Climatology

Low-Level Jet Climatology

Low-level jets (LLJs) are streams of fast-moving air in the lower atmosphere. LLJs are particularly frequent in the central United States where they significantly impact the regional climatology. Southerly LLJs are responsible for the advection of warm, moist air from the Gulf of Mexico and the creation of low-level convergence that can lead to the formation of thunderstorms. Northerly LLJs, on the other hand, influence the regional climate through the advection of colder, drier air. They have been linked to adverse weather conditions, such as wintertime blizzards and the development and spread of large wildfires. LLJs from all directions are factors in the transport of pollutants and insect pests.

In spite of the significance of LLJs to the regional climate of the central United States, a long-term, comprehensive climatology of LLJs does not exist for this area. In addition, the synoptic environments that contribute to the formation of northerly LLJs are poorly understood. The goals of this research project funded by the National Science Foundation are to:

1. assess the quality of the wind observations from the United States rawinsonde network and determine their suitability for climatological investigations of low-level and upper-level wind maxima,
2. prepare a long-term (40-year) climatology of southerly and northerly LLJs for the central United States,
3. evaluate the interannual and intra-annual variability of LLJs in the central United States, particularly any associations to atmospheric teleconnections,
4. identify the spatial patterns and synoptic settings of LLJs from northerly compass directions, and
5. investigate the relationships between LLJs and airstreams within mid-latitude cyclones.