Hydroclimatic anomalies over Southern Great Plains (SGP), such as pluvial events and dry spells, often result in significant losses to agriculture, food, and water supplies, and cause other environmental damage across the SGP. Improving the sub-seasonal to seasonal (S2S) predictability of these anomalies—including their onset, persistence, severity, frequency, and demise—is crucial for providing timely decision support for early warnings and mitigation strategies.
While previous studies have shown that the North American Monsoon System (NAMS), the Great Plains Low-Level Jet (GPLLJ), and land surface processes each influence warm season precipitation in the SGP, the interactions among these factors and their role in extreme weather events remain unclear. Additionally, the extent to which these events are predictable on an S2S scale is not well understood. This study analyzes warm season precipitation anomalies since 1979, focusing on the impacts of evolution of NAMS and GPLLJ.
Preliminary results suggest that in most pluvial years, an intensified GPLLJ coincides with a stronger NAMS, characterized by a more westward and northward extension of the monsoon high-pressure ridge. Conversely, during years of extreme droughts, the opposite patterns are often observed. The date of NAMS onset also impacts precipitation in the SGP, with an earlier onset typically leading to extreme wet years. However, in some of the years featuring either dry or wet anomalies, no significant changes are observed in either NAMS or GPLLJ, suggesting that other factors, such as land surface processes, may play a dominant role. The ongoing land-atmosphere coupled modeling experiments will provide a deeper insight into the drivers of these extreme events in the SGP and identify potential sources of predictability for these events on the S2S scale.
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