Boundary Layer, Urban Meteorology and Land-Surface Processes

Observed Characteristics of Low-Level Jets During the Lower Atmospheric Boundary Layer Experiment

Tim Bonin

School of Meteorology

05 April 2013, 2:00 PM

National Weather Center, Room 5390
120 David L. Boren Blvd.
University of Oklahoma
Norman, OK

Low-level jets (LLJs) frequently develop at night in the southern Great Plains and significantly affect turbulence and momentum profiles within the planetary boundary layer. In the presence of 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 is transported upward. Currently, the discriminating factors between the formation of an "upside-down" boundary layer and the formation of a traditional boundary layer are not well understood.
In this presentation, I will discuss findings from the Lower Atmospheric Boundary Layer Experiment (LABLE), which was conducted by the OU-BLISS team from 18 September to 13 November 2012. For this field project, a sodar, scintillometer, and two Doppler lidars were deployed at the Southern Great Plains Atmospheric Radiation Measurement site to supplement the instrumentation already in place and used during the experiment (Halo Doppler lidar, 60-m instrumented tower, radiometer, radiosondes, etc.). During the campaign period, LLJs with peak winds of 10 m s-1 or higher were observed on 20 nights. Turbulence profiles associated with the LLJs were derived from Doppler lidar vertical velocity measurements. Characteristics of these turbulence profiles, as well as other features associated with the LLJs, will be discussed in this seminar to lend insight to boundary layer structure on nights with LLJs.

Boundary Layer, Urban Meteorology and Land-Surface Processes Seminar Series website