What are the Best Thermodynamic Quantity and Function to Define a Front in Gridded Model Output?

Thomas, Carl M.; Schultz, David M.

doi:10.1175/bams-d-18-0137.1

Cited by 40 publications

(36 citation statements)

References 104 publications

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“…This method for identifying synoptic‐scale features has been tested and validated for all types of front in the Northern Hemisphere (Schemm et al ., ; Schemm and Sprenger, ; Schemm et al ., ). There are other methods that can be used for frontal identification (e.g., Simmonds et al ., ) and also variants in the method applied in this study by using different thermal front parameters (e.g.,

θ

, Thomas and Schultz, ;

θ_{w}

, Berry et al ., ). In Schemm et al .…”

Section: Methodsmentioning

confidence: 99%

The role of secondary cyclones and cyclone families for the North Atlantic storm track and clustering over western Europe

Priestley

Dacre

Shaffrey

et al. 2020

Quart J Royal Meteoro Soc

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Secondary cyclones are those that form in association with a pre-existing primary cyclone, typically along a trailing cold front. In previously studied cases they have been shown to cause extreme damage across Europe, particularly when multiple cyclones track over the same location in rapid succession (known as cyclone clustering). To determine the dynamical relationship between primary and secondary cyclones over the North Atlantic, a frontal identification algorithm is partnered with a cyclone identification method to objectively identify secondary cyclones in 35 extended winter periods using reanalysis data.Cyclones are grouped into "cyclone families" consisting of a single primary cyclone and one or more secondary cyclones. This paper aims to quantify the differences between secondary and primary cyclones over the North Atlantic, and how cyclone families contribute to episodes of cyclone clustering across western Europe. Secondary cyclones are shown to occur most frequently in the central and eastern North Atlantic, whereas primary cyclones are commonly found over the western North Atlantic. Cyclone families have their strongest presence over the North Atlantic Ocean and contribute more than 50% of cyclones over the main North Atlantic storm track. A final category, solo cyclones, which are not associated with cyclogenesis on any connected fronts, are most commonly identified over continental regions as well as the Mediterranean Sea. Primary cyclones are associated with the development of an environment that is favourable for secondary cyclone growth. Enhanced Rossby wave breaking following primary cyclone development leads to an increase in the upper-level jet speed and a decrease in low-level stability. Secondary cyclogenesis commonly occurs in this region of anomalously low stability, close to the European continent. During periods of cyclone clustering, secondary cyclones are responsible for approximately 50% of the total number of cyclones. The increase in jet speed This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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θ

, Thomas and Schultz, ;

θ_{w}

, Berry et al ., ). In Schemm et al .…”

Section: Methodsmentioning

confidence: 99%

The role of secondary cyclones and cyclone families for the North Atlantic storm track and clustering over western Europe

Priestley

Dacre

Shaffrey

et al. 2020

Quart J Royal Meteoro Soc

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“…There is no agreed definition for a front and no standard method for their detection in observations, reanalyses, or models. For a recent review of how fronts are defined and detected see Thomas and Schultz (2019). This subsection explores the sensitivity of the results to some of the definitions, detection methods, and analysis period used here.…”

Section: The Relative Importance Of Convergence Adiabatic and Diabatic Frontogenesismentioning

confidence: 99%

The Effect of Sea Surface Temperature Fronts on Atmospheric Frontogenesis

Reeder

Spengler

Spensberger

2021

Journal of the Atmospheric Sciences

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It is thought that the sensible heat fluxes associated with sea surface temperature (SST) fronts can affect the genesis and evolution of atmospheric fronts. An analytic model is developed and used to explore this idea. The model predictions are compared with climatologies of atmospheric fronts over the North Atlantic Ocean identified in reanalyses. The climatologies are divided into times when fronts are detected at a point and times when they are not, and compared with model results with and without fronts in their initial conditions.In airstreams with fronts, both the climatologies and model show that adiabatic frontogenesis is much more important than diabatic frontogenesis. They also show that there is weak diabatic frontogenesis associated with differential sensible heating over the SST front and frontolysis either side of it. Because of the upstream and downstream frontolysis, the SST front has relatively little net effect on atmospheric fronts in the model. This result holds true as the width and strength of the SST front changes.In airstreams initially without fronts, a combination of adiabatic and diabatic frontogenesis is important for the local genesis of atmospheric fronts over the SST front. The model shows sustained frontogenesis only when the deformation is sufficiently strong or when the translation speed is low, as advection otherwise weakens the potential temperature gradient. This strong localized diabatic frontogenesis, which is amplified by adiabatic frontogenesis, can result in a front, which is consistent with atmospheric fronts in the region being most frequently located along the SST front.

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“…While such methods are in principle objective, choosing specific approaches and configurations involves many ultimately subjective choices. Lacking a universally accepted definition of fronts, it is not inherently clear how to identify them, and consequently, many different approaches exist, as discussed in detail by Schemm et al (2018) and Thomas and Schultz (2019). Another subjective choice is involved when attributing precipitation to a front within a certain distance, which might also depend on the resolution of the available data sets.…”

Section: Introductionmentioning

confidence: 99%

Attribution of precipitation to cyclones and fronts over Europe in a kilometer-scale regional climate simulation

Rüdisühli¹,

Sprenger²,

Leutwyler³

et al. 2020

Preprint

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Abstract. This study presents a detailed analysis of the climatological distribution of precipitation in relation to cyclones and fronts over Europe for the nine-year period 2000–2008. The analysis uses hourly output of a COSMO (Consortium for Small-scale Modeling) model simulation with 2.2 km grid spacing and resolved deep convection. Cyclones and fronts are identified as two-dimensional features in 850 hPa geopotential, equivalent potential temperature, and wind fields, and subsequently tracked over time based on feature overlap and size. Thermal heat lows and local thermal fronts are removed based on track properties. This data set then serves to define seven mutually exclusive precipitation components: high-pressure (e.g., summer convection), cyclonic (near cyclone center), cold-frontal, warm-frontal, collocated (e.g., occlusion area), far-frontal, and residual. The approach is illustrated with two case studies with contrasting precipitation characteristics. The climatological analysis for the nine-year period shows that frontal precipitation peaks in fall and winter over the eastern North Atlantic, with cold frontal precipitation also being crucial year-round near the Alps; cyclonic precipitation is largest over the North Atlantic (especially in summer) and in the northern Mediterranean (except in summer); high-pressure precipitation occurs almost exclusively over land and primarily in summer; and the residual contributions uniformly amount to about 20 % in all seasons. Considering heavy precipitation events (defined based on the local 99.9th percentile) reveals that high-pressure precipitation dominates in summer over the continent; cold fronts produce much more heavy precipitation than warm fronts; and cyclones contribute substantially, especially in the Mediterranean in fall through spring and in Northern Europe in summer.

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What are the Best Thermodynamic Quantity and Function to Define a Front in Gridded Model Output?

Cited by 40 publications

References 104 publications

The role of secondary cyclones and cyclone families for the North Atlantic storm track and clustering over western Europe

The role of secondary cyclones and cyclone families for the North Atlantic storm track and clustering over western Europe

The Effect of Sea Surface Temperature Fronts on Atmospheric Frontogenesis

Attribution of precipitation to cyclones and fronts over Europe in a kilometer-scale regional climate simulation

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