Mediterranean cyclones and windstorms in a changing climate

Changes in the frequency and intensity of cyclones and associated windstorms affecting the Medi-terranean region simulated under enhanced Greenhouse Gas forcing conditions are investigated. The analysis is based on 7 climate model integrations performed with two coupled global models (ECHAM5 MPIOM and INGV CMCC), comparing the end of the twentieth century and at least the first half of the twenty-first century. As one of the models has a considerably enhanced resolution of the atmosphere and the ocean, it is also investigated whether the climate change signals are influenced by the model resolution. While the higher resolved simulation is closer to reanalysis climatology, both in terms of cyclones and windstorm distributions, there is no evidence for an influence of the resolution on the sign of the climate change signal. All model simulations show a reduction in the total number of cyclones crossing the Mediterranean region under climate change conditions. Exceptions are Morocco and the Levant region, where the models predict an increase in the number of cyclones. The reduction is especially strong for intense cyclones in terms of their Laplacian of pressure. The influence of the simulated positive shift in the NAO Index on the cyclone decrease is restricted to the Western Mediterranean region, where it explains 10–50 % of the simulated trend, depending on the individual simulation. With respect to windstorms, decreases are simulated over most of the Mediterranean basin. This overall reduction is due to a decrease in the number of events associated with local cyclones, while the number of events associated with cyclones outside of the Mediterranean region slightly increases. These systems are, however, less intense in terms of their integrated severity over the Mediterranean area, as they mostly affect the fringes of the region. In spite of the general reduction in total numbers, several cyclones and windstorms of intensity unknown under current climate conditions are identified for the scenario simulations. For these events, no common trend exists in the individual simulations. Thus, they may rather be attributed to long-term (e.g. decadal) variability than to the Greenhouse Gas forcing. Nevertheless, the result indicates that high-impact weather systems will remain an important risk in the Mediterranean Basin

Upper-tropospheric downstream development leading to surface cyclogenesis in the central Mediterranean

In this study an attempt is made to investigate the upper-tropospheric downstream development over north-west Europe, which leads to surface cyclogenesis in the central Mediterranean. A case study is analysed to demonstrate that the upper-tropospheric downstream development could be closely related to the upper-tropospheric frontogenesis that appears upon the north-eastern flank of a blocking high. The frontogenesis is characterised by a jet streak within a strongly baroclinic zone and a tropopause folding associated with cold stratospheric air intrusion into the troposphere. According to this interpretation, the eddy ageostrophic divergence of eddy geopotential fluxes (dispersion and spreading of eddy kinetic energy), other than friction dissipation and barotropic conversion to the mean flow, is mainly responsible for the loss of Kinetic energy from a decaying depression of synoptic scale that has passed the mature stage. This dispersed eddy Kinetic energy accumulates in the vicinity of the aforementioned jet streak where it is transferred downstream and further triggers the generation or rejuvenation of a new disturbance

Quasi-Lagrangian energetics of an intense Mediterranean cyclone

Studies of the energetics of synoptic-scale systems and similar kinds of investigation have traditionally used a Eulerian framework. In this study, the energetics of a synoptic-scale system have been considered using a quasi-Lagrangian method, in order to isolate the disturbance under consideration within a volume which moves together with the system at each stage of its development. Applying a Lagrangian framework implies that the dimensions of the computational area can be modified on the basis of predetermined criteria. In this study, an area surrounding a depression as shown on the surface analysis, has been selected. This area moves together with the centre of the depression. The energetics results obtained using such a quasi-Lagrangian scheme are compared to those obtained by using a Eulerian framework. The synoptic-scale system studied here is a wintertime frontal depression, the greatest development of which occurred in the central Mediterranean on 7 December 1991. This depression moved east accompanied by significant temperature changes, heavy precipitation and gale force winds

A comparison of temperature inversion statistics at a coastal and a non-coastal location influenced by the same synoptic regime

The primary aim of this work is to examine to what extent the climatology of atmospheric temperature inversions at one location is site specific, and to what extent it reflects a wider area for which the same synoptic conditions can be assumed. To this end radiosonde data from a coastal and a non-coastal location in eastern England separated by 210 km and influenced by the same synoptic conditions are used. Analysis of these data shows that there is a pronounced difference between the inversion climatologies at the two sites. The vertical distribution of base-heights of inversions has a very distinct maximum at a height of about 200 m at the location proximate to the coast. This maximum is not present at the inland location, and the difference is due to both sea-breezes and advection from the sea due to synoptic-scale wind field. Examining the vertical distributions of base-heights of inversions at the two locations under conditions that either maximize or minimize the effect of sea-breeze it is found that the differences in the two distributions are to a certain extent deterministic (therefore predictable) rather than random, as the dominant mechanisms which are responsible for these differences (diurnal and yearly cycles) have an obvious regularity. Using standard statistical methods it is further shown that, apart from this difference, nearly all other inversion statistics for the two locations are similar when the atmospheric layer from surface to 700 hPa is taken into consideration. However, when only the first inversion in each temperature profile is considered, the inversions activity throughout the year, defined with the aid of an index, in the two locations is not correlated, indicating that for the lowest part of the surface-700 hPa region, local factors overwhelm the synoptic conditions. Thus, these results provide evidence that the inversion climatology at one location can be generalised over a wider area where the same synoptic regime can be assumed. Given that, at least to an extent, any differences in the characteristics of inversions due to local factors can be inferred once the underlying mechanisms are carefully studied, this work has also important implications for micrometeorological studies as for instance the local diffusion and transport of air pollutans

Evaluation of outcomes among patients with traumatic intracranial hypertension treated with decompressive craniectomy vs standard medical care at 24 month

Importance Trials often assess primary outcomes of traumatic brain injury at 6 months. Longer-term data are needed to assess outcomes for patients receiving surgical vs medical treatment for traumatic intracranial hypertension. Objective To evaluate 24-month outcomes for patients with traumatic intracranial hypertension treated with decompressive craniectomy or standard medical care. Design, Setting, and Participants Prespecified secondary analysis of the Randomized Evaluation of Surgery With Craniectomy for Uncontrollable Elevation of Intracranial Pressure (RESCUEicp) randomized clinical trial data was performed for patients with traumatic intracranial hypertension (>25 mm Hg) from 52 centers in 20 countries. Enrollment occurred between January 2004 and March 2014. Data were analyzed between 2018 and 2021. Eligibility criteria were age 10 to 65 years, traumatic brain injury (confirmed via computed tomography), intracranial pressure monitoring, and sustained and refractory elevated intracranial pressure for 1 to 12 hours despite pressure-controlling measures. Exclusion criteria were bilateral fixed and dilated pupils, bleeding diathesis, or unsurvivable injury. Interventions Patients were randomly assigned 1:1 to receive a decompressive craniectomy with standard care (surgical group) or to ongoing medical treatment with the option to add barbiturate infusion (medical group). Main Outcomes and Measures The primary outcome was measured with the 8-point Extended Glasgow Outcome Scale (1 indicates death and 8 denotes upper good recovery), and the 6- to 24-month outcome trajectory was examined. Results This study enrolled 408 patients: 206 in the surgical group and 202 in the medical group. The mean (SD) age was 32.3 (13.2) and 34.8 (13.7) years, respectively, and the study population was predominantly male (165 [81.7%] and 156 [80.0%], respectively). At 24 months, patients in the surgical group had reduced mortality (61 [33.5%] vs 94 [54.0%]; absolute difference, −20.5 [95% CI, −30.8 to −10.2]) and higher rates of vegetative state (absolute difference, 4.3 [95% CI, 0.0 to 8.6]), lower or upper moderate disability (4.7 [−0.9 to 10.3] vs 2.8 [−4.2 to 9.8]), and lower or upper severe disability (2.2 [−5.4 to 9.8] vs 6.5 [1.8 to 11.2]; χ27 = 24.20, P = .001). For every 100 individuals treated surgically, 21 additional patients survived at 24 months; 4 were in a vegetative state, 2 had lower and 7 had upper severe disability, and 5 had lower and 3 had upper moderate disability, respectively. Rates of lower and upper good recovery were similar for the surgical and medical groups (20 [11.0%] vs 19 [10.9%]), and significant differences in net improvement (≥1 grade) were observed between 6 and 24 months (55 [30.0%] vs 25 [14.0%]; χ22 = 13.27, P = .001). Conclusions and Relevance At 24 months, patients with surgically treated posttraumatic refractory intracranial hypertension had a sustained reduction in mortality and higher rates of vegetative state, severe disability, and moderate disability. Patients in the surgical group were more likely to improve over time vs patients in the medical group