Recent changes in the low-level jet along the subtropical west coast of South America

Abstract

Surface winds along the subtropical west coast of South America are characterized by the quasi-weekly occurrences of low-level jet events. These short lived but intense wind events impact the coastal ocean environment. Hence, identifying long-term trends in the coastal low-level jet (CLLJ) is essential for understanding changes in marine ecosystems. Here we use ERA5 reanalysis (1979-2019) and an objective algorithm to track anticyclones to investigate recent changes in CLLJ events off central Chile (25-43 degrees S). Results present evidence that the number of days with intense wind (>= 10 ms(-1)), and the number and duration of CLLJ events have significantly changed off central Chile in recent decades. There is an increase in the number of CLLJ events in the whole study area during winter (June-July-August; JJA), while during summer (December-January-February; DJF) a decrease is observed at lower latitudes (29-34 degrees S), and an increase is found at the southern boundary of the Humboldt system. We suggest that changes in the central pressures and frequency of extratropical, migratory anticyclones that reach the coast of South America, which force CLLJs, have played an important role in the recent CLLJ changes observed in this region.