Preprints
https://doi.org/10.5194/amt-2021-68
https://doi.org/10.5194/amt-2021-68

  14 Jun 2021

14 Jun 2021

Review status: this preprint is currently under review for the journal AMT.

Low-level buoyancy as a tool to understand boundary layer transitions

Francesca M. Lappin1,2, Tyler M. Bell1,2,3,5, Elizabeth A. Pillar-Little1,2, and Phillip B. Chilson1,2,4 Francesca M. Lappin et al.
  • 1School of Meteorology, University of Oklahoma, Norman, OK, USA
  • 2Center for Autonomous Sensing and Sampling, Norman, OK, USA
  • 3Cooperative Institute for Mesoscale Meteorology, Norman, OK, USA
  • 4University of Oklahoma Advanced Radar Research Center, Norman, OK, USA
  • 5NOAA/OAR National Severe Storms Laboratory, Norman, OK, USA

Abstract. Advancements in remotely piloted aircraft systems (RPAS) introduced a new way to observe the atmospheric boundary layer (ABL). Adequate sampling of the lower atmosphere is key to improving numerical weather models and understanding fine-scale processes. The ABL’s sensitivity to changes in surface fluxes leads to rapid changes in thermodynamic variables. This study proposes using low-level buoyancy to characterize ABL transitions. Previously, buoyancy has been used as a bulk parameter to quantify stability. Higher resolution data from RPAS highlight buoyancy fluctuations. RPAS profiles from two field campaigns are used to assess the evolution of buoyancy under convective and stable boundary layers. Data from these campaigns included challenging events to forecast accurately, such as convective initiation and a low-level jet. Throughout the daily ABL transition, results show that the ABL height determined by the minimum in vertical buoyancy gradient agrees well with proven ABL height metrics, such as potential temperature gradient maxima. Moreover, in the cases presented, low-level buoyancy rapidly increases prior to convective initiation and rapidly decreases prior to the onset of a low-level jet. Low-level buoyancy is a function sensitive in space and time, and with further analysis could be used as a forecasting tool. This study expounds on the utility of buoyancy in the ABL and offers potential uses for future research.

Francesca M. Lappin et al.

Status: open (extended)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on amt-2021-68', Anonymous Referee #2, 11 Jul 2021 reply

Francesca M. Lappin et al.

Francesca M. Lappin et al.

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Short summary
This study evaluates how a classically defined variable, air parcel buoyancy, can be used to interpret transitions in the atmospheric boundary layer (ABL). To capture the high-resolution variations, remotely piloted aircraft systems are used to collect data in two field campaigns. This paper finds that buoyancy has distinct evolutions prior to low-level jet and convective initiation cases. Additionally, buoyancy mixes well to act as an ABL height indicator comparable to other methods.