Analysis of Turbulence and Thermodynamics Associated with Low-Level Jets

Low-level jets (LLJs) significantly affect turbulence and momentum profiles within the planetary boundary layer. Under certain conditions with a strong LLJ, an “upside-down” boundary layer may develop in which turbulence is generated above the surface and is transported downward. This contrasts to the traditional boundary layer where turbulence is generated at the surface and transported upward. Currently, the discriminating factors determining whether an “upside-down” or traditional boundary layer will form are not well understood.

In this presentation, findings from the Lower Atmospheric Boundary Layer Experiments (LABLE-I and LABLE-II) will be discussed. For these field projects, several instruments including multiple Doppler lidars were deployed at the Southern Great Plains Atmospheric Radiation Measurement site to supplement the instrumentation already in place. The lidars were generally used to retrieve vertical profiles of wind and turbulence, utilizing dual- and tri-Doppler analysis during LABLE-II. Thermodynamic profiles were continuously retrieved with an Atmospheric Emitted Radiance Interferometer (AERI) to monitor the development and progression of near-surface temperature inversions. The combined use of AERI and lidar data enables a unique investigation of the relationship between nocturnal turbulence and atmospheric stability. Characteristics of turbulence profiles associated with LLJs, including their relation to inversion and shear layers, will be discussed in this presentation.