Polar low tracks over the Nordic Seas: a 14-winter climatic analysis

• Published in: Tellus A: Dynamic Meteorology and Oceanography
• Main Authors: Rojo, Maxence, Claud, Chantal, Mallet, Paul-Etienne, Noer, Gunnar, Carleton, Andrew, Vicomte, Marie
• Other Authors: Cultures, Environnements, Arctique, Représentations, Climat (CEARC), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Centre National de la Recherche Scientifique (CNRS), Laboratoire de Météorologie Dynamique (UMR 8539) (LMD), Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL), Observatoire de Versailles Saint-Quentin-en-Yvelines (OVSQ), Norwegian Meteorological Institute Oslo (MET), Earth and Environmental Systems Institute PennState (EESI), Pennsylvania State University (Penn State), Penn State System-Penn State System, Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-École des Ponts ParisTech (ENPC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Département des Géosciences - ENS Paris
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2015
• Subjects: polar low; the Norwegian Sea; the Barents Sea; tracks; weather regime; sea-ice; dual and multiple systems; [SDE]Environmental Sciences; Barents Sea; Greenland; Norwegian Sea; Nordic Seas; Sea ice; Spitsbergen
• Online Access: https://hal.science/hal-01872789; https://doi.org/10.3402/tellusa.v67.24660

International audience To develop a 14-winter (October–April; 1999–2013) climatic description of polar low (PL) occurrence for the Nordic Seas, systems have been tracked using images acquired from the Very High Resolution Radiometer (AVHRR). Also, the dominant PL characteristics – their temporal and spatial distributions, size, lifespan, distance travelled, speed of propagation and directions – have been determined. On average, 14 PL events occur per winter but there is strong inter-annual and intra-seasonal variability. Although systems may form and travel over the whole Nordic Seas, their genesis is enhanced in areas characterised by warm oceanic currents. At the start of the season (October–November), systems mainly form over the Greenland and Norwegian Seas, but further into winter they form increasingly over the Barents Sea. In connection with recent low-ice winters, new areas of PL formation are evident, particularly to the west of Spitsbergen and in the Barents Sea. PL speeds of propagation range between 5 and 13 m/s but are observed to be highly variable among cases and even during the lifespan of individual PLs. To a considerable extent, the direction of movement is controlled by the large-scale flow in the lowest atmospheric layers, but we also observed cyclonic co-rotation of some pairs of PLs due to their influence on the ambient flow. Although these generally move southward or southeastward, a substantial number of PLs have westward and even northward tracks. PLs in the western part of the region average larger than their eastern counterparts. This study also highlights that PLs characteristics and tracks differ according to weather regimes.