An Overview of Low‐Level Jet Winds and Corresponding Mixed Layer Depths During PECAN
Loading...
Author/Creator
Author/Creator ORCID
Date
2019-08-09
Type of Work
Department
Program
Citation of Original Publication
Carroll, Brian J.; Demoz, Belay B.; Delgado, Ruben; An Overview of Low‐Level Jet Winds and Corresponding Mixed Layer Depths During PECAN; Journals of geophysical Researches: Atmospheres 124,16; https://doi.org/10.1029/2019JD030658
Rights
This item is likely protected under Title 17 of the U.S. Copyright Law. Unless on a Creative Commons license, for uses protected by Copyright Law, contact the copyright holder or the author.
©2018. American Geophysical Union. All Rights Reserved.
Access to this item will begin on 2020-02-09
©2018. American Geophysical Union. All Rights Reserved.
Access to this item will begin on 2020-02-09
Abstract
Thirty southerly low‐level jet (LLJ) events were observed during the Plains Elevated Convection at Night (PECAN) field campaign in the Great Plains region of the United States during summer 2015. Here we present Doppler lidar wind data from three PECAN instrumentation sites to explore characteristics of LLJs and the boundary layer as well as some of the heterogeneities possible within the wind field of a LLJ. Southerly LLJs were observed on 66% of nights at the southwestern site (Greensburg, KS) but only 56% and 53% of nights at the eastern and northern sites, respectively (Hesston and Ellis, KS). The northernmost site had a relative abundance of weaker jets or nonjet conditions due to fronts or convective systems that only affected part of the observation domain. Plotting mean wind fields of each LLJ type reveals that the strongest LLJs tend to develop under very similar conditions but begin to show variability in wind profile evolution after several hours. A robust mixed layer height retrieval algorithm is used to investigate the interplay between the jets and the turbulent convective boundary layer, showing that stronger LLJs are preceded by deeper afternoon mixed layers and often have a later decoupling of mixing between the upper convective mixed layer and the near‐surface layer. Only the strongest LLJs generated a shallow mixing layer overnight. Comparing jet strength and direction to pristine nocturnal convection initiation shows that the strongest southerly LLJs yielded the most pristine nocturnal convection initiation events per night, and the pristine nocturnal convection initiation occurred farther north.