How do Low-Level Jets Lead to Precipitation Extremes?

The relationship between low level jets (LLJs) and precipitation extremes (e.g., drought and flooding) in the southern Great Plains Region is investigated. The water years 2006 (a drought year) and 2007 (a flood year) are studied and compared in terms of the distribution, frequency, and characteristics of LLJs and associated precipitation. NCEP North American Regional Reanalysis (NARR), NASA Modern Era Retrospective Analysis for Research and Applications (MERRA), NOAA wind profiler data, and NASA TRMM satellite data products are used. Statistics are calculated for various quantities to relate when and how the LLJs will lead to heavy precipitation events.

It is found that LLJs are more likely to produce heavy precipitation when their source regions are from the Gulf area, when the jets are stronger, or when they occur further south. In addition, it is found that the main difference in the structure of the LLJs between the drought year of 2006 and the flood year of 2007 can be attributed to the strength and placement of the synoptic scale features. The mesoscale and boundary layer processes that contribute to heavy precipitation from LLJs are investigated. Results will be reported during the symposium.