An easterly tip jet off Cape Farewell, Greenland. II: Simulations and dynamics

An easterly tip jet that occurred on 21 February 2007 off Cape Farewell, Greenland, is examined. In Part I of this article aircraft observations were described. Now, in Part II, numerical simulations and an analysis of the dynamical forcing mechanisms are presented. The simulations make use of a limited-area 12 km resolution configuration of the Met Office's Unified Model. Sea-surface temperatures and sea-ice concentrations have been replaced using the Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) product, addressing a boundary-layer temperature bias, while roughness lengths over sea ice have been updated, addressing a wind-speed bias. These modifications ensured a reasonably accurate simulation: generally within 1–2 K and 2–3 m s-1 when compared with dropsonde observations. A momentum-budget analysis along a curved locus through the core of the jet has been derived. Off southeast Greenland, the easterly tip jet was in cross-jet geostrophic balance, but was being accelerated downstream by an along-jet pressure gradient. Over the curved part of the locus, as the jet rounded Cape Farewell, a cross-jet residual suggests that the jet was unbalanced at the height of the jet core. This residual decreases with height so that an approximate gradient wind balance applies in the upper part of the jet. The anticyclonic curvature, characteristic of easterly tip jets, was caused by a dramatic decrease in the cross-jet pressure-gradient force at the end of the barrier, after which the jet aligned with the synoptic-scale isobars and returned to approximate geostrophic balance. The momentum budget is shown to be robust and applicable to other cases

"No level up!": no effects of video game specialization and expertise on cognitive performance

Previous research into the effects of action video gaming on cognition has suggested that long term exposure to this type of game might lead to an enhancement of cognitive skills that transfer to non-gaming cognitive tasks. However, these results have been controversial. The aim of the current study was to test the presence of positive cognitive transfer from action video games to two cognitive tasks. More specifically, this study investigated the effects that participants’ expertise and genre specialisation have on cognitive improvements in one task unrelated to video gaming (a flanker task) and one related task (change detection task with both control and genre-specific images). This study was unique in three ways. Firstly, it analysed a continuum of expertise levels, which has yet to be investigated in research into the cognitive benefits of video gaming. Secondly, it explored genre-specific skill developments on these tasks by comparing Action and Strategy video game players. Thirdly, it used a very tight experiment design, including the experimenter being blind to expertise level and genre specialisation of the participant. Ninety-two university students aged between 18 and 30 (M = 21.25) were recruited through opportunistic sampling and were grouped by video game specialization and expertise level. While the results of the flanker task were consistent with previous research (i.e. effect of congruence), there was no effect of expertise, and the action gamers failed to outperform the strategy gamers. Additionally, contrary to expectation, there was no interaction between genre specialisation and image type in the change detection task, again demonstrating no expertise effect. The lack of effects for game specialization and expertise goes against previous research on the positive effects of action video gaming on other cognitive tasks

Probability cueing of distractor locations: both intertrial facilitation and statistical learning mediate interference reduction

Targets in a visual search task are detected faster if they appear in a probable target region as compared to a less probable target region, an effect which has been termed “probability cueing.” The present study investigated whether probability cueing cannot only speed up target detection, but also minimize distraction by distractors in probable distractor regions as compared to distractors in less probable distractor regions. To this end, three visual search experiments with a salient, but task-irrelevant, distractor (“additional singleton”) were conducted. Experiment 1 demonstrated that observers can utilize uneven spatial distractor distributions to selectively reduce interference by distractors in frequent distractor regions as compared to distractors in rare distractor regions. Experiments 2 and 3 showed that intertrial facilitation, i.e., distractor position repetitions, and statistical learning (independent of distractor position repetitions) both contribute to the probability cueing effect for distractor locations. Taken together, the present results demonstrate that probability cueing of distractor locations has the potential to serve as a strong attentional cue for the shielding of likely distractor locations

A classical-theory-based parameterization of heterogeneous ice nucleation by mineral dust, soot, and biological particles in a global climate model

An ice nucleation parameterization based on classical nucleation theory, with aerosol-specific parameters derived from experiments, has been implemented into a global climate model-the Community Atmosphere Model (CAM)-Oslo. The parameterization treats immersion, contact, and deposition nucleation by mineral dust, soot, bacteria, fungal spores, and pollen in mixed-phase clouds at temperatures between 0° and -38°C. Immersion freezing is considered for insoluble particles that are activated to cloud droplets, and deposition and contact nucleation are only allowed for uncoated, unactivated aerosols. Immersion freezing by mineral dust is found to be the dominant ice formation process, followed by immersion and contact freezing by soot. The simulated biological aerosol contribution to global atmospheric ice formation is marginal, even with high estimates of their ice nucleation activity, because the number concentration of ice nucleation active biological particles in the atmosphere is low compared to other ice nucleating aerosols. Because of the dominance of mineral dust, the simulated ice nuclei concentrations at temperatures below -20°C are found to correlate with coarse-mode aerosol particle concentrations. The ice nuclei (IN) concentrations in the model agree well overall with in situ continuous flow diffusion chamber measurements. At individual locations, the model exhibits a stronger temperature dependence on IN concentrations than what is observed. The simulated IN composition (77 mineral dust, 23 soot, and 10 -5 biological particles) lies in the range of observed ice nuclei and ice crystal residue compositions

The phylogenetic diversity of Thermus and Meiothermus from microbial mats of an Australian subsurface aquifer runoff channel

Spectral analysis of the cell free extracts of four mat samples colonizing a Great Artesian Bain (GAB) aquifer bore runoff channel suggested that Thermus was present in the 75 °C grey mat, Meiothermus was present in the 66 °C red mat, a mixed population of Meiothermus/Thermus and photosynthetic microbes were present in the 57 °C green mat and photosynthetic microbes were present in the 52 °C brown mat. Enumeration studies indicated that Thermus dominated the grey mats and Meiothermus dominated the red mat but both were absent in samples collected at the bore source (89 °C) and below the bore source (88 °C). Culture-dependent studies followed by 16S rRNA gene sequence analysis indicated that 13 of the 14 Thermus isolates clustered closely with each other and to T. igniterrae, with the remaining strain clustering with Thermus strain SRI-96. The two Meiothermus isolates were closely related to Meiothermus ruber. A culture-independent study with 367 16S rRNA gene clones concurred that Thermus dominated the grey mat, but to a lesser extent in the red mat and the green mats and its complete absence in the brown mat. Of the four Thermus phylogroups identified one phylogroup dominated the cloned library and was related to the cluster represented by T. scotoductus. The second most dominant phylogroup was related to the cluster represented by T. igniterrae and the third and fourth phylogroups, which were the least dominant, were related to cluster represented by Thermus strain SRI-248 and T. oshima respectively. Meiothermus was only represented in the 16S rRNA gene libraries of the red, green and brown mats and formed two phylogroups, of which the most dominant was associated with the red mat and phylogenetically related to M. ruber while the second phylogroup was found only in the green mat gene library and was related to M. cerberus