Bellingshausen Sea from mid-1988 to early 1991; the relationship between Ross Sea SST and the ENSO signal, and reduced sea ice concentration in the Ross Sea; and the shortening of the ice season in the eastern Ross Sea, Amundsen Sea, far western Weddell Sea and lengthening of the ice season in the western Ross Sea, Bellinghausen Sea, and central Weddell Sea gyre during the period 1988-94. Four ENSO episodes over the last 17 years contributed to a negative mean in the SOI (0.5). In each of these episodes, significant retreats in ice cover of the Bellingshausen and Amundsen Seas were observed showing a unique association of this region of the Antarctic with the Southern Oscillation.

Assessing sea wave and spray effects on Marine Boundary Layer structure

NASA Astrophysics Data System (ADS)

Stathopoulos, Christos; Galanis, George; Patlakas, Platon; Kallos, George

2017-04-01

Air sea interface is characterized by several mechanical and thermodynamical processes. Heat, moisture and momentum exchanges increase the complexity in modeling the atmospheric-ocean system. Near surface atmospheric levels are subject to sea surface roughness and sea spray. Sea spray fluxes can affect atmospheric stability and induce microphysical processes such as sea salt particle formation and condensation/evaporation of water in the boundary layer. Moreover, presence of sea spray can alter stratification over the ocean surface with further insertion of water vapor. This can lead to modified stability conditions and to wind profiles that deviate significantly from the logarithmic approximation. To model these effects, we introduce a fully coupled system consisting of the mesoscale atmospheric model RAMS/ICLAMS and the wave model WAM. The system encompasses schemes for ocean surface roughness, sea salt aerosols and droplet thermodynamic processes and handles sea salt as predictive quantity. Numerical experiments using the developed atmospheric-ocean system are performed over the Atlantic and Mediterranean shoreline. Emphasis is given to the quantification of the improvement obtained in the description of the marine boundary layer, particularly in its lower part as well as in wave characteristics.

Probing the intrinsically oil-wet surfaces of pores in North Sea chalk at subpore resolution.

PubMed

Hassenkam, T; Skovbjerg, L L; Stipp, S L S

2009-04-14

Pore surface properties control oil recovery. This is especially true for chalk reservoirs, where pores are particularly small. Wettability, the tendency for a surface to cover itself with fluid, is traditionally defined by the angle a droplet makes with a surface, but this macroscopic definition is meaningless when the particles are smaller than even the smallest droplet. Understanding surface wetting, at the pore scale, will provide clues for more effective oil recovery. We used a special mode of atomic force microscopy and a hydrophobic tip to collect matrices of 10,000 force curves over 5- x 5-mum(2) areas on internal pore surfaces and constructed maps of topography, adhesion, and elasticity. We investigated chalk samples from a water-bearing formation in the Danish North Sea oil fields that had never seen oil. Wettability and elasticity were inhomogeneous over scales of 10s of nanometers, smaller than individual chalk particles. Some areas were soft and hydrophobic, whereas others showed no correlation between hardness and adhesion. We conclude that the macroscopic parameter, "wetting," averages the nanoscopic behavior along fluid pathways, and "mixed-wet" samples have patches with vastly different properties. Development of reservoir hydrophobicity has been attributed to infiltrating oil, but these new results prove that wettability and elasticity are inherent properties of chalk. Their variability, even on single particles, must result from material originally present during sedimentation or material sorbed from the pore fluid some time later.

Probing the intrinsically oil-wet surfaces of pores in North Sea chalk at subpore resolution

PubMed Central

Hassenkam, T.; Skovbjerg, L. L.; Stipp, S. L. S.

2009-01-01

Pore surface properties control oil recovery. This is especially true for chalk reservoirs, where pores are particularly small. Wettability, the tendency for a surface to cover itself with fluid, is traditionally defined by the angle a droplet makes with a surface, but this macroscopic definition is meaningless when the particles are smaller than even the smallest droplet. Understanding surface wetting, at the pore scale, will provide clues for more effective oil recovery. We used a special mode of atomic force microscopy and a hydrophobic tip to collect matrices of 10,000 force curves over 5- × 5-μm2 areas on internal pore surfaces and constructed maps of topography, adhesion, and elasticity. We investigated chalk samples from a water-bearing formation in the Danish North Sea oil fields that had never seen oil. Wettability and elasticity were inhomogeneous over scales of 10s of nanometers, smaller than individual chalk particles. Some areas were soft and hydrophobic, whereas others showed no correlation between hardness and adhesion. We conclude that the macroscopic parameter, “wetting,” averages the nanoscopic behavior along fluid pathways, and “mixed-wet” samples have patches with vastly different properties. Development of reservoir hydrophobicity has been attributed to infiltrating oil, but these new results prove that wettability and elasticity are inherent properties of chalk. Their variability, even on single particles, must result from material originally present during sedimentation or material sorbed from the pore fluid some time later. PMID:19321418

Arctic Sea Ice Classification and Mapping for Surface Albedo Parameterization in Sea Ice Modeling

NASA Astrophysics Data System (ADS)

Nghiem, S. V.; Clemente-Colón, P.; Perovich, D. K.; Polashenski, C.; Simpson, W. R.; Rigor, I. G.; Woods, J. E.; Nguyen, D. T.; Neumann, G.

2016-12-01

A regime shift of Arctic sea ice from predominantly perennial sea ice (multi-year ice or MYI) to seasonal sea ice (first-year ice or FYI) has occurred in recent decades. This shift has profoundly altered the proportional composition of different sea ice classes and the surface albedo distribution pertaining to each sea ice class. Such changes impacts physical, chemical, and biological processes in the Arctic atmosphere-ice-ocean system. The drastic changes upset the traditional geophysical representation of surface albedo of the Arctic sea ice cover in current models. A critical science issue is that these profound changes must be rigorously and systematically observed and characterized to enable a transformative re-parameterization of key model inputs, such as ice surface albedo, to ice-ocean-atmosphere climate modeling in order to obtain re-analyses that accurately reproduce Arctic changes and also to improve sea ice and weather forecast models. Addressing this challenge is a strategy identified by the National Research Council study on "Seasonal to Decadal Predictions of Arctic Sea Ice - Challenges and Strategies" to replicate the new Arctic reality. We review results of albedo characteristics associated with different sea ice classes such as FYI and MYI. Then we demonstrate the capability for sea ice classification and mapping using algorithms developed by the Jet Propulsion Laboratory and by the U.S. National Ice Center for use with multi-sourced satellite radar data at L, C, and Ku bands. Results obtained with independent algorithms for different radar frequencies consistently identify sea ice classes and thereby cross-verify the sea ice classification methods. Moreover, field observations obtained from buoy webcams and along an extensive trek across Elson Lagoon and a sector of the Beaufort Sea during the BRomine, Ozone, and Mercury EXperiment (BROMEX) in March 2012 are used to validate satellite products of sea ice classes. This research enables the mapping of Arctic sea ice classes over multiple decades using multiple satellite radar datasets with both coarse resolution for synoptic scales and high resolution for local and regional scales, which are crucial for realistic surface albedo parameterization to significantly advance sea ice forecast and projection models.

Design studies of large aperture, high-resolution Earth science microwave radiometers compatible with small launch vehicles

NASA Technical Reports Server (NTRS)

Schroeder, Lyle C.; Bailey, M. C.; Harrington, Richard F.; Kendall, Bruce M.; Campbell, Thomas G.

1994-01-01

High-spatial-resolution microwave radiometer sensing from space with reasonable swath widths and revisit times favors large aperture systems. However, with traditional precision antenna design, the size and weight requirements for such systems are in conflict with the need to emphasize small launch vehicles. This paper describes tradeoffs between the science requirements, basic operational parameters, and expected sensor performance for selected satellite radiometer concepts utilizing novel lightweight compactly packaged real apertures. Antenna, feed, and radiometer subsystem design and calibration are presented. Preliminary results show that novel lightweight real aperture coupled with state-of-the-art radiometer designs are compatible with small launch systems, and hold promise for high-resolution earth science measurements of sea ice, precipitation, soil moisture, sea surface temperature, and ocean wind speeds.

Effects of wind waves on horizontal array performance in shallow-water conditions

NASA Astrophysics Data System (ADS)

Zavol'skii, N. A.; Malekhanov, A. I.; Raevskii, M. A.; Smirnov, A. V.

2017-09-01

We analyze the influence of statistical effects of the propagation of an acoustic signal excited by a tone source in a shallow-water channel with a rough sea surface on the efficiency of a horizontal phased array. As the array characteristics, we consider the angular function of the array response for a given direction to the source and the coefficient of amplification of the signal-to-noise ratio (array gain). Numerical simulation was conducted in to the winter hydrological conditions of the Barents Sea in a wide range of parameters determining the spatial signal coherence. The results show the main physical effects of the influence of wind waves on the array characteristics and make it possible to quantitatively predict the efficiency of a large horizontal array in realistic shallow-water channels.

Wind-sea surface temperature-sea ice relationship in the Chukchi-Beaufort Seas during autumn

NASA Astrophysics Data System (ADS)

Zhang, Jing; Stegall, Steve T.; Zhang, Xiangdong

2018-03-01

Dramatic climate changes, especially the largest sea ice retreat during September and October, in the Chukchi-Beaufort Seas could be a consequence of, and further enhance, complex air-ice-sea interactions. To detect these interaction signals, statistical relationships between surface wind speed, sea surface temperature (SST), and sea ice concentration (SIC) were analyzed. The results show a negative correlation between wind speed and SIC. The relationships between wind speed and SST are complicated by the presence of sea ice, with a negative correlation over open water but a positive correlation in sea ice dominated areas. The examination of spatial structures indicates that wind speed tends to increase when approaching the ice edge from open water and the area fully covered by sea ice. The anomalous downward radiation and thermal advection, as well as their regional distribution, play important roles in shaping these relationships, though wind-driven sub-grid scale boundary layer processes may also have contributions. Considering the feedback loop involved in the wind-SST-SIC relationships, climate model experiments would be required to further untangle the underlying complex physical processes.

Seasonal Ice Zone Reconnaissance Surveys Coordination and Ocean Profiles

DTIC Science & Technology

2015-09-30

Morison), UpTempO buoy measurements of sea surface temperature (SST), sea level atmospheric pressure ( SLP ), and velocity (Steele), and dropsonde...dropsondes, micro-aircraft), cloud top/base heights UpTempO buoys for understanding and prediction…. Steele UpTempO buoy drops for SLP , SST, SSS...Air Expendable Current Profiler, SLP = Sea Level atmospheric Pressure, SST= Seas Surface Temperature, A/C= aircraft, SIC=Sea Ice Concentration We

Impact of Langmuir Turbulence on Upper Ocean Response to Hurricane Edouard: Model and Observations

NASA Astrophysics Data System (ADS)

Blair, A.; Ginis, I.; Hara, T.; Ulhorn, E.

2017-12-01

Tropical cyclone intensity is strongly affected by the air-sea heat flux beneath the storm. When strong storm winds enhance upper ocean turbulent mixing and entrainment of colder water from below the thermocline, the resulting sea surface temperature cooling may reduce the heat flux to the storm and weaken the storm. Recent studies suggest that this upper ocean turbulence is strongly affected by different sea states (Langmuir turbulence), which are highly complex and variable in tropical cyclone conditions. In this study, the upper ocean response under Hurricane Edouard (2014) is investigated using a coupled ocean-wave model with and without an explicit sea state dependent Langmuir turbulence parameterization. The results are compared with in situ observations of sea surface temperature and mixed layer depth from AXBTs, as well as satellite sea surface temperature observations. Overall, the model results of mixed layer deepening and sea surface temperature cooling under and behind the storm are consistent with observations. The model results show that the effects of sea state dependent Langmuir turbulence can be significant, particularly on the mixed layer depth evolution. Although available observations are not sufficient to confirm such effects, some observed trends suggest that the sea state dependent parameterization might be more accurate than the traditional (sea state independent) parameterization.

Kinematic parameters of second-mode internal waves in the South China Sea

NASA Astrophysics Data System (ADS)

Kurkina, Oxana; Talipova, Tatiana; Kurkin, Andrey; Naumov, Alexander; Rybin, Artem

2017-04-01

Kinematic parameters of second-mode internal waves (in the framework of weakly nonlinear model of the Gardner equation) are calculated for the region of the South China Sea on a base of GDEM climatology. The prognostic parameters of the model include phase speed of long linear waves, coefficients of dispersion, quadratic and cubic nonlinearity, location (in vertical) of minimum, zero and maximum of the second vertical baroclinic mode and the ratio of its maximal and minimal values. All the parameters are presented in the form of geographical maps for winter (January) and summer (July) seasons. Frequence (in the sense of occurrence) histograms and scatter plots with depth are also given for all the parameters. Special attention is paid to the conditions of normalizing for internal waves of the second mode, as it possesses two extremes. Here some freedom exists, but for correct further modeling of internal waves within the Gardner model one has to fix and keep the same normalization (at maximum or at minimum) for whole a basin. Constructed arrays of prognostic parameters of second-mode internal waves are necessary for the estimations of shape and width (at fixed amplitude) of internal solitary and breather-like waves, limiting amplitudes of internal solitary waves of different families, for assessment of near-bed and near-surface flows induced by such waves, and for evaluation of transport distance for dissolved and suspended matter. The presented results of research are obtained with the support of the Russian Foundation for Basic Research grant 16-05-00049.

Global comparisons between the modified Pathfinder derived sea surface temperature and skin temperatures from the along-track scanning radiometer on board ERS-2: how close are we getting?

NASA Technical Reports Server (NTRS)

Vazquez, J.

2001-01-01

Sea Surface Temperatures (SST) as derived from the Pathfinder Sea Surface Temperature Data Set and the Along-Track Scanning Radiometer on-board the European Remote Sensing Satellite provide a unique opportunity for comparing two independent SST data sets.

Application of advanced data assimilation techniques to the study of cloud and precipitation feedbacks in the tropical climate system

NASA Astrophysics Data System (ADS)

Posselt, Derek J.

The research documented in this study centers around two topics: evaluation of the response of precipitating cloud systems to changes in the tropical climate system, and assimilation of cloud and precipitation information from remote-sensing platforms. The motivation for this work proceeds from the following outstanding problems: (1) Use of models to study the response of clouds to perturbations in the climate system is hampered by uncertainties in cloud microphysical parameterizations. (2) Though there is an ever-growing set of available observations, cloud and precipitation assimilation remains a difficult problem, particularly in the tropics. (3) Though it is widely acknowledged that cloud and precipitation processes play a key role in regulating the Earth's response to surface warming, the response of the tropical hydrologic cycle to climate perturbations remains largely unknown. The above issues are addressed in the following manner. First, Markov chain Monte Carlo (MCMC) methods are used to quantify the sensitivity of the NASA Goddard Cumulus Ensemble (GCE) cloud resolving model (CRM) to changes in its cloud odcrnpbymiC8l parameters. TRMM retrievals of precipitation rate, cloud properties, and radiative fluxes and heating rates over the South China Sea are then assimilated into the GCE model to constrain cloud microphysical parameters to values characteristic of convection in the tropics, and the resulting observation-constrained model is used to assess the response of the tropical hydrologic cycle to surface warming. The major findings of this study are the following: (1) MCMC provides an effective tool with which to evaluate both model parameterizations and the assumption of Gaussian statistics used in optimal estimation procedures. (2) Statistics of the tropical radiation budget and hydrologic cycle can be used to effectively constrain CRM cloud microphysical parameters. (3) For 2D CRM simulations run with and without shear, the precipitation efficiency of cloud systems increases with increasing sea surface temperature, while the high cloud fraction and outgoing shortwave radiation decrease.

Pacific Dictates Droughts and Drenchings

NASA Image and Video Library

2004-01-30

The latest remote sensing data from NASA's Jason satellite show that the equatorial Pacific sea surface levels are higher, indicating warmer sea surface temperatures in the central and west Pacific Ocean. This pattern has the appearance of La Niña rather than El Niño. This contrasts with the Bering Sea, Gulf of Alaska and U.S. West Coast where lower-than-normal sea surface levels and cool ocean temperatures continue (indicated by blue and purple areas). The image above is a global map of sea surface height, accurate to within 30 millimeters. The image represents data collected and composited over a 10-day period, ending on Jan 23, 2004. The height of the water relates to the temperature of the water. As the ocean warms, its level rises; and as it cools, its level falls. Yellow and red areas indicate where the waters are relatively warmer and have expanded above sea level, green indicates near normal sea level, and blue and purple areas show where the waters are relatively colder and the surface is lower than sea level. The blue areas are between 5 and 13 centimeters (2 and 5 inches) below normal, whereas the purple areas range from 14 to 18 centimeters (6 to 7 inches) below normal. http://photojournal.jpl.nasa.gov/catalog/PIA05071

Arctic Sea Ice: Using Airborne Topographic Mapper Measurements (ATM) to Determine Sea Ice Thickness

DTIC Science & Technology

2011-05-10

Track Distance (Km) E le v a ti o n ( m ) ATM Elevation Profile Elevation 18 Figure 13: Geoid shape of earth’s equipotential surface , which is...inferred for the region between successive leads. Therefore, flying over a lead in the ice is very important for determining the exact sea surface elevation...inferred for the region between successive leads. Therefore, flying over a lead in the ice is very important for determining the exact sea surface

Assessment of radar altimetry correction slopes for marine gravity recovery: A case study of Jason-1 GM data

NASA Astrophysics Data System (ADS)

Zhang, Shengjun; Li, Jiancheng; Jin, Taoyong; Che, Defu

2018-04-01

Marine gravity anomaly derived from satellite altimetry can be computed using either sea surface height or sea surface slope measurements. Here we consider the slope method and evaluate the errors in the slope of the corrections supplied with the Jason-1 geodetic mission data. The slope corrections are divided into three groups based on whether they are small, comparable, or large with respect to the 1 microradian error in the current sea surface slope models. (1) The small and thus negligible corrections include dry tropospheric correction, inverted barometer correction, solid earth tide and geocentric pole tide. (2) The moderately important corrections include wet tropospheric correction, dual-frequency ionospheric correction and sea state bias. The radiometer measurements are more preferred than model values in the geophysical data records for constraining wet tropospheric effect owing to the highly variable water-vapor structure in atmosphere. The items of dual-frequency ionospheric correction and sea state bias should better not be directly added to range observations for obtaining sea surface slopes since their inherent errors may cause abnormal sea surface slopes and along-track smoothing with uniform distribution weight in certain width is an effective strategy for avoiding introducing extra noises. The slopes calculated from radiometer wet tropospheric corrections, and along-track smoothed dual-frequency ionospheric corrections, sea state bias are generally within ±0.5 microradians and no larger than 1 microradians. (3) Ocean tide has the largest influence on obtaining sea surface slopes while most of ocean tide slopes distribute within ±3 microradians. Larger ocean tide slopes mostly occur over marginal and island-surrounding seas, and extra tidal models with better precision or with extending process (e.g. Got-e) are strongly recommended for updating corrections in geophysical data records.

Spatial scales of light transmission through Antarctic pack ice: Surface flooding vs. floe-size distribution

NASA Astrophysics Data System (ADS)

Arndt, S.; Meiners, K.; Krumpen, T.; Ricker, R.; Nicolaus, M.

2016-12-01

Snow on sea ice plays a crucial role for interactions between the ocean and atmosphere within the climate system of polar regions. Antarctic sea ice is covered with snow during most of the year. The snow contributes substantially to the sea-ice mass budget as the heavy snow loads can depress the ice below water level causing flooding. Refreezing of the snow and seawater mixture results in snow-ice formation on the ice surface. The snow cover determines also the amount of light being reflected, absorbed, and transmitted into the upper ocean, determining the surface energy budget of ice-covered oceans. The amount of light penetrating through sea ice into the upper ocean is of critical importance for the timing and amount of bottom sea-ice melt, biogeochemical processes and under-ice ecosystems. Here, we present results of several recent observations in the Weddell Sea measuring solar radiation under Antarctic sea ice with instrumented Remotely Operated Vehicles (ROV). The combination of under-ice optical measurements with simultaneous characterization of surface properties, such as sea-ice thickness and snow depth, allows the identification of key processes controlling the spatial distribution of the under-ice light. Thus, our results show how the distinction between flooded and non-flooded sea-ice regimes dominates the spatial scales of under-ice light variability for areas smaller than 100-by-100m. In contrast, the variability on larger scales seems to be controlled by the floe-size distribution and the associated lateral incidence of light. These results are related to recent studies on the spatial variability of Arctic under-ice light fields focusing on the distinctly differing dominant surface properties between the northern (e.g. summer melt ponds) and southern (e.g. year-round snow cover, surface flooding) hemisphere sea-ice cover.

Deep Coherent Vortices and Their Sea Surface Expressions

NASA Astrophysics Data System (ADS)

Ienna, Federico; Bashmachnikov, Igor; Dias, Joaquim; Peliz, Alvaro

2017-04-01

Mediterranean Water eddies, known as Meddies, are an important dynamic process occurring at depths of 1000-meters in the Northeast Atlantic Ocean. Meddies occur as a direct result of the Mediterranean Outflow exiting through the Gibraltar Strait, and represent a prevalent mechanism that can be found extensively throughout the ocean. Moreover, Meddy cores are known to produce measurable expressions at the sea surface in the form of rotating coherent vortices, not only affecting the sea surface from beneath, but also allowing for the possibility to remotely study these deep phenomena through data gathered at the sea surface. While many past studies have focused on the properties of Meddy cores, only a handful of studies focus on the physical characteristics and behavior of the surface expressions produced. Are Meddy surface expressions different from other like vortices that dominate the physical ocean surface? What are the relationships between deep and surface mechanisms, and do any feedbacks exist? To shed light on these questions, we investigate the relationship between Meddies and their sea-surface expressions through observations using in-situ float and drifter profiles and satellite altimetry. A total of 782 Meddy cores were examined in the Northeast Atlantic using temperature and salinity data obtained by CTD and Argo during the Mecanismos de transporte e de dispersão da Água Mediterrânica no Atlântico Nordeste (MEDTRANS) project, and their corresponding sea-level expressions were geo-temporally matched in satellite altimetry data. We report several statistical properties of the sea-surface expressions of Meddies, including their mean diameter and vertical magnitude, and compare the properties of their surface features to the underlying Meddy cores. We investigate how the deep core affects the surface, and whether surface expressions may in return yield information about the underlying cores. Additionally, we examine the variability of the surface expressions, including seasonal and geographical variability.

Simulation of a polarized laser beam reflected at the sea surface: modeling and validation

NASA Astrophysics Data System (ADS)

Schwenger, Frédéric

2015-05-01

A 3-D simulation of the polarization-dependent reflection of a Gaussian shaped laser beam on the dynamic sea surface is presented. The simulation considers polarized or unpolarized laser sources and calculates the polarization states upon reflection at the sea surface. It is suitable for the radiance calculation of the scene in different spectral wavebands (e.g. near-infrared, SWIR, etc.) not including the camera degradations. The simulation also considers a bistatic configuration of laser source and receiver as well as different atmospheric conditions. In the SWIR, the detected total power of reflected laser light is compared with data collected in a field trial. Our computer simulation combines the 3-D simulation of a maritime scene (open sea/clear sky) with the simulation of polarized or unpolarized laser light reflected at the sea surface. The basic sea surface geometry is modeled by a composition of smooth wind driven gravity waves. To predict the input of a camera equipped with a linear polarizer, the polarized sea surface radiance must be calculated for the specific waveband. The s- and p-polarization states are calculated for the emitted sea surface radiance and the specularly reflected sky radiance to determine the total polarized sea surface radiance of each component. The states of polarization and the radiance of laser light specularly reflected at the wind-roughened sea surface are calculated by considering the s- and p- components of the electric field of laser light with respect to the specular plane of incidence. This is done by using the formalism of their coherence matrices according to E. Wolf [1]. Additionally, an analytical statistical sea surface BRDF (bidirectional reflectance distribution function) is considered for the reflection of laser light radiances. Validation of the simulation results is required to ensure model credibility and applicability to maritime laser applications. For validation purposes, field measurement data (images and meteorological data) was analyzed. An infrared laser, with or without a mounted polarizer, produced laser beam reflection at the water surface and images were recorded by a camera equipped with a polarizer with horizontal or vertical alignment. The validation is done by numerical comparison of measured total laser power extracted from recorded images with the corresponding simulation results. The results of the comparison are presented for different incident (zenith/azimuth) angles of the laser beam and different alignment for the laser polarizers (vertical/horizontal/without) and the camera (vertical/horizontal).

Ensemble-Based Parameter Estimation in a Coupled General Circulation Model

DOE PAGES

Liu, Y.; Liu, Z.; Zhang, S.; ...

2014-09-10

Parameter estimation provides a potentially powerful approach to reduce model bias for complex climate models. Here, in a twin experiment framework, the authors perform the first parameter estimation in a fully coupled ocean–atmosphere general circulation model using an ensemble coupled data assimilation system facilitated with parameter estimation. The authors first perform single-parameter estimation and then multiple-parameter estimation. In the case of the single-parameter estimation, the error of the parameter [solar penetration depth (SPD)] is reduced by over 90% after ~40 years of assimilation of the conventional observations of monthly sea surface temperature (SST) and salinity (SSS). The results of multiple-parametermore » estimation are less reliable than those of single-parameter estimation when only the monthly SST and SSS are assimilated. Assimilating additional observations of atmospheric data of temperature and wind improves the reliability of multiple-parameter estimation. The errors of the parameters are reduced by 90% in ~8 years of assimilation. Finally, the improved parameters also improve the model climatology. With the optimized parameters, the bias of the climatology of SST is reduced by ~90%. Altogether, this study suggests the feasibility of ensemble-based parameter estimation in a fully coupled general circulation model.« less

Tropical Cyclone Information System

NASA Technical Reports Server (NTRS)

Li, P. Peggy; Knosp, Brian W.; Vu, Quoc A.; Yi, Chao; Hristova-Veleva, Svetla M.

2009-01-01

The JPL Tropical Cyclone Infor ma tion System (TCIS) is a Web portal (http://tropicalcyclone.jpl.nasa.gov) that provides researchers with an extensive set of observed hurricane parameters together with large-scale and convection resolving model outputs. It provides a comprehensive set of high-resolution satellite (see figure), airborne, and in-situ observations in both image and data formats. Large-scale datasets depict the surrounding environmental parameters such as SST (Sea Surface Temperature) and aerosol loading. Model outputs and analysis tools are provided to evaluate model performance and compare observations from different platforms. The system pertains to the thermodynamic and microphysical structure of the storm, the air-sea interaction processes, and the larger-scale environment as depicted by ocean heat content and the aerosol loading of the environment. Currently, the TCIS is populated with satellite observations of all tropical cyclones observed globally during 2005. There is a plan to extend the database both forward in time till present as well as backward to 1998. The portal is powered by a MySQL database and an Apache/Tomcat Web server on a Linux system. The interactive graphic user interface is provided by Google Map.

Reflective properties of melt ponds on sea ice

NASA Astrophysics Data System (ADS)

Malinka, Aleksey; Zege, Eleonora; Istomina, Larysa; Heygster, Georg; Spreen, Gunnar; Perovich, Donald; Polashenski, Chris

2018-06-01

Melt ponds occupy a large part of the Arctic sea ice in summer and strongly affect the radiative budget of the atmosphere-ice-ocean system. In this study, the melt pond reflectance is considered in the framework of radiative transfer theory. The melt pond is modeled as a plane-parallel layer of pure water upon a layer of sea ice (the pond bottom). We consider pond reflection as comprising Fresnel reflection by the water surface and multiple reflections between the pond surface and its bottom, which is assumed to be Lambertian. In order to give a description of how to find the pond bottom albedo, we investigate the inherent optical properties of sea ice. Using the Wentzel-Kramers-Brillouin approximation approach to light scattering by non-spherical particles (brine inclusions) and Mie solution for spherical particles (air bubbles), we conclude that the transport scattering coefficient in sea ice is a spectrally independent value. Then, within the two-stream approximation of the radiative transfer theory, we show that the under-pond ice spectral albedo is determined by two independent scalar values: the transport scattering coefficient and ice layer thickness. Given the pond depth and bottom albedo values, the bidirectional reflectance factor (BRF) and albedo of a pond can be calculated with analytical formulas. Thus, the main reflective properties of the melt pond, including their spectral dependence, are determined by only three independent parameters: pond depth z, ice layer thickness H, and transport scattering coefficient of ice σt.The effects of the incident conditions and the atmosphere state are examined. It is clearly shown that atmospheric correction is necessary even for in situ measurements. The atmospheric correction procedure has been used in the model verification. The optical model developed is verified with data from in situ measurements made during three field campaigns performed on landfast and pack ice in the Arctic. The measured pond albedo spectra were fitted with the modeled spectra by varying the pond parameters (z, H, and σt). The coincidence of the measured and fitted spectra demonstrates good performance of the model: it is able to reproduce the albedo spectrum in the visible range with RMSD that does not exceed 1.5 % for a wide variety of melt pond types observed in the Arctic.

Propagation regimes and populations of internal waves in the Mediterranean Sea basin

NASA Astrophysics Data System (ADS)

Kurkina, Oxana; Rouvinskaya, Ekaterina; Talipova, Tatiana; Soomere, Tarmo

2017-02-01

The geographical and seasonal distributions of kinematic and nonlinear parameters of long internal waves are derived from the Generalized Digital Environmental Model (GDEM) climatology for the Mediterranean Sea region, including the Black Sea. The considered parameters are phase speed of long internal waves and the coefficients at the dispersion, quadratic and cubic terms of the weakly-nonlinear Korteweg-de Vries-type models (in particular, the Gardner model). These parameters govern the possible polarities and shapes of solitary internal waves, their limiting amplitudes and propagation speeds. The key outcome is an express estimate of the expected parameters of internal waves for different regions of the Mediterranean basin.

Effects of ocean acidification, warming and melting of sea ice on aragonite saturation of the Canada Basin surface water

NASA Astrophysics Data System (ADS)

Yamamoto-Kawai, M.; McLaughlin, F. A.; Carmack, E. C.

2011-02-01

In 2008, surface waters in the Canada Basin of the Arctic Ocean were found to be undersaturated with respect to aragonite. This is associated with recent extensive melting of sea ice in this region, as well as elevated sea surface temperature and atmospheric CO2 concentrations. We have estimated the relative contribution of each of these controlling factors to the calcium carbonate saturation state (Ω) from observations of dissolved inorganic carbon, total alkalinity and oxygen isotope ratio. Results indicate that the increase in atmospheric CO2 has lowered surface Ω by ˜0.3 in the Canada Basin since the preindustrial period. Recent melting of sea ice has further lowered mean Ω by 0.4, and of this, half was due to dilution of surface water and half was due to the change in air-sea disequilibrium state. Surface water warming has generally counteracted the mean decrease in Ω by 0.1.

On the Simulation of Sea States with High Significant Wave Height for the Validation of Parameter Retrieval Algorithms for Future Altimetry Missions

NASA Astrophysics Data System (ADS)

Kuschenerus, Mieke; Cullen, Robert

2016-08-01

To ensure reliability and precision of wave height estimates for future satellite altimetry missions such as Sentinel 6, reliable parameter retrieval algorithms that can extract significant wave heights up to 20 m have to be established. The retrieved parameters, i.e. the retrieval methods need to be validated extensively on a wide range of possible significant wave heights. Although current missions require wave height retrievals up to 20 m, there is little evidence of systematic validation of parameter retrieval methods for sea states with wave heights above 10 m. This paper provides a definition of a set of simulated sea states with significant wave height up to 20 m, that allow simulation of radar altimeter response echoes for extreme sea states in SAR and low resolution mode. The simulated radar responses are used to derive significant wave height estimates, which can be compared with the initial models, allowing precision estimations of the applied parameter retrieval methods. Thus we establish a validation method for significant wave height retrieval for sea states causing high significant wave heights, to allow improved understanding and planning of future satellite altimetry mission validation.

Observation of Sea Ice Surface Thermal States Under Cloud Cover

NASA Technical Reports Server (NTRS)

Nghiem, S. V.; Perovich, D. K.; Gow, A. J.; Kwok, R.; Barber, D. G.; Comiso, J. C.; Zukor, Dorothy J. (Technical Monitor)

2001-01-01

Clouds interfere with the distribution of short-wave and long-wave radiations over sea ice, and thereby strongly affect the surface energy balance in polar regions. To evaluate the overall effects of clouds on climatic feedback processes in the atmosphere-ice-ocean system, the challenge is to observe sea ice surface thermal states under both clear sky and cloudy conditions. From laboratory experiments, we show that C-band radar (transparent to clouds) backscatter is very sensitive to the surface temperature of first-year sea ice. The effect of sea ice surface temperature on the magnitude of backscatter change depends on the thermal regimes of sea ice thermodynamic states. For the temperature range above the mirabilite (Na2SO4.10H20) crystallization point (-8.2 C), C-band data show sea ice backscatter changes by 8-10 dB for incident angles from 20 to 35 deg at both horizontal and vertical polarizations. For temperatures below the mirabilite point but above the crystallization point of MgCl2.8H2O (-18.0 C), relatively strong backwater changes between 4-6 dB are observed. These backscatter changes correspond to approximately 8 C change in temperature for both cases. The backscattering mechanism is related to the temperature which determines the thermodynamic distribution of brine volume in the sea ice surface layer. The backscatter is positively correlated to temperature and the process is reversible with thermodynamic variations such as diurnal insolation effects. From two different dates in May 1993 with clear and overcast conditions determined by the Advanced Very High Resolution Radiometer (AVHRR), concurrent Earth Resources Satellite 1 (ERS-1) C-band ice observed with increases in backscatter over first-year sea ice, and verified by increases in in-situ sea ice surface temperatures measured at the Collaborative-Interdisciplinary Cryosphere Experiment (C-ICE) site.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Y.; Liu, Z.; Zhang, S.

Parameter estimation provides a potentially powerful approach to reduce model bias for complex climate models. Here, in a twin experiment framework, the authors perform the first parameter estimation in a fully coupled ocean–atmosphere general circulation model using an ensemble coupled data assimilation system facilitated with parameter estimation. The authors first perform single-parameter estimation and then multiple-parameter estimation. In the case of the single-parameter estimation, the error of the parameter [solar penetration depth (SPD)] is reduced by over 90% after ~40 years of assimilation of the conventional observations of monthly sea surface temperature (SST) and salinity (SSS). The results of multiple-parametermore » estimation are less reliable than those of single-parameter estimation when only the monthly SST and SSS are assimilated. Assimilating additional observations of atmospheric data of temperature and wind improves the reliability of multiple-parameter estimation. The errors of the parameters are reduced by 90% in ~8 years of assimilation. Finally, the improved parameters also improve the model climatology. With the optimized parameters, the bias of the climatology of SST is reduced by ~90%. Altogether, this study suggests the feasibility of ensemble-based parameter estimation in a fully coupled general circulation model.« less