Rapid declines in Arctic sea ice have captured attention and pose significant challenges to a variety of stakeholders. There is a rising demand for Arctic sea ice prediction at daily to seasonal time scales, which is ...Rapid declines in Arctic sea ice have captured attention and pose significant challenges to a variety of stakeholders. There is a rising demand for Arctic sea ice prediction at daily to seasonal time scales, which is partly a sea ice initial condition problem. Thus, a multivariate data assimilation that integrates sea ice observations to generate realistic and skillful model initialization is needed to improve predictive skill of Arctic sea ice. Sea ice data assimilation is a relatively new research area. In this review paper, we focus on two challenges for implementing multivariate data assimilation systems for sea ice forecast. First, to address the challenge of limited spatiotemporal coverage and large uncertainties of observations, we discuss sea ice parameters derived from satellite remote sensing that(1) have been utilized for improved model initialization, including concentration, thickness and drift, and(2) are currently under development with the potential for enhancing the predictability of Arctic sea ice, including melt ponds and sea ice leads. Second, to strive to generate the ‘‘best" estimate of sea ice initial conditions by combining model simulations/forecasts and observations, we review capabilities and limitations of different data assimilation techniques that have been developed and used to assimilate observed sea ice parameters in dynamical models.展开更多
In recent decades, significant changes of Arctic sea ice have taken place. These changes are expected to influence the surface energy balance of the ice-covered Arctic Ocean. To quantify this energy balance and to inc...In recent decades, significant changes of Arctic sea ice have taken place. These changes are expected to influence the surface energy balance of the ice-covered Arctic Ocean. To quantify this energy balance and to increase our understanding of mechanisms leading to observed changes in the Arctic sea ice, the project ＂Advancing Modelling and Observing solar Radiation of Arctic sea ice--understanding changes and processes （AMORA）＂ was initiated and conducted from 2009 to 2013. AMORA was funded and organized under a frame of Norway-China bilateral collaboration program with partners from Finland, Germany, and the USA. The primary goal of the project was achieved by developing an autonomous spectral radiation buoy, deploying it on drifting sea ice close to the North Pole, and receiving a high-resolution time series of spectral radiation over and under sea ice from spring （before melt onset） to autumn （after freeze-up） 2012. Beyond this, in-situ sea ice data were collected during several field campaigns and simulations of snow and sea ice thermodynamics were performed. More autonomous measurements are available through deployments of sea ice mass balance buoys. These new observational data along with numerical model studies are helping us to better understand the key thermodynamic processes of Arctic sea ice and changes in polar climate. A strong scientific, but also cultural exchange between Norway, China, and the partners from the USA and Europe initiated new collaborations in Arctic reseach.展开更多
Multilayer Laue lenses are volume diffraction elements for the efficient focusing of X-rays.With a new manufacturing technique that we introduced,it is possible to fabricate lenses of sufficiently high numerical apert...Multilayer Laue lenses are volume diffraction elements for the efficient focusing of X-rays.With a new manufacturing technique that we introduced,it is possible to fabricate lenses of sufficiently high numerical aperture(NA)to achieve focal spot sizes below 10 nm.The alternating layers of the materials that form the lens must span a broad range of thicknesses on the nanometer scale to achieve the necessary range of X-ray deflection angles required to achieve a high NA.This poses a challenge to both the accuracy of the deposition process and the control of the materials properties,which often vary with layer thickness.We introduced a new pair of materials—tungsten carbide and silicon carbide—to prepare layered structures with smooth and sharp interfaces and with no material phase transitions that hampered the manufacture of previous lenses.Using a pair of multilayer Laue lenses(MLLs)fabricated from this system,we achieved a two-dimensional focus of 8.4×6.8 nm2 at a photon energy of 16.3 keV with high diffraction efficiency and demonstrated scanning-based imaging of samples with a resolution well below 10 nm.The high NA also allowed projection holographic imaging with strong phase contrast over a large range of magnifications.An error analysis indicates the possibility of achieving 1 nm focusing.展开更多
The Polar Regions play an important role in the global processes of our planet, from climate change to sea level rise, protection from UV （ultraviolet） radiation to uptake of carbon dioxide. In addition, their scien...The Polar Regions play an important role in the global processes of our planet, from climate change to sea level rise, protection from UV （ultraviolet） radiation to uptake of carbon dioxide. In addition, their scientific importance, extraordinary beauty and adventurous history provide perfect ingredients for both education and public outreach.Polar examples provide an excellent way to transmit basic concepts about a wide range of STEM （science, technology, engineering and mathematics） disciplines. The IPY （International Polar Year） brought educators and scientists together and provided the incentive for the formation of the PEI （Polar Educators International）, an organization encouraging the exchange of ideas between educators and researchers and enhancement of the profile of polar education on the international scene. Educators must be adequately informed about current scientific polar research and have the confidenceto teach it to students. Scientists have the knowledge and data to explain these complexities, but may lack the communication skills to make the subject accessible to non-technical audiences. The development of this new network between polar educators and scientists has the potential to break down walls that restrict international collaboration and understanding, provide educators with topical and reliable information and share best practices internationally in an effective way.展开更多
基金supported by the National Key R&D Program of China (2018YFA0605901)the NOAA Climate Program Office (NA15OAR4310163)+1 种基金the National Natural Science Foundation of China (41676185)and the Key Research Program of Frontier Sciences of Chinese Academy of Sciences (QYZDY-SSW-DQC021)
文摘Rapid declines in Arctic sea ice have captured attention and pose significant challenges to a variety of stakeholders. There is a rising demand for Arctic sea ice prediction at daily to seasonal time scales, which is partly a sea ice initial condition problem. Thus, a multivariate data assimilation that integrates sea ice observations to generate realistic and skillful model initialization is needed to improve predictive skill of Arctic sea ice. Sea ice data assimilation is a relatively new research area. In this review paper, we focus on two challenges for implementing multivariate data assimilation systems for sea ice forecast. First, to address the challenge of limited spatiotemporal coverage and large uncertainties of observations, we discuss sea ice parameters derived from satellite remote sensing that(1) have been utilized for improved model initialization, including concentration, thickness and drift, and(2) are currently under development with the potential for enhancing the predictability of Arctic sea ice, including melt ponds and sea ice leads. Second, to strive to generate the ‘‘best" estimate of sea ice initial conditions by combining model simulations/forecasts and observations, we review capabilities and limitations of different data assimilation techniques that have been developed and used to assimilate observed sea ice parameters in dynamical models.
基金supported by the Research Council of Norway through AMORA (grant 193592)the Norwegian Polar Institute (NPI) and its Center for Ice, Climate and Ecosystems (ICE)support came from all partner institutes:Alfred-Wegener-Institut Helmholtz-Zentrum für Polarund Meeresforschung,Polar Research Institute of China,Dalian University of Technology(Grant no.NSFC41376186),Finnish Meteorological Institute, and the Cold Regions Research and Engineering Laboratory
文摘In recent decades, significant changes of Arctic sea ice have taken place. These changes are expected to influence the surface energy balance of the ice-covered Arctic Ocean. To quantify this energy balance and to increase our understanding of mechanisms leading to observed changes in the Arctic sea ice, the project ＂Advancing Modelling and Observing solar Radiation of Arctic sea ice--understanding changes and processes （AMORA）＂ was initiated and conducted from 2009 to 2013. AMORA was funded and organized under a frame of Norway-China bilateral collaboration program with partners from Finland, Germany, and the USA. The primary goal of the project was achieved by developing an autonomous spectral radiation buoy, deploying it on drifting sea ice close to the North Pole, and receiving a high-resolution time series of spectral radiation over and under sea ice from spring （before melt onset） to autumn （after freeze-up） 2012. Beyond this, in-situ sea ice data were collected during several field campaigns and simulations of snow and sea ice thermodynamics were performed. More autonomous measurements are available through deployments of sea ice mass balance buoys. These new observational data along with numerical model studies are helping us to better understand the key thermodynamic processes of Arctic sea ice and changes in polar climate. A strong scientific, but also cultural exchange between Norway, China, and the partners from the USA and Europe initiated new collaborations in Arctic reseach.
基金supported by Joachim Herz Stiftungthe Helmholtz Association through program-oriented funds.
文摘Multilayer Laue lenses are volume diffraction elements for the efficient focusing of X-rays.With a new manufacturing technique that we introduced,it is possible to fabricate lenses of sufficiently high numerical aperture(NA)to achieve focal spot sizes below 10 nm.The alternating layers of the materials that form the lens must span a broad range of thicknesses on the nanometer scale to achieve the necessary range of X-ray deflection angles required to achieve a high NA.This poses a challenge to both the accuracy of the deposition process and the control of the materials properties,which often vary with layer thickness.We introduced a new pair of materials—tungsten carbide and silicon carbide—to prepare layered structures with smooth and sharp interfaces and with no material phase transitions that hampered the manufacture of previous lenses.Using a pair of multilayer Laue lenses(MLLs)fabricated from this system,we achieved a two-dimensional focus of 8.4×6.8 nm2 at a photon energy of 16.3 keV with high diffraction efficiency and demonstrated scanning-based imaging of samples with a resolution well below 10 nm.The high NA also allowed projection holographic imaging with strong phase contrast over a large range of magnifications.An error analysis indicates the possibility of achieving 1 nm focusing.
文摘The Polar Regions play an important role in the global processes of our planet, from climate change to sea level rise, protection from UV （ultraviolet） radiation to uptake of carbon dioxide. In addition, their scientific importance, extraordinary beauty and adventurous history provide perfect ingredients for both education and public outreach.Polar examples provide an excellent way to transmit basic concepts about a wide range of STEM （science, technology, engineering and mathematics） disciplines. The IPY （International Polar Year） brought educators and scientists together and provided the incentive for the formation of the PEI （Polar Educators International）, an organization encouraging the exchange of ideas between educators and researchers and enhancement of the profile of polar education on the international scene. Educators must be adequately informed about current scientific polar research and have the confidenceto teach it to students. Scientists have the knowledge and data to explain these complexities, but may lack the communication skills to make the subject accessible to non-technical audiences. The development of this new network between polar educators and scientists has the potential to break down walls that restrict international collaboration and understanding, provide educators with topical and reliable information and share best practices internationally in an effective way.
