6533b858fe1ef96bd12b60a1

RESEARCH PRODUCT

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

subject

description

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.