Abstract The South American low‐level jet (SALLJ) is a major source of moisture transport to southeastern South America, influencing rainfall, agriculture, and hydropower. While past research emphasized atmospheric controls, we examine the role of antecedent soil moisture in modulating jet dynamics. We focus on strong Chaco jets, a southward‐extended branch of the SALLJ that transport 37.9 Gt of water daily—twice the Amazon River’s discharge. Using reanalysis data, we identify 54 Chaco jet events and categorize them based on antecedent soil moisture over northern Argentina; 63% occur under drier‐than‐normal conditions. Dry soils are associated with enhanced surface sensible heating, lower‐tropospheric warming, and a deepened thermal low, which intensifies the Chaco jet (2.8 times stronger than in wet cases) during the 5 days before its peak. These results highlight the importance of land‐atmosphere interactions in modulating SALLJ dynamics and suggest that antecedent soil moisture information could improve jet forecasts in the region.
Observations from the Little Bunker
Last updated: December 29, 2025 02:12 PM
Atmospheric CO₂
427.9 ppm
+18.1
ppm/year
Atmospheric CH₄
1930.95 ppb
+-3.5
ppb/year
Global Temperature
+1.48 °C
Peak: +1.73°C
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