MERRA-2 Great Plains Low-level Jet Characteristics and Variability

Great Plains Low-level Jets (GPLLJs) in MERRA-2's 45-year (1980-2024) record have been objectively analyzed and classified according to relative strength of synoptic-scale forcing. We compare our results derived from MERRA-2's 0.5 x 0.625 resolution record with previous results based on reduced resolution reanalyses. The analysis is extended to examine covariability of GPLLJs with other aspects of the climate system. For example, land conditions, including regional soil moisture gradients, can significantly affect low level pressure gradients and heating rates that interact with the atmospheric circulation driving the GPLLJ wind intensities, and hence the transport of atmospheric water vapor into the central United States. While the land condition is a dominant forcing of uncoupled GPLLJs (i.e., those that operate independently of the large-scale mid-upper tropospheric flow), the sensitivity of coupled GPLLJs to different land conditions will also be tested. This analysis will provide a baseline for NASA’s forthcoming reanalysis, MERRA-21C, which will have further model developments and output related to GPLLJs and the planetary boundary layer at increased horizontal and vertical resolution.