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Sample records for sea-surface polarized microwave

  1. Sea surface signature of tropical cyclones using microwave remote sensing

    NASA Astrophysics Data System (ADS)

    Kil, Bumjun; Burrage, Derek; Wesson, Joel; Howden, Stephan

    2013-06-01

    Measuring the sea surface during tropical cyclones (TC) is challenging due to severe weather conditions that prevent shipboard measurements and clouds which mask the sea surface for visible satellite sensors. However, sea surface emission in the microwave L-band can penetrate rain and clouds and be measured from space. The European Space Agency (ESA) MIRAS L-band radiometer on the Soil Moisture and Ocean Salinity (SMOS) satellite enables a view of the sea surface from which the effects of tropical cyclones on sea surface emissivity can be measured. The emissivity at these frequencies is a function of sea surface salinity (SSS), sea surface temperature (SST), sea surface roughness, polarization, and angle of emission. If the latter four variables can be estimated, then models of the sea surface emissivity can be used to invert SSS from measured brightness temperature (TB). Actual measured TB from space also has affects due to the ionosphere and troposphere, which have to be compensated for, and components due to the galactic and cosmic background radiation those have to be removed. In this research, we study the relationships between retrieved SSS from MIRAS, and SST and precipitation collected by the NASA TMI sensor from the Tropical Rainfall Measuring Mission (TRMM) satellite during Hurricane Isaac, in August 2012. During the slower movement of the storm, just before landfall on the vicinity of the Louisiana Shelf, higher precipitation amounts were associated with lower SSS and slightly increased SST. This increased trend of SST and lower SSS under regions of high precipitation are indicative of inhibited vertical mixing. The SMOS Level 2 SSS were filtered by a stepwise process with removal of high uncertainty in TB under conditions of strong surface roughness which are known to create noise. The signature of increased SST associated with increasing precipitation was associated with decreased SSS during the storm. Although further research is required, this study

  2. Microwave Imager Measures Sea Surface Temperature Through Clouds

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This image was acquired over Tropical Atlantic and U.S. East Coast regions on Aug. 22 - Sept. 23, 1998. Cloud data were collected by the Geostationary Operational Environmental Satellite (GOES). Sea Surface Temperature (SST) data were collected aboard the NASA/NASDA Tropical Rainfall Measuring Mission (TRMM) satellite by The TRMM Microwave Imager (TMI). TMI is the first satellite microwave sensor capable of accurately measuring sea surface temperature through clouds, as shown in this scene. For years scientists have known there is a strong correlation between sea surface temperature and the intensity of hurricanes. But one of the major stumbling blocks for forecasters has been the precise measurement of those temperatures when a storm begins to form. In this scene, clouds have been made translucent to allow an unobstructed view of the surface. Notice Hurricane Bonnie approaching the Carolina Coast (upper left) and Hurricane Danielle following roughly in its path (lower right). The ocean surface has been falsely colored to show a map of water temperature--dark blues are around 75oF, light blues are about 80oF, greens are about 85oF, and yellows are roughly 90oF. A hurricane gathers energy from warm waters found at tropical latitudes. In this image we see Hurricane Bonnie cross the Atlantic, leaving a cooler trail of water in its wake. As Hurricane Danielle followed in Bonnie's path, the wind speed of the second storm dropped markedly, as available energy to fuel the storm dropped off. But when Danielle left Bonnie's wake, wind speeds increased due to temperature increases in surface water around the storm. As a hurricane churns up the ocean, it's central vortex draws surface heat and water into the storm. That suction at the surface causes an upwelling of deep water. At depth, tropical ocean waters are significantly colder than water found near the surface. As they're pulled up to meet the storm, those colder waters essentially leave a footprint in the storm's wake

  3. Detecting nonlinearities in microwave return from the sea surface

    NASA Astrophysics Data System (ADS)

    Heia, Karsten; Eltoft, Torbjorn

    1994-12-01

    In this paper we discuss the properties of two different methods for extracting information of non-linear mechanisms influencing the backscatter of microwaves from the ocean surface. In the first of these methods, denoted the Multi Frequency Technique (MFT), several frequencies, distributed in a narrow band around a carrier frequency, are simultaneously transmitted, and the non-linearities are detected as secondary peaks in their mutual cross-product spectrum. This technique has been extensively discussed in earlier papers as a proper method for extracting sea surface information (Alpers, W., and K. Hasselmann, 1978). The second method uses only the transmitted frequency and the non-linear effects are detected as secondary (or over-harmonic) frequency peaks in the bispectrum of the backscattered signal. This method has been successfully applied to studies of non-linear wave-wave iterations in experimental plasma physics, but has to the authors' knowledge not been used in studies of microwave scattering from the sea surface. We refer to this method as the Bispectral Analysis Technique (BAT). In order to correctly interpret the different signatures observed in microwave remote sensing of the ocean surface, it is important to fully understand how various physical phenomena influence the backscattered signal. The data used in this work, are generated by a numerical simulator. Based on the Holliday scattering model and a theoretical description of the power spectrum of the surface elevation, we are able to study in detail how various physical and geometrical conditions influence the backscattered signal. Specifically, we address the problem of detecting non-linear hydrodynamical phenomena induced by non-linear hydrodynamical phenomena (Stokes-type gravity waves) or non-linear modulation mechanisms (tilt and hydrodynamic modulation), using the MFT and BAT. We show in this paper that both methods are capable of detecting non-linear features, but that the performance is

  4. Skylab S-193 Radscat microwave measurements of sea surface winds

    NASA Technical Reports Server (NTRS)

    Moore, R. K.; Fung, A. K.; Young, J. D.; Claassen, J. P.; Chan, H. L.; Afarani, M.; Pierson, W. J.; Cardone, V. J.; Hayes, J.; Spring, W.; Greenwood, C.

    1975-01-01

    The S-193 Radscat made extensive measurements of many sea conditions. Measurements were taken in a tropical hurricane (Ava), a tropical storm (Christine), and in portions of extratropical cyclones. Approximately 200 scans of ocean data at 105 kilometer spacings were taken during the first two Skylab missions and another 200 during the final mission when the characteristics of the measurements changed due to damage of the antenna. Backscatter with four transmit/receive polarization combinations and emissions with horizontal and vertical receive polarizations were measured. Other surface parameters investigated for correlation with the measurements included sea temperature, air/sea temperature difference, and gravity-wave spectrum. Methods were developed to correct the microwave measurements for atmospheric effects. The radiometric data were corrected accurately for clear sky and light cloud conditions only. The radiometer measurements were used to recover the surface scattering characteristics for all atmospheric conditions excluding rain. The radiometer measurements also detected the presence of rain which signaled when the scattering measurement should not be used for surface wind estimation. Regression analysis was used to determine empirically the relation between surface parameters and the microwave measurements, after correction for atmospheric effects. Results indicate a relationship approaching square-law at 50 deg between differential scattering coefficient and wind speed with horizontally polarized scattering data showing slightly more sensitivity to wind speed than vertically polarized data.

  5. Estimating Sea Surface Salinity and Wind Using Combined Passive and Active L-Band Microwave Observations

    NASA Technical Reports Server (NTRS)

    Yueh, Simon H.; Chaubell, Mario J.

    2012-01-01

    Several L-band microwave radiometer and radar missions have been, or will be, operating in space for land and ocean observations. These include the NASA Aquarius mission and the Soil Moisture Active Passive (SMAP) mission, both of which use combined passive/ active L-band instruments. Aquarius s passive/active L-band microwave sensor has been designed to map the salinity field at the surface of the ocean from space. SMAP s primary objectives are for soil moisture and freeze/thaw detection, but it will operate continuously over the ocean, and hence will have significant potential for ocean surface research. In this innovation, an algorithm has been developed to retrieve simultaneously ocean surface salinity and wind from combined passive/active L-band microwave observations of sea surfaces. The algorithm takes advantage of the differing response of brightness temperatures and radar backscatter to salinity, wind speed, and direction, thus minimizing the least squares error (LSE) measure, which signifies the difference between measurements and model functions of brightness temperatures and radar backscatter. The algorithm uses the conjugate gradient method to search for the local minima of the LSE. Three LSE measures with different measurement combinations have been tested. The first LSE measure uses passive microwave data only with retrieval errors reaching 1 to 2 psu (practical salinity units) for salinity, and 1 to 2 m/s for wind speed. The second LSE measure uses both passive and active microwave data for vertical and horizontal polarizations. The addition of active microwave data significantly improves the retrieval accuracy by about a factor of five. To mitigate the impact of Faraday rotation on satellite observations, the third LSE measure uses measurement combinations invariant under the Faraday rotation. For Aquarius, the expected RMS SSS (sea surface salinity) error will be less than about 0.2 psu for low winds, and increases to 0.3 psu at 25 m/s wind speed

  6. Variation of the microwave brightness temperature of sea surfaces covered with mineral and monomolecular oil films

    SciTech Connect

    Blume, H.J.; Alpers, W.; Huehnerfuss, H.

    1983-07-01

    Airborne microwave radiometer measurements over mineral and monomolecular oil films and adjacent clean sea surfaces are reported. An artificial crude-oil spill experiment in the New York Bight area showed a brightness temperature increase of the sea surface at 1.43 GHz as expected from a multilayered system with different dielectric constants. However, a monomolecular surface-film experiment with oleyl alcohol conducted in the North Sea during MARSEN in 1979 showed a strong brightness temperature depression at 1.43 GHz and no change in brightness temperature at 2.65 GHz. It is postulated that the monomolecular layer, because of its physical and chemical properties, polarized the underlying water molecules so strongly that the emissivity decreased from 0.31 to 0.016. It is estimated that the effective dielectric constant changed from 90 to 5.2 x 10/sup 4/. Because these phenomena occurred at 1.43 GHz it may be concluded that this frequency is very close to the center of a new anomalous dispersion region resulting from a restructuring of the water layer below the surface film.

  7. Global measurements of sea surface temperature, wind speed and atmospheric water content from satellite microwave radiometry

    NASA Technical Reports Server (NTRS)

    Njoku, E. G.; Swanson, L.

    1983-01-01

    The Scanning Multichannel Microwave Radiometer (SMMR) was launched on the Seasat and Nimbus 7 satellites in 1978. The SMMR has the ability to measure sea surface temperature and wind speed with the aid of microwaves. In addition, the instrument was designed to measure water vapor and cloud liquid water with better spatial resolution than previous microwave radiometers, and to make sea-ice measurements with higher precision. A description is presented of the results of global analyses of sea surface temperature, wind speed, water vapor, and cloud liquid water, taking into account data provided by the SMMR on the Seasat satellite. It is found that the SMMR data show good self-consistency, and can usefully measure global distributions of sea surface temperatures, surface winds, water vapor, and cloud liquid water.

  8. Ultra Stable Microwave Radiometers for Future Sea Surface Salinity Missions

    NASA Technical Reports Server (NTRS)

    Wilson, William J.; Tanner, Alan B.; Pellerano, Fernando A.; Horgan, Kevin A.

    2005-01-01

    The NASA Earth Science System Pathfinder (ESSP) mission Aquarius will measure global sea surface salinity with 100-km spatial resolution every 8 days with an average monthly salinity accuracy of 0.2 psu (parts per thousand). This requires an L-band low-noise radiometer with the long-term calibration stability of less than 0.1 K over 8 days. This three-year research program on ultra stable radiometers has addressed the radiometer requirements and configuration necessary to achieve this objective for Aquarius and future ocean salinity missions. The system configuration and component performance have been evaluated with radiometer testbeds at both JPL and GSFC. The research has addressed several areas including component characterization as a function of temperature, a procedure for the measurement and correction for radiometer system non-linearity, noise diode calibration versus temperature, low noise amplifier performance over voltage, and temperature control requirements to achieve the required stability. A breadboard radiometer, utilizing microstrip-based technologies, has been built to demonstrate this long-term stability. This report also presents the results of the radiometer test program, a detailed radiometer noise model, and details of the operational switching sequence optimization that can be used to achieve the low noise and stability requirements. Many of the results of this research have been incorporated into the Aquarius radiometer design and will allow this instrument to achieve its goals.

  9. 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

  10. Sea-surface temperature and salinity mapping from remote microwave radiometric measurements of brightness temperature

    NASA Technical Reports Server (NTRS)

    Hans-Juergen, C. B.; Kendall, B. M.; Fedors, J. C.

    1977-01-01

    A technique to measure remotely sea surface temperature and salinity was demonstrated with a dual frequency microwave radiometer system. Accuracies in temperature of 1 C and in salinity of part thousand for salinity greater than 5 parts per thousand were attained after correcting for the influence of extraterrestrial background radiation, atmospheric radiation and attenuation, sea-surface roughness, and antenna beamwidth. The radiometers, operating at 1.43 and 2.65 GHz, comprise a third-generation system using null balancing and feedback noise injection. Flight measurements from an aircraft at an altitude of 1.4 km over the lower Chesapeake Bay and coastal areas of the Atlantic Ocean resulted in contour maps of sea-surface temperature and salinity with a spatial resolution of 0.5 km.

  11. Rainfall on microwave return from the sea surface

    NASA Technical Reports Server (NTRS)

    Bliven, L. F.; Giovanangeli, J.-P.

    1988-01-01

    The long range goal remains unchanged; to conduct experiments and develop/test theoretical models to permit useful algorithms to be constructed for microwave systems that observe oceanic processes. This topic is relevant to altimeters, scatterometers, and rain rate measurements. The current focus is attention to scatterometer wind velocity measurement. One component of the laboratory efforts is an experiment conducted, in the wind wave tank at the GSFC/WFF, to quantify the effect of rain-generated surface wave brightening of radar cross section. Laboratory conditions can be characterized as light wind, functional rain rates, a single drop size, and a 36 GHz radar system at 30 degrees inclination.

  12. Microwave radiometer and scatterometer design for the aquarius sea surface Salinity Mission

    NASA Technical Reports Server (NTRS)

    Wilson, William J.; Yueh, Simon H.; Pellerano, Fernando

    2004-01-01

    The measurement of sea surface salinity with L-band microwave radiometers is a very challenging task. Since the L-band brightness temperature variations associated with salinity changes are small, it is necessary to have a very sensitive and stable radiometer. In addition, the corrections for the ocean surface roughness require real time scatterometer measurements. The designs of the Aquarius radiometer and scatterometer are described in this paper.

  13. Microwave Remote Sensing Modeling of Ocean Surface Salinity and Winds Using an Empirical Sea Surface Spectrum

    NASA Technical Reports Server (NTRS)

    Yueh, Simon H.

    2004-01-01

    Active and passive microwave remote sensing techniques have been investigated for the remote sensing of ocean surface wind and salinity. We revised an ocean surface spectrum using the CMOD-5 geophysical model function (GMF) for the European Remote Sensing (ERS) C-band scatterometer and the Ku-band GMF for the NASA SeaWinds scatterometer. The predictions of microwave brightness temperatures from this model agree well with satellite, aircraft and tower-based microwave radiometer data. This suggests that the impact of surface roughness on microwave brightness temperatures and radar scattering coefficients of sea surfaces can be consistently characterized by a roughness spectrum, providing physical basis for using combined active and passive remote sensing techniques for ocean surface wind and salinity remote sensing.

  14. The Effect of Sea-Surface Sun Glitter on Microwave Radiometer Measurements

    NASA Technical Reports Server (NTRS)

    Wentz, F. J.

    1981-01-01

    A relatively simple model for the microwave brightness temperature of sea surface Sun glitter is presented. The model is an accurate closeform approximation for the fourfold Sun glitter integral. The model computations indicate that Sun glitter contamination of on orbit radiometer measurements is appreciable over a large swath area. For winds near 20 m/s, Sun glitter affects the retrieval of environmental parameters for Sun angles as large as 20 to 25 deg. The model predicted biases in retrieved wind speed and sea surface temperature due to neglecting Sun glitter are consistent with those experimentally observed in SEASAT SMMR retrievals. A least squares retrieval algorithm that uses a combined sea and Sun model function shows the potential of retrieving accurate environmental parameters in the presence of Sun glitter so long as the Sun angles and wind speed are above 5 deg and 2 m/s, respectively.

  15. Polarized infrared emissivity of one-dimensional Gaussian sea surfaces with surface reflections.

    PubMed

    Li, Hongkun; Pinel, Nicolas; Bourlier, Christophe

    2011-08-10

    Surface reflection is an important phenomenon that must be taken into account when studying sea surface infrared emissivity, especially at large observation angles. This paper models analytically the polarized infrared emissivity of one-dimensional sea surfaces with shadowing effect and one surface reflection, by assuming a Gaussian surface slope distribution. A Monte Carlo ray-tracing method is employed as a reference. It is shown that the present model agrees well with the reference method. The emissivity calculated by the present model is then compared with measurements. The comparisons show that agreements are greatly improved by taking one surface reflection into account. The Monte Carlo ray-tracing results of sea surface infrared emissivity with two and three reflections are also determined. Their contributions are shown to be negligible. PMID:21833139

  16. Effects of light polarization and waves slope statistics on the reflectance factor of the sea surface.

    PubMed

    D'Alimonte, Davide; Kajiyama, Tamito

    2016-04-18

    Above-water radiometry depends on estimates of the reflectance factor ρ of the sea surface to compute the in situ water-leaving radiance. The Monte Carlo code for ocean color simulations MOX is used in this study to analyze the effect of different environmental components on ρ values. A first aspect is examining the reflectance factor without and by accounting for the sky-radiance polarization. The influence of the sea-surface statistics at discrete grid points is then considered by presenting a new scheme to define the variance of the waves slope. Results at different sun elevations and sensor orientations indicate that the light polarization effect on ρ simulations reduces from ∼17 to ∼10% when the wind speed increases from 0 to 14m s-1. An opposite tendency characterizes the modeling of the sea-surface slope variance, with ρ differences up to ∼12% at a wind speed of 10m s-1. The joint effect of polarization and the the sea-surface statistics displays a less systematic dependence on the wind speed, with differences in the range ∼13 to ∼18%. The ρ changes due to the light polarization and the variance of the waves slope become more relevant at sky-viewing geometries respectively lower and higher than 40° with respect to the zenith. An overall compensation of positive and negative offsets due to light polarization is finally documented when considering different sun elevations. These results address additional investigations which, by combining the modeling and experimental components of marine optics, better evaluate specific measurement protocols for collecting above-water radiometric data in the field. PMID:27137234

  17. Microwave Frequency Polarizers

    NASA Technical Reports Server (NTRS)

    Ha, Vien The; Mirel, Paul; Kogut, Alan J.

    2013-01-01

    This article describes the fabrication and analysis of microwave frequency polarizing grids. The grids are designed to measure polarization from the cosmic microwave background. It is effective in the range of 500 to 1500 micron wavelength. It is cryogenic compatible and highly robust to high load impacts. Each grid is fabricated using an array of different assembly processes which vary in the types of tension mechanisms to the shape and size of the grids. We provide a comprehensive study on the analysis of the grids' wire heights, diameters, and spacing.

  18. Ship motion estimation from polarized Doppler spectra from ship wakes on two-dimensional sea surfaces

    NASA Astrophysics Data System (ADS)

    Jiang, Wang-Qiang; Zhang, Min; Nie, Ding; Sun, Rong-Qing

    2016-07-01

    The main purpose of this paper is to investigate the Doppler spectra from ship wakes on two-dimensional sea surfaces and further estimate the ship motion characteristics. The analysis of the ship wakes is helpful to detect the existence of ships on sea surface. And it will be an alternative method when the radar cross-section values are not competent to identify the ship target. In the study, Doppler spectra for different polarizations are compared with and without ship's wakes based on the second-order small slope approximation method. As expected, there appears the second spectral peak when ship's wake is considered. Moreover, the ship velocities, wind speed, and direction are also analyzed. As the results shown, there is a good linearity relation between the position of the second Doppler spectral peak and the ship velocity. Therefore, it is feasible to detect ship according the Doppler spectra.

  19. Sea surface temperatures from the scanning multichannel microwave radiometer on Nimbus 7

    NASA Technical Reports Server (NTRS)

    Milman, A. S.; Wilheit, T. T.

    1985-01-01

    Because of problems with the design and calibration of the scanning multichannel microwave radiometer (SMMR) on Nimbus 7, sea surface temperature (SST) algorithms had to be developed that corrected for instrument effects. Several stages of this development are reported here. The quality of the SST products from the final version is assessed. Thirty-four months of data have been analyzed; the average SST error is about 1.12 C over the whole globe. The error is smaller in the equatorial region and larger in the northern oceans. The main source of error is due to heating of the SMMR instrument. Specific problems in the design of the instrument are discussed. The details of the ST algorithms are given in an appendix.

  20. Infrared and Passive Microwave Radiometric Sea Surface Temperatures and Their Relationships to Atmospheric Forcing

    NASA Technical Reports Server (NTRS)

    Castro, Sandra L.

    2004-01-01

    The current generation of infrared (IR) and passive microwave (MW) satellite sensors provides highly complementary information for monitoring sea surface temperature (SST). On the one hand, infrared sensors provide high resolution and high accuracy but are obscured by clouds. Microwave sensors on the other hand, provide coverage through non-precipitating clouds but have coarser resolution and generally poorer accuracy. Assuming that the satellite SST measurements do not have spatially variable biases, they can be blended combining the merits of both SST products. These factors have motivated recent work in blending the MW and IR data in an attempt to produce high-accuracy SST products with improved coverage in regions with persistent clouds. The primary sources of retrieval uncertainty are, however, different for the two sensors. The main uncertainty in the MW retrievals lies in the effects of wind-induced surface roughness and foam on emissivity, whereas the IR retrievals are more sensitive to the atmospheric water vapor and aerosol content. Average nighttime differences between the products for the month periods of January 1999 and June 2000 are shown. These maps show complex spatial and temporal differences as indicated by the strong spatially coherent features in the product differences and the changes between seasons. Clearly such differences need to be understood and accounted for if the products are to be combined. The overall goals of this project are threefold: (1) To understand the sources of uncertainty in the IR and MW SST retrievals and to characterize the errors affecting the two types of retrieval as a fiction of atmospheric forcing; (2) To demonstrate how representative the temperature difference between the two satellite products is of Delta T; (3) To apply bias adjustments and to device a comprehensive treatment of the behavior of the temperature difference across the oceanic skin layer to determine the best method for blending thermal infrared

  1. Polarization Imaging over Sea Surface - A Method for Measurements of Stokes Components Angular Distribution

    NASA Astrophysics Data System (ADS)

    Freda, W.; Piskozub, J.; Toczek, H.

    2015-12-01

    This article describes a method for determining the angular distribution of light polarization over a roughened surface of the sea. Our method relies on measurements of the Stokes vector elements using a polarization imaging camera that operates using the Division of Focal Plane (DoFP) method. It uses special monochrome CCD array in which the neighbouring cells, instead of recording different colours (red green and blue), are equipped with micropolarizers of four directions (0, 45, 90 and 135 degrees). We combined the camera with a fish-eye lens of Field of View (FoV) > 180 deg. Such a large FoV allowed us to crop out the fragment of the frame along the circular horizon, showing a view covering all directions of the hemisphere. Because of complicated optical design of the fish-eye lens (light refraction on surfaces of parts of the lens) connected to the sensor we checked the accuracy of the measurement system. A method to determine the accuracy of measured polarization is based on comparison of the experimentally obtained rotation matrix with its theoretical form. Such a comparison showed that the maximum error of Stokes vector elements depended on zenith angle and reached as much as 24% for light coming from just above the horizon, but decreased rapidly with decreasing zenith angle to the value of 12% for the angles 10° off the edge of FoV. Moreover we present the preliminary results prepared over rough sea surface. These results include total intensity of light, Degree of Linear Polarization (DoLP) and their standard deviations. The results have been averaged over one thousand frames of a movie. These results indicate that the maximum polarization is observed near the reflection of the sun, and the signal coming from below the surface may be observed at zenith angles far from the vertical direction.

  2. Sea Surface Salinity and Wind Retrieval Algorithm Using Combined Passive-Active L-Band Microwave Data

    NASA Technical Reports Server (NTRS)

    Yueh, Simon H.; Chaubell, Mario J.

    2011-01-01

    Aquarius is a combined passive/active L-band microwave instrument developed to map the salinity field at the surface of the ocean from space. The data will support studies of the coupling between ocean circulation, the global water cycle, and climate. The primary science objective of this mission is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean with a spatial resolution of 150 kilometers and a retrieval accuracy of 0.2 practical salinity units globally on a monthly basis. The measurement principle is based on the response of the L-band (1.413 gigahertz) sea surface brightness temperatures (T (sub B)) to sea surface salinity. To achieve the required 0.2 practical salinity units accuracy, the impact of sea surface roughness (e.g. wind-generated ripples and waves) along with several factors on the observed brightness temperature has to be corrected to better than a few tenths of a degree Kelvin. To the end, Aquarius includes a scatterometer to help correct for this surface roughness effect.

  3. Assessment of the Aquarius Space-borne Sea Surface Salinity Retrievals in Polar Ocean

    NASA Astrophysics Data System (ADS)

    Dinnat, E.; Brucker, L.; Caraballo Álvarez, I. O.

    2014-12-01

    Ocean salinity and temperature drive the thermohaline circulation and play a key role in the ocean-atmosphere coupling. With the availability of passive L-band (1.4 GHz) space-borne observations, Sea Surface Salinity (SSS) can be monitored globally at weekly time scales. SSS in the polar regions may be used to better constrain deep water formation, and to monitor changes due to freshening by the melting cryosphere. However, SSS remote sensing in the polar oceans is challenging because L-band radiometric observations are less sensitive to salinity in cold waters, SSS retrieval is less accurate for very rough seas and the presence of sea ice, icebergs and land in the radiometer field of view adds complexity to the retrieval process. Aquarius is a NASA space-borne instrument operating three L-band radiometers. While Aquarius SSS retrievals are performed with a good accuracy in tropical and mid-latitude oceans, a thorough assessment has not been performed in the colder waters of the polar oceans. To assess Aquarius data at high latitudes, we compare them to in-situ measurements from ship cruises. In the northern hemisphere, cruises between Denmark and Greenland are used. In the south, we use cruises in the Austral Ocean between Tasmania and Antarctica. These quality-controlled shipborne measurements (more extensive than the Argo profiling floats which are rare at high latitudes) allow us to assess Aquarius SSS over long transects, repeated weekly or monthly, over the three year period during which Aquarius has been operating. Our results show that significant contamination of SSS retrievals by ice and land are observed, despite the correction for land contamination applied in the Aquarius retrieval algorithm. Such long track comparisons with ship data will help refine the future versions of Aquarius space-borne products. Nonetheless, excluding the data contaminated by land or ice, the agreement with ship data is good. Specifically, the standard deviation is ~0.3 - 0

  4. AQUARIUS: A Passive/Active Microwave Sensor to Monitor Sea Surface Salinity Globally from Space

    NASA Technical Reports Server (NTRS)

    LeVine, David; Lagerloef, Gary S. E.; Colomb, F. Raul; Chao, Yi

    2004-01-01

    Salinity is important for understanding ocean dynamics, energy exchange with the atmosphere and the global water cycle. Existing data is limited and much of the ocean has never even been sampled. Sea surface salinity can be measured remotely by satellite and a three year mission for this purpose called AquariudSAC-D has recently been selected by NASA's Earth System Science Pathfinder (ESSP) program. The objective is to map the salinity field globally with a spatial resolution of 100 km and a monthly average accuracy of 0.2 psu. The mission, scheduled for launch in 2008, is a partnership of the United States National Aeronautics and Space Agency (NASA) and the Argentine Comision National de Actividades Epaciales (CONAE).

  5. Microwave emission measurements of sea surface roughness, soil moisture, and sea ice structure

    NASA Technical Reports Server (NTRS)

    Gloersen, P.; Wilheit, T. T.; Schmugge, T. J.

    1972-01-01

    In order to demonstrate the feasibility of the microwave radiometers to be carried aboard the Nimbus 5 and 6 satellites and proposed for one of the earth observatory satellites, remote measurements of microwave radiation at wavelengths ranging from 0.8 to 21 cm have been made of a variety of the earth's surfaces from the NASA CV-990 A/C. Brightness temperatures of sea water surfaces of varying roughness, of terrain with varying soil moisture, and of sea ice of varying structure were observed. In each case, around truth information was available for correlation with the microwave brightness temperature. The utility of passive microwave radiometry in determining ocean surface wind speeds, at least for values higher than 7 meters/second has been demonstrated. In addition, it was shown that radiometric signatures can be used to determine soil moisture in unvegetated terrain to within five percentage points by weight. Finally, it was demonstrated that first year thick, multi-year, and first year thin sea ice can be distinguished by observing their differing microwave emissivities at various wavelengths.

  6. Microwave emission from polar firn

    NASA Technical Reports Server (NTRS)

    Chang, A. T. C.; Choudhury, B. J.

    1978-01-01

    The microwave emission from a half-space medium, characterized by coordinate dependent scattering and absorbing centers, was calculated by numerically solving the radiative transfer equation by the method of invariant imbedding. Rayleigh scattering phase functions and scattering induced polarization of the radiation were included in the calculation. Using the scattering and extinction data of polar firn the brightness temperature was calculated for the 1.55 cm wavelength. This study was the first quantitative comparison of the results of numerical calculation using the actual measured information of crystal size with the observed data.

  7. Passive microwave airborne measurements of the sea surface response at 89 and 157 GHz

    NASA Astrophysics Data System (ADS)

    Guillou, C.; English, S. J.; Prigent, C.; Jones, D. C.

    1996-02-01

    Microwave measurements of the ocean-roughened surface have been collected during several recent international experiments using an airborne radiometer observing at 89 and 157 GHz. The purpose of this project is to test and validate the sea emissivity model required for the future humidity sounder, advanced microwave sounder unit B, over a wide range of atmospheric and surface conditions. In this paper, the measurements are statistically analyzed and compared with a geometric optics model with special emphasis on the sensitivity to the input parameters. This model is shown to provide good overall agreement with the data when coupled to the wave slope description of Cox and Munk (1954), the liquid water dielectric permittivity of Liebe et al. (1991), and the foam coverage of Monahan and Lu (1990), after increasing the theoretical predictions by a bias of about 2.5 K at 89 GHz and 1.7 K at 157 GHz. In addition, an empirical emissivity algorithm derived from low-frequency observations (Hollinger, 1971; Stogryn, 1972) and widely used for satellite retrieval purposes is shown to be inappropriate for use at millimeter frequencies.

  8. Polarization of Cosmic Microwave Background

    NASA Astrophysics Data System (ADS)

    Buzzelli, A.; Cabella, P.; de Gasperis, G.; Vittorio, N.

    2016-02-01

    In this work we present an extension of the ROMA map-making code for data analysis of Cosmic Microwave Background polarization, with particular attention given to the inflationary polarization B-modes. The new algorithm takes into account a possible cross- correlated noise component among the different detectors of a CMB experiment. We tested the code on the observational data of the BOOMERanG (2003) experiment and we show that we are provided with a better estimate of the power spectra, in particular the error bars of the BB spectrum are smaller up to 20% for low multipoles. We point out the general validity of the new method. A possible future application is the LSPE balloon experiment, devoted to the observation of polarization at large angular scales.

  9. Sea-surface temperature fronts in the Yellow and East China Seas from TRMM microwave imager data

    NASA Astrophysics Data System (ADS)

    Huang, Daji; Zhang, Tao; Zhou, Feng

    2010-06-01

    Swath data from the Tropical Rainfall Measuring Mission microwave imager of sea-surface temperatures (SST) from 1998 to 2005 have been used to analyze the climatology and seasonal variability of the SST fronts in the Yellow and East China Seas (YES). Seven fronts have been identified and placed into three categories, namely, (1) the shelf-break front (Kuroshio Front), (2) the coastal fronts (Zhe-Min, Jiangsu, Shangdong Peninsula, Western Korean, and Western Chejudo Fronts), and (3) the shelf front (Western Yellow Sea Shelf Front). The Kuroshio Front exists from December through May, with the maximum SST gradient and highest frontal probability in April. The five coastal fronts exist year-round, all with their maximum SST gradient and highest frontal probability in February. The shelf front in the western Yellow Sea exists only from January to March. Frontogenesis in winter is due to effects of both air-sea heat exchange and advection by currents. The coastal fronts in the stratified months are expressed as tidal fronts. The coastal frontal zones coincide with the major spawning grounds of fish in the YES. The overwintering fishery ground in the Yellow Sea overlaps with the narrow band of favorable water temperature in the frontal zone. The overwintering grounds in the East China Sea are broad and bounded by fronts.

  10. Estimating Longwave Net Radiation at Sea Surface from the Special Sensor Microwave/Imager (SSM/I).

    NASA Astrophysics Data System (ADS)

    Liu, Quanhua; Simmer, Clemens; Ruprecht, Eberhard

    1997-07-01

    A neural network is used to calculate the longwave net radiation (Lnet) at the sea surface from measurements of the Special Sensor Microwave/Imager (SSM/I). The neural network applied in this study is able to account largely for the nonlinearity between Lnet and the satellite-measured brightness temperatures (TB). The algorithm can be applied for instantaneous measurements over oceanic regions with the area extent of satellite passive microwave observations (30-60 km in diameter). Comparing with a linear regression method the neural network reduces the standard error for Lnet from 17 to 5 W m2 when applied to model results. For clear-sky cases, a good agreement with an error of less than 5 W m2 for Lnet between calculations from SSM/I observations and pyrgeometer measurements on the German research vessel Poseidon during the International Cirrus Experiment (ICE) 1989 is obtained. For cloudy cases, the comparison is problematic due to the inhomogenities of clouds and the low and different spatial resolutions of the SSM/I data. Global monthly mean values of Lnet for October 1989 are computed and compared to other sources. Differences are observed among the climatological values from previous studies by H.-J. Isemer and L. Hasse, the climatological values from R. Lindau and L. Hasse, the values of W. L. Darnell et al., and results from this study. Some structures of Lnet are similar for results from W. L. Darnell et al. and the present authors. The differences between both results are generally less than 15 W m2. Over the North Atlantic Ocean the authors found a poleward increase for Lnet, which is contrary to the results of H.-J. Isemer and L. Hasse.

  11. Polar low climatology over the Nordic and Barents seas based on satellite passive microwave data

    NASA Astrophysics Data System (ADS)

    Smirnova, Julia E.; Golubkin, Pavel A.; Bobylev, Leonid P.; Zabolotskikh, Elizaveta V.; Chapron, Bertrand

    2015-07-01

    A new climatology of polar lows over the Nordic and Barents seas for 14 seasons (1995/1996-2008/2009) is presented. For the first time in climatological studies of polar lows an approach based on satellite passive microwave data was adopted for polar low identification. A total of 637 polar lows were found in 14 extended winter seasons by combining total atmospheric water vapor content and sea surface wind speed fields retrieved from Special Sensor Microwave/Imager data. As derived, the polar low activity in the Norwegian and Barents Seas is found to be almost equal, and the main polar low genesis area is located northeastward of the North Cape. For the Barents Sea, a significant correlation is found between the number of polar lows and mean sea ice extent. Individual indicative polar low characteristics (i.e., diameter, lifetime, distance traveled, translation speed, and maximum wind speed) are also presented.

  12. Comparison of sea surface winds derived from active and passive microwaves instruments on the Mediterranean Sea

    NASA Astrophysics Data System (ADS)

    De Biasio, Francesco; Zecchetto, Stefano

    2013-04-01

    In order to characterize the energy and momentum fluxes at the air-sea interface, the surface wind vector must be known with adequate spatial and temporal coverages. Satellite-borne active and passive microwaves instruments perform such measurements. In the Mediterranean Sea, and in general in enclosed or semi-enclosed basins, an adequate coverage is yet more difficult to achieve than in open sea, because of the presence of vast coastal areas and elevated orography near the coastline. This study aims to compare the performance of three of such instruments (two actives and one passive) over several years of activity over the Mediterranean Sea, in order to delve into the possibility of using the three data-sets as a common reference for marine meteorology investigations, dramatically improving the availability of surface wind data in the Mediterranean Sea. They are the METOP-A ASCAT scatterometer, the QuikSCAT SeaWinds scatterometer and the Coriolis WindSat radiometer. ASCAT and QuikSCAT data are freely available for download, at spatial resolution of 25 km by 25 km and 12.5 km by 12.5 km, from the Physical Oceanography Distributed Active Archive Center PO.DAAC (http://podaac.jpl.nasa.gov). ASCAT near real time data have 2 hours latency. The time span covered by these data is March 2007-present for ASCAT, July 1999-November 2009 for QuikSCAT. In the Mediterranean Sea the nominal temporal coverage is less then 2 hit per point per day for both. WindSat data have spatial resolution of 25 km by 25 km, cover the period February 2003-present, and are freely available for download from Remote Sensing Systems (http://www.ssmi.com). They are available as delayed datasets covering one day at a time. The two collocated datasets cover the period February 2003 - November 2009 (WindSat - QuikSCAT) and March 2009 - November 2010 (WindSat - ASCAT), and offer the means to perform: - a comparison of the performances of active and passive microwaves instruments; - a very long

  13. Comparison of sea surface wind speed fields by SEASAT radar altimeter, scatterometer and scanning multichannel microwave radiometer with an emphasis on the Southern Ocean

    NASA Technical Reports Server (NTRS)

    Mognard, N. M.; Campbell, W. J.

    1984-01-01

    The SEASAT altimeter (ALT), scatterometer (SASS), and scanning microwave multichannel radiometer (SMMR) measured sea surface wind speed. During the satellite lifetime from June to October 1978, the Austral winter, the highest wind speeds were recorded in the Southern Ocean. Three-month, monthly, and three-day surface wind speed fields deduced from the three Seasat wind speed sensors are compared. The monthly and three-day fields show a pronounced mesoscale (1000 km) variability in wind speed. At all space and time scales analyzed, differences of 40% are found in the magnitude of the wind speed features, with the ALT consistently yielding the lowest wind speed and the SMMR the highest.

  14. Experimental measurement and theoretical modeling of microwave scattering and the structure of the sea surface influencing radar observations from space

    NASA Technical Reports Server (NTRS)

    Arnold, David; Kong, J. A.

    1992-01-01

    The electromagnetic (EM) bias 'epsilon' is an error present in radar altimetry of the ocean due to the nonuniform reflection from wave troughs and crests. The EM bias is defined as the difference between the mean reflecting surface and the mean sea surface. A knowledge of the EM bias is necessary to permit error reduction in mean sea level measurements by satellite radar altimeters. Direct measurements of the EM bias were made from a Shell Offshore oil production platform in the Gulf of Mexico for a six month period during 1989 and 1990. Measurements of the EM bias were made at 5 and 14 Ghz. During the EM bias experiments by Melville et al., a wire wave gauge was used to obtain the modulation of the high frequency waves by the low frequency waves. It became apparent that the EM bias was primarily caused by the modulation of the short waves. This was reported by Arnold et al. The EM bias is explained using physical optics scattering and an empirical model for the short wave modulation. Measurements of the short wave modulation using a wire wave gauge demonstrated a linear dependence of the normalized bias on the short wave modulation strength, M. The theory accurately predicts this dependence by the relation epsilon = -alphaMH sub 1/3. The wind speed dependence of the normalized bias is explained by the dependence of the short wave modulation strength on the wind speed. While other effects such as long wave tilt and curvature will have an effect on the bias, the primary cause of the bias is shown to be due to the short wave modulation. This report will present a theory using physical optics scattering and an empirical model of the short wave modulation to estimate the EM bias. The estimated EM bias will be compared to measurements at C and Ku bands.

  15. Cosmic Microwave Background Polarization and Inflation

    NASA Technical Reports Server (NTRS)

    Chuss, David T.

    2011-01-01

    Measurements of the cosmic microwave background (CMB) offer a means to explore the universe at a very early epoch. Specifically, if the universe went through a brief period of exponential expansion called inflation as current data suggest, gravitational waves from this period would polarize the CMB in a specific pattern. At GSFC, we are currently working towards two experiments that work in concert to measure this polarization pattern in search of evidence for inflation. The Cosmology Large Angular Scale Surveyor (CLASS) will measure the polarization at frequencies between 40 and 150 GHz from the Atacama Desert in Chile. The Primordial Inflation Polarization Explorer (PIPER) is a balloon-borne experiment that will make similar measurements at frequencies between 200 and 600 GHz.

  16. The POLARBEAR Cosmic Microwave Background Polarization Experiment

    NASA Astrophysics Data System (ADS)

    Barron, D.; Ade, P.; Anthony, A.; Arnold, K.; Boettger, D.; Borrill, J.; Chapman, S.; Chinone, Y.; Dobbs, M.; Edwards, J.; Errard, J.; Fabbian, G.; Flanigan, D.; Fuller, G.; Ghribi, A.; Grainger, W.; Halverson, N.; Hasegawa, M.; Hattori, K.; Hazumi, M.; Holzapfel, W.; Howard, J.; Hyland, P.; Jaehnig, G.; Jaffe, A.; Keating, B.; Kermish, Z.; Keskitalo, R.; Kisner, T.; Lee, A. T.; Le Jeune, M.; Linder, E.; Lungu, M.; Matsuda, F.; Matsumura, T.; Meng, X.; Miller, N. J.; Morii, H.; Moyerman, S.; Myers, M.; Nishino, H.; Paar, H.; Peloton, J.; Quealy, E.; Rebeiz, G.; Reichardt, C. L.; Richards, P. L.; Ross, C.; Shimizu, A.; Shimmin, C.; Shimon, M.; Sholl, M.; Siritanasak, P.; Spieler, H.; Stebor, N.; Steinbach, B.; Stompor, R.; Suzuki, A.; Tomaru, T.; Tucker, C.; Yadav, A.; Zahn, O.

    2014-09-01

    The polarbear cosmic microwave background (CMB) polarization experiment has been observing since early 2012 from its 5,200 m site in the Atacama Desert in Northern Chile. polarbear's measurements will characterize the expected CMB polarization due to gravitational lensing by large scale structure, and search for the possible B-mode polarization signature of inflationary gravitational waves. polarbear's 250 mK focal plane detector array consists of 1,274 polarization-sensitive antenna-coupled bolometers, each with an associated lithographed band-defining filter and contacting dielectric lenslet, an architecture unique in current CMB experiments. The status of the polarbear instrument, its focal plane, and the analysis of its measurements are presented.

  17. Cosmological spatial curvature probed by microwave polarization

    SciTech Connect

    Matzner, R.A.; Tolman, B.W.

    1982-11-15

    If there is a large-scale anisotropy in the expansion of the universe, the microwave background radiation is expected to be linearly polarized. This communication shows that spatial curvature is capable of rotating the polarization of the microwaves relative to its direction at last scattering, which is directly correlated with the expansion anisotropy (and so also the observed intensity anisotropy). In Friedmann-Robertson-Walker models of the universe with additional small expansion anisotropy, the observed rotation relative to the intensity anisotropy would be appreciable and constant over the celestial sphere in the closed (type IX) model, but in the flat and open models, it must either vanish (types I and V) or vary ina complicated way over the celestial sphere (type VII/sub h/). These facts suggest a clear observational test of the closure of the universe. Also, an ambiguity inherent in the homogeneity of the universe does not allow prediction of the direction of rotation; thus homogeneous universes possess a property which might be called ''handedness.''

  18. Characterization of sun and sky glint from wind ruffled sea surfaces for improved estimation of polarized remote sensing reflectance

    NASA Astrophysics Data System (ADS)

    Foster, Robert; Ibrahim, Amir; Gilerson, Alex; El-Habashi, Ahmed; Carrizo, Carlos; Ahmed, Sam

    2015-09-01

    During two cruises in 2014, the polarized radiance of the ocean and the sky were continuously acquired using a HyperSAS-POL system. The system consists of seven hyperspectral radiometric sensors, three of which (one unpolarized and two polarized) look at the water and similarly three at the sky. The system autonomously tracks the Sun position and the heading of the research vessel to which it is attached in order to maintain a fixed relative azimuth angle with respect to the Sun (i.e. 90°) and therefore avoid the specular reflection of the sunlight. For the duration of both cruises, (NASA Ship Aircraft Bio-Optical Research (SABOR), and NOAA VIIRS Validation/Calibration), in situ inherent optical properties (IOPs) were continuously acquired using a set of instrument packages modified for underway measurement, and hyperspectral radiometric measurements were taken manually at all stations. During SABOR, an underwater polarimeter was deployed when conditions permitted. All measurements were combined in an effort to first develop a glint (sky + Sun) correction scheme for the upwelling polarized signal from a wind driven ocean surface and compare with one assuming that the ocean surface is flat.

  19. Optically Transparent Microwave Polarizer Based On Quasi-Metallic Graphene.

    PubMed

    Grande, Marco; Bianco, Giuseppe Valerio; Vincenti, Maria Antonietta; de Ceglia, Domenico; Capezzuto, Pio; Scalora, Michael; D'Orazio, Antonella; Bruno, Giovanni

    2015-01-01

    In this paper, we report on the engineering and the realization of optically transparent graphene-based microwave devices using Chemical Vapour Deposition (CVD) graphene whose sheet resistance may be tailored down to values below 30 Ω/sq. In particular, we show that the process was successfully used to realize and characterize a simple, optically transparent graphene-based wire-grid polarizer at microwave frequencies (X band). The availability of graphene operating in a quasi-metallic region may allow the integration of graphene layers in several microwave components, thus leading to the realization of fully transparent (and flexible) microwave devices. PMID:26603112

  20. Optically Transparent Microwave Polarizer Based On Quasi-Metallic Graphene

    PubMed Central

    Grande, Marco; Bianco, Giuseppe Valerio; Vincenti, Maria Antonietta; de Ceglia, Domenico; Capezzuto, Pio; Scalora, Michael; D’Orazio, Antonella; Bruno, Giovanni

    2015-01-01

    In this paper, we report on the engineering and the realization of optically transparent graphene-based microwave devices using Chemical Vapour Deposition (CVD) graphene whose sheet resistance may be tailored down to values below 30 Ω/sq. In particular, we show that the process was successfully used to realize and characterize a simple, optically transparent graphene-based wire-grid polarizer at microwave frequencies (X band). The availability of graphene operating in a quasi-metallic region may allow the integration of graphene layers in several microwave components, thus leading to the realization of fully transparent (and flexible) microwave devices. PMID:26603112

  1. Microwave frequency modulation for improving polarization transfer in DNP experiments

    NASA Astrophysics Data System (ADS)

    Guy, Mallory; Ramanathan, Chandrasekhar

    Dynamic nuclear polarization (DNP) is a driven process that transfers the inherently high electron polarization to surrounding nuclear spins via microwave irradiation at or near the electron Larmor frequency. In a typical DNP experiment, the amplitude and frequency of the applied microwaves are constant. However, by adding time dependence in the form of frequency modulation, the electron excitation bandwidth is increased, thereby increasing the number of electron spins active in the polarization transfer process and improving overall efficiency. Both triangular and sinusoidal modulation show a 3 fold improvement over monochromatic irradiation. In the present study, we compare the nuclear spin polarization after DNP experiments with no modulation of the applied microwaves, triangular and sinusoidal modulation, and modulation schemes derived from the sample's ESR spectrum. We characterize the polarization as a function of the modulation amplitude and frequency and compare the optimal results from each modulation scheme. Working at a field of 3.34 T and at a temperature of 4 K, we show that by using a modulation scheme tailored to the electronic environment of the sample, polarization transfer is improved over other modulation schemes. Small-scale simulations of the spin system are developed to gain further insight into the dynamics of this driven open system. This understanding could enable the design of modulation schemes to achieve even higher polarization transfer efficiencies. With support from NSF (CHE-1410504) and by NIH (U19-A1091173).

  2. Cross-polarized microwave surface-state anti-resonance

    NASA Astrophysics Data System (ADS)

    Appelbaum, Ian

    2014-08-01

    We propose a polarization-sensitive measurement of microwave electromagnetic resonances in a static magnetic field to detect the metallic surface state of a bulk insulator. A quantitative model is used to demonstrate that a unique, unambiguous signature of the dissipative but conducting surface can be seen in the orthogonally polarized transmission spectra. These results are relevant to the ongoing search for candidate topological insulator materials.

  3. Sea surface wind field by TerraSAR-X and Tandem-X data

    NASA Astrophysics Data System (ADS)

    Li, Xiaoming; Lehner, Susanne

    2013-04-01

    A new Geophysical Model Function (GMF), denoted XMOD2, is developed to retrieve the sea surface wind field from X-band TerraSAR-X/Tandem-X (TS-X/TD-X) data. In contrary to the previous XMOD1, XMOD2 is based on a nonlinear GMF, and moreover it also depicts the difference between upwind and downwind of the sea surface backscatter. By exploiting 371 collocations, the retrieved TS-X/TD-X sea surface wind speed U10 by XMOD2 agrees well with in situ buoy measurements with a bias of 0.39 m/s, an RMSE of 1.52 m/s and a scatter index (SI) of 16.1%. To apply XMOD2 to TS-X/TD-X data acquired at HH polarization, we verify the X-band SAR Polarization Ratio (PR) models by comparing the retrieved sea surface wind speed to in situ buoy measurements as well. Based on 62 collocated pairs, it is found that by using the Elfouhaily type PR model and XMOD2 yields better U10 retrieval with a bias of -0.27 m/s, an RMSE of 2.06 m/s and a SI of 22.7% than using the X-PR model which yields a bias of -0.98 m, and RMSE of 2.30 m and a SI of 23.4%. Several TerraSAR-X and TanDEM-X ScanSAR images are acquired in October, 2012 to track the Hurricane Sandy. Three of the images are acquired in the open sea, which are presented in this chapter to demonstrate observations of sea surface wind and wave extracted from X-band ScanSAR image with high spatial resolution of 17 m in the hurricane. In the case of the TerraSAR-X image acquired on October 26, 2012, we analyze the peak wave direction and length of swell generated by Hurricane Sandy, as well as interaction of swell with the Abaco Island, Bahamas. In the other two cases, sea surface wind field derived from the TerraSAR-X and TanDEM-X acquired on October 27 and 28 are presented. The sea surface wind speed retrieved by the X-band Geophysical Model Function (GMF) XMOD2 using wind direction derived from SAR images and the NOAA Hurricane Research Division (HRD) wind analyses are both presented for comparisons. We also compare the retrieved sea surface

  4. Polarized cosmic microwave background map recovery with sparse component separation

    NASA Astrophysics Data System (ADS)

    Bobin, J.; Sureau, F.; Starck, J.-L.

    2015-11-01

    The polarization modes of the cosmological microwave background are an invaluable source of information for cosmology and a unique window to probe the energy scale of inflation. Extracting this information from microwave surveys requires distinguishing between foreground emissions and the cosmological signal, which means solving a component separation problem. Component separation techniques have been widely studied for the recovery of cosmic microwave background (CMB) temperature anisotropies, but very rarely for the polarization modes. In this case, most component separation techniques make use of second-order statistics to distinguish between the various components. More recent methods, which instead emphasize the sparsity of the components in the wavelet domain, have been shown to provide low-foreground, full-sky estimates of the CMB temperature anisotropies. Building on sparsity, we here introduce a new component separation technique dubbed the polarized generalized morphological component analysis (PolGMCA), which refines previous work to specifically work on the estimation of the polarized CMB maps: i) it benefits from a recently introduced sparsity-based mechanism to cope with partially correlated components; ii) it builds upon estimator aggregation techniques to further yield a better noise contamination/non-Gaussian foreground residual trade-off. The PolGMCA algorithm is evaluated on simulations of full-sky polarized microwave sky simulations using the Planck Sky Model (PSM). The simulations show that the proposed method achieves a precise recovery of the CMB map in polarization with low-noise and foreground contamination residuals. It provides improvements over standard methods, especially on the Galactic center, where estimating the CMB is challenging.

  5. Combined study of microwave-power-dependence and linear-polarization-dependence of the microwave-radiation-induced magnetoresistance oscillations

    NASA Astrophysics Data System (ADS)

    Ye, Tianyu; Liu, Han-Chun; Mani, Ramesh; Wegscheider, Werner; Georgia State University Collaboration; ETH Zurich Collaboration

    2014-03-01

    Microwave radiation induced magnetoresistance oscillations (MRIMOs) represent an interesting electrical property of the high mobility two dimensional electron gas (2DEG) at low temperatures in a perpendicular magnetic field and under microwave excitation. Some questions under discussion in this topic include: (a) whether MRIMOs' amplitudes grow linearly with the microwave power and (b) how the MRIMO amplitudes change with the rotation of the microwave polarization with respect to the sample. In this study, we utilize swept microwave power and continuously changed linear polarized microwave polarization angle as two variables in four-terminal low-frequency lock-in magnetoresistance measurements of the 2DEG samples. The results show that amplitude of MRIMOs varies non-linearly with the microwave power. Also, the microwave polarization dependence measurements show that MRIMOs depend sensitively on the polarization angle of the linearly polarized microwaves, while the oscillatory magnetoresistance follows a cosine square function of the polarization angle. We provide a simple model that conveys our understanding of our observations. Basic research at Georgia State University is supported by the DOE-BES, MSE Division under DE-SC0001762. Microwave work is supported by the ARO under W911NF-07-01-0158.

  6. Recovering Microwave Cross-Polarization Losses

    NASA Technical Reports Server (NTRS)

    Seidel, B. L.; Stelzried, C. T.; Ohlson, J. E.

    1985-01-01

    Reception improved by adding normally discarded portion of signal. For signal enhancement, major and minor signals combined in slaved closedloop receiver channels. Both receiver channels served by common local oscillator controlled by phase-locked loop in main channel. 10-MHz intermediate-frequency (IF) signals of channels coherently summed. For polarization tracking, phasemeter added to measure phase difference between points A and B. With new circuit, low-level signal used at receiver to augment main signal.

  7. Dipole modulation of cosmic microwave background temperature and polarization

    NASA Astrophysics Data System (ADS)

    Ghosh, Shamik; Kothari, Rahul; Jain, Pankaj; Rath, Pranati K.

    2016-01-01

    We propose a dipole modulation model for the Cosmic Microwave Background Radiation (CMBR) polarization field. We show that the model leads to correlations between l and l+1 multipoles, exactly as in the case of temperature. We obtain results for the case of TE, EE and BB correlations. An anisotropic or inhomogeneous model of primordial power spectrum which leads to such correlations in temperature field also predicts similar correlations in CMBR polarization. We analyze the CMBR temperature and polarization data in order to extract the signal of these correlation between l and l+1 multipoles. Our results for the case of temperature using the latest PLANCK data agree with those obtained by an earlier analysis. A detailed study of the correlation in the polarization data is not possible at present. Hence we restrict ourselves to a preliminary investigation in this case.

  8. Cosmic microwave background polarization signals from tangled magnetic fields.

    PubMed

    Seshadri, T R; Subramanian, K

    2001-09-01

    Tangled, primordial cosmic magnetic fields create small rotational velocity perturbations on the last scattering surface of the cosmic microwave background radiation. For fields which redshift to a present value of B0 = 3 x 10(-9) G, these vector modes are shown to generate polarization anisotropies of order 0.1-4 microK on small angular scales (500polarization, which could help in their detection. PMID:11531471

  9. Airborne antenna polarization study for the microwave landing system

    NASA Technical Reports Server (NTRS)

    Gilreath, M. C.

    1976-01-01

    The feasibility of the microwave landing system (MLS) airborne antenna pattern coverage requirements are investigated for a large commercial aircraft using a single omnidirectional antenna. Omnidirectional antennas having vertical and horizontal polarizations were evaluated at several different station locations on a one-eleventh scale model Boeing 737 aircraft. The results obtained during this experimental program are presented which include principal plane antenna patterns and complete volumetric coverage plots.

  10. Automated Microwave Frequency Control in Dynamic Nuclear Polarization Experiments

    NASA Astrophysics Data System (ADS)

    Scott, Ethan; Johnson, Ian; Keller, Dustin; Solid Polarized Target Group Team

    2016-03-01

    To achieve highest polarization levels in dynamic nuclear polarization (DNP) experiments, target materials must be subjected to microwave irradiation at a particular frequency determined by the difference in the nuclear Larmor and electron paramagnetic resonance (EPR) frequencies. However, this resonant frequency is variable; it drifts as a result of radiation damage. Manually adjusting the frequency to accommodate for this fluctuation can be difficult, and improper adjustments negatively impact the polarization. In response to this problem, a controller has been developed which automates the process of seeking and maintaining optimal frequency. The creation of such a controller has necessitated research into the correlation between microwave frequency and corresponding polarization growth or decay rates in DNP experiments. Knowledge gained from the research of this unique relationship has additionally lead to the development of a Monte-Carlo simulation which accurately models polarization as a function of frequency and a number of other parameters. The simulation and controller continue to be refined, however, recent DNP experimentation has confirmed the controller's effectiveness.

  11. Effects of polarization-charge shielding in microwave heating

    SciTech Connect

    Lin, M. S.; Lin, S. M.; Chiang, W. Y.; Barnett, L. R.; Chu, K. R.

    2015-08-15

    Heating of dielectric objects by radio frequency (RF) and microwaves has long been a method widely employed in scientific research and industrial applications. However, RF and microwave heating are often susceptible to an excessive temperature spread due to uneven energy deposition. The current study elucidates an important physical reason for this difficulty and proposes an effective remedy. Non-spherical samples are placed in an anechoic chamber, where it is irradiated by a traveling microwave wave with 99% intensity uniformity. Polarization charges induced on the samples tend to partially cancel the incident electric field and hence reduce the heating rate. The polarization-charge shielded heating rate is shown to be highly dependent on the sample's shape and its orientation relative to the wave electric field. For samples with a relatively high permittivity, the resultant uneven heating can become a major cause for the excessive temperature spread. It is also demonstrated that a circularly polarized wave, with its rapidly rotating electric field, can effectively even out the heating rate and hence the temperature spread.

  12. Testing cosmic microwave background polarization data using position angles

    NASA Astrophysics Data System (ADS)

    Preece, Michael; Battye, Richard A.

    2014-10-01

    We consider a novel null test for contamination which can be applied to cosmic microwave background (CMB) polarization data that involves analysis of the statistics of the polarization position angles. Specifically, we will concentrate on using histograms of the measured position angles to illustrate the idea. Such a test has been used to identify systematics in the NRAO-VLA Sky Survey point source catalogue with an amplitude well below the noise level. We explore the statistical properties of polarization angles in CMB maps. If the polarization angle is not correlated between pixels, then the errors follow a simple √{N_{pix}} law. However, this is typically not the case for CMB maps since these have correlations which result in an increase in the variance as the effective number of independent pixels is reduced. Then, we illustrate how certain classes of systematic errors can result in very obvious patterns in these histograms, and thus that these errors could possibly be identified using this method. We discuss how this idea might be applied in a realistic context, and make a preliminary analysis of the Wilkinson Microwave Anisotropy Probe 7 data, finding evidence of a systematic error in the Q- and W- band data, consistent with a constant offset in Q and U.

  13. Enhancement of nuclear polarization with frequency modulated microwaves

    SciTech Connect

    Dulya, C.

    1995-04-01

    The authors report their discovery of a gain by a factor of two in the growth rate and of a gain by {approx} 1.7 in the maximum dynamic nuclear polarization (DNP) of deuteron in the large polarized targets of the Spin Muon Collaboration. These large gains resulted from a frequency modulation (FM) of the {approx} 69 GHz microwave field used for DNP; this FM had a 30 MHz amplitude and {approx} 1 KHz frequency. The target material is glassy deuterated 1-butanol doped with a paramagnetic Cr(V) complex. Measurements of the 430 MHz broad electron paramagnetic resonance (EPR) absorption spectrum in the 2.5 T field were performed by a novel differential bolometric technique. They show that FM gives rise to an additional microwave absorption which depends on the amplitude and frequency of FM and which is more pronounced in the edges of the EPR spectrum. For deuterons, polarizations of 0.46 and {minus}0.53 have been obtained. Similar although less dramatic effects were observed for protons where FM increased the polarization by less than 10% and the growth rate by {approx} 20%.

  14. Forward Monte Carlo Computations of Polarized Microwave Radiation

    NASA Technical Reports Server (NTRS)

    Battaglia, A.; Kummerow, C.

    2000-01-01

    Microwave radiative transfer computations continue to acquire greater importance as the emphasis in remote sensing shifts towards the understanding of microphysical properties of clouds and with these to better understand the non linear relation between rainfall rates and satellite-observed radiance. A first step toward realistic radiative simulations has been the introduction of techniques capable of treating 3-dimensional geometry being generated by ever more sophisticated cloud resolving models. To date, a series of numerical codes have been developed to treat spherical and randomly oriented axisymmetric particles. Backward and backward-forward Monte Carlo methods are, indeed, efficient in this field. These methods, however, cannot deal properly with oriented particles, which seem to play an important role in polarization signatures over stratiform precipitation. Moreover, beyond the polarization channel, the next generation of fully polarimetric radiometers challenges us to better understand the behavior of the last two Stokes parameters as well. In order to solve the vector radiative transfer equation, one-dimensional numerical models have been developed, These codes, unfortunately, consider the atmosphere as horizontally homogeneous with horizontally infinite plane parallel layers. The next development step for microwave radiative transfer codes must be fully polarized 3-D methods. Recently a 3-D polarized radiative transfer model based on the discrete ordinate method was presented. A forward MC code was developed that treats oriented nonspherical hydrometeors, but only for plane-parallel situations.

  15. Reconfigurable microwave photonic filter based on polarization modulation

    NASA Astrophysics Data System (ADS)

    Xu, Enming; Pan, Shilong; Li, Peili

    2016-03-01

    A reconfigurable microwave photonic filter based on a polarization modulator (PolM) is proposed and experimentally demonstrated. The PolM together with a polarization controller (PC) and a polarization beam splitter (PBS) implements two complementary intensity modulations in two separated branches. Then, optical components are inserted in the two branches to realize a bandpass filter and an allpass filter, respectively. When the two branches are combined by a second PBS, a filter with a frequency response that equals the subtraction of the frequency responses of the allpass filter and bandpass filter is achieved. By adjusting the PCs placed before the second PBS, a notch filter with a tunable notch depth or a bandpass filter can be achieved.

  16. Microwave-mediated magneto-optical trap for polar molecules

    NASA Astrophysics Data System (ADS)

    Dizhou, Xie; Wenhao, Bu; Bo, Yan

    2016-05-01

    Realizing a molecular magneto-optical trap has been a dream for cold molecular physicists for a long time. However, due to the complex energy levels and the small effective Lande g-factor of the excited states, the traditional magneto-optical trap (MOT) scheme does not work very well for polar molecules. One way to overcome this problem is the switching MOT, which requires very fast switching of both the magnetic field and the laser polarizations. Switching laser polarizations is relatively easy, but fast switching of the magnetic field is experimentally challenging. Here we propose an alternative approach, the microwave-mediated MOT, which requires a slight change of the current experimental setup to solve the problem. We calculate the MOT force and compare it with the traditional MOT and the switching MOT scheme. The results show that we can operate a good MOT with this simple setup. Project supported by the Fundamental Research Funds for the Central Universities of China.

  17. The Cosmic Microwave Background Radiation and its Polarization

    NASA Astrophysics Data System (ADS)

    Wollack, Edward

    2016-03-01

    The cosmic microwave background (CMB) radiation and its faint polarization have provided a unique means to constrain the physical state of the early Universe. Continued advances in instrumentation, observation, and analysis have revealed polarized radiation signatures associated with gravitational lensing and have heightened the prospects for using precision polarimetry to experimentally confront the inflationary paradigm. Characterization of this relic radiation field has the power to constrain or reveal the detailed properties of astroparticle species and long wave gravitational radiation. On going and planned CMB polarization efforts from the ground, balloon, and space borne platforms will be briefly surveyed. Recent community activities by the Inflation Probe Science Interest Group (IPSIG) will also be summarized. NASA PCOS mini-symposium (invited IPSIG talk).

  18. Searching for Faraday rotation in cosmic microwave background polarization

    NASA Astrophysics Data System (ADS)

    Ruiz-Granados, B.; Battaner, E.; Florido, E.

    2016-08-01

    We use the Wilkinson Microwave Anisotropy Probe (WMAP) 9th-year foreground reduced data at 33, 41 and 61 GHz to derive a Faraday rotation at map and at angular power spectrum levels taking into account their observational errors. A processing mask provided by WMAP is used to avoid contamination from the disc of our Galaxy and local spurs. We have found a Faraday rotation component at both, map and power spectrum levels. The lack of correlation of the Faraday rotation with Galactic Faraday rotation, synchrotron and dust polarization from our Galaxy or with cosmic microwave background anisotropies or lensing suggests that it could be originated at reionization (ℓ ≲ 12). Even if the detected Faraday rotation signal is weak, the present study could contribute to establish magnetic fields strengths of B0 ˜ 10-8 G at reionization.

  19. Estimation of sea-surface winds using backscatter cross-section measurements from airborne research weather radar

    SciTech Connect

    Hildebrand, P.H. . Remote Sensing Facility)

    1994-01-01

    A technique is presented for estimation of sea-surface winds using backscatter cross-section measurements from an airborne research weather radar. The technique is based on an empirical relation developed for use with satellite-borne microwave scatterometers which derives sea-surface winds from radar backscatter cross-section measurements. Unlike a scatterometer, the airborne research weather radar is a Doppler radar designed to measure atmospheric storm structure and kinematics. Designed to scan the atmosphere, the radar also scans the ocean surface over a wide range of azimuths, with the incidence angle and polarization angle changing continuously during each scan. The new sea-surface wind estimation technique accounts for these variations in incidence angle and polarization and derives the atmospheric surface winds. The technique works well over the range of wind conditions over which the wind speed-backscatter cross-section relation holds, about 2--20 m/s. The problems likely to be encountered with this new technique are evaluated and it is concluded that most problems are those which are endemic to any microwave scatterometer wind estimation technique. The new technique will enable using the research weather radar to provide measurements which would otherwise require use of a dedicated scatterometer.

  20. Measuring the Cosmic Microwave Background Polarization with SPT-POL

    NASA Astrophysics Data System (ADS)

    Crites, Abigail; SPT-POL Collaboration

    2013-01-01

    A new polarization-sensitive camera, SPT-POL, designed to measure the polarization of the cosmic microwave background (CMB), was deployed on the 10 meter South Pole Telescope in January 2012. The goal of the project is to exploit the high resolution of the telescope (1 arcminute beam) and the high sensitivity afforded by the 1536 detector camera to characterize the B-mode polarization induced by the gravitational lensing of the primordial E-mode CMB polarization, as well as to detect or set an upper limit on the level of the B-mode polarization from inflationary gravitational waves. The lensing B-modes will be used to constrain the sum of the neutrino masses by measuring large scale structure, while the inflationary B-modes are sensitive to the energy scale of inflation. I will discuss the development of the SPT-POL camera including the cryogenic design and the transition edge sensor (TES) detectors as well as the science goals and status of the ongoing of the SPT-POL program.

  1. Analysis and Modelling of Sea-Surface Doppler Spectra

    NASA Astrophysics Data System (ADS)

    Fois, F.; Hoogeboom, P.; Le Chevalier, F.; Stoffelen, A.

    2012-12-01

    The modelling of the Doppler spectrum of a time-varying ocean surface has gained considerable attention in the last decades. Knowledge of how the evolution of the ocean surface wave spectrum affects the scattered electromagnetic field is essential for a quantitative understanding of the properties of the measured microwave Doppler spectra. Complicated hydrodynamics, influencing the motion of the ocean surface waves, make this understanding significantly difficult. Non linear hydrodynamics couple the motion of the large and small waves and, consequently, change statistical characteristics and shapes of the surface-wave components. These hydrodynamic surface interactions are not included in the simplest linear sea-surface model, which assumes that each surface harmonic propagates according to the dispersion relation typical of water waves. In the past decades, Bass [1968] and Barrick [1972] used a surface perturbation theory to predict the Doppler spectra; Valenzuela and Laing [1970], instead, obtained similar results by using a composite surface model. Later, Doppler spectra were studied by Thompson [1989], who computed the spectra using a time-dependent composite model. Zavorotny and Voronovich [1998] made use of an approximate "two-scale" surface model based on a directional wave spectrum. However, currently available analytical scattering models are unreliable at high incidence angles and do not provide a full-polarimetric information. Exact numerical simulations of microwave scattering from time-varying ocean-like surfaces are highly recommended to eliminate concerns on the applicability of approximate models and to provide a validation tool for approximate scattering theories. A more realistic model, that accounts for hydrodynamic surface interactions, is the non-linear model for surface waves by Creamer et ali [1989]. Rino et ali [ 1991] were the first to use the Creamer model to simulate the Doppler spectra from dynamically evolving surface realizations

  2. Polar sea ice observations by means of microwave radiometry

    NASA Technical Reports Server (NTRS)

    Gloersen, P.; Chang, T. C.; Wilheit, T. T.; Campbell, W. J.

    1973-01-01

    Principles pertinent to the utilization of 1.55 cm wavelength radiation emanating from the surface of the earth for studying the changing characteristics of polar sea ice are briefly reviewed. Recent data obtained at that wavelength with an imaging radiometer on-board the Nimbus 5 satellite are used to illustrate how the seasonal changes in extent of sea ice in both polar regions may be monitored free of atmospheric interference. Within a season, changes in the compactness of the sea ice are also observed from the satellite. Some substantial areas of the Arctic sea ice canopy identified as first-year ice in the past winter were observed not to melt this summer, a graphic illustration of the eventual formation of multiyear ice in the Arctic. Finally, the microwave emissivity of some of the multiyear ice areas near the North Pole was found to increase significantly in the summer, probably due to liquid water content in the firm layer.

  3. Microwave maps of the polar ice of the earth

    NASA Technical Reports Server (NTRS)

    Gloersen, P.; Wilheit, T. T.; Chang, T. C.; Nordberg, W.; Campbell, W. J.

    1974-01-01

    Synoptic views of the entire polar regions of earth have been obtained free of the usual persistent cloud cover using a scanning microwave radiometer operating at a wavelength of 1.55 cm on board the Nimbus-5 satellite. Three different views at each pole are presented utilizing data obtained at approximately one-month intervals from December 1972 to February 1973. Large discrepancies exist between the long-term ice cover depicted in various atlases and the actual extent of the canopies. The distribution of multiyear ice in the north polar region is markedly different from that predicted by existing ice dynamics models. Irregularities in the edge of the Antarctic sea ice pack occur that have neither been observed previously nor anticipated. The brightness temperatures of the Greenland and Antarctic glaciers show interesting contours probably related to the ice and snow morphologic structure.

  4. 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

  5. Passive measurement and interpretation of polarized microwave brightness temperatures

    NASA Technical Reports Server (NTRS)

    Gasiewski, A. J.; Kunkee, D. B.; Piepmeier, J. R.

    1995-01-01

    The goal of this project is to develop satellite-based observational techniques for measuring both oceanic and atmospheric variables using passive polarimetric radiometry. Polarimetric radiometry offers a potential alternative to radar scatterometry in observing global ocean surface wind direction from satellites. Polarimetric radiometry might also provide a means of detecting cell-top ice in convective storms by virtue of the polarizing properties of oriented ice particles, and thus facilitate estimation of the phase of the storm. The project focuses on the development of polarimetric microwave radiometers using digital cross-correlators for obtaining precise measurements of all four Stokes' parameters. As part of the project a unique four-band polarimetric imaging radiometer, the Polar Scanning Radiometer (PSR), is being designed for use on the NASA DC-8 aircraft. In addition to providing an aircraft-based demonstration of digital correlation technology the PSR will significantly enhance the microwave imaging capability of the existing suite of DC-8 instruments. During the first grant year excellent progress has been made in the following areas: (1) demonstrating digital correlation radiometry, (2) fabricating aircraft-qualified correlators for use in the PSR, and (3) modeling observed SSM/I brightness signatures of ocean wind direction.

  6. Microwave Kinetic Inductance Detector with Selective Polarization Coupling

    NASA Technical Reports Server (NTRS)

    Wollack, Edward; U-yen, Kongpop; Stevenson, Thomas; Brown, Ari; Moseley, Samuel; Hsieh, Wen-Ting

    2013-01-01

    A conventional low-noise detector requires a technique to both absorb incident power and convert it to an electrical signal at cryogenic temperatures. This innovation combines low-noise detector and readout functionality into one device while maintaining high absorption, controlled polarization sensitivity, and broadband detection capability. The resulting far-infrared detectors can be read out with a simple approach, which is compact and minimizes thermal loading. The proposed microwave kinetic inductance detector (MKID) consists of three basic elements. The first is the absorptive section in which the incident power is coupled to a superconducting resonator at far-infrared frequency above its superconducting critical frequency (where superconductor becomes normal conductor). This absorber's shape effectively absorbs signals in the desired polarization state and is resonant at the radio frequency (RF) used for readout of the device. Control over the metal film used in the absorber allows realization of structures with either a 50% broadband or 100% resonance absorptance over a 30% fractional bandwidth. The second element is a microwave resonator - which is realized from the thin metal films used to make the absorber as transmission lines - whose resonance frequency changes due to a variation in its kinetic inductance. The resonator's kinetic inductance is a function of the power absorbed by the device. A low-loss dielectric (mono-crystalline silicon) is used in a parallel-plate transmission line structure to realize the desired superconducting resonators. There is negligible coupling among the adjacent elements used to define the polarization sensitivity of each detector. The final component of the device is a microwave transmission line, which is coupled to the resonator, and allows detection of changes in resonance frequency for each detector in the focal plane array. The spiral shape of the detector's absorber allows incident power with two polarizations to

  7. A novel microwave cancellation circuit for measuring nonlinear dielectric changes of polar solution under microwave fields

    NASA Astrophysics Data System (ADS)

    Sun, Hao-Ran; Huang, Ka-Ma

    2015-12-01

    In this paper, an experimental set-up based on a novel microstrip cancellation circuit is presented for investigating the effects of external microwave fields on the dielectric properties of polar solution. The circuit consists of a 3 dB Wilkinson power combiner, a conventional 20 dB backward coupler, and a specially designed 20 dB single-sectioned forward coupler. Besides, in order to realize a uniform electric field in the tested solution, a nicked microstrip ring is designed in the circuit. An improvement of measurement sensitivity in the proposed circuit was obtained when compared to the conventional transmission lines method. We exploit interference cancellation processes to suppress the probing signal at the output port under the principle that two identical amplitude signals with 180° phase difference will completely cancel each other. The measurements are carried out at the frequency of 2.45 GHz, and the temperature effects caused by microwave heating are excluded by the flowing fluid. Experimental results show that the dielectric properties of DMSO-methanol/ethanol mixtures change at the electric field intensity of 105 V m  -  1 and present a distinctly nonlinear dielectric change with the electric fields. The study of the microwave-material interaction has expanded our insights into the high-power microwave’s industry application.

  8. SELF-CALIBRATION OF COSMIC MICROWAVE BACKGROUND POLARIZATION EXPERIMENTS

    SciTech Connect

    Keating, Brian G.; Yadav, Amit P. S.; Shimon, Meir

    2013-01-10

    Precision measurements of the polarization of the cosmic microwave background (CMB) radiation, especially experiments seeking to detect the odd-parity 'B-modes', have far-reaching implications for cosmology. To detect the B-modes generated during inflation, the flux response and polarization angle of these experiments must be calibrated to exquisite precision. While suitable flux calibration sources abound, polarization angle calibrators are deficient in many respects. Man-made polarized sources are often not located in the antenna's far-field, have spectral properties that are radically different from the CMB's, are cumbersome to implement, and may be inherently unstable over the (long) duration these searches require to detect the faint signature of the inflationary epoch. Astrophysical sources suffer from time, frequency, and spatial variability, are not visible from all CMB observatories, and none are understood with sufficient accuracy to calibrate future CMB polarimeters seeking to probe inflationary energy scales of 10{sup 15} GeV. Both man-made and astrophysical sources require dedicated observations which detract from the amount of integration time usable for detection of the inflationary B-modes. CMB TB and EB modes, expected to identically vanish in the standard cosmological model, can be used to calibrate CMB polarimeters. By enforcing the observed EB and TB power spectra to be consistent with zero, CMB polarimeters can be calibrated to levels not possible with man-made or astrophysical sources. All of this can be accomplished for any polarimeter without any loss of observing time using a calibration source which is spectrally identical to the CMB B-modes.

  9. Sea Surface Height 1993 - 2011

    NASA Video Gallery

    This animation depicts year-to-year variability in sea surface height, and chronicles two decades of El Niño and La Niña events. It was created using NASA ocean altimetry data from 1993 to 2011, ...

  10. The Evolution of Spaceborne Microwave Sounders for the U.S. Polar-Orbiting Weather Satellites

    NASA Technical Reports Server (NTRS)

    Shiue, James C.; Krimschansky, Sergey; Patel, Probodh; Hildebrand, Peter (Technical Monitor)

    2002-01-01

    The Advanced Technology Microwave Sounder (ATMS) is the next generation space-borne microwave sounder. It is the latest and most advanced version of a series of satellite-based microwave sounders, currently under development by NASA for the future U.S. operational polar-orbiting weather satellite system, called the NPOESS (National Polar-orbiting Operational Environment Satellite System), slated to begin orbiting around the end of this decade. This paper will present a brief history of the evolution of the space-borne microwave sounders, from its early-day scientific experiments, through the operational sounder aboard today's polar orbiting weather satellites, and ending in the ATMS development. It will also describe the evolution of microwave radiometer technology that enabled the space-borne microwave radiometry, from its early versions with simple, nadir-viewing, fixed-horn antennas to the present-day scanning reflector antennas with broad-band MMIC Low Noise Amplifiers, plus on-board calibrations.

  11. Spectral distortions in the cosmic microwave background polarization

    SciTech Connect

    Renaux-Petel, Sébastien; Fidler, Christian; Pitrou, Cyril; Pettinari, Guido W. E-mail: christian.fidler@port.ac.uk E-mail: g.pettinari@sussex.ac.uk

    2014-03-01

    We compute the spectral distortions of the Cosmic Microwave Background (CMB) polarization induced by non-linear effects in the Compton interactions between CMB photons and the flow of intergalactic electrons. This signal is of the y-type and is dominated by contributions arising from the reionized era. We stress that it is not shadowed by the thermal SZ effect which has no equivalent for polarization. We decompose its angular dependence into E- and B-modes, and we calculate the corresponding power spectra, both exactly and using a suitable Limber approximation that allows a simpler numerical evaluation. We find that B-modes are of the same order of magnitude as E-modes. Both spectra are relatively flat, peaking around ℓ = 280, and their overall amplitude is directly related to the optical depth to reionization. Moreover, we find this effect to be one order of magnitude larger than the non-linear kinetic Sunyaev-Zel'dovich effect in galaxy clusters. Finally, we discuss how to improve the detectability of our signal by cross-correlating it with other quantities sourced by the flow of intergalactic electrons.

  12. Microwave remote sensing and radar polarization signatures of natural fields

    NASA Technical Reports Server (NTRS)

    Mo, Tsan

    1989-01-01

    Theoretical models developed for simulation of microwave remote sensing of the Earth surface from airborne/spaceborne sensors are described. Theoretical model calculations were performed and the results were compared with data of field measurements. Data studied included polarimetric images at the frequencies of P band, L band, and C band, acquired with airborne polarimeters over a agricultural field test site. Radar polarization signatures from bare soil surfaces and from tree covered fields were obtained from the data. The models developed in this report include: (1) Small perturbation model of wave scatterings from randomly rough surfaces, (2) Physical optics model, (3) Geometrical optics model, and (4) Electromagnetic wave scattering from dielectric cylinders of finite lengths, which replace the trees and branches in the modeling of tree covered field. Additionally, a three-layer emissivity model for passive sensing of a vegetation covered soil surface is also developed. The effects of surface roughness, soil moisture contents, and tree parameters on the polarization signatures were investigated.

  13. A wideband photonic microwave phase shifter using polarization-dependent intensity modulation

    NASA Astrophysics Data System (ADS)

    Wang, Weiyu; Sun, Wenhui; Wang, Wenting; Tong, Youwan; Zheng, Jianyu; Yuan, Haiqing; Wang, Xin; Bai, Jinhua; Yu, Lijuan; Liu, Jianguo; Zhu, Ninghua

    2015-12-01

    We present a tunable and wideband microwave photonic phase shifter based on polarization-dependence of the LiNbO3 Mach-Zehender modulator (MZM). In the proposed device, an orthogonal single sideband modulation is implemented by using a MZM and an optical band-pass filter. With the polarizer to synthesize the polarization orthogonal optical carrier and sideband, the phase of the optical microwave signal output from the polarizer can be tuned from 0 to 360° by simply adjusting the polarization direction of the lights whereas the amplitude keeps constant. A full range tunable phase shifting in the frequency range of 10-35 GHz is achieved.

  14. Cosmic Microwave Background B-Mode Polarization Experiment POLARBEAR-2

    NASA Astrophysics Data System (ADS)

    Matsumura, Tomotake; Ade, Peter; Akiba, Yoshiki; Aleman, Christopher; Arnold, Kam; Atlas, Matt; Barron, Darcy; Borrill, Julian; Chapman, Scott; Chinone, Yuji; Cukierman, Ari; Dobbs, Matt; Elleflot, Tucker; Errard, Josquin; Fabbian, Giulio; Feng, Guangyuan; Gilbert, Adam; Grainger, William; Halverson, Nils; Hasegawa, Masaya; Hattori, Kaori; Hazumi, Masashi; Holzapfel, William; Hori, Yasuto; Inoue, Yuki; Jaehnig, Greg; Katayama, Nobuhiko; Keating, Brian; Kermish, Zigmund; Keskitalo, Reijo; Kisner, Ted; Lee, Adrian; Matsuda, Frederick; Morii, Hideki; Moyerman, Stephanie; Myers, Michael; Navaroli, Marty; Nishino, Haruki; Okamura, Takahiro; Reichart, Christian; Richards, Paul; Ross, Colin; Rotermund, Kaja; Sholl, Michael; Siritanasak, Praween; Smecher, Graeme; Stebor, Nathan; Stompor, Radek; Suzuki, Jun-ichi; Suzuki, Aritoki; Takada, Suguru; Takakura, Satoru; Tomaru, Takayuki; Wilson, Brandon; Yamaguchi, Hiroshi; Zahn, Oliver

    POLARBEAR-2 (PB-2) is a ground-based experiment to measure the polarization of the cosmic microwave background (CMB) located at the Atacama desert (5200 m in altitude) in Chile. The science goals of the POLARBEAR-2 are i) to detect or set an upper limit of the inflationary gravitational wave B-mode with the sensitivity of r = 0.01 with 95% C.L. and ii) to measure the weak gravitational lensing B-mode signal and extract the information, such as the sum of neutrino masses with the limit of 90 meV by PB-2 alone and 65 meV by combining PB-2 and Planck at 68% CL. PB-2 observes at the 95 and 150 GHz bands simultaneously using the dichroic dual-polarization antenna-coupled transition edge sensor bolometers together with SQUIDs and the frequency domain multiplexing readout system. The total number of the detectors with the two bands are 7855 that are 6 times more than that of POLARBEAR-1, and the expected focal plane combined statistical sensitivity is 5.7 µK√s with the beam size of 5.2 and3.5 arcmin for the 95 and 150 GHz bands, respectively. The polarization signal is modulated by the sky rotation and the continuously rotating half-wave plate. PB-2 is scheduled to deploy in 2014. The PB-2 receiver will be mounted on the new telescope, which has the same design as the Huan Tran telescope (HTT). We present the overview of PB-2 and discuss the project status.

  15. Microwave Manipulation of Electrically Injected Spin-Polarized Electrons in Silicon

    NASA Astrophysics Data System (ADS)

    Lo, C. C.; Li, J.; Appelbaum, I.; Morton, J. J. L.

    2014-02-01

    We demonstrate microwave manipulation of the spin states of electrically injected spin-polarized electrons in silicon. Although the silicon channel is bounded by ferromagnetic metal films, we show that moderate microwave power can be applied to the devices without altering the device operation significantly. Resonant microwave irradiation is used to induce spin rotation of spin-polarized electrons as they travel across a silicon channel, and the resultant spin polarization is subsequently detected by a ferromagnetic Schottky barrier spin detector. These results demonstrate the potential for combining advanced electron spin resonance techniques to complement the study of semiconductor spintronic devices beyond standard magnetotransport measurements.

  16. New Constraints on Cosmic Polarization Rotation from B-Mode Polarization in the Cosmic Microwave Background

    NASA Astrophysics Data System (ADS)

    di Serego Alighieri, Sperello; Ni, Wei-Tou; Pan, Wei-Ping

    2014-09-01

    SPTpol, POLARBEAR, and BICEP2 have recently measured the cosmic microwave background (CMB) B-mode polarization in various sky regions of several tens of square degrees and obtained BB power spectra in the multipole range 20-3000, detecting the components due to gravitational lensing and to inflationary gravitational waves. We analyze jointly the results of these three experiments and propose modifications to their analyses of the spectra to include in the model, in addition to the gravitational lensing and the inflationary gravitational wave components, and also the effects induced by the cosmic polarization rotation (CPR), if it exists within current upper limits. Although in principle our analysis would also lead to new constraints on CPR, in practice these can only be given on its fluctuations langδα2rang, since constraints on its mean angle are inhibited by the derotation which is applied by current CMB polarization experiments, in order to cope with the insufficient calibration of the polarization angle. The combined data fits from all three experiments (with 29% CPR-SPTpol correlation, depending on the theoretical model) gives the constraint langδα2rang1/2 < 27.3 mrad (1.°56), with r = 0.194 ± 0.033. These results show that the present data are consistent with no CPR detection and the constraint on CPR fluctuation is about 1.°5. This method of constraining the CPR is new, is complementary to previous tests, which use the radio and optical/UV polarization of radio galaxies and the CMB E-mode polarization, and adds a new constraint for the sky areas observed by SPTpol, POLARBEAR, and BICEP2.

  17. Circularly Polarized Microwave Antenna Element with Very Low Off-Axis Cross-Polarization

    NASA Technical Reports Server (NTRS)

    Greem. David; DuToit, Cornelis

    2013-01-01

    The goal of this work was to improve off-axis cross-polarization performance and ease of assembly of a circularly polarized microwave antenna element. To ease assembly, the initial design requirement of Hexweb support for the internal circuit part, as well as the radiating disks, was eliminated. There is a need for different plating techniques to improve soldering. It was also desirable to change the design to eliminate soldering as well as the need to use the Hexweb support. Thus, a technique was developed to build the feed without using solder, solving the lathing and soldering issue. Internal parts were strengthened by adding curvature to eliminate Hexweb support, and in the process, the new geometries of the internal parts opened the way for improving the off-axis cross-polarization performance as well. The radiating disks curvatures were increased for increased strength, but it was found that this also improved crosspolarization. Optimization of the curvatures leads to very low off-axis cross-polarization. The feed circuit was curved into a cylinder for improved strength, eliminating Hexweb support. An aperture coupling feed mechanism eliminated the need for feed pins to the disks, which would have required soldering. The aperture coupling technique also improves cross-polarization performance by effectively exciting the radiating disks very close to the antenna s central axis of symmetry. Because of the shape of the parts, it allowed for an all-aluminum design bolted together and assembled with no solder needed. The advantage of a solderless design is that the reliability is higher, with no single-point failure (solder), and no need for special plating techniques in order to solder the unit together. The shapes (curved or round) make for a more robust build without extra support materials, as well as improved offaxis cross-polarization.

  18. New constraints on cosmic polarization rotation from B-mode polarization in the cosmic microwave background

    SciTech Connect

    Alighieri, Sperello di Serego; Ni, Wei-Tou; Pan, Wei-Ping E-mail: weitou@gmail.com

    2014-09-01

    SPTpol, POLARBEAR, and BICEP2 have recently measured the cosmic microwave background (CMB) B-mode polarization in various sky regions of several tens of square degrees and obtained BB power spectra in the multipole range 20-3000, detecting the components due to gravitational lensing and to inflationary gravitational waves. We analyze jointly the results of these three experiments and propose modifications to their analyses of the spectra to include in the model, in addition to the gravitational lensing and the inflationary gravitational wave components, and also the effects induced by the cosmic polarization rotation (CPR), if it exists within current upper limits. Although in principle our analysis would also lead to new constraints on CPR, in practice these can only be given on its fluctuations (δα{sup 2}), since constraints on its mean angle are inhibited by the derotation which is applied by current CMB polarization experiments, in order to cope with the insufficient calibration of the polarization angle. The combined data fits from all three experiments (with 29% CPR-SPTpol correlation, depending on the theoretical model) gives the constraint (δα{sup 2}){sup 1/2} < 27.3 mrad (1.°56), with r = 0.194 ± 0.033. These results show that the present data are consistent with no CPR detection and the constraint on CPR fluctuation is about 1.°5. This method of constraining the CPR is new, is complementary to previous tests, which use the radio and optical/UV polarization of radio galaxies and the CMB E-mode polarization, and adds a new constraint for the sky areas observed by SPTpol, POLARBEAR, and BICEP2.

  19. Wilkinson Microwave Anisotropy Probe (WMAP) First Year Observations: TE Polarization

    NASA Technical Reports Server (NTRS)

    Kogut, A.; Spergel, D. N.; Barnes, C.; Bennett, C. L.; Halpern, M.; Hinshaw, G.; Jarosik, N.; Limon, M.; Meyer, S. S.; Page, L.; Oegerle, William (Technical Monitor)

    2001-01-01

    The Wilkinson Microwave Anisotropy Probe (WMAP) has mapped the full sky in Stokes I, Q, and U parameters at frequencies 23, 33, 41, 61, and 94 GHz. We detect correlations between the temperature and polarization maps significant at more than 10 standard deviations. The correlations are inconsistent with instrument noise and are significantly larger than the upper limits established for potential systematic errors. The correlations are present in all WAMP frequency bands with similar amplitude from 23 to 94 GHz, and are consistent with a superposition of a CMB signal with a weak foreground. The fitted CMB component is robust against different data combinations and fitting techniques. On small angular scales (theta less than 5 deg), the WMAP data show the temperature-polarization correlation expected from adiabatic perturbations in the temperature power spectrum. The data for l greater than 20 agree well with the signal predicted solely from the temperature power spectra, with no additional free parameters. We detect excess power on large angular scales (theta greater than 10 deg) compared to predictions based on the temperature power spectra alone. The excess power is well described by reionization at redshift 11 is less than z(sub r) is less than 30 at 95% confidence, depending on the ionization history. A model-independent fit to reionization optical depth yields results consistent with the best-fit ACDM model, with best fit value t = 0.17 +/- 0.04 at 68% confidence, including systematic and foreground uncertainties. This value is larger than expected given the detection of a Gunn-Peterson trough in the absorption spectra of distant quasars, and implies that the universe has a complex ionization history: WMAP has detected the signal from an early epoch of reionization.

  20. FETAL AND MATERNAL EFFECTS OF CONTINUAL EXPOSURE OF RATS TO 970-MHZ CIRCULARLY-POLARIZED MICROWAVES

    EPA Science Inventory

    Virtually continual exposure to 970-MHz microwaves in circularly-polarized waveguides was used to elicit fetal responses in Sprague-Dawley rats during gestation. wo hundred fifty rats were exposed to microwave radiation at whole-body averaged specific absorption rates (SAR) of 0....

  1. Sea surface wind measurement over offshore wind farm using TerraSAR-X data

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Ming; Lehner, Susanne; Brusch, Stephan; Ren, Yong-Zheng

    2011-11-01

    A TerraSAR-X Stripmap image over the North Sea shows significant spatial variations of sea surface wind field over the offshore wind farm Alpha Ventus. In the present study, we demonstrate the tempting potential of using high resolution SAR to investigate spatial variations of sea surface wind field over the offshore wind farms. A newly developed X-band Geophysical Model Function (GMF) XMOD2 is applied on the TS-X data to retrieve sea surface wind speed. By comparing the TS-X retrieved sea surface wind field to results of the DWD wind field, in situ observations on the FiNO platform, as well as the satellite measurement derived from the polarimetric microwave radiometer WindSat, it is found that the SAR estimated wind field not only agrees well with other measurements, but also presents the fine-scale features of sea surface wind field over the offshore wind farm.

  2. MODIS Global Sea Surface Temperature

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Every day the Moderate-resolution Imaging Spectroradiometer (MODIS) measures sea surface temperature over the entire globe with high accuracy. This false-color image shows a one-month composite for May 2001. Red and yellow indicates warmer temperatures, green is an intermediate value, while blues and then purples are progressively colder values. The new MODIS sea surface temperature product will be particularly useful in studies of temperature anomalies, such as El Nino, as well as research into how air-sea interactions drive changes in weather and climate patterns. In the high resolution image, notice the amazing detail in some of the regional current patterns. For instance, notice the cold water currents that move from Antarctica northward along South America's west coast. These cold, deep waters upwell along an equatorial swath around and to the west of the Galapagos Islands. Note the warm, wide currents of the Gulf Stream moving up the United States' east coast, carrying Caribbean warmth toward Newfoundland and across the Atlantic toward Western Europe. Note the warm tongue of water extending from Africa's east coast to well south of the Cape of Good Hope. MODIS was launched in December 1999 aboard NASA's Terra satellite. For more details on this and other MODIS data products, please see NASA Unveils Spectacular Suite of New Global Data Products from MODIS. Image courtesy MODIS Ocean Group, NASA GSFC, and the University of Miami

  3. Observation of linear-polarization-sensitivity in the microwave-radiation-induced magnetoresistance oscillations

    SciTech Connect

    Mani, R. G.; Ramanayaka, A. N.; Wegscheider, W.

    2013-12-04

    We examine the linear polarization sensitivity of the radiation- induced magneto-resistance oscillations by investigating the effect of rotating in-situ the electric field of linearly polarized microwaves relative to the current, in the GaAs/AlGaAs system. We find that the frequency and the phase of the photo-excited magneto-resistance oscillations are insensitive to the polarization. On the other hand, the amplitude of the resistance oscillations are strongly sensitive to the relative orientation between the microwave antenna and the current-axis in the specimen.

  4. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    PubMed Central

    Ye, Tianyu; Liu, Han-Chun; Wang, Zhuo; Wegscheider, W.; Mani, Ramesh G.

    2015-01-01

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. For circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ. PMID:26450679

  5. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation.

    PubMed

    Ye, Tianyu; Liu, Han-Chun; Wang, Zhuo; Wegscheider, W; Mani, Ramesh G

    2015-01-01

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. For circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ. PMID:26450679

  6. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    SciTech Connect

    Ye, Tianyu; Liu, Han -Chun; Wang, Zhuo; Wegscheider, W.; Mani, Ramesh G.

    2015-10-09

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. As a result, for circularly polarized radiation, the oscillatory magnetoresistive response is hardly sensitive to θ.

  7. Satellite-Derived Sea Surface Temperature: Workshop-2

    NASA Technical Reports Server (NTRS)

    Njoku, E. G.

    1984-01-01

    Global accuracies and error characteristics of presently orbiting satellite sensors are examined. The workshops are intended to lead to a better understanding of present capabilities for sea surface temperature measurement and to improve measurement concepts for the future. Data from the Advanced Very High Resolution Radiometer AVHRR and Scanning Multichannel Microwave Radiometer is emphasized. Some data from the High Resolution Infrared Sounder HIRS and AVHRR are also examined. Comparisons of satellite data with ship and eXpendable BathyThermograph XBT measurement show standard deviations in the range 0.5 to 1.3 C with biases of less than 0.4 C, depending on the sensor, ocean region, and spatial/temporal averaging. The Sea Surface Temperature SST anomaly maps show good agreement in some cases, but a number of sensor related problems are identified.

  8. Satellite-Derived Sea Surface Temperature: Workshop 1

    NASA Technical Reports Server (NTRS)

    Njoku, E. G.

    1983-01-01

    Satellite measurements of sea surface temperature are now possible using a variety of sensors. The present accuracies of these methods are in the range of 0.5 to 2.0 C. This makes them potentially useful for synoptic studies of ocean currents and for global monitoring of climatological anomalies. To improve confidence in the satellite data, objective evaluations of sensor accuracies are necessary, and the conditions under which these accuracies degrade need to be understood. The Scanning Multichannel Microwave Radiometer (SMMR) on the Nimbus-7 satellite was studied. Sea surface temperatures, derived from November 1979 SMMR data, were compared globally against ship measurements and climatology, using facilities of the JPL Pilot Ocean Data System. Methods for improved data analysis and plans for additional workshops to incorporate data from other sensors were discussed.

  9. Generation of phase-coded microwave signals using a polarization-modulator-based photonic microwave phase shifter.

    PubMed

    Zhang, Yamei; Pan, Shilong

    2013-03-01

    A scheme for the generation of phase-coded microwave signals using an electrically tunable photonic microwave phase shifter is proposed and demonstrated. The photonic phase shifter is based on a single-sideband polarization modulator (PolM), and the tuning of the phase shifter is implemented by a second PolM. By introducing an RF signal to the first PolM and an electrical coding signal to the second PolM, a phase-coded microwave signal with binary phase codes or polyphase codes is achieved. An experiment is performed. The simple and flexible operation, high coding rate, large frequency range, excellent transmission performance, and high stability of the system is confirmed. PMID:23455292

  10. Bistatic electromagnetic scattering and detection of pollutant on a sea surface

    NASA Astrophysics Data System (ADS)

    Ghanmi, Helmi; Khenchaf, Ali; Comblet, Fabrice

    2015-01-01

    We present the study and analysis of the variations of the bistatic electromagnetic (EM) signature of the sea surface contaminated by pollutants. Therefore, we start with the numerical analyses of the pollutant effect on the geometrical and physical characteristics of sea surface. Then, we evaluate the EM scattering coefficients of the clean and polluted sea surfaces observed in bistatic configuration by using the numerical forward-backward method. The obtained numerical results of the EM scattering coefficients are studied and given as a function of various parameters: sea state, wind velocity, type of pollutant (sea surface polluted by oil emulsion and sea surface covered by oil layer), incidence and scattering angles, frequencies bands (C, X, and Ku), and radar polarization.

  11. Bistatic scattering from a contaminated sea surface observed in C, X, and Ku bands

    NASA Astrophysics Data System (ADS)

    Ghanmi, H.; Khenchaf, A.; Comblet, F.

    2014-10-01

    The aim of the work presented in this paper focuses on the study and analysis of variations of the bistatic electromagnetic signature of the sea surface contaminated by pollutants. Therefore, we will start the numerical analyses of the pollutant effect on the geometrical and physical characteristics of sea surface. Then, we will evaluate the electromagnetic (EM) scattering coefficients of the clean and polluted sea surface observed in bistatic configuration by using the numerical Forward-Backward Method (FBM). The obtained numerical results of the electromagnetic scattering coefficients are studied and given as a function of various parameters: sea state, wind velocity, type of pollutant (sea surface polluted by oil emulsion, and sea surface covered by oil layer), incidence and scattering angles, frequencies bands (C, X and Ku) and radar polarization.

  12. Broadband and wide-angle reflective polarization converter based on metasurface at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Zhang, Linbo; Zhou, Peiheng; Chen, Haiyan; Lu, Haipeng; Xie, Jianliang; Deng, Longjiang

    2015-09-01

    We propose to realize a broadband and wide-angle reflective polarization converter in microwave regions. The proposed converter can convert a linearly polarized (LP) wave to its cross-polarized wave at three resonant frequencies. It can also convert the LP wave to a circularly polarized wave at other two resonant frequencies. Furthermore, the proposed converter can achieve broad bandwidth with incident angle up to 45°. The simulated and measured results are in agreement in the entire frequency regions, and the bandwidth of polarization conversion over 75 % can be obtained from 7.6 to 15.5 GHz under normal incidence and from 7.8 to 13.0 GHz under incident angle of 45°. The surface current distributions of the proposed converter are discussed to analyze the physical mechanism. The converter tolerance to wide angle of incidence and the broad bandwidth could be useful in the range of applications in the microwave regions.

  13. Frequency swept microwaves for hyperfine decoupling and time domain dynamic nuclear polarization.

    PubMed

    Hoff, Daniel E M; Albert, Brice J; Saliba, Edward P; Scott, Faith J; Choi, Eric J; Mardini, Michael; Barnes, Alexander B

    2015-11-01

    Hyperfine decoupling and pulsed dynamic nuclear polarization (DNP) are promising techniques to improve high field DNP NMR. We explore experimental and theoretical considerations to implement them with magic angle spinning (MAS). Microwave field simulations using the high frequency structural simulator (HFSS) software suite are performed to characterize the inhomogeneous phase independent microwave field throughout a 198GHz MAS DNP probe. Our calculations show that a microwave power input of 17W is required to generate an average EPR nutation frequency of 0.84MHz. We also present a detailed calculation of microwave heating from the HFSS parameters and find that 7.1% of the incident microwave power contributes to dielectric sample heating. Voltage tunable gyrotron oscillators are proposed as a class of frequency agile microwave sources to generate microwave frequency sweeps required for the frequency modulated cross effect, electron spin inversions, and hyperfine decoupling. Electron spin inversions of stable organic radicals are simulated with SPINEVOLUTION using the inhomogeneous microwave fields calculated by HFSS. We calculate an electron spin inversion efficiency of 56% at a spinning frequency of 5kHz. Finally, we demonstrate gyrotron acceleration potentials required to generate swept microwave frequency profiles for the frequency modulated cross effect and electron spin inversions. PMID:26482131

  14. Multi-frequency phase-coded microwave signal generation based on polarization modulation and balanced detection.

    PubMed

    Zhu, Dan; Xu, Weiyuan; Wei, Zhengwu; Pan, Shilong

    2016-01-01

    Photonic multi-frequency phase-coded microwave signal generation is proposed and demonstrated based on polarization modulation and balanced detection. Consisting of only a polarization modulator (PolM) driven by an electrical coding data, a polarization beam splitter (PBS) and a balanced photodetector (BPD), the proposed microwave phase coder has no requirement on the wavelength, intensity modulation format, or modulation index of the input optical microwave signal, and allows phase coding of arbitrary-format RF signals, which enables multi-frequency phase coding with compact structure, simple operation, and high flexibility. A proof-of-concept experiment is performed, achieving simultaneous phase coding of 15 and 30 GHz, or 10 and 20 GHz RF signals with a coding rate of 5  Gb/s. PMID:26696170

  15. Resonance overlap criterion for H atom ionization by circularly polarized microwave fields

    SciTech Connect

    Sacha, K.; Zakrzewski, J.

    1997-01-01

    The threshold for H atom ionization by circularly polarized microwave fields is discussed within the classical mechanics framework for high microwave frequencies. The Chirikov resonance overlap criterion predictions are compared with estimates obtained adopting the renormalization method. It is shown that the ionization threshold is highly sensitive to the helicity of microwaves. Among all possible initial electronic orbits, those of medium eccentricity are the first to ionize. The results obtained indicate that collisions with the nucleus play a negligible role for the onset of ionization. {copyright} {ital 1997} {ital The American Physical Society}

  16. A microwave trap for sympathetic cooling of polar molecules

    NASA Astrophysics Data System (ADS)

    Dunseith, Devin; Truppe, Stefan; Hendricks, Richard; Sauer, Ben; Hinds, Edward; Tarbutt, Michael

    2015-03-01

    We have been developing techniques to cool molecules into the microkelvin regime. One method is to use sympathetic cooling, using ultracold atoms as a refrigerant to cool molecules. Previous work has suggested that atoms and molecules can be trapped in the antinode of a Fabry­-Pérot microwave cavity. We couple microwave power into this cavity from a rectangular waveguide via a small hole in one mirror. We have developed an analytical model that helps us understand this coupling, and gives us an idea of how the size of the hole affects the cavity's coupling and finesse. We carried out finite-­difference time­-domain simulations and performed experiments on a prototype cavity to verify this model. We have now designed and built this trap for operation under ultra­high vacuum, with the ability to cool the mirrors to 77 K and couple in up to 2 kW of microwave power. This will allow us to trap molecules with a moderate dipole moment at temperatures of hundreds of millikelvin, as well as atoms at a few millikelvin. We will present our work in creating and understanding the microwave trap, as well as our first results demonstrating trapping of lithium atoms in the microwave trap. The authors would like to thank EPSRC for supporting this work.

  17. New satellite record of sea surface temperature

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2013-02-01

    Sea surface temperature is one of the key variables scientists track in studying climate changes; it is also important to meteorology and oceanography. Merchant et al. describe a new 20-year record of sea surface temperature. The record was created using infrared imagery from the Along-Track Scanning Radiometers (ATSR) as part of the ATSR Reprocessing for Climate (ARC) project.

  18. Propagation of Polarized Cosmic Microwave Background Radiation in an Anisotropic Magnetized Plasma

    SciTech Connect

    Moskaliuk, S. S.

    2010-01-01

    The polarization plane of the cosmic microwave background radiation (CMBR) can be rotated either in a space-time with metric of anisotropic type and in a magnetized plasma or in the presence of a quintessential background with pseudoscalar coupling to electromagnetism. A unified treatment of these three phenomena is presented for cold anisotropic plasma at the pre-recombination epoch. It is argued that the generalized expressions derived in the present study may be relevant for direct searches of a possible rotation of the cosmic microwave background polarization.

  19. H-atom ionization by elliptically polarized microwave fields: The overlap criterion

    SciTech Connect

    Sacha, K.; Zakrzewski, J.

    1997-07-01

    The threshold for H-atom ionization by elliptically polarized microwave fields is discussed within the classical-mechanics framework using the Chirikov overlap criterion. It is shown that the trends observed in the recent experiment [M. R. W. Bellermann {ital et al.} Phys. Rev. Lett. {bold 76}, 892 (1996)] are qualitatively reproduced by the theory; the origin of the remaining discrepancy is discussed. Increased stability of some orbits with respect to the perturbation due to the elliptically polarized microwaves has been related to vanishing widths of the corresponding resonance islands. Analytic Chirikov overlap prediction is compared with results of numerical simulations. {copyright} {ital 1997} {ital The American Physical Society}

  20. Boltzmann hierarchy for the cosmic microwave background at second order including photon polarization

    SciTech Connect

    Beneke, M.; Fidler, C.

    2010-09-15

    Non-Gaussianity and B-mode polarization are particularly interesting features of the cosmic microwave background, as--at least in the standard model of cosmology--their only sources to first order in cosmological perturbation theory are primordial, possibly generated during inflation. If the primordial sources are small, the question arises how large is the non-Gaussianity and B-mode background induced in second order from the initially Gaussian and scalar perturbations. In this paper we derive the Boltzmann hierarchy for the microwave background photon phase-space distributions at second order in cosmological perturbation theory including the complete polarization information, providing the basis for further numerical studies. As an aside we note that the second-order collision term contains new sources of B-mode polarization and that no polarization persists in the tight-coupling limit.

  1. Stratospheric Impact of Varying Sea Surface Temperatures

    NASA Technical Reports Server (NTRS)

    Newman, Paul A.; Nash, Eric R.; Nielsen, Jon E.; Waugh, Darryn; Pawson, Steven

    2004-01-01

    The Finite-Volume General Circulation Model (FVGCM) has been run in 50 year simulations with the: 1) 1949-1999 Hadley Centre sea surface temperatures (SST), and 2) a fixed annual cycle of SSTs. In this presentation we first show that the 1949-1999 FVGCM simulation produces a very credible stratosphere in comparison to an NCEP/NCAR reanalysis climatology. In particular, the northern hemisphere has numerous major and minor stratospheric warming, while the southern hemisphere has only a few over the 50-year simulation. During the northern hemisphere winter, temperatures are both warmer in the lower stratosphere and the polar vortex is weaker than is found in the mid-winter southern hemisphere. Mean temperature differences in the lower stratosphere are shown to be small (less than 2 K), and planetary wave forcing is found to be very consistent with the climatology. We then will show the differences between our varying SST simulation and the fixed SST simulation in both the dynamics and in two parameterized trace gases (ozone and methane). In general, differences are found to be small, with subtle changes in planetary wave forcing that lead to reduced temperatures in the SH and increased temperatures in the NH.

  2. Fast polarization changes in mm microwave emission of weak multistructured solar bursts

    NASA Technical Reports Server (NTRS)

    Kaufmann, P.; Strauss, F. M.; Costa, J. E. R.; Dennis, B. R.

    1982-01-01

    Circular polarization of weak multistructured solar bursts was measured at mm microwaves with unprecedented sensitivity (0.03 sfu rms) and high time resolution (1ms). It was shown that sudden changes occur in the degree of polarization with time scales of 0.04 to 0.3 s. In most cases the degree of polarization attained maximum values before the maximum flux in both mm microwaves and hard X-rays with time scales of 0.04 to 1.0 s. The timing accuracy in determining the degree of polarization was 40 ms. Physical phenomena are discussed invoking one or a combination of various possible causes for the observed effects. The bursts at mm microwaves were weak compared to the contribution of the preexisting active regions, and therefore the changes in magnetoionic propagation conditions for emerging radiation plays an important role in the observed effects. Composite effects due to more than one polarizing mechanism or more than one polarized spots within the antenna beam are discussed.

  3. 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.

  4. Constraints on CPT violation from Wilkinson Microwave Anisotropy Probe three year polarization data: A wavelet analysis

    SciTech Connect

    Cabella, Paolo; Silk, Joseph; Natoli, Paolo

    2007-12-15

    We perform a wavelet analysis of the temperature and polarization maps of the cosmic microwave background (CMB) delivered by the Wilkinson Microwave Anisotropy Probe experiment in search for a parity-violating signal. Such a signal could be seeded by new physics beyond the standard model, for which the Lorentz and CPT symmetries may not hold. Under these circumstances, the linear polarization direction of a CMB photon may get rotated during its cosmological journey, a phenomenon also called cosmological birefringence. Recently, Feng et al. have analyzed a subset of the Wilkinson Microwave Anisotropy Probe and BOOMERanG 2003 angular power spectra of the CMB, deriving a constraint that mildly favors a nonzero rotation. By using wavelet transforms we set a tighter limit on the CMB photon rotation angle {delta}{alpha}=-2.5{+-}3.0 ({delta}{alpha}=-2.5{+-}6.0) at the one (two) {sigma} level, consistent with a null detection.

  5. A microwave applicator for uniform irradiation by circularly polarized waves in an anechoic chamber

    NASA Astrophysics Data System (ADS)

    Chiang, W. Y.; Wu, M. H.; Wu, K. L.; Lin, M. H.; Teng, H. H.; Tsai, Y. F.; Ko, C. C.; Yang, E. C.; Jiang, J. A.; Barnett, L. R.; Chu, K. R.

    2014-08-01

    Microwave applicators are widely employed for materials heating in scientific research and industrial applications, such as food processing, wood drying, ceramic sintering, chemical synthesis, waste treatment, and insect control. For the majority of microwave applicators, materials are heated in the standing waves of a resonant cavity, which can be highly efficient in energy consumption, but often lacks the field uniformity and controllability required for a scientific study. Here, we report a microwave applicator for rapid heating of small samples by highly uniform irradiation. It features an anechoic chamber, a 24-GHz microwave source, and a linear-to-circular polarization converter. With a rather low energy efficiency, such an applicator functions mainly as a research tool. This paper discusses the significance of its special features and describes the structure, in situ diagnostic tools, calculated and measured field patterns, and a preliminary heating test of the overall system.

  6. A microwave applicator for uniform irradiation by circularly polarized waves in an anechoic chamber.

    PubMed

    Chiang, W Y; Wu, M H; Wu, K L; Lin, M H; Teng, H H; Tsai, Y F; Ko, C C; Yang, E C; Jiang, J A; Barnett, L R; Chu, K R

    2014-08-01

    Microwave applicators are widely employed for materials heating in scientific research and industrial applications, such as food processing, wood drying, ceramic sintering, chemical synthesis, waste treatment, and insect control. For the majority of microwave applicators, materials are heated in the standing waves of a resonant cavity, which can be highly efficient in energy consumption, but often lacks the field uniformity and controllability required for a scientific study. Here, we report a microwave applicator for rapid heating of small samples by highly uniform irradiation. It features an anechoic chamber, a 24-GHz microwave source, and a linear-to-circular polarization converter. With a rather low energy efficiency, such an applicator functions mainly as a research tool. This paper discusses the significance of its special features and describes the structure, in situ diagnostic tools, calculated and measured field patterns, and a preliminary heating test of the overall system. PMID:25173291

  7. A microwave applicator for uniform irradiation by circularly polarized waves in an anechoic chamber

    SciTech Connect

    Chiang, W. Y.; Wu, M. H.; Wu, K. L.; Lin, M. H.; Teng, H. H.; Barnett, L. R.; Chu, K. R.; Tsai, Y. F.; Ko, C. C.; Yang, E. C.; Jiang, J. A.

    2014-08-15

    Microwave applicators are widely employed for materials heating in scientific research and industrial applications, such as food processing, wood drying, ceramic sintering, chemical synthesis, waste treatment, and insect control. For the majority of microwave applicators, materials are heated in the standing waves of a resonant cavity, which can be highly efficient in energy consumption, but often lacks the field uniformity and controllability required for a scientific study. Here, we report a microwave applicator for rapid heating of small samples by highly uniform irradiation. It features an anechoic chamber, a 24-GHz microwave source, and a linear-to-circular polarization converter. With a rather low energy efficiency, such an applicator functions mainly as a research tool. This paper discusses the significance of its special features and describes the structure, in situ diagnostic tools, calculated and measured field patterns, and a preliminary heating test of the overall system.

  8. Problems in determining sea surface topography

    NASA Technical Reports Server (NTRS)

    Whitehead, J. A., Jr.

    1978-01-01

    Anticipated problems for determining ocean dynamics signals from sea surface topography are discussed. The needs for repeated tracks are listed if oceanic tides or ocean turbulence are to be determined.

  9. Aquarius Observations of Sea Surface Salinity

    NASA Video Gallery

    This visualization shows changes in global sea surface salinity, as measured by NASA’s Aquarius instrument aboard the Aquarius/SAC-D spacecraft, from December 2011 through December 2012. Red repr...

  10. 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.

  11. SMOS Sea Surface Salinity Validation in the South China Sea

    NASA Astrophysics Data System (ADS)

    Ren, Yongzheng; Li, Xiaoming; Dong, Qing

    2013-01-01

    In November 2009, the European Space Agency (ESA) launched the first soil moisture and ocean salinity (SMOS) satellite, which represented the first use of spaceborne remote sensing tools to probe global sea surface salinity (SSS). The SMOS satellite carries a microwave imaging radiometer with aperture synthesis (MIRAS) for detection in the microwave L-band as the only payload. The MIRAS instrument is expected to provide a global SSS distribution with a spatial resolution of approximately 100 km and an accuracy of 0.1-0.2 practical salinity units (psu). The South China Sea is semi-enclosed, and the sea conditions are relatively complex. The suitability of ESA SMOS salinity products for the South China Sea has not been validated. Therefore, using SSS data measured during an expedition in the South China Sea, which was sponsored by China Natural Science Foundation and conducted in the fall of 2011, this paper validated the SSS products released by ESA, which were retrieved using three sea surface roughness models. To analyze the effect of the spatial resolution on the weekly average SMOS SSS distribution, the weekly average salinity data were averaged to reduce the spatial resolution to 0.25 ° x 0.25°. These average data were then compared to the measured data, followed by an analysis of the error variation. In addition, the effects of the orbital track (ascending or descending) on the SSS retrieval were analyzed.

  12. Dual-band and high-efficiency polarization converter based on metasurfaces at microwave frequencies

    NASA Astrophysics Data System (ADS)

    Liu, Yajun; Xia, Song; Shi, Hongyu; Zhang, Anxue; Xu, Zhuo

    2016-06-01

    We present a dual-band and high-efficiency polarization converter in microwave regime. The proposed converter can convert a linearly polarized wave to its cross-polarized wave for two distinct bands: Ku (11.5-20.0 GHz) and Ka (28.8-34.0 GHz). It can also convert the linearly polarized wave to a circularly polarized wave at four other frequencies. The experimental results are in good agreement with simulation results for both frequency bands. The polarization conversion ratio is above 0.94 for the Ku-band and 0.90 for the Ka-band. Furthermore, the converter can achieve dual-band and high-efficiency polarization conversion over angles of incidence up to 45°. The converter is also polarization-selective in that only the x- and y-polarized waves can be converted. The physical mechanism of the dual-band polarization conversion effect is interpreted via decomposed electric field components that couple with different plasmon resonance modes of the structure.

  13. Fast cosmic microwave background power spectrum estimation of temperature and polarization with Gabor transforms

    NASA Astrophysics Data System (ADS)

    Hansen, Frode K.; Górski, Krzysztof M.

    2003-08-01

    We extend the analysis of Gabor transforms on a cosmic microwave background temperature map to polarization. We study the temperature and polarization power spectra on the cut sky, the so-called pseudo-power spectra. The transformation kernels relating the full-sky polarization power spectra and the polarization pseudo-power spectra are found to be similar to the kernel for the temperature power spectrum. This fact is used to construct a fast power spectrum estimation algorithm using the pseudo-power spectrum of temperature and polarization as data vectors in a maximum-likelihood approach. Using the pseudo-power spectra as input to the likelihood analysis solves the problem of having to invert huge matrices, which makes the standard likelihood approach infeasible.

  14. Simulation of Cosmic Microwave Background Polarization Fields for AMiBA Experiment

    NASA Astrophysics Data System (ADS)

    Park, Chan-Gyung; Park, Changbom

    2002-06-01

    We have made a topological study of cosmic microwave background (CMB) polarization maps by simulating the AMiBA experiment results. A ΛCDM CMB sky is adopted to make mock interferometric observations designed for the AMiBA experiment. CMB polarization fields are reconstructed from the AMiBA mock visibility data using the maximum entropy method. We have also considered effects of Galactic foregrounds on the CMB polarization fields. The genus statistic is calculated from the simulated Q and U polarization maps, where Q and U are Stokes parameters. Our study shows that the Galactic foreground emission, even at low Galactic latitude, is expected to have small effects on the CMB polarization field. Increasing survey area and integration time is essential to detect non-Gaussian signals of cosmological origin through genus measurement.

  15. Analytical Derivation of the Vegetation Optical Depth from the Microwave Polarization Difference Index

    NASA Technical Reports Server (NTRS)

    Meesters, Antoon G. C. A.; DeJeu, Richard A. M.; Owe, Manfred

    2006-01-01

    A numerical solution for the canopy optical depth in an existing microwave-based land surface parameter retrieval model is presented. The optical depth is derived from the microwave polarization difference index and the dielectric constant of the soil. The original procedure used an approximation in the form of a logarithmic decay function to define this relationship, and was derived through a series of lengthy polynomials. These polynomials had to be recalculated when the scattering albedo or antenna incidence angle changes. The new procedure is computationally more efficient and accurate.

  16. Enhanced polarization of the cosmic microwave background radiation from thermal gravitational waves.

    PubMed

    Bhattacharya, Kaushik; Mohanty, Subhendra; Nautiyal, Akhilesh

    2006-12-22

    If inflation was preceded by a radiation era, then at the time of inflation there will exist a decoupled thermal distribution of gravitons. Gravitational waves generated during inflation will be amplified by the process of stimulated emission into the existing thermal distribution of gravitons. Consequently, the usual zero temperature scale invariant tensor spectrum is modified by a temperature dependent factor. This thermal correction factor amplifies the B-mode polarization of the cosmic microwave background radiation by an order of magnitude at large angles, which may now be in the range of observability of the Wilkinson Microwave Anisotropy Probe. PMID:17280339

  17. Frequency-dependent polarization-angle-phase-shift in the microwave-induced magnetoresistance oscillations

    SciTech Connect

    Liu, Han-Chun; Ye, Tianyu; Mani, R. G.; Wegscheider, W.

    2015-02-14

    Linear polarization angle, θ, dependent measurements of the microwave radiation-induced oscillatory magnetoresistance, R{sub xx}, in high mobility GaAs/AlGaAs 2D electron devices have shown a θ dependence in the oscillatory amplitude along with magnetic field, frequency, and extrema-dependent phase shifts, θ{sub 0}. Here, we suggest a microwave frequency dependence of θ{sub 0}(f) using an analysis that averages over other smaller contributions, when those contributions are smaller than estimates of the experimental uncertainty.

  18. The Application of Aperture Synthesis to the Remote Sensing of Sea Surface Salinity From Space

    NASA Technical Reports Server (NTRS)

    LeVine, David M.

    1998-01-01

    Sea surface salinity is measured optimally at the long wavelength end of the microwave spectrum in order to maximize radiometric sensitivity to changes in salinity. Long wavelengths (e.g. L-band) mean large antennas in space, and because of the technological challenge associated with putting large scanning antennas in orbit, no system currently exists to measure salinity. Aperture synthesis is an interferometric technique to make deployment of large antenna apertures in space feasible. It uses pairs of small antennas and signal processing to achieve the resolution of a single large aperture. Aperture synthesis has been demonstrated successfully for remote sensing by the aircraft prototype radiometer, ESTAR. ESTAR is an L-band instrument which employs aperture synthesis in the cross track dimension. Recent measurements with ESTAR of the fresh water outflow from the Delaware River are in good agreement (about 1 psu) with shipboard thermosalinograph measurements. Synthetic aperture radiometers are currently being developed for remote sensing from space. HYDROSTAR is an instrument for remote sensing from space based on the design of ESTAR. It employs aperture synthesis in one dimension and is being proposed as a pathfinder instrument to make global maps of soil moisture and sea surface salinity and to demonstrate the feasibility of aperture synthesis for remote sensing from space. Instruments which use remote sensing in two dimensions are currently being developed by the European Space Agency. These instruments include additional channels (frequencies and polarizations) and may be able to achieve radiometric sensitivity and spatial resolution to meet the diverse needs of the coastal zone and open ocean oceanographic communities.

  19. An application of new microwave absorption tube in non-polar solvent microwave-assisted extraction of organophosphorus pesticides from fresh vegetable samples.

    PubMed

    Zhao, Xin; Xu, Xu; Su, Rui; Zhang, Hanqi; Wang, Ziming

    2012-03-16

    A new self-designed microwave absorption tube was used in microwave-assisted extraction of seven organophosphorus pesticides from four kinds of vegetable samples. The non-polar solvent was used as extraction solvent, and a new portable microwave extraction apparatus was used. By sealing graphite powder in glass tube, microwave absorption tube was made and used to heat samples directly. The extracts were directly analyzed by GC-MS without any clean-up process. The effects of some experimental parameters on extraction efficiency were investigated and optimized. 3.0 g of sample, 25 mL of hexane and three microwave absorption tubes were added in the microwave extraction vessel, the extraction was carried out under 425 W irradiation power at 70 °C for 8 min. The recoveries were in the range of 76.5-109.4% and the relative standard deviations were lower than 13.1%. PMID:22321952

  20. Comparative study of microwave radiation-induced magnetoresistive oscillations induced by circularly- and linearly- polarized photo-excitation

    DOE PAGESBeta

    Ye, Tianyu; Liu, Han -Chun; Wang, Zhuo; Wegscheider, W.; Mani, Ramesh G.

    2015-10-09

    A comparative study of the radiation-induced magnetoresistance oscillations in the high mobility GaAs/AlGaAs heterostructure two dimensional electron system (2DES) under linearly- and circularly- polarized microwave excitation indicates a profound difference in the response observed upon rotating the microwave launcher for the two cases, although circularly polarized microwave radiation induced magnetoresistance oscillations observed at low magnetic fields are similar to the oscillations observed with linearly polarized radiation. For the linearly polarized radiation, the magnetoresistive response is a strong sinusoidal function of the launcher rotation (or linear polarization) angle, θ. As a result, for circularly polarized radiation, the oscillatory magnetoresistive response ismore » hardly sensitive to θ.« less

  1. Simultaneous measurements of skin sea surface temperature and sea surface emissivity from a single thermal imagery.

    PubMed

    Yoshimori, Kyu; Tamba, Sumio; Yokoyama, Ryuzo

    2002-08-20

    A novel method, to our knowledge, to measure simultaneously the thermal emissivity and skin temperature of a sea surface has been developed. The proposed method uses an infrared image that includes a sea surface and a reference object located near the surface. By combining this image with sky radiation temperature, we retrieve both skin sea surface temperature and sea surface emissivity from the single infrared image. Because the method requires no knowledge of thermal radiative properties of actual sea surfaces, it can be used even for a contaminated sea surface whose emissivity is hard to determine theoretically, e.g., oil slicks or slicks produced by biological wastes. Experimental results demonstrate that the estimated emissivity agrees with the theoretical prediction and, also, the recovered temperature distribution of skin sea surface has no appreciable high-temperature area that is due to reflection of the reference object. The method allows the acquisition of match-up data of radiometric sea surface temperatures that precisely correspond to the satellite observable data. PMID:12206200

  2. Addressing spin transitions on 209Bi donors in silicon using circularly polarized microwaves

    NASA Astrophysics Data System (ADS)

    Yasukawa, T.; Sigillito, A. J.; Rose, B. C.; Tyryshkin, A. M.; Lyon, S. A.

    2016-03-01

    Over the past decade, donor spin qubits in isotopically enriched 28Si have been intensely studied due to their exceptionally long coherence times. More recently, bismuth donor electron spins have become popular because Bi has a large nuclear spin which gives rise to clock transitions (first-order insensitive to magnetic field noise). At every clock transition there are two nearly degenerate transitions between four distinct states which can be used as a pair of qubits. Here it is experimentally demonstrated that these transitions are excited by microwaves of opposite helicity such that they can be selectively driven by varying microwave polarization. This work uses a combination of a superconducting coplanar waveguide (CPW) microresonator and a dielectric resonator to flexibly generate arbitrary elliptical polarizations while retaining the high sensitivity of the CPW.

  3. Production of global sea surface temperature fields for the Jet Propulsion Laboratory workshop comparisons

    NASA Technical Reports Server (NTRS)

    Hilland, J. E.; Njoku, E. G.; Chelton, D. B.

    1985-01-01

    Sea surface temperature (SST) is measured from space by the advanced very high resolution radiometer (AVHRR), scanning multichannel microwave radiometer (SMMR), high resolution infrared sounder (HIRS) and VISSR atmospheric sounder (VAS). Typical accuracies have been reported from 0.5 C regionally to 2.0 C on a global basis. To evaluate the accuracy of the satellite-derived sea surface temperatures, a series of three workshops was organized to provide uniform data reduction and analysis. The analytical techniques used to intercompare satellite and in situ measurements are described in detail. Selected results showed the overall average rms errors were in the range 0.5-1.0 C.

  4. Neutral Hydrogen Structures Trace Dust Polarization Angle: Implications for Cosmic Microwave Background Foregrounds

    NASA Astrophysics Data System (ADS)

    Clark, S. E.; Hill, J. Colin; Peek, J. E. G.; Putman, M. E.; Babler, B. L.

    2015-12-01

    Using high-resolution data from the Galactic Arecibo L-Band Feed Array HI (GALFA-Hi) survey, we show that linear structure in Galactic neutral hydrogen (Hi) correlates with the magnetic field orientation implied by Planck 353 GHz polarized dust emission. The structure of the neutral interstellar medium is more tightly coupled to the magnetic field than previously known. At high Galactic latitudes, where the Planck data are noise dominated, the Hi data provide an independent constraint on the Galactic magnetic field orientation, and hence the local dust polarization angle. We detect strong cross-correlations between template maps constructed from estimates of dust intensity combined with either Hi-derived angles, starlight polarization angles, or Planck 353 GHz angles. The Hi data thus provide a new tool in the search for inflationary gravitational wave B -mode polarization in the cosmic microwave background, which is currently limited by dust foreground contamination.

  5. Neutral Hydrogen Structures Trace Dust Polarization Angle: Implications for Cosmic Microwave Background Foregrounds.

    PubMed

    Clark, S E; Hill, J Colin; Peek, J E G; Putman, M E; Babler, B L

    2015-12-11

    Using high-resolution data from the Galactic Arecibo L-Band Feed Array HI (GALFA-Hi) survey, we show that linear structure in Galactic neutral hydrogen (Hi) correlates with the magnetic field orientation implied by Planck 353 GHz polarized dust emission. The structure of the neutral interstellar medium is more tightly coupled to the magnetic field than previously known. At high Galactic latitudes, where the Planck data are noise dominated, the Hi data provide an independent constraint on the Galactic magnetic field orientation, and hence the local dust polarization angle. We detect strong cross-correlations between template maps constructed from estimates of dust intensity combined with either Hi-derived angles, starlight polarization angles, or Planck 353 GHz angles. The Hi data thus provide a new tool in the search for inflationary gravitational wave B-mode polarization in the cosmic microwave background, which is currently limited by dust foreground contamination. PMID:26705622

  6. Polarization conversion from a thin cavity array in the microwave regime

    PubMed Central

    Tremain, B.; Rance, H. J.; Hibbins, A. P.; Sambles, J. R.

    2015-01-01

    Linearly polarized microwave radiation is shown to have its plane of polarization converted to the orthogonal state upon reflection from an ultrathin (λ/25) cavity array. The structure benefits from an uncomplicated design consisting of a metallic grating closely separated from a ground plane by a dielectric spacer. A single set of periodically spaced slits (monograting) exhibits polarization conversion when the normally incident electric field is aligned at 45° to the slits. Two orthogonal sets of slits (bigrating) allows this narrow-band effect to be broadened when the two orthogonal resonances are separated in frequency. We optimise the design and experimentally demonstrate near loss-less polarization conversion (95% of the incident intensity) across a 3.1 GHz frequency band. Finally, we study the dependence of the structure's performance on incident angle and slit width. PMID:25797210

  7. Phase-space structures and ionization dynamics of the hydrogen atom in elliptically polarized microwaves

    NASA Astrophysics Data System (ADS)

    Shchekinova, E.; Chandre, C.; Uzer, T.

    2006-10-01

    The multiphoton ionization of hydrogen atoms in a strong elliptically polarized microwave field exhibits complex features that are not observed for ionization in circular and linear polarized fields. Experimental data reveal high sensitivity of ionization dynamics to the small changes of the field polarization. The multidimensional nature of the problem makes widely used diagnostics of dynamics, such as Poincaré surfaces of section, impractical. We analyze the phase-space dynamics using the finite time stability analysis rendered by the fast Lyapunov indicators technique. The concept of zero-velocity surface is used to initialize the calculations and visualize the dynamics. Our analysis provides stability maps calculated for the initial energy at the maximum and below the saddle of the zero-velocity surface. We estimate qualitatively the dependence of ionization thresholds on the parameters of the applied field, such as polarization and scaled amplitude.

  8. Microwave Polarized Signatures Generated within Cloud Systems: SSM/I Observations Interpreted with Radiative Transfer Simulations

    NASA Technical Reports Server (NTRS)

    Prigent, Catherine; Pardo, Juan R.; Mishchenko, Michael I.; Rossow, Willaim B.; Hansen, James E. (Technical Monitor)

    2001-01-01

    Special Sensor Microwave /Imager (SSM/I) observations in cloud systems are studied over the tropics. Over optically thick cloud systems, presence of polarized signatures at 37 and 85 GHz is evidenced and analyzed with the help of cloud top temperature and optical thickness extracted from visible and IR satellite observations. Scattering signatures at 85 GHz (TbV(85) less than or = 250 K) are associated with polarization differences greater than or = 6 K, approx. 50%, of the time over ocean and approx. 40% over land. In addition. over thick clouds the polarization difference at 37 GHz is rarely negligible. The polarization differences at 37 and 85 GHz do not stem from the surface but are generated in regions of relatively homogeneous clouds having high liquid water content. To interpret the observations, a radiative transfer model that includes the scattering by non-spherical particles is developed. based on the T-matrix approach and using the doubling and adding method. In addition to handling randomly and perfectly oriented particles, this model can also simulate the effect of partial orientation of the hydrometeors. Microwave brightness temperatures are simulated at SSM/I frequencies and are compared with the observations. Polarization differences of approx. 2 K can be simulated at 37 GHz over a rain layer, even using spherical drops. The polarization difference is larger for oriented non-spherical particles. The 85 GHz simulations are very sensitive to the ice phase of the cloud. Simulations with spherical particles or with randomly oriented non-spherical ice particles cannot replicate the observed polarization differences. However, with partially oriented non-spherical particles, the observed polarized signatures at 85 GHz are explained, and the sensitivity of the scattering characteristics to the particle size, asphericity, and orientation is analyzed. Implications on rain and ice retrievals are discussed.

  9. A microwave satellite water vapour column retrieval for polar winter conditions

    NASA Astrophysics Data System (ADS)

    Perro, Christopher; Lesins, Glen; Duck, Thomas J.; Cadeddu, Maria

    2016-05-01

    A new microwave satellite water vapour retrieval for the polar winter atmosphere is presented. The retrieval builds on the work of Miao et al. (2001) and Melsheimer and Heygster (2008), employing auxiliary information for atmospheric conditions and numerical optimization. It was tested using simulated and actual measurements from the Microwave Humidity Sounder (MHS) satellite instruments. Ground truth was provided by the G-band vapour radiometer (GVR) at Barrow, Alaska. For water vapour columns less than 6 kg m-2, comparisons between the retrieval and GVR result in a root mean square (RMS) deviation of 0.39 kg m-2 and a systematic bias of 0.08 kg m-2. These results are compared with RMS deviations and biases at Barrow for the retrieval of Melsheimer and Heygster (2008), the AIRS and MIRS satellite data products, and the ERA-Interim, NCEP, JRA-55, and ASR reanalyses. When applied to MHS measurements, the new retrieval produces a smaller RMS deviation and bias than for the earlier retrieval and satellite data products. The RMS deviations for the new retrieval were comparable to those for the ERA-Interim, JRA-55, and ASR reanalyses; however, the MHS retrievals have much finer horizontal resolution (15 km at nadir) and reveal more structure. The new retrieval can be used to obtain pan-Arctic maps of water vapour columns of unprecedented quality. It may also be applied to measurements from the Special Sensor Microwave/Temperature 2 (SSM/T2), Advanced Microwave Sounding Unit B (AMSU-B), Special Sensor Microwave Imager/Sounder (SSMIS), Advanced Technology Microwave Sounder (ATMS), and Chinese MicroWave Humidity Sounder (MWHS) instruments.

  10. Characteristics of 13.9 GHz radar scattering from oil films on the sea surface

    NASA Technical Reports Server (NTRS)

    Johnson, J. W.; Croswell, W. F.

    1982-01-01

    Aircraft microwave scatterometer measurements are presented, which were made in 1979 as part of a project to study the response of a number of active and passive microwave and optical remote sensors to an oil-covered sea surface conducted by NASA Langley Research Center. A 13.9-GHz Doppler scatterometer with a fan beam antenna and coherent detection was used to measure radar backscatter as a function of incidence angle. The radar scattering signature of the clear surface and signatures of the surface covered with various crude oil films are compared. Reductions in Ku band microwave backscatter up to 14 dB are observed for both treated and untreated LaRosa and Murban crude oil films deposited on the sea surface. Maximum Ku band sensitivity to the effects of the oil in terms of differential scatter is observed in the 25-35 deg incidence angle region.

  11. Dielectric properties measurement method in the microwave frequencies range for non-polar/polar liquid mixtures characterization

    NASA Astrophysics Data System (ADS)

    Surducan, E.; Neamtu, C.; Ienciu, M.; Surducan, V.; Limare, A.; Fourel, L.

    2015-12-01

    We present a method based on dielectric properties measurements over a large spectrum of frequencies, in the microwave (MW) domain, in order to characterize a liquid mixture. The liquid mixtures consist of non-polar fluids (silicone oil, diesel fuel) and polar additives, in order to increase the specific MW absorption of the mixture for further MW power processing. We have measured the MW specific absorptions for mixtures of silicone oil with 20% and 30% (w/w) isopropanol. In both cases, the mixtures are sufficiently stable over time to allow further studies of thermal convection dynamics initiated by MW heating. For a mixture of diesel fuel with 10% (w/w) alkyl polyglycoside, the main observation was that its MW specific absorption varies over time after the mechanical mixing process.

  12. Microwave field distribution in a magic angle spinning dynamic nuclear polarization NMR probe

    NASA Astrophysics Data System (ADS)

    Nanni, Emilio A.; Barnes, Alexander B.; Matsuki, Yoh; Woskov, Paul P.; Corzilius, Björn; Griffin, Robert G.; Temkin, Richard J.

    2011-05-01

    We present a calculation of the microwave field distribution in a magic angle spinning (MAS) probe utilized in dynamic nuclear polarization (DNP) experiments. The microwave magnetic field (B 1 S) profile was obtained from simulations performed with the High Frequency Structure Simulator (HFSS) software suite, using a model that includes the launching antenna, the outer Kel-F stator housing coated with Ag, the RF coil, and the 4 mm diameter sapphire rotor containing the sample. The predicted average B 1 S field is 13 μT/W 1/2, where S denotes the electron spin. For a routinely achievable input power of 5 W the corresponding value is γSB 1 S = 0.84 MHz. The calculations provide insights into the coupling of the microwave power to the sample, including reflections from the RF coil and diffraction of the power transmitted through the coil. The variation of enhancement with rotor wall thickness was also successfully simulated. A second, simplified calculation was performed using a single pass model based on Gaussian beam propagation and Fresnel diffraction. This model provided additional physical insight and was in good agreement with the full HFSS simulation. These calculations indicate approaches to increasing the coupling of the microwave power to the sample, including the use of a converging lens and fine adjustment of the spacing of the windings of the RF coil. The present results should prove useful in optimizing the coupling of microwave power to the sample in future DNP experiments. Finally, the results of the simulation were used to predict the cross effect DNP enhancement ( ɛ) vs. ω1 S/(2 π) for a sample of 13C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment.

  13. Microwave field distribution in a magic angle spinning dynamic nuclear polarization NMR probe.

    PubMed

    Nanni, Emilio A; Barnes, Alexander B; Matsuki, Yoh; Woskov, Paul P; Corzilius, Björn; Griffin, Robert G; Temkin, Richard J

    2011-05-01

    We present a calculation of the microwave field distribution in a magic angle spinning (MAS) probe utilized in dynamic nuclear polarization (DNP) experiments. The microwave magnetic field (B(1S)) profile was obtained from simulations performed with the High Frequency Structure Simulator (HFSS) software suite, using a model that includes the launching antenna, the outer Kel-F stator housing coated with Ag, the RF coil, and the 4mm diameter sapphire rotor containing the sample. The predicted average B(1S) field is 13μT/W(1/2), where S denotes the electron spin. For a routinely achievable input power of 5W the corresponding value is γ(S)B(1S)=0.84MHz. The calculations provide insights into the coupling of the microwave power to the sample, including reflections from the RF coil and diffraction of the power transmitted through the coil. The variation of enhancement with rotor wall thickness was also successfully simulated. A second, simplified calculation was performed using a single pass model based on Gaussian beam propagation and Fresnel diffraction. This model provided additional physical insight and was in good agreement with the full HFSS simulation. These calculations indicate approaches to increasing the coupling of the microwave power to the sample, including the use of a converging lens and fine adjustment of the spacing of the windings of the RF coil. The present results should prove useful in optimizing the coupling of microwave power to the sample in future DNP experiments. Finally, the results of the simulation were used to predict the cross effect DNP enhancement (ϵ) vs. ω(1S)/(2π) for a sample of (13)C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment. PMID:21382733

  14. Microwave Field Distribution in a Magic Angle Spinning Dynamic Nuclear Polarization NMR Probe

    PubMed Central

    Nanni, Emilio A.; Barnes, Alexander B.; Matsuki, Yoh; Woskov, Paul P.; Corzilius, Björn; Griffin, Robert G.; Temkin, Richard J.

    2011-01-01

    We present a calculation of the microwave field distribution in a magic angle spinning (MAS) probe utilized in dynamic nuclear polarization (DNP) experiments. The microwave magnetic field (B1S) profile was obtained from simulations performed with the High Frequency Structure Simulator (HFSS) software suite, using a model that includes the launching antenna, the outer Kel-F stator housing coated with Ag, the RF coil, and the 4 mm diameter sapphire rotor containing the sample. The predicted average B1S field is 13µT/W1/2, where S denotes the electron spin. For a routinely achievable input power of 5 W the corresponding value is γ SB1S = 0.84 MHz. The calculations provide insights into the coupling of the microwave power to the sample, including reflections from the RF coil and diffraction of the power transmitted through the coil. The variation of enhancement with rotor wall thickness was also successfully simulated. A second, simplified calculation was performed using a single pass model based on Gaussian beam propagation and Fresnel diffraction. This model provided additional physical insight and was in good agreement with the full HFSS simulation. These calculations indicate approaches to increasing the coupling of the microwave power to the sample, including the use of a converging lens and fine adjustment of the spacing of the windings of the RF coil. The present results should prove useful in optimizing the coupling of microwave power to the sample in future DNP experiments. Finally, the results of the simulation were used to predict the cross effect DNP enhancement (ε) vs. ω1S/(2π) for a sample of 13C-urea dissolved in a 60:40 glycerol/water mixture containing the polarizing agent TOTAPOL; very good agreement was obtained between theory and experiment. PMID:21382733

  15. Sea surface and remotely sensed temperatures off Cape Mendocino, California

    NASA Technical Reports Server (NTRS)

    Breaker, L. C.; Arvesen, J. C.; Frydenlund, D.; Myers, J. S.; Short, K.

    1985-01-01

    During September 3 to 5, 1979, a multisensor oceanographic experiment was conducted off Cape Mendocino, California. The purpose of this experiment was to validate the use of remote sensing techniques over an area along the U.S. west coast where coasted upwelling is known to be intense. Remotely sensed mutlispectral data, including thermal infrared imagery, were collected above an upwelling feature off Cape Mendocino. Data were acquired from the TIRNOS-N and NOAA-6 polar orbiting satellites, the NASA Ames Research Center's high altitude U-2 aircraft, and a U.S. Coast Guard C-130 aircraft. Supporting surface truth data over the same feature were collected aboard the National Oceanic and Atmospheric Administration (NOAA) ship, OCEANOGRAPHER. Atmospheric soundings were also taken aboard the ship. The results indicate that shipboard measurements of sea surface temperatures can be reproduction within 1 C or better through remote observation of absolute infrared radiance values (whether measured aboard the NOAA polar orbiting satellite, the U-2 aircraft, or the Coast Guard aircraft) by using appropriate atmospheric corrections. Also, the patterns of sea surface temperature which were derived independently from the various remote platforms provide a consistent interpretation of the surface temperature field.

  16. Systematic Effects in Polarizing Fourier Transform Spectrometers for Cosmic Microwave Background Observations

    NASA Astrophysics Data System (ADS)

    Nagler, Peter C.; Fixsen, Dale J.; Kogut, Alan; Tucker, Gregory S.

    2015-11-01

    The detection of the primordial B-mode polarization signal of the cosmic microwave background (CMB) would provide evidence for inflation. Yet as has become increasingly clear, the detection of a such a faint signal requires an instrument with both wide frequency coverage to reject foregrounds and excellent control over instrumental systematic effects. Using a polarizing Fourier transform spectrometer (FTS) for CMB observations meets both of these requirements. In this work, we present an analysis of instrumental systematic effects in polarizing FTSs, using the Primordial Inflation Explorer (PIXIE) as a worked example. We analytically solve for the most important systematic effects inherent to the FTS—emissive optical components, misaligned optical components, sampling and phase errors, and spin synchronous effects—and demonstrate that residual systematic error terms after corrections will all be at the sub-nK level, well below the predicted 100 nK B-mode signal.

  17. Optically controlled microwave phase shifter based on nonlinear polarization rotation in a highly nonlinear fiber.

    PubMed

    Li, Wei; Sun, Wen Hui; Wang, Wen Ting; Zhu, Ning Hua

    2014-06-01

    This Letter reports an optically controlled microwave phase shifter with an ultra-wideband working bandwidth and a full 360° phase shifting range based on nonlinear polarization rotation (NPR) in a highly nonlinear fiber (HNLF). A continuous wave probe light is modulated by a polarization modulator (PolM) that is driven by a microwave signal to be phase shifted. The optical carrier and the first-order sidebands of the probe light experience different phase shifts due to the NPR induced by the control light in the HNLF. An optical bandpass filter is used to realize single-sideband modulation of the probe light by removing one of the first-order sidebands, as well as to reject the control light. After detecting by a photodetector, the phase of the recovered microwave signal is continuously tunable by adjusting the power of the control light. The proposed approach is theoretically analyzed and experimentally verified. A full 360° tunable phase shift is realized over an ultra-wideband frequency range from 8 to 38 GHz when the power of the control light is tuned from 0 to 570 mW. PMID:24876035

  18. Implementation of a widely tunable microwave signal generator based on dual-polarization fiber grating laser.

    PubMed

    Yuan, Qiang; Liang, Yizhi; Jin, Long; Cheng, Linghao; Guan, Bai-Ou

    2015-02-01

    In this paper, we demonstrate the implementation of a widely tunable microwave signal generator based on a dual-polarization fiber grating laser. The laser contains two strong, wavelength-matched Bragg gratings photoinscribed in an Er-doped fiber and emits two polarization modes when pumped with a 980 nm laser diode. By beating the two modes, a microwave signal with a signal-to-noise ratio over 60 dB can be obtained. For a free running laser the fluctuations in intensity and frequency of the microwave signal are ±1  dB and ±5  kHz, respectively, and the noise level is about -40  dBc/Hz at 1 kHz. The frequency can be continuously tuned from 1.8 to 15.1 GHz, by transversely loading the laser cavity and changing the intracavity birefringence by use of a piezoelectric transducer-based mechanical device. The measured response time rate of tuning is about 90 MHz/μs and the intensity fluctuation at different frequencies is less than ±1.5  dB. The frequency fluctuation under loading is controlled within 1 MHz by introducing an electrical feedback. PMID:25967802

  19. Wind-Driven Angular Dependence of Sea-Surface Reflectance Measured with an Airborne Doppler Lidar

    NASA Technical Reports Server (NTRS)

    Tratt, David M.; Menzies, Robert T.; Cutten, Dean R.

    1998-01-01

    The effects of wind-stress on the optical properties of the ocean surface have been studied for several decades. In particular, the classic study by Cox and Munk (1954) linking sea-surface wind field to wave slope statistics provides a phenomenology by which the sea-surface wind velocity can be estimated from direct measurement of the wave-modulated surface reflectance. A limited number of studies along these lines have been conducted using airborne or spaceborne lidar systems. In these instances, truthing was provided by in situ ship reports or satellite microwave remote sensing instruments (e.g., ERS scatterometer, SSM/I). During the second deployment of the MACAWS Doppler wind lidar in the summer of 1996 measurements of sea-surface reflectance as a function of azimuth- and nadir-viewing angles were acquired off the California coast. MACAWS data products include directly measured winds, as well as calibrated backscatter/reflectance profiles, thus enabling comparison of the winds inferred from sea-surface reflectance measurements with those deriving from the Doppler-processed direct line-of-sight (LOS) estimates. Additional validation data was extracted from the ERS and SSM/I satellite microwave sensor archives maintained by the JPL Physical Oceanography Distributed Active Archive Center (PO- DAAC).

  20. 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.

  1. Circularly polarized microwaves for magnetic resonance study in the GHz range: Application to nitrogen-vacancy in diamonds

    SciTech Connect

    Mrózek, M. Rudnicki, D. S.; Gawlik, W.; Mlynarczyk, J.

    2015-07-06

    The ability to create time-dependent magnetic fields of controlled polarization is essential for many experiments with magnetic resonance. We describe a microstrip circuit that allows us to generate strong magnetic field at microwave frequencies with arbitrary adjusted polarization. The circuit performance is demonstrated by applying it to an optically detected magnetic resonance and Rabi nutation experiments in nitrogen-vacancy color centers in diamond. Thanks to high efficiency of the proposed microstrip circuit and degree of circular polarization of 85%; it is possible to address the specific spin states of a diamond sample using a low power microwave generator. The circuit may be applied to a wide range of magnetic resonance experiments with a well-controlled polarization of microwaves.

  2. Satellite Altimetric Mappings of Arctic Sea Surface Topography: An Evaluation

    NASA Astrophysics Data System (ADS)

    McAdoo, D. C.; Farrell, S. L.; Laxon, S. W.; Zwally, H. J.; Yi, D.; Coakley, B.; Cochran, J. R.

    2008-12-01

    Increasingly precise mappings of sea surface topography (SST) in the Arctic Ocean are being derived from near-polar satellite altimeters such as the laser system - Geoscience Laser Altimeter System (GLAS) - onboard NASA's ICESat and the radar systems onboard ESA's ERS-2 and Envisat. These mappings of sea surface topography (SST) have important oceanographic and geodetic applications. For example, because the geoid does conform closely to sea surface topography we can use altimetric SST measurements to estimate gravity (e.g., see the ARCtic Satellite-only (ARCS) field, McAdoo et al. 2008) particularly in regions lacking "true" surface gravity observations. Also, by differencing mappings of mean SST with a gravimetric geoid - particularly a geoid underpinned by a GRACE mean field model - we can estimate the dynamic ocean topography (DOT) and circulation of the Arctic Ocean. However, accurate estimates of DOT (e.g. accuracies better than a decimeter) require that we have very precise knowledge of the geoid and mean SST. Comparing a mean SST derived from ICESat/GLAS data spanning several years with a corresponding mean SST derived from ERS-2 data reveals short- wavelength differences or discrepancies of order 40 - 60 cm in certain areas of the Arctic Ocean such as the Chukchi Borderland. In order to attribute a portion of these discrepancies to laser or radar altimeter measurement error, we convert these mean SST fields to equivalent gravity fields and compare with gravity observations from several of the unclassified SCICEX/U.S. Navy submarine cruises (Edwards and Coakley, 2003; http://www.ldeo.columbia.edu/res/pi/SCICEX/ ). This comparison enables us to quantify short-wavelength errors in both laser and radar altimetric mean SST models.

  3. The meteorological effects on microwave apparent temperatures looking downward over a smooth sea

    NASA Technical Reports Server (NTRS)

    Wu, S.

    1973-01-01

    The effects of clouds and rain on microwave apparent temperatures for a flat sea surface are examined. The presence of clouds and rain can be expressed as a change of absorption coefficient and the total absorption is computed as the sum of individual effects. Various cloud and rain models proposed by meteorologists are employed to compute the microwave apparent temperature when viewing downward through these model atmospheres. It is shown that stratus, cumulus, overcast, and rain all contribute significantly to the observed temperature. Larger sensitivities to clouds and rain are observed for horizontally polarized apparent temperature at large nadir angles than for vertically polarized apparent temperature.

  4. Multiresolution internal template cleaning: an application to the Wilkinson Microwave Anisotropy Probe 7-yr polarization data

    NASA Astrophysics Data System (ADS)

    Fernández-Cobos, R.; Vielva, P.; Barreiro, R. B.; Martínez-González, E.

    2012-03-01

    The cosmic microwave background (CMB) radiation data obtained by different experiments contain, besides the desired signal, a superposition of microwave sky contributions. Using a wavelet decomposition on the sphere, we present a fast and robust method to recover the CMB signal from microwave maps. We present an application to the Wilkinson Microwave Anisotropy Probe (WMAP) polarization data, which shows its good performance, particularly in very polluted regions of the sky. The applied wavelet has the advantages that it requires little computational time in its calculations, it is adapted to the HEALPIX pixelization scheme and it offers the possibility of multiresolution analysis. The decomposition is implemented as part of a fully internal template fitting method, minimizing the variance of the resulting map at each scale. Using a χ2 characterization of the noise, we find that the residuals of the cleaned maps are compatible with those expected from the instrumental noise. The maps are also comparable to those obtained from the WMAP team, but in our case we do not make use of external data sets. In addition, at low resolution, our cleaned maps present a lower level of noise. The E-mode power spectrum ? is computed at high and low resolutions, and a cross-power spectrum ? is also calculated from the foreground reduced maps of temperature given by WMAP and our cleaned maps of polarization at high resolution. These spectra are consistent with the power spectra supplied by the WMAP team. We detect the E-mode acoustic peak at ℓ˜ 400, as predicted by the standard ΛCDM model. The B-mode power spectrum ? is compatible with zero.

  5. Low-Temperature Dynamic Nuclear Polarization at 9.4 Tesla With a 30 Milliwatt Microwave Source

    PubMed Central

    Thurber, Kent R.; Yau, Wai-Ming; Tycko, Robert

    2010-01-01

    Dynamic nuclear polarization (DNP) can provide large signal enhancements in nuclear magnetic resonance (NMR) by transfer of polarization from electron spins to nuclear spins. We discuss several aspects of DNP experiments at 9.4 Tesla (400 MHz resonant frequency for 1H, 264 GHz for electron spins in organic radicals) in the 7–80 K temperature range, using a 30 mW, frequency-tunable microwave source and a quasi-optical microwave bridge for polarization control and low-loss microwave transmission. In experiments on frozen glycerol/water doped with nitroxide radicals, DNP signal enhancements up to a factor of 80 are observed (relative to 1H NMR signals with thermal equilibrium spin polarization). The largest sensitivity enhancements are observed with a new triradical dopant, DOTOPA-TEMPO. Field modulation with a 10 G root-mean-squared amplitude during DNP increases the nuclear spin polarizations by up to 135%. Dependencies of 1H NMR signal amplitudes, nuclear spin relaxation times, and DNP build-up times on the dopant and its concentration, temperature, microwave power, and modulation frequency are reported and discussed. The benefits of low-temperature DNP can be dramatic: the 1H spin polarization is increased approximately 1000-fold at 7 K with DNP, relative to thermal polarization at 80 K. PMID:20392658

  6. Low-temperature dynamic nuclear polarization at 9.4 T with a 30 mW microwave source

    NASA Astrophysics Data System (ADS)

    Thurber, Kent R.; Yau, Wai-Ming; Tycko, Robert

    2010-06-01

    Dynamic nuclear polarization (DNP) can provide large signal enhancements in nuclear magnetic resonance (NMR) by transfer of polarization from electron spins to nuclear spins. We discuss several aspects of DNP experiments at 9.4 T (400 MHz resonant frequency for 1H, 264 GHz for electron spins in organic radicals) in the 7-80 K temperature range, using a 30 mW, frequency-tunable microwave source and a quasi-optical microwave bridge for polarization control and low-loss microwave transmission. In experiments on frozen glycerol/water doped with nitroxide radicals, DNP signal enhancements up to a factor of 80 are observed (relative to 1H NMR signals with thermal equilibrium spin polarization). The largest sensitivity enhancements are observed with a new triradical dopant, DOTOPA-TEMPO. Field modulation with a 10 G root-mean-squared amplitude during DNP increases the nuclear spin polarizations by up to 135%. Dependencies of 1H NMR signal amplitudes, nuclear spin relaxation times, and DNP build-up times on the dopant and its concentration, temperature, microwave power, and modulation frequency are reported and discussed. The benefits of low-temperature DNP can be dramatic: the 1H spin polarization is increased approximately 1000-fold at 7 K with DNP, relative to thermal polarization at 80 K.

  7. Electromagnetic Wave Propagation over Oil-Covered Sea Surface

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Jin, Wei; Guo, Li-Xin

    2012-07-01

    An exhaustive analysis of electromagnetic wave propagation over an oil-covered sea surface in an evaporation duct environment is studied in comparison with those of the oil-free sea surface. Instead of using the traditional rms height formula, which only considers the oil-free sea surface, we reduce the rms height of a one-dimensional oil-covered sea surface based on the Pierson-Moskowitz sea spectrum. Then, the electromagnetic wave propagation over the oil-covered sea surface in an evaporation duct environment with different wind speeds and frequencies is discussed by the parabolic equation for a fully oil-covered sea surface. In addition, the influence of the fractional filling factor on the electromagnetic wave propagation over non-fully oil-covered sea surface is also investigated. The results show that the oil film can reduce the sea surface roughness and strengthen the trapping effect in an evaporation duct environment.

  8. MEASUREMENT OF COSMIC MICROWAVE BACKGROUND POLARIZATION POWER SPECTRA FROM TWO YEARS OF BICEP DATA

    SciTech Connect

    Chiang, H. C.; Barkats, D.; Bock, J. J.; Hristov, V. V.; Jones, W. C.; Kovac, J. M.; Lange, A. E.; Mason, P. V.; Matsumura, T.; Ade, P. A. R.; Battle, J. O.; Dowell, C. D.; Nguyen, H. T.; Bierman, E. M.; Keating, B. G.; Duband, L.; Hivon, E. F.; Holzapfel, W. L.; Kuo, C. L.; Leitch, E. M.

    2010-03-10

    Background Imaging of Cosmic Extragalactic Polarization (BICEP) is a bolometric polarimeter designed to measure the inflationary B-mode polarization of the cosmic microwave background (CMB) at degree angular scales. During three seasons of observing at the South Pole (2006 through 2008), BICEP mapped {approx}2% of the sky chosen to be uniquely clean of polarized foreground emission. Here, we present initial results derived from a subset of the data acquired during the first two years. We present maps of temperature, Stokes Q and U, E and B modes, and associated angular power spectra. We demonstrate that the polarization data are self-consistent by performing a series of jackknife tests. We study potential systematic errors in detail and show that they are sub-dominant to the statistical errors. We measure the E-mode angular power spectrum with high precision at 21 <= l <= 335, detecting for the first time the peak expected at l {approx} 140. The measured E-mode spectrum is consistent with expectations from a LAMBDACDM model, and the B-mode spectrum is consistent with zero. The tensor-to-scalar ratio derived from the B-mode spectrum is r = 0.02{sup +0.31}{sub -0.26}, or r < 0.72 at 95% confidence, the first meaningful constraint on the inflationary gravitational wave background to come directly from CMB B-mode polarization.

  9. Degree-scale Cosmic Microwave Background Polarization Measurements from Three Years of BICEP1 Data

    NASA Astrophysics Data System (ADS)

    Barkats, D.; Aikin, R.; Bischoff, C.; Buder, I.; Kaufman, J. P.; Keating, B. G.; Kovac, J. M.; Su, M.; Ade, P. A. R.; Battle, J. O.; Bierman, E. M.; Bock, J. J.; Chiang, H. C.; Dowell, C. D.; Duband, L.; Filippini, J.; Hivon, E. F.; Holzapfel, W. L.; Hristov, V. V.; Jones, W. C.; Kuo, C. L.; Leitch, E. M.; Mason, P. V.; Matsumura, T.; Nguyen, H. T.; Ponthieu, N.; Pryke, C.; Richter, S.; Rocha, G.; Sheehy, C.; Kernasovskiy, S. S.; Takahashi, Y. D.; Tolan, J. E.; Yoon, K. W.

    2014-03-01

    BICEP1 is a millimeter-wavelength telescope designed specifically to measure the inflationary B-mode polarization of the cosmic microwave background at degree angular scales. We present results from an analysis of the data acquired during three seasons of observations at the South Pole (2006-2008). This work extends the two-year result published in Chiang et al., with additional data from the third season and relaxed detector-selection criteria. This analysis also introduces a more comprehensive estimation of band power window functions, improved likelihood estimation methods, and a new technique for deprojecting monopole temperature-to-polarization leakage that reduces this class of systematic uncertainty to a negligible level. We present maps of temperature, E- and B-mode polarization, and their associated angular power spectra. The improvement in the map noise level and polarization spectra error bars are consistent with the 52% increase in integration time relative to Chiang et al. We confirm both self-consistency of the polarization data and consistency with the two-year results. We measure the angular power spectra at 21 <= l <= 335 and find that the EE spectrum is consistent with Lambda cold dark matter cosmology, with the first acoustic peak of the EE spectrum now detected at 15σ. The BB spectrum remains consistent with zero. From B-modes only, we constrain the tensor-to-scalar ratio to r = 0.03^{+0.27}_{-0.23}, or r < 0.70 at 95% confidence level.

  10. Dynamic nuclear polarization at 9T using a novel 250 gyrotron microwave source.

    PubMed

    Griffin, Robert G

    2011-12-01

    In the 1990's we initiated development of high frequency gyrotron microwave sources with the goal of performing dynamic nuclear polarization at magnetic fields (∼5-23 T) used in contemporary NMR experiments. This article describes the motivation for these efforts and the developments that led to the operation of a gyrotron source for DNP operating at 250 GHz. We also mention results obtained with this instrument that would have been otherwise impossible absent the increased sensitivity. Finally, we describe recent efforts that have extended DNP to 460 GHz and 700 MHz (1)H frequencies. PMID:22152359

  11. Cosmic 21 cm delensing of microwave background polarization and the minimum detectable energy scale of inflation.

    PubMed

    Sigurdson, Kris; Cooray, Asantha

    2005-11-18

    We propose a new method for removing gravitational lensing from maps of cosmic microwave background (CMB) polarization anisotropies. Using observations of anisotropies or structures in the cosmic 21 cm radiation, emitted or absorbed by neutral hydrogen atoms at redshifts 10 to 200, the CMB can be delensed. We find this method could allow CMB experiments to have increased sensitivity to a background of inflationary gravitational waves (IGWs) compared to methods relying on the CMB alone and may constrain models of inflation which were heretofore considered to have undetectable IGW amplitudes. PMID:16384131

  12. Efficient decomposition of cosmic microwave background polarization maps into pure E, pure B, and ambiguous components

    SciTech Connect

    Bunn, Emory F.

    2011-04-15

    Separation of the B component of a cosmic microwave background (CMB) polarization map from the much larger E component is an essential step in CMB polarimetry. For a map with incomplete sky coverage, this separation is necessarily hampered by the presence of ambiguous modes which could be either E or B modes. I present an efficient pixel-space algorithm for removing the ambiguous modes and separating the map into pure E and B components. The method, which works for arbitrary geometries, does not involve generating a complete basis of such modes and scales the cube of the number of pixels on the boundary of the map.

  13. Dynamic nuclear polarization at 9T using a novel 250 Gyrotron microwave source

    NASA Astrophysics Data System (ADS)

    Griffin, Robert G.

    2011-12-01

    In the 1990's we initiated development of high frequency gyrotron microwave sources with the goal of performing dynamic nuclear polarization at magnetic fields (˜5-23 T) used in contemporary NMR experiments. This article describes the motivation for these efforts and the developments that led to the operation of a gyrotron source for DNP operating at 250 GHz. We also mention results obtained with this instrument that would have been otherwise impossible absent the increased sensitivity. Finally, we describe recent efforts that have extended DNP to 460 GHz and 700 MHz 1H frequencies.

  14. Twentieth-Century Sea Surface Temperature Trends

    PubMed

    Cane; Clement; Kaplan; Kushnir; Pozdnyakov; Seager; Zebiak; Murtugudde

    1997-02-14

    An analysis of historical sea surface temperatures provides evidence for global warming since 1900, in line with land-based analyses of global temperature trends, and also shows that over the same period, the eastern equatorial Pacific cooled and the zonal sea surface temperature gradient strengthened. Recent theoretical studies have predicted such a pattern as a response of the coupled ocean-atmosphere system to an exogenous heating of the tropical atmosphere. This pattern, however, is not reproduced by the complex ocean-atmosphere circulation models currently used to simulate the climatic response to increased greenhouse gases. Its presence is likely to lessen the mean 20th-century global temperature change in model simulations. PMID:9020074

  15. Ocean backscatter across the Gulf Stream sea surface temperature front

    SciTech Connect

    Nghiem, S.V.; Li, F.K.

    1997-06-01

    Ocean backscatter was measured by the Jet Propulsion Laboratory, with the airborne NUSCAT K{sub u}-band scatterometer, across the Gulf Stream sea surface temperature front during the Surface Wave Dynamics Experiment off the coast of Virginia and Maryland in the winter of 1991. Backscatter across the front between the National Oceanic and Atmospheric Administration experimental coastal buoy A (44024) on the cold side and Discus C buoy (44023) on the warm side shows a difference of more than 5 dB for vertical polarization in many cases. This large frontal backscatter change is observed in all upwind, downwind, and crosswind directions. The sea surface temperature difference measured by the buoys was about 9{degrees}C. The corresponding difference in wind speed cannot account for the large backscatter change in view of geophysical model functions depending only on neutral wind velocity such as SASS. The measured backscatter also has larger upwind-downwind and upwind-crosswind ratios compared to the model results. Furthermore, NUSCAT data reveal that upwind backscatter on the cold side was smaller than or close to crosswind backscatter on the warm side for incidence angles between 30{degrees} to 50{degrees}. This suggests that the temperature front can be detected by the scatterometer at these incidence angles for different wind directions in the cold and warm sides.

  16. Global mean sea surface based upon SEASAT altimeter data

    NASA Technical Reports Server (NTRS)

    Marsh, J. G.

    1984-01-01

    A global mean sea surface based upon the SEASAT altimeter data was derived. A combination of crossing arc techniques, accurate SEASAT reference orbits, and a previously computed GOES-3/SEASAT mean sea surface were used in the computation process. This mean sea surface provides a basis for the determination of global ocean circulation patterns and for detailed analysis of the Earth's internal structure. A contour map of the global mean sea surface is presented.

  17. Precise orbit computation and sea surface modeling

    NASA Technical Reports Server (NTRS)

    Wakker, Karel F.; Ambrosius, B. A. C.; Rummel, R.; Vermaat, E.; Deruijter, W. P. M.; Vandermade, J. W.; Zimmerman, J. T. F.

    1991-01-01

    The research project described below is part of a long-term program at Delft University of Technology aiming at the application of European Remote Sensing satellite (ERS-1) and TOPEX/POSEIDON altimeter measurements for geophysical purposes. This program started in 1980 with the processing of Seasat laser range and altimeter height measurements and concentrates today on the analysis of Geosat altimeter data. The objectives of the TOPEX/POSEIDON research project are the tracking of the satellite by the Dutch mobile laser tracking system MTLRS-2, the computation of precise TOPEX/POSEIDON orbits, the analysis of the spatial and temporal distribution of the orbit errors, the improvement of ERS-1 orbits through the information obtained from the altimeter crossover difference residuals for crossing ERS-1 and TOPEX/POSEIDON tracks, the combination of ERS-1 and TOPEX/POSEIDON altimeter data into a single high-precision data set, and the application of this data set to model the sea surface. The latter application will focus on the determination of detailed regional mean sea surfaces, sea surface variability, ocean topography, and ocean currents in the North Atlantic, the North Sea, the seas around Indonesia, the West Pacific, and the oceans around South Africa.

  18. On the influence of resonant scattering on cosmic microwave background polarization anisotropies

    NASA Astrophysics Data System (ADS)

    Hernández-Monteagudo, C.; Rubiño-Martín, J. A.; Sunyaev, R. A.

    2007-10-01

    We implement the theory of resonant scattering in the context of cosmic microwave background (CMB) polarization anisotropies. We compute the changes in the E-mode polarization (EE) and temperature E-mode (TE) CMB power spectra introduced by the scattering on a resonant transition with a given optical depth τX and polarization coefficient E1. The latter parameter, accounting for how anisotropic the scattering is, depends on the exchange of angular momentum in the transition, enabling observational discrimination between different resonances. We use this formalism in two different scenarios: cosmological recombination and cosmological re-ionization. In the context of cosmological recombination, we compute predictions in frequency and multipole space for the change in the TE and EE power spectra introduced by scattering on the Hα and Pα lines of hydrogen. This constitutes a fundamental test of the standard model of recombination, and the sensitivity it requires is comparable to that needed in measuring the primordial CMB B-mode polarization component. In the context of re-ionization, we study the scattering off metals and ions produced by the first stars, and find that polarization anisotropies, apart from providing a consistency test for intensity measurements, give some insight on how re-ionization evolved. Since polarization anisotropies have memory of how anisotropic the line scattering is, they should be able to discern the OI 63.2-μm transition from other possible transitions associated to OIII, NII, NIII, etc. The amplitude of these signals are, however, between 10 and 100 times below the (already challenging) level of CMB B-mode polarization anisotropies.

  19. Cosmic birefringence fluctuations and cosmic microwave background B-mode polarization

    NASA Astrophysics Data System (ADS)

    Lee, Seokcheon; Liu, Guo-Chin; Ng, Kin-Wang

    2015-06-01

    Recently, BICEP2 measurements of the cosmic microwave background (CMB) B-mode polarization has indicated the presence of primordial gravitational waves at degree angular scales, inferring the tensor-to-scalar ratio of r = 0.2 and a running scalar spectral index, provided that dust contamination is low. In this Letter, we show that the existence of the fluctuations of cosmological birefringence can give rise to CMB B-mode polarization that fits BICEP2 data with r < 0.11 and no running of the scalar spectral index. When dust contribution is taken into account, we derive an upper limit on the cosmological birefringence, Aβ2 < 0.0075, where A is the amplitude of birefringence fluctuations that couple to electromagnetism with a coupling strength β.

  20. Synthesis of passive microwave and radar altimeter data for estimating accumulation rates of polar snow

    NASA Technical Reports Server (NTRS)

    Davis, Curt H.

    1993-01-01

    In this paper, we compare dry-snow extinction coefficients derived from radar altimeter data with brightness temperature data from passive microwave measurements over a portion of the East Antarctic plateau. The comparison between the extinction coefficients and the brightness temperatures shows a strong negative correlation, where the correlation coefficients ranged from -0.87 to -0.95. The extinction coefficient of the dry polar snow decreases with increasing surface elevation, while the average brightness temperature increases with surface elevation. Our analysis shows that the observed trends are related to geographic variations in scattering coefficient of snow, which in turn are controlled by variations in surface temperature and snow accumulation rate. By combining information present in the extinction coefficient and brightness temperature data sets, we develop a model that can be used to obtain quantitative estimates of the accumulation rate of dry polar snow.

  1. Microwave maps of the polar ice of the earth. [from Nimbus-5 satellite

    NASA Technical Reports Server (NTRS)

    Gloersen, P.; Wilheit, T. T.; Chang, T. C.; Nordberg, W.; Campbell, W. J.

    1973-01-01

    Synoptic views of the entire polar regions of earth were obtained free of the usual persistent cloud cover using a scanning microwave radiometer operating at a wavelength of 1.55 cm on board the Nimbus-5 satellite. Three different views at each pole are presented utilizing data obtained at approximately one-month intervals during the winter of 1972-1973. The major discoveries resulting from an analysis of these data are as follows: (1) Large discrepancies exist between the climatic norm ice cover depicted in various atlases and the actual extent of the canopies. (2) The distribution of multiyear ice in the north polar region is markedly different from that predicted by existing ice dynamics models. (3) Irregularities in the edge of the Antarctic sea ice pack occur that have neither been observed previously nor anticipated. (4) The brightness temperatures of the Greenland and Antarctica glaciers show interesting contours probably related to the ice and snow morphologic structure.

  2. W-band dual-polarization receiver for array of microwave background anisotropy (AMiBA)

    NASA Astrophysics Data System (ADS)

    Hwang, Yuh-Jing; Chen, Ming-Tang; Jiang, Homing; Chu, Tah-Hsiung; Hsieh, Sun-Nieng; Han, Chi-Chian; Patt, Ferdinand; Ho, West; Huang, Yau-Der; Wilson, Warwick

    2004-10-01

    This is to report on our development for a dual-polarization receiver to detect the cosmic microwave background (CMB) in 85 to 105 GHz band. The receiver is based on a MMIC, HEMT-based LNA developed in the Jet Propulsion Laboratory. A W-band, orthomode transducer (OMT) is used for polarization separation. Most of the RF front-end is located in cryogenics environment at 20K. We have developed a MMIC sub-harmonically pumped diode mixer, operating at 42 GHz, for signal down-conversion. The entire base-band, 2 to 18 GHz, is correlated in a lag-correlator system. The receiver design details and the lab test results will be described in this report.

  3. BAYESIAN INFERENCE OF POLARIZED COSMIC MICROWAVE BACKGROUND POWER SPECTRA FROM INTERFEROMETRIC DATA

    SciTech Connect

    Karakci, Ata; Korotkov, Andrei; Tucker, Gregory S.; Sutter, P. M.; Wandelt, Benjamin D.; Zhang, Le; Timbie, Peter; Bunn, Emory F.

    2013-01-15

    Detection of B-mode polarization of the cosmic microwave background (CMB) radiation is one of the frontiers of observational cosmology. Because they are an order of magnitude fainter than E-modes, it is quite a challenge to detect B-modes. Having more manageable systematics, interferometers prove to have a substantial advantage over imagers in detecting such faint signals. Here, we present a method for Bayesian inference of power spectra and signal reconstruction from interferometric data of the CMB polarization signal by using the technique of Gibbs sampling. We demonstrate the validity of the method in the flat-sky approximation for a simulation of an interferometric observation on a finite patch with incomplete uv-plane coverage, a finite beam size, and a realistic noise model. With a computational complexity of O(n {sup 3/2}), n being the data size, Gibbs sampling provides an efficient method for analyzing upcoming cosmology observations.

  4. Evolution of the linear-polarization-angle-dependence of the radiation-induced magnetoresistance-oscillations with microwave power

    SciTech Connect

    Ye, Tianyu; Mani, R. G.; Wegscheider, W.

    2014-11-10

    We examine the role of the microwave power in the linear polarization angle dependence of the microwave radiation induced magnetoresistance oscillations observed in the high mobility GaAs/AlGaAs two dimensional electron system. The diagonal resistance R{sub xx} was measured at the fixed magnetic fields of the photo-excited oscillatory extrema of R{sub xx} as a function of both the microwave power, P, and the linear polarization angle, θ. Color contour plots of such measurements demonstrate the evolution of the lineshape of R{sub xx} versus θ with increasing microwave power. We report that the non-linear power dependence of the amplitude of the radiation-induced magnetoresistance oscillations distorts the cosine-square relation between R{sub xx} and θ at high power.

  5. Evaluation of the potential of one to three SEASAT-SMMR channels in retrieving sea surface temperature

    NASA Technical Reports Server (NTRS)

    Pandey, P. C.; Kniffen, S.

    1982-01-01

    The scanning multichannel microwave radiometer (SMMR) aboard the SEASAT satellite measured emitted radiation in both horizontal and vertical polarizations at microwave frequencies of 6.6, 10.69, 18.0, 21.0 and 37.0 GHz. Retrieval algorithms, for sea surface temperature (SST) determination, from subsets of one to three SMMR channels are obtained by a two step statistical technique. The technique first selects the best subsets of a given size defined by an R2 criterion (coefficient of determination), of a given size by the application of an efficient 'leaps and bounds' technique on a statistical data base. It then performs a regression analysis on the selected subsets. The statistical data base employed a large (600) set of seasonally and geographically diverse atmospheric and surface parameters for radiative transfer calculations. The results of the study of one to three channel subset retrieval algorithms indicate the possibility of using 6.6V, 6.6H and 18V channels for SST determination from SEASAT-SMMR data.

  6. Extraction of Water from Polar Lunar Permafrost with Microwaves - Dielectric Property Measurements

    NASA Technical Reports Server (NTRS)

    Ethridge, Edwin C.; Kaukler, William

    2009-01-01

    Remote sensing indicates the presence of hydrogen rich regions associated with the lunar poles. The logical hypothesis is that there is cryogenically trapped water ice located in craters at the lunar poles. Some of the craters have been in permanent darkness for a billion years. The presence of water at the poles as well as other scientific advantages of a polar base, have influenced NASA plans for the lunar outpost. The lunar outpost has water and oxygen requirements on the order of 1 ton per year scaling up to as much as 10 tons per year. Microwave heating of the frozen permafrost has unique advantages for water extraction. Proof of principle experiments have successfully demonstrated that microwaves will couple to the cryogenic soil in a vacuum and the sublimed water vapor can be successfully captured on a cold trap. The dielectric properties of lunar soil will determine the hardware requirements for extraction processes. Microwave frequency dielectric property measurements of lunar soil simulant have been measured.

  7. Investigation on the GPS single scattering from a 2-D largescale sea surface

    NASA Astrophysics Data System (ADS)

    Wei, Yiwen; Guo, Lixin

    2014-05-01

    Global positioning system (GPS) signals reflected from the ocean surface can be used for various remote sensing purposes. In this paper, we develop a facet model to simulate the received GPS single from a 2-D largescale sea surface. In this model, the sea surface is envisaged as a two-scale profile on which the long waves are locally approximated by planar facets. The microscopic profile within a facet is assumed to be represented by a set of sinusoidal ripple patches. The complex reflective function of each modified facet is evaluated by a modified formula of the original Bass and Fuks' two-scale model, in which the phase factor of each facet is with the capillary wave modification. The scattering field and the bistatic scattering coefficient of facet model is derived in detail. With received GPS single, we give a detail analysis of the polarization property, the scattering property of GPS scattering signal over the sea surface.

  8. Monte Carlo Calculations of Polarized Microwave Radiation Emerging from Cloud Structures

    NASA Technical Reports Server (NTRS)

    Kummerow, Christian; Roberti, Laura

    1998-01-01

    The last decade has seen tremendous growth in cloud dynamical and microphysical models that are able to simulate storms and storm systems with very high spatial resolution, typically of the order of a few kilometers. The fairly realistic distributions of cloud and hydrometeor properties that these models generate has in turn led to a renewed interest in the three-dimensional microwave radiative transfer modeling needed to understand the effect of cloud and rainfall inhomogeneities upon microwave observations. Monte Carlo methods, and particularly backwards Monte Carlo methods have shown themselves to be very desirable due to the quick convergence of the solutions. Unfortunately, backwards Monte Carlo methods are not well suited to treat polarized radiation. This study reviews the existing Monte Carlo methods and presents a new polarized Monte Carlo radiative transfer code. The code is based on a forward scheme but uses aliasing techniques to keep the computational requirements equivalent to the backwards solution. Radiative transfer computations have been performed using a microphysical-dynamical cloud model and the results are presented together with the algorithm description.

  9. Optical Demonstration of THz, Dual-Polarization Sensitive Microwave Kinetic Inductance Detectors

    NASA Astrophysics Data System (ADS)

    Dober, B.; Austermann, J. A.; Beall, J. A.; Becker, D.; Che, G.; Cho, H. M.; Devlin, M.; Duff, S. M.; Galitzki, N.; Gao, J.; Groppi, C.; Hilton, G. C.; Hubmayr, J.; Irwin, K. D.; McKenney, C. M.; Li, D.; Lourie, N.; Mauskopf, P.; Vissers, M. R.; Wang, Y.

    2016-07-01

    Polarization sensitive, microwave kinetic inductance detectors (MKIDs) are under development for the next generation BLAST instrument (BLAST-TNG). BLAST-TNG is a balloon-borne submillimeter polarimeter designed to study magnetic fields in diffuse dust regions and molecular clouds. We present the design and performance of feedhorn-coupled, dual-polarization sensitive MKIDs fabricated from TiN/Ti multilayer films, which have been optimized for the 250 μm band. Measurements show effective selection of linear polarization and good electrical isolation between the orthogonally crossed X and Y detectors within a single spatial pixel. The detector cross-polar coupling is <3 %. Passband measurements are presented, which demonstrate that the desired band-edges (1.0-1.4 THz) have been achieved. We find a near linear response to the optical load from a blackbody source, which has been observed in previous devices fabricated from TiN. Blackbody-coupled noise measurements demonstrate that the sensitivity of the detectors is limited by photon noise when the optical load is greater than 1 pW.

  10. Measurement of the cosmic microwave background polarization lensing power spectrum with the POLARBEAR experiment.

    PubMed

    Ade, P A R; Akiba, Y; Anthony, A E; Arnold, K; Atlas, M; Barron, D; Boettger, D; Borrill, J; Chapman, S; Chinone, Y; Dobbs, M; Elleflot, T; Errard, J; Fabbian, G; Feng, C; Flanigan, D; Gilbert, A; Grainger, W; Halverson, N W; Hasegawa, M; Hattori, K; Hazumi, M; Holzapfel, W L; Hori, Y; Howard, J; Hyland, P; Inoue, Y; Jaehnig, G C; Jaffe, A; Keating, B; Kermish, Z; Keskitalo, R; Kisner, T; Le Jeune, M; Lee, A T; Linder, E; Leitch, E M; Lungu, M; Matsuda, F; Matsumura, T; Meng, X; Miller, N J; Morii, H; Moyerman, S; Myers, M J; Navaroli, M; Nishino, H; Paar, H; Peloton, J; Quealy, E; Rebeiz, G; Reichardt, C L; Richards, P L; Ross, C; Schanning, I; Schenck, D E; Sherwin, B; Shimizu, A; Shimmin, C; Shimon, M; Siritanasak, P; Smecher, G; Spieler, H; Stebor, N; Steinbach, B; Stompor, R; Suzuki, A; Takakura, S; Tomaru, T; Wilson, B; Yadav, A; Zahn, O

    2014-07-11

    Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial cosmic microwave background (CMB) and thereby induces new, small-scale B-mode polarization. This signal carries detailed information about the distribution of all the gravitating matter between the observer and CMB last scattering surface. We report the first direct evidence for polarization lensing based on purely CMB information, from using the four-point correlations of even- and odd-parity E- and B-mode polarization mapped over ∼30 square degrees of the sky measured by the POLARBEAR experiment. These data were analyzed using a blind analysis framework and checked for spurious systematic contamination using null tests and simulations. Evidence for the signal of polarization lensing and lensing B modes is found at 4.2σ (stat+sys) significance. The amplitude of matter fluctuations is measured with a precision of 27%, and is found to be consistent with the Lambda cold dark matter cosmological model. This measurement demonstrates a new technique, capable of mapping all gravitating matter in the Universe, sensitive to the sum of neutrino masses, and essential for cleaning the lensing B-mode signal in searches for primordial gravitational waves. PMID:25062161

  11. Rotation of the cosmic microwave background polarization from weak gravitational lensing.

    PubMed

    Dai, Liang

    2014-01-31

    When a cosmic microwave background (CMB) photon travels from the surface of last scatter through spacetime metric perturbations, the polarization vector may rotate about its direction of propagation. This gravitational rotation is distinct from, and occurs in addition to, the lensing deflection of the photon trajectory. This rotation can be sourced by linear vector or tensor metric perturbations and is fully coherent with the curl deflection field. Therefore, lensing corrections to the CMB polarization power spectra as well as the temperature-polarization cross correlations due to nonscalar perturbations are modified. The rotation does not affect lensing by linear scalar perturbations, but needs to be included when calculations go to higher orders. We present complete results for weak lensing of the full-sky CMB power spectra by general linear metric perturbations, taking into account both deflection of the photon trajectory and rotation of the polarization. For the case of lensing by gravitational waves, we show that the B modes induced by the rotation largely cancel those induced by the curl component of deflection. PMID:24580435

  12. Optical Demonstration of THz, Dual-Polarization Sensitive Microwave Kinetic Inductance Detectors

    NASA Astrophysics Data System (ADS)

    Dober, B.; Austermann, J. A.; Beall, J. A.; Becker, D.; Che, G.; Cho, H. M.; Devlin, M.; Duff, S. M.; Galitzki, N.; Gao, J.; Groppi, C.; Hilton, G. C.; Hubmayr, J.; Irwin, K. D.; McKenney, C. M.; Li, D.; Lourie, N.; Mauskopf, P.; Vissers, M. R.; Wang, Y.

    2016-07-01

    Polarization sensitive, microwave kinetic inductance detectors (MKIDs) are under development for the next generation BLAST instrument (BLAST-TNG). BLAST-TNG is a balloon-borne submillimeter polarimeter designed to study magnetic fields in diffuse dust regions and molecular clouds. We present the design and performance of feedhorn-coupled, dual-polarization sensitive MKIDs fabricated from TiN/Ti multilayer films, which have been optimized for the 250 \\upmu m band. Measurements show effective selection of linear polarization and good electrical isolation between the orthogonally crossed X and Y detectors within a single spatial pixel. The detector cross-polar coupling is <3 %. Passband measurements are presented, which demonstrate that the desired band-edges (1.0-1.4 THz) have been achieved. We find a near linear response to the optical load from a blackbody source, which has been observed in previous devices fabricated from TiN. Blackbody-coupled noise measurements demonstrate that the sensitivity of the detectors is limited by photon noise when the optical load is greater than 1 pW.

  13. Measurement of the Cosmic Microwave Background Polarization Lensing Power Spectrum with the POLARBEAR Experiment

    NASA Astrophysics Data System (ADS)

    Ade, P. A. R.; Akiba, Y.; Anthony, A. E.; Arnold, K.; Atlas, M.; Barron, D.; Boettger, D.; Borrill, J.; Chapman, S.; Chinone, Y.; Dobbs, M.; Elleflot, T.; Errard, J.; Fabbian, G.; Feng, C.; Flanigan, D.; Gilbert, A.; Grainger, W.; Halverson, N. W.; Hasegawa, M.; Hattori, K.; Hazumi, M.; Holzapfel, W. L.; Hori, Y.; Howard, J.; Hyland, P.; Inoue, Y.; Jaehnig, G. C.; Jaffe, A.; Keating, B.; Kermish, Z.; Keskitalo, R.; Kisner, T.; Le Jeune, M.; Lee, A. T.; Linder, E.; Leitch, E. M.; Lungu, M.; Matsuda, F.; Matsumura, T.; Meng, X.; Miller, N. J.; Morii, H.; Moyerman, S.; Myers, M. J.; Navaroli, M.; Nishino, H.; Paar, H.; Peloton, J.; Quealy, E.; Rebeiz, G.; Reichardt, C. L.; Richards, P. L.; Ross, C.; Schanning, I.; Schenck, D. E.; Sherwin, B.; Shimizu, A.; Shimmin, C.; Shimon, M.; Siritanasak, P.; Smecher, G.; Spieler, H.; Stebor, N.; Steinbach, B.; Stompor, R.; Suzuki, A.; Takakura, S.; Tomaru, T.; Wilson, B.; Yadav, A.; Zahn, O.; Polarbear Collaboration

    2014-07-01

    Gravitational lensing due to the large-scale distribution of matter in the cosmos distorts the primordial cosmic microwave background (CMB) and thereby induces new, small-scale B-mode polarization. This signal carries detailed information about the distribution of all the gravitating matter between the observer and CMB last scattering surface. We report the first direct evidence for polarization lensing based on purely CMB information, from using the four-point correlations of even- and odd-parity E- and B-mode polarization mapped over ˜30 square degrees of the sky measured by the POLARBEAR experiment. These data were analyzed using a blind analysis framework and checked for spurious systematic contamination using null tests and simulations. Evidence for the signal of polarization lensing and lensing B modes is found at 4.2σ (stat +sys) significance. The amplitude of matter fluctuations is measured with a precision of 27%, and is found to be consistent with the Lambda cold dark matter cosmological model. This measurement demonstrates a new technique, capable of mapping all gravitating matter in the Universe, sensitive to the sum of neutrino masses, and essential for cleaning the lensing B-mode signal in searches for primordial gravitational waves.

  14. A high-power microwave circular polarizer and its application on phase shifter

    NASA Astrophysics Data System (ADS)

    Shao, Hao; Hu, Yongmei; Chang, Chao; Guo, Letian

    2016-04-01

    A high-power waveguide dual circular polarizer was theoretically designed and proof-of-principle was experimentally tested. It consists of two incident rectangular waveguides with a perpendicular H-plane junction, one circular waveguide with a pair of trapezoidal grooves coupled in E-plane at the top, a spherical crown located at the bottom, and an iris at the perpendicular junction of two rectangular waveguides. When wave incidents at one of the two separated rectangular waveguides, it, respectively, generates a left-hand circular polarized wave or a right-hand circular polarized wave in the circular waveguide. By adding a dumbbell-like metal plug driven with a high speed servomotor, a movable short circuit is formed along the circular waveguide to adjust the output RF phase of the rectangular port, realizing a high-speed high-power phase shifter. The C-band high power microwave (HPM) experiments were carried out, and the power capacity of the HPM polarizer and phase shifter was demonstrated to reach gigawatt level.

  15. Optical Demonstration of THz, Dual-Polarization Sensitive Microwave Kinetic Inductance Detectors

    NASA Astrophysics Data System (ADS)

    Dober, B.; Austermann, J. A.; Beall, J. A.; Becker, D.; Che, G.; Cho, H. M.; Devlin, M.; Duff, S. M.; Galitzki, N.; Gao, J.; Groppi, C.; Hilton, G. C.; Hubmayr, J.; Irwin, K. D.; McKenney, C. M.; Li, D.; Lourie, N.; Mauskopf, P.; Vissers, M. R.; Wang, Y.

    2015-12-01

    Polarization sensitive, microwave kinetic inductance detectors (MKIDs) are under development for the next generation BLAST instrument (BLAST-TNG). BLAST-TNG is a balloon-borne submillimeter polarimeter designed to study magnetic fields in diffuse dust regions and molecular clouds. We present the design and performance of feedhorn-coupled, dual-polarization sensitive MKIDs fabricated from TiN/Ti multilayer films, which have been optimized for the 250 \\upmu m band. Measurements show effective selection of linear polarization and good electrical isolation between the orthogonally crossed X and Y detectors within a single spatial pixel. The detector cross-polar coupling is < 3 %. Passband measurements are presented, which demonstrate that the desired band-edges (1.0-1.4 THz) have been achieved. We find a near linear response to the optical load from a blackbody source, which has been observed in previous devices fabricated from TiN. Blackbody-coupled noise measurements demonstrate that the sensitivity of the detectors is limited by photon noise when the optical load is greater than 1 pW.

  16. A Polarized Delta-Four-Stream Approximation for Infrared and Microwave Radiative Transfer: Part I.

    NASA Astrophysics Data System (ADS)

    Liou, K. N.; Ou, S. C.; Takano, Y.; Liu, Q.

    2005-07-01

    The delta-four-stream polarized (vector) thermal radiative transfer has been formulated and numerically tested specifically for application to satellite data assimilation in cloudy atmospheres. It is shown that for thermal emission in the earth's atmosphere, the [I, Q] component of the Stokes vector can be decoupled from the [U, V] component and that the solution of the vector equation set involving the four-stream approximation can be expressed in an analytic form similar to the scalar case. Thus, the computer time requirement can be optimized for the simulation of forward radiances and their derivatives. Computations have been carried out to illustrate the accuracy and efficiency of this method by comparing radiance and polarization results to those computed from the exact doubling method for radiative transfer for a number of thermal infrared and microwave frequencies. Excellent agreement within 1% is shown for the radiance results for all satellite viewing angles and cloud optical depths. For polarization, differences between the two are less than 5% if brightness temperature is used in the analysis. On balance of the computational speed and accuracy, the four-stream approximation for radiative transfer appears to be an attractive means for the simulation of cloudy radiances and polarization for research and data assimilation purposes.

  17. Detection of polarization in the cosmic microwave background using DASI. Degree Angular Scale Interferometer.

    PubMed

    Kovac, J M; Leitch, E M; Pryke, C; Carlstrom, J E; Halverson, N W; Holzapfel, W L

    The past several years have seen the emergence of a standard cosmological model, in which small temperature differences in the cosmic microwave background (CMB) radiation on angular scales of the order of a degree are understood to arise from acoustic oscillations in the hot plasma of the early Universe, arising from primordial density fluctuations. Within the context of this model, recent measurements of the temperature fluctuations have led to profound conclusions about the origin, evolution and composition of the Universe. Using the measured temperature fluctuations, the theoretical framework predicts the level of polarization of the CMB with essentially no free parameters. Therefore, a measurement of the polarization is a critical test of the theory and thus of the validity of the cosmological parameters derived from the CMB measurements. Here we report the detection of polarization of the CMB with the Degree Angular Scale Interferometer (DASI). The polarization is deteced with high confidence, and its level and spatial distribution are in excellent agreement with the predictions of the standard theory. PMID:12490941

  18. Cosmic ray contributions to the WMAP polarization data on the cosmic microwave background

    NASA Astrophysics Data System (ADS)

    Wibig, Tadeusz; Wolfendale, Arnold W.

    2016-01-01

    We have updated our analysis of the 9-year WMAP data using the collection of polarization maps looking for the presence of additional evidence for a finite ‘cosmic ray (CR) foreground’ for the cosmic microwave background (CMB). We have given special attention to high Galactic latitudes, where the recent BICEP2 findings were reported although very recent Planck data claims that dust is prevalent, thus nullifying the BICEP2 results. The method of examining the correlation with the observed gamma ray flux proposed in our earlier papers and applied to the polarization data shows that the foreground related to CRs is still observed even at high Galactic latitudes and conclusions about gravitational waves are not yet secure. Theory has it that there is important information about inflationary gravitational waves in the fine structure of the CMB polarization properties (polarization vector and angle) and it is necessary to examine further the conclusions that can be gained from studies of the CMB maps, in view of the disturbing foreground effects.

  19. A measurement of the cosmic microwave background polarization with the south pole telescope

    NASA Astrophysics Data System (ADS)

    Crites, Abigail Tinney

    We present maps of the cosmic microwave background (CMB) polarization at 90 and 150 GHz measured with SPTpol and the first EE and TE CMB power spectrum measurements from SPTpol. We also describe the SPTpol instrument in detail. We discuss the development of the SPTpol camera including the cryogenic design and the transition edge sensor (TES) detectors developed at NIST and Argonne National Laboratory. The goals of the SPTpol project are to exploit the high resolution of the telescope (1 arcminute beam) and the high sensitivity afforded by the 1536 detector camera to measure the E-mode power spectrum of the CMB, characterize the B-mode polarization induced by the gravitational lensing of the primordial E-mode CMB polarization, and to detector set an upper limit on the level of the B-mode polarization from inflationary gravitational waves. This thesis is a first step toward accomplishing these goals. Measuring the E-mode power spectrum will allow us to improve constraints on parameters of the current cosmological models that are sensitive to the damping tail of the CMB.

  20. Design and Deployment of the Polarbear Cosmic Microwave Background Polarization Experiment

    NASA Astrophysics Data System (ADS)

    Arnold, Kam Stahly

    2010-12-01

    POLARBEAR is a Cosmic Microwave Background (CMB) polarization experiment that will measure the CMB polarization angular power spectrum with unprecedented precision, searching for evidence of inflationary gravitational waves and the gravitational lensing of the CMB polarization by large scale structure. This dissertation presents an overview of the design of the instrument, focusing on the design and fabrication of the focal plane, and presents the results of some tests of instrument performance, both in the laboratory and from the initial engineering deployment. The structure of this thesis is as follows: Chapter 1 introduces the theoretical constructs used to describe the CMB polarization anisotropies, and the state of measurements in the field. Chapter 2 gives an overview of the choices made in the instrument design. Chapter 3 discusses the fundamental limits to the sensitivity of bolometric detectors, and chapter 4 explains the design choices involved in populating the focal plane with detectors. Chapter 5 describes the details of the detector architecture and fabrication, and chapter 6 the details of selecting the spectral band of the detectors. Finally, chapter 7 goes through some results obtained before and during the POLARBEAR engineering run in 2010, and comments on the work to be done before the Chilean deployment.

  1. Sea Surface Temperature and Vegetation Index

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is a composite MODIS image showing the 'green wave' of spring in North America and sea surface temperature in the ocean, collected over an 8-day period during the first week in April 2000. On land, the darker green pixels show where the most green foliage is being produced due to photosynthetic activity. Yellows on land show where there is little or no productivity and red is a boundary zone. In the ocean, orange and yellows show warmer waters and blues show colder values.

  2. A global monthly sea surface temperature climatology

    SciTech Connect

    Shea, D.J.; Trenberth, K.E.; Reynolds, R.W. NOAA, Climate Analysis Center, Washington, DC )

    1992-09-01

    The paper presents a new global 2 deg x 2 deg monthly sea surface temperature (SST) climatology, referred here to as the Shea-Trenberth-Reynolds (STR) climatology, which was derived by modifying a 1950-1979-based SST climatology from the Climate Analysis Center (CAC), by using data from the Comprehensive Ocean-Atmosphere Data Set to improve the SST estimates in the regions of the Kuroshio and the Gulf Stream. A comparison of the STR climatology with the Alexander and Mobley SST climatology showed that the STR climatology is warmer in the Northern Hemisphere, and colder poleward of 45 deg S. 22 refs.

  3. Degree-scale cosmic microwave background polarization measurements from three years of BICEP1 data

    SciTech Connect

    Barkats, D.; Aikin, R.; Bock, J. J.; Filippini, J.; Hristov, V. V.; Bischoff, C.; Buder, I.; Kovac, J. M.; Kaufman, J. P.; Keating, B. G.; Bierman, E. M.; Su, M.; Ade, P. A. R.; Battle, J. O.; Dowell, C. D.; Chiang, H. C.; Duband, L.; Hivon, E. F.; Holzapfel, W. L.; Jones, W. C.; and others

    2014-03-10

    BICEP1 is a millimeter-wavelength telescope designed specifically to measure the inflationary B-mode polarization of the cosmic microwave background at degree angular scales. We present results from an analysis of the data acquired during three seasons of observations at the South Pole (2006-2008). This work extends the two-year result published in Chiang et al., with additional data from the third season and relaxed detector-selection criteria. This analysis also introduces a more comprehensive estimation of band power window functions, improved likelihood estimation methods, and a new technique for deprojecting monopole temperature-to-polarization leakage that reduces this class of systematic uncertainty to a negligible level. We present maps of temperature, E- and B-mode polarization, and their associated angular power spectra. The improvement in the map noise level and polarization spectra error bars are consistent with the 52% increase in integration time relative to Chiang et al. We confirm both self-consistency of the polarization data and consistency with the two-year results. We measure the angular power spectra at 21 ≤ ℓ ≤ 335 and find that the EE spectrum is consistent with Lambda cold dark matter cosmology, with the first acoustic peak of the EE spectrum now detected at 15σ. The BB spectrum remains consistent with zero. From B-modes only, we constrain the tensor-to-scalar ratio to r=0.03{sub −0.23}{sup +0.27}, or r < 0.70 at 95% confidence level.

  4. SYSTEMATIC EFFECTS IN INTERFEROMETRIC OBSERVATIONS OF THE COSMIC MICROWAVE BACKGROUND POLARIZATION

    SciTech Connect

    Karakci, Ata; Korotkov, Andrei; Tucker, Gregory S.; Zhang Le; Timbie, Peter; Sutter, P. M.; Wandelt, Benjamin D.; Bunn, Emory F.

    2013-07-15

    The detection of the primordial B-mode spectrum of the polarized cosmic microwave background (CMB) signal may provide a probe of inflation. However, observation of such a faint signal requires excellent control of systematic errors. Interferometry proves to be a promising approach for overcoming such a challenge. In this paper we present a complete simulation pipeline of interferometric observations of CMB polarization, including systematic errors. We employ two different methods for obtaining the power spectra from mock data produced by simulated observations: the maximum likelihood method and the method of Gibbs sampling. We show that the results from both methods are consistent with each other as well as, within a factor of six, with analytical estimates. Several categories of systematic errors are considered: instrumental errors, consisting of antenna gain and antenna coupling errors; and beam errors, consisting of antenna pointing errors, beam cross-polarization, and beam shape (and size) errors. In order to recover the tensor-to-scalar ratio, r, within a 10% tolerance level, which ensures the experiment is sensitive enough to detect the B-signal at r = 0.01 in the multipole range 28 < l < 384, we find that, for a QUBIC-like experiment, Gaussian-distributed systematic errors must be controlled with precisions of |g{sub rms}| = 0.1 for antenna gain, |{epsilon}{sub rms}| = 5 Multiplication-Sign 10{sup -4} for antenna coupling, {delta}{sub rms} Almost-Equal-To 0. Degree-Sign 7 for pointing, {zeta}{sub rms} Almost-Equal-To 0. Degree-Sign 7 for beam shape, and {mu}{sub rms} = 5 Multiplication-Sign 10{sup -4} for beam cross-polarization. Although the combined systematic effects produce a tolerance level on r twice as large for an experiment with linear polarizers, the resulting bias in r for a circular experiment is 15% which is still on the level of desirable sensitivity.

  5. COSMIC MICROWAVE BACKGROUND INDUCED POLARIZATION FROM SINGLE SCATTERING BY CLUSTERS OF GALAXIES AND FILAMENTS

    SciTech Connect

    Ramos, Elsa P. R. G.; Da Silva, Antonio J. C.; Liu, Guo-Chin

    2012-09-20

    We present light-cone-integrated simulations of the cosmic microwave background (CMB) polarization signal induced by a single scattering in the direction of clusters of galaxies and filaments. We characterize the statistical properties of the induced polarization signals from the presence of the CMB quadrupole component (pqiCMB) and as the result of the transverse motion of ionized gas clouds with respect to the CMB rest frame (p{beta}{sup 2}{sub t}SZ). From adiabatic N-body/hydrodynamic simulations, we generated 28 random sky patches integrated along the light cone, each with about 0.86 deg{sup 2} and angular resolution of 6''. Our simulation method involves a box-stacking scheme that allows to reconstruct the CMB quadrupole component and the gas physical properties along the line of sight. We find that the linear polarization degree in the logarithmic scale of both effects follows approximately a Gaussian distribution and the mean total signal is about 10{sup -8} and 10{sup -10} for the pqiCMB and p{beta}{sup 2}{sub t}SZ effects, respectively. The polarization angle is consistent with a flat distribution in both cases. From the mean distributions of the polarization degree with redshift, the highest peak is found at z {approx_equal} 1 for the induced CMB quadrupole and at z {approx_equal} 0.5 for the kinematic component. Our results suggest that most of the contribution for the total polarization signal arises from z {approx}< 4 for the pqiCMB and z {approx}< 3 for p{beta}{sup 2}{sub t}SZ. The spectral dependency of both integrated signals is strong, increasing with the frequency, especially in the case of the p{beta}{sup 2}{sub t}SZ signal, which increases by a factor of 100 from 30 GHz to 675 GHz. The maxima values found at the highest frequency are about 3 {mu}K and 13 {mu}K for the pqiCMB and p{beta}{sup 2}{sub t}SZ, respectively. The angular power spectra of these effects peak at large multipoles l > 10{sup 4}, being of the order of 10{sup -5} {mu}K{sup 2

  6. What can be learned from the lensed cosmic microwave background B-mode polarization power spectrum?

    SciTech Connect

    Smith, Sarah; Challinor, Anthony; Rocha, Graca

    2006-01-15

    The effect of weak gravitational lensing on the cosmic microwave background (CMB) temperature anisotropies and polarization will provide access to cosmological information that cannot be obtained from the primary anisotropies alone. We compare the information content of the lensed B-mode polarization power spectrum, properly accounting for the non-Gaussian correlations between the power on different scales, with that of the unlensed CMB fields and the lensing potential. The latter represent the products of an (idealized) optimal analysis that exploits the lens-induced non-Gaussianity to reconstruct the fields. Compressing the non-Gaussian lensed CMB into power spectra is wasteful and leaves a tight degeneracy between the equation of state of dark energy and neutrino mass that is much stronger than in the more optimal analysis. Despite this, a power-spectrum analysis will be a useful first step in analyzing future B-mode polarization data. For this reason, we also consider how to extract accurate parameter constraints from the lensed B-mode power spectrum. We show with simulations that for cosmic-variance-limited measurements of the lensed B-mode power, including the non-Gaussian correlations in existing likelihood approximations gives biased parameter results. We develop a more refined likelihood approximation that performs significantly better. This new approximation should also be of more general interest in the wider context of parameter estimation from Gaussian CMB data.

  7. Modern average global sea-surface temperature

    USGS Publications Warehouse

    Schweitzer, Peter N.

    1993-01-01

    The data contained in this data set are derived from the NOAA Advanced Very High Resolution Radiometer Multichannel Sea Surface Temperature data (AVHRR MCSST), which are obtainable from the Distributed Active Archive Center at the Jet Propulsion Laboratory (JPL) in Pasadena, Calif. The JPL tapes contain weekly images of SST from October 1981 through December 1990 in nine regions of the world ocean: North Atlantic, Eastern North Atlantic, South Atlantic, Agulhas, Indian, Southeast Pacific, Southwest Pacific, Northeast Pacific, and Northwest Pacific. This data set represents the results of calculations carried out on the NOAA data and also contains the source code of the programs that made the calculations. The objective was to derive the average sea-surface temperature of each month and week throughout the whole 10-year series, meaning, for example, that data from January of each year would be averaged together. The result is 12 monthly and 52 weekly images for each of the oceanic regions. Averaging the images in this way tends to reduce the number of grid cells that lack valid data and to suppress interannual variability.

  8. L-Band H Polarized Microwave Emission During the Corn Growth Cycle

    NASA Technical Reports Server (NTRS)

    Joseph, A. T.; va der Velde, R.; O'Neill, P. E.; Kim, E.; Lang, R. H.; Gish, T.

    2012-01-01

    Hourly L-band (1.4 GHz) horizontally (H) polarized brightness temperatures (T(sub B))'s measured during five episodes (more than two days of continuous measurements) of the 2002 corn growth cycle are analyzed. These T(sub B)'s measurements were acquired as a part of a combined active/passive microwave field campaign, and were obtained at five incidence and three azimuth angles relative to the row direction. In support of this microwave data collection, intensive ground sampling took place once a week. Moreover, the interpretation of the hourly T(sub B)'s could also rely on the data obtained using the various automated instruments installed in the same field. In this paper, the soil moisture and temperature measured at fixed time intervals have been employed as input for the tau-omega model to reproduce the hourly T(sub B). Through the calibration of the vegetation and surface roughness parameterizations, the impact of the vegetation morphological changes on the microwave emission and the dependence of the soil surface roughness parameter, h(sub r), on soil moisture are investigated. This analysis demonstrates that the b parameter, appearing in the representation of the canopy opacity, has an angular dependence that varies throughout the growing period and also that the parameter hr increases as the soil dries in a portion of the dry-down cycle. The angular dependence of the b parameter imposes the largest uncertainty on T(sub B) simulations near senescence as the response of b to the incidence is also affected by the crop row orientation. On the other hand, the incorporation of a soil moisture dependent h(sub r) parameterization was responsible for the largest error reduction of T(sub B) simulations in the early growth cycle.

  9. Deciphering inflation with gravitational waves: Cosmic microwave background polarization vs direct detection with laser interferometers

    SciTech Connect

    Smith, Tristan L.; Peiris, Hiranya V.; Cooray, Asantha

    2006-06-15

    A detection of the primordial gravitational wave background is considered to be the 'smoking-gun' evidence for inflation. While superhorizon waves are probed with cosmic microwave background (CMB) polarization, the relic background will be studied with laser interferometers. The long lever arm spanned by the two techniques improves constraints on the inflationary potential and validation of consistency relations expected under inflation. If gravitational waves with a tensor-to-scalar amplitude ratio greater than 0.01 are detected by the CMB, then a direct-detection experiment with a sensitivity consistent with current concept studies should be pursued vigorously. If no primordial tensors are detected by the CMB, a direct-detection experiment to understand the simplest form of inflation must have a sensitivity improved by two to 3 orders of magnitude over current plans.

  10. Leveraging microwave polarization information for the calibration of a land data assimilation system

    NASA Astrophysics Data System (ADS)

    Holmes, Thomas R. H.; Crow, Wade T.; De Jeu, Richard A. M.

    2014-12-01

    This letter contributes a new approach to calibrating a tau-omega radiative transfer model coupled to land surface model output with low-frequency (<10 GHz) microwave brightness temperature (TB) observations. The problem of calibrating this system is generally poorly posed because various parameter combinations may yield indistinguishable (least squares error) results. This is theoretically important for a land data assimilation system since alternative parameter combinations have different impacts on the sensitivity of TB to soil moisture and misattribution of systematic error may therefore disrupt data assimilation system performance. Via synthetic experiments we demonstrate that using TB polarization difference to parameterize vegetation opacity can improve the stability of calibrated soil moisture/TB sensitivities relative to the more typical approach of utilizing ancillary information to estimate vegetation opacity. The proposed approach fully follows from the radiative transfer model, implemented according to commonly adopted assumptions, and reduces by one the number of calibration parameters.

  11. Synthesis of polymer-derived ceramic Si(B)CN-carbon nanotube composite by microwave-induced interfacial polarization.

    PubMed

    Bhandavat, R; Kuhn, W; Mansfield, E; Lehman, J; Singh, G

    2012-01-01

    We demonstrate synthesis of a polymer-derived ceramic (PDC)-multiwall carbon nanotube (MWCNT) composite using microwave irradiation at 2.45 GHz. The process takes about 10 min of microwave irradiation for the polymer-to-ceramic conversion. The successful conversion of polymer coated carbon nanotubes to ceramic composite is chemically ascertained by Fourier transform-infrared and X-ray photoelectron spectroscopy and physically by thermogravimetric analysis and transmission electron microscopy characterization. Frequency dependent dielectric measurements in the S-Band (300 MHz to 3 GHz) were studied to quantify the extent of microwave-CNT interaction and the degree of selective heating available at the MWCNT-polymer interface. Experimentally obtained return loss of the incident microwaves in the specimen explains the reason for heat generation. The temperature-dependent permittivity of polar molecules further strengthens the argument of internal heat generation. PMID:22141448

  12. Artificial neural network based microwave precipitation estimation using scattering index and polarization corrected temperature

    NASA Astrophysics Data System (ADS)

    Mahesh, C.; Prakash, Satya; Sathiyamoorthy, V.; Gairola, R. M.

    2011-11-01

    An Artificial Neural Network (ANN) based technique is proposed for estimating precipitation over Indian land and oceanic regions [30° S - 40° N and 30° E - 120° E] using Scattering Index (SI) and Polarization Corrected Temperature (PCT) derived from Special Sensor Microwave Imager (SSM/I) measurements. This rainfall retrieval algorithm is designed to estimate rainfall using a combination of SSM/I and Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) measurements. For training the ANN, SI and PCT (which signify rain signatures in a better way) calculated from SSM/I brightness temperature are considered as inputs and Precipitation Radar (PR) rain rate as output. SI is computed using 19.35 GHz, 22.235 GHz and 85.5 GHz Vertical channels and PCT is computed using 85.5 GHz Vertical and Horizontal channels. Once the training is completed, the independent data sets (which were not included in the training) were used to test the performance of the network. Instantaneous precipitation estimates with independent test data sets are validated with PR surface rain rate measurements. The results are compared with precipitation estimated using power law based (i) global algorithm and (ii) regional algorithm. Overall results show that ANN based present algorithm shows better agreement with PR rain rate. This study is aimed at developing a more accurate operational rainfall retrieval algorithm for Indo-French Megha-Tropiques Microwave Analysis and Detection of Rain and Atmospheric Structures (MADRAS) radiometer.

  13. The Aquarius Mission: Sea Surface Salinity from Space

    NASA Technical Reports Server (NTRS)

    Koblinsky, Chester; Chao, Y.; deCharon, A.; Edelstein, W.; Hildebrand, P.; Lagerloef, G.; LeVine, D.; Pellerano, F.; Rahmat-Samii, Y.; Ruf, C.

    2001-01-01

    Aquarius is a new satellite mission concept to study the impact of the global water cycle on the ocean, including the response of the ocean to buoyancy forcing and the subsequent feedback of the ocean on the climate. The measurement objective of Aquarius is sea surface salinity, which reflects the concentration of freshwater at the ocean surface. Salinity affects the dielectric constant of sea water and, consequently, the radiometric emission of the sea surface to space. Rudimentary space observations with an L-band radiometer were first made from Skylab in the mid-70s and numerous aircraft missions of increasing quality and improved technology have been conducted since then. Technology is now available to carry out a global mission, which includes both an accurate L band (1.413 Ghz) radiometer and radar system in space and a global array of in situ observations for calibration and validation, in order to address key NASA Earth Science Enterprise questions about the global cycling of water and the response of the ocean circulation to climate change. The key scientific objectives of Aquarius examine the cycling of water at the ocean's surface, the response of the ocean circulation to buoyancy forcing, and the impact of buoyancy forcing on the ocean's thermal feedback to the climate. Global surface salinity will also improve our ability to model the surface solubility chemistry needed to estimate the air-sea exchange of CO2. In order to meet these science objectives, the NASA Salinity Sea Ice Working Group over the past three years has concluded that the mission measurement goals should be better than 0.2 practical salinity units (psu) accuracy, 100 km resolution, and weekly to revisits. The Aquarius mission proposes to meet these measurement requirements through a real aperture dual-polarized L band radiometer and radar system. This system can achieve the less than 0.1 K radiometric temperature measurement accuracy that is required. A 3 m antenna at approx. 600km

  14. EBEX: A Balloon-Borne Telescope for Measuring Cosmic Microwave Background Polarization

    NASA Astrophysics Data System (ADS)

    Chapman, Daniel

    2015-05-01

    EBEX is a long-duration balloon-borne (LDB) telescope designed to probe polarization signals in the cosmic microwave background (CMB). It is designed to measure or place an upper limit on the inflationary B-mode signal, a signal predicted by inflationary theories to be imprinted on the CMB by gravitational waves, to detect the effects of gravitational lensing on the polarization of the CMB, and to characterize polarized Galactic foreground emission. The payload consists of a pointed gondola that houses the optics, polarimetry, detectors and detector readout systems, as well as the pointing sensors, control motors, telemetry sytems, and data acquisition and flight control computers. Polarimetry is achieved with a rotating half-wave plate and wire grid polarizer. The detectors are sensitive to frequency bands centered on 150, 250, and 410 GHz. EBEX was flown in 2009 from New Mexico as a full system test, and then flown again in December 2012 / January 2013 over Antarctica in a long-duration flight to collect scientific data. In the instrumentation part of this thesis we discuss the pointing sensors and attitude determination algorithms. We also describe the real-time map making software, "QuickLook", that was custom-designed for EBEX. We devote special attention to the design and construction of the primary pointing sensors, the star cameras, and their custom-designed flight software package, "STARS" (the Star Tracking Attitude Reconstruction Software). In the analysis part of this thesis we describe the current status of the post-flight analysis procedure. We discuss the data structures used in analysis and the pipeline stages related to attitude determination and map making. We also discuss a custom-designed software framework called "LEAP" (the LDB EBEX Analysis Pipeline) that supports most of the analysis pipeline stages.

  15. Satellite Sensed Skin Sea Surface Temperature

    NASA Technical Reports Server (NTRS)

    Donlon, Craig

    1997-01-01

    Quantitative predictions of spatial and temporal changes the global climate rely heavily on the use of computer models. Unfortunately, such models cannot provide the basis for climate prediction because key physical processes are inadequately treated. Consequently, fine tuning procedures are often used to optimize the fit between model output and observational data and the validation of climate models using observations is essential if model based predictions of climate change are to be treated with any degree of confidence. Satellite Sea Surface Temperature (SST) observations provide high spatial and temporal resolution data which is extremely well suited to the initialization, definition of boundary conditions and, validation of climate models. In the case of coupled ocean-atmosphere models, the SST (or more correctly the 'Skin' SST (SSST)) is a fundamental diagnostic variable to consider in the validation process. Daily global SST maps derived from satellite sensors also provide adequate data for the detection of global patterns of change which, unlike any other SST data set, repeatedly extend into the southern hemisphere extra-tropical regions. Such data are essential to the success of the spatial 'fingerprint' technique, which seeks to establish a north-south asymmetry where warming is suppressed in the high latitude Southern Ocean. Some estimates suggest that there is a greater than 80% chance of directly detecting significant change (97.5 % confidence level) after 10-12 years of consistent global observations of mean sea surface temperature. However, these latter statements should be qualified with the assumption that a negligible drift in the observing system exists and that biases between individual instruments required to derive a long term data set are small. Given that current estimates for the magnitude of global warming of 0.015 K yr(sup -1) - 0.025 K yr(sup -1), satellite SST data sets need to be both accurate and stable if such a warming trend is to

  16. Improved Sea Surface Salinity Retrievals using Ancillary data for Aquarius Ocean Roughness Correction

    NASA Astrophysics Data System (ADS)

    Jones, L.; Hejazin, Y.; Rabollii, M.

    2012-12-01

    The Aquarius/SAC-D sea surface salinity (SSS) measurement mission was launched into polar orbit during the summer of 2011. The prime sensor is a combined L-band radiometer/scatterometer developed jointly by NASA Goddard Space Flight Center and the Jet Propulsion Laboratory, which derives SSS from ocean surface brightness temperature (Tb) measurements. This paper deals with a method of improving AQ SSS by making a making an ocean roughness brightness temperature correction (ΔTbr). The ΔTbr is derived using several ancillary data sources of surface wind measurements, namely; NOAA numerical weather model - Global Data Assimilation System (GDAS), WindSat ocean vector wind, and the CONAE Microwave Radiometer (MWR). The basis of the correction is the excess (warming) brightness temperature that is produced when the ocean is roughened by the surface wind. We model the increase in L-band Tb as a function of wind speed and direction relative to the antenna azimuth look direction. Our radiative transfer model by El-Nimri [2010] has been tuned to actual AQ ocean surface Tb's with corresponding surface wind vector. Using this ocean emissivity model and the ancillary wind vector, we derive the roughness correction, ΔTbr, which is applied to the AQ measured ocean surface Tb before retrieving SSS. Finally the effect of ΔTbr is evaluated by computing the difference between the HYCOM ocean salinity model and the AQ retrievals. These differences are cross correlated with the ancillary surface wind vector to assess the effectiveness of the roughness correction. Finally, we compare our ΔTbr with the AQ scatterometer derived ΔTbr. We compare the similarities and differenced versus the ancillary surface wind speed. S. El-Nimri et al., 2010, "An improved C-band ocean surface emissivity model at hurricane force wind speeds over a wide range of earth incidence angles," IEEE Geosci. Rem. Sens. Letters, vol. 7, NO. 4, October.

  17. Sea surface wind stress in stratified atmospheric flow

    SciTech Connect

    Myrhaug, D.; Slaattelid, O.H.

    1996-12-31

    The paper presents the wind shear stress on the sea surface as well as the velocity profile in stably stratified atmospheric boundary layer flow over wind waves by using similarity theory. For a given geostrophic velocity, Coriolis parameter, spectral peak period and stratification parameter the sea surface shear stress is determined. Further, the direction of the sea surface shear stress and the velocity profile are given. Parameterizations of the results are also presented. Finally, the engineering relevance of the results is discussed.

  18. Passive L-Band H Polarized Microwave Emission During the Corn Growth Cycle

    NASA Astrophysics Data System (ADS)

    Joseph, A. T.; van der Velde, R.; O'Neill, P. E.; Kim, E. J.; Lang, R. H.; Gish, T. J.

    2012-12-01

    Hourly L-band (1.4 GHz) horizontally (H) polarized brightness temperatures (TB's) measured during five episodes (more than two days of continuous measurements) of the 2002 corn growth cycle are analyzed. These TB measurements were acquired as a part of a combined active/passive microwave field campaign, and were obtained at five incidence and three azimuth angles relative to the row direction. In support of this microwave data collection, intensive ground sampling took place once a week. Moreover, the interpretation of the hourly TB's could also rely on the data obtained using the various automated instruments installed in the same field. In this paper, the soil moisture and temperature measured at fixed time intervals have been employed as input for the tau-omega model to reproduce the hourly TB. Through the calibration of the vegetation and surface roughness parameterizations, the impact of the vegetation morphological changes on the microwave emission and the dependence of the soil surface roughness parameter, hr, on soil moisture are investigated. This analysis demonstrates that the b parameter, appearing in the representation of the canopy opacity, has an angular dependence that varies throughout the growing period and also that the parameter hr increases as the soil dries in a portion of the dry-down cycle. The angular dependence of the b parameter imposes the largest uncertainty on TB simulations near senescence as the response of b to the incidence is also affected by the crop row orientation. On the other hand, the incorporation of a soil moisture dependent hr parameterization was responsible for the largest error reduction of TB simulations in the early growth cycle. A.T. Joseph, R. Van der Velde, P.E. O'Neill, R.H. Lang, and T. Gish, "Soil moisture retrieval during a corn growth cycle using L-band (1.6 GHz) radar observations", IEEE Transactions on Geoscience and Remote Sensing, vol. 46, DOI:10.1109/TGRS.2008.917214, Aug. 2008. M.C. Dobson, F.T. Ulaby, M

  19. The POLARBEAR Cosmic Microwave Background Polarization Experiment and Anti-Reflection Coatings for Millimeter Wave Observations

    NASA Astrophysics Data System (ADS)

    Quealy, Erin Elizabeth

    New technology has rapidly advanced the field of observational cosmology over the last 30 years. This trend will continue with the development of technologies to measure the Cosmic Microwave Background (CMB) polarization. The B-mode component of the polarization map will place limits on the energy scale of inflation and the sum of the neutrino masses. This thesis describes the pb instrument which will measure the CMB polarization anisotropy to unprecedented sensitivity. POLARBEAR-I is currently observing, and an upgraded version, POLARBEAR-II, is planned for the future. The first version of the experiment, POLARBEAR-I, is fielding several new technologies for the first time. POLARBEAR-I has high sensitivity due to its detector count. It employs a 1274 detector Transition-Edge Sensor (TES) bolometer array. The bolometers are coupled to a planar array of polarization sensitive antennas. These antennas are lithographed on the same substrate as the TES detectors, allowing on-chip band defining filters between the antenna and detector. The focal plane is composed of seven hexagonal detector modules. This modular scheme can be extended to create larger focal plane arrays in the future. POLARBEAR-I is observing at a single band near 150 GHz, the peak in the CMB blackbody curve. The lenslet antenna coupled detector technology, fielding for the first time in POLARBEAR-I, is naturally scalable to larger arrays with multi-chroic pixels. This broadband technology will have higher sensitivity and better capability for astronomical foreground contaminant removal. The antenna geometry can be changed to receive a wider frequency bandwidth. This bandwidth can be broken into multiple frequency bands with the on-chip band defining filters. Each band will be read out by one TES detector. A dual band instrument, pbtwo, is in development with bands at 90 and 150 GHz. One challenge for all CMB polarization measurements is minimization of systematic errors. One source of error is

  20. A TSVD Analysis of the Impact of Polarization on Microwave Breast Imaging using an Enclosed Array of Miniaturized Patch Antennas

    PubMed Central

    Mays, R. Owen; Behdad, Nader; Hagness, Susan C.

    2014-01-01

    Microwave breast imaging performance is fundamentally dependent on the quality of information contained within the scattering data. We apply a truncated singular-value decomposition (TSVD) method to evaluate the information contained in a simulated scattering scenario wherein a compact, shielded array of miniaturized patch antennas surrounds an anatomically realistic numerical breast phantom. In particular, we investigate the impact of different antenna orientations (and thus polarizations), namely two array configurations with uniform antenna orientations and one mixed-orientation array configuration. The latter case is of interest because it may offer greater flexibility in antenna and array design. The results of this analysis indicate that mixed-polarization configurations do not degrade information quality compared to uniform-polarization configurations and in fact may enhance imaging performance, and thus represent viable design options for microwave breast imaging systems. PMID:25705136

  1. Satellite monitoring of sea surface pollution

    NASA Technical Reports Server (NTRS)

    Fielder, G.; Telfer, D. J. (Principal Investigator)

    1979-01-01

    The author has identified the following significant results. Image processing techniques developed are well adapted to the exploration and isolation of local areas which exhibit small temperature differences between themselves and their surroundings. In the worst case of imagery of small areal extent of sea surface having no coastal boundary in the area, there is yet no method of distinguishing unambiguously an oil spill from fog, cloud, the effect produced by shallow sediments, or the effects of naturally occuring thermal fronts. In the case of uniform slicks of liquid North Sea oil in still air, laboratory simulation experiments show that, for oil thicknesses in excess of 1 or 2 mm, there is, under equilibrium conditions, little dependence of oil surface temperature on the thickness of the oil layer. The surface temperature of oil is consistently higher than that of water, the difference being about 1 K at low values of relative humidity, but tending to increase as the relative humidity increases.

  2. Middle Pliocene sea surface temperature variability

    USGS Publications Warehouse

    Dowsett, H.J.; Chandler, M.A.; Cronin, T. M.; Dwyer, G.S.

    2005-01-01

    Estimates of sea surface temperature (SST) based upon foraminifer, diatom, and ostracod assemblages from ocean cores reveal a warm phase of the Pliocene between about 3.3 and 3.0 Ma. Pollen records and plant megafossils, although not as well dated, show evidence for a warmer climate at about the same time. Increased greenhouse forcing and altered ocean heat transport are the leading candidates for the underlying cause of Pliocene global warmth. Despite being a period of global warmth, this interval encompasses considerable variability. Two new SST reconstructions are presented that are designed to provide a climatological error bar for warm peak phases of the Pliocene and to document the spatial distribution and magnitude of SST variability within the mid-Pliocene warm period. These data suggest long-term stability of low-latitude SST and document greater variability in regions of maximum warming. Copyright 2005 by the American Geophysical Union.

  3. Sea surface temperatures from VAS MSI data

    NASA Technical Reports Server (NTRS)

    Bates, J. J.

    1984-01-01

    A procedure is developed for estimating sea surface temperatures from multispectral image data acquired from the VISSR atmospheric sounder on the geostationary GOES satellites. Theoretical regression equations for two and three infrared window channels are empirically tuned using clear field of view satellite radiances matched with reports of SST from NOAA fixed environmental buoys. The empirical regression equations are then used to produce daily regional analyses of SST. Monthly mean SST's for the western North Atlantic and the eastern equatorial Pacific during March and July 1982 were produced for use in the SST Intercomparison Workshop Series. Workshop results showed VAS SST's have a scatter of 0.8-1.0 C and a slight warm bias with respect to the other measurements of SST. The VAS SST's show no discernible bias in the region of El Chichon volcanic aerosol cloud.

  4. Sea surface temperature - Observations from geostationary satellites

    NASA Technical Reports Server (NTRS)

    Bates, J. J.; Smith, W. L.

    1985-01-01

    Multispectral image data acquired from the VISSR atmospheric sounder (VAS) on the geostationary GOES satellites were used to estimate sea surface temperatures (SST). A procedure was developed to screen VAS visible and infrared data for cloud-free regions for estimation of SST from the clear infrared radiances. A data set of matches between the VAS radiances and high quality buoy estimates of SST was produced. A linear regression analysis of these matches was performed to generate an empirical algorithm relating the VAS window channel brightness temperatures to the estimates of SST recorded by NOAA fixed environment buoys. Daily maps of SST during Hurricanes Alicia (1983) and Debbie (1982) demonstrated the ability of VAS to monitor air-sea interactions at high temporal and spatial scales.

  5. Sea surface temperature variability: patterns and mechanisms.

    PubMed

    Deser, Clara; Alexander, Michael A; Xie, Shang-Ping; Phillips, Adam S

    2010-01-01

    Patterns of sea surface temperature (SST) variability on interannual and longer timescales result from a combination of atmospheric and oceanic processes. These SST anomaly patterns may be due to intrinsic modes of atmospheric circulation variability that imprint themselves upon the SST field mainly via surface energy fluxes. Examples include SST fluctuations in the Southern Ocean associated with the Southern Annular Mode, a tripolar pattern of SST anomalies in the North Atlantic associated with the North Atlantic Oscillation, and a pan-Pacific mode known as the Pacific Decadal Oscillation (with additional contributions from oceanic processes). They may also result from coupled ocean-atmosphere interactions, such as the El Niño-Southern Oscillation phenomenon in the tropical Indo-Pacific, the tropical Atlantic Niño, and the cross-equatorial meridional modes in the tropical Pacific and Atlantic. Finally, patterns of SST variability may arise from intrinsic oceanic modes, notably the Atlantic Multidecadal Oscillation. PMID:21141660

  6. Probing 'Parent Universe' in Loop Quantum Cosmology with B-mode Polarization in Cosmic Microwave Background

    NASA Astrophysics Data System (ADS)

    Lucky Chang, Wen-Hsuan; Proty Wu, Jiun-Huei

    2016-06-01

    We aim to use the observations of B-mode polarization in the Cosmic Microwave Background (CMB) to probe the ‘parent universe’ under the context of Loop Quantum Cosmology (LQC). In particular, we investigate the possibility for the gravitational waves (GW) such as those from the stellar binary systems in the parent universe to survive the big bounce and thus to be still observable today. Our study is based on the background dynamics with the zeroth-order holonomy correction using the Arnowitt-Deser-Misner (ADM) formalism. We propose a new framework in which transfer functions are invoked to bring the GWs in the parent universe through the big bounce, inflation, and big bang to reach today. This transparent and intuitive formalism allows us to accurately discuss the influence of the GWs from the parent universe on the B-mode polarization in the CMB today under backgrounds of different LQC parameters. These features can soon be tested by the forth-coming CMB observations and we note that the LQC backgrounds with symmetric bouncing scenarios are ruled out by the latest observational results from Planck and BICEP2/Keck experiments.

  7. The millimeter-wave bolometric interferometer (MBI) for observing the cosmic microwave background polarization

    NASA Astrophysics Data System (ADS)

    Kim, Jaiseung

    This thesis describes the Millimeter-wave Bolometric Interferometer (MBI) to measure the Cosmic Microwave Background Polarization (CMBP) anisotropy at angular scales 0.5°--1° and a center frequency of 90 GHz. The measurement of the CMBP anisotropy on these angular scales will put more stringent constraints on cosmological models and parameters. The prototype instrument employs four corrugated feedhorns and cooled bolometers. Using a Butler beam combiner, beams from four feedhorns are correlated, yielding interferometric measurements of the CMBP. From these interferometric measurements, we can reconstruct the image of polarization by aperture synthesis and estimate the power spectrum of the CMBP by maximum likelihood method. We describe aperture synthesis and maximum likelihood method. We present the result of the image reconstruction and the power spectrum estimation from simulated MBI observations. With the planned sensitivity of the MBI, the MBI will be able to estimate the E mode power spectra of the CMBP in the multipole range (150 <= l <= 300) and put upper bounds on the B mode power spectra in the relevant multipoles. In the end, we describe all-sky imaging method from interferometric measurements developed for the Einstein Probe Interferometer for Cosmology (EPIC), which is the satellite version of the MBI.

  8. Determination of the Structure of the Coronal Magnetic Field Using Microwave Polarization Measurements

    NASA Astrophysics Data System (ADS)

    Bogod, V. M.; Yasnov, L. V.

    2016-07-01

    An analysis of the oscillatory motions and wave processes in active regions requires knowledge of the structure of the magnetic fields in the chromosphere and corona. We study the magnetic field structure of active regions at coronal heights, as they are determined by means of multiwave observations of polarized radio emission of active regions in the microwave range. Two methods, a stereoscopic method and the analysis of the radio spectrum are used. The method of stereoscopy rotation allows estimating the height of radio sources in a stable active region relative to the photosphere, based on its apparent motion in the image plane recorded over several days of observation. At various times one-dimensional scans at multiple frequencies spanning the 5.98 - 15.95 GHz frequency range from the RATAN-600 instrument are used. The gyroresonance emission mechanism, which is sensitive to the coronal magnetic field strength, is applied to convert the radio source estimated heights at various frequencies, h(f), to information as regards magnetic field vs. height, B(h). Diagrams of longitude - height of some polarized radio sources revealed multiple reversals, suggestive of a spiral magnetic structure. In all cases, the magnetic field strength maintains high values (800 - 1000 G) at the highest altitudes analysed, which reflects a relatively weak divergence in the field of magnetic flux tubes (in the height range 8 - 14 Mm) responsible for the main part of the radio emission of active regions.

  9. B polarization of the cosmic microwave background as a tracer of strings

    SciTech Connect

    Seljak, Uros; Slosar, Anze

    2006-09-15

    String models can produce successful inflationary scenarios in the context of brane collisions, and in many of these models cosmic strings may also be produced. In scenarios such as Kachru-Kallosh-Linde-Maldacena-McAllister-Trivedi (KKLMMT) scenario the string contribution is naturally predicted to be well below the inflationary signal for cosmic microwave background (CMB) temperature anisotropies, in agreement with the existing limits. We find that for B type polarization of CMB the situation is reversed and the dominant signal comes from vector modes generated by cosmic strings, which exceeds the gravity wave signal from both inflation and strings. The signal can be detected for a broad range of parameter space; future polarization experiments may be able to detect the string signal down to the string tension G{mu}=10{sup -9}, although foregrounds and lensing are likely to worsen these limits. We argue that the optimal scale to search for the string signature is at l{approx}1000, but in models with high optical depth the signal from reionization peak at large scales is also significant. The shape of the power spectrum allows one to distinguish the string signature from the gravity waves from inflation, but only with a sufficiently high angular resolution experiment.

  10. Dynamic nuclear polarization at 9T using a novel 250GHz gyrotron microwave source.

    PubMed

    Bajaj, V S; Farrar, C T; Hornstein, M K; Mastovsky, I; Vieregg, J; Bryant, J; Eléna, B; Kreischer, K E; Temkin, R J; Griffin, R G

    2003-02-01

    In this communication, we report enhancements of nuclear spin polarization by dynamic nuclear polarization (DNP) in static and spinning solids at a magnetic field strength of 9T (250 GHz for g=2 electrons, 380 MHz for 1H). In these experiments, 1H enhancements of up to 170+/-50 have been observed in 1-13C-glycine dispersed in a 60:40 glycerol/water matrix at temperatures of 20K; in addition, we have observed significant enhancements in 15N spectra of unoriented pf1-bacteriophage. Finally, enhancements of approximately 17 have been obtained in two-dimensional 13C-13C chemical shift correlation spectra of the amino acid U-13C, 15N-proline during magic angle spinning (MAS), demonstrating the stability of the DNP experiment for sustained acquisition and for quantitative experiments incorporating dipolar recoupling. In all cases, we have exploited the thermal mixing DNP mechanism with the nitroxide radical 4-amino-TEMPO as the paramagnetic dopant. These are the highest frequency DNP experiments performed to date and indicate that significant signal enhancements can be realized using the thermal mixing mechanism even at elevated magnetic fields. In large measure, this is due to the high microwave power output of the 250 GHz gyrotron oscillator used in these experiments. PMID:12615147

  11. Dynamic nuclear polarization at 9T using a novel 250GHz gyrotron microwave source

    PubMed Central

    Bajaj, V.S.; Farrar, C.T.; Hornstein, M.K.; Mastovsky, I.; Vieregg, J.; Bryant, J.; Eléna, B.; Kreischer, K.E.; Temkin, R.J.; Griffin, R.G.

    2010-01-01

    In this communication, we report enhancements of nuclear spin polarization by dynamic nuclear polarization (DNP) in static and spinning solids at a magnetic field strength of 9T (250 GHz for g = 2 electrons, 380 MHz for 1H). In these experiments, 1H enhancements of up to 170 ± 50 have been observed in 1-13C-glycine dispersed in a 60:40 glycerol/water matrix at temperatures of 20 K; in addition, we have observed significant enhancements in 15N spectra of unoriented pf1-bacteriophage. Finally, enhancements of ~17 have been obtained in two-dimensional 13C–13C chemical shift correlation spectra of the amino acid U-13C, 15N-proline during magic angle spinning (MAS), demonstrating the stability of the DNP experiment for sustained acquisition and for quantitative experiments incorporating dipolar recoupling. In all cases, we have exploited the thermal mixing DNP mechanism with the nitroxide radical 4-amino-TEMPO as the paramagnetic dopant. These are the highest frequency DNP experiments performed to date and indicate that significant signal enhancements can be realized using the thermal mixing mechanism even at elevated magnetic fields. In large measure, this is due to the high microwave power output of the 250 GHz gyrotron oscillator used in these experiments. PMID:12615147

  12. Determination of the Structure of the Coronal Magnetic Field Using Microwave Polarization Measurements

    NASA Astrophysics Data System (ADS)

    Bogod, V. M.; Yasnov, L. V.

    2016-06-01

    An analysis of the oscillatory motions and wave processes in active regions requires knowledge of the structure of the magnetic fields in the chromosphere and corona. We study the magnetic field structure of active regions at coronal heights, as they are determined by means of multiwave observations of polarized radio emission of active regions in the microwave range. Two methods, a stereoscopic method and the analysis of the radio spectrum are used. The method of stereoscopy rotation allows estimating the height of radio sources in a stable active region relative to the photosphere, based on its apparent motion in the image plane recorded over several days of observation. At various times one-dimensional scans at multiple frequencies spanning the 5.98 - 15.95 GHz frequency range from the RATAN-600 instrument are used. The gyroresonance emission mechanism, which is sensitive to the coronal magnetic field strength, is applied to convert the radio source estimated heights at various frequencies, h(f), to information as regards magnetic field vs. height, B(h). Diagrams of longitude - height of some polarized radio sources revealed multiple reversals, suggestive of a spiral magnetic structure. In all cases, the magnetic field strength maintains high values (800 - 1000 G) at the highest altitudes analysed, which reflects a relatively weak divergence in the field of magnetic flux tubes (in the height range 8 - 14 Mm) responsible for the main part of the radio emission of active regions.

  13. POLARBEAR2: A new multichroic receiver for precision measurements of cosmic microwave background polarization

    NASA Astrophysics Data System (ADS)

    Barron, Darcy; POLARBEAR Collaboration

    2014-01-01

    POLARBEAR-2 is a new receiver that will be installed in 2014 alongside the currently observing POLARBEAR-1 receiver, on a new telescope as a part of the Simons Array. The science goals of the POLARBEAR project are to do a deep search for B-mode polarization of the cosmic microwave background (CMB) created by inflationary gravitational waves, as well as characterize the CMB B-mode signal at smaller angular scales, where it originates from weak gravitational lensing. The Simons Array will include a total of three off-axis Gregorian telescopes with 3.5 m primary mirrors, located in the Chajnantor Astronomical Park in the Atacama Desert in Chile. Phased upgrades to receiver technology will enable us to improve sensitivity and capabilities, while continuing a deep survey of 80% of the sky. The POLARBEAR-2 receiver has a larger area focal plane with new dichroic pixels, with bands at 95 GHz and 150 GHz, and a total of 7,588 polarization sensitive antenna-coupled transition edge sensor bolometers. The focal plane is cooled to 250 milliKelvin, and the bolometers will be read-out by SQUID amplifiers with 32x frequency domain multiplexing. The focal plane is designed to have a noise equivalent temperature of 5.7 μK√s.

  14. Antenna-coupled Superconducting Bolometers for Observations of the Cosmic Microwave Background Polarization

    NASA Astrophysics Data System (ADS)

    Myers, Michael James

    We describe the development of a novel millimeter-wave cryogenic detector. The device integrates a planar antenna, superconducting transmission line, bandpass filter, and bolometer onto a single silicon wafer. The bolometer uses a superconducting Transition-Edge Sensor (TES) thermistor, which provides substantial advantages over conventional semiconductor bolometers. The detector chip is fabricated using standard micro-fabrication techniques. This highly-integrated detector architecture is particularly well-suited for use in the de- velopment of polarization-sensitive cryogenic receivers with thousands of pixels. Such receivers are needed to meet the sensitivity requirements of next-generation cosmic microwave background polarization experiments. The design, fabrication, and testing of prototype array pixels are described. Preliminary considerations for a full array design are also discussed. A set of on-chip millimeter-wave test structures were developed to help understand the performance of our millimeter-wave microstrip circuits. These test structures produce a calibrated transmission measurement for an arbitrary two-port circuit using optical techniques, rather than a network analyzer. Some results of fabricated test structures are presented.

  15. Investigation on global positioning system signal scattering and propagation over the rough sea surface

    NASA Astrophysics Data System (ADS)

    Yang, Chao; Guo, Li-Xin; Wu, Zhen-Sen

    2010-05-01

    This paper is devoted to the study of polarization properties, scattering properties and propagation properties of global positioning system (GPS) scattering signal over the rough sea surface. To investigate the polarization and the scattering properties, the scattering field and the bistatic scattering coefficient of modified Kirchhoff approximation using the tapered incident wave is derived in detail. In modeling the propagation properties of the GPS scattering signal in the evaporation duct, the initial field of parabolic equation traditionally computed by the antenna pattern using fast Fourier transform (FFT) is replaced by the GPS scattering field. And the propagation properties of the GPS scattering signal in the evaporation duct with different evaporation duct heights and elevation angles of GPS are discussed by the improved discrete mixed Fourier transform taking into account the sea surface roughness.

  16. Estimating the Ocean Flow Field From Combined Sea Surface Temperature and Sea Surface Height Data

    NASA Technical Reports Server (NTRS)

    Stammer, Detlef

    2000-01-01

    The primary focus of this project was on the estimation of the three-dimensional, absolute and time-evolving general circulation of the global ocean from a combined analysis of remotely sensed fields of sea surface temperature (SST) and sea surface height (SSH). The synthesis of those two fields was performed with other relevant physical data, and appropriate dynamical ocean models with emphasis on constraining ocean general circulation models by a combination of both SST and SSH data. This effort is directly related to an attempt to describe the mechanisms which give rise to observed SST and its variability on seasonal and inter-annual timescales, its relation to ocean-atmosphere interaction, and the dynamical coupling between the ocean mixed layer and the deep interior ocean. This is one of the fundamental climate related questions being pursued currently under the CLIVAR Program. Because of the strong turbulent mixing associated with atmospheric fluxes of momentum, heat and freshwater through the sea surface, the ocean forms a shallow surface boundary layer, the mixed layer which is largely homogeneous in its constituents. The relation between the temperature of the remotely sensed "skin" and the bulk of the mixed layer is largely understood (Reynolds and Smith 1994; Emery et al., 1995). However, because the surface mixed layer is effectively decoupled from the underlying ocean dynamics, an interpretation of satellite SST observations in isolation and in direct use for dynamical studies is very difficult. As a result, the impact of SST data on the understanding of ocean variability.

  17. Multisensor monitoring of sea surface state of the coastal zone

    NASA Astrophysics Data System (ADS)

    Lavrova, Olga; Mityagina, Marina; Bocharova, Tatina

    Results of many-year monitoring of the state of coastal zone based on a multisensor approach are presented. The monitoring is aimed at solving the following tasks: operational mapping of parameters characterizing the state and pollution (coastal, ship and biogenic) of water; analysis of meteorological state and its effect on the drift and spread of pollutants; study of coastal circulation patterns and their impact on the drift and spread of pollutants; deriving typical pollution distribution patterns in the coastal zone.Processing and analysis is performed using data in visual, infrared and microwave ranges from ERS-2 SAR, Envisat ASAR/MERIS, Terra and Aqua MODIS and NOAA AVHRR instruments. These are complimented with ground data from meteorological stations on the shore and results of satellite data processing of previous periods. The main regions of interest are the Russian sectors of the Black and Azov Seas, southeastern part of the Baltic Sea, and northern and central regions of the Caspian Sea. Adjacent coasts are extremely populated and have well-developed industry, agriculture and rapidly growing tourist sectors. The necessity of constant monitoring of the sea state there is obvious.The monitoring activities allow us to accumulate extensive material for the study of hydrodynamic processes in the regions, in particular water circulation. Detailing the occurrence, evolution and drift of smalland meso-scale vortex structures is crucial for the knowledge of the mechanisms determining mixing and circulation processes in the coastal zone. These mechanisms play an important role in ecological, hydrodynamic and meteorological status of a coastal zone. Special attention is paid to the sea surface state in the Kerch Strait, where a tanker catastrophe took place on November 11, 2007 causing a spillage of over 1.5 thousand tons of heavy oil. The Kerch Strait is characterized by a complex current system with current directions changing to their opposites depending on

  18. On discrimination between film slicks and "look-alikes" on the sea surface in multifrequency radar images

    NASA Astrophysics Data System (ADS)

    Sergievskaya, Irina; Ermakov, Stanislav A.; Kapustin, Ivan

    2015-10-01

    Slicks on the sea surface are characterized by attenuation of short wind waves and appear in radar imagery at moderate incidence angles as areas of reduced intensity. In the proximity of oil platforms, ship routes, fish farms, etc. marine slicks are often identified as oil spills or biogenic films. However, probability of false alarm when detecting film slicks is very high because of the occurrence of structures in radar images looking similar but not related to surface films ("lookalikes"). One of the most frequent "look-alikes" is wind depression areas (WDAs) where the wind excitation of short surface waves is reduced compared to the ambient background. Results of field observations of films slicks and WDA are described and differences in character of wind wave attenuation in different parts of the wind wave spectrum are revealed. Model calculations of wave damping degree (contrast) in film slick and in WDA are carried out and are shown to be in general agreement with experiment. Capabilities of dual-polarization and multi-band microwave radar for discrimination between film slicks and "look-alikes" are analyzed based on experiment and model results.

  19. A multispectral method of determining sea surface temperatures

    NASA Technical Reports Server (NTRS)

    Shenk, W. E.

    1972-01-01

    A multispectral method for determining sea surface temperatures is discussed. The specifications of the equipment and the atmospheric conditions required for successful multispectral data acquisition are described. Examples of data obtained in the North Atlantic Ocean are presented. The differences between the actual sea surface temperatures and the equivalent blackbody temperatures as determined by a radiometer are plotted.

  20. Improved dark energy detection through the polarization-assisted cross correlation of the cosmic microwave background with radio sources

    SciTech Connect

    Liu, Guo-Chin; Ng, Kin-Wang; Pen, Ue-Li

    2011-03-15

    Integrated Sachs-Wolfe (ISW) effect can be estimated by cross-correlating the cosmic microwave background (CMB) sky with tracers of the local matter distribution. At late cosmic time, the dark energy-induced decay of gravitation potential generates a cross correlation signal on large angular scales. The dominant noise is the intrinsic CMB anisotropies from the inflationary epoch. In this paper we use CMB polarization to reduce this intrinsic noise. We cross-correlate the microwave sky observed by Wilkinson Microwave Anisotropy Probe (WMAP) with the radio source catalog compiled by NRAO VLA Sky Survey (NVSS) to study the efficiency of the noise suppression. We find that the error bars are reduced by about 4 to 14% and the statistical power in the signal is improved.

  1. Mapping photosynthetically available radiation at the sea surface using GOCI

    NASA Astrophysics Data System (ADS)

    Choi, Jongkuk; Kim, Jihye; Yang, Hyun; Moon, Jeong-Eon; Frouin, Robert

    2016-04-01

    Photosynthetically available radiation (PAR) controls the composition of marine ecosystem by affecting the growth of phytoplankton, thus estimating PAR at the ocean surface accurately is important to understand the marine ecological environment. Although many studies have been attempted to estimate PAR employing ocean colour satellite data since 2003, previous studies using data from the polar orbit systems had spatial and temporal limitations to estimate accurate daily PAR. Here, we estimate daily PAR from Geostationary Ocean Colour Imager (GOCI) which collects data eight times a day at an hour interval in daytime and compare it with in-situ measurement and MODIS-based daily PAR. The algorithm we developed in this study, employed GOCI visible bands (centred at (412, 443, 490, 555, 660, 680 nm) which belongs to the range of PAR by calculating albedo at the layer of clouds and the sea surface to estimate daily PAR. The resultant value was validated by comparing the in-situ measurements acquired from an ocean research station, Socheongcho between February and May 2015, which showed a similar pattern with somewhat GOCI-base PAR's overestimations. The comparison with the results from MODIS, a polar orbit system showed that a good agreement with each other was illustrated at clear sky conditions, while MODIS showed some over- or underestimations at cloudy conditions with irregular patterns. This study shows that GOCI can estimate effectively the daily PAR with its advantages of acquiring data more frequently than other polar orbit ocean colour satellites by reducing the uncertainties induced by insufficient images to map the daily PAR at ocean surface.

  2. Calibration of Suomi national polar-orbiting partnership advanced technology microwave sounder

    NASA Astrophysics Data System (ADS)

    Weng, Fuzhong; Zou, Xiaolei; Sun, Ninghai; Yang, Hu; Tian, Miao; Blackwell, William J.; Wang, Xiang; Lin, Lin; Anderson, Kent

    2013-10-01

    The Suomi National Polar-Orbiting Partnership (NPP) satellite was launched on 28 October 2011 and carries the Advanced Technology Microwave Sounder (ATMS) on board. ATMS is a cross-track scanning instrument observing in 22 channels at frequencies ranging from 23 to 183 GHz, permitting the measurements of the atmospheric temperature and moisture under most weather conditions. In this study, the ATMS radiometric calibration algorithm used in the operational system is first evaluated through independent analyses of prelaunch thermal vacuum data. It is found that the ATMS peak nonlinearity for all the channels is less than 0.5 K, which is well within the specification. For the characterization of the ATMS instrument sensitivity or noise equivalent differential temperatures (NEDT), both standard deviation and Allan variance of warm counts are computed and compared. It is shown that NEDT derived from the standard deviation is about three to five times larger than that from the Allan variance. The difference results from a nonstationary component in the standard deviation of warm counts. The Allan variance is better suited than the standard deviation for describing NEDT. In the ATMS sensor brightness temperature data record (SDR) processing algorithm, the antenna gain efficiencies of main beam, cross-polarization beam, and side lobes must be derived accurately from the antenna gain distribution function. However, uncertainties remain in computing the efficiencies at ATMS high frequencies. Thus, ATMS antenna brightness temperature data records (TDR) at channels 1 to 15 are converted to SDR with the actual beam efficiencies whereas those for channels 16 to 22 are only corrected for the near-field sidelobe contributions. The biases of ATMS SDR measurements to the simulations are consistent between GPS RO and NWP data and are generally less than 0.5 K for those temperature-sounding channels where both the forward model and input atmospheric profiles are reliable.

  3. Evidence for gravitational lensing of the cosmic microwave background polarization from cross-correlation with the cosmic infrared background.

    PubMed

    Ade, P A R; Akiba, Y; Anthony, A E; Arnold, K; Atlas, M; Barron, D; Boettger, D; Borrill, J; Borys, C; Chapman, S; Chinone, Y; Dobbs, M; Elleflot, T; Errard, J; Fabbian, G; Feng, C; Flanigan, D; Gilbert, A; Grainger, W; Halverson, N W; Hasegawa, M; Hattori, K; Hazumi, M; Holzapfel, W L; Hori, Y; Howard, J; Hyland, P; Inoue, Y; Jaehnig, G C; Jaffe, A; Keating, B; Kermish, Z; Keskitalo, R; Kisner, T; Le Jeune, M; Lee, A T; Leitch, E M; Linder, E; Lungu, M; Matsuda, F; Matsumura, T; Meng, X; Miller, N J; Morii, H; Moyerman, S; Myers, M J; Navaroli, M; Nishino, H; Paar, H; Peloton, J; Poletti, D; Quealy, E; Rebeiz, G; Reichardt, C L; Richards, P L; Ross, C; Rotermund, K; Schanning, I; Schenck, D E; Sherwin, B D; Shimizu, A; Shimmin, C; Shimon, M; Siritanasak, P; Smecher, G; Spieler, H; Stebor, N; Steinbach, B; Stompor, R; Suzuki, A; Takakura, S; Tikhomirov, A; Tomaru, T; Wilson, B; Yadav, A; Zahn, O

    2014-04-01

    We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0σ and indication of the presence of a lensing B-mode signal at a significance of 2.3σ. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces POLARBEAR auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics. PMID:24745402

  4. Evidence for Gravitational Lensing of the Cosmic Microwave Background Polarization from Cross-Correlation with the Cosmic Infrared Background

    NASA Astrophysics Data System (ADS)

    Ade, P. A. R.; Akiba, Y.; Anthony, A. E.; Arnold, K.; Atlas, M.; Barron, D.; Boettger, D.; Borrill, J.; Borys, C.; Chapman, S.; Chinone, Y.; Dobbs, M.; Elleflot, T.; Errard, J.; Fabbian, G.; Feng, C.; Flanigan, D.; Gilbert, A.; Grainger, W.; Halverson, N. W.; Hasegawa, M.; Hattori, K.; Hazumi, M.; Holzapfel, W. L.; Hori, Y.; Howard, J.; Hyland, P.; Inoue, Y.; Jaehnig, G. C.; Jaffe, A.; Keating, B.; Kermish, Z.; Keskitalo, R.; Kisner, T.; Le Jeune, M.; Lee, A. T.; Leitch, E. M.; Linder, E.; Lungu, M.; Matsuda, F.; Matsumura, T.; Meng, X.; Miller, N. J.; Morii, H.; Moyerman, S.; Myers, M. J.; Navaroli, M.; Nishino, H.; Paar, H.; Peloton, J.; Poletti, D.; Quealy, E.; Rebeiz, G.; Reichardt, C. L.; Richards, P. L.; Ross, C.; Rotermund, K.; Schanning, I.; Schenck, D. E.; Sherwin, B. D.; Shimizu, A.; Shimmin, C.; Shimon, M.; Siritanasak, P.; Smecher, G.; Spieler, H.; Stebor, N.; Steinbach, B.; Stompor, R.; Suzuki, A.; Takakura, S.; Tikhomirov, A.; Tomaru, T.; Wilson, B.; Yadav, A.; Zahn, O.; Polarbear Collaboration

    2014-04-01

    We reconstruct the gravitational lensing convergence signal from cosmic microwave background (CMB) polarization data taken by the Polarbear experiment and cross-correlate it with cosmic infrared background maps from the Herschel satellite. From the cross spectra, we obtain evidence for gravitational lensing of the CMB polarization at a statistical significance of 4.0σ and indication of the presence of a lensing B-mode signal at a significance of 2.3σ. We demonstrate that our results are not biased by instrumental and astrophysical systematic errors by performing null tests, checks with simulated and real data, and analytical calculations. This measurement of polarization lensing, made via the robust cross-correlation channel, not only reinforces POLARBEAR auto-correlation measurements, but also represents one of the early steps towards establishing CMB polarization lensing as a powerful new probe of cosmology and astrophysics.

  5. Effects of irregular sea surface and evaporation duct on radar detection performance

    NASA Astrophysics Data System (ADS)

    Marom, Moshe

    1988-06-01

    The detection performance of microwave search radars operating in close proximity to the sea surface is evaluated. The effects of media characteristics on the propagation of electromagnetic waves have been incorporated. Specular and diffused scattering from a rough surface, and the effects of the curvature of the earth's surface have been included in the study. Additionally, surface ducting effects caused by atmospheric anomalies are presented. Some design and operational considerations which can improve the detection performance of a surface search radar, are also presented.

  6. Variations and climatology of CI0 in the polar lower stratosphere from UARS Microwave Limb Sounder measurements

    NASA Technical Reports Server (NTRS)

    Santee, M. L.; Manney, G. L.; Water, J. W.; Livesey, N. J.

    2002-01-01

    The Microwave Limb Sounder (MLS) on board the Upper Atmosphere Research Satellite (UARS) measured the global distribution of stratospheric ClO over annual cycles for much of the 1990s, albeit with reduced sampling frequency in the latter half of the decade. Here we present an overview of the interannual and interhemispheric variations in the distribution of ClO derived from UARS MLS measurements, with a particular emphasis on enhancements in the winter polar lower stratosphere.

  7. Litmus Test for Cosmic Hemispherical Asymmetry in the Cosmic Microwave Background B -Mode Polarization

    NASA Astrophysics Data System (ADS)

    Mukherjee, Suvodip; Souradeep, Tarun

    2016-06-01

    Recent measurements of the temperature field of the cosmic microwave background (CMB) provide tantalizing evidence for violation of statistical isotropy (SI) that constitutes a fundamental tenet of contemporary cosmology. CMB space based missions, WMAP, and Planck have observed a 7% departure in the SI temperature field at large angular scales. However, due to higher cosmic variance at low multipoles, the significance of this measurement is not expected to improve from any future CMB temperature measurements. We demonstrate that weak lensing of the CMB due to scalar perturbations produces a corresponding SI violation in B modes of CMB polarization at smaller angular scales. The measurability of this phenomenon depends upon the scales (l range) over which power asymmetry is present. Power asymmetry, which is restricted only to l <64 in the temperature field, cannot lead to any significant observable effect from this new window. However, this effect can put an independent bound on the spatial range of scales of hemispherical asymmetry present in the scalar sector.

  8. A triple-band, polarization- and incident angle-independent microwave metamaterial absorber with interference theory

    NASA Astrophysics Data System (ADS)

    Chen, Junfeng; Hu, Zhaoyang; Wang, Shengming; Huang, Xiutao; Liu, Minghai

    2016-01-01

    We present the design, fabrication and characterization of an ultrathin triple-band metamaterial absorber (MMA) in the microwave frequencies. The unit cell of the MMA consists of three different sizes of electric split ring resonators (eSRRs) and continuous metal film separated by only 1 mm dielectric substrate. The single-band MMA of this structure is firstly investigated. Then, by tuning the scale factor of the unit cells, the proposed triple-band MMA achieves absorption peaks at 9.85 GHz, 13.05 GHz and 14.93 GHz, respectively. Electric field distributions at three resonant frequencies are investigated to qualitatively analyze the loss mechanism. The further simulated and experimental results indicate that the proposed MMA is also polarization- and incident angle-independent. Finally, the interference theory is introduced to quantitatively analyze the MMA, which provides good insight into the physics behind the absorbing structure. To calculate the absorption rates accurately, we employ a simulation strategy make the near-field coupling between two metallic layers get back (compensation method). The measured absorption spectra show an excellent agreement with the theoretical calculation and simulation results. Therefore, the explanation to the physical mechanism of the triple-band MMA is presented and verified.

  9. Born-corrections to weak lensing of the cosmic microwave background temperature and polarization anisotropies

    NASA Astrophysics Data System (ADS)

    Hagstotz, Steffen; Schäfer, Björn Malte; Merkel, Philipp M.

    2015-11-01

    Many weak-lensing calculations make use of the Born approximation where the light ray is approximated by a straight path. We examine the effect of Born-corrections for lensing of the cosmic microwave background (CMB) in an analytical approach by taking perturbative corrections to the geodesic into account. The resulting extra power in the lensing potential spectrum is comparable to the power generated by non-linear structure formation and affects especially the polarization spectra, leading to relative changes of the order of 10-3 for the E-mode spectrum and several per cent on all scales to the B-mode spectrum. In contrast, there is only little change of spectra involving the CMB temperature. Additionally, the corrections excite one more degree of freedom resulting in a deflection component which cannot be described as a gradient of the lensing potential as it is related to image rotation in lens-lens coupling. We estimate the magnitude of this effect on the CMB spectra and find it to be negligible.

  10. Litmus Test for Cosmic Hemispherical Asymmetry in the Cosmic Microwave Background B-Mode Polarization.

    PubMed

    Mukherjee, Suvodip; Souradeep, Tarun

    2016-06-01

    Recent measurements of the temperature field of the cosmic microwave background (CMB) provide tantalizing evidence for violation of statistical isotropy (SI) that constitutes a fundamental tenet of contemporary cosmology. CMB space based missions, WMAP, and Planck have observed a 7% departure in the SI temperature field at large angular scales. However, due to higher cosmic variance at low multipoles, the significance of this measurement is not expected to improve from any future CMB temperature measurements. We demonstrate that weak lensing of the CMB due to scalar perturbations produces a corresponding SI violation in B modes of CMB polarization at smaller angular scales. The measurability of this phenomenon depends upon the scales (l range) over which power asymmetry is present. Power asymmetry, which is restricted only to l<64 in the temperature field, cannot lead to any significant observable effect from this new window. However, this effect can put an independent bound on the spatial range of scales of hemispherical asymmetry present in the scalar sector. PMID:27314711

  11. High-precision simulations of the weak lensing effect on cosmic microwave background polarization

    NASA Astrophysics Data System (ADS)

    Fabbian, Giulio; Stompor, Radek

    2013-08-01

    We studied the accuracy, robustness, and self-consistency of pixel-domain simulations of the gravitational lensing effect on the primordial cosmic microwave background (CMB) anisotropies due to the large-scale structure of the Universe. In particular, we investigated the dependence of the precision of the results precision on some crucial parameters of these techniques and propose a semi-analytic framework to determine their values so that the required precision is a priori assured and the numerical workload simultaneously optimized. Our focus was on the B-mode signal, but we also discuss other CMB observables, such as the total intensity, T, and E-mode polarization, emphasizing differences and similarities between all these cases. Our semi-analytic considerations are backed up by extensive numerical results. Those are obtained using a code, nicknamed lenS2HAT - for lensing using scalable spherical harmonic transforms (S2HAT) - which we have developed in the course of this work. The code implements a version of the previously described pixel-domain approach and permits performing the simulations at very high resolutions and data volumes, thanks to its efficient parallelization provided by the S2HAT library - a parallel library for calculating of the spherical harmonic transforms. The code is made publicly available.

  12. Use of superconducting bearings to measure the polarization of the cosmic microwave background radiation.

    SciTech Connect

    Hanany, S.; Matsumura, T.; Johnson, B.; Jones, T.; Hull, J. R.; Ma, K. B.

    2002-08-21

    Measurements of the polarization of the cosmic microwave background (CMB) radiation are expected to significantly increase our understanding of the early universe. We present a design for a CMB polarimeter in which a cryogenically cooled half wave plate rotates by means of a high-temperature superconducting (HTS) bearing. The design is optimized for implementation in MAXIPOL, a balloon-borne CMB polarimeter. A prototype bearing, consisting of commercially available ring-shaped permanent magnet and an array of YBCO bulk HTS material, has been constructed. We report on measurements of the coefficient of friction as a function of temperature between 15 and 80 K, of rotation frequency between 0.3 and 3.5 Hz, of levitation distance between 6 and 10 mm, and of ambient pressure between 1 and 10{sup -7} torr. The low rotational drag of the HTS bearing allows rotations for long periods of time with minimal input power and negligible wear and tear thus making this technology suitable for a future satellite mission.

  13. An atlas of monthly mean distributions of SSMI surface wind speed, AVHRR/2 sea surface temperature, AMI surface wind velocity, TOPEX/POSEIDON sea surface height, and ECMWF surface wind velocity during 1993

    NASA Technical Reports Server (NTRS)

    Halpern, D.; Fu, L.; Knauss, W.; Pihos, G.; Brown, O.; Freilich, M.; Wentz, F.

    1995-01-01

    The following monthly mean global distributions for 1993 are presented with a common color scale and geographical map: 10-m height wind speed estimated from the Special Sensor Microwave Imager (SSMI) on a United States (U.S.) Air Force Defense Meteorological Satellite Program (DMSP) spacecraft; sea surface temperature estimated from the Advanced Very High Resolution Radiometer (AVHRR/2) on a U.S. National Oceanic and Atmospheric Administration (NOAA) satellite; 10-m height wind speed and direction estimated from the Active Microwave Instrument (AMI) on the European Space Agency (ESA) European Remote Sensing (ERS-1) satellite; sea surface height estimated from the joint U.S.-France Topography Experiment (TOPEX)/POSEIDON spacecraft; and 10-m height wind speed and direction produced by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of annual mean, monthly mean, and sampling distributions are displayed.

  14. The weighted curvature approximation in scattering from sea surfaces

    NASA Astrophysics Data System (ADS)

    Guérin, Charles-Antoine; Soriano, Gabriel; Chapron, Bertrand

    2010-07-01

    A family of unified models in scattering from rough surfaces is based on local corrections of the tangent plane approximation through higher-order derivatives of the surface. We revisit these methods in a common framework when the correction is limited to the curvature, that is essentially the second-order derivative. The resulting expression is formally identical to the weighted curvature approximation, with several admissible kernels, however. For sea surfaces under the Gaussian assumption, we show that the weighted curvature approximation reduces to a universal and simple expression for the off-specular normalized radar cross-section (NRCS), regardless of the chosen kernel. The formula involves merely the sum of the NRCS in the classical Kirchhoff approximation and the NRCS in the small perturbation method, except that the Bragg kernel in the latter has to be replaced by the difference of a Bragg and a Kirchhoff kernel. This result is consistently compared with the resonant curvature approximation. Some numerical comparisons with the method of moments and other classical approximate methods are performed at various bands and sea states. For the copolarized components, the weighted curvature approximation is found numerically very close to the cut-off invariant two-scale model, while bringing substantial improvement to both the Kirchhoff and small-slope approximation. However, the model is unable to predict cross-polarization in the plane of incidence. The simplicity of the formulation opens new perspectives in sea state inversion from remote sensing data.

  15. The Effect of Ocean Currents on Sea Surface Temperature Anomalies

    NASA Technical Reports Server (NTRS)

    Stammer, Detlef; Leeuwenburgh, Olwijn

    2000-01-01

    We investigate regional and global-scale correlations between observed anomalies in sea surface temperature and height. A strong agreement between the two fields is found over a broad range of latitudes for different ocean basins. Both time-longitude plots and wavenumber-frequency spectra suggest an advective forcing of SST anomalies by a first-mode baroclinic wave field on spatial scales down to 400 km and time scales as short as 1 month. Even though the magnitude of the mean background temperature gradient is determining for the effectiveness of the forcing, there is no obvious seasonality that can be detected in the amplitudes of SST anomalies. Instead, individual wave signatures in the SST can in some cases be followed over periods of two years. The phase relationship between SST and SSH anomalies is dependent upon frequency and wavenumber and displays a clear decrease of the phase lag toward higher latitudes where the two fields come into phase at low frequencies. Estimates of the damping coefficient are larger than generally obtained for a purely atmospheric feedback. From a global frequency spectrum a damping time scale of 2-3 month was found. Regionally results are very variable and range from 1 month near strong currents to 10 month at low latitudes and in the sub-polar North Atlantic. Strong agreement is found between the first global EOF modes of 10 day averaged and spatially smoothed SST and SSH grids. The accompanying time series display low frequency oscillations in both fields.

  16. Low-frequency microwave radiometer for N-ROSS

    NASA Technical Reports Server (NTRS)

    Hollinger, J. P.; Lo, R. C.

    1985-01-01

    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 esstential parameters of the low frequency microwave radiometer (LFMR). It will be a dual polarized, dual frequency system at 5.2 and 10.4 GHz using a 4.9 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.

  17. A reevaluation of Stogryn's apparent temperature theory over the sea surface

    NASA Technical Reports Server (NTRS)

    Fung, A. K.; Eom, H. J.

    1984-01-01

    The emission theory for the sea surface by Stogryn has been reevaluated. Results agree with Stogryn's paper except for small nadir angles where the apparent temperature versus wind speed behavior is in reverse of what was reported by Stogryn. By plotting the change in contributions by the sea surface emission and sky temperature scattered toward the radiometer as a function of nadir angle at two different wind speeds, it is found that the sky temperature effect is dominating at small nadir angles, while the change in surface emission becomes increasingly more important at larger nadir angles. It is also found that at nadir higher emission is associated with the polarization where E(arrow) field is aligned along the upwind direction than the one along the crosswind direction.

  18. Annual variations in sea surface wind speed around Japan observed by ASCAT

    NASA Astrophysics Data System (ADS)

    Takeyama, Y.; Shimada, S.; Ohsawa, T.; Kozai, K.; Kogaki, T.

    2015-12-01

    Sea surface wind speeds and these statistics can be applied for many marine industrial activities. For example, the averaged wind speed is crucial information for a site selection of an offshore wind farm. It has widely been recognized that a total amount of the offshore wind generation is strongly depended on the annual average wind speeds. A advanced scatterometer (ASCAT), which is a kind of scatterometer aboard METOP-A and B, has observed sea surface wind speeds at the height of 10 m above the sea surface approximately twice a day using active microwaves. The annual average wind speed can be calculated from the observed wind speed. For an actual use of the annual average wind speed, generalities and representativeness of the wind speed must be clarified. To investigate annual variations in sea surface wind speed around Japan (120°E to 165°E, 19°N to 49°N), the annual average wind speeds and these standard deviations are calculated from 5 years of ASCAT observations from 2010 through 2014. It is found that there are some sea areas where standard deviations are relatively higher than their surroundings. Annual average wind speed maps indicate that the high standard deviation is caused by strong winds from Eurasia in the winter of 2011 in part of North Pacific Ocean and Sea of Okhotsk. Additionally standard deviations for only winter are also higher than for summer in those sea areas. Therefore the strong wind speed in the winter of a particular year can easily affect to the annual average wind speed. Meanwhile off the coast of Niigata and Hokkaido, there are also higher standard deviation areas than their surroundings. Differences between monthly maximum wind speeds for the winter and minimum wind speeds for the summer in these areas are larger and the large differences seem to be a cause of the high standard deviations.

  19. Correlations between altimetric sea surface height and radiometric sea surface temperature in the South Atlantic

    NASA Astrophysics Data System (ADS)

    Jones, Matthew S.; Allen, Myles; Guymer, Trevor; Saunders, Mark

    1998-04-01

    In the last decade, satellite altimetric measurements of sea surface height (SSH) and infrared radiometric measurements of sea surface temperature (SST) have provided a wealth of information about ocean circulation and atmosphere-ocean interactions. SSH is a depth-integrated quantity dependent upon the temperature and salinity structure of the water column and on the depth independent barotropic contribution. SST from infrared radiometers is a surface parameter representing the temperature of the top few microns of the ocean surface. Hence any relationship between SST and SSH provides dynamical information about the coupling between the ocean surface and subsurface. It also offers a promise of new techniques such as interpolating SSH data using SST and of improved calculations of eddy kinetic energy. We use SST data from the along-track scanning radiometer on ERS-I and SSH data from the TOPEX/POSEIDON instrument to examine the relationship between SST and SSH anomalies within the South Atlantic region for 1993 and 1994. We find that positive (≈0.2-0.6) spatial cross correlations between SST and SSH anomalies at zero lag are present throughout the region at large scales (wavelengths >1000 km). Small-scale correlations, however, are high (≈0.7) only in areas associated with fronts and mesoscale variability. These small-scale correlations are seasonal, being strongest in winter and weakest in summer. We discuss the application of these correlations to various techniques requiring the synergistic use of SSH and SST data.

  20. Estimating the Ocean Flow Field from Combined Sea Surface Temperature and Sea Surface Height Data

    NASA Technical Reports Server (NTRS)

    Stammer, Detlef; Lindstrom, Eric (Technical Monitor)

    2002-01-01

    This project was part of a previous grant at MIT that was moved over to the Scripps Institution of Oceanography (SIO) together with the principal investigator. The final report provided here is concerned only with the work performed at SIO since January 2000. The primary focus of this project was the study of the three-dimensional, absolute and time-evolving general circulation of the global ocean from a combined analysis of remotely sensed fields of sea surface temperature (SST) and sea surface height (SSH). The synthesis of those two fields was performed with other relevant physical data, and appropriate dynamical ocean models with emphasis on constraining ocean general circulation models by a combination of both SST and SSH data. The central goal of the project was to improve our understanding and modeling of the relationship between the SST and its variability to internal ocean dynamics, and the overlying atmosphere, and to explore the relative roles of air-sea fluxes and internal ocean dynamics in establishing anomalies in SST on annual and longer time scales. An understanding of those problems will feed into the general discussion on how SST anomalies vary with time and the extend to which they interact with the atmosphere.

  1. SECOND SEASON QUIET OBSERVATIONS: MEASUREMENTS OF THE COSMIC MICROWAVE BACKGROUND POLARIZATION POWER SPECTRUM AT 95 GHz

    SciTech Connect

    Araujo, D.; Dumoulin, R. N.; Newburgh, L. B.; Zwart, J. T. L.; Bischoff, C.; Brizius, A.; Buder, I.; Kusaka, A.; Chinone, Y.; Cleary, K.; Reeves, R.; Naess, S. K.; Eriksen, H. K.; Wehus, I. K.; Bronfman, L.; Church, S. E.; Dickinson, C.; Gaier, T.; Collaboration: QUIET Collaboration; and others

    2012-12-01

    The Q/U Imaging ExperimenT (QUIET) has observed the cosmic microwave background (CMB) at 43 and 95 GHz. The 43 GHz results have been published in a previous paper, and here we report the measurement of CMB polarization power spectra using the 95 GHz data. This data set comprises 5337 hr of observations recorded by an array of 84 polarized coherent receivers with a total array sensitivity of 87 {mu}K{radical}s. Four low-foreground fields were observed, covering a total of {approx}1000 deg{sup 2} with an effective angular resolution of 12.'8, allowing for constraints on primordial gravitational waves and high signal-to-noise measurements of the E-modes across three acoustic peaks. The data reduction was performed using two independent analysis pipelines, one based on a pseudo-C {sub l} (PCL) cross-correlation approach, and the other on a maximum-likelihood (ML) approach. All data selection criteria and filters were modified until a predefined set of null tests had been satisfied before inspecting any non-null power spectrum. The results derived by the two pipelines are in good agreement. We characterize the EE, EB, and BB power spectra between l = 25 and 975 and find that the EE spectrum is consistent with {Lambda}CDM, while the BB power spectrum is consistent with zero. Based on these measurements, we constrain the tensor-to-scalar ratio to r = 1.1{sup +0.9} {sub -0.8} (r < 2.8 at 95% C.L.) as derived by the ML pipeline, and r = 1.2{sup +0.9} {sub -0.8} (r < 2.7 at 95% C.L.) as derived by the PCL pipeline. In one of the fields, we find a correlation with the dust component of the Planck Sky Model, though the corresponding excess power is small compared to statistical errors. Finally, we derive limits on all known systematic errors, and demonstrate that these correspond to a tensor-to-scalar ratio smaller than r = 0.01, the lowest level yet reported in the literature.

  2. Second Season QUIET Observations: Measurements of the Cosmic Microwave Background Polarization Power Spectrum at 95 GHz

    NASA Astrophysics Data System (ADS)

    QUIET Collaboration; Araujo, D.; Bischoff, C.; Brizius, A.; Buder, I.; Chinone, Y.; Cleary, K.; Dumoulin, R. N.; Kusaka, A.; Monsalve, R.; Næss, S. K.; Newburgh, L. B.; Reeves, R.; Wehus, I. K.; Zwart, J. T. L.; Bronfman, L.; Bustos, R.; Church, S. E.; Dickinson, C.; Eriksen, H. K.; Gaier, T.; Gundersen, J. O.; Hasegawa, M.; Hazumi, M.; Huffenberger, K. M.; Ishidoshiro, K.; Jones, M. E.; Kangaslahti, P.; Kapner, D. J.; Kubik, D.; Lawrence, C. R.; Limon, M.; McMahon, J. J.; Miller, A. D.; Nagai, M.; Nguyen, H.; Nixon, G.; Pearson, T. J.; Piccirillo, L.; Radford, S. J. E.; Readhead, A. C. S.; Richards, J. L.; Samtleben, D.; Seiffert, M.; Shepherd, M. C.; Smith, K. M.; Staggs, S. T.; Tajima, O.; Thompson, K. L.; Vanderlinde, K.; Williamson, R.

    2012-12-01

    The Q/U Imaging ExperimenT (QUIET) has observed the cosmic microwave background (CMB) at 43 and 95 GHz. The 43 GHz results have been published in a previous paper, and here we report the measurement of CMB polarization power spectra using the 95 GHz data. This data set comprises 5337 hr of observations recorded by an array of 84 polarized coherent receivers with a total array sensitivity of 87 μK\\sqrt{s}. Four low-foreground fields were observed, covering a total of ~1000 deg2 with an effective angular resolution of 12farcm8, allowing for constraints on primordial gravitational waves and high signal-to-noise measurements of the E-modes across three acoustic peaks. The data reduction was performed using two independent analysis pipelines, one based on a pseudo-C l (PCL) cross-correlation approach, and the other on a maximum-likelihood (ML) approach. All data selection criteria and filters were modified until a predefined set of null tests had been satisfied before inspecting any non-null power spectrum. The results derived by the two pipelines are in good agreement. We characterize the EE, EB, and BB power spectra between l = 25 and 975 and find that the EE spectrum is consistent with ΛCDM, while the BB power spectrum is consistent with zero. Based on these measurements, we constrain the tensor-to-scalar ratio to r = 1.1+0.9 - 0.8 (r < 2.8 at 95% C.L.) as derived by the ML pipeline, and r = 1.2+0.9 - 0.8 (r < 2.7 at 95% C.L.) as derived by the PCL pipeline. In one of the fields, we find a correlation with the dust component of the Planck Sky Model, though the corresponding excess power is small compared to statistical errors. Finally, we derive limits on all known systematic errors, and demonstrate that these correspond to a tensor-to-scalar ratio smaller than r = 0.01, the lowest level yet reported in the literature.

  3. Observational Strategies of Cosmic Microwave Background Temperature and Polarization Interferometry Experiments

    NASA Astrophysics Data System (ADS)

    Park, Chan-Gyung; Ng, Kin-Wang; Park, Changbom; Liu, Guo-Chin; Umetsu, Keiichi

    2003-05-01

    We have simulated the interferometric observation of the cosmic microwave background (CMB) temperature and polarization fluctuations. We have constructed data pipelines from the time-ordered raw visibility samples to the CMB power spectra that utilize the methods of data compression, maximum likelihood analysis, and optimal subspace filtering. They are customized for three observational strategies: the single pointing, the mosaicking, and the drift-scanning. For each strategy, derived are the optimal strategy parameters that yield band power estimates with minimum uncertainty. The results are general and can be applied to any close-packed array on a single platform such as the CBI and the forthcoming AMiBA experiments. We have also studied the effect of rotation of the array platform on the band power correlation by simulating the CBI single-pointing observation. It is found that the band power anticorrelations can be reduced by rotating the platform and thus densely sampling the visibility plane. This enables us to increase the resolution of the power spectrum in the l-space down to the limit of the sampling theorem (Δl=226~π/θ), which is narrower by a factor of about sqrt(2) than the resolution limit (Δl~300) used in the recent CBI single-pointing observation. The validity of this idea is demonstrated for a two-element interferometer that samples visibilities uniformly in the uv-annulus. From the fact that the visibilities are the Fourier modes of the CMB field convolved with the beam, a fast unbiased estimator (FUE) of the CMB power spectra is developed and tested. It is shown that the FUE gives results very close to those from the quadratic estimator method without requiring large computer resources even though uncertainties in the results increase.

  4. Upper ocean flow statistics estimated from superresolved sea-surface temperature images

    NASA Astrophysics Data System (ADS)

    Keating, Shane R.; Smith, K. Shafer

    2015-02-01

    Ocean turbulence on scales of 10-50 km plays a key role in biogeochemical processes, frontal dynamics, and tracer transport in the upper ocean, but our understanding of these scales is limited because they are too small to be resolved using extant satellite altimetry products. By contrast, microwave imagery of the sea-surface temperature field does resolve these scales and can be used to estimate the upper ocean flow field due to the strong correlation between the surface density field and the interior potential vorticity. However, because the surface density (or temperature) is a smoothed version of the geostrophic stream function, the resulting velocity field estimates are limited to scales of 100-300 km in the first few hundred meters of the water column. A method is proposed for generating superresolved sea-surface temperature images using direct low-resolution (microwave) temperature observations in combination with an empirical parameterization for the unresolved scales modeled on statistical information from high-resolution (infrared) imagery. Because the method relies only on the statistics of the small-scale field, it is insensitive to data outages due to cloud cover that affect infrared observations. The method enhances the effective resolution of the temperature images by exploiting the effect of spatial aliasing and generates an optimal estimate of the small-scale temperature field using standard Bayesian inference. The technique is tested in quasigeostrophic simulations driven by realistic climatological shear and stratification profiles for three contrasting regions at high, middle, and low latitudes. The resulting superresolved sea-surface temperature images are then used to estimate the three-dimensional velocity field in the upper ocean on scales of 10-50 km.

  5. The interaction of polarized microwaves with planar arrays of femtosecond laser-produced plasma filaments in air

    SciTech Connect

    Marian, Anca; El Morsli, Mbark; Vidal, Francois; Payeur, Stephane; Kieffer, Jean-Claude; Chateauneuf, Marc; Theberge, Francis; Dubois, Jacques

    2013-02-15

    The interaction of polarized microwaves with subwavelength arrays of parallel plasma filaments, such as those produced by the propagation of high-power femtosecond laser pulses in ambient air, was investigated by calculating the reflection and transmission coefficients as a function of the incidence angles using the finite-difference time-domain (FDTD) method. The time evolution of these coefficients was calculated and compared with experiments. It is found that the plasma filaments array becomes transparent when the polarization of the microwave radiation is perpendicular to the filaments axis, regardless the incidence angle of the microwave with respect to the filaments, except near grazing incidence. Increasing the filaments electron density or diameter, or decreasing the electron collision frequency or filaments spacing, decreases the transmission and increases the reflection. Transmission decreases when increasing the number of filament layers while reflection remains unchanged as the number of filament layers exceeds a given number ({approx}3 in our case). Transmission slightly increases when disorder is introduced in the filament arrays. The detailed calculation results are compared with those obtained from the simple birefringent slab model, which provides a convenient framework to calculate approximately the properties of filament arrays.

  6. Three-dimensional effects in polarization signatures as observed from precipitating clouds by low frequency ground-based microwave radiometers

    NASA Astrophysics Data System (ADS)

    Battaglia, A.; Simmer, C.; Czekala, H.

    2006-09-01

    Consistent negative polarization differences (i.e. differences between the vertical and the horizontal brightness temperature) are observed when looking at precipitating systems by ground-based radiometers at slant angles. These signatures can be partially explained by one-dimensional radiative transfer computations that include oriented non-spherical raindrops. However some cases are characterized by polarization values that exceed differences expected from one-dimensional radiative transfer. A three-dimensional fully polarized Monte Carlo model has been used to evaluate the impact of the horizontal finiteness of rain shafts with different rain rates at 10, 19, and 30 GHz. The results show that because of the reduced slant optical thickness in finite clouds, the polarization signal can strongly differ from its one-dimensional counterpart. At the higher frequencies and when the radiometer is positioned underneath the cloud, significantly higher negative values for the polarization are found which are also consistent with some observations. When the observation point is located outside of the precipitating cloud, typical polarization patterns (with troughs and peaks) as a function of the observation angle are predicted. An approximate 1-D slant path radiative transfer model is considered as well and results are compared with the full 3-D simulations to investigate whether or not three-dimensional effects can be explained by geometry effects alone. The study has strong relevance for low-frequency passive microwave polarimetric studies.

  7. Three-dimensional effects in polarization signatures as observed from precipitating clouds by low frequency ground-based microwave radiometers

    NASA Astrophysics Data System (ADS)

    Battaglia, A.; Simmer, C.; Czekala, H.

    2006-06-01

    Consistent negative polarization differences (i.e. differences between the vertical and the horizontal brightness temperature) are observed when looking at precipitating systems by ground-based radiometers at slant angles. These signatures can be partially explained by one-dimensional radiative transfer computations that include oriented non-spherical raindrops. However some cases are characterized by polarization values that exceed differences expected from one-dimensional radiative transfer. A three-dimensional fully polarized Monte Carlo model has been used to evaluate the impact of the horizontal finiteness of rain shafts with different rain rates at 10, 19, and 30 GHz. The results show that because of the reduced slant optical thickness in finite clouds, the polarization signal can strongly differ from its one-dimensional counterpart. At the higher frequencies and when the radiometer is positioned underneath the cloud, significantly higher negative values for the polarization are found which are also consistent with some observations. When the observation point is located outside of the precipitating cloud, typical polarization patterns (with troughs and peaks) as a function of the observation angle are predicted. An approximate 1-D slant path radiative transfer model is considered as well and results are compared with the full 3-D simulations to investigate whether or not three-dimensional effects can be explained by geometry effects alone. The study has strong relevance for low-frequency passive microwave polarimetric studies.

  8. A technique for measuring vertically and horizontally polarized microwave brightness temperatures using electronic polarization-basis rotation

    NASA Technical Reports Server (NTRS)

    Gasiewski, Albin J.

    1992-01-01

    This technique for electronically rotating the polarization basis of an orthogonal-linear polarization radiometer is based on the measurement of the first three feedhorn Stokes parameters, along with the subsequent transformation of this measured Stokes vector into a rotated coordinate frame. The technique requires an accurate measurement of the cross-correlation between the two orthogonal feedhorn modes, for which an innovative polarized calibration load was developed. The experimental portion of this investigation consisted of a proof of concept demonstration of the technique of electronic polarization basis rotation (EPBR) using a ground based 90-GHz dual orthogonal-linear polarization radiometer. Practical calibration algorithms for ground-, aircraft-, and space-based instruments were identified and tested. The theoretical effort consisted of radiative transfer modeling using the planar-stratified numerical model described in Gasiewski and Staelin (1990).

  9. A Methodology for Surface Soil Moisture and Vegetation Optical Depth Retrieval Using the Microwave Polarization Difference Index

    NASA Technical Reports Server (NTRS)

    Owe, Manfred; deJeu, Richard; Walker, Jeffrey; Zukor, Dorothy J. (Technical Monitor)

    2001-01-01

    A methodology for retrieving surface soil moisture and vegetation optical depth from satellite microwave radiometer data is presented. The procedure is tested with historical 6.6 GHz brightness temperature observations from the Scanning Multichannel Microwave Radiometer over several test sites in Illinois. Results using only nighttime data are presented at this time, due to the greater stability of nighttime surface temperature estimation. The methodology uses a radiative transfer model to solve for surface soil moisture and vegetation optical depth simultaneously using a non-linear iterative optimization procedure. It assumes known constant values for the scattering albedo and roughness. Surface temperature is derived by a procedure using high frequency vertically polarized brightness temperatures. The methodology does not require any field observations of soil moisture or canopy biophysical properties for calibration purposes and is totally independent of wavelength. Results compare well with field observations of soil moisture and satellite-derived vegetation index data from optical sensors.

  10. Relative sensitivity of Normalized Difference Vegetation Index (NDVI) and Microwave Polarization Difference Index (MPDI) for vegetation and desertification monitoring

    NASA Technical Reports Server (NTRS)

    Becker, Francois; Choudhury, Bhaskar J.

    1988-01-01

    A simple equation relating the Microwave Polarization Difference Index (MPDI) and the Normalized Difference Vegetation Index (NDVI) is proposed which represents well data obtained from Nimbus 7/SMMR at 37 GHz and NOAA/AVHRR Channels 1 and 2. It is found that there is a limit which is characteristic of a particular type of cover for which both indices are equally sensitive to the variation of vegetation, and below which MPDI is more efficient than NDVI. The results provide insight into the relationship between water content and chlorophyll absorption at pixel size scales.

  11. IMPROVED MEASUREMENTS OF THE TEMPERATURE AND POLARIZATION OF THE COSMIC MICROWAVE BACKGROUND FROM QUaD

    SciTech Connect

    Brown, M. L.; Ade, P.; Bowden, M.; Gear, W. K.; Gupta, S.; Orlando, A.; Bock, J.; Leitch, E.; Cahill, G.; Murphy, J. A.; Castro, P. G.; Memari, Y.; Church, S.; Hinderks, J.; Culverhouse, T.; Friedman, R. B.; Ganga, K.; Melhuish, S. J.

    2009-11-01

    We present an improved analysis of the final data set from the QUaD experiment. Using an improved technique to remove ground contamination, we double the effective sky area and hence increase the precision of our cosmic microwave background (CMB) power spectrum measurements by approx30% versus that previously reported. In addition, we have improved our modeling of the instrument beams and have reduced our absolute calibration uncertainty from 5% to 3.5% in temperature. The robustness of our results is confirmed through extensive jackknife tests, and by way of the agreement that we find between our two fully independent analysis pipelines. For the standard six-parameter LAMBDACDM model, the addition of QUaD data marginally improves the constraints on a number of cosmological parameters over those obtained from the WMAP experiment alone. The impact of QUaD data is significantly greater for a model extended to include either a running in the scalar spectral index, or a possible tensor component, or both. Adding both the QUaD data and the results from the Arcminute Cosmology Bolometer Array Receiver experiment, the uncertainty in the spectral index running is reduced by approx25% compared to WMAP alone, while the upper limit on the tensor-to-scalar ratio is reduced from r < 0.48 to r < 0.33 (95% c.l.). This is the strongest limit on tensors to date from the CMB alone. We also use our polarization measurements to place constraints on parity-violating interactions to the surface of last scattering, constraining the energy scale of Lorentz violating interactions to <1.5 x 10{sup -43} GeV (68% c.l.). Finally, we place a robust upper limit on the strength of the lensing B-mode signal. Assuming a single flat band power between l = 200 and l = 2000, we constrain the amplitude of B-modes to be <0.57 muK{sup 2} (95% c.l.).

  12. Improved Measurements of the Temperature and Polarization of the Cosmic Microwave Background from QUaD

    NASA Astrophysics Data System (ADS)

    Brown, M. L.; Ade, P.; Bock, J.; Bowden, M.; Cahill, G.; Castro, P. G.; Church, S.; Culverhouse, T.; Friedman, R. B.; Ganga, K.; Gear, W. K.; Gupta, S.; Hinderks, J.; Kovac, J.; Lange, A. E.; Leitch, E.; Melhuish, S. J.; Memari, Y.; Murphy, J. A.; Orlando, A.; O'Sullivan, C.; Piccirillo, L.; Pryke, C.; Rajguru, N.; Rusholme, B.; Schwarz, R.; Taylor, A. N.; Thompson, K. L.; Turner, A. H.; Wu, E. Y. S.; Zemcov, M.; QUa D Collaboration

    2009-11-01

    We present an improved analysis of the final data set from the QUaD experiment. Using an improved technique to remove ground contamination, we double the effective sky area and hence increase the precision of our cosmic microwave background (CMB) power spectrum measurements by ~30% versus that previously reported. In addition, we have improved our modeling of the instrument beams and have reduced our absolute calibration uncertainty from 5% to 3.5% in temperature. The robustness of our results is confirmed through extensive jackknife tests, and by way of the agreement that we find between our two fully independent analysis pipelines. For the standard six-parameter ΛCDM model, the addition of QUaD data marginally improves the constraints on a number of cosmological parameters over those obtained from the WMAP experiment alone. The impact of QUaD data is significantly greater for a model extended to include either a running in the scalar spectral index, or a possible tensor component, or both. Adding both the QUaD data and the results from the Arcminute Cosmology Bolometer Array Receiver experiment, the uncertainty in the spectral index running is reduced by ~25% compared to WMAP alone, while the upper limit on the tensor-to-scalar ratio is reduced from r < 0.48 to r < 0.33 (95% c.l.). This is the strongest limit on tensors to date from the CMB alone. We also use our polarization measurements to place constraints on parity-violating interactions to the surface of last scattering, constraining the energy scale of Lorentz violating interactions to <1.5 × 10-43 GeV (68% c.l.). Finally, we place a robust upper limit on the strength of the lensing B-mode signal. Assuming a single flat band power between ell = 200 and ell = 2000, we constrain the amplitude of B-modes to be <0.57 μK2 (95% c.l.).

  13. Front-End Electronics for the Array Readout of a Microwave Kinetic Inductance Detector Towards Observation of Cosmic Microwave Background Polarization

    NASA Astrophysics Data System (ADS)

    Ishitsuka, H.; Ikeno, M.; Oguri, S.; Tajima, O.; Tomita, N.; Uchida, T.

    2016-07-01

    Precise measurements of polarization patterns in cosmic microwave background (CMB) provide deep knowledge about the begin of the Universe. The GroundBIRD experiment aims to measure the CMB polarization by using microwave kinetic inductance detector (MKID) arrays. The MKID is suited to multiplexing. One of our requirements is a MUX factor (the number of readout channels for a single wire pair) of at least 100. If we make frequency combs of the MKIDs with 2-MHz spacing, a bandwidth of 200 MHz satisfies 100 MUX. The analog electronics must consist of an analog-to-digital converter (ADC), digital-to-analog converter (DAC), and local oscillator. We developed our own analog electronics board " RHEA." Two outputs/inputs of DAC/ADC with a 200-MHz clock provide an effective bandwidth of 200 MHz. The RHEA allows us to measure both the amplitude and phase responses of each MKID simultaneously. These data are continuously sampled at a high rate (e.g., 1 kSPS) and with no dead time. We achieved 12 and 14 bits resolution for ADC and DAC, respectively. This corresponds to achieve that our electronics achieved low noise: 1/1000 compared with the detector noise. We also achieved low power consumption compared with that of other electronics development for other experiments. Another important feature is that the board is completely separated from the digital part. Each user can choose their preferred field-programmable array. With the combination of the Kintex-7 evaluation kit from Xilinx, we demonstrated readout of MKID response.

  14. Front-End Electronics for the Array Readout of a Microwave Kinetic Inductance Detector Towards Observation of Cosmic Microwave Background Polarization

    NASA Astrophysics Data System (ADS)

    Ishitsuka, H.; Ikeno, M.; Oguri, S.; Tajima, O.; Tomita, N.; Uchida, T.

    2016-01-01

    Precise measurements of polarization patterns in cosmic microwave background (CMB) provide deep knowledge about the begin of the Universe. The GroundBIRD experiment aims to measure the CMB polarization by using microwave kinetic inductance detector (MKID) arrays. The MKID is suited to multiplexing. One of our requirements is a MUX factor (the number of readout channels for a single wire pair) of at least 100. If we make frequency combs of the MKIDs with 2-MHz spacing, a bandwidth of 200 MHz satisfies 100 MUX. The analog electronics must consist of an analog-to-digital converter (ADC), digital-to-analog converter (DAC), and local oscillator. We developed our own analog electronics board "RHEA." Two outputs/inputs of DAC/ADC with a 200-MHz clock provide an effective bandwidth of 200 MHz. The RHEA allows us to measure both the amplitude and phase responses of each MKID simultaneously. These data are continuously sampled at a high rate (e.g., 1 kSPS) and with no dead time. We achieved 12 and 14 bits resolution for ADC and DAC, respectively. This corresponds to achieve that our electronics achieved low noise: 1/1000 compared with the detector noise. We also achieved low power consumption compared with that of other electronics development for other experiments. Another important feature is that the board is completely separated from the digital part. Each user can choose their preferred field-programmable array. With the combination of the Kintex-7 evaluation kit from Xilinx, we demonstrated readout of MKID response.

  15. Assessing the impact of satellite-based observations in sea surface temperature trends

    NASA Astrophysics Data System (ADS)

    Huang, Boyin; Liu, Chunying; Banzon, Viva F.; Zhang, Huai-Min; Karl, Thomas R.; Lawrimore, Jay H.; Vose, Russell S.

    2016-04-01

    Global trends of sea surface temperature (SST) are assessed for the existing and new experimental SST analyses that incorporate advanced very high resolution radiometer (AVHRR) observations from NOAA polar-orbiting satellites. These analyses show that globally and annually averaged SST trends over the 21st century (2000-2015) are similar to the trends for the full satellite record period (1982-2015), regardless of whether AVHRR data are included in the analyses. It is shown that appropriate bias correction is an important step to remove discontinuities of AVHRR data for consistent time series and trend analysis.

  16. ENSO signature in the SMOS sea surface salinity maps

    NASA Astrophysics Data System (ADS)

    Ballabrera, J.; Umbert, M.; Hoareau, N.; Turiel, A.; Font, J.

    2012-12-01

    Until recently, the role of salinity observations in the operational simulation and prediction of ENSO was neglected because of the historical lack of observations and because leading intermediate coupled models had significant predictive skill without directly accounting for salinity effects. In Ballabrera-Poy et al., (2002), the potential role of sea surface salinity (SSS) observations on the statistical predictions of ENSO was investigated. It was shown that, although SSS observations would play little role in statistical nowcasts of ENSO, they would provide a significant role in the 6-12 month predictions. The European Space Agency (ESA) Soil Moisture and Ocean Salinity (SMOS) Earth Explorer opportunity mission was launched on November 2, 2009, becoming the first satellite mission addressing the challenge of measuring SSS from space with the help of MIRAS (Microwave Imaging Radiometer with Aperture Synthesis), a novel two-dimensional interferometer operating at L-band (1.4 GHz). Although the L-band frequency is the optimal for ocean salinity measurements, the retrieval of SSS information requires special care because of the low sensitivity of the brightness temperature to SSS: from 0.2-0.8 K per salinity unit. Maps of 10-day averages of SSS in 1x1 degree boxes are distributed by the SMOS Barcelona Expert Centre on Radiometric Calibration and Ocean Salinity (SMOS-BEC, http://www.smos-bec.icm.csic.es). These maps are derived from the SMOS reprocessing campaign released to the SMOS user community in March 2011, and span the period from January 2010 through December 2011. The current accuracy of these SSS maps ranges from 0.2-0.4, depending on the ocean region being considered (Umbert et al., 2012). During the period of the reprocessing campaign, the equatorial Pacific has been in a quasi-continuous La Niña state. During the cold phases of ENSO, positive anomalies of SSS are expected with a largest anomalous values in the western warm-fresh pool. The anomalies

  17. Integrative algorithm of determining ice conditions in Polar Regions by data of satellite microwave radiometry (VASIA2)

    NASA Astrophysics Data System (ADS)

    Tikhonov, V. V.; Repina, I. A.; Raev, M. D.; Sharkov, E. A.; Boyarskii, D. A.; Komarova, N. Yu.

    2015-12-01

    In this paper, a new algorithm for determining the concentration of the ice cover in Polar Regions by data of satellite microwave radiometry is considered. The technique of its construction is described in detail; it cardinally differs from the technique of creating present-day algorithms. The new algorithm demonstrates good results in determining the concentration of the ice cover in Polar Regions. The algorithm permits one not only to obtain maps of ice concentration, but also to determine areas of puddles covering the ice-cover surface in summer months. The algorithm is easy-to-use and requires no additional or fitting parameters. At the end of the work, advantages and disadvantages of the new algorithm are discussed.

  18. The effects of the variations in sea surface temperature and atmospheric stability in the estimation of average wind speed by SEASAT-SASS

    NASA Technical Reports Server (NTRS)

    Liu, W. T.

    1984-01-01

    The average wind speeds from the scatterometer (SASS) on the ocean observing satellite SEASAT are found to be generally higher than the average wind speeds from ship reports. In this study, two factors, sea surface temperature and atmospheric stability, are identified which affect microwave scatter and, therefore, wave development. The problem of relating satellite observations to a fictitious quantity, such as the neutral wind, that has to be derived from in situ observations with models is examined. The study also demonstrates the dependence of SASS winds on sea surface temperature at low wind speeds, possibly due to temperature-dependent factors, such as water viscosity, which affect wave development.

  19. Polar microwave brightness temperatures from Nimbus-7 SMMR: Time series of daily and monthly maps from 1978 to 1987

    NASA Technical Reports Server (NTRS)

    Comiso, Josefino C.; Zwally, H. Jay

    1989-01-01

    A time series of daily brightness temperature gridded maps (October 25, 1978 through August 15, 1987) were generated from all ten channels of the Nimbus-7 Scanning Multichannel Microwave Radiometer orbital data. This unique data set can be utilized in a wide range of applications including heat flux, ocean circulation, ice edge productivity, and climate studies. Two sets of data in polar stereographic format are created for the Arctic region: one with a grid size of about 30 km on a 293 by 293 array similar to that previously utilized for the Nimbus-5 Electrically Scanning Microwave Radiometer, while the other has a grid size of about 25 km on a 448 by 304 array identical to what is now being used for the DMSP Scanning Multichannel Microwave Imager. Data generated for the Antaractic region are mapped using the 293 by 293 grid only. The general technique for mapping, and a quality assessment of the data set are presented. Monthly and yearly averages are also generated from the daily data and sample geophysical ice images and products derived from the data are given. Contour plots of monthly ice concentrations derived from the data for October 1978 through August 1987 are presented to demonstrate spatial and temporal detail which this data set can offer, and to show potential research applications.

  20. Sea Surface Temperature from EUMETSAT Including Sentinel-3 SLSTR

    NASA Astrophysics Data System (ADS)

    O'Carroll, Anne; Bonekamp, Hans; Montagner, Francois; Santacesaria, Vincenzo; Tomazic, Igor

    2015-12-01

    The paper gives an overview of sea surface temperature (SST) activities at EUMETSAT including information on SST planned from the Sea and Land Surface Temperature Radiometer (SLSTR). Operational oceanography activities within the Marine Applications group at EUMETSAT continue with a focus on SST, sea surface winds, sea-ice products, radiative fluxes, significant wave height and sea surface topography. These are achieved through the mandatory, optional and third-party programmes, and for some products with the EUMETSAT Ocean and Sea-Ice Satellite Application Facility (OSI SAF). Progress towards products from sea-ice surface temperature, ocean colour products, turbidity and aerosol optical depth over water continue. Information on oceanography products from EUMETSAT can be found through the product navigator (http://navigator.eumetsat.int). EUMETSAT have been collaborating with ESA for a number of years on the development of SST for SLSTR.

  1. A measurement of the cosmic microwave background B-mode polarization power spectrum at sub-degree scales with POLARBEAR

    SciTech Connect

    Ade, P. A. R.; Akiba, Y.; Hasegawa, M.; Anthony, A. E.; Halverson, N. W.; Arnold, K.; Atlas, M.; Barron, D.; Boettger, D.; Elleflot, T.; Feng, C.; Borrill, J.; Errard, J.; Chapman, S.; Chinone, Y.; Flanigan, D.; Dobbs, M.; Gilbert, A.; Fabbian, G.; Collaboration: Polarbear Collaboration; and others

    2014-10-20

    We report a measurement of the B-mode polarization power spectrum in the cosmic microwave background (CMB) using the POLARBEAR experiment in Chile. The faint B-mode polarization signature carries information about the universe's entire history of gravitational structure formation, and the cosmic inflation that may have occurred in the very early universe. Our measurement covers the angular multipole range 500 < ℓ < 2100 and is based on observations of an effective sky area of 25 deg{sup 2} with 3.'5 resolution at 150 GHz. On these angular scales, gravitational lensing of the CMB by intervening structure in the universe is expected to be the dominant source of B-mode polarization. Including both systematic and statistical uncertainties, the hypothesis of no B-mode polarization power from gravitational lensing is rejected at 97.2% confidence. The band powers are consistent with the standard cosmological model. Fitting a single lensing amplitude parameter A{sub BB} to the measured band powers, A{sub BB}=1.12±0.61(stat){sub −0.12}{sup +0.04}(sys)±0.07(multi), where A{sub BB} = 1 is the fiducial WMAP-9 ΛCDM value. In this expression, 'stat' refers to the statistical uncertainty, 'sys' to the systematic uncertainty associated with possible biases from the instrument and astrophysical foregrounds, and 'multi' to the calibration uncertainties that have a multiplicative effect on the measured amplitude A{sub BB}.

  2. A Measurement of the Cosmic Microwave Background B-mode Polarization Power Spectrum at Sub-degree Scales with POLARBEAR

    NASA Astrophysics Data System (ADS)

    The Polarbear Collaboration: P. A. R. Ade; Akiba, Y.; Anthony, A. E.; Arnold, K.; Atlas, M.; Barron, D.; Boettger, D.; Borrill, J.; Chapman, S.; Chinone, Y.; Dobbs, M.; Elleflot, T.; Errard, J.; Fabbian, G.; Feng, C.; Flanigan, D.; Gilbert, A.; Grainger, W.; Halverson, N. W.; Hasegawa, M.; Hattori, K.; Hazumi, M.; Holzapfel, W. L.; Hori, Y.; Howard, J.; Hyland, P.; Inoue, Y.; Jaehnig, G. C.; Jaffe, A. H.; Keating, B.; Kermish, Z.; Keskitalo, R.; Kisner, T.; Le Jeune, M.; Lee, A. T.; Leitch, E. M.; Linder, E.; Lungu, M.; Matsuda, F.; Matsumura, T.; Meng, X.; Miller, N. J.; Morii, H.; Moyerman, S.; Myers, M. J.; Navaroli, M.; Nishino, H.; Orlando, A.; Paar, H.; Peloton, J.; Poletti, D.; Quealy, E.; Rebeiz, G.; Reichardt, C. L.; Richards, P. L.; Ross, C.; Schanning, I.; Schenck, D. E.; Sherwin, B. D.; Shimizu, A.; Shimmin, C.; Shimon, M.; Siritanasak, P.; Smecher, G.; Spieler, H.; Stebor, N.; Steinbach, B.; Stompor, R.; Suzuki, A.; Takakura, S.; Tomaru, T.; Wilson, B.; Yadav, A.; Zahn, O.

    2014-10-01

    We report a measurement of the B-mode polarization power spectrum in the cosmic microwave background (CMB) using the POLARBEAR experiment in Chile. The faint B-mode polarization signature carries information about the universe's entire history of gravitational structure formation, and the cosmic inflation that may have occurred in the very early universe. Our measurement covers the angular multipole range 500 < l < 2100 and is based on observations of an effective sky area of 25 \\deg ^2 with 3.'5 resolution at 150 GHz. On these angular scales, gravitational lensing of the CMB by intervening structure in the universe is expected to be the dominant source of B-mode polarization. Including both systematic and statistical uncertainties, the hypothesis of no B-mode polarization power from gravitational lensing is rejected at 97.2% confidence. The band powers are consistent with the standard cosmological model. Fitting a single lensing amplitude parameter ABB to the measured band powers, ABB = 1.12 +/- 0.61 (stat) +0.04-0.12(sys) +/- 0.07 (multi), where ABB = 1 is the fiducial WMAP-9 ΛCDM value. In this expression, "stat" refers to the statistical uncertainty, "sys" to the systematic uncertainty associated with possible biases from the instrument and astrophysical foregrounds, and "multi" to the calibration uncertainties that have a multiplicative effect on the measured amplitude ABB .

  3. A Texture-Polarization Method for Estimating Convective/Stratiform Precipitation Area Coverage from Passive Microwave Radiometer Data

    NASA Technical Reports Server (NTRS)

    Olson, William S.; Hong, Ye; Kummerow, Christian D.; Turk, Joseph; Einaudi, Franco (Technical Monitor)

    2000-01-01

    Observational and modeling studies have described the relationships between convective/stratiform rain proportion and the vertical distributions of vertical motion, latent heating, and moistening in mesoscale convective systems. Therefore, remote sensing techniques which can quantify the relative areal proportion of convective and stratiform, rainfall can provide useful information regarding the dynamic and thermodynamic processes in these systems. In the present study, two methods for deducing the convective/stratiform areal extent of precipitation from satellite passive microwave radiometer measurements are combined to yield an improved method. If sufficient microwave scattering by ice-phase precipitating hydrometeors is detected, the method relies mainly on the degree of polarization in oblique-view, 85.5 GHz radiances to estimate the area fraction of convective rain within the radiometer footprint. In situations where ice scattering is minimal, the method draws mostly on texture information in radiometer imagery at lower microwave frequencies to estimate the convective area fraction. Based upon observations of ten convective systems over ocean and nine systems over land, instantaneous 0.5 degree resolution estimates of convective area fraction from the Tropical Rainfall Measuring Mission Microwave Imager (TRMM TMI) are compared to nearly coincident estimates from the TRMM Precipitation Radar (TRMM PR). The TMI convective area fraction estimates are slightly low-biased with respect to the PR, with TMI-PR correlations of 0.78 and 0.84 over ocean and land backgrounds, respectively. TMI monthly-average convective area percentages in the tropics and subtropics from February 1998 exhibit the greatest values along the ITCZ and in continental regions of the summer (southern) hemisphere. Although convective area percentages. from the TMI are systematically lower than those from the PR, monthly rain patterns derived from the TMI and PR rain algorithms are very similar

  4. Sea surface temperature of the coastal zones of France

    NASA Technical Reports Server (NTRS)

    Deschamps, P. Y.; Crepon, M.; Monget, J. M.; Verger, F. (Principal Investigator); Frouin, R.; Cassanet, J.; Wald, L.

    1982-01-01

    Thermal gradients in French coastal zones for the period of one year were mapped in order to enable a coherent study of certain oceanic features detectable by the variations in the sea surface temperature field and their evolution in time. The phenomena examined were mesoscale thermal features in the English Channel, the Bay of Biscay, and the northwestern Mediterranean; thermal gradients generated by French estuary systems; and diurnal heating in the sea surface layer. The investigation was based on Heat Capacity Mapping Mission imagery.

  5. Influence of polarity on the scalability and reproducibility of solvent-free microwave-assisted reactions.

    PubMed

    Díaz-Ortiz, Angel; de la Hoz, Antonio; Alcázar, Jesús; Carrillo, José R; Herrero, María A; Fontana, Alberto; Muñoz, Juan de M; Prieto, Pilar; de Cózar, Abel

    2011-02-01

    Organic reactions performed in the absence of solvent in domestic ovens without appropriate temperature control are generally considered as not reproducible, particularly when different instruments are used. For this reason, reproducibility has historically been one of the major issues associated with Microwave-Assisted Organic Synthesis (MAOS) especially when domestic ovens are involved. The lack of reproducibility limits the general applicability and the scale up of these reactions. In this work several solvent-free reactions previously carried out in domestic ovens have been translated into a single-mode microwave reactor and then scaled up in a multimode oven. The results show that most of these reactions, although not considered as reproducible, can be easily updated and applied in microwave reactors using temperature-controlled conditions. Furthermore, computational calculations can assist to explain and/or predict whether a reaction will be reproducible or not. PMID:21143180

  6. The clear-sky greenhouse effect sensitivity to a sea surface temperature change

    NASA Technical Reports Server (NTRS)

    Duvel, J. PH.; Breon, F. M.

    1991-01-01

    The clear-sky greenhouse effect response to a sea surface temperature (SST or Ts) change is studied using outgoing clear-sky longwave radiation measurements from the Earth Radiation Budget Experiment. Considering geographical distributions for July 1987, the relation between the SST, the greenhouse effect (defined as the outgoing infrared flux trapped by atmospheric gases), and the precipitable water vapor content (W), estimated by the Special Sensor Microwave Imager, is analyzed first. A fairly linear relation between W and the normalized greenhouse effect g, is found. On the contrary, the SST dependence of both W and g exhibits nonlinearities with, especially, a large increase for SST above 25 C. This enhanced sensitivity of g and W can be interpreted in part by a corresponding large increase of atmospheric water vapor content related to the transition from subtropical dry regions to equatorial moist regions. Using two years of data (1985 and 1986), the normalized greenhouse effect sensitivity to the sea surface temperature is computed from the interannual variation of monthly mean values.

  7. Sea surface Ka-band radar cross-section from field observations in the Black Sea

    NASA Astrophysics Data System (ADS)

    Yurovsky, Yury; Kudryavtsev, Vladimir; Grodsky, Semyon; Chapron, Bertrand

    2016-04-01

    An interest in Ka-band radar backscattering from the ocean surface is growing due to better spatial resolution and more accurate Doppler anomaly estimate. But, available empirical models of Ka-band cross-section are quite scarce and sometime controversial. Here we present multi-year (2009-2015) field measurements of Ka-band co-polarized (VV and HH) sea surface normalized radar cross-section (NRCS) from research platform in the Black sea collected in a wide range of observation and sea state conditions. The data are fitted by polynomial function of incidence angle, azimuth and wind speed with accounting for measured radar antenna pattern. This empirical NRCS is compared with published Ka- and Ku-band data. Our Ka-band NRCS is close to Ku-band, but is 5-7 dB higher than 'pioneer' measurements by Masuko et al. (1986). Following the two-scale Bragg paradigm, the NRCS is split into polarized (Bragg) and non-polarized components and analyzed in terms of polarization ratio (VV/HH) and polarization difference (VV-HH) to estimate wave spectra at the Bragg wave number. Non-polarized component dominates at low incidence angles <30° due to specular reflection from regular surface. At larger incidence angles, the relative non-polarized contribution decreases, but grows again at HH-polarization approaching 0.7-0.8 at 65° for 10 m/s wind speed, suggesting that backscattering from breaking waves dominates HH NRCS at low grazing angles. At high incidence angles (>60°) NRCS azimuth dependency is unimodal (upwind peak) for HH and bimodal (with up- and downwind peaks) for VV polarization. This again can be attributed to different backscattering mechanisms for VV and HH polarizations. With decreasing of incidence angle, up- to downwind ratio tends to 1, and under light wind conditions (4-6 m/s) can be less than 1. The same situation is observed for polarization difference, which reflects Bragg backscattering properties only. This effect can be explained by enhanced roughness on

  8. Polar low monitoring

    NASA Astrophysics Data System (ADS)

    Bobylev, Leonid; Zabolotskikh, Elizaveta; Mitnik, Leonid

    2010-05-01

    passive microwave data make it possible to retrieve several important atmospheric and oceanic parameters inside the polar lows, such as sea surface wind speed, water vapour content in the atmosphere, total liquid water content in the clouds and others, providing not only qualitative image of a vortex, but also quantitative information about these severe events, constituting a promising tool for their study and monitoring. An approach for detection and tracking of polar lows is developed utilizing the data from two sensors: SSM/I onboard DMSP and Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) onboard Aqua satellite. This approach consists of two stages. At the first stage total atmospheric water vapor fields are retrieved from SSM/I and AMSRE-E measurement data using precise Arctic polar algorithms, developed at NIERSC. These algorithms are applicable over open water. They have high retrieval accuracies under a wide range of environmental conditions. Algorithms are based on numerical simulation of brightness temperatures and their inversion by means of Neural Networks. At the second stage the vortex structures are detected in these fields, polar lows are identified and tracked and some of their parameters are calculated. A few case studies are comprehensively conducted based on SSM/I and AMSRE-E measurements and using other satellite data including visible, infrared and SAR images, QuickScat Scatterometer wind fields, surface analysis maps and re-analysis data, which demonstrated the advantages of satellite passive microwave data usage in the polar low studies.

  9. Leveraging microwave polarization information for calibration of a land data assimilation system

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This letter contributes a new approach to calibrating a tau-omega radiative transfer model coupled to a land surface model with low frequency (< 10 GHz) microwave brightness temperature (TB) observations. The problem of calibrating this system is generally poorlyposed because various parameter combi...

  10. Sea Surface Salinity: The Next Remote Sensing Challenge

    NASA Technical Reports Server (NTRS)

    Lagerloef, Gary S. E.; Swift, Calvin T.; LeVine, David M.

    1995-01-01

    A brief history of salinity remote sensing is presented. The role of sea surface salinity (SSS) in the far north Atlantic and the influence of salinity variations on upper ocean dynamics in the tropics are described. An assessment of the present state of the technology of the SSS satellite remote sensing is given.

  11. Radar Backscatter Across the Gulf Stream Sea Surface Temperature Front

    NASA Technical Reports Server (NTRS)

    Nghiem, S. V.; Li, F. K.; Walsh, E. J.; Lou, S. H.

    1998-01-01

    Ocean backscatter signatures were measured by the Jet Propulsion Laboratory airborne NUSCAT K(sub u)-band scatterometer across the Gulf Stream sea surface temperature front. The measurements were made during the Surface Wave Dynamics Experiment (SWADE) off the coast of Virginia and Maryland in the winter of 1991.

  12. Long-term changes in sea surface temperatures

    SciTech Connect

    Parker, D.E.

    1994-12-31

    Historical observations of sea surface temperature since 1856 have been improved by applying corrections to compensate for the predominant use of uninsulated or partly insulated buckets until the Second World War. There are large gaps in coverage in the late nineteenth century and around the two world wars, but a range of statistical techniques suggest that these gaps do not severely prejudice estimates of global and regional climatic change. Nonetheless, to improve the analysis on smaller scales, many unused historical data are to be digitized and incorporated. For recent years, satellite-based sea surface temperatures have improved the coverage, after adjustments for their biases relative to in situ data. An initial version of a nominally globally complete sea ice and interpolated sea surface temperature data set, beginning in 1871, has been created for use in numerical simulations of recent climate. Long time series of corrected regional, hemispheric, and global sea surface temperatures are mostly consistent with corresponding night marine air temperature series, and confirm the regionally specific climatic changes portrayed in the Scientific Assessments of the intergovernmental Panel on Climate Change. The observations also show an El Nino-like oscillation on bidecadal and longer time scales.

  13. Calving seismicity from iceberg-sea surface interactions

    USGS Publications Warehouse

    Bartholomaus, T.C.; Larsen, C.F.; O'Neel, S.; West, M.E.

    2012-01-01

    Iceberg calving is known to release substantial seismic energy, but little is known about the specific mechanisms that produce calving icequakes. At Yahtse Glacier, a tidewater glacier on the Gulf of Alaska, we draw upon a local network of seismometers and focus on 80 hours of concurrent, direct observation of the terminus to show that calving is the dominant source of seismicity. To elucidate seismogenic mechanisms, we synchronized video and seismograms to reveal that the majority of seismic energy is produced during iceberg interactions with the sea surface. Icequake peak amplitudes coincide with the emergence of high velocity jets of water and ice from the fjord after the complete submergence of falling icebergs below sea level. These icequakes have dominant frequencies between 1 and 3 Hz. Detachment of an iceberg from the terminus produces comparatively weak seismic waves at frequencies between 5 and 20 Hz. Our observations allow us to suggest that the most powerful sources of calving icequakes at Yahtse Glacier include iceberg-sea surface impact, deceleration under the influence of drag and buoyancy, and cavitation. Numerical simulations of seismogenesis during iceberg-sea surface interactions support our observational evidence. Our new understanding of iceberg-sea surface interactions allows us to reattribute the sources of calving seismicity identified in earlier studies and offer guidance for the future use of seismology in monitoring iceberg calving.

  14. Three-way partitioning of sea surface temperature measurement error

    NASA Technical Reports Server (NTRS)

    Chelton, D.

    1983-01-01

    Given any set of three 2 degree binned anomaly sea surface temperature (SST) data sets by three different sensors, estimates of the mean square error of each sensor estimate is made. The above formalism performed on every possible triplet of sensors. A separate table of error estimates is then constructed for each sensor.

  15. Airborne full polarization radiometry using the MSFC Advanced Microwave Precipitation Radiometer (AMPR)

    NASA Technical Reports Server (NTRS)

    Gasiewski, Al J.; Kunkee, D. B.

    1993-01-01

    The applications of vertically and horizontally polarized brightness temperatures in both atmospheric and surface remote sensing have been long recognized by many investigators, particularly those studying SMMR and SSM/I data. Here, the large contrast between the first two Stokes' parameters (T(sub V) and T(sub H)) can be used for detection of sea ice, measurement of ocean surface wind speed, and measurement of cloud and water vapor opacity. High-resolution aircraft data from instruments such as the NASA/MSFC AMPR is crucial for verifying radiative transfer models and developing retrieval algorithms. Currently, the AMPR is outfitted with single-polarization channels at 10, 18, 37 and 85 GHz. To increase its utility, it is proposed that additional orthogonal linearly polarized channels be added to the AMPR. Since the AMPR's feedhorns are already configured for dual orthogonal linearly polarized modes, this would require only a duplication of the currently existing receivers. To circumvent the resulting polarization basis skew caused by the cross-track scanning mechanism, the technique of Electronic Polarization Basis Rotation is proposed to be implemented. Implementation of EPBR requires precise measurement of the third Stokes parameter and will eliminate polarization skew by allowing the feedhorn basis skew angle to be corrected in software. In addition to upgrading AMPR to dual polarization capability (without skew), the modifications will provide an opportunity to demonstrate EPBR on an airborne platform. This is a highly desirable intermediate step prior to satellite implementation.

  16. High Galactic latitude polarized emission at 1.4 GHz and implications for cosmic microwave background observations

    NASA Astrophysics Data System (ADS)

    Carretti, E.; Bernardi, G.; Sault, R. J.; Cortiglioni, S.; Poppi, S.

    2005-03-01

    We analyse the polarized emission at 1.4 GHz in a 3°× 3° area at high Galactic latitude (b~-40°). The region, centred in (α= 5h, δ=-49°), was observed with the Australia Telescope Compact Array (ATCA) radio-interferometer, whose 3-30 arcmin angular sensitivity range allows the study of scales appropriate for cosmic microwave background polarization (CMBP) investigations. The angular behaviour of the diffuse emission is analysed through the E- and B-mode angular power spectra. These follow a power law CXl~lβX with slopes βE=-1.97 +/- 0.08 and βB=-1.98 +/- 0.07. The emission is found to be approximately a factor 25 fainter than in Galactic plane regions. The comparison of the power spectra with other surveys indicates that this area is intermediate between strong and negligible Faraday rotation effects. A similar conclusion can be reached by analysing both the frequency and Galactic latitude behaviours of the diffuse Galactic emission of the 408-1411 MHz Leiden survey data. We present an analysis of the Faraday rotation effects on the polarized power spectra and find that the observed power spectra can be enhanced by a transfer of power from large to small angular scales. The extrapolation of the spectra to 32 and 90 GHz of the cosmic microwave background (CMB) window suggests that Galactic synchrotron emission leaves the CMBP E-mode uncontaminated at 32 GHz. The level of the contamination at 90 GHz is expected to be more than 4 orders of magnitude below the CMBP spectrum. Extrapolating to the relevant angular scales, this region also appears adequate for investigation of the CMBP B-modes for models with tensor-to-scalar fluctuation power ratio T/S > 0.01. We also identify polarized point sources in the field, providing a nine object list, which is complete down to the polarized flux limit of Splim= 2 mJy.

  17. Earth System Science at NASA: Teleconnections Between Sea Surface Temperature and Epidemics in Africa

    NASA Technical Reports Server (NTRS)

    Meeson, Blanche W.

    2000-01-01

    The research carried out in the Earth Sciences in NASA and at NASA's Goddard Space Flight Center will be the focus of the presentations. In addition, one research project that links sea surface temperature to epidemics in Africa will be highlighted. At GSFC research interests span the full breath of disciplines in Earth Science. Branches and research groups focus on areas as diverse as planetary geomagnetics and atmospheric chemistry. These organizations focus on atmospheric sciences (atmospheric chemistry, climate and radiation, regional processes, atmospheric modeling), hydrological sciences (snow, ice, oceans, and seasonal-to-interannual prediction), terrestrial physics (geology, terrestrial biology, land-atmosphere interactions, geophysics), climate modeling (global warming, greenhouse gases, climate change), on sensor development especially using lidar and microwave technologies, and on information technologies, that enable support of scientific and technical research.

  18. Photonic generation of widely tunable phase-coded microwave signals based on a dual-parallel polarization modulator.

    PubMed

    Liu, Shifeng; Zhu, Dan; Wei, Zhengwu; Pan, Shilong

    2014-07-01

    A photonic approach for the generation of a widely tunable arbitrarily phase-coded microwave signal based on a dual-parallel polarization modulator (DP-PolM) is proposed and demonstrated without using any optical or electrical filter. Two orthogonally polarized ± first-order optical sidebands with suppressed carrier are generated based on the DP-PolM, and their polarization directions are aligned with the two principal axes of the following PolM. Phase coding is implemented at a following PolM driven by an electrical coding signal. The inherent frequency-doubling operation can make the system work at a frequency beyond the operation bandwidth of the DP-PolM and the 90° hybrid. Because no optical or electrical filter is applied, good frequency tunability is realized. An experiment is performed. The generation of phase-coded signals tuning from 10 to 40 GHz with up to 10  Gbit/s coding rates is verified. PMID:24978781

  19. Microwave polarization angle study of the radiation-induced magnetoresistance oscillations in the GaAs/AlGaAs 2D electron system under dc current bias

    NASA Astrophysics Data System (ADS)

    Iqbal, Muhammad-Zahir; Liu, Han-Chun; Heimbeck, Martin S.; Everitt, Henry O.; Wegscheider, Werner; Mani, Ramesh G.

    Microwave-induced magnetoresistance oscillations followed by the vanishing resistance states are a prime representation of non-equilibrium transport phenomena in two-dimensional electron systems (2DES). The effect of a dc current bias on the nonlinear response of 2DES with microwave polarization angle under magnetic field is a subject of interest. Here, we have studied the effect of various dc current bias on microwave radiation-induced magnetoresistance oscillations in a high mobility 2DES. Further, we systematically investigate the effect of the microwave polarization angle on the magneto-resistance oscillations at two different frequencies 152.78 GHz and 185.76 GHz. This study aims to better understand the effects of both dc current and microwave polarization angle in the GaAs/AlGaAs system, both of which modify the observed magneto-transport properties DOE-BES, Mat'l. Sci. & Eng. Div., DE-SC0001762; ARO W911NF-14-2-0076; ARO W911NF-15-1-0433.

  20. Crop moisture estimation over the southern Great Plains with dual polarization 1.66 centimeter passive microwave data from Nimbus 7

    NASA Technical Reports Server (NTRS)

    Mcfarland, M. J.; Harder, P. H., II; Wilke, G. D.; Huebner, G. L., Jr.

    1984-01-01

    Moisture content of snow-free, unfrozen soil is inferred using passive microwave brightness temperatures from the scanning multichannel microwave radiometer (SMMR) on Nimbus-7. Investigation is restricted to the two polarizations of the 1.66 cm wavelength sensor. Passive microwave estimates of soil moisture are of two basic categories; those based upon soil emissivity and those based upon the polarization of soil emission. The two methods are compared and contrasted through the investigation of 54 potential functions of polarized brightness temperatures and, in some cases, ground-based temperature measurements. Of these indices, three are selected for the estimated emissivity, the difference between polarized brightness temperatures, and the normalized polarization difference. Each of these indices is about equally effective for monitoring soil moisture. Using an antecedent precipitation index (API) as ground control data, temporal and spatial analyses show that emissivity data consistently give slightly better soil moisture estimates than depolarization data. The difference, however, is not statistically significant. It is concluded that polarization data alone can provide estimates of soil moisture in areas where the emissivity cannot be inferred due to nonavailability of surface temperature data.

  1. LETHALITY IN MICE AND RATS EXPOSED TO 2450 MHZ CIRCULARLY POLARIZED MICROWAVES AS A FUNCTION OF EXPOSURE DURATION AND ENVIRONMENTAL FACTORS

    EPA Science Inventory

    Adult male CD-1 mice and CD rats were used to determine LD50/24 hr of lethality from exposure to 2450-MHz circularly-polarized microwaves. Groups of sixteen mice or six rats were exposed in each of 32 combinations of nominal power density (10, 25, 50 or 75 mW/sq. cm.), exposure d...

  2. New Constraints on Cosmic Polarization Rotation from the ACTPol Cosmic Microwave Background B-mode Polarization Observation and the BICEP2 Constraint Update

    NASA Astrophysics Data System (ADS)

    Mei, Hsien-Hao; Ni, Wei-Tou; Pan, Wei-Ping; Xu, Lixin; di Serego Alighieri, Sperello

    2015-06-01

    Recently, ACTPol measured the cosmic microwave background (CMB) B-mode and E-mode polarizations and obtained TE, EE, BB, TB, and EB power spectra in the multipole range 225-8725. In our previous paper (Paper I), we jointly analyzed the results of three experiments on the CMB B-mode polarization—SPTpol, POLARBEAR, and BICEP2—to include in the model, in addition to the gravitational lensing and inflationary gravitational waves components, the fluctuation effects induced by cosmic polarization rotation (CPR) if it exists within the upper limits at the time. In this paper, we fit both the mean CPR angle < α > and its fluctuation < δ {{α }2}> from the new ACTPol data, and update our fitting of CPR fluctuations using the BICEP2 data taking the new Planck dust measurement results into consideration. We follow the same method used in Paper I. The mean CPR angle is constrained from the EB correlation power spectra to |< α > |\\lt 14 mrad (0.°8) and the fluctuation (rms) is constrained from the BB correlation power spectra to {{< δ {{α }2}> }1/2}\\lt 29.3 mrad (1.°68). Assuming that the polarization angle of Tau A does not change from 89.2 to 146 GHz, the ACTPol data give < α > =1.0+/- 0\\buildrel{\\circ}\\over{.} 63. These results suggest that the inclusion of the present ACTPol data is consistent with no CPR detection. Using the new Planck dust measurement, we update our fits of the BICEP2 CPR fluctuation constraint to be 32.8 mrad (1.°88). The joint ACTPol-BICEP2-POLARBEAR CPR fluctuation constraint is 23.7 mrad (1.°36).

  3. New Constraints on Cosmic Polarization Rotation from the ACTPol Cosmic Microwave Background B-mode Polarization Observation and the BICEP2 Constraint Update

    NASA Astrophysics Data System (ADS)

    Mei, Hsien-Hao; Ni, Wei-Tou; Pan, Wei-Ping; Xu, Lixin; di Serego Alighieri, Sperello

    2015-06-01

    Recently, ACTPol measured the cosmic microwave background (CMB) B-mode and E-mode polarizations and obtained TE, EE, BB, TB, and EB power spectra in the multipole range 225–8725. In our previous paper (Paper I), we jointly analyzed the results of three experiments on the CMB B-mode polarization—SPTpol, POLARBEAR, and BICEP2—to include in the model, in addition to the gravitational lensing and inflationary gravitational waves components, the fluctuation effects induced by cosmic polarization rotation (CPR) if it exists within the upper limits at the time. In this paper, we fit both the mean CPR angle < α > and its fluctuation < δ {{α }2}> from the new ACTPol data, and update our fitting of CPR fluctuations using the BICEP2 data taking the new Planck dust measurement results into consideration. We follow the same method used in Paper I. The mean CPR angle is constrained from the EB correlation power spectra to |< α > |\\lt 14 mrad (0.°8) and the fluctuation (rms) is constrained from the BB correlation power spectra to {{< δ {{α }2}> }1/2}\\lt 29.3 mrad (1.°68). Assuming that the polarization angle of Tau A does not change from 89.2 to 146 GHz, the ACTPol data give < α > =1.0+/- 0\\buildrel{\\circ}\\over{.} 63. These results suggest that the inclusion of the present ACTPol data is consistent with no CPR detection. Using the new Planck dust measurement, we update our fits of the BICEP2 CPR fluctuation constraint to be 32.8 mrad (1.°88). The joint ACTPol-BICEP2-POLARBEAR CPR fluctuation constraint is 23.7 mrad (1.°36).

  4. In-depth Analysis of Land Surface Emissivity using Microwave Polarization Difference Index to Improve Satellite QPE

    NASA Astrophysics Data System (ADS)

    Zheng, Y.; Kirstetter, P. E.; Hong, Y.; Wen, Y.; Turk, J.; Gourley, J. J.

    2015-12-01

    One of primary uncertainties in satellite overland quantitative precipitation estimates (QPE) from passive sensors such as radiometers is the impact on the brightness temperatures by the surface land emissivity. The complexity of surface land emissivity is linked to its temporal variations (diurnal and seasonal) and spatial variations (subsurface vertical profiles of soil moisture, vegetation structure and surface temperature) translating into sub-pixel heterogeneity within the satellite field of view (FOV). To better extract the useful signal from hydrometeors, surface land emissivity needs to be determined and filtered from the satellite-measured brightness temperatures. Based on the dielectric properties of surface land cover constitutes, Microwave Polarization Differential index (MPDI) is expected to carry the composite effect of surface land properties on land surface emissivity, with a higher MPDI indicating a lower emissivity. This study analyses the dependence of MPDI to soil moisture, vegetation and surface skin temperature over 9 different land surface types. Such analysis is performed using the normalized difference vegetation index (NDVI) from MODIS, the near surface air temperature from the RAP model and ante-precedent precipitation accumulation from the Multi-Radar Multi-Sensor as surrogates for the vegetation, surface skin temperature and shallow layer soil moisture, respectively. This paper provides 1) evaluations of brightness temperature-based MPDI from the TRMM and GPM Microwave Imagers in both raining and non-raining conditions to test the dependence of MPDI to precipitation; 2) comparisons of MPDI categorized into instantly before, during and immediately after selected precipitation events to examine the impact of modest-to-heavy precipitation on the spatial pattern of MPDI; 3) inspections of relationship between MPDI versus rain fraction and rain rate within the satellite sensors FOV to investigate the behaviors of MPDI in varying

  5. Parity Violation Constraints Using Cosmic Microwave Background Polarization Spectra from 2006 and 2007 Observations by the QUaD Polarimeter

    SciTech Connect

    Wu, E. Y. S.; Church, S.; Hinderks, J.; Rusholme, B.; Thompson, K. L.; Ade, P.; Gear, W. K.; Gupta, S.; Rajguru, N.; Turner, A. H.; Bock, J.; Leitch, E.; Bowden, M.; Brown, M. L.; Cahill, G.; Murphy, J. A.; O'Sullivan, C.; Castro, P. G.; Culverhouse, T.; Friedman, R. B.

    2009-04-24

    We constrain parity-violating interactions to the surface of last scattering using spectra from the QUaD experiment's second and third seasons of observations by searching for a possible systematic rotation of the polarization directions of cosmic microwave background photons. We measure the rotation angle due to such a possible 'cosmological birefringence' to be 0.55 deg. {+-}0.82 deg. (random) {+-}0.5 deg. (systematic) using QUaD's 100 and 150 GHz temperature-curl and gradient-curl spectra over the spectra over the multipole range 200

  6. DC response of hot carriers under circularly polarized intense microwave fields and intense magnetic fields in quantum wells

    SciTech Connect

    Ishida, Norihisa

    2013-12-04

    Hot carrier dynamics under intense microwave and crossed magnetic fields are investigated theoretically for the case that the dominant scattering process is inelastic collision, especially intersubband and intrasubband transition in Quantum wells. If the applied electric fields are circularly polarized, the equation of motion forms symmetric on the x-y plane. But the carrier motions are complicated to accumulate because of acceleration and emission process. This situation makes possible to create a variation of the carrier motion, typically the carrier bunching is occurred. This state is a sort of population inversion. The DC response of this system attains strongly negative at appropriate field conditions. Through the simulation for the real case described below, it may include a type of induced emission.

  7. Microwave studies of collision-induced transitions between rotational levels. VIII. Collisions between NH/sub 3/ and polar molecules

    SciTech Connect

    Fabris, A.R.; Oka, T.

    1983-03-15

    The technique of four-level microwave double resonance has been applied to the study of rotation-inversion transitions of NH/sub 3/ induced by collisions with various polar molecules. H/sub 2/O, D/sub 2/O, CH/sub 3/OH, CH/sub 3/X and CHX/sub 3/ (X = F, Cl, Br, I), NO, CO, and OCS were used as collision partners. The values of eta = ..delta..I/I observed for many four-level systems which are connected by dipole-type transitions (..delta..J = +- 1, ..delta..K = 0, parity +bold-arrow-left-right-) are given and qualitatively explained taking into account the long-range dipole--dipole interaction and the pattern of rotational energy levels of the collision partners.

  8. COSMIC MICROWAVE BACKGROUND POLARIZATION AND TEMPERATURE POWER SPECTRA ESTIMATION USING LINEAR COMBINATION OF WMAP 5 YEAR MAPS

    SciTech Connect

    Samal, Pramoda Kumar; Jain, Pankaj; Saha, Rajib; Prunet, Simon; Souradeep, Tarun

    2010-05-01

    We estimate cosmic microwave background (CMB) polarization and temperature power spectra using Wilkinson Microwave Anisotropy Probe (WMAP) 5 year foreground contaminated maps. The power spectrum is estimated by using a model-independent method, which does not utilize directly the diffuse foreground templates nor the detector noise model. The method essentially consists of two steps: (1) removal of diffuse foregrounds contamination by making linear combination of individual maps in harmonic space and (2) cross-correlation of foreground cleaned maps to minimize detector noise bias. For the temperature power spectrum we also estimate and subtract residual unresolved point source contamination in the cross-power spectrum using the point source model provided by the WMAP science team. Our TT, TE, and EE power spectra are in good agreement with the published results of the WMAP science team. We perform detailed numerical simulations to test for bias in our procedure. We find that the bias is small in almost all cases. A negative bias at low l in TT power spectrum has been pointed out in an earlier publication. We find that the bias-corrected quadrupole power (l(l + 1)C{sub l} /2{pi}) is 532 {mu}K{sup 2}, approximately 2.5 times the estimate (213.4 {mu}K{sup 2}) made by the WMAP team.

  9. Building and flying the E and B Experiment to measure the polarization of the cosmic microwave background

    NASA Astrophysics Data System (ADS)

    Reichborn-Kjennerud, Britt

    2010-11-01

    The E and B Experiment (EBEX), a balloon-borne polarization sensitive microwave telescope, will map the cosmic microwave background (CMB) over a 420 deg2 patch of sky with 8' resolution. The observing area and resolution provide sensitivity to an angular power spectrum from ℓ = 20 to 1500. This will allow EBEX to observe the primordial B-mode signal predicted by inflation on a scale of about ℓ = 100 and the anticipated lensing B-mode signal at smaller angular scales. Simulations show that EBEX will detect the primordial B-mode signal if the tensor to scalar ratio, r, is 0.1, or it will reduce the current upper limit to 0.02. This limit assumes that errors due to foreground subtraction are below detector noise, and it does not include systematic uncertainties. During the EBEX ˜ 14-day Antarctic long duration science flight the instrument will observe with 1432 transition edge sensor (TES) bolometric detectors in three frequency bands centered at 150, 250, and 410 GHz. This broad frequency coverage will provide valuable information about foreground emission from thermal dust. The polarimetry and signal modulation are achieved using an achromatic half wave plate (HWP) rotating on a superconducting magnetic bearing and a fixed wire grid polarizer. In this thesis we discuss the EBEX science goals, instrument design, integration, and characterization. We provide an overview of the June, 2009, engineering flight from Ft. Sumner, NM, and a summary of the results from the flight. Additionally, we provide a detailed analysis of scan synchronous temperature signals in the warm optics and a preliminary analysis of bolometer data taken during galactic crossings in the engineering flight.

  10. Simulation of polar atmospheric microwave and sub-millimetre spectra for characterizing potential new ground-based observations

    NASA Astrophysics Data System (ADS)

    Newnham, David; Turner, Emma; Ford, George; Pumphrey, Hugh; Withington, Stafford

    2016-04-01

    Advanced detector technologies from the fields of astronomy and telecommunications are offering the potential to address key atmospheric science challenges with new instrumental methods. Adoption of these technologies in ground-based passive microwave and sub-millimetre radiometry could allow new measurements of chemical species and winds in the polar middle atmosphere for verifying meteorological data-sets and atmospheric models. A site study to assess the feasibility of new polar observations is performed by simulating the downwelling clear-sky submillimetre spectrum over 10-2000 GHz (30 mm to 150 microns) at two Arctic and two Antarctic locations under different seasonal and diurnal conditions. Vertical profiles for temperature, pressure and 28 atmospheric gases are constructed by combining radiosonde, meteorological reanalysis, and atmospheric chemistry model data. The sensitivity of the simulated spectra to the choice of water vapour continuum model and spectroscopic line database is explored. For the atmospheric trace species hypobromous acid (HOBr), hydrogen bromide (HBr), perhydroxyl radical (HO2) and nitrous oxide (N2O) the emission lines producing the largest change in brightness temperature are identified and minimum integration times and maximum receiver noise temperatures estimated. The optimal lines for all species are shown to vary significantly between location and scenario, strengthening the case for future hyperspectral instruments that measure over a broad frequency range. We also demonstrate the feasibility of measuring horizontal wind profiles above Halley station, Antarctica with time resolution as high as 0.5hr using simulated spectroradiometric observations of Doppler-shifted ozone (O3) and carbon monoxide (CO) lines in the 230-250 GHz region. The techniques presented provide a framework that can be applied to the retrieval of additional atmospheric parameters and be taken forward to simulate and guide the design of future microwave and sub

  11. Estimation of the sea surface's two-scale backscatter parameters

    NASA Technical Reports Server (NTRS)

    Wentz, F. J.

    1978-01-01

    The relationship between the sea-surface normalized radar cross section and the friction velocity vector is determined using a parametric two-scale scattering model. The model parameters are found from a nonlinear maximum likelihood estimation. The estimation is based on aircraft scatterometer measurements and the sea-surface anemometer measurements collected during the JONSWAP '75 experiment. The estimates of the ten model parameters converge to realistic values that are in good agreement with the available oceanographic data. The rms discrepancy between the model and the cross section measurements is 0.7 db, which is the rms sum of a 0.3 db average measurement error and a 0.6 db modeling error.

  12. Fabrication of Feedhorn-Coupled Transition Edge Sensor Arrays for Measurement of the Cosmic Microwave Background Polarization

    NASA Technical Reports Server (NTRS)

    Denis, Kevin L.; Aamir, A.; Bennett, C. L.; Chang, M. P.; Chuss, D. T.; Colazo, F. A.; Costen, N.; Essinger-Hileman, T.; Hu, R.; Marriage, T.; Rostem, K.; U-Yen, K.; Wollack, E. J.

    2015-01-01

    Characterization of the minute cosmic microwave background polarization signature requires multi-frequency high-throughput precision instrument systems. We have previously described the detector fabrication of a 40 GHz focal plane and now describe the fabrication of the detector modules for measurement of the CMB at 90GHz. The 74-TES based bolometers in each module are coupled to a niobium based planar orthomode transducer with integrated band defining filters implemented in microstrip transmission line. A single crystal silicon dielectric substrate serves as microstrip dielectric and as a thermal link between the membrane isolated MoAu TES operating at 150mK and the heat bath. A short silicon leg between the heat bath and the TES bolometer is designed for ballistic phonon transport and provides improved process control and uniformity of thermal conductance in the presence of phonon scattering on roughened surfaces. Micro-machined structures are used to realize the orthomode transducer backshort, provide out of band signal rejection, and a silicon photonic choke for feedhorn coupling are described. The backshort, choke wafer, and detector wafer are indium bump bonded to create a single 37-element dual-polarization detector module. Fourteen such hexagonally shaped modules each 90 mm in size comprise two focal planes. These, along with the recently delivered 40GHz focal plane, will survey a large fraction of the sky as part of the Johns Hopkins University led ground based CLASS (Cosmology Large Angular Scale Surveyor) telescope.

  13. The satellite altimeter data derived mean sea surface GSFC98

    NASA Astrophysics Data System (ADS)

    Wang, Yan M.

    2000-03-01

    The GSFC98 mean sea surface (MSS) was computed on a 2' oceanwide grid for latitudes below 80°. The data used included 3-years of TOPEX data (Cycles 9 to 119), 1.5-years of ERS-1 35-day repeat cycle (Cycles 1 to 18), 2-years of Geosat ERM data (Cycles 1 to 42), 2 ERS-1 168-day repeat cycles, and 18 months of the Geosat Geodetic Mission data. All non-TOPEX satellite altimeter data were adjusted to the mean of TOPEX data in 2° × 30° blocks. After the adjustment, the mean sea surface height was gridded into 2' nodes using least squares collocation and an iteration procedure to reduce the ocean variability. To validate the mean sea surfaces, three comparisons were made. The GSFC98 MSS, along with OSU95 [Yi, 1995] and CSR95 [Kim et al., 1995], were compared with 6-years of TOPEX and 3-years of ERS-2 mean tracks which were not used in the MSS computations. Finally, the marine gravity anomalies were computed from the three MSS implied geoid undulations using the inverse Stokes integral. The marine gravity anomalies were compared with ship gravity data in selected areas. The ship gravity comparison is an independent assessment of the quality of the MSSs, especially at intermediate and short wavelengths. Finally, the inter-comparisons between the mean sea surfaces were made. The root mean square values of the differences were 6.8, 6.8, and 7.2 cm between GSFC98/OSU95, GSFC98/CSR95, and OSU95/CSR95. The differences agree well with the error estimation of GSFC98 MSS.

  14. Sea surface temperature of the coastal zones of France

    NASA Technical Reports Server (NTRS)

    Deschamps, P. Y.; Crepon, M.; Monget, J. M.; Verger, F. (Principal Investigator); Frouin, R.; Cassanet, J.; Wald, L.

    1980-01-01

    The various thermal gradients in the coastal zones of France were mapped with regard to natural phenomena and man made thermal effluents. The mesoscale thermal features of the English Channel, the Bay of Biscay, and the northwestern Mediterranean Sea were also studied. The evolution of the thermal gradients generated by the main estuaries of the French coastal zones was investigated along with the modeling of diurnal heating of the sea surface and its influence on the oceanic surface layers.

  15. Japanese Whaling Ships' Sea Surface Temperatures 1946-84.

    NASA Astrophysics Data System (ADS)

    Mierzejewska, Anna W.; Wu, Zhongxiang; Newell, Reginald E.; Miyashita, Tomio

    1997-03-01

    Japanese whaling ship data, a homogeneous dataset mainly covering the southern high-latitude oceans, may be used to fill in gaps in recent sea surface temperature datasets, contributing a fair number of additional observations in this area. The Japanese whaling ship data are treated separately here for the period 1946-84, and they show no significant temperature changes during this period in the main fishing region of 60°-70°S or in the west Pacific warm pool.

  16. Sea surface determination from space: The GSFC geoid

    NASA Technical Reports Server (NTRS)

    Vonbun, F. O.; Mcgoogan, J.; Marsh, J.; Lerch, F. J.

    1975-01-01

    The determination of the sea surface/geoid and its relative variation were investigated and results of the altimeter experiment on Skylab to test the geoid are discussed. The spaceborne altimeter on Skylab revealed that the sea surface of the world's oceans can be measured with an accuracy in the meter range. Surface variations are discussed as they relate to those computed from satellite orbital dynamics and ground based gravity data. The GSFC geoid was constructed from about 400,000 satellite tracking data (range, range rate, angles) and about 20,000 ground gravity observations. One of the last experiments on Skylab was to measure and/or test this geoid over almost one orbit. It was found that the computed water surface deviates between 5 to 20 m from the measured one. Further outlined are the influence of orbital errors on the sea surface, and numerical examples are given based upon real tracking data. Orbital height error estimates were computed for geodetic type satellites and are found to be in the order of 0.2 to 5 meters.

  17. The incident solar irradiance at the sea surface

    NASA Technical Reports Server (NTRS)

    Van Tran, AN; Collins, Donald J.

    1990-01-01

    Computations have been performed of the incident spectral irradiance at the sea surface using LOWTRAN-7 as the basis to describe the incident scalar and vector irradiance in terms of the true solar zenith angle and the nominal visibility in the atmosphere. These computations have been used to describe the contributions to the incident irradiance from the direct and the sky components of the total irradiance and the average cosine of the sky component as a measure of the radiance distribution of the sky for varying atmospheric conditions. Comparisons of the computations from LOWTRAN-7 have been made with the results from other models, and with data obtained from field measurements, and excellent agreement has been obtained for the daily profiles of the vector and scalar irradiance at the surface. These computations have been used to provide a description of the irradiance at the sea surface for use in the analysis of remotely sensed data based on information on the radiative transfer through the atmosphere above the sea surface.

  18. Fabrication of Feedhorn-Coupled Transition Edge Sensor Arrays for Measurement of the Cosmic Microwave Background Polarization

    NASA Technical Reports Server (NTRS)

    Denis, K. L.; Ali, A.; Appel, J.; Bennett, C. L.; Chang, M. P.; Chuss, D. T.; Colazo, F. A.; Costen, N.; Essinger-Hileman, T.; Hu, R.; Marriage, T.; Rostem, K.; U-Yen, K.; Wollack, E. J.

    2015-01-01

    Characterization of the minute cosmic microwave background (CMB) polarization signature requires multi-frequency high-throughput precision instrument systems. We have previously described the detector fabrication of a 40 gigahertz focal plane and now describe the fabrication of a 37-element dual-polarization detector module for measurement of the CMB at 90 gigahertz. The 72-TES (Transition Edge Sensor)-based bolometers in each module are coupled to a niobium-based planar orthomode transducer with integrated band defining filters implemented in microstrip transmission line. A single crystal silicon dielectric substrate serves as microstrip dielectric and as a thermal link between the membrane isolated MoAu TES operating at 150 millikelvins and the heat bath. A short silicon leg between the heat bath and the TES bolometer is designed for ballistic phonon transport and provides improved process control and uniformity of thermal conductance in the presence of phonon scattering on roughened surfaces. Micro-machined structures are used to realize the orthomode transducer backshort, provide out of band signal rejection, and a silicon photonic choke for feedhorn coupling are described. The backshort, choke wafer, and detector wafer are indium bump-bonded to create a single 37-element dual-polarization detector module. Fourteen such hexagonally shaped modules each 80 millimeters in size comprise two focal planes. These, along with the recently delivered 40 gigahertz focal plane, will survey a large fraction of the sky as part of the Johns Hopkins University-led ground-based CLASS (Cosmology Large Angular Scale Surveyor) telescope.

  19. Sensitivity and foreground modelling for large-scale cosmic microwave background B-mode polarization satellite missions

    NASA Astrophysics Data System (ADS)

    Remazeilles, M.; Dickinson, C.; Eriksen, H. K. K.; Wehus, I. K.

    2016-05-01

    The measurement of the large-scale B-mode polarization in the cosmic microwave background (CMB) is a fundamental goal of future CMB experiments. However, because of unprecedented sensitivity, future CMB experiments will be much more sensitive to any imperfect modelling of the Galactic foreground polarization in the reconstruction of the primordial B-mode signal. We compare the sensitivity to B-modes of different concepts of CMB satellite missions (LiteBIRD, COrE, COrE+, PRISM, EPIC, PIXIE) in the presence of Galactic foregrounds. In particular, we quantify the impact on the tensor-to-scalar parameter of incorrect foreground modelling in the component separation process. Using Bayesian fitting and Gibbs sampling, we perform the separation of the CMB and Galactic foreground B-modes. The recovered CMB B-mode power spectrum is used to compute the likelihood distribution of the tensor-to-scalar ratio. We focus the analysis to the very large angular scales that can be probed only by CMB space missions, i.e. the reionization bump, where primordial B-modes dominate over spurious B-modes induced by gravitational lensing. We find that fitting a single modified blackbody component for thermal dust where the `real' sky consists of two dust components strongly bias the estimation of the tensor-to-scalar ratio by more than 5σ for the most sensitive experiments. Neglecting in the parametric model the curvature of the synchrotron spectral index may bias the estimated tensor-to-scalar ratio by more than 1σ. For sensitive CMB experiments, omitting in the foreground modelling a 1 per cent polarized spinning dust component may induce a non-negligible bias in the estimated tensor-to-scalar ratio.

  20. A Match-based approach to the estimation of polar stratospheric ozone loss using Aura Microwave Limb Sounder observations

    NASA Astrophysics Data System (ADS)

    Livesey, N. J.; Santee, M. L.; Manney, G. L.

    2015-04-01

    The well-established "Match" approach to quantifying chemical destruction of ozone in the polar lower stratosphere is applied to ozone observations from the Microwave Limb Sounder (MLS) on NASA's Aura spacecraft. Quantification of ozone loss requires distinguishing transport- and chemically induced changes in ozone abundance. This is accomplished in the Match approach by examining cases where trajectories indicate that the same airmass has been observed on multiple occasions. The method was pioneered using ozone sonde observations, for which hundreds of matched ozone observations per winter are typically available. The dense coverage of the MLS measurements, particularly at polar latitudes, allows matches to be made to thousands of observations each day. This study is enabled by recently developed MLS Lagrangian Trajectory Diagnostic (LTD) support products. Sensitivity studies indicate that the largest influence on the ozone loss estimates are the value of potential vorticity (PV) used to define the edge of the polar vortex (within which matched observations must lie) and the degree to which the PV of an airmass is allowed to vary between matched observations. Applying Match calculations to MLS observations of nitrous oxide, a long-lived tracer whose expected rate of change on these timescales is negligible, enables quantification of the impact of transport errors on the Match-based ozone loss estimates. Our loss estimates are generally in agreement with previous estimates for selected Arctic winters, though indicating smaller losses than many other studies. Arctic ozone losses are greatest during the 2010/11 winter, as seen in prior studies, with 2.0 ppmv (parts per million by volume) loss estimated at 450 K potential temperature. As expected, Antarctic winter ozone losses are consistently greater than those for the Arctic, with less interannual variability (e.g., ranging between 2.3 and 3.0 ppmv at 450 K). This study exemplifies the insights into atmospheric

  1. Applications of the NPOESS Visible/Infrared and Microwave Imagers

    NASA Astrophysics Data System (ADS)

    Lee, T. F.; Hawkins, J. D.; Turk, F. J.; Kuciauskas, A.; Richardson, K.; Miller, S.

    2008-12-01

    Satellites from the National Polar-orbiting Operational Environmental Satellite System (NPOESS) will contain two key imagers responsible for a large number of operational products. These are the Visible Infrared Imaging Radiometer Suite (VIIRS), and the Microwave Imager Sounder (MIS). VIIRS will fly on all NPOESS satellites, initial launch expected in 2013, and the NPOESS Preparatory Project (NPP) satellite to be launched in 2010. Three of the four planned NPOESS satellites will carry MIS, starting in 2016. This presentation will discuss each sensor and show prototype products from existing sensors. The VIIRS instrument will contain 22 channels, ranging from the visible to infrared. It will have a swath of 3000 km. Data from all of the VIIRS channels will be produced using scan geometry which allows only slow pixel expansion toward the edge of scan. This feature enables imagery which is as sharp at the edge of scan as near nadir, enabling many more high-resolution zooms per overpass. We will also discuss in some detail the Day/Night Band (DNB), a channel for low-light imaging at night. The DNB will be considerably improved compared to the nighttime visible channel aboard the Defense Meteorological Satellite Program (DMSP) satellites with many more display levels, decreased noise and artifacts, higher spatial resolution, and full integration into the VIIRS radiometer suite. The MIS design is still being completed. However, with a larger number of channels than predecessor sensors, it will have the capability to improve upon the products from the DMSP Special Sensor Microwave Imager (SSM/I) and the Special Sensor Microwave Imager Sounder (SSMIS). It will also create products previewed by WindSat, the first spaceborne polarametric microwave imager built by the Naval Research Laboratory and flown aboard the DoD Space Test Program's Coriolis satellite. Products include sea surface temperature, soil moisture, sea surface wind vectors, total precipitable water, and

  2. Microwave properties of a quiet sea

    NASA Technical Reports Server (NTRS)

    Stacey, J.

    1985-01-01

    The microwave flux responses of a quiet sea are observed at five microwave frequencies and with both horizontal and vertical polarizations at each frequency--a simultaneous 10 channel receiving system. The measurements are taken from Earth orbit with an articulating antenna. The 10 channel responses are taken simultaneously since they share a common articulating collector with a multifrequency feed. The plotted flux responses show: (1) the effects of the relative, on-axis-gain of the collecting aperture for each frequency; (2) the effects of polarization rotation in the output responses of the receive when the collecting aperture mechanically rotates about a feed that is fixed; (3) the difference between the flux magnitudes for the horizontal and vertical channels, at each of the five frequencies, and for each pointing position, over a 44 degree scan angle; and (4) the RMS value of the clutter--as reckoned over the interval of a full swath for each of the 10 channels. The clutter is derived from the standard error of estimate of the plotted swath response for each channel. The expected value of the background temperature is computed for each of the three quiet seas. The background temperature includes contributions from the cosmic background, the downwelling path, the sea surface, and the upwelling path.

  3. Large scale anisotropies and polarization of the microwave background radiation in homogeneous cosmologies

    NASA Astrophysics Data System (ADS)

    Tolman, B. W.; Matzner, R. A.

    1984-04-01

    A quadrupole anisotropy in the expansion of the universe (shear) is considered in realistic cosmological models, and a calculation is made of the resulting anisotropies and polarization of the radiation. The role of spatial curvature is treated separately; it is found to have two profound effects. The first, in closed models only, is that the direction of polarization of the radiation will appear upon observation to be twisted in relation to the anisotropy; the existence of this twist is seen as implying that the closed universe has a handedness property. The second effect, in open models, is that a quadrupole anisotropy may be distorted by the spatial curvature so that it resembles a dipole; it is noted that in the extreme case all the anisotropy is confined to a region of small angular diameter (a 'spot'). On the basis of the work reported by Dautcourt and Rose (1978), a derivation is provided of a transfer equation for polarized radiation in a general curved space-time. An allowance is made for the effect of Thomson scattering by free electrons, and the equation is separated into those for the multipoles up to quadrupole by expanding in polynomials formed from spring-weighted spherical harmonics.

  4. Three-dimensional inhomogeneous rain fields: implications for the distribution of intensity and polarization of the microwave thermal radiation.

    NASA Astrophysics Data System (ADS)

    Ilyushin, Yaroslaw; Kutuza, Boris

    Observations and mapping of the upwelling thermal radiation of the Earth is the very promising remote sensing technique for the global monitoring of the weather and precipitations. For reliable interpretation of the observation data, numerical model of the microwave radiative transfer in the precipitating atmosphere is necessary. In the present work, numerical simulations of thermal microwave radiation in the rain have been performed at three wavelengths (3, 8 and 22 mm). Radiative properties of the rain have been simulated using public accessible T-matrix codes (Mishchenko, Moroz) for non-spherical particles of fixed orientation and realistic raindrop size distributions (Marshall-Palmer) within the range of rain intensity 1-100 mm/h. Thermal radiation of infinite flat slab medium and isolated rain cell of kilometer size has been simulated with finite difference scheme for the vectorial radiative transfer equation (VRTE) in dichroic scattering medium. Principal role of cell structure of the rain field in the formation of angular and spatial distribution of the intensity and polarization of the upwelling thermal radiation has been established. Possible approaches to interpretation of satellite data are also discussed. It is necessary that spatial resolution of microwave radiometers be less than rain cell size. At the present time the resolution is approximately 15 km. It can be considerably improved, for example by two-dimensional synthetic aperture millimeter-wave radiometric interferometer for measuring full-component Stokes vector of emission from hydrometeors. The estimates show that in millimeter band it is possible to develop such equipment with spatial resolution of the order of 1-2 km, which is significantly less than the size of rain cell, with sensitivity 0.3-0.5 K. Under this condition the second Stokes parameter may by successfully measured and may be used for investigation of precipitation regions. Y-shaped phased array antenna is the most promising to

  5. Effect of Recent Sea Surface Temperature Trends on the Arctic Stratospheric Vortex

    NASA Technical Reports Server (NTRS)

    Garfinkel, Chaim I.; Oman, Luke; Hurwitz, Margaret

    2015-01-01

    The springtime Arctic polar vortex has cooled significantly over the satellite era, with consequences for ozone concentrations in the springtime transition season. The causes of this cooling trend are deduced by using comprehensive chemistry-climate model experiments. Approximately half of the satellite era early springtime cooling trend in the Arctic lower stratosphere was caused by changing sea surface temperatures (SSTs). An ensemble of experiments forced only by changing SSTs is compared to an ensemble of experiments in which both the observed SSTs and chemically- and radiatively-active trace species are changing. By comparing the two ensembles, it is shown that warming of Indian Ocean, North Pacific, and North Atlantic SSTs, and cooling of the tropical Pacific, have strongly contributed to recent polar stratospheric cooling in late winter and early spring, and to a weak polar stratospheric warming in early winter. When concentrations of ozone-depleting substances and greenhouse gases are fixed, polar ozone concentrations show a small but robust decline due to changing SSTs. Ozone changes are magnified in the presence of changing gas concentrations. The stratospheric changes can be understood by examining the tropospheric height and heat flux anomalies generated by the anomalous SSTs. Finally, recent SST changes have contributed to a decrease in the frequency of late winter stratospheric sudden warmings.

  6. Satellite-derived sea surface height and sea surface wind data fusion for spilled oil tracking

    NASA Astrophysics Data System (ADS)

    Kozai, K.

    Data fusion is defined as a framework with the purpose of obtaining information of 'greater quality'. Within the framework tools are expressed for the alliance of data originating from different sources. The exact definition of 'greater quality' is stated in this context as more reliable prediction for the trajectory of spilled oil from two different microwave sensor data, namely ERS-2 altimeter and ADEOS/NSCAT scatterometer data. An example is presented in the case of trajectory of bow section and associated oil upwelling from the sunken tanker Nakhodka occurred from January to June in 1997 in Japan Sea. Spill distance is defined as a horizontal distance from the oil upwelling point to the location of sunken Nakhodka and a spill direction is defined as an angle made by the geographic north and the line corresponding to the spill distance. Geostrophic current vectors are derived from ERS-2 altimeter and wind-induced current vectors are derived from ADEOS/NSCAT scatterometer data. These two different satellite-derived vectors are 'fused' together in the surface current model to estimate and evaluate the trajectory of bow section and associated oil upwelling from the sunken tanker Nakhodka. Result of comparison between the estimated and the observed trajectory of bow section indicates that the estimated trajectory is agreed well with the observed one in the first half of drift period, while in the latter half of drift period the estimated trajectory is not agreed well with the observed one, which may be attributable to changes of wind directions within 24 hours from the satellite overpasses. Moreover the comparison between spill vector and 'fused' surface current vector shows the good correspondence in terms of direction when in situ wind accelerates the surface current vector, while the comparison between the twos shows the bad correspondence when the temporal changes of wind vector occurs.

  7. Analysis of Ultra High Resolution Sea Surface Temperature Level 4 Datasets

    NASA Technical Reports Server (NTRS)

    Wagner, Grant

    2011-01-01

    Sea surface temperature (SST) studies are often focused on improving accuracy, or understanding and quantifying uncertainties in the measurement, as SST is a leading indicator of climate change and represents the longest time series of any ocean variable observed from space. Over the past several decades SST has been studied with the use of satellite data. This allows a larger area to be studied with much more frequent measurements being taken than direct measurements collected aboard ship or buoys. The Group for High Resolution Sea Surface Temperature (GHRSST) is an international project that distributes satellite derived sea surface temperatures (SST) data from multiple platforms and sensors. The goal of the project is to distribute these SSTs for operational uses such as ocean model assimilation and decision support applications, as well as support fundamental SST research and climate studies. Examples of near real time applications include hurricane and fisheries studies and numerical weather forecasting. The JPL group has produced a new 1 km daily global Level 4 SST product, the Multiscale Ultrahigh Resolution (MUR), that blends SST data from 3 distinct NASA radiometers: the Moderate Resolution Imaging Spectroradiometer (MODIS), the Advanced Very High Resolution Radiometer (AVHRR), and the Advanced Microwave Scanning Radiometer ? Earth Observing System(AMSRE). This new product requires further validation and accuracy assessment, especially in coastal regions.We examined the accuracy of the new MUR SST product by comparing the high resolution version and a lower resolution version that has been smoothed to 19 km (but still gridded to 1 km). Both versions were compared to the same data set of in situ buoy temperature measurements with a focus on study regions of the oceans surrounding North and Central America as well as two smaller regions around the Gulf Stream and California coast. Ocean fronts exhibit high temperature gradients (Roden, 1976), and thus

  8. Dependence of SMOS/MIRAS brightness temperatures on wind speed: sea surface effect and latitudinal biases

    NASA Astrophysics Data System (ADS)

    Yin, Xiaobin; Boutin, Jacqueline; Martin, Nicolas; Spurgeon, Paul

    2013-04-01

    SMOS (Soil Moisture and Ocean Salinity) has been successfully launched in November 2009 and its only payload, Microwave Imaging Radiometer using Aperture Synthesis (MIRAS) instrument, is the first interferometric radiometer at L band (1.4GHz) in orbit. MIRAS employs aperture synthesis in 2D with a Y-shaped antenna structure to create an image of emissions from the Earth surface at L-band over a range of incidence angles (0° to 65°) with a spatial resolution of 35 to 110 km. More than two years after launch the level 1C (L1C) brightness temperatures (TBs) reprocessed with the up-to-date ESA level 1 processing version (the Level 1 processor V5.04 and V5.05), have been released. It has been shown during the commissioning phase that the receivers onboard of MIRAS are affected by a short-term drift during each orbit, and a seasonal variation due to the thermal drifts of the antenna patch. Although a new antenna model is incorporated in the ESA L1 V5 processing to account for these variations, latitudinal and seasonal drifts in L1C TBs are still observed. In this presentation, we first investigate the impact of the TB drifts on the sea surface emissivity roughness model we derived in Yin et al. (TGRS 2012) from multi-latitude level 1 V3.17 TBs. We then study dependencies of TBs at multi-incidence angles with wind speed separately for various latitudinal bands and different seasons in order to separate artificial effects of TB drifts from sea surface effects. We then propose a new roughness/foam forward model. We estimate the quality of SMOS retrieved SSS by comparing it with ARGO measurements, and discuss SSS quality given the imprecision of the forward model and of the wind speed used as prior value in the level 2 ocean salinity processor.

  9. Retrieving sea surface salinity with multiangular L-band brightness temperatures: Improvement by spatiotemporal averaging

    NASA Astrophysics Data System (ADS)

    Camps, A.; Vall-Llossera, M.; Batres, L.; Torres, F.; Duffo, N.; Corbella, I.

    2005-04-01

    The Soil Moisture and Ocean Salinity (SMOS) mission was selected in May 1999 by the European Space Agency to provide global and frequent soil moisture and sea surface salinity maps. SMOS' single payload is Microwave Imaging Radiometer by Aperture Synthesis (MIRAS), an L band two-dimensional aperture synthesis interferometric radiometer with multiangular observation capabilities. Most geophysical parameter retrieval errors studies have assumed the independence of measurements both in time and space so that the standard deviation of the retrieval errors decreases with the inverse of square root of the number of measurements being averaged. This assumption is especially critical in the case of sea surface salinity (SSS), where spatiotemporal averaging is required to achieve the ultimate goal of 0.1 psu error. This work presents a detailed study of the SSS error reduction by spatiotemporal averaging, using the SMOS end-to-end performance simulator (SEPS), including thermal noise, all instrumental error sources, current error correction and image reconstruction algorithms, and correction of atmospheric and sky noises. The most important error sources are the biases that appear in the brightness temperature images. Three different sources of biases have been identified: errors in the noise injection radiometers, Sun contributions to the antenna temperature, and imaging under aliasing conditions. A calibration technique has been devised to correct these biases prior to the SSS retrieval at each satellite overpass. Simulation results show a retrieved salinity error of 0.2 psu in warm open ocean, and up to 0.7 psu at high latitudes and near the coast, where the external calibration method presents more difficulties.

  10. Pliocene-Pleistocene evolution of sea surface and intermediate water temperatures from the southwest Pacific

    NASA Astrophysics Data System (ADS)

    McClymont, Erin L.; Elmore, Aurora C.; Kender, Sev; Leng, Melanie J.; Greaves, Mervyn; Elderfield, Henry

    2016-06-01

    Over the last 5 million years, the global climate system has evolved toward a colder mean state, marked by large-amplitude oscillations in continental ice volume. Equatorward expansion of polar waters and strengthening temperature gradients have been detected. However, the response of the mid latitudes and high latitudes of the Southern Hemisphere is not well documented, despite the potential importance for climate feedbacks including sea ice distribution and low-high latitude heat transport. Here we reconstruct the Pliocene-Pleistocene history of both sea surface and Antarctic Intermediate Water (AAIW) temperatures on orbital time scales from Deep Sea Drilling Project Site 593 in the Tasman Sea, southwest Pacific. We confirm overall Pliocene-Pleistocene cooling trends in both the surface ocean and AAIW, although the patterns are complex. The Pliocene is warmer than modern, but our data suggest an equatorward displacement of the subtropical front relative to present and a poleward displacement of the subantarctic front of the Antarctic Circumpolar Current (ACC). Two main intervals of cooling, from ~3 Ma and ~1.5 Ma, are coeval with cooling and ice sheet expansion noted elsewhere and suggest that equatorward expansion of polar water masses also characterized the southwest Pacific through the Pliocene-Pleistocene. However, the observed trends in sea surface temperature and AAIW temperature are not identical despite an underlying link to the ACC, and intervals of unusual surface ocean warmth (~2 Ma) and large-amplitude variability in AAIW temperatures (from ~1 Ma) highlight complex interactions between equatorward displacements of fronts associated with the ACC and/or varying poleward heat transport from the subtropics.

  11. Doppler spectra of electromagnetic fields scattered from two-dimensional fetch- and depth-limited nearshore sea surfaces

    NASA Astrophysics Data System (ADS)

    Nie, Ding; Zhang, Min; Li, Ning; Jiang, Wangqiang

    2014-11-01

    Doppler spectral signatures of sea echoes from two-dimensional (2-D) fetch- and depth-limited sea surfaces are investigated using the second-order small-slope approximation (SSA-II) model. For the description of 2-D nearshore sea surface, the revised choppy wave model (RCWM) is applied, which takes into account the wind fetch effect and water depth effect in nearshore marine environment. Comparisons of computed results in co-polarizations and cross polarization at various incident angles show that Doppler shift and spectral bandwidth can be greatly influenced by hydrodynamic modulation of waves in the large wind fetch and small water depth marine environment, which indicates that the hydrodynamic modulation induced by shoaling effect would be greatly enhanced in the situation of the nearshore shallow sea with a long wind fetch. The differences in variation trend between results in co-polarizations and cross polarization also reflect varying degrees of influence of aforementioned hydrodynamic modulation on different scattering mechanisms.

  12. Microwave Radiometers from 0.6 to 22 GHz for Juno, a Polar Orbiter around Jupiter

    NASA Technical Reports Server (NTRS)

    Pingree, Paula J.; Janssen, M.; Oswald, J.; Brown, S.; Chen, J.; Hurst, K.; Kitiyakara, A.; Maiwald, F.; Smith, S.

    2008-01-01

    A compact instrument called the MWR (microwave radiometer) is under development at JPL for Juno, the next NASA new frontiers mission, scheduled to launch in 2011. It's purpose is to measure the thermal emission from Jupiter's atmosphere at six selected frequencies from 0.6 to 22 GHz, operating in direct detection mode, in order to quantify the distributions and abundances of water and ammonia in Jupiter's atmosphere. The goal is to understand the previously unobserved dynamics of the sub-cloud atmosphere, and to discriminate among models for planetary formation in our solar system. as part of a deep space mission aboard a solar-powered spacecraft, MWR is designed to be compact, lightweight, and low power. The receivers and control electronics are protected by a radiation-shielding enclosure on the Juno spacecraft that also provides for a benign and stable operating temperature environment. All antennas and RF transmission lines outside the vault must withstand low temperatures and the harsh radiation environment surrounding Jupiter. This paper describes the concept of the MWR instrument and presents results of one breadboard receiver channel.

  13. Microwave Radiometers from 0.6 to 22 GHz for Juno, A Polar Orbiter Around Jupiter

    NASA Technical Reports Server (NTRS)

    Pingree, P.; Janssen, M.; Oswald, J.; Brown, S.; Chen, J.; Hurst, K.; Kitiyakara, A.; Maiwald, F.; Smith, S.

    2008-01-01

    A compact instrument called the MWR (MicroWave Radiometer) is under development at JPL for Juno, the next NASA New Frontiers mission, scheduled to launch in 2011. It's purpose is to measure the thermal emission from Jupiter's atmosphere at six selected frequencies from 0.6 to 22 GHz, operating in direct detection mode, in order to quantify the distributions and abundances of water and ammonia in Jupiter's atmosphere. The goal is to understand the previously unobserved dynamics of the sub-cloud atmosphere, and to discriminate among models for planetary formation in our solar system. As part of a deep space mission aboard a solar-powered spacecraft, MWR is designed to be compact, lightweight, and low power. The receivers and control electronics are protected by a radiation-shielding enclosure on the Juno spacecraft that would provide a benign and stable operating temperature environment. All antennas and RF transmission lines outside the vault must withstand low temperatures and the harsh radiation environment surrounding Jupiter. This paper describes the concept of the MWR instrument and presents results of one breadboard receiver channel.

  14. Pre-Launch Characterization of the Advanced Technology Microwave Sounder (ATMS) on the Joint Polar Satellite System-1 Satellite (JPSS-1)

    NASA Astrophysics Data System (ADS)

    Kim, Edward; Leslie, Vince; Lyu, Joseph; Smith, Craig; McCormick, Lisa; Anderson, Kent

    2016-04-01

    The Advanced Technology Microwave Sounder (ATMS) is the newest generation of microwave sounder in the international fleet of polar-orbiting weather satellites, replacing the Advanced Microwave Sounding Unit (AMSU) which first entered service in 1998. The first ATMS was launched aboard the Suomi NPP (S-NPP) satellite in late 2011. The second ATMS is manifested on the Joint Polar Satellite System-1 Satellite (JPSS-1). ATMS provides 22 channels of temperature and humidity sounding observations over a frequency range from 23 to 183 GHz. These microwave soundings provide the highest impact data ingested by operational Numerical Weather Prediction (NWP) models, and are the most critical of the polar-orbiting satellite observations, particularly because microwave sensing can penetrate clouds. This paper will present performance characterizations from pre-launch calibration measurements of the JPSS-1 ATMS just completed in December, 2015. The measurements were conducted in a thermal vacuum chamber with blackbody targets simulating cold space, ambient, and a variable Earth scene. They represent the best opportunity for calibration characterization of the instrument since the environment can be carefully controlled. We will present characterizations of the sensitivity (NEDT), accuracy, nonlinearity, noise spectral characteristics, gain stability, repeatability, and inter-channel correlation. An estimate of expected "striping" will be presented, and a discussion of reflector emissivity effects will also be provided. Comparisons will be made with the S-NPP flight unit. Finally, we will describe planned on-orbit characterizations - such as pitch and roll maneuvers - that will further improve both the measurement quality and the understanding of various error contributions.

  15. Dynamical processes of transfer at the sea surface

    NASA Astrophysics Data System (ADS)

    Thorpe, S. A.

    This review describes the dynamical processes of transport from, and immediately below, the sea surface, particularly those which involve convergence and the separation of flow, and which result in the renewal of surface water at horizontal scales ranging from millimeters to hundreds of meters. Turbulence at or near the sea surface derives from several processes - breaking waves and the bubbles they may produce, precipitation and spray, Langmuir circulation and thermal convection, and turbulence which is internally generated by shear. Interest in the subject derives from the requirements to predict air-sea fluxes of heat, momentum and gases, to develop climate models, to interpret satellite images of the sea surface, including those of ship wakes, and to predict upper ocean structure, including mixing layer depth, in models of phytoplankton blooms and acoustic propagation. The general effect of subsurface turbulence on the sea surface, and the effects of surfactants, is described, and each process is discussed in turn. Laboratory experiments and theoretical studies have contributed particularly to the understanding of the interaction of vortices and turbulence with the surface and to the consequences of breaking waves. They point to the development of instability in the flow ahead of steep waves carrying parasitic capillary waves, which may contribute to the onset of flow separation on the leading face of the waves and the development of a rotor, or ‘roller’, below the wave crest, shown most clearly in the pattern of streamlines in a frame of reference moving forward with the wave. The conditions near the flow separation line on the wave surface ahead of the rotor may be similar to those produced by vortices approaching a free surface. Detailed observation of breaking waves at sea is lacking, but some progress has been made using acoustics to detect the clouds of subsurface bubbles formed by the larger breakers and the depth to which they penetrate. The

  16. Broadband, polarization-insensitive, and wide-angle microwave absorber based on resistive film

    NASA Astrophysics Data System (ADS)

    Dan-Dan, Bu; Chun-Sheng, Yue; Guang-Qiu, Zhang; Yong-Tao, Hu; Sheng, Dong

    2016-06-01

    A simple design of broadband metamaterial absorber (MA) based on resistive film is numerically presented in this paper. The unit cell of this absorber is composed of crossed rectangular rings-shaped resistive film, dielectric substrate, and continuous metal film. The simulated results indicate that the absorber obtains a 12.82-GHz-wide absorption from about 4.75 GHz to 17.57 GHz with absorptivity over 90% at normal incidence. Distribution of surface power loss density is illustrated to understand the intrinsic absorption mechanism of the structure. The proposed structure can work at wide polarization angles and wide angles of incidence for both transverse electric (TE) and transverse magnetic (TM) waves. Finally, the multi-reflection interference theory is involved to analyze and explain the broadband absorption mechanism at both normal and oblique incidence. Moreover, the polarization-insensitive feature is also investigated by using the interference model. It is seen that the simulated and calculated absorption rates agree fairly well with each other for the absorber.

  17. GroundBIRD: Observing Cosmic Microwave Polarization at Large Angular Scale with Kinetic Inductance Detectors and High-Speed Rotating Telescope

    NASA Astrophysics Data System (ADS)

    Oguri, S.; Choi, J.; Damayanthi, T.; Hattori, M.; Hazumi, M.; Ishitsuka, H.; Karatsu, K.; Mima, S.; Minowa, M.; Nagasaki, T.; Otani, C.; Sekimoto, Y.; Tajima, O.; Tomita, N.; Yoshida, M.; Won, E.

    2016-08-01

    Cosmic microwave background (CMB) is an important source of information about the origin of our universe. In particular, odd-parity large angular scale patterns in the CMB polarization, the primordial B-modes, are strong evidence for an inflationary universe, related to the accelerating expansion of the metric. We are developing a unique telescope, GroundBIRD, to take CMB polarization measurements. The telescope combines novel techniques: high-speed rotation scanning, cold optics, and microwave kinetic inductance detectors (MKIDs). We evaluated the response of MKIDs on the rotation stage. Method of shielding from the geo-magnetic field is established. We have also developed a receiver cryostat. We are able to maintain a sufficient cold status for observations on the optical configuration. We plan to start commissioning the system by observing CMB in Japan in 2015-2016. We will then deploy GroundBIRD in the Canary Islands for further scientific observations.

  18. Medium-assisted non-polar solvent dynamic microwave extraction for determination of organophosphorus pesticides in cereals using gas chromatography-mass spectrometry.

    PubMed

    Wu, Lijie; Song, Ying; Xu, Xu; Li, Na; Shao, Mingyuan; Zhang, Hanqi; Yu, Aimin; Yu, Cui; Ma, Qiang; Lu, Chunmei; Wang, Ziming

    2014-11-01

    A fast and green pretreatment method, medium-assisted non-polar solvent dynamic microwave extraction, was first applied to extract ten of organophosphorus pesticides (OPPs) from five cereal samples. Without adding any polar solvent, graphite powders (GP) were used as microwave absorption medium to transform microwave energy into heat energy. For recycling GP, an extractor was made by sealing GP inside the exterior tube of a glass sleeve. By dynamic microwave extraction using hexane as extraction solvent, ten OPPs could be extracted completely within 200s, and the extract was directly analysed by GC-MS without any clean-up process. The effects of some experimental parameters on extraction efficiency were investigated and optimised. Relative standard deviations of intra- and inter-day ranging from 1.02% to 5.32% were obtained. Five real samples were analysed, and the recoveries obtained were in the range of 73.2-99.8%, and the relative standard deviations were lower than 6.63%. PMID:24874384

  19. The PRISM palaeoclimate reconstruction and Pliocene sea-surface temperature

    USGS Publications Warehouse

    Dowsett, H.J.

    2007-01-01

    In this paper, I present a summary of the Pliocene Research, Interpretation and Synoptic Mapping (PRISM) palaeoenvironmental reconstruction, with emphasis on its historical development and range of boundary condition datasets. Sea-surface temperature (SST), sea level, sea ice, land cover (vegetation and ice) and topography are discussed as well as many of the assumptions required to create an integrated global-scale reconstruction. New multiproxy research shows good general agreement on the magnitude of mid-Pliocene SST warming. Future directions, including maximum and minimum SST analyses and deep ocean temperature estimates aimed at a full three-dimensional reconstruction, are presented. ?? The Micropalaeontological Society 2007.

  20. Sea Surface Temperature and Vegetation Index from MODIS

    NASA Technical Reports Server (NTRS)

    2002-01-01

    This is a composite MODIS image showing the 'green wave' of spring in North America and sea surface temperature in the ocean, collected over an 8-day period during the first week in April 2000. On land, the darker green pixels show where the most green foliage is being produced due to photosynthetic activity. Yellows on land show where there is little or no productivity and red is a boundary zone. In the ocean, orange and yellows show warmer waters and blues show colder values. (MODIS Data Type: MODIS-PFM)

  1. Spherical harmonic expansion of the Levitus Sea surface topography

    NASA Technical Reports Server (NTRS)

    Engelis, Theodossios

    1987-01-01

    Prior information for the stationary sea surface topography (SST) may be needed in altimetric solutions that intend to simultaneously improve the gravity field and determine the SST. For this purpose the oceanographically derived SST estimates are represented by a spherical harmonic expansion. The spherical harmonic coefficients are computed from a least squares adjustment of the data covering the majority of the oceanic regions of the world. Several tests are made to determine the optimum maximum degree of solution and the best configuration of the geometry of the data in order to obtain a solution that fits the data and also provides a good spectral representation of the SST.

  2. Middle Pliocene sea surface temperatures: A global reconstruction

    USGS Publications Warehouse

    Dowsett, H.; Barron, J.; Poore, R.

    1996-01-01

    Identification and analyses of Pliocene marine microfossils from 64 globally distributed stratigraphic sequences have been used to produce a middle Pliocene sea surface temperature reconstruction of the Earth. This reconstruction shows little or no change from current conditions in low latitude regions and significant warming of the ocean surface at mid and higher latitudes of both hemispheres. This pattern of warming is consistent with terrestrial records and suggests a combination of enhanced meridional ocean heat transport and enhanced greenhouse effect were responsible for the middle Pliocene warmth.

  3. SMOS sea surface salinity maps of the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Gabarro, Carolina; Olmedo, Estrella; Turiel, Antonio; Ballabrera-Poy, Joaquim; Martinez, Justino; Portabella, Marcos

    2016-04-01

    Salinity and temperature gradients drive the thermohaline circulation of the oceans, and play a key role in the ocean-atmosphere coupling. The strong and direct interactions between the ocean and the cryosphere (primarily through sea ice and ice shelves) is also a key ingredient of the thermohaline circulation. The ESA's Soil Moisture and Ocean Salinity (SMOS) mission, launched in 2009, has the objective measuring soil moisture over the continents and sea surface salinity over the oceans. Although the mission was originally conceived for hydrological and oceanographic studies [1], SMOS is also making inroads in the cryospheric monitoring. SMOS carries an innovative L-band (1.4 GHz, or 21-cm wavelength), passive interferometric radiometer (the so-called MIRAS) that measures the electromagnetic radiation emitted by the Earth's surface, at about 50 km spatial resolution wide swath (1200-km), and with a 3-day revisit time at the equator, but a more frequent one at the poles. Although the SMOS radiometer operating frequency offers almost the maximum sensitivity of the brightness temperature (TB) to sea surface salinity (SSS) variations, this is rather low, , i.e.,: 90% of ocean SSS values span a range of brightness temperatures of only 5K at L-band. This sensitivity is particularly low in cold waters. This implies that the SSS retrieval requires high radiometric performance. Since the SMOS launch, SSS Level 3 maps have been distributed by several expert laboratories including the Barcelona Expert Centre (BEC). However, since the TB sensitivity to SSS decreases with decreasing sea surface temperature (SST), large retrieval errors had been reported when retrieving salinity values at latitudes above 50⁰N. Two new processing algorithms, recently developed at BEC, have led to a considerable improvement of the SMOS data, allowing for the first time to derive SSS maps in cold waters. The first one is to empirically characterize and correct the systematic biases with six

  4. Fabrication of Feedhorn-Coupled Transition Edge Sensor Arrays for Measurement of the Cosmic Microwave Background Polarization

    NASA Astrophysics Data System (ADS)

    Denis, K. L.; Ali, A.; Appel, J.; Bennett, C. L.; Chang, M. P.; Chuss, D. T.; Colazo, F. A.; Costen, N.; Essinger-Hileman, T.; Hu, R.; Marriage, T.; Rostem, K.; U-Yen, K.; Wollack, E. J.

    2016-08-01

    Characterization of the minute cosmic microwave background polarization signature requires multi-frequency, high-throughput precision instrument systems. We have previously described the detector fabrication of a 40 GHz focal plane and now describe the fabrication of detector modules for measurement of the CMB at 90 GHz. The 90 GHz detectors are a scaled version of the 40 GHz architecture where, due to smaller size detectors, we have implemented a modular (wafer level) rather than the chip-level architecture. The new fabrication process utilizes the same design rules with the added challenge of increased wiring density to the 74 TES's as well as a new wafer level hybridization procedure. The hexagonally shaped modules are tile-able, and as such can be used to form the large focal planes required for a space-based CMB polarimeter. The detectors described here will be deployed in two focal planes with seven modules each in the Johns Hopkins University led ground-based Cosmology Large Angular Scale Surveyor (CLASS) telescope.

  5. Fabrication of Feedhorn-Coupled Transition Edge Sensor Arrays for Measurement of the Cosmic Microwave Background Polarization

    NASA Astrophysics Data System (ADS)

    Denis, K. L.; Ali, A.; Appel, J.; Bennett, C. L.; Chang, M. P.; Chuss, D. T.; Colazo, F. A.; Costen, N.; Essinger-Hileman, T.; Hu, R.; Marriage, T.; Rostem, K.; U-Yen, K.; Wollack, E. J.

    2015-12-01

    Characterization of the minute cosmic microwave background polarization signature requires multi-frequency, high-throughput precision instrument systems. We have previously described the detector fabrication of a 40 GHz focal plane and now describe the fabrication of detector modules for measurement of the CMB at 90 GHz. The 90 GHz detectors are a scaled version of the 40 GHz architecture where, due to smaller size detectors, we have implemented a modular (wafer level) rather than the chip-level architecture. The new fabrication process utilizes the same design rules with the added challenge of increased wiring density to the 74 TES's as well as a new wafer level hybridization procedure. The hexagonally shaped modules are tile-able, and as such can be used to form the large focal planes required for a space-based CMB polarimeter. The detectors described here will be deployed in two focal planes with seven modules each in the Johns Hopkins University led ground-based Cosmology Large Angular Scale Surveyor (CLASS) telescope.

  6. Study of the blue-green laser scattering from the rough sea surface with foams by the improved two-scale method

    NASA Astrophysics Data System (ADS)

    Li, Xiangzhen; Qi, Xiao; Han, Xiang'e.

    2015-10-01

    The characteristics of laser scattering from sea surface have a great influence on application performance, from submarine communication, laser detection to laser diffusion communication. Foams will appear when the wind speed exceeds a certain value, so the foam can be seen everywhere in the upper layer of the ocean. Aiming at the volume-surface composite model of rough sea surface with foam layer driven by wind, and the similarities and differences of scattering characteristics between blue-green laser and microwave, an improved two-scale method for blue-green laser to calculate the scattering coefficient is presented in this paper. Based on the improved two-scale rough surface scattering theory, MIE theory and VRT( vector radiative transfer ) theory, the relations between the foam coverage of the sea surface and wind speed and air-sea temperature difference are analyzed. Aiming at the Gauss sea surface in blue-green laser, the dependence of back- and bistatie-scattering coefficient on the incident and azimuth angle, the coverage of foams, as well as the wind speed are discussed in detail. The results of numerical simulations are compared and analyzed in this paper. It can be concluded that the foam layer has a considerable effect on the laser scattering with the increase of wind speed, especially for a large incident angle. Theoretical analysis and numerical simulations show that the improved two-scale method is reasonable and efficient.

  7. Microwave radiation force and torque on a disk resonator excited by a circularly polarized plane wave

    NASA Astrophysics Data System (ADS)

    Makarov, S.; Kulkarni, S.

    2004-05-01

    A numerical simulation method [S. Makarov and S. Kulkarni, Appl. Phys. Lett. 84, 1600 (2004)] is used in order to determine the radiation force and radiation torque on a parallel-plate disk resonator, whose size is comparable to wavelength. The method is based on the MOM solution of the electric-field integral equation, accurate calculation of the near field, and removal of the self-interaction terms responsible for the pinch effect. The local force/torque distribution at the normal incidence of a circularly polarized plane wave is found. It is observed that, at the resonance, the individual disks are subject to unexpectedly large local force densities, despite the fact that the net radiation force on the resonator remains very small. On the other hand, the total axial torque on the disk resonator also increases at the resonance.

  8. Velocity profiles inside volcanic clouds from three-dimensional scanning microwave dual-polarization Doppler radars

    NASA Astrophysics Data System (ADS)

    Montopoli, Mario

    2016-07-01

    In this work, velocity profiles within a volcanic tephra cloud obtained by dual-polarization Doppler radar acquisitions with three-dimensional (3-D) mechanical scanning capability are analyzed. A method for segmenting the radar volumes into three velocity regimes: vertical updraft, vertical fallout, and horizontal wind advection within a volcanic tephra cloud using dual-polarization Doppler radar moments is proposed. The horizontal and vertical velocity components within the regimes are retrieved using a novel procedure that makes assumptions concerning the characteristics of the winds inside these regimes. The vertical velocities retrieved are combined with 1-D simulations to derive additional parameters including particle fallout, mass flux, and particle sizes. The explosive event occurred on 23 November 2013 at the Mount Etna volcano (Sicily, Italy), is considered a demonstrative case in which to analyze the radar Doppler signal inside the tephra column. The X-band radar (3 cm wavelength) in the Catania, Italy, airport observed the 3-D scenes of the Etna tephra cloud ~32 km from the volcano vent every 10 min. From the radar-derived vertical velocity profiles of updraft, particle fallout, and horizontal transportation, an exit velocity of 150 m/s, mass flux rate of 1.37 • 107 kg/s, particle fallout velocity of 18 m/s, and diameters of precipitating tephra particles equal to 0.8 cm are estimated on average. These numbers are shown to be consistent with theoretical 1-D simulations of plume dynamics and local reports at the ground, respectively. A thickness of 3 ± 0.36 km for the downwind ash cloud is also inferred by differentiating the radar-derived cloud top and the height of transition between the convective and buoyancy regions, the latter being inferred by the estimated vertical updraft velocity profile. The unique nature of the case study as well as the novelty of the segmentation and retrieval methods presented potentially give new insights into the

  9. A Match-based approach to the estimation of polar stratospheric ozone loss using Aura Microwave Limb Sounder observations

    NASA Astrophysics Data System (ADS)

    Livesey, N. J.; Santee, M. L.; Manney, G. L.

    2015-09-01

    The well-established "Match" approach to quantifying chemical destruction of ozone in the polar lower stratosphere is applied to ozone observations from the Microwave Limb Sounder (MLS) on NASA's Aura spacecraft. Quantification of ozone loss requires distinguishing transport- and chemically induced changes in ozone abundance. This is accomplished in the Match approach by examining cases where trajectories indicate that the same air mass has been observed on multiple occasions. The method was pioneered using ozonesonde observations, for which hundreds of matched ozone observations per winter are typically available. The dense coverage of the MLS measurements, particularly at polar latitudes, allows matches to be made to thousands of observations each day. This study is enabled by recently developed MLS Lagrangian trajectory diagnostic (LTD) support products. Sensitivity studies indicate that the largest influence on the ozone loss estimates are the value of potential vorticity (PV) used to define the edge of the polar vortex (within which matched observations must lie) and the degree to which the PV of an air mass is allowed to vary between matched observations. Applying Match calculations to MLS observations of nitrous oxide, a long-lived tracer whose expected rate of change is negligible on the weekly to monthly timescales considered here, enables quantification of the impact of transport errors on the Match-based ozone loss estimates. Our loss estimates are generally in agreement with previous estimates for selected Arctic winters, though indicating smaller losses than many other studies. Arctic ozone losses are greatest during the 2010/11 winter, as seen in prior studies, with 2.0 ppmv (parts per million by volume) loss estimated at 450 K potential temperature (~ 18 km altitude). As expected, Antarctic winter ozone losses are consistently greater than those for the Arctic, with less interannual variability (e.g., ranging between 2.3 and 3.0 ppmv at 450 K). This

  10. Global interoperability in the oceanographic sea surface temperature community

    NASA Astrophysics Data System (ADS)

    Armstrong, E. M.; Casey, K. S.; Vazquez, J.; Habermann, T.; Bingham, A.; Thompson, C. K.; Donlon, C. J.

    2010-12-01

    The Group for High Resolution Sea Surface Temperature (GHRSST) Project is an international consortium of data providers coordinated across four continents providing sea surface temperature (SST) products from nearly every SST observing satellite in common data and metadata formats since 2005. It currently provides Level 2P data for 13 unique sensors with over 40 combined Level 2, 3 and 4 products. The entire project produces on the order of 35 Gbytes/day and distributes over 3 Tbytes/ month from a variety of access nodes. Although these combined data throughputs are modest by the standards of future NASA Decadal missions, GHRSST has achieved a large measure of success by implementing a regional/global task sharing framework built on self describing data formats, standardized metadata content and data access protocols early in its mission. We will present some of these implementation strategies, lessons learned and history with regard to standardizing products while reducing barriers to interoperability that the project undertook leading up to the present. We will also discuss recent revisions of data and metadata product specifications, and new tools and services that the project will implement in the near future to further reduce barriers, and improve discovery, metadata and access.

  11. Emerita analoga recruit populations and correlations with sea surface temperature

    NASA Astrophysics Data System (ADS)

    Pettway, J.; Quan, H.; Juarez, F.; Vicencio, M.; Ng, N.; Careers in Science Intern Program

    2010-12-01

    The Careers in Science program at the California Academy of Sciences is a science internship for students from groups traditionally under-represented in the sciences. Starting in 2003, interns have participated in the Farallones Marine Sanctuary Association's LiMPETS Sandy Beach Monitoring program, assessing populations of Emerita analoga, the Pacific mole crab. E. analoga, an inhabitant of intertidal swash zones along the coast from Alaska to Baja California, is an important species in the sandy beach intertidal food web. Weekly, during the months of June, July and August, a group of interns go to stairwell 18 of San Francisco’s Ocean Beach in Golden Gate National Recreational Area to systematically collect live E. analoga samples and data. Along a 50 meter sampling area, five transects with ten samples in the swash zone are taken and recorded. Collected E. analoga are sexed (male, female, female w/eggs, and recruit) and measured for carapace size. Newly settled E. analoga (recruit) populations have declined in recent years. However, beginning in 2009, recruit populations began to increase in number, particularly in 2010. Our group hypothesized that this increase in recruitment is correlated with increased sea surface temperature. It has been reported that some planktonic animals become more abundant in warmer waters after a major temperature shift. After examining the data, we did not find a correlation between sea surface temperature and recruit populations, leading us to further questions on the cause of this increase in E. analoga recruits.

  12. Climate modulation on sea surface height in China seas

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaoshuang; Wang, Xidong; Cao, Yingzhi; Zhang, Lianxin; Shao, Caixia; Sun, Chunjian; Wu, Xinrong; Fu, Hongli; Xuan, Lili

    2015-09-01

    The climate modulation on the sea surface height (SSH) in China seas is investigated using a China Ocean Reanalysis (CORA) dataset from 1958-2008. The dataset is constructed by assimilating the temperature/salinity profiles derived from the satellite altimetry data and historical observational temperature/salinity profiles. Based on the Empirical Orthogonal Function (EOF), the CORA sea surface height anomaly (SSHa) is decomposed, and the interannual and decadal variability of the first three leading modes are analyzed. On the interannual timescale, the first principal component (PC1) is significant positively correlated with the El Niño/Southern Oscillation (ENSO). On the decadal timescale, North Pacific Gyre Oscillation (NPGO) has significant negative correlation with PC1 whereas Pacific Decadal Oscillation (PDO) is in phase with PC3. Analysis shows that the decadal variability of SSH is mainly modulated by the wind stress curl variability related to the NPGO and PDO. In addition, the effect of net heat flux associated to the NPGO and PDO on SSH is also investigated, with net heat flux variability in the Luzon strait and tropic Pacific found to influence the decadal variability of SSH.

  13. Joint variability of global runoff and global sea surface temperatures

    USGS Publications Warehouse

    McCabe, G.J.; Wolock, D.M.

    2008-01-01

    Global land surface runoff and sea surface temperatures (SST) are analyzed to identify the primary modes of variability of these hydroclimatic data for the period 1905-2002. A monthly water-balance model first is used with global monthly temperature and precipitation data to compute time series of annual gridded runoff for the analysis period. The annual runoff time series data are combined with gridded annual sea surface temperature data, and the combined dataset is subjected to a principal components analysis (PCA) to identify the primary modes of variability. The first three components from the PCA explain 29% of the total variability in the combined runoff/SST dataset. The first component explains 15% of the total variance and primarily represents long-term trends in the data. The long-term trends in SSTs are evident as warming in all of the oceans. The associated long-term trends in runoff suggest increasing flows for parts of North America, South America, Eurasia, and Australia; decreasing runoff is most notable in western Africa. The second principal component explains 9% of the total variance and reflects variability of the El Ni??o-Southern Oscillation (ENSO) and its associated influence on global annual runoff patterns. The third component explains 5% of the total variance and indicates a response of global annual runoff to variability in North Aflantic SSTs. The association between runoff and North Atlantic SSTs may explain an apparent steplike change in runoff that occurred around 1970 for a number of continental regions.

  14. Microstrip Antenna for Remote Sensing of Soil Moisture and Sea Surface Salinity

    NASA Technical Reports Server (NTRS)

    Ramhat-Samii, Yahya; Kona, Keerti; Manteghi, Majid; Dinardo, Steven; Hunter, Don; Njoku, Eni; Wilson, Wiliam; Yueh, Simon

    2009-01-01

    This compact, lightweight, dual-frequency antenna feed developed for future soil moisture and sea surface salinity (SSS) missions can benefit future soil and ocean studies by lowering mass, volume, and cost of the antenna system. It also allows for airborne soil moisture and salinity remote sensors operating on small aircraft. While microstrip antenna technology has been developed for radio communications, it has yet to be applied to combined radar and radiometer for Earth remote sensing. The antenna feed provides a key instrument element enabling high-resolution radiometric observations with large, deployable antennas. The design is based on the microstrip stacked-patch array (MSPA) used to feed a large, lightweight, deployable, rotating mesh antenna for spaceborne L-band (approximately equal to 1 GHz) passive and active sensing systems. The array consists of stacked patches to provide dual-frequency capability and suitable radiation patterns. The stacked-patch microstrip element was designed to cover the required L-band center frequencies at 1.26 GHz (lower patch) and 1.413 GHz (upper patch), with dual-linear polarization capabilities. The dimension of patches produces the required frequencies. To achieve excellent polarization isolation and control of antenna sidelobes for the MSPA, the orientation of each stacked-patch element within the array is optimized to reduce the cross-polarization. A specialized feed-distribution network was designed to achieve the required excitation amplitude and phase for each stacked-patch element.

  15. Microwave Radiometers from 0.6 to 22 GHz for Juno, a Polar Orbiter around Jupiter

    NASA Technical Reports Server (NTRS)

    P. Pingree; Janssen, M.; Oswald, J.; Brown, S.; Chen, J.; Hurst, K.; Kitiyakara, A.; Maiwald, F.; Smith, S.

    2008-01-01

    A compact radiometer instrument is under development at JPL for Juno, the next NASA New Frontiers mission, scheduled to launch in 2011. This instrument is called the MWR (MicroWave Radiometer), and its purpose is to measure the thermal emission from Jupiter's atmosphere at selected frequencies from 0.6 to 22 GHz. The objective is to measure the distributions and abundances of water and ammonia in Jupiter's atmosphere, with the goal of understanding the previously unobserved dynamics of the subcloud atmosphere, and to discriminate among models for planetary formation in our solar system. The MWR instrument is currently being developed to address these science questions for the Juno mission. As part of a deep space mission aboard a solar-powered spacecraft, MWR is designed to be compact, lightweight, and low power. The entire MWR instrument consists of six individual radiometer channels with approximately 4% bandwidth at 0.6, 1.25,2.6,5.2, 10,22 GHz operating in direct detection mode. Each radiometer channel has up to 80 dB of gain with a noise figure of several dB. The highest frequency channel uses a corrugated feedhorn and waveguide transmission lines, whereas all other channels use highly phase stable coaxial cables and either patch array or waveguide slot array antennas. Slot waveguide array antennas were chosen for the low loss at the next three highest frequencies and patch array antennas were implemented due to the mass constraint at the two lowest frequencies. The six radiometer channels receive their voltage supplies and control lines from an electronics unit that also provides the instrument communication interface to the Juno spacecraft. For calibration purposes each receiver has integrated noise diodes, a Dicke switch, and temperature sensors near each component that contributes to the noise figure. In addition, multiple sensors will be placed along the RF transmission lines and the antennas in order to measure temperature gradients. All antennas and RF

  16. Large Antenna Multifrequency Microwave Radiometer (LAMMR) system design

    NASA Technical Reports Server (NTRS)

    King, J. L.

    1980-01-01

    The large Antenna Multifrequency Microwave Radiometer (LAMMR) is a high resolution 4 meter aperture scanning radiometer system designed to determine sea surface temperature and wind speed, atmospheric water vapor and liquid water, precipitation, and various sea ice parameters by interpreting brightness temperature images from low Earth orbiting satellites. The LAMMR with dual linear horizontal and vertical polarization radiometer channels from 1.4 to 91 GHZ can provide multidiscipline data with resolutions from 105 to 7 km. The LAMMR baseline radiometer system uses total power radiometers to achieve delta T's in the 0.5 to 1.7 K range and system calibration accuracies in the 1 to 2 deg range. A cold sky horn/ambient load two point calibration technique is used in this baseline concept and the second detector output uses an integrated and dump circuit to sample the scanning cross-tract resolution cells.

  17. Persistence of Rainfall Imprint on SMOS Sea Surface Salinity

    NASA Astrophysics Data System (ADS)

    Boutin, Jacqueline; Reverdin, Gilles; Martin, Nicolas

    2015-04-01

    The Soil Moisture and Ocean Salinity (SMOS) satellite mission monitors sea surface salinity (SSS) over the global ocean for more than 5 years. In previous studies, Boutin et al. (2014) have shown a clear freshening of SMOS SSS under rain cells of about -0.14pss/mm/hr at moderate wind speed (3-12m/s). This order of magnitude is compatible with in situ drifters observations taken at 45cm depth while SMOS SSS are at about 1cm depth and at a mean spatial resolution of 43km. Using Aquarius satellite SSS, Meissner and Wentz (2014) found a SSS decrease under rain cells of -0.12pss/mm/hr at 7 m/s wind speed, consistent with SMOS estimate considering the lower spatial resolution of Aquarius SSS (about 150km); Santos-Garcia et al. (2014) found an influence of the rain history preceding by a few hours the Aquarius measurement. In most cases, drifters observations also suggest that about half of the freshening observed locally disappears after one hour, likely because of mixing with surrounding waters. In this presentation, we will investigate the temporal and spatial evolution of SMOS SSS after a rain event. Rainfall information will be either derived from SSM/Is measurements (during periods when three SSM/Is satellites provide adequate sampling before and simultaneous to SMOS measurements) or from the NOAA CMORPH products. In order to separate instantaneous from historical effects, we distinguish two cases: 1) rainfall occurs at less than 30mn from SMOS observation but no rain occurred before; 2) rainfall occurred previous to SMOS observation (up to 3 hours before) but has stopped at least 30mn before SMOS acquisition. In addition to looking at the temporal evolution of SMOS SSS under the rain cell, since both vertical mixing and horizontal stirring may occur, we also investigate the size of the fresh SSS region relative to the size of the rain cell. Boutin, J., N. Martin, G. Reverdin, S. Morisset, X. Yin, L. Centurioni, and N. Reul (2014), Sea surface salinity under rain

  18. Sea Surface Salinity and Ocean Color Observations in the Northern Gulf

    NASA Astrophysics Data System (ADS)

    Wesson, J. C.; Burrage, D. M.; Wang, D. W.; Howden, S. D.

    2012-04-01

    Airborne mapping of Sea Surface Salinity (SSS) has been performed using L-Band radiometers for over 15 years, and has been operationally practical for over a decade. Ocean scale L-band observations of SSS are now obtained by satellite. ESA's SMOS has been operational for over two years and NASA's Aquarius satellite, launched in Jun, 2011, for over 6 months. Aircraft SSS complements satellite measurements by measuring nearer to coasts and with finer (˜1 km) spatial resolution. Due to the large effective pixel size of the satellite L-Band SSS measurements(˜35-80km), SMOS measurements do not reach the coast. Land microwave brightness signal in a given pixel contaminates the measurement of sea surface brightness temperature. However, the high signal to noise ratio (salinity contrast of 7-15 psu over 10km in some cases) of the coastal salinity signal, due to large freshwater sources, may dominate land contamination effects, to allow closer than usual SMOS SSS observations of strong coastal salinity patterns. An additional method to estimate SSS near coasts is using ocean color. Very near to coasts, freshwater sources such as rivers are relatively rich in Colored Dissolved Organic Matter (CDOM). As freshwater mixes with saltwater, salinity increases and CDOM concentrations fall. For conservative mixing, there is an inverse linear relation between CDOM and salinity, allowing estimates of SSS based on CDOM. The airborne sensors we use during STARRS flights include 2 SeaWifs airborne simulator sensors, one upward looking and one downward looking, as well as digital cameras, which we have used to identify color fronts. These provide ocean color measurements in addition to the STARRS microwave SSS measurements. We present results from an airborne campaign in the northern Gulf of Mexico, June 2-13, 2011. We made four types of flights. 1) Underflights of SMOS tracks at times coincident with SMOS passes. 2) Zig-zag flights along the coast, between Texas and Mississippi. 3

  19. Variability of Sea Surface Temperature Response to Tropical Cyclones along the NEC Bifurcation Latitude

    NASA Astrophysics Data System (ADS)

    Fernandez, I.; Villanoy, C. L.

    2013-12-01

    The east of the Philippines serves as an entry point to an annual average of 20 tropical cyclones. The ocean is dynamic where the North Equatorial Current (NEC) bifurcates into the Kurushio Current to the north and Mindanao Current to the south. The displacement and intensity of NEC bifurcation in the region varies seasonally and interannually driven by local monsoons and ENSO. The variability of the NEC bifurcation latitude may alter the origins of the Kuroshio and modify the sea surface temperature field, which can alter the strength of the typhoons and upper ocean response. This paper aims to characterize the variability of Sea Surface Temperature (SST) Response to Tropical Cyclones along with the NEC Bifurcation latitude using daily merged product of the TRMM Microwave Imager (TMI) and Advanced Microwave Scanning Radiometer (AMSR-E), Sea Surface Height (SSH) and SSH Anomaly (SSHA) from AVISO and background climatological D26 (depth of 26 °C) and T100 (depth integrated temperature up to 100 meters) from ARGO profiles and CTD data from WOA09 from 2003 to 2012. SSH measurements from this period were used as a proxy for determining the bifurcation latitude (YB). Characteristics of the meridional distribution from 0° to 30°N of D26 is homogenous along 10-15°N. Monthly mean D26 along 10-15°N, 125-145°E shows high correlation with YB . Variations of the D26 and T100 showed deepening and warming along with YB. Two regions were derived from meridional distribution of T100 namely BSouth (<15°N) where background climatological condition is warm all throughout the year with deep D26 and BNorth (>15°N), where background climatological condition is shallow (D26) and varies seasonally. These regions where used to compare variability with respect to SST recovery time and the SST maximum change (ΔSSTmax) along with other factors such as TCs translation speed (TS) and intensity based on the Saffir-Simpson Hurricane Scale. Results showed that in both regions SST Recovery

  20. Modulation of cosmic microwave background polarization with a warm rapidly rotating half-wave plate on the Atacama B-Mode Search instrument.

    PubMed

    Kusaka, A; Essinger-Hileman, T; Appel, J W; Gallardo, P; Irwin, K D; Jarosik, N; Nolta, M R; Page, L A; Parker, L P; Raghunathan, S; Sievers, J L; Simon, S M; Staggs, S T; Visnjic, K

    2014-02-01

    We evaluate the modulation of cosmic microwave background polarization using a rapidly rotating, half-wave plate (HWP) on the Atacama B-Mode Search. After demodulating the time-ordered-data (TOD), we find a significant reduction of atmospheric fluctuations. The demodulated TOD is stable on time scales of 500-1000 s, corresponding to frequencies of 1-2 mHz. This facilitates recovery of cosmological information at large angular scales, which are typically available only from balloon-borne or satellite experiments. This technique also achieves a sensitive measurement of celestial polarization without differencing the TOD of paired detectors sensitive to two orthogonal linear polarizations. This is the first demonstration of the ability to remove atmospheric contamination at these levels from a ground-based platform using a rapidly rotating HWP. PMID:24593374

  1. Satellite-Derived Sea Surface Temperature: Workshop 3

    NASA Technical Reports Server (NTRS)

    1985-01-01

    This is the third of a series of three workshops, sponsored by the National Aeronautics and Space Administration, to investigate the state of the art in global sea surface temperature measurements from space. Three workshops were necessary to process and analyze sufficient data from which to draw conclusions on the accuracy and reliability of the satellite measurements. In this workshop, the final two (out of a total of four) months of satellite and in situ data chosen for study were processed and evaluated. Results from the AVHRR, HIRS, SMMR, and VAS sensors, in comparison with in situ data from ships, XBTs, and buoys, confirmed satellite rms accuracies in the 0.5 to 1.0 C range, but with variable biases. These accuracies may degrade under adverse conditions for specific sensors. A variety of color maps, plots, and statistical tables are provided for detailed study of the individual sensor SST measurements.

  2. Improved accuracy of the remote sensing of sea surface temperature

    NASA Technical Reports Server (NTRS)

    Dalu, G.; Prabhakara, C.; Lo, R. C.

    1981-01-01

    A method is described for determining the water vapor content to within + or - 0.4 g/sq cm from remotely sensed radiances in three infrared channels, 11, 13, 18 microns. Using this method, it is possible to significantly improve the accuracy of sea surface temperature (SST) over what is obtainable with the two channel technique. A radiative computational scheme for the radiative transfer equation is used to study the manner in which the equivalent radiative temperature of the atmosphere changes as a function of wave number for different atmospheric conditions. Average climatological conditions are used to simulate the radiative response of the atmosphere. This radiative transfer simulation is used to compute brightness temperatures for radiosonde profiles obtained from oceanographic ships, which temperatures are in turn used to estimate the SST. Nimbus 4 IRIS spectral measurements corresponding to the profiles were used in the same way for purposes of comparison.

  3. Microbial community genomics in eastern Mediterranean Sea surface waters.

    PubMed

    Feingersch, Roi; Suzuki, Marcelino T; Shmoish, Michael; Sharon, Itai; Sabehi, Gazalah; Partensky, Frédéric; Béjà, Oded

    2010-01-01

    Offshore waters of the eastern Mediterranean Sea are one of the most oligotrophic regions on Earth in which the primary productivity is phosphorus limited. To study the unexplored function and physiology of microbes inhabiting this system, we have analyzed a genomic library from the eastern Mediterranean Sea surface waters by sequencing both termini of nearly 5000 clones. Genome recruitment strategies showed that the majority of high-scoring pairs corresponded to genomes from the Alphaproteobacteria (SAR11-like and Rhodobacterales), Cyanobacteria (Synechococcus and high-light adapted Prochlorococcus) and diverse uncultured Gammaproteobacteria. The community structure observed, as evaluated by both protein similarity scores or metabolic potential, was similar to that found in the euphotic zone of the ALOHA station off Hawaii but very different from that of deep aphotic zones in both the Mediterranean Sea and the Pacific Ocean. In addition, a strong enrichment toward phosphate and phosphonate uptake and utilization metabolism was also observed. PMID:19693100

  4. Sensitivity of tropical cyclone intensity to sea surface temperature

    SciTech Connect

    Evans, J.L. )

    1993-06-01

    Increased occurrence of more intense tropical storms intruding further poleward has been foreshadowed as one of the potential consequences of global warming. This scenario is based almost entirely on the general circulation model predictions of warmer sea surface temperature (SST) with increasing levels of atmospheric CO[sub 2] and some theories of tropical cyclone intensification that support the notion of more intense systems with warmer SST. Whether storms are able to achieve this theoretically determined more intense state depends on whether the temperature of the underlying water is the dominant factor in tropical cyclone intensification. An examination of the historical data record in a number of ocean basins is used to identify the relative importance of SST in the tropical cyclone intensification process. The results reveal that SST alone is an inadequate predictor of tropical cyclone intensity. Other factors known to affect tropical cyclone frequency and intensity are discussed. 16 refs., 6 figs., 3 tabs.

  5. Sea surface: fate and biological effects of mixed contaminants

    SciTech Connect

    Hardy, J.T.; Crecelius, E.A.; Long, E.; Kiesser, S.L.; Stubin, A.I.; Gurtisen, J.M.; Apts, C.W.

    1985-09-01

    This research on the microlayer (upper 50 micrometers of the sea surface) confirms that many contaminants partition at this interface. High concentrations of polynuclear aromatic and chlorinated hydrocarbons were found in the microlayer of urban bays in Puget Sound. In some cases, concentrations exceeded water quality criteria by several orders of magnitude. At the same sites, subsurface bulk water showed no detectable contamination. Fertilized neustonic eggs of sand sole (Psettichthys melanostictus), were exposed to collected microlayer samples during their first week of embryonic and larval development. Compared to the rural site and/or central Puget Sound, exposure of embryos to microlayer from several urban bay sites resulted in delayed hatching, increased embryo mortality, and kyphosis (bent spine abnormalities) in hatched larvae. 28 refs., 2 figs., 4 tabs.

  6. Eddies contribute to striations in sea surface topography

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2013-03-01

    Scientists recently observed striations in sea surface topography in all ocean basins. These striations appear as alternating mesoscale jet-like structures; they have speeds on the order of 1 centimeter per second and are typically separated by about 200 kilometers in the meridional direction. The cause of these striations has been debated. Contributing to this scientific discussion, Buckingham and Cornillon used a database of tracked eddies and a contour identification and eddy removal algorithm to show that eddies are a significant source of striations. The authors noted that a small portion of the energy was unaccounted for by propagating eddies, allowing for the existence of weak zonal flows. (Journal of Geophysical Research-Oceans, doi:10.1029/2012JC008231, 2013)

  7. Tropical cyclone rainfall area controlled by relative sea surface temperature

    PubMed Central

    Lin, Yanluan; Zhao, Ming; Zhang, Minghua

    2015-01-01

    Tropical cyclone rainfall rates have been projected to increase in a warmer climate. The area coverage of tropical cyclones influences their impact on human lives, yet little is known about how tropical cyclone rainfall area will change in the future. Here, using satellite data and global atmospheric model simulations, we show that tropical cyclone rainfall area is controlled primarily by its environmental sea surface temperature (SST) relative to the tropical mean SST (that is, the relative SST), while rainfall rate increases with increasing absolute SST. Our result is consistent with previous numerical simulations that indicated tight relationships between tropical cyclone size and mid-tropospheric relative humidity. Global statistics of tropical cyclone rainfall area are not expected to change markedly under a warmer climate provided that SST change is relatively uniform, implying that increases in total rainfall will be confined to similar size domains with higher rainfall rates. PMID:25761457

  8. Sea surface temperature contributes to marine crocodylomorph evolution.

    PubMed

    Martin, Jeremy E; Amiot, Romain; Lécuyer, Christophe; Benton, Michael J

    2014-01-01

    During the Mesozoic and Cenozoic, four distinct crocodylomorph lineages colonized the marine environment. They were conspicuously absent from high latitudes, which in the Mesozoic were occupied by warm-blooded ichthyosaurs and plesiosaurs. Despite a relatively well-constrained stratigraphic distribution, the varying diversities of marine crocodylomorphs are poorly understood, because their extinctions neither coincided with any major biological crises nor with the advent of potential competitors. Here we test the potential link between their evolutionary history in terms of taxic diversity and two abiotic factors, sea level variations and sea surface temperatures (SST). Excluding Metriorhynchoidea, which may have had a peculiar ecology, significant correlations obtained between generic diversity and estimated Tethyan SST suggest that water temperature was a driver of marine crocodylomorph diversity. Being most probably ectothermic reptiles, these lineages colonized the marine realm and diversified during warm periods, then declined or became extinct during cold intervals. PMID:25130564

  9. Mean sea surface and gravity investigations using TOPEX/Poseidon altimeter data

    NASA Technical Reports Server (NTRS)

    Rapp, Richard H.

    1991-01-01

    From a broad point of view, we will be concerned with studying global ocean circulation patterns on the basis of ocean surface determinations with geoid undulation information. In addition, we will study local variations of the gravity field implied by the altimeter data. These general goals are reflected in the title of our investigation. To meet our general goal, we have defined a number of specific objectives: (1) sea surface topography representation; (2) mean sea surface determination; (3) development of local geoid models; (4) mean sea surface comparisons; (5) sea surface topographic files; and (6) gravity anomaly determination.

  10. Diatom and Geochemical Constraints on Pliocene Sea Surface Conditions on the Wilkes Land Margin, East Antarctica

    NASA Astrophysics Data System (ADS)

    Riesselman, C. R.; Taylor-Silva, B.

    2015-12-01

    The mid-Pliocene is the most recent interval in Earth's history to sustain global temperatures within the range of warming predicted for the 21st century, providing an appealing analog with which to examine the changes we might encounter in the coming century. Diatom-based Southern Ocean sea surface and sea ice reconstructions by the USGS Pliocene Research Interpretations and Synoptic Mapping (PRISM) Group suggest an average +2° summer SST anomaly during the 3.3-3.0 Ma interval relative to modern. Here, we present a reconstruction of Pliocene sea surface conditions from a marine sediment core collected at IODP Site U1361, on the continental rise of the Wilkes Land margin. U1361 biogenic silica concentrations document the alternation of diatom-rich and diatom-poor lithologies; we interpret 8 diatom-rich mudstones within this sequence to record interglacial conditions between 3.8 and 2.8 Ma, across the transition from obliquity control to precession control on East Antarctic ice volumes. This progression also preserves 3 packages of interglacial sediments within the 3.3-3.0 PRISM interval, providing an opportunity for direct comparison to proximal PRISM site Eltanin 50-28. Diatom assemblages in both cores are characterized by Fragilariopsis barronii and Rouxia antarctica, extinct species with an inferred ecological preference for waters south of the polar front. However F. weaveri, an extinct diatom with inferred preference for more northerly waters and moderate abundance in E50-28, has not been identified at U1361. This may indicate that the polar frontal zone migrated across E50-28 (62° 54'S) but remained north of U1361 (64° 25'S) during the mid-Pliocene. This interpretation is bolstered by the low abundance of extant polar front species (e.g., Thalassiosira oliverana, T. lentiginosa) at U1361; these diatoms dominate the E50-28 assemblage. In contrast, the U1361 assemblage includes a number of extant sea ice indicators (F. sublinearis, F. curta, Chaetoceros

  11. Albatrosses as Ocean Samplers of Sea Surface Temperature

    NASA Astrophysics Data System (ADS)

    Shaffer, S. A.; Kappes, M.; Tremblay, Y.; Costa, D. P.; Weber, R.; Weimerskirch, H.

    2006-12-01

    Albatrosses are unique ocean voyagers because they range so widely and travel at speeds exceeding 90 km per hour. Because they can integrate vast areas of open-ocean, albatrosses are ideal ocean samplers. Between 2003 and 2005 breeding seasons, 21 Laysan and 15 black-footed albatrosses (body mass 2.5 to 3.5 kg) were equipped with 6 g leg-mounted geolocation archival data loggers at Tern Island, French Frigate Shoals, Northwest Hawaiian Islands. The tags sampled environmental temperatures every 480 or 540 s and provided a single location per day for the duration of deployment. Whenever an albatross landed on the sea surface to feed or rest, the tag sampled sea surface temperature (SST). After nearly one year of deployment, 31 albatrosses were recaptured and 29 tags provided complete records. A total of 377,455 SST readings were obtained over 7,360 bird-days at sea. Given the location errors in the geolocation methodology (200 km) and the lack of temporal resolution (1 location per day), the SST measurements can only be used to characterize broad-scale correlates between albatross distribution and the ocean environment. However, in February 2006, we deployed 45 g GPS data loggers on 10 breeding albatrosses for 2-4 day deployments. The GPS loggers were attached to feathers on the albatrosses backs, they sampled every 10 s, and were accurate to within 10 m. One albatross was also equipped with the same leg-mounted archival tag that sampled SST every 8 s. This albatross collected 6,289 SST measurements with complementary GPS quality locations in 3 days at sea. These results highlight the efficacy of albatrosses as ocean samplers. Given that Laysan and black- footed albatrosses range throughout the North Pacific Ocean, it is conceivable that these seabirds could someday become sentinels of changing oceanic conditions. Moreover, these technologies provide exciting new information about the oceanic habitats of North Pacific albatrosses.

  12. Microhydrodynamics of flotation processes in the sea surface layer

    NASA Astrophysics Data System (ADS)

    Grammatika, Marianne; Zimmerman, William B.

    2001-10-01

    The uppermost surface of the ocean forms a peculiarly important ecosystem, the sea surface microlayer (SML). Comprising the top 1-1000 μm of the ocean surface, the SML concentrates many chemical substances, particularly those that are surface active. Important economically as a nursery for fish eggs and larvae, the SML unfortunately is also especially vulnerable to pollution. Contaminants that settle out from the air, have low solubility, or attach to floatable matter tend to accumulate in the SML. Bubbles contribute prominently to the dynamics of air-sea exchanges, playing an important role in geochemical cycling of material in the upper ocean and SML. In addition to the movement of bubbles, the development of a bubble cloud interrelates with the single particle dynamics of all other bubbles and particles. In the early sixties, several in situ oceanographic techniques revealed an "unbelievably immense" number of coastal bubbles of radius 15-300 μm. The spatial and temporal variation of bubble numbers were studied; acoustical oceanographers now use bubbles as tracers to determine ocean processes near the ocean surface. Sea state and rain noises have both been definitively ascribed to the radiation from huge numbers of infant micro bubbles [The Acoustic Bubble. Academic Press, San Diego]. Our research programme aims at constructing a hydrodynamic model for particle transport processes occurring at the microscale, in multi-phase flotation suspensions. Current research addresses bubble and floc microhydrodynamics as building blocks for a microscale transport model. This paper reviews sea surface transport processes in the microlayer and the lower atmosphere, and identifies those amenable to microhydrodynamic modelling and simulation. It presents preliminary simulation results including the multi-body hydrodynamic mobility functions for the modelling of "dynamic bubble filters" and floc suspensions. Hydrodynamic interactions versus spatial anisotropy and size of

  13. A high-resolution global sea surface temperature climatology

    SciTech Connect

    Reynolds, R.W.; Smith, T.M.

    1995-06-01

    In response to the development of a new higher-resolution sea surface temperature (SST) analysis at the National Meteorological Center (NMC), a new monthly 1{degrees} global sea surface temperature climatology was constructed from two intermediate climatologies: the 2{degrees} SST climatology used a 30-yr 1950-1979 base period between roughly 40{degrees}S and 60{degrees}N based on in situ (ship and buoy) SST data supplemented by four years (1982-1985) of satellite SST retrievals, and sea-ice coverage data over a 12-yr period (1982-1993). The final climatology was combined from these two products so that a 1{degrees} resolution was maintained and the base period was adjusted to the 1950-1979 period wherever possible (approximately between 40{degrees}S and 60{degrees}N). Compared to the 2{degrees} climatology, the 1{degrees} climatology resolves equatorial upwelling and fronts much better. This leads to a better matching of the scales of the new analysis and climatology. In addition, because the magnitudes of large-scale features are consistently maintained in both the older 2{degrees} and the new 1{degrees} climatologies, climate monitoring of large-scale anomalies will be minimally affected by the analysis change. The use of 12 years of satellite SST retrievals makes this new climatology useful for many additional purposes because its effective resolution actually approaches 1{degrees} everywhere over the global ocean and because the mean SST values are more accurate south of 40{degrees}S than climatologies without these data. 12 refs., 16 figs.

  14. Evaporation and solar irradiance as regulators of sea surface temperature in annual and interannual changes

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy; Zhang, Anzhen; Bishop, James K. B.

    1994-01-01

    Seven years of net surface solar irradiance (S) derived from cloud information provided by the International Satellite Cloud Climatology Project (ISCCP) and 4 years of surface latent heat flux (E) derived from the observations of the special sensor microwave imager (SSM/I) were used to examine the relation between surface heat fluxes and sea surface temperature (T(sub s)) in their global geographical distribution, seasonal cycle, and interannual variation. The relations of seasonal changes imply that evaporation cooling is significant over most of the ocean and that solar heating is the main drive for the change of T(sub s) away from the equatorial wave guide where ocean dynamics may be more important. However, T(sub s) is not the most direct and significant factor in the seasonal changes of S and E over most of the ocean; the solar incident angle may be more important to S, and wind speed and air humidity are found to correlate better with E. Significant local correlations between anomalies of T(sub s) and S and between anomalies of T(sub s) and E are found in the central equatorial Pacific; both types of correlation are negative. The influence of ocean dynamics in changing T(sub s) in the tropical ocean cannot be ignored.

  15. Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves

    SciTech Connect

    Thurber, Kent R. Tycko, Robert

    2014-05-14

    We report solid state {sup 13}C and {sup 1}H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, {sup 1}H and cross-polarized {sup 13}C NMR signals from {sup 15}N,{sup 13}C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T{sub 1e} is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations.

  16. Perturbation of nuclear spin polarizations in solid state NMR of nitroxide-doped samples by magic-angle spinning without microwaves

    PubMed Central

    Thurber, Kent R.; Tycko, Robert

    2014-01-01

    We report solid state 13C and 1H nuclear magnetic resonance (NMR) experiments with magic-angle spinning (MAS) on frozen solutions containing nitroxide-based paramagnetic dopants that indicate significant perturbations of nuclear spin polarizations without microwave irradiation. At temperatures near 25 K, 1H and cross-polarized 13C NMR signals from 15N,13C-labeled L-alanine in trinitroxide-doped glycerol/water are reduced by factors as large as six compared to signals from samples without nitroxide doping. Without MAS or at temperatures near 100 K, differences between signals with and without nitroxide doping are much smaller. We attribute most of the reduction of NMR signals under MAS near 25 K to nuclear spin depolarization through the cross-effect dynamic nuclear polarization mechanism, in which three-spin flips drive nuclear polarizations toward equilibrium with spin polarization differences between electron pairs. When T1e is sufficiently long relative to the MAS rotation period, the distribution of electron spin polarization across the nitroxide electron paramagnetic resonance lineshape can be very different from the corresponding distribution in a static sample at thermal equilibrium, leading to the observed effects. We describe three-spin and 3000-spin calculations that qualitatively reproduce the experimental observations. PMID:24832263

  17. Correcting infrared satellite estimates of sea surface temperature for atmospheric water vapor attenuation

    NASA Technical Reports Server (NTRS)

    Emery, William J.; Yu, Yunyue; Wick, Gary A.; Schluessel, Peter; Reynolds, Richard W.

    1994-01-01

    A new satellite sea surface temperature (SST) algorithm is developed that uses nearly coincident measurements from the microwave special sensor microwave imager (SSM/I) to correct for atmospheric moisture attenuation of the infrared signal from the advanced very high resolution radiometer (AVHRR). This new SST algorithm is applied to AVHRR imagery from the South Pacific and Norwegian seas, which are then compared with simultaneous in situ (ship based) measurements of both skin and bulk SST. In addition, an SST algorithm using a quadratic product of the difference between the two AVHRR thermal infrared channels is compared with the in situ measurements. While the quadratic formulation provides a considerable improvement over the older cross product (CPSST) and multichannel (MCSST) algorithms, the SSM/I corrected SST (called the water vapor or WVSST) shows overall smaller errors when compared to both the skin and bulk in situ SST observations. Applied to individual AVHRR images, the WVSST reveals an SST difference pattern (CPSST-WVSST) similar in shape to the water vapor structure while the CPSST-quadratic SST difference appears unrelated in pattern to the nearly coincident water vapor pattern. An application of the WVSST to week-long composites of global area coverage (GAC) AVHRR data demonstrates again the manner in which the WVSST corrects the AVHRR for atmospheric moisture attenuation. By comparison the quadratic SST method underestimates the SST corrections in the lower latitudes and overestimates the SST in th e higher latitudes. Correlations between the AVHRR thermal channel differences and the SSM/I water vapor demonstrate the inability of the channel difference to represent water vapor in the midlatitude and high latitudes during summer. Compared against drifting buoy data the WVSST and the quadratic SST both exhibit the same general behavior with the relatively small differences with the buoy temperatures.

  18. Middle Jurassic-Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Jenkyns, H. C.; Schouten-Huibers, L.; Schouten, S.; Sinninghe Damsté, J. S.

    2011-04-01

    Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed during the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of isotopic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEX86 back to the middle Jurassic indicates that relatively warm sea-surface conditions (26-30 °C) existed from this interval (~160 Ma) to the Early Cretaceous (~115 Ma) in the Southern Ocean. The Jurassic and Cretaceous "cold snaps" represent falls of only a few degrees. Belemnite δ18O data give palaeotemperatures that are consistently lower by ~14 °C than does TEX86 and these molluscs likely record conditions below the thermocline. Such long-term warm climatic conditions would only be compatible with the existence of continental ice if appreciable areas of high altitude existed on Antarctica, and/or in other polar regions, during the Mesozoic Era.

  19. Effect of recent sea surface temperature trends on the Arctic stratospheric vortex

    NASA Astrophysics Data System (ADS)

    Garfinkel, C. I.; Hurwitz, M. M.; Oman, L. D.

    2015-06-01

    Comprehensive chemistry-climate model experiments and observational data are used to show that up to half of the satellite era early springtime cooling trend in the Arctic lower stratosphere was caused by changing sea surface temperatures (SSTs). An ensemble of experiments forced only by changing SSTs is compared to an ensemble of experiments in which both the observed SSTs and chemically and radiatively active trace species are changing. By comparing the two ensembles, it is shown that warming of Indian Ocean, North Pacific, and North Atlantic SSTs and cooling of the tropical Pacific have strongly contributed to recent polar stratospheric cooling in late winter and early spring. When concentrations of ozone-depleting substances and greenhouse gases are fixed, polar ozone concentrations show a small but robust decline due to changing SSTs. Ozone loss is larger in the presence of changing concentrations of ozone-depleting substances and greenhouse gases. The stratospheric changes can be understood by examining the tropospheric height and heat flux anomalies generated by the anomalous SSTs. Finally, recent SST changes have contributed to a decrease in the frequency of late winter stratospheric sudden warmings.

  20. Estimating sea surface salinity in coastal waters of the Gulf of Mexico using visible channels on SNPP-VIIRS

    NASA Astrophysics Data System (ADS)

    Vandermeulen, Ryan A.; Arnone, Robert; Ladner, Sherwin; Martinolich, Paul

    2014-05-01

    Sea surface salinity is determined using the visible channels from the Visual Infrared Imaging Radiometer Suite (VIIRS) to derive regional algorithms for the Gulf of Mexico by normalizing to seasonal river discharge. The dilution of river discharge with open ocean waters and the surface salinity is estimated by tracking the surface spectral signature. The water leaving radiances derived from atmospherically-corrected and calibrated 750-m resolution visible M-bands (410, 443, 486, 551, 671 nm) are applied to bio-optical algorithms and subsequent multivariate statistical methods to derive regional empirical relationships between satellite radiances and surface salinity measurements. Although radiance to salinity is linked to CDOM dilution, we explored alternative statistical relationships to account for starting conditions. In situ measurements are obtained from several moorings spread across the Mississippi Sound and Mobile Bay, with a salinity range of 0.1 - 33. Data were collected over all seasons in the year 2013 in order to assess inter-annual variability. The seasonal spectral signatures at the river mouth were used to track the fresh water end members and used to develop a seasonal slope and bias between salinity and radiance. Results show an increased spatial resolution for remote detection of coastal sea surface salinity from space, compared to the Aquarius Microwave salinity. Characterizing the coastal surface salinity has a significant impact on the physical circulation which affects the coastal ecosystems. Results identify locations and dissipation of the river plumes and can provide direct data for assimilation into physical circulation models.

  1. Global monthly sea surface nitrate fields estimated from remotely sensed sea surface temperature, chlorophyll, and modeled mixed layer depth

    NASA Astrophysics Data System (ADS)

    Arteaga, Lionel; Pahlow, Markus; Oschlies, Andreas

    2015-02-01

    Information about oceanic nitrate is crucial for making inferences about marine biological production and the efficiency of the biological carbon pump. While there are no optical properties that allow direct estimation of inorganic nitrogen, its correlation with other biogeochemical variables may permit its inference from satellite data. Here we report a new method for estimating monthly mean surface nitrate concentrations employing local multiple linear regressions on a global 1° by 1° resolution grid, using satellite-derived sea surface temperature, chlorophyll, and modeled mixed layer depth. Our method is able to reproduce the interannual variability of independent in situ nitrate observations at the Bermuda Atlantic Time Series, the Hawaii Ocean Time series, the California coast, and the southern New Zealand region. Our new method is shown to be more accurate than previous algorithms and thus can provide improved information on temporal and spatial nutrient variations beyond the climatological mean at regional and global scales.

  2. Response of sea surface fugacity of CO2 to the SAM shift south of Tasmania: Regional differences

    NASA Astrophysics Data System (ADS)

    Xue, Liang; Gao, Libao; Cai, Wei-Jun; Yu, Weidong; Wei, Meng

    2015-05-01

    Using observational data collected south of Tasmania during 14 austral summer cruises during 1993-2011, we examined the response of sea surface fugacity of carbon dioxide (fCO2) to the Southern Annular Mode (SAM) shift, which occurred around 2000. In the southern part of the Southern Ocean (SO) or the Polar Zone (PZ) and the Polar Frontal Zone (PFZ), fCO2 increased faster at the sea surface than in the atmosphere before the SAM shift, but not after the shift. In the northern part of the SO or the Subantarctic Zone (SAZ), however, surface fCO2 increased faster than atmospheric fCO2 both before and after the shift. The SAM shift had an important influence on the surface fCO2 trend in the PZ and PFZ but not in the SAZ, which we attribute to differences in regional oceanographic processes (upwelling versus nonupwelling). The SAM shift may have reversed the negative trend of SO CO2 uptake.

  3. A qualitative study on sea surface temperature over the tropical Indian Ocean and performance of Indian summer monsoon

    NASA Astrophysics Data System (ADS)

    Singh, Umesh Kumar; Singh, Gyan Prakash

    2012-08-01

    A careful analysis of the sea surface temperature (SST) over the tropical Indian Ocean using the available SST data sets (namely, Hadley Center Ice SST, tropical rainfall measuring mission microwave imager SST, and optimum interpolation SST) at different time scales has been presented in the present study. By simple visual inspection of the SST plots, it has been shown that the qualitative prediction of Indian summer monsoon condition (weak/normal) and northern limit of monsoon (NLM) can be possible a month in advance using SST. The present qualitative study may be useful for common man to know the behavior of summer monsoon well a month in advance. Therefore, the qualitative study may enable the common man to show the application of satellite data to bring out the information regarding the onset of summer monsoon and related performance of Indian summer monsoon well in advance.

  4. The 2015-2016 Arctic winter: Perspectives on extremes in polar processing and meteorological variability from the 12-year record of Aura Microwave Limb Sounder measurements

    NASA Astrophysics Data System (ADS)

    Santee, Michelle; Manney, Gloria; Lambert, Alyn; Livesey, Nathaniel; Lawrence, Zachary

    2016-04-01

    In the last decade, the Arctic lower stratosphere has seen some of the most dynamically disturbed winters, with stratospheric sudden warmings that curtailed polar processing early in the season and limited chemical ozone loss, as well as several winters marked by exceptionally cold conditions and severe chemical ozone loss. The occurrence in recent winters of different combinations of extreme meteorological conditions, and their impact on polar chemical processes, has underscored the Arctic stratosphere's sensitivity to a spectrum of dynamical variability. Launched as part of NASA's Aura satellite in July 2004, the Microwave Limb Sounder (MLS) provides an extensive suite of measurements enabling quantification of polar processing and chemical ozone loss. Here we use MLS observations in conjunction with meteorological analyses in a comprehensive analysis of the Arctic winter of 2015-2016. An unusually large volume of low temperatures in the early winter led to strong depletion in gas-phase HNO3 and H2O associated with polar stratospheric cloud formation. As a consequence of this early-winter processing and an elongated vortex with significant portions exposed to sunlight, substantial chlorine activation (enhanced abundances of ClO, depressed abundances of HCl) was evident far earlier than is typical in Arctic winter. The degree of polar processing and chemical ozone loss in this winter will be placed in the context of the previous 11 Arctic winters observed by Aura MLS.

  5. Seasonal sea surface temperature anomaly prediction for coastal ecosystems

    NASA Astrophysics Data System (ADS)

    Stock, Charles A.; Pegion, Kathy; Vecchi, Gabriel A.; Alexander, Michael A.; Tommasi, Desiree; Bond, Nicholas A.; Fratantoni, Paula S.; Gudgel, Richard G.; Kristiansen, Trond; O'Brien, Todd D.; Xue, Yan; Yang, Xiasong

    2015-09-01

    Sea surface temperature (SST) anomalies are often both leading indicators and important drivers of marine resource fluctuations. Assessment of the skill of SST anomaly forecasts within coastal ecosystems accounting for the majority of global fish yields, however, has been minimal. This reflects coarse global forecast system resolution and past emphasis on the predictability of ocean basin-scale SST variations. This paper assesses monthly to inter-annual SST anomaly predictions in coastal "Large Marine Ecosystems" (LMEs). We begin with an analysis of 7 well-observed LMEs adjacent to the United States and then examine how mechanisms responsible for prediction skill in these systems are reflected in predictions for LMEs globally. Historical SST anomaly estimates from the 1/4° daily Optimal Interpolation Sea Surface Temperature reanalysis (OISST.v2) were first found to be highly consistent with in-situ measurements for 6 of the 7 U.S. LMEs. Thirty years of retrospective forecasts from climate forecast systems developed at NOAA's Geophysical Fluid Dynamics Laboratory (CM2.5-FLOR) and the National Center for Environmental Prediction (CFSv2) were then assessed against OISST.v2. Forecast skill varied widely by LME, initialization month, and lead but there were many cases of high skill that also exceeded that of a persistence forecast, some at leads greater than 6 months. Mechanisms underlying skill above persistence included accurate simulation of (a) seasonal transitions between less predictable locally generated and more predictable basin-scale SST variability; (b) seasonal transitions between different basin-scale influences; (c) propagation of SST anomalies across seasons through sea ice; and (d) re-emergence of previous anomalies upon the breakdown of summer stratification. Globally, significant skill above persistence across many tropical systems arises via mechanisms (a) and (b). Combinations of all four mechanisms contribute to less prevalent but nonetheless

  6. Sea Surface Global Climate Datasets With Compatible High Resolutions

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Bates, J. J.; Reynolds, R. W.

    2007-05-01

    Present day global ocean observing system consists of multiple satellites and in-situ platforms. Blending of these observations has made it possible to produce gridded global climate datasets with increasingly higher resolutions that are demanded by the research and operational forecast communities. However, caution must be exercised when producing and utilizing global high resolution products: under-sampling could result in significant alias errors for variables with higher frequency variability. The resolutions of the blended products have to be compatible with the available observational data density or frequency. In this paper we present a case study, taking sea surface wind speed as an example. Sea surface wind speed has been observed from multiple satellites and in-situ instruments. These long-term satellites ranged from one DMSP (the Defense Meteorological Satellite Program) satellite (F08) in mid 1987 to the present six or more satellites since June 2002. We shall show that on a global 0.25° grid, blended products with temporal resolutions of 6-hours, 12-hours and daily have become feasible since mid 2002, mid 1995 and January 1991, respectively (with greater than 75 percent time coverage and greater than 90 percent spatial coverage between 65°S-65°N). Thus, for a uniform long-term climate product on a global 0.25° grid and over the whole time period (July 1987 to present), a near Gaussian 3-D (x, y, t) interpolation was used with the spatial and time windows of 125 km and 12-hours. To take advantage of the high data density of the later years (since mid 2002), 4 times per day snapshots have been generated. Documentation of the feasibility study, data production, data visualization, sub-setting and downloading can be obtained at: http:www.ncdc.noaa.gov/oa/satellite.html; http:nomads.ncdc.noaa.gov:8085/las/servlets/dataset; ftp:eclipse.ncdc.noaa.gov/pub. Our analysis shows that the unique sampling times of the AMSR-E are largely responsible for the

  7. Analyses of global sea surface temperature 1856-1991

    NASA Astrophysics Data System (ADS)

    Kaplan, Alexey; Cane, Mark A.; Kushnir, Yochanan; Clement, Amy C.; Blumenthal, M. Benno; Rajagopalan, Balaji

    1998-08-01

    Global analyses of monthly sea surface temperature (SST) anomalies from 1856 to 1991 are produced using three statistically based methods: optimal smoothing (OS), the Kaiman filter (KF) and optimal interpolation (OI). Each of these is accompanied by estimates of the error covariance of the analyzed fields. The spatial covariance function these methods require is estimated from the available data; the timemarching model is a first-order autoregressive model again estimated from data. The data input for the analyses are monthly anomalies from the United Kingdom Meteorological Office historical sea surface temperature data set (MOHSST5) [Parker et al., 1994] of the Global Ocean Surface Temperature Atlas (GOSTA) [Bottomley et al., 1990]. These analyses are compared with each other, with GOSTA, and with an analysis generated by projection (P) onto a set of empirical orthogonal functions (as in Smith et al. [1996]). In theory, the quality of the analyses should rank in the order OS, KF, OI, P, and GOSTA. It is found that the first four give comparable results in the data-rich periods (1951-1991), but at times when data is sparse the first three differ significantly from P and GOSTA. At these times the latter two often have extreme and fluctuating values, prima facie evidence of error. The statistical schemes are also verified against data not used in any of the analyses (proxy records derived from corals and air temperature records from coastal and island stations). We also present evidence that the analysis error estimates are indeed indicative of the quality of the products. At most times the OS and KF products are close to the OI product, but at times of especially poor coverage their use of information from other times is advantageous. The methods appear to reconstruct the major features of the global SST field from very sparse data. Comparison with other indications of the El Niño-Southern Oscillation cycle show that the analyses provide usable information on

  8. Comparison of remote sensing measurements with a two-scale polarimetric emission and scattering model for sea surfaces

    NASA Technical Reports Server (NTRS)

    Yueh, S. H.; Nghiem, S. V.; Kwok, R.; Li, F. K.

    1993-01-01

    Recently, it has been observed that the brightness temperatures of sea surfaces correlate with the azimuth angle of the ocean wind vector, indicating that ocean wind direction can not only be retrieved from the microwave backscatter, but also from the brightness temperature measurements. In this paper, comparison of the theoretical result calculated from a two-scale emission and scattering model with the Seasat and SSM/I model functions and aircraft measurements is presented and potential applications of microwave polarimetry are discussed. In our two-scale model, the modified reflectivities of large scale surfaces are calculated by extending the small perturbation method to the second order for small scale perturbation with anisotropic directional spectrum. It was found that the modified reflectivities derived from the second-order scattered field agree excellently well with the results obtained from a Monte Carlo simulation technique which numerically calculates the polarimetric reflectivities of one-dimensional random rough surfaces with a power-law spectrum. Without the second-order correction, the modified reflectivities of the rough surfaces are significantly over-estimated and sign errors are observed in the third and fourth Stokes parameters for thermal emissions. The surface spectrum parameters and two-scale cutoff are selected so that the calculated scattering and emission signatures agree with the reported model functions for Seasat and SSM/I. Subsequently, the polarimetric signatures of sea surfaces are illustrated to indicate the possibility of reducing the number of azimuthal looks required for spaceborne sensors in the remote sensing of ocean wind by using the polarimetric information. Furthermore, it is found that contrary to the dependence of backscattering coefficients on incidence angles, polarimetric brightness temperatures display a stronger wind direction dependence in the near nadir-looking direction than away from nadir. Finally, we discuss

  9. 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. PMID:22704150

  10. Spatial Statistical Estimation for Massive Sea Surface Temperature Data

    NASA Astrophysics Data System (ADS)

    Marchetti, Y.; Vazquez, J.; Nguyen, H.; Braverman, A. J.

    2015-12-01

    We combine several large remotely sensed sea surface temperature (SST) datasets to create a single high-resolution SST dataset that has no missing data and provides an uncertainty associated with each value. This high resolution dataset will optimize estimates of SST in critical parts of the world's oceans, such as coastal upwelling regions. We use Spatial Statistical Data Fusion (SSDF), a statistical methodology for predicting global spatial fields by exploiting spatial correlations in the data. The main advantages of SSDF over spatial smoothing methodologies include the provision of probabilistic uncertainties, the ability to incorporate multiple datasets with varying footprints, measurement errors and biases, and estimation at any desired resolution. In order to accommodate massive input and output datasets, we introduce two modifications of the existing SSDF algorithm. First, we compute statistical model parameters based on coarse resolution aggregated data. Second, we use an adaptive spatial grid that allows us to perform estimation in a specified region of interest, but incorporate spatial dependence between locations in that region and all locations globally. Finally, we demonstrate with a case study involving estimations on the full globe at coarse resolution grid (30 km) and a high resolution (1 km) inset for the Gulf Stream region.

  11. Method for modelling sea surface clutter in complicated propagation environments

    NASA Astrophysics Data System (ADS)

    Dockery, G. D.

    1990-04-01

    An approach for predicting clutter levels in complicated propagation conditions using an advanced propagation model and one of several empirical clutter cross-section models is described. Incident power and grazing angle information is obtained using a parabolic equation/Fourier split-step technique to predict the distribution of energy in complicated, range-varying environments. Such environments also require the use of an algorithm that establishes a physically reasonable range-interpolation scheme for the measured refractivity profiles. The reflectivity of the sea surface is represented using a clutter cross-section model that was developed originally by the Georgia Institutue of Technology and subsequently modified to include the effects of arbitrary refractive conditions. Predicted clutter power levels generated by the new procedure are compared with clutter measured at 2.9 GHz during propagation experiments conducted at the NASA Wallops Flight Facility on Virginia's Eastern Shore. During these experiments, high-resolution refractivity data were collected in both range and altitude by an instrumented helicopter.

  12. Extracting the Global Sea Surface Temperature Evolutions of Different Timescales

    NASA Astrophysics Data System (ADS)

    Feng, J.; Wu, Z.

    2012-12-01

    A new data analysis procedure, involving empirical orthogonal functions (EOF) analysis and ensemble empirical mode decomposition (EEMD), is employed to extract the evolutions of global Sea Surface Temperature (SST) of different timescales spanning the period from 1880 to 2009 (130 yr). Specifically, EOF analysis serves as a means of lossy data compression to eliminate the spatial-temporally incoherent, noise-like part of the data; and EEMD decomposes SST time series into different time scales, which facilitates research on SST-related weather and climate phenomena that have various timescales. Through validation, it is shown that the difference between the results and the original SST time series are mostly white noises, both spatially and temporally incoherent. We apply the results to study El Niño-Southern Oscillation (ENSO) events. Each ENSO event is examined and we find an oceanic region off Baja California coast ( ) that is instrumental to some ENSO events, especially those recently called ENSO Modoki, whose initial warming may be traced back to earlier warming signals from Baja California.

  13. Reevaluation of mid-Pliocene North Atlantic sea surface temperatures

    USGS Publications Warehouse

    Robinson, Marci M.; Dowsett, Harry J.; Dwyer, Gary S.; Lawrence, Kira T.

    2008-01-01

    Multiproxy temperature estimation requires careful attention to biological, chemical, physical, temporal, and calibration differences of each proxy and paleothermometry method. We evaluated mid-Pliocene sea surface temperature (SST) estimates from multiple proxies at Deep Sea Drilling Project Holes 552A, 609B, 607, and 606, transecting the North Atlantic Drift. SST estimates derived from faunal assemblages, foraminifer Mg/Ca, and alkenone unsaturation indices showed strong agreement at Holes 552A, 607, and 606 once differences in calibration, depth, and seasonality were addressed. Abundant extinct species and/or an unrecognized productivity signal in the faunal assemblage at Hole 609B resulted in exaggerated faunal-based SST estimates but did not affect alkenone-derived or Mg/Ca–derived estimates. Multiproxy mid-Pliocene North Atlantic SST estimates corroborate previous studies documenting high-latitude mid-Pliocene warmth and refine previous faunal-based estimates affected by environmental factors other than temperature. Multiproxy investigations will aid SST estimation in high-latitude areas sensitive to climate change and currently underrepresented in SST reconstructions.

  14. Horizontal advection, diffusion and plankton spectra at the sea surface.

    NASA Astrophysics Data System (ADS)

    Bracco, A.; Clayton, S.; Pasquero, C.

    2009-04-01

    Plankton patchiness is ubiquitous in the oceans, and various physical and biological processes have been proposed as its generating mechanisms. However, a coherent statement on the problem is missing, due to both a small number of suitable observations and to an incomplete understanding of the properties of reactive tracers in turbulent media. Abraham (1998) suggested that horizontal advection may be the dominant process behind the observed distributions of phytoplankton and zooplankton, acting to mix tracers with longer reaction times (Rt) down to smaller scales. Conversely, Mahadevan and Campbell (2002) attributed the relative distributions of sea surface temperature and phytoplankton to small scale upwelling, where tracers with longer Rt are able to homogenize more than those with shorter reaction times. Neither of the above mechanisms can explain simultaneously the (relative) spectral slopes of temperature, phytoplankton and zooplankton. Here, with a simple advection model and a large suite of numerical experiments, we concentrate on some of the physical processes influencing the relative distributions of tracers at the ocean surface, and we investigate: 1) the impact of the spatial scale of tracer supply; 2) the role played by coherent eddies on the distribution of tracers with different Rt; 3) the role of diffusion (so far neglected). We show that diffusion determines the distribution of temperature, regardless of the nature of the forcing. We also find that coherent structures together with differential diffusion of tracers with different Rt impact the tracer distributions. This may help in understanding the highly variable nature of observed plankton spectra.

  15. The gelatinous nature of the sea-surface microlayer

    NASA Astrophysics Data System (ADS)

    Wurl, Oliver

    2013-04-01

    The sea-surface microlayer (SML) represents the interfacial layer between the ocean and atmosphere and covers the ocean's surface extensivly. Gel-like transparent exopolymer particles (TEP) in the SML were studied in oceanic and coastal SML and subsurface water samples. The TEP enrichment factor, determined as the ratio of the TEP concentration in the SML to that in the corresponding subsurface water are typically in a range of 2 to 5. The enrichment of gel-like particles include three mechanisms: (i) ascend of positive buoyant gels, (ii) adsorption and aggregation of dissolved pre-cursor material to gels on ascending bubbles, and (iii) aggregation processes in the SML through dilation/compression of the water surface. For example, the aggregation rates in the SML were generally enhanced over those in the bulk surface waters by factors of 2 to 30. Based on our studies investigating the gelatinous nature of the SML, the new emerging consensus is that the SML is a biofilm-like and microbial-rich habitat. The hypothesis of a biofilm-like coverage of the ocean's surface has wide implications on biogeochemical cycling, air-sea gas exchange and the production of organic-rich aerosols affecting formation of cloud condensation nuclei.

  16. Interannual variability in stratiform cloudiness and sea surface temperature

    SciTech Connect

    Norris, J.R.; Leovy, C.B.

    1994-12-01

    Marine stratiform cloudiness (MSC)(stratus, stratocumulus, and fog) is widespread over subtropical oceans west of the continents and over midlatitude oceans during summer, the season when MSC has maximum influence on surface downward radiation and is most influenced by boundary-layer processes. Long-term datasets of cloudiness and sea surface teperature (SST) from surface observations from 1952 to 1981 are used to examine interannual variations in MSC and SST. Linear correlations of anomalies in seasonal MSC amount with seasonal SST anomalies are negative and significant in midlatitude and eastern subtropical oceans, especially during summer. Significant negative correlations between SST and nimbostratus and nonprecipitating midlevel cloudiness are also observed at midlatitudes during summer, suggesting that summer storm tracks shift from year to year following year-to-year meridional shifts in the SST gradient. Over the 30-yr period, there are significant upward trends in MSC amount over the northern midlatitude oceans and a significant downward trend off the coast of California. The highest correlations and trends occur where gradients in MSC and SST are strongest. During summer, correlations between SST and MSC anomalies peak at zero lag in midlatitudes where warm advection prevails, but SST lags MSC in subtropical regions where cold advection predominates. This difference is attributed to a tendency for anomalies in latent heat flux to compensate anomalies in surface downward radiation in warm advection regions but not in cold advection regions.

  17. Interannual variability in stratiform cloudiness and sea surface temperature

    NASA Technical Reports Server (NTRS)

    Norris, Joel R.; Leovy, Conway B.

    1994-01-01

    Marine stratiform cloudiness (MSC)(stratus, stratocumulus, and fog) is widespread over subtropical oceans west of the continents and over midlatitude oceans during summer, the season when MSC has maximum influence on surface downward radiation and is most influenced by boundary-layer processes. Long-term datasets of cloudiness and sea surface teperature (SST) from surface observations from 1952 to 1981 are used to examine interannual variations in MSC and SST. Linear correlations of anomalies in seasonal MSC amount with seasonal SST anomalies are negative and significant in midlatitude and eastern subtropical oceans, especially during summer. Significant negative correlations between SST and nimbostratus and nonprecipitating midlevel cloudiness are also observed at midlatitudes during summer, suggesting that summer storm tracks shift from year to year following year-to-year meridional shifts in the SST gradient. Over the 30-yr period, there are significant upward trends in MSC amount over the northern midlatitude oceans and a significant downward trend off the coast of California. The highest correlations and trends occur where gradients in MSC and SST are strongest. During summer, correlations between SST and MSC anomalies peak at zero lag in midlatitudes where warm advection prevails, but SST lags MSC in subtropical regions where cold advection predominates. This difference is attributed to a tendency for anomalies in latent heat flux to compensate anomalies in surface downward radiation in warm advection regions but not in cold advection regions.

  18. A Robust Mechanical Sensing System for Unmanned Sea Surface Vehicles

    NASA Technical Reports Server (NTRS)

    Kulczycki, Eric A.; Magnone, Lee J.; Huntsberger, Terrance; Aghazarian, Hrand; Padgett, Curtis W.; Trotz, David C.; Garrett, Michael S.

    2009-01-01

    The need for autonomous navigation and intelligent control of unmanned sea surface vehicles requires a mechanically robust sensing architecture that is watertight, durable, and insensitive to vibration and shock loading. The sensing system developed here comprises four black and white cameras and a single color camera. The cameras are rigidly mounted to a camera bar that can be reconfigured to mount multiple vehicles, and act as both navigational cameras and application cameras. The cameras are housed in watertight casings to protect them and their electronics from moisture and wave splashes. Two of the black and white cameras are positioned to provide lateral vision. They are angled away from the front of the vehicle at horizontal angles to provide ideal fields of view for mapping and autonomous navigation. The other two black and white cameras are positioned at an angle into the color camera's field of view to support vehicle applications. These two cameras provide an overlap, as well as a backup to the front camera. The color camera is positioned directly in the middle of the bar, aimed straight ahead. This system is applicable to any sea-going vehicle, both on Earth and in space.

  19. Mean sea surface and geoid gradient comparisons with TOPEX altimeter data

    NASA Technical Reports Server (NTRS)

    Rapp, Richard H.; Yi, Yuchan; Wang, Yan Ming

    1994-01-01

    Cycles 4 to 54 of TOPEX data have been analyzed through comparisons with the mean sea surface given on the disturbed geophysical data record (GDR). Two inverted barometer correction procedures were considered for the data reduction. One used a constant atmospheric pressure for all data while the one adopted for use, for most computations, introduced a cycle average pressure. The maximum difference between the two estimates was 3.0 cm with a clear annual signal. With the modified correction the TOPEX sea surface was compared to The Ohio State University (OSU) mean sea surface, given on the GDR, to estimate three translations ( delta x = -2.3 cm; delta y = 25.0 cm; delta z = -0.3 cm) and a bias (43.3 cm) between the two surfaces. The only significant translation is delta y which indicates the reference frame of the TOPEX system differs from that used in the OSU mean sea surface system. The bias between the TOPEX mean sea surface and the OSU mean sea surface was used to estimate an equatorial radius of 6,378,136.55 m based on an 18-cm biased estimate of the TOPEX altimeter. Examination of the average difference, by cycle, between the TOPEX sea surface and the OSU mean sea surface suggested a bias change of 3.1 +/- 2.2 mm/yr with a positive sign indicating the average ocean surface is rising or the altimeter measured distance is decreasing. Models were implemented that solved directly for a bias, bias rate annual/semiannual, and tide correction terms. The computations indicated that a simultaneous solution for this bias, bias rate, and annual/semiannual terms gave the most accurate results. Nonsimultaneous solutions led to slightly different bias rate values. The root mean square difference between the TOPEX sea surface and OSU sea surface, after translation and bias correction, was +/- 17 cm for a typical cycle. Some locations were indentified where the difference could reach 2.3 cm and were repeated over several cycles indicating errors in the mean sea surface. Most

  20. Interpretation of observed microwave signatures from ground dual polarization radar and space multi frequency radiometer for the 2011 Grímsvötn volcanic eruption

    NASA Astrophysics Data System (ADS)

    Montopoli, M.; Vulpiani, G.; Cimini, D.; Picciotti, E.; Marzano, F. S.

    2013-07-01

    The important role played by ground-based microwave weather radars for the monitoring of volcanic ash clouds has been recently demonstrated. The potential of microwaves from satellite passive and ground-based active sensors to estimate near-source volcanic ash cloud parameters has been also proposed, though with little investigation of their synergy and the role of the radar polarimetry. The goal of this work is to show the potentiality and drawbacks of the X-band Dual Polarization radar measurements (DPX) through the data acquired during the latest Grímsvötn volcanic eruptions that took place on May 2011 in Iceland. The analysis is enriched by the comparison between DPX data and the observations from the satellite Special Sensor Microwave Imager/Sounder (SSMIS) and a C-band Single Polarization (SPC) radar. SPC, DPX, and SSMIS instruments cover a large range of the microwaves spectrum, operating respectively at 5.4, 3.2, and 0.16-1.6 cm wavelengths. The multi-source comparison is made in terms of Total Columnar Concentration (TCC). The latter is estimated from radar observables using the "Volcanic Ash Radar Retrieval for dual-Polarization X band systems" (VARR-PX) algorithm and from SSMIS brightness temperature (BT) using a linear BT-TCC relationship. The BT-TCC relationship has been compared with the analogous relation derived from SSMIS and SPC radar data for the same case study. Differences between these two linear regression curves are mainly attributed to an incomplete observation of the vertical extension of the ash cloud, a coarser spatial resolution and a more pronounced non-uniform beam filling effect of SPC measurements (260 km far from the volcanic vent) with respect to the DPX (70 km from the volcanic vent). Results show that high-spatial-resolution DPX radar data identify an evident volcanic plume signature, even though the interpretation of the polarimetric variables and the related retrievals is not always straightforward, likely due to the

  1. Global Sea Surface Temperature and Ecosystem Change Across the Mid-Miocene Climatic Optimum

    NASA Astrophysics Data System (ADS)

    Veenstra, T. J. T.; Bakker, V. B.; Sangiorgi, F.; Peterse, F.; Schouten, S.; Sluijs, A.

    2015-12-01

    The Mid-Miocene Climatic Optimum (MMCO) (ca. 17 to 14 Ma) is generally considered as the warmest episode of the Neogene based on deep marine oxygen isotope records and terrestrial plant fossils. To date, however, reasonable resolution high-quality sea surface temperature (SST) proxy records spanning its onset are scarce at best. For the remainder of the MMCO, reliable SST records are absent from the tropics and very scarce in temperate and polar regions. This leaves the question if the MMCO was truly associated with global warming and if this warming was associated with biotic change. We use organic biomarker paleothermometry (Uk'37 and TEX86) to reconstruct SST across the MMCO at four locations along a pole-to-pole transect in the Atlantic and Pacific Ocean. Additionally, we use marine palynology (mostly dinoflagellate cysts) to assess ecosystem change at these locations. This study includes the first tropical biomarker-based SST records of the MMCO. Together with new and existing SST records from higher latitudes and the corresponding palynological records, they provide new insights in the temporal and spatial development of the MMCO. Our results indicate that Mid-Miocene warming was most prominent in the Norwegian Sea, showed a more complex, perhaps upwelling-related pattern in a tropical location, and was small in the Southern Hemisphere.

  2. On the Influence of North Pacific Sea Surface Temperature on the Arctic Winter Climate

    NASA Technical Reports Server (NTRS)

    Hurwitz, Margaret M.; Newman, P. A.; Garfinkel, C. I.

    2012-01-01

    Differences between two ensembles of Goddard Earth Observing System Chemistry-Climate Model simulations isolate the impact of North Pacific sea surface temperatures (SSTs) on the Arctic winter climate. One ensemble of extended winter season forecasts is forced by unusually high SSTs in the North Pacific, while in the second ensemble SSTs in the North Pacific are unusually low. High Low differences are consistent with a weakened Western Pacific atmospheric teleconnection pattern, and in particular, a weakening of the Aleutian low. This relative change in tropospheric circulation inhibits planetary wave propagation into the stratosphere, in turn reducing polar stratospheric temperature in mid- and late winter. The number of winters with sudden stratospheric warmings is approximately tripled in the Low ensemble as compared with the High ensemble. Enhanced North Pacific SSTs, and thus a more stable and persistent Arctic vortex, lead to a relative decrease in lower stratospheric ozone in late winter, affecting the April clear-sky UV index at Northern Hemisphere mid-latitudes.

  3. Solar wind: A possible factor driving the interannual sea surface temperature tripolar mode over North Atlantic

    NASA Astrophysics Data System (ADS)

    Xiao, Ziniu; Li, Delin

    2016-06-01

    The effect of solar wind (SW) on the North Atlantic sea surface temperature (SST) in boreal winter is examined through an analysis of observational data during 1964-2013. The North Atlantic SSTs show a pronounced meridional tripolar pattern in response to solar wind speed (SWS) variations. This pattern is broadly similar to the leading empirical orthogonal function (EOF) mode of interannual variations in the wintertime SSTs over North Atlantic. The time series of this leading EOF mode of SST shows a significant interannual period, which is the same as that of wintertime SWS. This response also appears as a compact north-south seesaw of sea level pressure and a vertical tripolar structure of zonal wind, which simultaneously resembles the North Atlantic Oscillation (NAO) in the overlying atmosphere. As compared with the typical low SWS winters, during the typical high SWS winters, the stratospheric polar night jet (PNJ) is evidently enhanced and extends from the stratosphere to the troposphere, even down to the North Atlantic Ocean surface. Notably, the North Atlantic Ocean is an exclusive region in which the SW signal spreads downward from the stratosphere to the troposphere. Thus, it seems that the SW is a possible factor for this North Atlantic SST tripolar mode. The dynamical process of stratosphere-troposphere coupling, together with the global atmospheric electric circuit-cloud microphysical process, probably accounts for the particular downward propagation of the SW signal.

  4. Validation of the Version 1 NOAA/NASA Pathfinder Sea Surface Temperature Data Set

    NASA Technical Reports Server (NTRS)

    Smith, Elizabeth A.

    1998-01-01

    A high-resolution, global satellite-derived sea surface temperature (SST) data set called Pathfinder, from the Advanced Very High Resolution Radiometer (AVHRR) aboard the NOAA Polar Orbiters, is available from the Jet Propulsion Laboratory Physical Oceanography Distributed Active Archive Center (JPL PO.DAAC). Suitable for research as well as education, the Pathfinder SST data set is a result of a collaboration between the National Oceanographic and Atmospheric Administration (NOAA), the National Aeronautics and Space Administration (NASA) and investigators at several universities. NOAA and NASA are the sponsors of the Pathfinder Program, which takes advantage of currently archived Earth science data from satellites. Where necessary, satellite sensors have been intercalibrated, algorithms improved and processing procedures revised, in order to produce long time-series, global measurements of ocean, land and atmospheric properties necessary for climate research. Many Pathfinder data sets are available to researchers now, nearly a decade before the first launch of NASA's Earth Observing System (EOS). The lessons learned from the Pathfinder programs will facilitate the processing and management of terabytes of data from EOS. The Oceans component of Pathfinder has undertaken to reprocess all Global Area Coverage (GAC) data acquired by the 5-channel AVHRRs since 1981. The resultant data products are consistent and stably calibrated [Rao, 1993a, Rao, 1993b, Brown et al., 1993], Earth-gridded SST fields at a variety of spatial and temporal resolutions.

  5. OSI-SAF operational NPP/VIIRS sea surface temperature chain

    NASA Astrophysics Data System (ADS)

    Le Borgne, Pierre; Legendre, Gérard; Marsouin, Anne; Péré, Sonia; Roquet, Hervé

    2013-06-01

    Data of the Visible Infrared Imaging Radiometer Suite (VIIRS) onboard Suomi National Polar-orbiting Partnership (NPP) have been acquired at Centre de Météorologie Spatiale (CMS) in Lannion (Brittany) in direct readout mode since April 2012. CMS is committed to produce sea surface temperature (SST) products from VIIRS data twice a day over an area covering North-East Atlantic and the Mediterranean Sea in the framework of the EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI-SAF). A cloud mask has been developed and cloud mask control techniques have been implemented. SST algorithms have been defined, as well as quality level attribution rules. Since mid October 2012 a VIIRS SST chain, similar to that used for processing METOP AVHRR has been run in a preoperational mode. The corresponding bias and standard deviation against drifting buoy measurements (mid October 2012 to mid March 2013) are -0.05 and 0.37 K for nighttime and -0.13 and 0.46 K for daytime, respectively. VIIRS derived SST production is expected operational by mid 2013. The OSI-SAF VIIRS derived SST products are compliant with the Group for High Resolution SST (GHRSST) GDS V2.0 format.

  6. Seasonal differences in intraseasonal and interannual variability of Mediterranean Sea surface temperature

    NASA Astrophysics Data System (ADS)

    Zveryaev, Igor I.

    2015-04-01

    Sea surface temperature (SST) data from the NOAA OI SST data set for 1982-2011 are used to investigate intraseasonal and interannual variability of Mediterranean SST during winter and summer seasons. It is shown that during winter the intraseasonal SST fluctuations are larger than the interannual SST variations in the western Mediterranean (e.g., the Tyrrhenian Sea), but smaller in the central and eastern Mediterranean Sea. In summer, the intraseasonal SST fluctuations are larger in almost the entire Mediterranean basin. Also summertime intraseasonal SST fluctuations are larger (up to three times near the Gulf of Lions) than their wintertime counterparts in the entire Mediterranean basin. The interannual SST variations are larger during summer in the western and central Mediterranean Sea and during winter in its eastern part. The leading empirical orthogonal functions (EOFs) of the Mediterranean SST and of the intensities of its intraseasonal fluctuations are characterized by the differing spatial-temporal structures both during winter and summer implying that their interannual variability is driven by different physical mechanisms. During winter, the EOF-1 of SST is associated with the East Atlantic teleconnection, whereas EOF-1 of the intensity of intraseasonal fluctuations is not linked significantly to regional atmospheric dynamics. The second EOFs of these variables are associated, respectively, with the East Atlantic/West Russia and the North Atlantic teleconnections. While during summer the atmospheric influence on Mediterranean SST is generally weaker, it is revealed that the EOF-1 of the intensity of intraseasonal SST fluctuations is linked to the Polar teleconnection.

  7. 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.

  8. Optimum interpolation analysis of Aquarius sea surface salinity

    NASA Astrophysics Data System (ADS)

    Melnichenko, Oleg; Hacker, Peter; Maximenko, Nikolai; Lagerloef, Gary; Potemra, James

    2016-01-01

    A new high-resolution sea surface salinity (SSS) analysis has been produced using Aquarius satellite observations from September 2011 to June 2015. The motivation for the new product is twofold: to produce Level-4 SSS analysis that is consistent with existing in situ observations such as from Argo profile data, and to reduce the large-scale satellite biases that have existed in all versions of the standard Level-3 Aquarius products. The new product is a weekly SSS analysis on a nearly global 0.5° grid. The analysis method is optimum interpolation (OI) that takes into account analyzed errors of the observations, specific to the Aquarius instrument. The method also includes a large-scale correction for satellite biases, filtering of along-track SSS data prior to OI, and the use of realistic correlation scales of SSS anomalies. All these features of the analysis are shown to result in more accurate SSS maps. In particular, the method reduces the effects of relative biases between the Aquarius beams and eliminates most of the large-scale, space-varying, and time-varying satellite biases relative to in situ data, including spurious annual signals. Statistical comparison between the weekly OI SSS maps and concurrent buoy data demonstrates that the global root-mean-square error of the analysis is smaller than 0.2 pss for nearly all weeks over the ˜4 year period of comparison. The utility of the OI SSS analysis is also exemplified by the derived patterns of regional SSS variability.

  9. Long-Range Correlations of Global Sea Surface Temperature.

    PubMed

    Jiang, Lei; Zhao, Xia; Wang, Lu

    2016-01-01

    Scaling behaviors of the global monthly sea surface temperature (SST) derived from 1870-2009 average monthly data sets of Hadley Centre Sea Ice and SST (HadISST) are investigated employing detrended fluctuation analysis (DFA). The global SST fluctuations are found to be strong positively long-range correlated at all pertinent time-intervals. The value of scaling exponent is larger in the tropics than those in the intermediate latitudes of the northern and southern hemispheres. DFA leads to the scaling exponent α = 0.87 over the globe (60°S~60°N), northern hemisphere (0°N~60°N), and southern hemisphere (0°S~60°S), α = 0.84 over the intermediate latitude of southern hemisphere (30°S~60°S), α = 0.81 over the intermediate latitude of northern hemisphere (30°N~60°N) and α = 0.90 over the tropics 30°S~30°N [fluctuation F(s) ~ sα], which the fluctuations of monthly SST anomaly display long-term correlated behaviors. Furthermore, the larger the standard deviation is, the smaller long-range correlations (LRCs) of SST in the corresponding regions, especially in three distinct upwelling areas. After the standard deviation is taken into account, an index χ = α * σ is introduced to obtain the spatial distributions of χ. There exists an obvious change of global SST in central east and northern Pacific and the northwest Atlantic. This may be as a clue on predictability of climate and ocean variabilities. PMID:27100397

  10. Estimation of Sea Surface Temperature (SST) Using Marine Seismic Data

    NASA Astrophysics Data System (ADS)

    Sinha, Satish Kumar; Dewangan, Pawan; Sain, Kalachand

    2016-04-01

    Not much attention is given to direct wave arrivals in marine seismic data that are acquired for petroleum exploration and prospecting. These direct arrivals are usually muted out in routine seismic data processing. In the present study, we process these direct arrivals to accurately estimate soundspeed in near-surface seawater and invert for sea surface temperature. The established empirical equation describing the relationships among temperature, salinity, pressure and soundspeed is used for the inversion. We also discuss processing techniques, such as first-break picking and cross-correlation for the estimation of soundspeed, that are well known among petroleum-industry geophysicists. The accuracy of the methods is directly linked to the data quality and signal processing. The novelty in our approach is in the data conditioning, which consists essentially of spectral balancing based on a wavelet transform that compensates for spherical spreading and increases the signal-to-noise ( S/ N) ratio. The 2D seismic data used in this paper are from the offshore Krishna-Godavari Basin east of India. We observe a significantly higher soundspeed of 1545 m/s for near-surface water than the commonly used value of ~1500 m/s. The estimated temperature (from velocity) is about 30 °C. Interestingly, the estimated temperature matches well with the temperature recorded in the CTD profile acquired in the study area during the month of May, the month corresponding to the acquisition of seismic data. Furthermore, the estimated temperatures during different times of data acquisition correlate well with the expected diurnal variation in temperature.

  11. Testing for deterministic trends in global sea surface temperature

    NASA Astrophysics Data System (ADS)

    Barbosa, Susana

    2010-05-01

    The identification and estimation of trends is a frequent and fundamental task in the analysis of hydrometeorological records. The task is challenging because even time series generated by purely random processes can exhibit visually appealing trends that can be misleadingly taken as evidence of non-stationary behavior. Hydrometeorological time series exhibiting long range dependence can also exhibit trend-like features that can be mistakenly interpreted as a trend, leading to erroneous forecasts and interpretations of the variability structure of the series, particularly in terms of statistical uncertainty. In practice the overwhelming majority of trends in hydro-climatic records are reported as the slope from a linear regression model. It is therefore important to assess when a linear regression model is a reasonable description for a time series. One could think that if a derived slope is statistically significant, particularly if inference is performed carefully, the linear regression model would be appropriate. However, stochastic features, such as long-range dependence can produce statistically significant linear trends. Therefore, the plausibility of the linear regression model needs to be tested itself, in addition to testing if the trend slope is statistically significant. In this work parametric statistical tests are applied in order to evaluate the trend-stationary assumption in global sea surface temperature for the period from January 1900 to December 2008. The fit of a linear deterministic model to the spatially-averaged global mean SST series yields a statistically significant positive slope, suggesting an increasing linear trend. However, statistical testing rejects the hypothesis of a deterministic linear trend with a stationary stochastic noise. This is supported by the form of the temporal structure of the detrended series, which exhibits large positive values up to lags of 5 years, indicating temporal persistence.

  12. Sea surface temperature variability in the Colombian Basin, Caribbean Sea

    NASA Astrophysics Data System (ADS)

    Ruiz-Ochoa, Mauricio; Beier, Emilio; Bernal, Gladys; Barton, Eric Desmond

    2012-06-01

    Daily sea surface temperature (SST) data from the Advanced Very High Resolution Radiometer (AVHRR) database with ∼4 km of spatial resolution were analyzed for the period 1985-2009 in the Colombian Basin using harmonic and empirical orthogonal function (EOF) analysis. The data were compared with observational records in the Rosario Island National Park at 10 m depth (T10) from March 2003 to August 2005. SST values were higher than T10 from June to October (rainy season), but similar from December to February (dry season); both data sets have similar coefficient of variation. The mean SST distribution varies spatially, with minimum SST values in the coastal zone of La Guajira Peninsula and maximum values in the Darien and Mosquitos Gulfs. The seasonal variability explains up to 75% of the total variability in La Guajira, a high value compared with 40% in the Mosquitos Gulf. The most important feature of the splitting of SST variation into annual and semiannual harmonics in La Guajira is the relationship between their amplitudes. These are of the same order, which is not common in other ocean zones, where the semiannual component is only a small fraction of the annual dominated by the solar warming. The river water discharge, highest from August to November, produces low density surface water, reduces vertical mixing and limits the absorption of solar radiation to a thin surface layer, explaining the discrepancy between SST and T10 in the rainy season. The decomposition of the SST in EOFs indicated that the dominant mode of the basin is a uniform interannual variation in phase with the North Tropical Atlantic Index. The second mode, representing the variability of the Guajira upwelling, covaried strongly with the second mode of wind stress curl. The third mode reflected the role of the vertical atmospheric circulation cell associated with the Caribbean Low Level Jet off Central America.

  13. Sampling Errors in Satellite-derived Infrared Sea Surface Temperatures

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Minnett, P. J.

    2014-12-01

    Sea Surface Temperature (SST) measured from satellites has been playing a crucial role in understanding geophysical phenomena. Generating SST Climate Data Records (CDRs) is considered to be the one that imposes the most stringent requirements on data accuracy. For infrared SSTs, sampling uncertainties caused by cloud presence and persistence generate errors. In addition, for sensors with narrow swaths, the swath gap will act as another sampling error source. This study is concerned with quantifying and understanding such sampling errors, which are important for SST CDR generation and for a wide range of satellite SST users. In order to quantify these errors, a reference Level 4 SST field (Multi-scale Ultra-high Resolution SST) is sampled by using realistic swath and cloud masks of Moderate Resolution Imaging Spectroradiometer (MODIS) and Advanced Along Track Scanning Radiometer (AATSR). Global and regional SST uncertainties are studied by assessing the sampling error at different temporal and spatial resolutions (7 spatial resolutions from 4 kilometers to 5.0° at the equator and 5 temporal resolutions from daily to monthly). Global annual and seasonal mean sampling errors are large in the high latitude regions, especially the Arctic, and have geographical distributions that are most likely related to stratus clouds occurrence and persistence. The region between 30°N and 30°S has smaller errors compared to higher latitudes, except for the Tropical Instability Wave area, where persistent negative errors are found. Important differences in sampling errors are also found between the broad and narrow swath scan patterns and between day and night fields. This is the first time that realistic magnitudes of the sampling errors are quantified. Future improvement in the accuracy of SST products will benefit from this quantification.

  14. Data-Model Comparison of Pliocene Sea Surface Temperature

    NASA Astrophysics Data System (ADS)

    Dowsett, H. J.; Foley, K.; Robinson, M. M.; Bloemers, J. T.

    2013-12-01

    The mid-Piacenzian (late Pliocene) climate represents the most geologically recent interval of long-term average warmth and shares similarities with the climate projected for the end of the 21st century. As such, its fossil and sedimentary record represents a natural experiment from which we can gain insight into potential climate change impacts, enabling more informed policy decisions for mitigation and adaptation. We present the first systematic comparison of Pliocene sea surface temperatures (SST) between an ensemble of eight climate model simulations produced as part of PlioMIP (Pliocene Model Intercomparison Project) and the PRISM (Pliocene Research, Interpretation and Synoptic Mapping) Project mean annual SST field. Our results highlight key regional (mid- to high latitude North Atlantic and tropics) and dynamic (upwelling) situations where there is discord between reconstructed SST and the PlioMIP simulations. These differences can lead to improved strategies for both experimental design and temporal refinement of the palaeoenvironmental reconstruction. Scatter plot of multi-model-mean anomalies (squares) and PRISM3 data anomalies (large blue circles) by latitude. Vertical bars on data anomalies represent the variability of warm climate phase within the time-slab at each locality. Small colored circles represent individual model anomalies and show the spread of model estimates about the multi-model-mean. While not directly comparable in terms of the development of the means nor the meaning of variability, this plot provides a first order comparison of the anomalies. Encircled areas are a, PRISM low latitude sites outside of upwelling areas; b, North Atlantic coastal sequences and Mediterranean sites; c, large anomaly PRISM sites from the northern hemisphere. Numbers identify Ocean Drilling Program sites.

  15. Long-Range Correlations of Global Sea Surface Temperature

    PubMed Central

    Jiang, Lei; Zhao, Xia; Wang, Lu

    2016-01-01

    Scaling behaviors of the global monthly sea surface temperature (SST) derived from 1870–2009 average monthly data sets of Hadley Centre Sea Ice and SST (HadISST) are investigated employing detrended fluctuation analysis (DFA). The global SST fluctuations are found to be strong positively long-range correlated at all pertinent time-intervals. The value of scaling exponent is larger in the tropics than those in the intermediate latitudes of the northern and southern hemispheres. DFA leads to the scaling exponent α = 0.87 over the globe (60°S~60°N), northern hemisphere (0°N~60°N), and southern hemisphere (0°S~60°S), α = 0.84 over the intermediate latitude of southern hemisphere (30°S~60°S), α = 0.81 over the intermediate latitude of northern hemisphere (30°N~60°N) and α = 0.90 over the tropics 30°S~30°N [fluctuation F(s) ~ sα], which the fluctuations of monthly SST anomaly display long-term correlated behaviors. Furthermore, the larger the standard deviation is, the smaller long-range correlations (LRCs) of SST in the corresponding regions, especially in three distinct upwelling areas. After the standard deviation is taken into account, an index χ = α * σ is introduced to obtain the spatial distributions of χ. There exists an obvious change of global SST in central east and northern Pacific and the northwest Atlantic. This may be as a clue on predictability of climate and ocean variabilities. PMID:27100397

  16. 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

  17. Daily sea surface salinity variability in the tropical Pacific Ocean derived from satellite remote sensing data

    NASA Astrophysics Data System (ADS)

    Ballabrera-Poy, Joaquim; Olmedo, Estrella; Turiel, Antonio; Portabella, Marcos; Martinez, Justino; Hoareau, Nina

    2016-04-01

    In this work, a multifractal data fusion algorithm is used to obtain daily sea surface salinity (SSS) maps from the Soil Moisture and Ocean Salinity (SMOS) Level 2 (L2) data. The L2 SSS retrievals are obtained from the brightness temperature reconstructions at different polarizations and incidence angles along the satellite swath. SMOS L2 data have a spatial resolution of about 43 km and accuracy between 0.6 to 1.7 (in the practical salinity scale). The main goal of the data fusion algorithm is to use the reliable information of the OSTIA sea surface temperature (SST) daily fields to increase the spatial and temporal resolution of the SMOS L2 SSS data. Our SMOS dataset consists of the European Space Agency (ESA) L2 v620 reprocessed data from January 2010 to May 2015, and of the latest L2 operational data (near real-time) version after May 2015. Salinity anomalies are constructed by removing the five-year average of the L2 salinity data as a function of the geographical position, the overpass orientation (ascending or descending), and the across-track distance to the center of the swath. The SMOS-based climatologies evidence the existence of strong systematic artifacts, especially near the coast and, as such, they allow retrieving some of the systematic errors present in the original L2 data. The 0.05-degree, daily SST product from OSTIA is used as a template in our scalar fusion algorithm to generate 0.05 degree, daily SSS maps. The resulting SSS maps are less noisy and better define the main geophysical structures as compared to the standard high-level SSS products. Differences against near-surface Argo salinity measurements are reduced by 40% with respect to the standard products. In order to assess the significance of the extrapolation to the time domain, data from the Global Tropical Moored Buoy Array are used. The results indicate that the small time-scale variability present in the mooring data are not completely reproduced by remote sensing, although data

  18. Modeling Tropospheric Radiowave Propagation Over Rough Sea Surfaces Using the Parabolic Equation Fourier Split-step Method

    NASA Astrophysics Data System (ADS)

    Cadette, Pierre E.

    This thesis develops the theory for solving the parabolic equation (PE) using the Fourier Split-step method for the purpose of modeling tropospheric radiowave propagation over the sea surface. Beginning with Maxwell's equations, the standard parabolic equation (SPE) approximation is derived from a linearly polarized scalar wave equation in Cartesian coordinates. Then, an introduction to the Fourier Split-step method is presented as a solution to the PE equation. Next, we make necessary approximations to the PE formulation to appropriately represented propagation through the troposphere including a conformal transformation of the coordinate system and the inclusion of refractivity profiles to represent evaporation duct conditions. The PE derivation concludes with the incorporation of the effects of finite impedance boundary conditions and sea surface roughness, which has a Split-step solution using the mixed Fourier transform (MFT). Finally, numerical examples are given to compare the field predictions of two well known PE/Split-step propagation models: Tropospheric ElectroMagnetic Parabolic Equation Routine (TEMPER) and Advanced Propagation Model (APM).

  19. Modes of variability of global sea surface temperature, free atmosphere temperature and oceanic surface energy flux

    SciTech Connect

    Hu, Wenjie; Newell, R.E.; Wu, Zhong-Xiang

    1994-11-01

    Monthly mean sea surface temperature (SST), free air temperature from satellite microwave sounding units (MSU) and oceanic surface energy fluxes are subjected to empirical orthogonal function (EOF) analysis for a common decade to investigate the physical relationships involved. The first seasonal modes of surface solar energy flux and SST show similar inter-hemispheric patterns with an annual cycle. Solar flux appears to control this pattern of SST. The first seasonal mode of MSU is similar with, additionally, land-sea differences; MSU is apparently partly controlled by absorption of solar near-infrared radiation and partly by sensible heat from from the land surface. The second and third seasonal eigenvector of SST and solar flux exhibit semi-annual oscillations associated with a pattern of cloudiness in the subtropics accompanying the translation of the Hadley cell rising motion between the hemispheres. The second seasonal mode of MSU is dominated by an El Nino Signal. The first nonseasonal EOFs of SST and solar flux exhibit El Nino characteristics with solar pattern being governed by west-to-east translation of a Walker cell type pattern. The first non-seasonal EOF of MSU shows a tropical strip pattern for the El Nino mode, which is well correlated with the latent heat fluxes in the tropical east Pacific but not in the tropical west Pacific. Two possible explanations are: an increase in subsidence throughout the tropical strip driven by extra evaporation in the tropical east Pacific and consequent additional latent heat liberation; a decrease of meridional heat flux out of the tropics. 56 refs., 12 figs., 5 tabs.

  20. An in situ-satellite blended analysis of global sea surface salinity

    NASA Astrophysics Data System (ADS)

    Xie, P.; Boyer, T.; Bayler, E.; Xue, Y.; Byrne, D.; Reagan, J.; Locarnini, R.; Sun, F.; Joyce, R.; Kumar, A.

    2014-09-01

    The blended monthly sea surface salinity (SSS) analysis, called the NOAA "Blended Analysis of Surface Salinity" (BASS), is constructed for the 4 year period from 2010 to 2013. Three data sets are employed as inputs to the blended analysis: in situ SSS measurements aggregated and quality controlled by NOAA/NODC, and passive microwave (PMW) retrievals from both the National Aeronautics and Space Administration's (NASA) Aquarius/SAC-D and the European Space Agency's (ESA) Soil Moisture-Ocean Salinity (SMOS) satellites. The blended analysis comprises two steps. First, the biases in the satellite retrievals are removed through probability distribution function (PDF) matching against temporally spatially colocated in situ measurements. The blended analysis is then achieved through optimal interpolation (OI), where the analysis for the previous time step is used as the first guess while the in situ measurements and bias-corrected satellite retrievals are employed as the observations to update the first guess. Cross validations illustrate improved quality of the blended analysis, with reduction in bias and random errors over most of the global oceans as compared to the individual inputs. Large uncertainty, however, remains in high-latitude oceans and coastal regions where the in situ networks are sparse and current-generation satellite retrievals have limitations. Our blended SSS analysis shows good agreements with the NODC in situ-based analysis over most of the tropical and subtropical oceans, but large differences are observed for high-latitude oceans and along coasts. In the tropical oceans, the BASS is shown to have coherent variability with precipitation and evaporation associated with the evolution of the El Niño-Southern Oscillation (ENSO).

  1. Present status of the global change observation mission 1st - water 'SHIZUKU' (GCOM-W1) and the advanced microwave scanning radiometer 2 (AMSR2)

    NASA Astrophysics Data System (ADS)

    Tsutsui, Hiroyuki; Imaoka, Keiji; Kachi, Misako; Maeda, Takeshi; Kasahara, Marehito; Ito, Norimasa; Oki, Taikan; Shimoda, Haruhisa

    2014-11-01

    The Global Change Observation Mission 1st - Water (CGOM-W1) or "SHIZUKU" was launched on May 18, 2012 (JST) from the JAXA's Tanegashima Space Center. Subsequently, the GCOM-W1 satellite was joined to the NASA's A-train orbit since June 29, 2012 to succeed observation by the Advanced Microwave Scanning Radiometer for EOS (AMSR-E) and to provide combined utilization with other A-train satellites. The Advanced Microwave Scanning Radiometer 2 (AMSR2), which is a successor of AMSR-E, onboard GCOM-W1 has started its scientific observation since July 3, 2012. AMSR-E was halted its scientific observation on October 4, 2011, but has restarted observation in slow antenna rotation rate since December 4, 2012 for cross-calibration with AMSR2. AMSR2 has multi-frequency, total-power microwave radiometer systems with dual polarization channels for all frequency bands, and continues AMSR-E observations: 1) Water vapor, 2) Cloud liquid water, 3) Precipitation, 4) SST, 5) Sea surface wind speed, 6) Sea ice concentration, 7) Snow depth, 8) Soil moisture. JAXA opened the AMSR2's brightness temperature products to the public since January 2013 after initial calibration/validation period by the GCOM-W1 Data Providing Service (https://gcomwl.jaxa.jp/). Thereafter, the retrieval algorithms of standard geophysical products for water vapor, cloud liquid water, precipitation, sea surface temperature, sea surface wind speed, sea ice concentration, snow depth and soil moisture were modified, and JAXA opened these standard geophysical products to the public since May 2013. In this paper, we present the present operation status of AMSR2.

  2. Anisotropy and polarization of the microwave background radiation as a test of nonequilibrium ionization of the pregalactic plasma

    SciTech Connect

    Nasel'skii, P.D.; Polnarev, A.G.

    1987-11-01

    The formation of small-scale anisotropy and polarization in a model of nonstationary ionization of the pregalactic plasma is considered. It is shown that the ratio of the degree of polarization to the degree of anisotropy is rather insensitive to the actual regime of ionization and is 7-8%. However, the characteristic correlation angle is in the distribution of the anisotropy and polarization of the background radiation on the celestial sphere depends strongly on the parameters of the nonequilibrium.

  3. Three Years of Atmospheric Infrared Sounder Radiometric Calibration Validation using Sea Surface Temperatures

    NASA Technical Reports Server (NTRS)

    Aumann, H. H.; Broberg, Steve; Elliott, Denis; Gaiser, Steve; Gregorich, Dave

    2006-01-01

    This paper evaluates the absolute accuracy and stability of the radiometric calibration of the Atmospheric Infrared Sounder (AIRS) by analyzing the difference between the brightness temperatures measured at 2616 cm(exp -1) and those calculated at the top of the atmosphere (TOA), using the Real-Time Global Sea Surface Temperature (RTGSST) for cloud-free night tropical oceans between +/- 30 degrees latitude. The TOA correction is based on radiative transfer. The analysis of the first 3 years of AIRS radiances verifies the absolute calibration at 2616 cm(exp -1) to better than 200 mK, with better than 16 mK/yr stability. The AIRS radiometric calibration uses an internal full aperture wedge blackbody with the National Institute of Standards and Technology (NIST) traceable prelaunch calibration coefficients. The calibration coefficients have been unchanged since launch. The analysis uses very tight cloud filtering, which selects about 7000 cloud-free tropical ocean spectra per day, about 0.5% of the data. The absolute accuracy and stability of the radiometry demonstrated at 2616 cm(sup -1) are direct consequences of the implementation of AIRS as a thermally controlled, cooled grating-array spectrometer and meticulous attention to details. Comparable radiometric performance is inferred from the AIRS design for all 2378 channels. AIRS performance sets the benchmark for what can be achieved with a state-of-the-art hyperspectral radiometer from polar orbit and what is expected from future hyperspectral sounders. AIRS was launched into a 705 km altitude polar orbit on NASA's Earth Observation System (EOS) Aqua spacecraft on 4 May 2002. AIRS covers the 3.7-15.4 micron region of the thermal infrared spectrum with a spectral resolution of nu/Delta nu = 1200 and has returned 3.7 million spectra of the upwelling radiance each day since the start of routine data gathering in September 2002.

  4. Proxy data constraints on Cretaceous sea surface temperature evolution

    NASA Astrophysics Data System (ADS)

    O'Brien, Charlotte L.; Robinson, Stuart A.; O'Connor, Lauren K.; Pancost, Richard D.

    2015-04-01

    It is well established that greenhouse conditions prevailed during the Cretaceous. However, constraining the exact nature of the greenhouse gas forcing, climatic warming and climate sensitivity remains an ongoing topic of research. Proxy temperature data provide valuable observational constraints on Cretaceous climate. In particular, much of our understanding of Cretaceous climate warmth comes from marine temperature proxy data reconstructions derived using planktic foraminiferal oxygen isotope (δ18O) palaeothermometry and, more recently, the TEX86 proxy, based on the distribution of marine isoprenoidal glycerol dialkyl glycerol tetraether lipids (GDGTs). Both of these proxies provide estimates of sea surface temperature (SST), however each technique is subject to a number of proxy-specific caveats. For example, δ18O values in planktic foraminifer may be compromised by preservation and/or diagenetic alteration, while the TEX86 proxy has undergone several temperature calibration re-evaluations and the exact mechanism that relates GDGT production to SST is not fully understood. Here we synthesise and reinterpret available TEX86- and δ18O-SST proxy data for the entire Cretaceous. For the TEX86 data, where possible we re-evaluate the fractional abundance of all individual GDGTs. By utilising fractional GDGT abundances we are also able to compute methane indices and branched and isoprenoid tetraether (BIT) indices, as well as apply both the TEX86H and TEX86L temperature calibrations. For each of the two SST proxy techniques, TEX86 and δ18O, we apply consistent temperature calibrations and place all data on a common timescale. Our new data-based SST synthesis allows us to examine long term temperature trends in the Cretaceous, including latitudinal temperature gradient variations, and evaluate global versus regional temperature patterns. Through considering both TEX86 and planktic foraminiferal δ18O data we critically compare the application of these two techniques

  5. Improving Streamflow Forecasts Using Predefined Sea Surface Temperature

    NASA Astrophysics Data System (ADS)

    Kalra, A.; Ahmad, S.

    2011-12-01

    With the increasing evidence of climate variability, water resources managers in the western United States are faced with greater challenges of developing long range streamflow forecast. This is further aggravated by the increases in climate extremes such as floods and drought caused by climate variability. Over the years, climatologists have identified several modes of climatic variability and their relationship with streamflow. These climate modes have the potential of being used as predictor in models for improving the streamflow lead time. With this as the motivation, the current research focuses on increasing the streamflow lead time using predefine climate indices. A data driven model i.e. Support Vector Machine (SVM) based on the statistical learning theory is used to predict annual streamflow volume 3-year in advance. The SVM model is a learning system that uses a hypothesis space of linear functions in a Kernel induced higher dimensional feature space, and is trained with a learning algorithm from the optimization theory. Annual oceanic-atmospheric indices, comprising of Pacific Decadal Oscillation (PDO), North Atlantic Oscillation (NAO), Atlantic Multidecadal Oscillation (AMO), El Niño-Southern Oscillations (ENSO), and a new Sea Surface Temperature (SST) data set of "Hondo" Region for a period of 1906-2005 are used to generate annual streamflow volumes. The SVM model is applied to three gages i.e. Cisco, Green River, and Lees Ferry in the Upper Colorado River Basin in the western United States. Based on the performance measures the model shows very good forecasts, and the forecast are in good agreement with measured streamflow volumes. Previous research has identified NAO and ENSO as main drivers for extending streamflow forecast lead-time in the UCRB. Inclusion of "Hondo Region" SST information further improve the model's forecasting ability. The overall results of this study revealed that the annual streamflow of the UCRB is significantly influenced by

  6. Regional studies using sea surface temperature fields derived from satellite infrared measurements

    NASA Technical Reports Server (NTRS)

    Strong, A. E.

    1972-01-01

    Three examples of sea surface temperature distributions over the western Atlantic are presented. These were detected by means of data from the scanning radiometer on the Improved Tiros Operational Satellite 1 (ITOS 1) under relatively clear sky conditions.

  7. Moderate-Resolution Sea Surface Temperature Data for the Nearshore North Pacific

    EPA Science Inventory

    Coastal sea surface temperature (SST) is an important environmental characteristic defining habitat suitability for nearshore marine and estuarine organisms. The purpose of this publication is to provide access to an easy-to-use coastal SST dataset for ecologists, biogeographers...

  8. Measurements of the infrared emissivity of a wind-roughened sea surface.

    PubMed

    Hanafin, Jennifer A; Minnett, Peter J

    2005-01-20

    Spectral statistical-analysis techniques were developed and applied to high-spectral-resolution infrared measurements of the sea surface. The effective incidence angle of a ship-borne instrument in typical at-sea conditions was found to introduce errors of up to 0.7 K in sea-surface temperature retrievals at a 55 degrees view angle. The sea-surface emissivity was determined over the 8-12-microm window at view angles of 40 degrees and 55 degrees and at wind speeds up to 13 ms(-1). The emissivity was found to increase in magnitude with increasing wind speed, rather than decrease, as predicted by widely used parameterizations. Use of these parameterizations can cause significant bias in remote sensing of sea-surface temperature in noncalm conditions. PMID:15717830

  9. Moderate-resolution sea surface temperature data for the Arctic Ocean Ecoregions

    EPA Science Inventory

    Sea surface temperature (SST) is an important environmental characteristic in determining the suitability and sustainability of habitats for marine organisms. Of particular interest is the fate of the Arctic Ocean, which provides critical habitat to commercially important fish (M...

  10. Physical Retrievals of Over-Ocean Rain Rate from Multichannel Microwave Imagery. Part 1; Theoretical Characteristics of Normalized Polarization and Scattering Indices

    NASA Technical Reports Server (NTRS)

    Petty, G. W.

    1994-01-01

    Microwave rain rate retrieval algorithms have most often been formulated in terms of the raw brightness temperatures observed by one or more channels of a satellite radiometer. Taken individually, single-channel brightness temperatures generally represent a near-arbitrary combination of positive contributions due to liquid water emission and negative contributions due to scattering by ice and/or visibility of the radiometrically cold ocean surface. Unfortunately, for a given rain rate, emission by liquid water below the freezing level and scattering by ice particles above the freezing level are rather loosely coupled in both a physical and statistical sense. Furthermore, microwave brightness temperatures may vary significantly (approx. 30-70 K) in response to geophysical parameters other than liquid water and precipitation. Because of these complications, physical algorithms which attempt to directly invert observed brightness temperatures have typically relied on the iterative adjustment of detailed micro-physical profiles or cloud models, guided by explicit forward microwave radiative transfer calculations. In support of an effort to develop a significantly simpler and more efficient inversion-type rain rate algorithm, the physical information content of two linear transformations of single-frequency, dual-polarization brightness temperatures is studied: the normalized polarization difference P of Petty and Katsaros (1990, 1992), which is intended as a measure of footprint-averaged rain cloud transmittance for a given frequency; and a scattering index S (similar to the polarization corrected temperature of Spencer et al.,1989) which is sensitive almost exclusively to ice. A reverse Monte Carlo radiative transfer model is used to elucidate the qualitative response of these physically distinct single-frequency indices to idealized 3-dimensional rain clouds and to demonstrate their advantages over raw brightness temperatures both as stand-alone indices of

  11. Satellite observations of a polar low over the Norwegian Sea by Special Sensor Microwave Imager, Geosat, and TIROS-N Operational Vertical Sounder

    NASA Technical Reports Server (NTRS)

    Claud, Chantal; Mognard, Nelly M.; Katsaros, Kristina B.; Chedin, Alain; Scott, Noelle A.

    1993-01-01

    Many polar lows are generated at the boundary between sea ice and the ocean, in regions of large temperature gradients, where in situ observations are rare or nonexistent. Since satellite observations are frequent in high-latitude regions, they can be used to detect polar lows and track their propagation and evolution. The Special Sensor Microwave/Imager (SSM/I) providing estimates of surface wind speed, integrated cloud liquid water content, water vapor content, and precipitation size ice-scattering signal over the ocean; the Geosat radar altimeter measuring surface wind speed and significant wave height; and the TIROS-N Operational Vertical Sounder (TOVS) allowing the determination of temperature and humidity profiles in the atmosphere have been used in synergy for a specific case which occurred in the Norwegian Sea on January, 23-24 1988. All three instruments show sharp atmospheric gradients associated with the propagation of this low across the ocean, which permit the detection of the polar low at a very early stage and tracking it during its development, propagation, and decay. The wind speed gradients are measured with good qualitative agreement between the altimeter and SSM/I. TOVS retrieved fields prior to the formation of the low confirm the presence of an upper level trough, while during the mature phase baroclinicity can be observed in the 1000-500 hPa geopotential thicknesses.

  12. Measurements of E-Mode Polarization and Temperature-E-Mode Correlation in the Cosmic Microwave Background from 100 Square Degrees of SPTpol Data

    NASA Astrophysics Data System (ADS)

    Crites, A. T.; Henning, J. W.; Ade, P. A. R.; Aird, K. A.; Austermann, J. E.; Beall, J. A.; Bender, A. N.; Benson, B. A.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Chiang, H. C.; Cho, H.-M.; Citron, R.; Crawford, T. M.; de Haan, T.; Dobbs, M. A.; Everett, W.; Gallicchio, J.; Gao, J.; George, E. M.; Gilbert, A.; Halverson, N. W.; Hanson, D.; Harrington, N.; Hilton, G. C.; Holder, G. P.; Holzapfel, W. L.; Hoover, S.; Hou, Z.; Hrubes, J. D.; Huang, N.; Hubmayr, J.; Irwin, K. D.; Keisler, R.; Knox, L.; Lee, A. T.; Leitch, E. M.; Li, D.; Liang, C.; Luong-Van, D.; McMahon, J. J.; Mehl, J.; Meyer, S. S.; Mocanu, L.; Montroy, T. E.; Natoli, T.; Nibarger, J. P.; Novosad, V.; Padin, S.; Pryke, C.; Reichardt, C. L.; Ruhl, J. E.; Saliwanchik, B. R.; Sayre, J. T.; Schaffer, K. K.; Smecher, G.; Stark, A. A.; Story, K. T.; Tucker, C.; Vanderlinde, K.; Vieira, J. D.; Wang, G.; Whitehorn, N.; Yefremenko, V.; Zahn, O.

    2015-05-01

    We present measurements of E-mode polarization and temperature-E-mode correlation in the cosmic microwave background using data from the first season of observations with SPTpol, the polarization-sensitive receiver currently installed on the South Pole Telescope (SPT). The observations used in this work cover 100 {{deg }2} of sky with arcminute resolution at 150 GHz. We report the E-mode angular auto-power spectrum (EE) and the temperature-E-mode angular cross-power spectrum (TE) over the multipole range 500 < ℓ ≤ 5000. These power spectra improve on previous measurements in the high-ℓ (small-scale) regime. We fit the combination of the SPTpol power spectra, data from Planck, and previous SPT measurements with a six-parameter ΛCDM cosmological model. We find that the best-fit parameters are consistent with previous results. The improvement in high-ℓ sensitivity over previous measurements leads to a significant improvement in the limit on polarized point-source power: after masking sources brighter than 50 mJy in unpolarized flux at 150 GHz, we find a 95% confidence upper limit on unclustered point-source power in the EE spectrum of {{D}\\ell }=\\ell (\\ell +1){{C}\\ell }/2π \\lt 0.40 μ {{K}2} at \\ell =3000, indicating that future EE measurements will not be limited by power from unclustered point sources in the multipole range \\ell \\lt 3600, and possibly much higher in \\ell .

  13. 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.

  14. 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.

  15. Effect of Recent Sea Surface Temperature Trends on the Springtime Cooling Trend of the Arctic Stratospheric Vortex

    NASA Astrophysics Data System (ADS)

    Garfinkel, Chaim; Oman, Luke; Hurwitz, Margaret

    2015-04-01

    The springtime Arctic polar vortex has cooled significantly over the satellite era, with consequences for ozone concentrations in the springtime transition season. The causes of this cooling trend are deduced by using comprehensive chemistry-climate model experiments. Approximately half of the satellite era early springtime cooling trend in the Arctic lower stratosphere was caused by changing sea surface temperatures (SSTs). An ensemble of experiments forced only by changing SSTs is compared to an ensemble of experiments in which both the observed SSTs and chemically- and radiatively-active trace species are changing. By comparing the two ensembles, it is shown that warming of Indian Ocean, North Pacific, and North Atlantic SSTs, and cooling of the tropical Pacific, have strongly contributed to recent polar stratospheric cooling in late winter and early spring, and to a weak polar stratospheric warming in early winter. When concentrations of ozone-depleting substances and greenhouse gases are fixed, polar ozone concentrations show a small but robust decline due to changing SSTs. Ozone changes are magnified in the presence of changing gas concentrations. The stratospheric changes can be understood by examining the tropospheric height and heat flux anomalies generated by the anomalous SSTs. Finally, recent SST changes have contributed to a decrease in the frequency of late winter stratospheric sudden warmings.

  16. Passive microwave sensing of coastal area waters

    NASA Technical Reports Server (NTRS)

    Kendall, B. M.

    1980-01-01

    A technique to remotely measure sea-surface temperature and salinity was demonstrated during the 1970's with a dual-frequency microwave radiometer system developed at the NASA Langley Research Center. Accuracies in temperature of 1 C and 1 part per thousand in salinity were obtained using state-of-the-art radiometers. Several aircraft programs for the measurement of coastal area waters demonstrating the application of the microwave radiometer system are discussed. Improvements of the microwave radiometer system during the 1980's and the design and development of new radiometer systems at other frequencies are outlined and related to potential applications.

  17. A physical algorithm to measure sea ice concentration from passive microwave remote sensing data

    NASA Astrophysics Data System (ADS)

    Tikhonov, V. V.; Repina, I. A.; Raev, M. D.; Sharkov, E. A.; Ivanov, V. V.; Boyarskii, D. A.; Alexeeva, T. A.; Komarova, N. Yu.

    2015-10-01

    A conceptually new algorithm of sea ice concentration retrieval in polar regions from satellite microwave radiometry data is discussed. The algorithm design favorably contrasts with that of known modern algorithms. Its design is based on a physical emission model of the "sea surface - sea ice - snow cover - atmosphere" system. No tie-points are used in the algorithm. All the calculation expressions are derived from theoretical modeling. The design of the algorithm minimizes the impact of atmospheric variability on sea ice concentration retrieval. Beside estimating sea ice concentration, the algorithm makes it possible to indicate ice areas with melting snow and melt ponds. The algorithm is simple to use, no complicated or time consuming calculations are involved.

  18. Warm Middle Jurassic-Early Cretaceous high-latitude sea-surface temperatures from the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Jenkyns, H. C.; Schouten-Huibers, L.; Schouten, S.; Sinninghe Damsté, J. S.

    2012-02-01

    Although a division of the Phanerozoic climatic modes of the Earth into "greenhouse" and "icehouse" phases is widely accepted, whether or not polar ice developed during the relatively warm Jurassic and Cretaceous Periods is still under debate. In particular, there is a range of isotopic and biotic evidence that favours the concept of discrete "cold snaps", marked particularly by migration of certain biota towards lower latitudes. Extension of the use of the palaeotemperature proxy TEX86 back to the Middle Jurassic indicates that relatively warm sea-surface conditions (26-30 °C) existed from this interval (∼160 Ma) to the Early Cretaceous (∼115 Ma) in the Southern Ocean, with a general warming trend through the Late Jurassic followed by a general cooling trend through the Early Cretaceous. The lowest sea-surface temperatures are recorded from around the Callovian-Oxfordian boundary, an interval identified in Europe as relatively cool, but do not fall below 25 °C. The early Aptian Oceanic Anoxic Event, identified on the basis of published biostratigraphy, total organic carbon and carbon-isotope stratigraphy, records an interval with the lowest, albeit fluctuating Early Cretaceous palaeotemperatures (∼26 °C), recalling similar phenomena recorded from Europe and the tropical Pacific Ocean. Extant belemnite δ18O data, assuming an isotopic composition of waters inhabited by these fossils of -1‰ SMOW, give palaeotemperatures throughout the Upper Jurassic-Lower Cretaceous interval that are consistently lower by ∼14 °C than does TEX86 and the molluscs likely record conditions below the thermocline. The long-term, warm climatic conditions indicated by the TEX86 data would only be compatible with the existence of continental ice if appreciable areas of high altitude existed on Antarctica, and/or in other polar regions, during the Mesozoic Era.

  19. Nature of the Jurassic Magnetic Quiet Zone revealed by the sea-surface, mid-water, and near-source magnetic sensor data in the western Pacific.

    NASA Astrophysics Data System (ADS)

    Tominaga, M.; Tivey, M.; Sager, W. W.

    2015-12-01

    The nature of the Jurassic Quiet Zone (JQZ) has been a long-standing debate in understanding Earth's geomagnetic field history and behavior. We present a coherent and likely globally significant marine magnetic reversal record for the JQZ by constructing a correlation of new and previously acquired magnetic anomaly profiles in the western Pacific. We obtained a high-resolution marine magnetic anomaly record using sea surface, mid-water (3-km level deep-towed), and near-bottom (Autonomous Underwater Vehicle (AUV)) profiles that targeted a spreading corridor in the Hawaiian lineation in 2011 (TN272 on R/V Thompson) and 2014 (SKQ2014S2 on R/V Sikuliaq). To extract crustal magnetic signals, the sea surface and mid-water magnetic data were corrected for ship-to-sensor offset, the diurnal effect, and the present-day ambient geomagnetic field. Mid-water data were upward continued to a constant 3 km level plane and to the sea surface. Near-bottom data were calibrated to remove the induced magnetic field by AUV Sentry, then corrected for IGRF and diurnal variations. We used these near-source data as an anchor for correlations with the sea surface and mid-water level data because of the AUV's superb inertial navigation and hydrodynamically stable, quiet platform environment. Our sea surface anomaly correlation with the previously established Japanese lineation sequence shows (i) an excellent correlation of anomaly shapes from M29 to M42; (ii) a remarkable similarity in anomaly amplitude envelope, which decreases back in time from M19 to M38, with a minimum at M41, then increases back in time from M42; and (iii) refined locations of pre-M25 lineations in the Hawaiian lineation set. Moreover, short-wavelength anomalies from the mid-water and near-bottom profiles show a strong similarity in the M37/M38 polarity attributes found both in the magnetostratigraphic and marine magnetic records, implying that rapid magnetic reversals were occurring at that time. The average reversal

  20. Passive microwave signatures of fractures and ridges in sea ice at 33. 6 GHz (vertical polarization) as observed in aircraft images

    SciTech Connect

    Farmer, L.D.; Eppler, D.T.; Lohanick, A.W. )

    1993-03-15

    An aircraft data set of coincident K[sub a] band (33.6 GHz, vertical polarization) passive microwave images and aerial photographs acquired in the Chukchi-Beaufort Sea region in March 1983 was analyzed to evaluate radiometric signatures of deformational features that occur in sea ice. A total of 115 fractures and 197 pressure ridges were examined with respect to physical appearance (relative age, snow cover, ice type, width, orientation) as observed in photographs, and radiometric character (brightness temperature, radiometric contrast with respect to adjacent ice, radiometric profile across the feature) as measured from digital passive microwave images. Of the deformational features that were observed in aerial photographs, 82% had radiometric signatures of sufficient contrast to be observed in passive microwave images. Fractures and ridges have equal chance of detection, but fractures cannot be distinguished from pressure ridges on the basis of brightness temperature, radiometric contrast, or characteristics of radiometric profiles measured across these features. Radiometric signatures of both fractures and ridges are more likely to be radiometrically warmer (as opposed to cooler) than adjacent ice, which suggests that saline ice is a significant constituent of most deformational features. New ridges are more likely to be radiometrically warmer than old ridges, probably because brine drains from the ridge as it ages (which reduces emissivity) and snow accumulates in drifts along the ridge trend (which enhances scattering). However, brightness temperatures of snow-covered ridges extend across a range that is approximately 15 K cooler, and 10 K warmer than the range observed for snow-free ridges. Old features show higher radiometric contrast with respect to adjacent ice than new features, which increases their probability of detection. 36 refs., 13 figs., 4 tabs.

  1. Ultra-low phase-noise microwave generation using a diode-pumped solid-state laser based frequency comb and a polarization-maintaining pulse interleaver.

    PubMed

    Portuondo-Campa, Erwin; Buchs, Gilles; Kundermann, Stefan; Balet, Laurent; Lecomte, Steve

    2015-12-14

    We report ultra-low phase-noise microwave generation at a 9.6 GHz carrier frequency from optical frequency combs based on diode-pumped solid-state lasers emitting at telecom wavelength and referenced to a common cavity-stabilized continuous-wave laser. Using a novel fibered polarization-maintaining pulse interleaver, a single-oscillator phase-noise floor of -171 dBc/Hz at 10 MHz offset frequency has been measured with commercial PIN InGaAs photodiodes, constituting a record for this type of detector. Also, a direct optical measurement of the stabilized frequency combs' timing jitter was performed using a balanced optical cross correlator, allowing for an identification of the origin of the phase-noise limitations in the system. PMID:26699033

  2. REIONIZATION ON LARGE SCALES. III. PREDICTIONS FOR LOW-l COSMIC MICROWAVE BACKGROUND POLARIZATION AND HIGH-l KINETIC SUNYAEV-ZEL'DOVICH OBSERVABLES

    SciTech Connect

    Battaglia, N.; Natarajan, A.; Trac, H.; Cen, R.; Loeb, A.

    2013-10-20

    We present new predictions for cosmic microwave background (CMB) temperature (on small angular scales) and polarization (on large angular scales) anisotropies induced during the epoch of reionization (EoR). Using a novel method calibrated from radiation-hydrodynamic simulations, we model the EoR in large volumes (L ∼> 2 Gpc h {sup –1}). We find that the EoR contribution to the kinetic Sunyaev-Zel'dovich power spectrum (patchy kSZ) ranges between ∼0.6-2.8 μK{sup 2} at l = 3000 for the explored parameter space. For each model, the patchy kSZ power spectrum is calculated from three large 15° × 15° maps for better numerical convergence. Decreasing the size of these maps biases the overall patchy kSZ power to higher values. We find that the amplitude of the patchy kSZ power spectrum at l = 3000 follows simple scalings of D{sub l=3000}{sup kSZ}∝ z-bar and D{sub l=3000}{sup kSZ}∝Δ{sub z}{sup 0.51} for the mean redshift ( z-bar ) and duration (Δ{sub z}) of reionization. Using the constraints on z-bar from the Wilkinson Microwave Anisotropy Probe seven year results and the lower limit on Δ{sub z} from EDGES, we find a lower limit of ∼0.4 μK{sup 2} at l = 3000. Planck will infer the mean redshift from the Thomson optical depth imprinted in the low-l polarization power spectrum. Future measurements of the high-l CMB power spectrum from the Atacama Cosmology Telescope and South Pole Telescope should detect the patchy kSZ signal if the cross correlation between the thermal SZ effect and the cosmic infrared background is constrained. We show that the combination of temperature and polarization measurements constrains both z-bar and Δ{sub z}. The patchy kSZ maps, power spectra templates, and the polarization power spectra will be publicly available.

  3. A Unified Model of the Fermi Bubbles, Microwave Haze, and Polarized Radio Lobes: Reverse Shocks in the Galactic Center’s Giant Outflows

    NASA Astrophysics Data System (ADS)

    Crocker, Roland M.; Bicknell, Geoffrey V.; Taylor, Andrew M.; Carretti, Ettore

    2015-08-01

    The Galactic center’s giant outflows are manifest in three different, nonthermal phenomena: (1) the hard-spectrum, γ-ray “Fermi bubbles” emanating from the nucleus and extending to | b| ˜ 50^\\circ ; (2) the hard-spectrum, total-intensity microwave (˜20-40 GHz) “haze” extending to | b| ˜ 35^\\circ in the lower reaches of the Fermi bubbles; and (3) the steep-spectrum, polarized, “S-PASS” radio (˜2-20 GHz) lobes that envelop the bubbles and extend to | b| ˜ 60^\\circ . We find that the nuclear outflows inflate a genuine bubble in each Galactic hemisphere that has the classical structure, working outward, of reverse shock, contact discontinuity (CD), and forward shock. Expanding into the finite pressure of the halo and given appreciable cooling and gravitational losses, the CD of each bubble is now expanding only very slowly. We find observational signatures in both hemispheres of giant, reverse shocks at heights of ˜1 kpc above the nucleus; their presence ultimately explains all three of the nonthermal phenomena mentioned above. Synchrotron emission from shock-reaccelerated cosmic-ray electrons explains the spectrum, morphology, and vertical extent of the microwave haze and the polarized radio lobes. Collisions between shock-reaccelerated hadrons and denser gas in cooling condensations that form inside the CD account for most of the bubbles’ γ-ray emissivity. Inverse Compton emission from primary electrons contributes at the 10%-30% level. Our model suggests that the bubbles are signatures of a comparatively weak but sustained nuclear outflow driven by Galactic center star formation over ≳few × 108 yr.

  4. Nonlinear aspects of sea surface temperature in Monterey Bay

    NASA Astrophysics Data System (ADS)

    Breaker, Laurence C.

    2006-04-01

    Nonlinear aspects of sea surface temperature (SST) in Monterey Bay are examined, based on an 85-year record of daily observations from Pacific Grove, California. Oceanic processes that affect the waters of Monterey Bay are described, processes that could contribute to nonlinearity in the record. Exploratory data analysis reveals that the record at Pacific Grove is non-Gaussian and, most likely, nonstationary. A more recent test for stationarity based on a power law approximation to the slope of the power spectrum indicates that the record is stationary for frequencies up to ∼8 cycles per year (∼45 days), but nonstationary at higher frequencies. To examine the record at Pacific Grove for nonlinear behavior, third-order statistics, including the skewness, statistical measures of asymmetry, the bicorrelation, and the bispectrum, were employed. The bicorrelation revealed maxima located approximately 365 days apart, reflecting a nonlinear contribution to the annual cycle. Based on a 365-day moving window, the running skewness is positive almost 80% of the time, reflecting the overall impact of warming influences. The asymmetry is positive approximately 75% of the time, consistent with the asymmetric shape of the mean annual cycle. Based on the skewness and asymmetry, nonlinearities in the record, when they occur, appear to be event-driven with time scales possibly as short as several days, to several years. In many cases, these events are related to warm water intrusions into the bay, and El Niño warming episodes. The power spectrum indicates that the annual cycle is a dominant source of variability in the record and that there is a relatively strong semiannual component as well. To determine whether or not the annual and semiannual cycles are harmonically related, the bispectrum and bicoherence were calculated. The bispectrum is nonzero, providing a strong indication of nonlinearity in the record. The bicoherence indicates that the annual cycle is a major source

  5. Effects of the Antenna Aperture on Remote Sensing of Sea Surface Salinity at L-Band

    NASA Technical Reports Server (NTRS)

    Dinnat, Emmanuel P.; LeVine, David M.

    2006-01-01

    Remote sensing of sea surface salinity with sufficient accuracy to meet the needs of global oceanography is a challenging task. The global variability of the salinity signal in the open ocean is only a few Kelvin even at L-band and an accuracy on the order of 0.1K is desired to study the influence of salinity on ocean circulation and energy exchange with the atmosphere. On the other hand, resolution is not an issue for understanding the dynamics of the open ocean where scales of hundreds of km are not uncommon. This permits remote sensing with large antenna footprints and spatial averaging to reduce noise. However, antennas with large footprints introduce other problems. For example, the angle of incidence and hence the brightness temperature varies over the footprint. Similarly, the polarization of brightness temperature relative to the antenna ports changes. Studies have been conducted using antenna patterns representative of the antenna that will be flown on the Aquarius mission to examine these effects. Aquarius is a pushbroom style radiometer with three beams looking across track away from the sun. The beams are at incidences angles (at the spacecraft) of about 26.5, 34 and 40 degrees each with a half-power beam width of about 5.8 degrees. It is shown that the measured brightness temperature is biased relative to the value at boresight because of changes across the field of view. The bias can be as much as 4K and positive or negative depending on polarization. Polarization mixing because of the variations of the local plane of incidence across the footprint also occur and can result in biased polarimetric measurements. A bias in the third Stokes parameter of as much as 0.4K is possible. Such effects may affect algorithms that use the third Stokes parameter to correct for Faraday rotation. Another issue associated with the antenna is sun glint. This is an issue determined by surface roughness and antenna sidelobes. Examples will be given for the random

  6. Sea surface temperatures in the North Atlantic Ocean from 30ka to 10ka

    NASA Astrophysics Data System (ADS)

    Barrack, Kerr; Greenop, Rosanna; Burke, Andrea; Barker, Stephen; Chalk, Thomas; Crocker, Anya

    2016-04-01

    Some of the most striking features of the Late Pleistocene interval are the rapid changes in climate between warmer interstadial and cold stadial periods which, when coupled, are termed Dansgaard-Oeschger (D-O) events. This shift between warm and cold climates has been interpreted to result from changes in the thermohaline circulation (Broecker et al., 1985) triggered by, for instance, freshwater input from the collapse of the Laurentide ice sheet (Zahn et al., 1997). However, a recent study suggests that major ice rafting events cannot be the 'trigger' for the centennial to millennial scale cooling events identified over the past 500kyr (Barker at al., 2015). Polar planktic foraminiferal and lithogenic/terrigenous grain counts reveal that the southward migration of the polar front occurs before the deposition of ice rafted debris and therefore the rafting of ice during stadial periods. Based upon this evidence, Barker et al. suggest that the transition to a stadial state is a non-linear response to gradual cooling in the region. In order to test this hypothesis, our study reconstructs sea surface temperature across D-O events and the deglaciation in the North Atlantic between 30ka and 10ka using Mg/ Ca paleothermometry in Globigerina bulloides at ODP Sites 980 and 983 (the same sites as used in Barker et al., 2015) with an average sampling resolution of 300 years. With our new record we evaluate the timing of surface ocean temperature change, frontal shift movement, and ice rafting to investigate variations in the temperature gradient across the polar front over D-O events. References: Barker, S., Chen, J., Gong, X., Jonkers, L., Knorr, G., Thornalley, D., 2015. Icebergs not the trigger for North Atlantic cold events. Nature, 520(7547), pp.333-336. Broecker, W.S., Peteer, D.M., Rind, D., 1985. Does the ocean-atmosphere system have more than one stable mode of operation? Nature, 315 (6014), pp.21-26. Zahn, R., Schönfeld, J., Kudrass, H.-R., Park, M

  7. Aquarius: An Instrument to Monitor Sea Surface Salinity from Space

    NASA Technical Reports Server (NTRS)

    LeVine, D. M.; Lagerloef, G. S .E.; Colomb, R.; Yueh, S.; Pellerano, F.

    2007-01-01

    Aquarius is a combined passive/active L-band microwave instrument that is being developed to map the salinity field at the surface of the ocean from space. The data will support studies of the coupling between ocean circulation, global water cycle, and climate. Aquarius is part of the Aquarius/SAC-D mission, which is a partnership between the U.S. (National Aeronautics and Space Administration) and Argentina (CONAE). The primary science objective of this mission is to monitor the seasonal and interannual variation of the large-scale features of the surface salinity field in the open ocean with a spatial resolution of 150 km and a retrieval accuracy of 0.2 psu globally on a monthly basis.

  8. New areas of polar lows over the Arctic as a result of the decrease in sea ice extent

    NASA Astrophysics Data System (ADS)

    Zabolotskikh, E. V.; Gurvich, I. A.; Chapron, B.

    2015-12-01

    Three mesocyclones (MCs) over the Russian (Eastern) Arctic are investigated using multispectral satellite remote sensing data, surface analysis maps, and reanalysis data. Advanced retrieval algorithms are used for estimating the geophysical parameter from satellite passive microwave measurements. These methods allow reconstructing in full the geophysical parameter fields characterizing polar lows. Synoptic analysis along with cloud image, atmospheric water vapor content, cloud liquid water content, and sea surface wind speed field analysis show that, while the Arctic sea ice retreats, new areas of open water appear where MCs can arise. A detailed study of several polar low cases reveals the typical conditions of their formation and development. Further studies are in demand due to the danger of MC extreme events for navigation, transport, and fishery operations in these unexplored regions.

  9. Sea surface temperature variability of the Peru-Chile Current during the previous ten interglacials

    NASA Astrophysics Data System (ADS)

    Caniupan, M.; Martinez-Mendez, G.; Lamy, F.; Hebbeln, D.; Mohtadi, M.; Pantoja, S.

    2014-12-01

    There are several interglacial periods during the Quaternary that were characterized by climates warmer than present and higher sea level and thus may serve as analogues for future global warming scenarios. These include Marine Isotope Stages (MIS) 5e, 9c and 11c. Little is known about past sea surface temperatures (SST) during these warm intervals in the Southern Hemisphere, particularly along the Peru-Chile Current (PCC) which plays a critical role in the Southern Hemisphere surface circulation as it connects the low and high latitudes by transporting sub-polar water masses and thus, a high-latitude climate signal towards the tropics. Here, we present new high-resolution alkenone-derived SST records from marine sediment cores located beneath the PCC. Core GeoB15016 was recovered from off northern Chile (27.5°S; 71.1°W) with the seafloor drill rig MARUM-MeBo. We analyzed the ca. 60 meters composite depth complemented by gravity core GeoB3375-1 (27.5°S; 71.3°W) for the upper part to generate a continuous record that extends back to 970 ka BP. Our record is the first continuous SST reconstruction from the Chilean margin extending back to MIS 25. SST varies between ~8°C and ~20°C over the past ~970 ka. Glacial-interglacial SST amplitudes are in the order of 6°C (see Groeneveld's et al. contribution for Mg/Ca-derived Glacial SST estimations). During MIS 5e, 7e, 9c and 11c, the record reaches SST maxima which are ca. 3ºC warmer than present annual mean SST in the area. Our results suggest a substantial warming of the PCC over past interglacials that may reflect reduced advection of subantarctic surface water from the south and/or enhanced tropical influence from the north.

  10. Arctic sea surface height variability and change from satellite radar altimetry and GRACE, 2003-2014

    NASA Astrophysics Data System (ADS)

    Armitage, Thomas W. K.; Bacon, Sheldon; Ridout, Andy L.; Thomas, Sam F.; Aksenov, Yevgeny; Wingham, Duncan J.

    2016-06-01

    Arctic sea surface height (SSH) is poorly observed by radar altimeters due to the poor coverage of the polar oceans provided by conventional altimeter missions and because large areas are perpetually covered by sea ice, requiring specialized data processing. We utilize SSH estimates from both the ice-covered and ice-free ocean to present monthly estimates of Arctic Dynamic Ocean Topography (DOT) from radar altimetry south of 81.5°N and combine this with GRACE ocean mass to estimate steric height. Our SSH and steric height estimates show good agreement with tide gauge records and geopotential height derived from Ice-Tethered Profilers. The large seasonal cycle of Arctic SSH (amplitude ˜5 cm) is dominated by seasonal steric height variation associated with seasonal freshwater fluxes, and peaks in October-November. Overall, the annual mean steric height increased by 2.2 ± 1.4 cm between 2003 and 2012 before falling to circa 2003 levels between 2012 and 2014 due to large reductions on the Siberian shelf seas. The total secular change in SSH between 2003 and 2014 is then dominated by a 2.1 ± 0.7 cm increase in ocean mass. We estimate that by 2010, the Beaufort Gyre had accumulated 4600 km3 of freshwater relative to the 2003-2006 mean. Doming of Arctic DOT in the Beaufort Sea is revealed by Empirical Orthogonal Function analysis to be concurrent with regional reductions in the Siberian Arctic. We estimate that the Siberian shelf seas lost ˜180 km3 of freshwater between 2003 and 2014, associated with an increase in annual mean salinity of 0.15 psu yr-1. Finally, ocean storage flux estimates from altimetry agree well with high-resolution model results, demonstrating the potential for altimetry to elucidate the Arctic hydrological cycle.

  11. MICROWAVES IN ORGANIC SYNTHESIS

    EPA Science Inventory

    The effect of microwaves, a non-ionizing radiation, on organic reactions is described both in polar solvents and under solvent-free conditions. The special applications are highlighted in the context of solventless organic synthesis which involve microwave (MW) exposure of neat r...

  12. Seasat scanning multichannel microwave radiometer - Results of the Gulf of Alaska workshop

    NASA Technical Reports Server (NTRS)

    Lipes, R. G.; Njoku, E. G.; Riley, A. L.; Bernstein, R. L.; Cardone, V. J.; Katsaros, K. B.; Ross, D. B.; Swift, C. T.; Wentz, F. J.

    1979-01-01

    Scanning multichannel microwave radiometer results obtained by the Gulf of Alaska Seasat Experiment Workshop are reported. The Seasat SMMR provided data from five channels operating at 6.6, 10.7, 18, 21, and 37 GHz at vertical and horizontal polarizations. Two preliminary algorithms were used to retrieve geophysical parameters from the data: the Wentz algorithm (Bierman et al., 1978) based on a theoretically derived function for computing brightness temperatures and the Wilheit algorithm, based on statistical relationships between brightness temperatures and the geophysical parameters obtained from an ensemble of realistic sea-surface temperature values, wind speeds, atmospheric temperature profiles, water vapor profiles and cloud models. In spite of the immaturity of the data-processing algorithms, results are encouraging. For open ocean, rain-free cells of high-quality surface truth wind determinations display standard deviations of 3 m/sec about a bias of 1.5 m/sec. The sea-surface temperature exhibits a standard deviation of about 1.5 deg C about a bias of 3 to 5 deg C under a variety of meteorological conditions.

  13. The Sensitivity of African Easterly Waves to Eastern Tropical Atlantic Sea-Surface Temperatures

    NASA Technical Reports Server (NTRS)

    Druyan, Leonard M.; Fulakeza, Matthew

    2011-01-01

    The results of two regional atmospheric model simulations are compared to assess the influence of the eastern tropical Atlantic sea-surface temperature maximum on local precipitation, transient easterly waves and the West African summer monsoon. Both model simulations were initialized with reanalysis 2 data (US National Center for Environmental Prediction and Department of Energy) on 15 May 2006 and extended through 6 October 2006, forced by synchronous reanalysis 2 lateral boundary conditions introduced four times daily. One simulation uses 2006 reanalysis 2 sea-surface temperatures, also updated four times daily, while the second simulation considers ocean forcing absent the sea-surface temperature maximum, achieved here by subtracting 3 K at every ocean grid point between 0 and 15 N during the entire simulation. The simulation with 2006 sea-surface temperature forcing produces a realistic distribution of June-September mean precipitation and realistic westward propagating swaths of maximum rainfall, based on validation against Tropical Rainfall Measuring Mission (TRMM) estimates. The simulation without the sea-surface temperature maximum produces only 57% of the control June-September total precipitation over the eastern tropical Atlantic and about 83% of the Sahel precipitation. The simulation with warmer ocean temperatures generates generally stronger circulation, which in turn enhances precipitation by increasing moisture convergence. Some local precipitation enhancement is also attributed to lower vertical thermal stability above the warm water. The study shows that the eastern tropical Atlantic sea-surface temperature maximum enhances the strength of transient easterly waves and broadens the spatial extent of associated precipitation. However, large-scale circulation and its interaction with the African continent, and not sea-surface temperatures, control the timing and trajectories of the waves.

  14. Global monitoring of Sea Surface Salinity with Aquarius

    NASA Technical Reports Server (NTRS)

    Lagerloef, G. S. E.; LeVine, D. M.; Chao, Yi; Colomb, R.; Nollmann, I.

    2005-01-01

    Aquarius is a microwave remote sensing system designed to obtain global maps of the surface salinity field of the oceans from space. It will be flown on the Aquarius/SAC-D mission, a partnership between the USA (NASA) and Argentina (CONAE) with launch scheduled for late in 2008. The objective of Aquarius is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean. This will provide data to address scientific questions associated with ocean circulation and its impact on climate. For example, salinity is needed to understand the large scale thermohaline circulation, driven by buoyancy, which moves large masses of water and heat around the globe. Of the two variables that determine buoyancy (salinity and temperature), temperature is already being monitored. Salinity is the missing variable needed to understand this circulation. Salinity also has an important role in energy exchange between the ocean and atmosphere, for example in the development of fresh water lenses (buoyant water that forms stable layers and insulates water below from the atmosphere) which alter the air-sea coupling. Aquarius is a combination radiometer and scatterometer (radar) operating at L-band (1.413 GHz for the radiometer and 1.26 GHz for the scatterometer). The primary instrument,for measuring salinity is the radiometer which is able to detect salinity because of the modulation salinity produces on the thermal emission from sea water. This change is detectable at the long wavelength end of the microwave spectrum. The scatterometer will provide a correction for surface roughness (waves) which is one of the greatest unknowns in the retrieval. The sensor will be in a sun-synchronous orbit at about 650 km with equatorial crossings of 6am/6pm. The antenna for these two instruments is a 3 meter offset fed reflector with three feeds arranged in pushbroom fashion looking away from the sun toward the shadow side of the orbit to

  15. Simulation and Prediction of North Pacific Sea Surface Temperature

    NASA Astrophysics Data System (ADS)

    Lienert, Fabian

    The first part of this thesis is an assessment of the ability of global climate models to reproduce observed features of the leading Empirical Orthogonal Function (EOF) mode of North Pacific sea surface temperature (SST) anomalies known as the Pacific Decadal Oscillation (PDO). My results are that 1) the models as group produce a realistic pattern of the PDO. The simulated variance of the PDO index is overestimated by roughly 30%. 2) The tropical influence on North Pacific SSTs is biased systematically in these models. The simulated response to El Nino-Southern Oscillation (ENSO) forcing is delayed compared to the observed response. This tendency is consistent with model biases toward deeper oceanic mixed layers in winter and spring and weaker air-sea feedbacks in the winter half-year. Model biases in mixed layer depths and air-sea feedbacks are also associated with a model mean ENSO-related signal in the North Pacific whose amplitude is overestimated by roughly 30%. Finally, model power spectra of the PDO signal and its ENSO-forced component are "redder" than observed due to errors originating in the tropics and extratropics. 3) The models are quite successful at capturing the influence of both the tropical Pacific related and the extratropical part of the PDO on North American surface temperature. 4) The models capture some of the influence of the PDO on North American precipitation mainly due to its tropical Pacific related part. In the second part of this thesis, I investigate the ability of one such coupled ocean-atmosphere climate model, carefully initialized with observations, to dynamically predict the future evolution of the PDO on seasonal to decadal time scales. I find that 1) CHFP2 is successful at predicting the PDO at the seasonal time scale measured by mean-square skill score and correlation skill. Weather "noise" unpredictable at the seasonal time scale generated by substantial North Pacific storm track activity that coincides with a shallow oceanic

  16. GREENER SYNTHETIC TRANSFORMATIONS USING MICROWAVES

    EPA Science Inventory

    Microwave irradiation has been used for a variety of organic transformations wherein chemical reactions are expedited because of selective adsorption of microwave (MW) energy by polar molecules, non-polar molecules being inert to the MW dielectric loss. The MW application under s...

  17. An Examination of the Sea Surface Salinity - Fresh Water Flux Relationship Using Satellite Observations

    NASA Astrophysics Data System (ADS)

    Xie, P.; Kumar, A.; Xue, Y.; Liu, W. T.

    2014-12-01

    Relationship between the sea surface salinity (SSS) and the oceanic fresh water flux (E-P) is examined using the SSS retrievals derived from the passive microwave (PMW) observations aboard the SMOS and Aquarius satellites, the CMORPH integrated satellite precipitation estimates (P) and the evaporation data (E) produced by the NCEP Climate Forecast System (CFS) reanalysis. Preprocessing is performed to construct gridded fields of SSS, P, and E on a 1o lat/lon grid over the global oceans and at a 30-min time resolution for a 54-month period from January 2010 to June 2014. Relationships between the SSS observed at a point in time and the P, E, and P-E at the same grid box accumulated over various time periods ending at the SSS observation time are examined. As a first step, we focused our investigation on an oceanic area over the central equatorial Pacific (10oS-10oN; 180o-160oW) where SSS is not influenced by the river runoffs. Our preliminary results show clear linear relationship between the satellite-observed skin SSS and the fresh water flux over the region. The Aquarius observed instantaneous SSS presents a correlation of ~0.4 with the E-P accumulated over the 30-min period of the SSS observations. The correlation between the instantaneous SSS and the E-P drops with the accumulation period for E-P, down to 0.36 for 6-hourly accumulated E-P. The Correlation, however, bounces back and improves with the E-P accumulation period longer than 6 hours, reaching to ~0.7 for an accumulation time period of 30 days. The existence of the minimum correlation between the instantaneous SSS and the E-P accumulation over a 6-hour period suggests the involvement of air-sea interaction and oceanic processes on multiple time scales in the manner E-P influences to the SSS variations. Among the two primary components of the fresh water flux, precipitation dominates the influences on the SSS. Further analysis is under way to repeat the examination for different regions to examine the

  18. Electromagnetic scattering and Doppler spectrum simulation of time-varying oil-covered nonlinear sea surface

    NASA Astrophysics Data System (ADS)

    Yang, Pengju; Guo, Lixin; Jia, Chungang

    2016-01-01

    Based on the model of Lombardini et al. [J. Atmos. Ocean. Technol. 6(6), 882-890 (1989)], which can predict the hydrodynamic damping of rough sea surfaces in the presence of oil films, the influence of sea slicks on the sea surface roughness spectrum and sea surface geometrical structure is examined briefly in the present study. On this basis, the influence of sea slicks on the angular distribution of the bistatic scattering coefficient of sea surfaces and the Doppler spectrum signature of backscattered radar sea-echo is investigated in detail based on a frequency-domain numerical method of the parallel fast multiple method. Simulation results show that Doppler spectrum signatures including Doppler shift and spectral bandwidth of radar sea-echo are significantly affected by sea slicks, which are qualitatively consistent with wave-tank or open sea measurements. Moreover, simulation results indicate that the Doppler spectrum signature is a promising technique for remote sensing of oil films floating on sea surfaces.

  19. Impact of Typhoon-induced sea surface cooling on the track of next Typhoon

    NASA Astrophysics Data System (ADS)

    Ando, Y.; Horiguchi, M.; Kodera, K.; Tachibana, Y.; Yamazaki, K.

    2015-12-01

    Typhoons (TCs) MATMO, HALONG, and NAKRI (2014), which caused Japan catastrophic disaster, landed the western part of Japan. The TCs came to Japan one after another during late July to early August 2014. The tracks of these TCs were similar, i.e., the TCs followed the western edge of the subtropical northwestern Pacific high (SNPH). However, the tracks gradually reached to Japan, which were associated with weakening the westward expansion of the SNPH. It was found that the changes in westward expansion of the SNPH were associated with TC-induced sea surface cooling of previous Typhoon. It has previously been reported that TC-induced sea surface cooling is mainly caused by Ekman upwelling and vertical turbulent mixing. The TCs MATMO, HALONG, and NAKRI passed around the Philippines, and induced sea surface cooling of this area. The sea surface temperatures of this area are important for Pacific-Japan pattern, which was associated with the westward expansion of the SNPH. Consequently, previous Typhoon induced sea surface cooling around the Philippines, which weakening the westward expansion of the SNPH. Then, the tracks of next Typhoon were changed, and gradually reached to Japan.

  20. Sea Surface Wind Field by X-Band TerraSAR-X and Tandem-X

    NASA Astrophysics Data System (ADS)

    Lehner, Susanne; Li, Xiaoming; Ren, Yongzheng; He, Mingxia

    2013-01-01

    In the present study, we present the newly developed Geophysical Model Function (GMF), denoted XMOD2, to retrieve the sea surface wind field from X-band TerraSAR-X/Tandem-X (TS-X/TD-X) data. In contrary to the previous XMOD1, XMOD2 is based on a nonlinear GMF, and moreover it also depicts the difference between upwind and downwind of the sea surface backscatter. By exploiting 371 collocations, the retrieved TS-X/TD-X sea surface wind speed by XMOD2 agrees well with in situ buoy measurements with a bias of 0.39 m/s, an RMSE of 1.52 m/s and a scatter index (SI) of 16.1%. To evaluate the sea surface wind field retrieved from X-band SAR, we conducted a joint campaign in the South China Sea in August, 2011. Examples of sea surface wind field retrieved from the TS-X/TD-X data acquired in the campaign are shown for demonstration.

  1. Investigation of the foam influence on the wind-wave momentum exchange and cross-polarization microwave radar return within laboratory modeling of atmosphere-ocean boundary layer

    NASA Astrophysics Data System (ADS)

    Sergeev, Daniil; Troitskaya, Yuliya; Vdovin, Maxim; Ermoshkin, Alexey

    2016-04-01

    The effect of foam presence on the transfer processes and the parameters of the surface roughness within the laboratory simulation of wind-wave interaction was carried out on the Thermostratified Wind-Wave Tank (TSWiWaT) IAP, using a specially designed foam generator. The parameters of air flow profiles and waves elevation were measured with scanning Pitot gauge and wire wave gauges respectively in the range of equivalent wind speed U10 from 12 to 38 m/s (covering strong winds) on the clean water and with foam. It was shown that the foam reduces the amplitudes and slopes of the waves in comparison with the clean water in the hole range of wind speeds investigated, and the peak frequency and wave numbers remain almost constant. The drag coefficient calculating by profiling method demonstrated similar behavior (almost independent on U10) for case of foam and increased compared with clear water, particularly noticeable for low wind speeds. Simultaneously the investigations of influence of the foam on the peculiarity of the microwave radio back scattering of X-diapason was investigated. These measurements were carried for different sensing angles (30, 40 i 50 degrees from vertical) and for four polarizations: co-polarized HH and VV, and de-polarized HV and VH. It was shown that foam leads to decrease of specific radar cross section of the wavy surface in comparison with clean water. The work was supported by the Russian Foundation for Basic Research (grants No. 15-35-20953, 14-05-00367, 16-55-52022) and project ASIST of FP7. The experiment is supported by Russian Science Foundation (Agreement No. 15-17-20009), radilocation measurments are partially supported by Russian Science Foundation (Agreement No. 14-17-00667).

  2. Aquarius: A Mission to Monitor Sea Surface Salinity from Space

    NASA Technical Reports Server (NTRS)

    LeVine, D. M.; Lagerloef, G. S. E.; Pellerano, F.; Yueh, S.; Colomb, R.

    2006-01-01

    Aquarius is a combination radiometer and scatterometer (radar) operating at L-band (1.413 GHz for the radiometer and 1.26 GHz for the scatterometer). The primary instrument for measuring salinity is the radiometer. The scatterometer will provide a correction for surface roughness (waves) which is one of the largest potential sources of error in the retrieval. Unique features of the sensor are the large reflector (2.5 meter offset fed reflector with three feeds), polarimetric operation, and the tight thermal control. The three feeds produce three beams arranged to image in pushbroom fashion looking to the side of the orbit away from the sun to avoid sunglint. Polarimetric operation is included to assist in correcting for Faraday rotation which can be important at L-band. The tight thermal control is necessary to meet stability requirements (less than 0.12K drift over 7 days) which have been imposed to assist in meeting the science requirements for the retrieval of surface salinity (0.2 psu). The sensor will be in a sun-synchronous orbit at about 650 km with equatorial crossings of 6ad6pm (ascending at 6 pm). The objective is to monitor the seasonal and interannual variation of the large scale features of the surface salinity field in the open ocean. To accomplish this, the measurement goals are a spatial resolution of 100 km and retrieval accuracy of 0.2 psu globally on a monthly basis. Aquarius is being developed by NASA and is a partnership between JPL and the Goddard Space Flight Center. The SAC-D mission is being developed by CONAE and will include the spacecraft and several additional instruments, including visible and infrared cameras and a microwave radiometer to monitor rain and wind velocity over the oceans, and sea ice.

  3. Cosmic Microwave Background Polarization Detector with High Efficiency, Broad Bandwidth, and Highly Symmetric Coupling to Transition Edge Sensor Bolometers

    NASA Technical Reports Server (NTRS)

    Wollack, E.; Cao, N.; Chuss, D.; Denis, K.; Hsieh, W.-T.; Moseley, S. Harvey; Schneider, G.; Stevenson, T.; Travers, D.; U-yen, K.

    2008-01-01

    Four probe antennas transfer signals from waveguide to microstrip lines. The probes not only provide broadband impedance matching, but also thermally isolate waveguide and detector. In addition, we developed a new photonic waveguide choke joint design, with four-fold symmetry, to suppress power leakage at the interface. We have developed facilities to test superconducting circuit elements using a cryogenic microwave probe station, and more complete systems in waveguide. We used the ring resonator shown below to measure a dielectric loss tangent < 7x10(exp -4) over 10 - 45 GHz. We have combined component simulations to predict the overall coupling from waveguide modes to bolometers. The result below shows the planar circuit and waveguide interface can utilize the high beam symmetry of HE11 circular feedhorns with > 99% coupling efficiency over 30% fractional bandwidth.

  4. Surface heat flux parameterizations and tropical Pacific sea surface temperature simulations

    SciTech Connect

    Giese, B.S. University Corp. for Atmospheric Research, Boulder, CO ); Cayan, D.R. )

    1993-04-15

    The authors report on a study of the problem of getting good model results for the sea surface temperature in the tropical Pacific ocean. The tropical Pacific is particularly important because of its size, the large areas of warm surface temperature, its impact on global atmospheric circulation, and the fact that it serves as an indicator of climatic variations. To simulate sea surface temperature it is necessary to have an energy budget which fits into a general ocean circulation model. The main input, from solar flux, is not well known in the tropical Pacific. The authors use two different models to describe the latent flux and the radiative flux at the sea surface. Parameters of concern include the relative humidity, air-sea temperature difference, latent heat formulae, and radiative heat flux. They use these parameters in their models in different ways, and compare results with measurement sets from the Tropical Pacific.

  5. Deghosting towed streamer data in τ/p domain based on rough sea surface reflectivity

    NASA Astrophysics Data System (ADS)

    Zhang, Xing-Yan; Pan, Dong-Ming; Shi, Wen-Ying; Fang, Zhong-Yu; Dan, Zhi-Wei; Zhang, Li-Xia

    2015-12-01

    Currently, the deghosting of towed streamer seismic data assumes a flat sea level and a sea-surface reflection coefficient of -1; this decreases the precision of deghosting. A new method that considers the rough sea surface is proposed to suppress ghost reflections. The proposed deghosting method obtains the rough sea surface reflection coefficient using Gaussian statistics, and calculates the optimized deghosting operator in the τ/ p domain. The proposed method is closer to the actual sea conditions, offers an improved deghosting operator, removes the ghost reflections from marine towed seismic data, widens the bandwidth and restores the low-frequency information, and finally improves the signal-tonoise ratio and resolution of the seismic data.

  6. Investigation of Optical Flow Techniques for Extracting Non-Rigid Sea Surface Currents

    NASA Astrophysics Data System (ADS)

    Ghalenoei, E.; Sharifi, M. A.; Hasanlou, M.

    2014-10-01

    This paper is about performance evaluation of two optical flow (OF) methods for extracting sea surface curved motions like eddies. By incorporating a simple matrix and its rotation in programming procedure, curved motion can be obtained. These two OF methods are Horn/Schunk and Lucas/Kanade. The Horn/Schunk method depends on a smoothness parameter (α) and when it changes, smoothness and reality change too. The Lucas/Kanade method is more complex than previous one. It depends on two parameters, smoothness parameter (Sigma) and window size (Win). Different values for Win and Sigma change smoothness and reality of the flows. Sea surface currents are extracted from two sequential sea surface temperature (SST) images by using OF methods. By using these methods and selecting the appropriate parameters like smoothness (for Horn/Schunk) and window size and smoothness (for Lucas/Kanade) extracting real flows or smooth flows are possible and investigated in this paper.

  7. Lightning in the Mediterranean and its relation with sea-surface temperature

    NASA Astrophysics Data System (ADS)

    Kotroni, V.; Lagouvardos, K.

    2016-03-01

    Here we present the analysis of lightning activity over the Mediterranean, based on a 10 year long dataset (2005-2014) provided by the ZEUS long-range lightning detection system. The major hot-spots of lightning activity are identified, with a clear predominance during the warm period of the year over land in the vicinity of the major topographic features of the area. Special emphasis is also given on the discussion of the seasonal distribution of lightning. In addition, we investigate the relationship of lightning with sea-surface temperature, obtained by high-resolution satellite measurements and we conclude that the number of lightning strokes is positively correlated with the sea-surface temperature during autumn when also the maximum lightning activity over the sea is depicted. We suggest that higher sea surface temperature further destabilises the lower tropospheric layers, enhancing thus convection and therefore lightning.

  8. Analyzing the Effects of Climate Change on Sea Surface Temperature in Monitoring Coral Reef Health in the Florida Keys Using Sea Surface Temperature Data

    NASA Technical Reports Server (NTRS)

    Jones, Jason; Burbank, Renane; Billiot, Amanda; Schultz, Logan

    2011-01-01

    This presentation discusses use of 4 kilometer satellite-based sea surface temperature (SST) data to monitor and assess coral reef areas of the Florida Keys. There are growing concerns about the impacts of climate change on coral reef systems throughout the world. Satellite remote sensing technology is being used for monitoring coral reef areas with the goal of understanding the climatic and oceanic changes that can lead to coral bleaching events. Elevated SST is a well-documented cause of coral bleaching events. Some coral monitoring studies have used 50 km data from the Advanced Very High Resolution Radiometer (AVHRR) to study the relationships of sea surface temperature anomalies to bleaching events. In partnership with NOAA's Office of National Marine Sanctuaries and the University of South Florida's Institute for Marine Remote Sensing, this project utilized higher resolution SST data from the Terra's Moderate Resolution Imaging Spectroradiometer (MODIS) and AVHRR. SST data for 2000-2010 was employed to compute sea surface temperature anomalies within the study area. The 4 km SST anomaly products enabled visualization of SST levels for known coral bleaching events from 2000-2010.

  9. Pliocene pre-glacial North Atlantic: A coupled sea surface-deep ocean circulation climate response

    SciTech Connect

    Ishman, S.E.; Dowsett, H.J. . National Center)

    1992-01-01

    A latitudinal transect of North Atlantic Deep Sea Drilling Project Holes from the equatorial region to 56 N in the 2,300- to 3,000-meter depth range was designed for a high-resolution study of coupled sea surface and deep ocean response to climate change. Precise age control was provided using magnetostratigraphic and biostratigraphic data from the cores to identify the 4.0 to 2.2 Ma interval, a period of warm-to-cool climatic transitions in the North Atlantic. The objective is to evaluate incremental (10 kyr) changes in sea surface temperatures (SST) and deep North Atlantic circulation patterns between 4.0 and 2.2 Ma to develop a coupled sea surface-deep ocean circulation response model. Sea surface temperature (SST) estimates are based on planktic foraminifer-based factor-analytic transfer functions. Oxygen isotopic data from paired samples provide tests of the estimated temperature gradients between localities. Benthic foraminifer assemblage data and [partial derivative]O-18 and [partial derivative]C-13 Isotopic data are used to quantitatively determine changes in deep North Atlantic circulation. These data are used to determine changes in source area (North Atlantic Deep Water (NADW) or Antarctic Bottom Water) and (or) in the components of NADW that were present (Upper or Lower NADW). These paired paleoceanographic sea surface and deep circulation interpretations over a 1.8 my interval form the basis for a coupled sea surface-deep circulation response model for the Pliocene North Atlantic Ocean.

  10. Analysis of sea level and sea surface temperature changes in the Black Sea

    NASA Astrophysics Data System (ADS)

    Betul Avsar, Nevin; Jin, Shuanggen; Kutoglu, Hakan; Erol, Bihter

    2016-07-01

    The Black Sea is a nearly closed sea with limited interaction with the Mediterranean Sea through the Turkish Straits. Measurement of sea level change will provide constraints on the water mass balance and thermal expansion of seawaters in response to climate change. In this paper, sea level changes in the Black Sea are investigated between January 1993 and December 2014 using multi-mission satellite altimetry data and sea surface temperature (SST) data. Here, the daily Maps of Sea Level Anomaly (MSLA) gridded with a 1/8°x1/8° spatial resolution from AVISO and the NOAA 1/4° daily Optimum Interpolation Sea Surface Temperature (OISST) Anomaly data set are used. The annual cycles of sea level and sea surface temperature changes reach the maximum values in November and January, respectively. The trend is 3.16±0.77 mm/yr for sea level change and -0.06±0.01°C/yr for sea surface temperature during the same 22-year period. The observed sea level rise is highly correlated with sea surface warming for the same time periods. In addition, the geographical distribution of the rates of the Black Sea level and SST changes between January 1993 and December 2014 are further analyzed, showing a good agreement in the eastern Black Sea. The rates of sea level rise and sea surface warming are larger in the eastern part than in the western part except in the northwestern Black Sea. Finally, the temporal correlation between sea level and SST time series are presented based on the Empirical Orthogonal Function (EOF) analysis.

  11. Temporal variability of remotely sensed suspended sediment and sea surface temperature patterns in Mobile Bay, Alabama

    USGS Publications Warehouse

    Rucker, J.B.; Stumpf, R.P.; Schroeder, W.W.

    1990-01-01

    Distribution patterns of suspended sediments and sea surface temperatures in, Mobile Bay were derived from algorithms using digital data from the visible, near infrared, and infrared channels of the Advanced Very High Resolution Radiometer (AVHRR) on the NOAA-TIROS-N satellite. Closely spaced AVHRR scenes for January 20, 24, and 29, 1982, were compared with available environmental information taken during the same period. A complex interaction between river discharge, winds, and astronomical tides controlled the distribution patterns of suspended sediments. These same variables, coupled with air temperatures, also governed the distribution patterns of sea surface temperatures. ?? 1990 Estuarine Research Federation.

  12. Evaluation of empirical retracking of Cryosat2 sea surface data in the Arctic Ocean

    NASA Astrophysics Data System (ADS)

    Jain, M.; Andersen, O. B.; Stenseng, L.

    2012-04-01

    Waveform retracking of satellite data is used for sea surface height determination. In the Arctic Region, these echo waveforms contain reflections from various cryosphere features such as sea ice, ice sheets, new frozen water etc. Cryosat2 data has Level1b components which record the power waveforms of the echoes as well as Level2 components which provide the sea surface height as developed by the retrackers used by the space agencies. A retracker based on the combination of OCOG (Offset Centre of Gravity) method and Threshold method is used to develop the sea surface height in the Arctic Region. This is to be compared with the Level2 sea surface height components available in the Cryosat2 data. The threshold retracker uses the statistical properties of the echo waveform to compute two difference thresholds (start and stop) for the neighboring power bins. Next, a loop is run to check the power differences throughout the waveform for neighboring bins. If this power difference is greater than the start threshold, the system records the beginning of a subwaveform. Further when the power difference of neighboring bins of this sub-waveform is less than the stop threshold, this is recorded as the end of the subwaveform. As a result the power waveform is divided into various subwaveforms each having one peak. The first subwaveform corresponds to the peak for the leading edge. Next, the OCOG method is used to determine the center of gravity of the first subwaveform. This provides the position of the leading edge and thereby the sea surface height is obtained. It is observed that applying the OCOG method on just the leading edge subwaveform results in improved sea surface determination as compared to its application on the complete waveform. The retracked data is subsequently evaluated for its ability to determine geophysical changes related to bathymetry and compared with existing marine gravity surveys in the Arctic Ocean. This presentation will also give an outline of

  13. In situ validation of sea surface temperatures from the GCOM-W1 AMSR2 RSS calibrated brightness temperatures

    NASA Astrophysics Data System (ADS)

    Gentemann, Chelle L.; Hilburn, Kyle A.

    2015-05-01

    Remote Sensing Systems AMSR2 v7.2 data from 25 July 2012 to 9 October 2014 are collocated with in situ sea surface temperature (SST) data. The RSS SST algorithm uses AMSR2 brightness temperatures calibrated using a methodology developed at RSS rather than using the standard JAXA AMSR2 product, which includes the JAXA calibration. The new RFI exclusion methodology used for the AMSR2 v7.2 data is described. Buoy data are quality controlled using an internal quality indicator. Daytime collocations with wind speeds of less than 6 m s-1 are excluded to avoid diurnal contamination of the results. A mean bias (AMSR2 minus in situ) of -0.04 K and standard deviation 0.55 K with 109,350 collocations is found. The geographical distribution of biases is investigated, with a small increase in biases found at higher latitudes. At lower SST the uncertainty increases and the bias. The dependencies of the bias and uncertainties on other geophysical variables are shown to be negligible. The time series of the bias and uncertainty show little variability, but a small seasonal dependence is determined to be related to a seasonal shift in wind speeds. Overall, the AMSR2 SSTs are of comparable quality to the AMSR-E SSTs and continue the climate microwave SST record that started in 1997.

  14. Global Sea-Surface Temperatures Derived from Satellites: Assessing Data Quality and the Quest for Climate Data Records.

    NASA Astrophysics Data System (ADS)

    Minnett, P. J.; Cornillon, P. C.

    2011-12-01

    The derivation of sea-surface temperatures (SST) from space-borne measurements from both infrared and microwave radiometers is now a relatively mature subject and the global and regional SST fields have many applications in operational weather and ocean forecasting, and in research into the processes of the climate system. Successful application of the SST fields depends on how well the uncertainties are known and represented. As additional processing steps are taken to generate more highly-derived representations of the satellite measurements, moving from radiances in swath coordinates to gap-filled SSTs on a regular geographic grid, additional sources of uncertainties contribute to the overall error budget of each SST value. Since some of the major sources of uncertainties in satellite-derived SSTs arise from imperfect identification of meteorological signatures (clouds and aerosols in the infrared, and rain in the microwave) and imperfect corrections for water vapor and other atmospheric effects, statistical representation of uncertainties can be derived by comparison of individual SSTs derived from satellites with independent measurements, usually taken from surface measurements from ships and buoys, as these capture the atmospheric sources of uncertainty. Such comparisons are usually made with swath data from satellites, and conventionally, all errors have been attributed to satellite measurements. Research in recent years has led to a recognition of the complexity of some of the sources of uncertainties, and moved towards a more appropriate representation of the strengths and weaknesses in the remotely-sensed SSTs. This presentation will give a review of the sources of uncertainties in the satellite-derived SST fields and of efforts to establish Climate Data Records of SST.

  15. Cool, cold or colder? Spatial segregation of prions and blue petrels is explained by differences in preferred sea surface temperatures.

    PubMed

    Quillfeldt, Petra; Cherel, Yves; Delord, Karine; Weimerkirch, Henri

    2015-04-01

    The Southern Ocean provides one of the largest environmental gradients on Earth that lacks geographical barriers, and small but highly mobile petrels living there may offer fine models of evolution of diversity along environmental gradients. Using geolocation devices, we investigated the winter distribution of closely related petrel species breeding sympatrically in the southern Indian Ocean, and applied ecological niche models to compare environmental conditions in the habitat used. We show that thin-billed prions (Pachyptila belcheri), Antarctic prions (Pachyptila desolata) and blue petrels (Halobaena caerulea) from the Kerguelen archipelago in the southern Indian Ocean segregate latitudinally, sea surface temperature being the most important variable separating the distribution of the species. Antarctic prions spent the winter north of the Polar Front in temperate waters, whereas blue petrels were found south of the Polar Front in Antarctic waters. Thin-billed prions preferred intermediate latitudes and temperatures. Stable isotope values of feathers reflected this near complete niche separation across an ecological gradient that spans large scales, and suggest evolutionary isolation by environment. In pelagic seabirds that exploit large areas of ocean, spatial niche partitioning may not only facilitate coexistence among ecologically similar species, but may also have driven their evolution in the absence of geographical barriers. PMID:25878044

  16. Cool, cold or colder? Spatial segregation of prions and blue petrels is explained by differences in preferred sea surface temperatures

    PubMed Central

    Quillfeldt, Petra; Cherel, Yves; Delord, Karine; Weimerkirch, Henri

    2015-01-01

    The Southern Ocean provides one of the largest environmental gradients on Earth that lacks geographical barriers, and small but highly mobile petrels living there may offer fine models of evolution of diversity along environmental gradients. Using geolocation devices, we investigated the winter distribution of closely related petrel species breeding sympatrically in the southern Indian Ocean, and applied ecological niche models to compare environmental conditions in the habitat used. We show that thin-billed prions (Pachyptila belcheri), Antarctic prions (Pachyptila desolata) and blue petrels (Halobaena caerulea) from the Kerguelen archipelago in the southern Indian Ocean segregate latitudinally, sea surface temperature being the most important variable separating the distribution of the species. Antarctic prions spent the winter north of the Polar Front in temperate waters, whereas blue petrels were found south of the Polar Front in Antarctic waters. Thin-billed prions preferred intermediate latitudes and temperatures. Stable isotope values of feathers reflected this near complete niche separation across an ecological gradient that spans large scales, and suggest evolutionary isolation by environment. In pelagic seabirds that exploit large areas of ocean, spatial niche partitioning may not only facilitate coexistence among ecologically similar species, but may also have driven their evolution in the absence of geographical barriers. PMID:25878044

  17. SPT-3G: a next-generation cosmic microwave background polarization experiment on the South Pole telescope

    NASA Astrophysics Data System (ADS)

    Benson, B. A.; Ade, P. A. R.; Ahmed, Z.; Allen, S. W.; Arnold, K.; Austermann, J. E.; Bender, A. N.; Bleem, L. E.; Carlstrom, J. E.; Chang, C. L.; Cho, H. M.; Cliche, J. F.; Crawford, T. M.; Cukierman, A.; de Haan, T.; Dobbs, M. A.; Dutcher, D.; Everett, W.; Gilbert, A.; Halverson, N. W.; Hanson, D.; Harrington, N. L.; Hattori, K.; Henning, J. W.; Hilton, G. C.; Holder, G. P.; Holzapfel, W. L.; Irwin, K. D.; Keisler, R.; Knox, L.; Kubik, D.; Kuo, C. L.; Lee, A. T.; Leitch, E. M.; Li, D.; McDonald, M.; Meyer, S. S.; Montgomery, J.; Myers, M.; Natoli, T.; Nguyen, H.; Novosad, V.; Padin, S.; Pan, Z.; Pearson, J.; Reichardt, C.; Ruhl, J. E.; Saliwanchik, B. R.; Simard, G.; Smecher, G.; Sayre, J. T.; Shirokoff, E.; Stark, A. A.; Story, K.; Suzuki, A.; Thompson, K. L.; Tucker, C.; Vanderlinde, K.; Vieira, J. D.; Vikhlinin, A.; Wang, G.; Yefremenko, V.; Yoon, K. W.

    2014-07-01

    We describe the design of a new polarization sensitive receiver, spt-3g, for the 10-meter South Pole Telescope (spt). The spt-3g receiver will deliver a factor of ~20 improvement in mapping speed over the current receiver, spt-pol. The sensitivity of the spt-3g receiver will enable the advance from statistical detection of B-mode polarization anisotropy power to high signal-to-noise measurements of the individual modes, i.e., maps. This will lead to precise (~0.06 eV) constraints on the sum of neutrino masses with the potential to directly address the neutrino mass hierarchy. It will allow a separation of the lensing and inflationary B-mode power spectra, improving constraints on the amplitude and shape of the primordial signal, either through spt-3g data alone or in combination with bicep2/keck, which is observing the same area of sky. The measurement of small-scale temperature anisotropy will provide new constraints on the epoch of reionization. Additional science from the spt-3g survey will be significantly enhanced by the synergy with the ongoing optical Dark Energy Survey (des), including: a 1% constraint on the bias of optical tracers of large-scale structure, a measurement of the differential Doppler signal from pairs of galaxy clusters that will test General Relativity on ~200Mpc scales, and improved cosmological constraints from the abundance of clusters of galaxies

  18. An Ultra-Wideband, Microwave Radar for Measuring Snow Thickness on Sea Ice and Mapping Near-Surface Internal Layers in Polar Firn

    NASA Technical Reports Server (NTRS)

    Panzer, Ben; Gomez-Garcia, Daniel; Leuschen, Carl; Paden, John; Rodriguez-Morales, Fernando; Patel, Azsa; Markus, Thorsten; Holt, Benjamin; Gogineni, Prasad

    2013-01-01

    Sea ice is generally covered with snow, which can vary in thickness from a few centimeters to >1 m. Snow cover acts as a thermal insulator modulating the heat exchange between the ocean and the atmosphere, and it impacts sea-ice growth rates and overall thickness, a key indicator of climate change in polar regions. Snow depth is required to estimate sea-ice thickness using freeboard measurements made with satellite altimeters. The snow cover also acts as a mechanical load that depresses ice freeboard (snow and ice above sea level). Freeboard depression can result in flooding of the snow/ice interface and the formation of a thick slush layer, particularly in the Antarctic sea-ice cover. The Center for Remote Sensing of Ice Sheets (CReSIS) has developed an ultra-wideband, microwave radar capable of operation on long-endurance aircraft to characterize the thickness of snow over sea ice. The low-power, 100mW signal is swept from 2 to 8GHz allowing the air/snow and snow/ ice interfaces to be mapped with 5 c range resolution in snow; this is an improvement over the original system that worked from 2 to 6.5 GHz. From 2009 to 2012, CReSIS successfully operated the radar on the NASA P-3B and DC-8 aircraft to collect data on snow-covered sea ice in the Arctic and Antarctic for NASA Operation IceBridge. The radar was found capable of snow depth retrievals ranging from 10cm to >1 m. We also demonstrated that this radar can be used to map near-surface internal layers in polar firn with fine range resolution. Here we describe the instrument design, characteristics and performance of the radar.

  19. Simultaneous even- and third-order distortion suppression in a microwave photonic link based on orthogonal polarization modulation, balanced detection, and optical sideband filtering.

    PubMed

    Han, Xiuyou; Chen, Xiang; Yao, Jianping

    2016-06-27

    A microwave photonic link (MPL) with simultaneous suppression of the even-order and third-order distortions using a polarization modulator (PolM), an optical bandpass filter (OBPF), and a balanced photodetector (BPD) is proposed and experimentally demonstrated. The even-order distortions are suppressed by utilizing orthogonal polarization modulation based on the PolM and balanced differential detection based on the BPD. The third-order distortions (IMD3) are suppressed by optimizing the spectral response of the OBPF with an optimal power ratio between the optical carrier and the sidebands of the phase-modulated signals from the PolM. Since the suppression of the IMD3 is achieved when the MPL is optimized for even-order distortion suppression, the proposed MPL can operate with simultaneous suppression of the even-order and third-order distortions. The proposed MPL is analyzed theoretically and is verified by an experiment. For a two-tone RF signal of f1 = 10 GHz and f2 = 19.95 GHz, the spurious-free dynamic range (SFDR2) is enhanced by 23.4 dB for the second harmonic (2f1), and 29.1 and 27.6 dB for the second intermodulation (f2-f1 and f1 + f2), as compared with a conventional MPL. For a two-tone RF signal of f1 = 9.95 GHz and f2 = 10 GHz, the SFDR3 is increased by 13.1 dB as compared with a conventional MPL. PMID:27410633

  20. Interaction Between Surface Heat Budgets, Sea Surface Temperature and Deep Convection in the Tropical Western Pacific

    NASA Technical Reports Server (NTRS)

    Chou, Shu-Hsien; Chou, Ming-Dah; Lin, Po-Hsiung; Starr, David OC. (Technical Monitor)

    2002-01-01

    The surface heat budgets, sea surface temperature (SST), clouds and winds in the tropical western Pacific are analyzed and compared for the periods April-June 1998 and 1999. The spring of 1998 is in the later phase of a strong El Nino, whereas the spring of 1999 is in a period of a La Nina. The surface shortwave (SW) and longwave (LW) radiative fluxes are retrieved from Japanese Geostationary Meteorological Satellite radiance measurements, while the surface turbulent fluxes (latent and sensible heat) are derived from SSM/I-Inferred surface air humidity and winds. The SST and sea-air temperature differences are taken from NCEP/NCAR reanalysis. Deep convection is inferred from the outgoing longwave radiation of NOAA's polar-orbiting satellites. The longitudinal shift in maximum SST, deep convection and winds during El Nino and La Nina have a large impact on the spatial distribution of surface heating. Changes in clouds between these two periods have a large impact on the monthly-mean radiative heating, exceeding 60 W m(exp -2) over large oceanic regions. Similarly, the differences in wind speeds and SST have a large impact on the latent cooling, exceeding 40 W m(exp -2) over large oceanic areas. However, the maximum impacts on radiative and latent heat fluxes occur in different regions. The regions of maximum impact on radiative fluxes coincide with the regions of maximum change in clouds, whereas regions of maximum impact on turbulent heat fluxes coincide with the regions of maximum change in trade winds. The time-evolution of SST in relation to that of surface heat fluxes and winds are investigated and compared between the two El Nino and La Nina periods. In regions where wind speeds (or wind stresses) are large, the change in SST agrees well with the change in the net surface heating, indicating a deep ocean mixed layer associated with strong trade winds. On the other hand, in regions where radiative fluxes are large, the change in SST does not agree well with the

  1. Density Banding in Coral Skeletons: A Biotic Response to Sea Surface Temperature?

    NASA Astrophysics Data System (ADS)

    Hill, C. A.; Oehlert, A. M.; Piggot, A. M.; Yau, P. M.; Fouke, B. W.

    2008-12-01

    Density bands in the CaCO3 (aragonite) skeleton of scleractinian corals are commonly used as chronometers, where crystalline couplets of high and low density bands represent the span of one year. This provides a sensitive reconstructive tool for paleothermometry, paleoclimatology and paleoecology. However, the detailed mechanisms controlling aragonite nucleation and crystallization events and the rate of skeletal growth remain uncertain. The organic matrix, composed of macromolecules secreted by the calicoblastic ectoderm, is closely associated with skeletal precipitation and is itself incorporated into the skeleton. We postulate that density banding is primarily controlled by changes in the rate of aragonite crystal precipitation mediated by the coral holobiont response to changes in sea surface temperature (SST). To test this hypothesis, data were collected from coral skeleton-tissue biopsies (2.5 cm in diameter) extracted from four species of Montastraea growing on the fringing reef tract of Curacao, Netherlands Antilles (annual mean variation in SST is 29° C in mid-September to 26° C in late February). Samples were collected in the following three contextual modes: 1) at two sites (Water Plant and Playa Kalki) along a lateral 25 km spatial transect; 2) across a vertical bathymetric gradient from 5 to 15 m water depth at each site; and 3) at strategic time periods spanning the 3° C annual variations in SST. Preliminary results indicate that skeletal density banding is also expressed in the organic matrix, permitting biochemical characterization and correlation of the organic matrix banding to the skeletal banding. In addition, both surficial and ectodermal mucins were characterized in terms of total protein content, abundance and location of their anionic, cationic, and neutral macromolecular constituents. Furthermore, the ratio of mucocytes in the oral ectoderm to gastrodermal symbiotic zooxanthellae has permitted estimates of seasonal carbon allocation by

  2. High time resolution observations of the polar stratosphere and mesosphere using a ground-based 230-250 GHz microwave radiometer

    NASA Astrophysics Data System (ADS)

    Newnham, D. A.; Espy, P. J.; Clilverd, M. A.; Maxfield, D. J.; Hartogh, P.; Holmén, K.; Blindheim, S.; Horne, R. B.

    2012-04-01

    Microwave radiometry is used to measure thermal emission by the Doppler- and pressure-broadened molecular rotational lines of atmospheric gases, from which vertical abundance profiles can be determined. Since solar radiation is not required for the measurement, the technique has the advantage that continuous observations are possible including throughout the polar winter. We describe the development of a passive microwave radiometer [Espy, P. J., P. Hartogh, and K. Holmen (2006), Proc. SPIE, 6362, 63620P, doi:10.1117/12.688953] for ground-based remote sensing of the polar middle atmosphere. The instrument measures nitric oxide (NO), ozone (O3), and carbon monoxide (CO) vertical profiles over the altitude range 35-90 km with time resolution as high as 15 minutes, allowing the diurnal variability of trace chemical species to be investigated. Heterodyne detection of atmospheric emission at 230 GHz and 250 GHz (wavelength ~1.25 mm) with a receiver noise temperature of 300 K is achieved using a superconductor-insulator-superconductor (SIS) mixer cooled to 4 K. The down-converted signals at 1.35 GHz and 2.10 GHz are analysed using both a moderate-resolution (28 kHz, 220 MHz bandwidth) and a high-resolution (14 kHz, 40 MHz bandwidth) chirp-transform spectrometer (CTS). The instrument was operated semi-autonomously at Troll station (72° 01'S 02° 32'E, 1270 m above sea level), Antarctica during 2008-10 and at the Arctic LIDAR Observatory for Middle Atmosphere Research (ALOMAR, 69° 16'N, 16° 00'E, 380 m above sea level), northern Norway during 2011-12. NO volume mixing ratio (VMR) profiles have been inverted from calibrated brightness temperature spectra of the NO line centred at 250.796 GHz, observed above Troll station, using the Microwave Observation Line Estimation and Retrieval (MOLIERE) version 5 code. A priori pressure, temperature, ozone, water vapour, and NO profiles above 30 km were calculated using the Sodankylä Ion and Neutral Chemistry (SIC, version 6

  3. Analysis of near-shore sea surface temperatures in the Northern Pacific

    EPA Science Inventory

    Recent studies report a warming trend in Pacific Ocean temperatures over the last 50 years. However, much less is known about temperature change in the near-coastal environment, which is particularly sensitive to climatic change. In near-shore regions in situ sea surface temper...

  4. Reconstructing Variations of Global Sea-Surface Temperature during the Last Interglaciation

    NASA Astrophysics Data System (ADS)

    Hoffman, J. S.; Clark, P. U.; He, F.; Parnell, A. C.

    2015-12-01

    The last interglaciation (LIG; ~130-116 ka) was the most recent period in Earth history with higher-than-present global sea level (≥6 m) under similar-to-preindustrial concentrations of atmospheric CO2, suggesting additional feedbacks related to albedo, insolation, and ocean circulation in generating the apparent climatic differences between the LIG and present Holocene. However, our understanding of how much warmer the LIG sea surface was relative to the present interglaciation remains uncertain, with current estimates suggesting from 0°C to 2°C warmer than late-20thcentury average global temperatures. Moreover, the timing, spatial expression, and amplitude of regional and global sea surface temperature variability related to other climate forcing during the LIG are poorly constrained, largely due to uncertainties in age control and proxy temperature reconstructions. An accurate characterization of global and regional temperature change during the LIG can serve as a benchmark for paleoclimate modeling intercomparison projects and help improve understanding of sea-level sensitivity to temperature change. We will present a global compilation (~100 published records) of sea surface temperature (SST) and other climate reconstructions spanning the LIG. Using a Monte Carlo-enabled cross-correlation maximization algorithm to climatostratigraphically align proxy records and then account for both the resulting chronologic and proxy calibration uncertainties with Bayesian statistical inference, our results quantify the spatial timing, amplitude, and uncertainty in estimates of global and regional sea surface temperature change during the LIG and its relation to potential forcings.

  5. Tightly linked zonal and meridional sea surface temperature gradients over the past five million years

    NASA Astrophysics Data System (ADS)

    Fedorov, Alexey V.; Burls, Natalie J.; Lawrence, Kira T.; Peterson, Laura C.

    2015-12-01

    The climate of the tropics and surrounding regions is defined by pronounced zonal (east-west) and meridional (equator to mid-latitudes) gradients in sea surface temperature. These gradients control zonal and meridional atmospheric circulations, and thus the Earth’s climate. Global cooling over the past five million years, since the early Pliocene epoch, was accompanied by the gradual strengthening of these temperature gradients. Here we use records from the Atlantic and Pacific oceans, including a new alkenone palaeotemperature record from the South Pacific, to reconstruct changes in zonal and meridional sea surface temperature gradients since the Pliocene, and assess their connection using a comprehensive climate model. We find that the reconstructed zonal and meridional temperature gradients vary coherently over this time frame, showing a one-to-one relationship between their changes. In our model simulations, we systematically reduce the meridional sea surface temperature gradient by modifying the latitudinal distribution of cloud albedo or atmospheric CO2 concentration. The simulated zonal temperature gradient in the equatorial Pacific adjusts proportionally. These experiments and idealized modelling indicate that the meridional temperature gradient controls upper-ocean stratification in the tropics, which in turn controls the zonal gradient along the equator, as well as heat export from the tropical oceans. We conclude that this tight linkage between the two sea surface temperature gradients posits a fundamental constraint on both past and future climates.

  6. 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.

  7. Sea surface height and steric height increases in the Southern Hemisphere

    NASA Astrophysics Data System (ADS)

    Tretkoff, Ernie

    2011-06-01

    Sea surface height has increased by 3 millimeters per year, globally averaged, since 1993. Some fraction of sea surface height change is due to added water from melting glaciers, for instance, and some is due to increasing heat and salinity changes (steric effects). Focusing on the Southern Hemisphere, Sutton and Roemmich analyzed temperature and salinity data from the Argo float array in relation to earlier data from the World Ocean Circulation Experiment (WOCE) to estimate the steric changes. These were compared with the total sea surface height changes over the same period seen in satellite altimetric data. They found that on decadal time scales, about half of the rise in sea surface height in the Southern Ocean is due to steric effects, with the proportion increasing southward. The accompanying increase in ocean heat content south of 30°S can account for most of the global heat content change during this period. (Geophysical Research Letters, doi:10.1029/ 2011GL046802, 2011)

  8. The impact of sea surface currents in wave power potential modeling

    NASA Astrophysics Data System (ADS)

    Zodiatis, George; Galanis, George; Kallos, George; Nikolaidis, Andreas; Kalogeri, Christina; Liakatas, Aristotelis; Stylianou, Stavros

    2015-11-01

    The impact of sea surface currents to the estimation and modeling of wave energy potential over an area of increased economic interest, the Eastern Mediterranean Sea, is investigated in this work. High-resolution atmospheric, wave, and circulation models, the latter downscaled from the regional Mediterranean Forecasting System (MFS) of the Copernicus marine service (former MyOcean regional MFS system), are utilized towards this goal. The modeled data are analyzed by means of a variety of statistical tools measuring the potential changes not only in the main wave characteristics, but also in the general distribution of the wave energy and the wave parameters that mainly affect it, when using sea surface currents as a forcing to the wave models. The obtained results prove that the impact of the sea surface currents is quite significant in wave energy-related modeling, as well as temporally and spatially dependent. These facts are revealing the necessity of the utilization of the sea surface currents characteristics in renewable energy studies in conjunction with their meteo-ocean forecasting counterparts.

  9. Remotely-sensed sea surface temperatuares (SST) of Northeaster Pacific Coastal Zones

    EPA Science Inventory

    Sea surface temperature (SST) is an important indicator of long-term trends and geographical temperature patterns; however there have been relatively few long-term records of SST in near-coastal habitats. In situ SST measurements are irregular in both space and time. Therefore, w...

  10. Statistical Analysis of Spatio-temporal Variations of Sea Surface Height Observed by Topex Altimeter

    NASA Technical Reports Server (NTRS)

    Fabrikant, A.; Glazman, R. E.; Greysukh, A.

    1994-01-01

    Using non-gridded Topex altimeter data, high resolution 2-d power spectra and spatio-temporal autocorrelation functions of sea surface height (SSH) variations are estimated and employed for studying anisotropic SSH fields varying in a broad range of scales.

  11. Evaporation and Solar Irradiance as Regulators of Sea Surface Temparature in Annual and Interrannual Changes

    NASA Technical Reports Server (NTRS)

    Liu, W. Timothy

    1994-01-01

    After numerical studies showed that global climate is sensitive to small changes in sea surface temperature (Ts), considerabel effort has been devoted to examine the role of surface fluxes in changing upper ocean heat balance and Ts, particularly in the tropical Pacific where interannual signals, such as El Nino Southern Oscillation (ENSO), have major economic and ecological impacts.

  12. Ecoregional analysis of nearshore sea-surface temperature in the North Pacific

    EPA Science Inventory

    Aim Sea surface temperature (SST) has been a parameter widely-identified to be useful to the investigation of marine species distribution, migration, and invasion, especially as SSTs are predicted to be affected by climate change. Here we use a remotely-sensed dataset to focus on...

  13. Sea surface temperature and torrential rains in the Valencia region: modelling the role of recharge areas

    NASA Astrophysics Data System (ADS)

    Pastor, Francisco J.

    2016-04-01

    Heavy rain events are frequently recorded in the Western Mediterranean causing economic and human losses. A main factor in the development of torrential rains is ocean-atmosphere exchange of heat and moisture that can destabilize air masses travelling over the sea. The study of air mass trajectories previous to the rain event permits the identification of sea areas that could probably contribute to the development or intensification of rainfall. From a Mediterranean sea surface temperature climatology, its spatio-temporal distribution patterns have been studied showing two main distribution modes in winter and summer and transitional regimes in spring and autumn. Hence, three heavy precipitation events, for such winter and summer sea temperature regimes and for fall transition, affecting the Valencia region have been selected to study the effect of sea surface temperature in torrential rains. Simulations with perturbed sea surface temperature in different areas along the air mass path were run to compare results with unperturbed simulation. The variation of sea surface temperature in certain areas caused significant changes in model accumulated values and its spatial distribution. Therefore, the existence of areas that at a greater extent favour air-sea interaction leading to the development of torrential rainfall in the Valencia region is shown. This methodology could be extended to other Mediterranean regions to look for such potential recharge areas. The identification of sea areas that contribute to the development or intensification of heavy rain events in the Mediterranean countries could be a useful prognosis and/or monitoring tool.

  14. Polarity-enhanced gas-sensing performance of Au-loaded ZnO nanospindles synthesized via precipitation and microwave irradiation

    NASA Astrophysics Data System (ADS)

    Li, Yan; Lv, Tan; Zhao, Fang-Xian; Lian, Xiao-Xue; Zou, Yun-Ling; Wang, Qiong

    2016-05-01

    Loading noble metal and exploring suitable morphology to achieve excellent gas-sensing performance is very crucial for the fabrication of gas sensors. We have successfully synthesized Au-loaded ZnO (Au/ZnO) nanospindles (NSs) through a really facile procedure involving a precipitation and subsequent microwave irradiation. The as-prepared products have been characterized by X-ray diffraction (XRD), scanning electron microscope (SEM). The formation and gas-sensing mechanism of Au/ZnO NSs were discussed. The SEM micrographs revealed an interesting morphological evolution of the Au/ZnO NSs with Au-loading content ranging from 0 at. % to 7 at. %. The nanostructures were employed for gas-sensing measurement toward various gases. It indicated that the Au/ZnO NSs based sensor showed a highly enhanced response (226.81) to 400 ppm acetone gas at a relatively low working temperature (270°C), and exhibited a fast response (1 s) and recovery speed (10 s). The highly enhanced acetone gas sensitivity of Au/ZnO NSs based sensor could be attributed to its enhanced polarity owing to the peculiar morphology, Schottcky barriers, as well as catalytic effect of Au NPs. [Figure not available: see fulltext.

  15. An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1991

    NASA Technical Reports Server (NTRS)

    Halpern, D.; Knauss, W.; Brown, O.; Wentz, F.

    1993-01-01

    The following monthly mean global distributions for 1991 are presented with a common color scale and geographical map: 10-m height wind speed estimated from the Special Sensor Microwave Imager (SSMI) on a United States Air Force Defense Meteorological Satellite Program (DMSP) spacecraft; sea surface temperature estimated from the advanced very high resolution radiometer (AVHRR/2) on a U.S. National Oceanic and Atmospheric Administration (NOAA) spacecraft; Cartesian components of free-drifting buoys which are tracked by the ARGOS navigation system on NOAA satellites; and Cartesian components of the 10-m height wind vector computed by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of monthly mean value, sampling distribution, and standard deviation value are displayed. Annual mean distributions are displayed.

  16. An atlas of monthly mean distributions of SSMI surface wind speed, ARGOS buoy drift, AVHRR/2 sea surface temperature, and ECMWF surface wind components during 1990

    NASA Technical Reports Server (NTRS)

    Halpern, D.; Knauss, W.; Brown, O.; Wentz, F.

    1993-01-01

    The following monthly mean global distributions for 1990 are proposed with a common color scale and geographical map: 10-m height wind speed estimated from the Special Sensor Microwave Imager (SSMI) on a United States (US) Air Force Defense Meteorological Satellite Program (DMSP) spacecraft; sea surface temperature estimated from the advanced very high resolution radiometer (AVHRR/2) on a U.S. National Oceanic and Atmospheric Administration (NOAA) spacecraft; Cartesian components of free drifting buoys which are tracked by the ARGOS navigation system on NOAA satellites; and Cartesian components on the 10-m height wind vector computed by the European Center for Medium-Range Weather Forecasting (ECMWF). Charts of monthly mean value, sampling distribution, and standard deviation values are displayed. Annual mean distributions are displayed.

  17. The Arctic sea surface microlayer: a source of atmospheric ice nuclei?

    NASA Astrophysics Data System (ADS)

    Murray, Benjamin; Wilson, Theodore; Whale, Thomas

    2014-05-01

    The Arctic climate is changing faster than almost anywhere else on the planet and future warming is predicted to exceed global mean changes. Central to this climate sensitivity are changes in cloud cover, water content, ice content and particle size. Low level stratus clouds which are ubiquitous in the Arctic region, frequently exist in a thermodynamically unstable mixed phase state; hence they are sensitive to ice nuclei. A key limitation in our ability to quantitatively understand and model these clouds is the identity, concentration and efficiency of ice nucleating particles in the Arctic. One potential source of ice nuclei in this region is from the sea surface microlayer which is enriched in organic material and thought to become concentrated in aerosol particles produced through bubble bursting. During the summer of 2013 we sampled sea surface microlayer using a remote control rotating drum sampler during the Aerosol-Cloud Coupling and Climate Interaction in the Arctic (ACCACIA) cruise. The samples were brought back on board the RSS James Clark Ross where we used a droplet freezing instrument to test for ice nuclei in these samples. We found that the concentration of ice nuclei in the sea surface microlayer was massively enhanced over the bulk sea water and were able to freeze droplets up to -7 C. We found that the sea surface microlayer was active in 15 sites between 70 N and 83 N. Tests showed that these ice nuclei were sensitive to heat which is consistent with a biogenic origin of these nuclei. Using filters we were also able to show that the bulk of the ice nucleating particles were on the order of 100s nm. These results show that there is a reservoir of ice nucleating particles in the sea surface microlayer which have the potential to influence Arctic clouds.

  18. Aliased tidal errors in TOPEX/POSEIDON sea surface height data

    NASA Technical Reports Server (NTRS)

    Schlax, Michael G.; Chelton, Dudley B.

    1994-01-01

    Alias periods and wavelengths for the M(sub 2, S(sub 2), N(sub 2), K(sub 1), O(sub 1), and P(sub 1) tidal constituents are calculated for TOPEX/POSEIDON. Alias wavelenghts calculated in previous studies are shown to be in error, and a correct method is presented. With the exception of the K(sub 1) constituent, all of these tidal aliases for TOPEX/POSEIDON have periods shorter than 90 days and are likely to be confounded with long-period sea surface height signals associated with real ocean processes. In particular, the correspondence between the periods and wavelengths of the M(sub 2) alias and annual baroclinic Rossby waves that plagued Geosat sea surface height data is avoided. The potential for aliasing residual tidal errors in smoothed estimates of sea surface height is calculated for the six tidal constituents. The potential for aliasing the lunar tidal constituents M(sub 2), N(sub 2) and O(sub 1) fluctuates with latitude and is different for estimates made at the crossovers of ascending and descending ground tracks than for estimates at points midway between crossovers. The potential for aliasing the solar tidal constituents S(sub 2), K(sub 1) and P(sub 1) varies smoothly with latitude. S(sub 2) is strongly aliased for latitudes within 50 degress of the equator, while K(sub 1) and P(sub 1) are only weakly aliased in that range. A weighted least squares method for estimating and removing residual tidal errors from TOPEX/POSEIDON sea surface height data is presented. A clear understanding of the nature of aliased tidal error in TOPEX/POSEIDON data aids the unambiguous identification of real propagating sea surface height signals. Unequivocal evidence of annual period, westward propagating waves in the North Atlantic is presented.

  19. Using hyperspectral image enhancement method for small size object detection on the sea surface

    NASA Astrophysics Data System (ADS)

    Yan, Lu; Noro, Naoki; Takara, Yohei; Ando, Fuminori; Yamaguchi, Masahiro

    2015-10-01

    Small size object detection in vast ocean plays an important role in rescues after accident or disaster. One of the promising approach is a hyperspectral imaging system (HIS). However, due to the limitation of HIS sensor's resolution, interested target might occupy only several pixels or less in the image, it's difficult to detect small object, moreover the sun glint of the sea surface make it even more difficult. In this paper, we propose an image analysis technique suitable for the computer aided detection of small objects on the sea surface, especially humans. We firstly separate objects from background by adapting a previously proposed image enhancement method and then apply a linear unmixing method to define the endmember's spectrum. At last, we use spectral angle mapping method to classify presented objects and thus detect small size object. The proposed system provides the following results for supporting the detection of humans and other small objects on the sea surface; an image with spectral color enhancement, alerts of various objects, and the human detection results. This multilayered approach is expected to reduce the oversight, i.e., false negative error. Results of the proposed technique have been compared with existent methods, and our method has successfully enhance the hyperspectral image, and detect small object from the sea surface with high human detection rate, shows the ability to further detection of human in this study). The result are less influenced by the sun glint effects. This study helps recognizing small objects on the sea surface, and it leads to advances in the rescuing system using aircraft equipped HIS technology.

  20. Comparison of TOPEX sea surface heights and tide gauge sea levels

    NASA Technical Reports Server (NTRS)

    Mitchum, Gary T.

    1994-01-01

    TOPEX sea surface height data from the first 300 days of the mission are compared to sea level data from 71 tide gauges. The initial comparison uses sea surface height data processed according to standard procedures as defined in the users handbook. It is found that the median correlations for island and for coastal tide gauges are 0.53 and 0.42, respectively. The analogous root mean square (RMS) differences between the two data sets are 7.9 and 10.4 cm. The comparisons improve significantly when a 60-day harmonic is fit to the differences and removed. This period captures aliased M(sub 2) and S(sub 2) tidal energy that is not removed by the tide model. Making this correction and smoothing the sea surface height data over 25-km along-track segments results in median correlations of 0.58 and 0.46 for the islands and coastal stations, and median RMS differences of 5.8 and 7.7 cm, respectively. Removing once per revolution signals from the sea surface heights results in degraded comparisons with the sea levels. It is also found that a number of stations have poor comparisons due to propagating signals that introduce temporal lags between the altimeter and tide gauge time series. A final comparison is made by eliminating stations where this propagation effect is large, discarding two stations that are suspected to have problems with the sea level data, smoothing over 10-day intervals, and restricting attention to islands gauges. This results in a set of 552 data pairs that have a correlation of 0.66 and a RMS difference of 4.3 cm. The conclusion is that on timescales longer than about 10 days the RMS sea surface height errors are less than or of the order of several centimeters.

  1. Reconstructing past sea surface temperatures: Correcting for diagenesis of bulk marine carbonate

    SciTech Connect

    Schrag, D.P.; DePaolo, D.J. |; Richter, F.M.

    1995-06-01

    A numerical model which describes oxygen isotope exchange during burial and recrystallization of deep-sea carbonate is used to obtain information on how sea surface temperatures have varied in the past by correcting measured {delta}{sup 18}O values of bulk carbonate for diagenetic overprinting. Comparison of bulk carbonate and planktonic foraminiferal {delta}{sup 18}O records from ODP site 677A indicates that the oxygen isotopic composition of bulk carbonate does reflect changes in sea surface temperature and {delta}{sup 18}O. At ODP Site 690, we calculate that diagenetic effects are small, and that both bulk carbonate and planktonic foraminiferal {delta}{sup 18}O records accurately reflect Paleogene warming of high latitude surface oceans, biased from diagenesis by no more than 1{degrees}C. The same is likely to be true for other high latitude sites where sedimentation rates are low. At DSDP sites 516 and 525, the effects of diagenesis are more significant. Measured {delta}{sup 18}O values of Eocene bulk carbonates are more than 2% lower at deeply buried site 516 than at site 525, consistent with the model prediction that the effects of diagenesis should be proportional to sedimentation rate. Model-corrections reconcile the differences in the data between the two sites; the resulting paleotemperature reconstruction indicates a 4{degrees}C cooling of mid-latitude surface oceans since the Eocene. We show that the data are consistent with constant equatorial sea surface temperatures through most of the Cenozoic, with the possible exception of the early Eocene, when slightly higher temperatures are indicated. We suggest that the lower equatorial sea surface temperatures for the Eocene and Oligocene reported in other oxygen isotope studies are artifacts of diagenetic recrystallization, and that it is impossible to reconstruct accurately equatorial sea surface temperatures without explicitly accounting for diagenetic overprinting.

  2. Simulation studies of the influence of sea-surface temperature anomalies on the Sahelian circulation and rainfall

    NASA Technical Reports Server (NTRS)

    Sud, Y. C.; Semazzi, F. H. M.; Mehta, V.

    1988-01-01

    An investigation was conducted to find out if sea surface temperature (SST) - African rainfall relationships could be simulated in a global climate model (GCM). If indeed that were possible, researchers generated useful diagnostics that can enable them to understand the physical mechanisms which lead to rainfall fluctuations over Africa in response to sea surface temperature anomalies over global ocean.

  3. A microwave backscattering model for precipitation

    NASA Astrophysics Data System (ADS)

    Ermis, Seda

    A geophysical microwave backscattering model for space borne and ground-based remote sensing of precipitation is developed and used to analyze backscattering measurements from rain and snow type precipitation. Vector Radiative Transfer (VRT) equations for a multilayered inhomogeneous medium are applied to the precipitation region for calculation of backscattered intensity. Numerical solution of the VRT equation for multiple layers is provided by the matrix doubling m