The turbulent mixing in thin ocean surface boundary layers (OSBL), which occupy the upper 100 m or so of the ocean, control the exchange of heat and trace gases between the atmosphere and ocean. Here ...we show that current parameterizations of this turbulent mixing lead to systematic and substantial errors in the depth of the OSBL in global climate models, which then leads to biases in sea surface temperature. One reason, we argue, is that current parameterizations are missing key surface‐wave processes that force Langmuir turbulence that deepens the OSBL more rapidly than steady wind forcing. Scaling arguments are presented to identify two dimensionless parameters that measure the importance of wave forcing against wind forcing, and against buoyancy forcing. A global perspective on the occurrence of wave‐forced turbulence is developed using re‐analysis data to compute these parameters globally. The diagnostic study developed here suggests that turbulent energy available for mixing the OSBL is under‐estimated without forcing by surface waves. Wave‐forcing and hence Langmuir turbulence could be important over wide areas of the ocean and in all seasons in the Southern Ocean. We conclude that surface‐wave‐forced Langmuir turbulence is an important process in the OSBL that requires parameterization.
Key Points
Climate models have biases in the depth of the ocean surface boundary layer
Langmuir turbulence is a key process mixing the ocean surface boundary layer
Langmuir turbulence deepens the layer more quickly than wind‐forced turbulence
A sea ice concentration and motion assimilation scheme has been developed using the Met Office Forecasting Ocean Assimilation Model (FOAM). FOAM has been upgraded to include a more realistic sea ice ...rheology and a sea ice thickness distribution. The sea ice data assimilation scheme uses Special Sensor Microwave Imager (SSMI) and QuikSCAT satellite observations to provide ice concentration and motion. A number of 1‐year test integrations have been undertaken, and the resulting sea ice analysis has been examined in detail. The assimilation is able to significantly reduce the model sea ice concentration error and is able to address the model biases. Owing to the faster response times of the elastic‐viscous‐plastic (EVP) sea ice rheology in the model compared to the viscous‐plastic used in previous studies, a novel approach to sea ice motion assimilation using increments to the ice stress has been developed. The sea ice motion assimilation scheme is able to reduce the model sea ice velocity errors by approximately 50% when compared to independent data. Ice velocity assimilation was found to have little impact on the ice concentration, and ice concentration assimilation is found to have little impact on ice velocities. This implies that ice concentrations are primarily thermodynamically controlled and ice velocities are primarily dynamically driven. During the summer, model biases and poor‐quality observations impair the performance of the assimilation.
A new niobium-doped inorganic scintillating oxyfluoride, Rb4Ge5O9F6:Nb, was synthesized in single crystal form by high-temperature flux growth. The host structure, Rb4Ge5O9F6, crystallizes in the ...orthorhombic space group Pbcn with lattice parameters a = 6.98430(10) Å, b = 11.7265(2) Å, and c = 19.2732(3) Å, consisting of germanium oxyfluoride layers made up of Ge3O9 units connected by GeO3F3 octahedra. In its pure form, Rb4Ge5O9F6 shows neither luminescence nor scintillation but when doped with niobium, Rb4Ge5O9F6:Nb exhibits bright blue luminescence and scintillation. The isostructural doped structure, Rb4Ge5O9F6:Nb, crystallizes in the orthorhombic space group Pbcn with lattice parameters a = 6.9960(3) Å, b = 11.7464(6) Å, and c = 19.3341(9) Å. X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements suggest that the niobium is located in an octahedral coordination environment. Optical measurements inform us that the niobium dopant acts as the activator. The synthesis, structure, and optical properties are reported, including radioluminescence (RL) measurements under X-ray irradiation.
Two new alkali bismuth silicates were prepared via high temperature flux crystal growth and their structures characterized by single crystal X-ray diffraction (SXRD). Cs3BiSi8O19 and Cs4Bi2Si8O21, ...crystallize in the orthorhombic space groups Pnma (a = 11.5903, b = 7.0346, c = 26.7393) and Pnn2 (a = 14.2674, b = 33.8270, c = 7.24260) respectively. Cs3BiSi8O19 was modified via ion exchange (K for Cs) and Cs4Bi2Si8O21 via Eu doping in a flux environment yielding Cs0.79K2.21BiSi8O19 and Cs4Bi1.72Eu0.28Si8O21, respectively. The two phases crystallize in the orthorhombic space group Cmcm and the monoclinic space group P21/n, respectively. Photoluminescence measurements demonstrated that the europium doped Cs4Bi1.72Eu0.28Si8O21 exhibited emission corresponding to the 5D0 → 7F2 (613 nm) red emission and 5D0 → 7F1 (590 nm) orange emission, characteristic of Eu3+ f-f transitions.
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•Two new bismuth silicates, Cs3BiSi8O19 and Cs4Bi2Si8O21 were synthesized using the molten-flux method.•The crystal structures of the compounds were determined using single crystal X-ray diffraction.•Alkali ion-exchange and luminescent properties of the host compounds were investigated.
Single crystals of a series of rare earth borates, A3Ln (BO3) (A = Na, K; Ln = Eu, Tb), were synthesized using a boric acid/hydroxide melt. The Na3Ln (BO3)2 borates crystallized in the monoclinic ...system with space group P21/n, and the K3Ln (BO3)2 borates crystallized in the orthorhombic system with space group Pnma. The luminescence of these borates was investigated under ultraviolet and X-ray excitations for the first time. Radioluminescence (RL) measurements showed K3Tb(BO3)2 to be the brightest compound, with an integral intensity equal to 55% of the integral emission of Bi4Ge3O12 (BGO) powder.
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•This study is the first to assimilate partitioned HF radar wave data.•Relative advantages of assimilating partitions over mean parameters are discussed.•Independent buoy data is used to validate the ...assimilation experiments.•Background error covariances are specifically designed for the coastal region.•Correlations are specified to reflect the complex coastline and bathymetry.
In this study the assimilation of HF radar data into a high resolution, coastal Wavewatch III model is investigated. An optimal interpolation scheme is used to assimilate the data and the design of a background error covariance matrix which reflects the local conditions and difficulties associated with a coastal domain is discussed. Two assimilation schemes are trialled; a scheme which assimilates mean parameters from the HF radar data and a scheme which assimilates partitioned spectral HF radar data. This study demonstrates the feasibility of assimilating partitioned wave data into a coastal domain. The results show that the assimilation schemes provide satisfactory improvements to significant wave heights but more mixed results for mean periods. The best improvements are seen during a stormy period with turning winds. During this period the model is deficient at capturing the change in wave directions and the peak in the waveheights, while the high sea state ensures good quality HF radar data for assimilation. The study also suggests that there are both physical and practical advantages to assimilating partitioned wave data compared to assimilating mean parameters for the whole spectrum.
Crystals of the title compound BiCuI.sub.5(phen).sub.2 were synthesized solvothermally by reacting CuCl.sub.2·2H.sub.2O, Bi(NO.sub.3).sub.3·5H.sub.2O, NH.sub.4I, and 1,10-phenanthroline in an ...ethanol/water solvent mixture. BiCuI.sub.5(phen).sub.2 crystallizes in the monoclinic space group P2.sub.1/n. The asymmetric unit consists of a Bi.sub.2I.sub.10 iodobismuthate group and a CuI(phen).sub.2 complex that are linked via a shared iodine. In this paper, we describe the synthesis and single crystal structure of the new metal-organic halobismuthate complex, BiCuI.sub.5(phen).sub.2. Graphical X-ray diffraction quality single crystals of a novel metal-organic halobismuthate, BiCuI.sub.5(phen).sub.2 were grown in water/ethanol solvent mixture at 120 °C and used for structure determination using single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2.sub.1/n.
Extreme weather events have become a dominant feature of the narrative surrounding changes in global climate with large impacts on ecosystem stability, functioning and resilience; however, ...understanding of their risk of co‐occurrence at the regional scale is lacking. Based on the UK Met Office’s long‐term temperature and rainfall records, we present the first evidence demonstrating significant increases in the magnitude, direction of change and spatial co‐localisation of extreme weather events since 1961. Combining this new understanding with land‐use data sets allowed us to assess the likely consequences on future agricultural production and conservation priority areas. All land‐uses are impacted by the increasing risk of at least one extreme event and conservation areas were identified as the hotspots of risk for the co‐occurrence of multiple event types. Our findings provide a basis to regionally guide land‐use optimisation, land management practices and regulatory actions preserving ecosystem services against multiple climate threats.
Extreme weather events have become a dominant feature of the narrative surrounding changes in global climate with large‐scale implications for ecosystem function. Based on the UK Met Office’s long‐term high‐resolution temperature and rainfall records, we present the first evidence demonstrating significant increases in the magnitude, direction of change and spatial co‐localisation of extreme weather events since 1961. Combining this new understanding with land‐use data sets allowed us to assess the likely consequences of these events on future agricultural production and conservation priority areas.
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