Idealised simulations of cyclones with robust symmetrically-unstable sting jets

Idealised simulations of Shapiro-Keyser cyclones developing a sting jet (SJ) are presented. Thanks to an improved and accurate implementation of thermal wind balance in the initial state, it has been possible to use more realistic environments than in previous idealised studies. As a consequence, this study provides further insight in SJ evolution and dynamics and explores SJ robustness to different environmental conditions, assessed via a wide range of sensitivity experiments. The control simulation contains a cyclone that fits the Shapiro-Keyser conceptual model and develops a SJ whose dynamics are associated with the evolution of mesoscale instabilities along the airstream, including symmetric instability (SI). The SJ undergoes a strong descent while leaving the cloud-head banded tip and markedly accelerating towards the frontal-fracture region, revealed as an area of buckling of the already-sloped moist isentropes. Dry instabilities, generated by vorticity tilting via slantwise frontal motions in the cloud head, exist in similar proportions to moist instabilities at the start of the SJ descent and are then released along the SJ. The observed evolution supports the role of SI in the airstream’s dynamics proposed in a conceptual model outlined in a previous study. Sensitivity experiments illustrate that the SJ is a robust feature of intense Shapiro-Keyser cyclones, highlighting a range of different environmental conditions in which SI contributes to the evolution of this airstream, conditional on the model having adequate resolution. The results reveal that several environmental factors can modulate the strength of the SJ. However, a positive relationship between the strength of the SJ, both in terms of peak speed and amount of descent, and the amount of instability occurring along it can still be identified. In summary, the idealised simulations presented in this study show the robustness of SJ occurrence in intense Shapiro-Keyser cyclones and support and clarify the role of dry instabilities in SJ dynamics

Sting jets in extratropical cyclones: a review

This paper reviews the current state of knowledge of sting jets in extratropical cyclones. Sting jets were formally identified in 2004 by the pioneering work of Keith Browning. Reviewing this and subsequent studies, we define the sting jet as a coherent air flow that descends from mid-levels inside the cloud head into the frontal-fracture region of a Shapiro-Keyser cyclone over a period of a few hours leading to a distinct region of near-surface stronger winds. It therefore lies above the cold conveyor belt during some stage its life, but, at least in some cases, descends to reach the top of boundary layer ahead of the cold conveyor belt. It is not attributed to a specific mechanism in this definition. We conclude that it is likely that a continuum of sting jet descent and speed-up mechanisms exists. At one extreme is balanced descent partly associated with frontolysis in the frontal-fracture region. More horizontally small-scale and stronger frontolytic descent may occur associated with weak stability to slantwise convective downdraughts. Instability to slantwise convective downdraughts may occur in some systems, leading to multiple slantwise convective downdraughts associated with the release of conditional symmetric instability and even, possibly, symmetric instability. The global climatology of sting jets and the interaction between the atmospheric boundary layer and sting jets are revealed as specific areas where more research is needed. Finally, we describe eight myths and misunderstandings that exist in the current literature with the aim of guiding future research into the sting jet phenomenon

Silica scale formation and effect of sodium and aluminium ions -29Si NMR study

Silica scale formation on reverse osmosis (RO) membrane surface is a significant problem for operation of high recovery RO desalination plant. In this study we report the effects of sodium ions derived from sodium chloride and aluminium ions derived from aluminium chloride on dissolved silica species obtained from commercial sodium silicate solutions. Five dissolved silica species have been positively identified in sodium silica solutions. 29 Si NMR spectroscopy has proven to be particular well suited to obtain in situ information on the connectivity of silicon atoms in the solution and the impact of sodium and aluminium ions on connectivity between monomeric silica acid groups. Such information extends the understanding of how polysilicate ion mixtures change under different chemical conditions. Implications for RO desalination and silica scale formation on the membrane surface were discussed

Detection of coherent airstreams using cluster analysis: application to an extratropical cyclone

Flow in geophysical fluids is commonly summarized by coherent streams, for example conveyor belt flows in extratropical cyclones or jet streaks in the upper troposphere. Typically, parcel trajectories are calculated from the flow field and subjective thresholds are used to distinguish coherent streams of interest. This methodology contribution develops a more objective approach to distinguish coherent airstreams within extratropical cyclones. Agglomerative clustering is applied to trajectories along with a method to identify the optimal number of cluster classes. The methodology is applied to trajectories associated with the low-level jets of a well-studied extratropical cyclone. For computational efficiency, a constraint that trajectories must pass through these jet regions is applied prior to clustering; the partitioning into different airstreams is then performed by the agglomerative clustering. It is demonstrated that the methodology can identify the salient flow structures of cyclones: the warm and cold conveyor belts. A test focusing on the airstreams terminating at the tip of the bent-back front further demonstrates the success of the method in that it can distinguish fine-scale flow structure such as descending sting jet airstreams

Sting-jet windstorms over the North Atlantic: climatology and contribution to extreme wind risk

Extratropical cyclones with damaging winds can have large socio-economic impacts when they make landfall. During the last decade, studies have identified a mesoscale transient jet, the sting jet, that descends from the tip of the hooked cloud head towards the top of the boundary layer in the dry intrusion region as a cause of strong surface winds, and especially gusts, in some cyclones. While many case studies have focused on the dynamics and characteristics of these jets, there have been few studies that assess the climatology of the associated cyclones and their importance for wind risk. Here we determine the climatological characteristics of North Atlantic cyclones in terms of the possibility that they had sting jets using a previously-published sting-jet precursor diagnostic applied to ERA-Interim data over 32 extended winter seasons from 1979–2012. Of the 5447 cyclones tracked, 32% had the precursor (42% in the 22% of cyclones that developed explosively). Precursor storms have a more southerly and zonal storm track than storms without the precursor and precursor storms tend to be more intense as defined by 850-hPa relative vorticity. This study also shows that precursor storms are the dominant cause of cyclone-related resolved strong wind events over the British Isles for 850-hPa windspeeds exceeding 30 ms−1. Hence, early detection of a sting jet storm could give advance warning of enhanced wind risk. However, over continental northwestern Europe, precusor cyclone-related windstorm events occur far less often

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The role of mesoscale instabilities in the sting-jet dynamics of windstorm Tini

Sting jets (SJ) occur as an additional region of low-level strong winds in some Shapiro-Keyser-type extra-tropical cyclones. While SJs are widely accepted as being distinct from the warm and cold conveyor belts, the mechanisms responsible for their occurrence are still not fully understood. Here we determine the relative importance of the release of mesoscale instabilities and synoptic-scale cyclone dynamics, so addressing an area of current debate. Numerical weather prediction simulations of a SJ-containing windstorm are analysed and Lagrangian trajectories used to assess the evolution of, and mesoscale atmospheric instabilities (e.g. symmetric and inertial instabilities) in, the descending airstream. The SJ undergoes a two-stage descent: cooling via sublimation followed by a large acceleration accompanied by instability release. Combined tilting and stretching of vorticity play a major role in the local onset of instability on the airstream. Vorticity and frontogenesis fields have a narrow slantwise banded structure in the cloud head and around the SJ; the descending SJ modifies the widespread frontolysis expected from the large-scale dynamics alone in the frontal-fracture region. A coarser-resolution simulation also generates strong winds in the frontal-fracture region, although these are significantly weaker than in the higher-resolution simulation. The SJ airstream in the coarser-resolution simulation undergoes a weaker descent without instability generation and descends in a widespread frontolytic region. Hence, while the SJ undergoes a process of destabilisation that enhances its descent and acceleration in the higher-resolution simulation, enhancing the strong winds already generated by the synoptic-scale cyclone dynamics, this destabilisation does not occur in the SJ produced by a coarser-resolution simulation, resulting in weaker winds. This analysis reveals the synergy between the paradigms of SJ occurrence through the release of mesoscale instabilities and synoptic-scale cyclone dynamics and demonstrates that the current debate may in part be a consequence of the model resolutions used by different studies

Microsomal triglyceride transfer protein expression in adipocytes: A new component in fat metabolism

AbstractMicrosomal triglyceride transfer protein (MTP) is a carrier of triglyceride essential for the assembly of apolipoprotein (apo)B-containing lipoproteins by the liver and the small intestine. Its role in triglyceride transfer in tissues that do not secrete lipoproteins has not been explored. In particular, MTP would seem to be a candidate for a role in triglyceride metabolism within the adipocyte. To test this hypothesis, we probed adipocytes for the presence of MTP. Immunohistochemical and biochemical studies demonstrate MTP in adipocytes from brown and white fat depots of mice and human, as well as in 3T3-L1 cells. Confocal microscopy revealed MTP throughout 3T3 cells; however, MTP fluorescence was prominent in juxtanuclear areas. In differentiated 3T3 cells MTP fluorescence was very striking around lipid droplets. In vitro lipid transfer assays demonstrated the presence of triglyceride transfer activity within microsomal fractions isolated from rat adipose tissue. In addition, quantitative rtPCR studies showed that MTP expression in mouse white fat depots was approximately 1% of MTP expression in mouse liver. MTP mRNA in differentiated 3T3 cells was approximately 13% of liver expression. Our results provide unequivocal evidence for the presence of MTP in adipocytes and present new possibilities for defining the mechanisms by which triglyceride is stored and/or hydrolyzed and mobilized

Policy recommendations from the 13th ICABR conference on the emerging bioeconomy

The International Consortium on Agricultural Biotechnology Research held its 13th annual conference in Ravello, Italy in June 2009. The theme of the conference was the bioeconomy,and this topic was addressed through research presentations from academia, government, and industry. Numerous presentations from developing countries highlighted the benefits of agricultural biotechnology in these nations. The broad range of presentations provided a wealth of insights, resulting in three policy recommendations regarding future funding, international regulation, and technology transfer.global food crisis, biofuels, food safety, innovation