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United States Naval Research Laboratory

United States Naval Research Laboratory

8 Projects, page 1 of 2
  • Funder: UK Research and Innovation Project Code: NE/H004238/1
    Funder Contribution: 371,897 GBP

    The exchange of heat and moisture between the ocean and atmosphere depends upon turbulent mixing in the lower atmosphere; this depends strongly on the wind speed. At very high wind speeds the sea surface becomes dominated by breaking waves, whitecaps, and sea spray. The water droplets lofted into the lower atmosphere by turbulent air motions will undergo two interactions with the air around them. First, if they are at a different temperature from the air, they will cool or warm until their temperature matches that of the air; secondly, they will start to evaporate, contributing water vapour to the air. Evaporation requires energy, which is obtained initially by a cooling of the droplet, and then a transfer of heat from the air to the droplet. The net result of these processes is a transfer of heat and moisture between ocean and air at some altitude above the surface. The simplified mathematical descriptions of of heat and moisture exchange used within weather forecast and climate models assume that all the heat and moisture exchange takes place at the surface, thus they may provide the wrong values at high wind speeds. The difficulty of making appropriate measurements under severe storm conditions at sea means that there are very few measurements available with which to evaluate whether the spray generated actually has a significant impact or not. Theoretical studies disagree strongly about the importance of the effect. In this study we will instrument autonomous buoys, specifically designed to operate in extreme conditions, to measure the turbulent exchange of heat, moisture, momentum, and sea-spray between the atmosphere and ocean, along measurements of wave state, turbulence in the surface layer of the ocean, the extent of wave breaking, and mean conditions in the surface layers of the ocean and atmosphere. The data obtained will be used to evaluate the air-sea exchange, and determine the contribution of the sea spray to the total exchange of heat and moisture. The measurements will also be used to better define the rate of sea-spray aerosol generation under high winds, and the influence of wave state on the production rate, both of which are poorly defined. Improving understanding of air-sea interaction is particularly important for high wind conditions, because the development and track of severe storms - hurricanes and typhoons - is critically dependent on the heat and moisture input and frictional drag at the surface. This study will ultimately lead to improved prediction of severe tropical storms. The study will be carried out in close collaboration with the University of Miami, Florida, who operate the buoys from which the measurements will be made. The buoys will be deployed in the East/South China Sea in June 2010 and recovered during October 2010.

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  • Funder: UK Research and Innovation Project Code: NE/G000123/1
    Funder Contribution: 47,555 GBP

    In 2006 scientists from the UK's National Oceanography Centre, Southampton (NOCS) installed additional sensors to measure the rate at which the atmosphere and ocean exchange heat, CO2 and momentum. The behaviour of theses exchanges or 'fluxes' is complicated and is affected by many other processes. For example, the CO2 flux may depend on wind speed, air temperature and humidity, sea temperature, sea state, wave breaking, whitecap coverage, CO2 concentration of the water and CO2 concentration in the atmosphere. All these processes need to be measured as well, so that the behaviour of the flux can be understood. The Polarfront was already equipped with a ship borne wave recorder (SBWR) which makes direct measurements of the wave heights, but this system does not measure the direction of the waves. As part of the NOCS project a wave radar system (WAVEX) was also installed to provide wave direction. The WAVEX does not make direct height measurements, but combining its directional data with the height data from the SBWR gives a very detailed description of the sea state - the Polarfront is the only ship in the world to have both systems. NOCS added digital cameras to the ship's bridge to obtain whitecap fraction and sea spikes in the wave radar data will be used to obtained wave breaking statistics. The fluxes are very difficult to measure directly and such measurements are usually only made from research ships, during short cruises of only a few weeks. To date very few measurements have been made of the CO2 flux and none have been made over the open ocean for winds of more than 15 m/s. In contrast, the NOCS systems on the Polarfront have operated continuously since they were installed in September 2006 and measurements in mean wind speeds of more than 25 m/s have already been made. Obtaining high wind speed data is important because the fluxes increase rapidly with increasing wind speed. The Polarfront was chosen for the project since it is dedicated to meteorological observations, unlike any other ship in the world. It also occupies a location where high wind speeds and therefore large fluxes often occur. To understand the interaction between the various forcing process requires a large data set obtained under as wide a range of conditions as possible. Extending the measurement program from 2 years to 3 years (as originally planned) would significantly increase the data available for analysis and would only increase the cost of the project by 12%.

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  • Funder: UK Research and Innovation Project Code: EP/N022661/1
    Funder Contribution: 432,288 GBP

    Site controlled semiconductor quantum dots (QDs) are the subject of world-wide interest because of their potential use in quantum information technologies and nanoscale optoelectronics. The goal is to create advanced QD architectures by controlling the precise position of single dots or molecules during epitaxial growth. However, a significant limitation in the realisation of site controlled III-V quantum structures is our inability to observe how they form in real-time and hence understand how to precisely tailor their characteristics. This project will utilise a unique electron microscope in Cardiff to obtain the first real-time movies of how QDs actually form in advanced architectures. This will provide unprecedented feedback to the National Centre for III-V Technologies and allow us to fabricate QDs with the best site control and optical properties ever achieved. These optimal structures will be tested optically with a view to commercial exploitation with Hitachi Europe Ltd for the large scale integration of single-photon (SP) sources into quantum photonic circuits and networks.

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  • Funder: UK Research and Innovation Project Code: NE/J015962/1
    Funder Contribution: 150,546 GBP

    Forecasting the weather from days to two weeks in advance has typically focused on the troposphere, the layer of the atmosphere closest to the ground. A typical weather forecast first attempts to estimate what the atmosphere is like now, and then extrapolates forward in time, using a complex model of the atmosphere based on the basic physical laws of motion. Over the last 15 years, evidence has been growing that different parts of the atmosphere and Earth system can also be exploited to improve weather forecasts. One of these regions is the stratosphere, the layer directly above the troposphere. Because, temperatures increase with height in the stratosphere, winds and weather systems are quite different, and a distinct community of scientific researchers who study the stratosphere exists around the world. Through the work of this community, many weather forecasting centres have been encouraged to look to the stratosphere to improve their weather forecasts and have been modifying their weather forecasting models accordingly. What has been missing, however, is a concerted effort to understand how best to make use of the stratosphere to improve weather forecasts and to determine how much weather forecasts might benefit. This proposal will fund a new international scientific network which will bring scientists from around the world together to study the stratosphere and how it might be used to improve weather forecasts. The network is made up of scientists from universities and weather forecasting centres around the world and is supported by two other international scientific research bodies. The network will allow scientists to come together to discuss current research in this area and to plan and carry out a new experiment which will compare the stratosphere and its impact on weather forecasts in their weather forecasting models. At the end of the research project, the network members will work together to produce a report which will provide guidance to all weather forecasting centres on the use of the stratosphere for weather forecasting.

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  • Funder: UK Research and Innovation Project Code: EP/I004475/1
    Funder Contribution: 1,172,100 GBP

    An important phenomenon in Nature is that of organization of many objects interacting together, which results into new entities with properties that are much more than the sum of the parts . For example the ability to think is a property of the brain as a whole and is the result of interactions that involves numerous neurons exchanging information in an organized way and is not a property of a single individual neuron. Similarly, in many technologically-important materials electrons also show a certain degree of order in that they correlate their motion with one another to avoid the strong repulsion that arise when they are brought close together. Such correlation effects can lead to surprising emergent material properties, which often can not be predicted in advance, such as superconductivity, where current flows with no resistance due to the fact that electrons travel in pairs in a very robust way. This proposal is to explore superconductivity and other novel form of electronic order stabilized by strong correlations in complex materials that are often not found in Nature but are artificially synthesized with the purpose to achieve certain material functionality. In 2008 the discovery of superconductivity a large class of materials based on Iron stimulated a revolution in condensed matter physics. This was most unexpected as usually Iron has strong ferromagnetic properties (attracting metals) that would normally destroy a superconducting state by breaking the special pairing between electrons. The large number of structural combinations in which iron-based superconductivity is found has raised the hope that the periodic table still holds the key to the discovery of new materials with extremely high superconducting temperatures which one day will revolutionize our way of living. In my first project I propose to take on the challenge of exploring deep into the nature of structural configurations, predicting electronic behaviors and testing experimentally novel superconductors. My second project aims to explore how electrons organize themselves in the presence of frustrated magnetic interactions. Imagine a restaurant with a number of triangular tables and a large number of male and female guests; if one tries to arrange guests such that everybody sits next to a person of the opposite sex, it cannot be realized even for one single table and many equally-unsatisfactory arrangements exist. The same kind of decision has to be made by magnetic spins which can point up or down on a triangular lattice and they cannot decide, so become frustrated. How electrons organize themselves and how they travel in such circumstances remains a mystery. Another amazing unexplored behaviour is that in which electrons are able to flow freely on the surface of a material but not inside it, giving rise to an insulator with a surface that conducts electricity. In this kind of topological insulator, as also in certain frustrated systems, conventional laws of physics do not apply as particles could be found in a superposition of several states at the same time, property that could be important for use in future quantum computers.For this research I use and plan to develop the most advanced tools for probing electron correlations in micron-size single crystalline materials using the highest magnetic fields in the world (a million times larger than earth's magnetic field), low temperatures near absolute zero and extreme high pressures to tune interactions and probe new electronic phases of matter.

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