L'activité dépressionnaire et anticyclonique hivernale des moyennes latitudes du Pacifique Nord

• Main Author: Favre, Alice
• Other Authors: Centre de Recherches de Climatologie (CRC), Université de Bourgogne (UB)-Centre National de la Recherche Scientifique (CNRS), Université de Bourgogne, Pierre Camberlin, Yves Richard
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2007
• Subjects: Anticyclones; Pacifique; Climatologie; Température; Précipitations; Variabilité; Amérique du Nord; Changement climatique; Dépressions barométriques; [SDU.STU.CL]Sciences of the Universe [physics]/Earth Sciences/Climatology; [SHS.GEO]Humanities and Social Sciences/Geography; Pacific; aleutian low; Alaska
• Online Access: https://theses.hal.science/tel-00454118; https://theses.hal.science/tel-00454118/document; https://theses.hal.science/tel-00454118/file/These_AliceFavre.pdf

Using a new automated scheme, synoptic mid-latitudes cyclone and anticyclone trajectories have been constructed over the North Pacific from daily sea level pressure (SLP) data, covering the period 1950-2001. Over the North-Eastern Pacific, the strength of anticyclones diminished and their frequency became more variable, while cyclones intensified and presented further southerly trajectories since the mid-1970s. Thus, cyclonic and anticyclonic activities are significantly anti-correlated. These transient activity changes averaged out into anomalously low winter mean SLP in the Aleutian Low region, consistent with the positive phase of the North Pacific Oscillation, inducing positive sea surface temperature (SST) anomalies along the west coast of North America and negative in the central North Pacific Ocean. These conditions are associated with warmer air temperatures and more precipitation from Alaska to Mexico as well as over Southwestern United States in general.According to the Centre National de Recherches Météorologiques Coupled global climate Model version 3 (CNRM-CM3) simulations, the enhanced of greenhouse gases could significantly reduce the frequency of mid-latitude cyclones. These modifications could favor anticyclonic conditions over the East, reducing the anthropogenic warming along the west coast of North America and decreasing / increasing precipitation to the south / north of 45°N respectively. En utilisant un nouveau schéma automatique, les trajectoires des dépressions et des anticyclones synoptiques des moyennes latitudes du Pacifique Nord ont été construites à partir des données de la pression au niveau de la mer journalière (PNM) sur la période 1950-2001 Sur l'Est du Pacifique Nord, la force des anticyclones diminue et leur fréquence devient plus variable, pendant que les dépressions s'intensifient et présentent des trajectoires plus méridionales à partir du milieu des années 70. Ainsi, l'activité dépressionnaire et anticyclonique hivernales sont significativement anti-corrélées. Ces ...