An intercomparison experiment involving 15 commonly used detection and tracking algorithms for extratropical cyclones reveals those cyclone characteristics that are robust between different schemes and those that differ markedly.

Factors directly or indirectly related to farming as parental occupation decrease the risk of children becoming atopic and developing symptoms of allergic rhinitis.

A B S T R A C T By way of introduction to the TELLUS thematic cluster on outcomes of the IMILAST project (Intercomparison of MId-LAtitude STorm diagnostics), this paper presents the results of new research that is fundamental for the correct interpretation of IMILAST results. Specifically we investigated the mesoscale structure of cyclonic windstorms, and the representation of those windstorms in re-analysis data. The paper concludes with an overview of the project itself. Twenty-nine historic windstorms are studied in detail, using wide-ranging observational data, and on this basis a conceptual model of the life cycle of a typical windstorm-generating cyclone is developed. The model delineates three wind phenomena, the warm jet, the sting jet and the cold jet, and maps out the typical damage footprint left by each. Focussing on the boundary layer, the physical processes at work in each jet zone are investigated. These include the impact of near-surface stability and exposure on gust strength. Based on numerous cases, a generic description of the sting jet is provided, with many new features highlighted. This phenomenon looks to be unique in that exceptional gusts can be realised well inland because destabilisation is activated from above. We next investigate how well the widely-referenced ERA-Interim re-analysis, that has been a primary data source for IMILAST, can represent windstorms. In many ways, performance is suboptimal. Compared to a benchmark manually-analysed dataset, windstorm-generating cyclones generally do not deepen rapidly enough. In part, this is a resolution limitation. For one medium-sized cyclone, it is shown, using other models, that horizontal resolution of order 20 km or better is required to capture the most damaging winds. In the context of IMILAST, which has used data at resolutions ]80 km, this is a fundamental result. For this and other reasons, caution is clearly needed when inferring storm behaviour and severity from model-based metrics.

Prevalence rates of childhood asthma and allergy have been on the increase for several decades. The present study investigated whether this trend continued during the 1990s in adolescents living in Switzerland.Between 1992 and 2000, the change in prevalence of specific immunoglobulin E to aeroallergens, asthma symptoms and hay fever symptoms assessed by parents9 and students9 answers to the International Study of Asthma and Allergies in Childhood questions was investigated using three cross-sectional surveys. In total 1,324 (74.9%), 1,668 (80.6%) and 1,250 (73.9%) adolescents participated.Prevalence rates of asthma and current asthmatic symptoms remained constant, irrespective of whether the assessment was based on parental questionnaires or the student9s self-completed written or video questionnaires (students9 report of current wheeze 8.8, 7.3, and 8.3%). Similarly, no further increase was observed for reported hay fever rates and allergic sensitisation rates (positive multiscreen allergy test, SX1-test: 34.6, 38.9, and 35.6%, respectively). Although time trends in the occurrence of a series of known risk factors were recorded, none of these factors had a significant impact on asthma and allergy prevalence over time.No further increase in asthma and allergy rates occurred during the 1990s in adolescents living in Switzerland. However, to adequately assess the trend a longer period of observation is needed.