Detection and climatology of fronts in a high‐resolution model reanalysis over the Alps

Jenkner, Johannes; Sprenger, Michael; Schwenk, I.; Schwierz, Cornelia; Dierer, Silke; Leuenberger, Daniel

doi:10.1002/met.142

Cited by 86 publications

(122 citation statements)

References 58 publications

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“…Following earlier studies [ Renard and Clarke , ; Clarke and Renard , ; Hewson , ; Jenkner et al ., ; Berry et al ., ; Schemm et al ., ], fronts are identified at the 850 hPa level using the thermal front parameter. This parameter is defined as

normalT normalF normalP = prefix- \nabla (||, \nabla θ_{e}) \cdot \nabla θ_{e} true/ (||, \nabla θ_{e})

…”

Section: Methods: Detection Of Large‐scale Mobile Fronts and Attributmentioning

confidence: 50%

Increase in the number of extremely strong fronts over Europe? A study based on ERA‐Interim reanalysis (1979–2014)

Schemm

Sprenger

Martius

et al. 2017

Geophysical Research Letters

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Evidence is presented that the frequency of extremely strong fronts, which occur mainly in summer, has increased over Europe in ERA‐Interim reanalyses data (1979–2014). Fronts are defined using a common detection scheme based on gradients of equivalent potential temperature (θe) at 850 hPa. The frequency increase is due to increasing atmospheric humidity, which in turn is reported as statistically significant over Europe in the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC AR5). There is no trend in the frequency of extremely strong fronts in North America where humidity trends are, according to the IPCC AR5, close to zero. Because frontal precipitation increases with frontal strength, measured by the θe gradient, the increase in the number of extremely strong fronts may help explain regional patterns of longer‐term trends in strong precipitation events.

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normalT normalF normalP = prefix- \nabla (||, \nabla θ_{e}) \cdot \nabla θ_{e} true/ (||, \nabla θ_{e})

…”

Section: Methods: Detection Of Large‐scale Mobile Fronts and Attributmentioning

confidence: 50%

Increase in the number of extremely strong fronts over Europe? A study based on ERA‐Interim reanalysis (1979–2014)

Schemm

Sprenger

Martius

et al. 2017

Geophysical Research Letters

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“…The high proportion of frontal precipitation highlights the importance of the fronts to the hydrological cycle around Japan. Because several studies have used an objective front detection method in analyses of front frequency and frontal precipitation [ Berry et al , ; Catto et al , ; Simmonds et al , ], and the objective detection method is usually tuned against the weather chart [ Hewson, ; Jenkner et al , ; Berry et al , ], investigating the spatiotemporal characteristics of fronts based on a weather chart can provide useful information for studies using an objective front detection method. Furthermore, the analysis of an occluded front based on a weather chart is also important because an occluded front cannot be detected by the existing objective detection method.The composite distribution of the precipitation relative to front location and structure is investigated.…”

Section: Summary and Concluding Remarksmentioning

confidence: 99%

Climatological characteristics of fronts in the western North Pacific based on surface weather charts

et al. 2014

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Composite front climatology in the western North Pacific is determined using a newly developed 1.0°gridded data set. Here we propose a research strategy for determining the spatiotemporal distribution of fronts using weather chart images published by the Japan Meteorological Agency, one of the major data providers in the region. A preliminarily investigation of the internal data characteristics for the period of 2000-2010 is undertaken, and the final 4 years of data are used for an analysis of front climatology to avoid the effect of any spurious trends. This enables in-depth analyses to be conducted, which have not previously been possible in the region, including the composites of cross-sectional patterns for the thermal fields and precipitation near fronts, front length seasonality, and the significance of the thermal gradient near the fronts, in addition to determining the frontal frequency and spatial distribution of frontal precipitation. Pixel-wise analysis reveals that 56% of the local precipitation maximum is located on the warm side of a cold front caused by less tilted upward motion on the warm side, with the intrusion of the upper level cold dry air into the warm side. This new data set also enables a further analysis of the occluded fronts, which are not correctly distinguished in the existing objective detection method.

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“…In this study, we extend the case studies cited above that focused on a limited number of cases (Ogura and Portis, ; Heymsfield and Schotz, ; Doswell, ; Locatelli et al , ; Neiman and Wakimoto, ) by investigating a larger sample of hail events (∼14 000) that occurred in Switzerland and adjacent regions during the extended hail season between 2002 and 2013. The main objectives of this study are: To apply an automated front recognition algorithm to an analysis data set with high spatial and temporal resolution (Steppler et al , ; Jenkner et al , ). The front algorithm and radar‐based hail detection are discussed in Section 3; the front frequency for Switzerland is presented in Section 4. To link the front data to a radar‐based data set of hail initiations, defined as the time when hail is first detected in a thunderstorm cell by the radar , and to quantify the fraction of pre‐frontal hail formations in different regions of Switzerland (Section 5).…”

Section: Outline and Objectivesmentioning

confidence: 99%

On the link between cold fronts and hail in Switzerland

Schemm

Nisi

Martinov

et al. 2016

Atmospheric Science Letters

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Hail is the costliest atmospheric hazard in Switzerland, causing substantial damage to agriculture, cars and buildings every year. In this study, a 12-year statistic of objectively identified cold fronts and a radar-based hail statistic are combined to investigate the co-occurrence of cold fronts and hail in Switzerland. In a first step, an automated front identification scheme, which has previously been designed for and applied to global reanalysis data, is modified for a high-resolution regional analysis data set. This front detection method is then adapted, tested and applied to the Consortium for Small Scale Modelling (COSMO) analysis data for the extended hail season (May to September) in the years 2002-2013. The resulting cold front statistic is presented and discussed. In a second step, the frequency of cold fronts is linked to a high-resolution radar-based hail statistic to determine the relative fraction of hail initiation events in pre-frontal environments. Up to 45% of all detected hail events in north-eastern and southern Switzerland form in pre-frontal zones. Similar fractions are identified upstream of the Jura and the Black Forest mountains. The percentage of front-related hail formation is highest in regions where hail is statistically less frequent, with the exception of southern Switzerland. Furthermore, it is shown that fronts create wind-sheared environments, which are favourable for hail cells.

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Detection and climatology of fronts in a high‐resolution model reanalysis over the Alps

Cited by 86 publications

References 58 publications

Increase in the number of extremely strong fronts over Europe? A study based on ERA‐Interim reanalysis (1979–2014)

Increase in the number of extremely strong fronts over Europe? A study based on ERA‐Interim reanalysis (1979–2014)

Climatological characteristics of fronts in the western North Pacific based on surface weather charts

On the link between cold fronts and hail in Switzerland

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