The Panama Low Level Jet: extension, annual cycle and modes of variation

Abstract

The Panama Low Level Jet (PLLJ) is the inter-isthmic jet closest to the equator, whose activation modifies circulation, sea surface temperature and climate in most of the Eastern Tropical Pacific off Colombia. Through the analysis of 26 years (1992-2018) of sea wind data, the extent of the jet and its main frequencies of variability were determined, in addition to its relationship with phenomena of climatic variability. The area of direct influence of the jet was estimated to be 59295.34 km², being located between 4.63° and 9ºN. The PLLJ is activated annually during the boreal summer (December-April) with intense intra-seasonal variability (with frequencies between 1 to 5 months) and inter annual perturbations associated with El Niño Southern Oscillation events. During warm ENSO events, the PLLJ activity last ~ 2 months more (from mid-November to the end of May) and its spatial extent increases southerly reaching ~ 2 ° N. Additionally, during warm ENSO years, there is an extemporaneous activation of PLLJ in the boreal summer, possibly linked to the intensification of the North Trade Winds over the Caribbean basin in the middle of the year and the increase in the north-south pressure gradient through the Panama isthmus during intense El Niño events. The entry of Caribbean winds in unusual seasons changes the climatology of the PLLJ and increasing its influence in the Eastern Tropical Pacific during the ENSO warm phases.