Modulation of the sea‐surface temperature in the Southeast Pacific by the atmospheric low‐level coastal jet

Abstract

The atmospheric low‐level coastal jet (LLCJ) in the Southeast Pacific (SEP) region is characterized as either a strong‐forcing jet (colder and drier air) or weak‐forcing jet (warm and moist) based on the location of the Southeast Pacific high‐pressure system (SEPH). The sea‐surface temperature (SST) changes corresponding to a particularly strong‐forcing jet (29–30 October) and weak‐forcing jet (22–23 November) are investigated in this study using the two‐way air‐ocean coupled model COAMPS® and satellite observation data. Results indicate that the coupled simulation reduces the overall absolute bias 50% for the surface wind speed, 70% for the cloud liquid water path, and 15% for SST as compared to the uncoupled simulation. The coupled simulation reduces excessive SST cooling, especially during the strong‐forcing jet period along the coastal area where offshore transport of upwelled cold water is too strong from the uncoupled simulation. The coupled simulation also reduces the excessive warming from the uncoupled simulation by providing better cloud coverage. The prominent mechanisms in cooling SST along the coast are the same for both the strong‐forcing and weak‐forcing jets, namely vigorous upwelling and horizontal advection. However, the mechanisms along the jet path differ from along the coast, with air‐sea heat exchange the most important process, resulting in cooling SST during the strong‐forcing jet period but warming SST during the weak‐forcing jet period. The advances and differences of the present study as compared with previous studies are discussed in detail in the paper.