Mechanisms underlying temperature extremes in Iberia: a Lagrangian perspective ...

• Main Authors: Santos, João A., Pfahl, Stephan, Pinto, Joaquim G., Wernli, Heini
• Format: Article in Journal/Newspaper
• Language: English
• Published: ETH Zurich 2015
• Subjects: Temperature extremes; Cold episodes; Warm episodes; Lagrangian trajectories; Large-scale circulation; Surface fluxes; Iberian Peninsula; ERA-Interim; North Atlantic
• Online Access: https://dx.doi.org/10.3929/ethz-b-000101056; http://hdl.handle.net/20.500.11850/101056

The mechanisms underlying the occurrence of temperature extremes in Iberia are analysed considering a Lagrangian perspective of the atmospheric flow, using 6-hourly ERA-Interim reanalysis data for the years 1979–2012. Daily 2-m minimum temperatures below the 1st percentile and 2-m maximum temperatures above the 99th percentile at each grid point over Iberia are selected separately for winter and summer. Four categories of extremes are analysed using 10-d backward trajectories initialized at the extreme temperature grid points close to the surface: winter cold (WCE) and warm extremes (WWE), and summer cold (SCE) and warm extremes (SWE). Air masses leading to temperature extremes are first transported from the North Atlantic towards Europe for all categories. While there is a clear relation to large-scale circulation patterns in winter, the Iberian thermal low is important in summer. Along the trajectories, air mass characteristics are significantly modified through adiabatic warming (air parcel descent), ... : Tellus A: Dynamic Meteorology and Oceanography, 67 (1) ...