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Atmospheric temperature variability and its response to climate change 

The atmospheric temperature distribution is typically described by its mean and variance, while higher order moments, such as skewness and kurtosis, have received less attention. Skewness is a measure of the asymmetry between the positive and negative tails of the distribution, while kurtosis is indicative of the ”extremity” of the tails. Applying a dynamical approach we study what controls the spatial structure of the near-surface temperature distribution and its response to climate change.

The 850hPa temperature field from ERA-Interim Reanalysis data. Black (white) dots denote the positive (negative) temperature anomalies

Rossby Wave Breaking and its relation to surface weather

Rossby Wave Breaking (RWB) events describe the last stage in the life-cycle of baroclinic atmospheric disturbances. These breaking events can strongly influence the large-scale circulation and are also related to weather extremes such as heat waves, blockings, and extreme precipitation events. Nonetheless, a complete understanding of the synoptic-scale dynamics involved with the breaking events is still absent. Here we take a new approach to study the RWBs and their fundamental relation to weather systems by combining a storm-tracking technique and a RWB detection algorithm. The synoptic-scale dynamics involved with RWBs is examined by analyzing time evolution composites of cyclones and anticyclones during Cyclonic Wave Breaking (CWB) and Anticyclonic Wave Breaking (AWB) events. A better understanding of the different life-cycles of real-atmosphere weather systems is important for exploring the relation between storm-tracks and slowly varying weather regimes and how it is mediated by RWB events.

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A Lagrangian approach to storm tracks

The storm tracks are traditionally defined in either one of the following ways: using an Eulerian approach, as regions of enhanced transient eddy kinetic energy (EKE), obtained using a bandpass time filter with a typical 3–10-day period; or alternatively, using an ensemble of Lagrangian feature tracking of the storms. The latter identifies the storms, tracks them Lagrangially and then analyzes their statistical distributions. The feature-tracking technique gives information about what type of systems, cyclones or anticyclones, compose the statistics of the eddy activity. We use the Lagrangian approach to study mechanisms that control the formation, intensity, and spatial distribution of the storm tracks. This was found useful for explaining the poleward motions of cyclones, the poleward deflection of the localized storm tracks in the northern hemisphere, and the projected poleward shift of the storm tracks under climate change.

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