Use of airborne lidar for boundary layer entrainment zone observations

Entrainment processes in the cloud-topped convective boundary layer are known to lead to boundary layer heating, most often drying, and changing concentrations of constituent gases and particles. However, such entrainment processes are notoriously difficult to observe and to accurately simulate. During lake effect snow events, the clouds fill the upper layers of the convective boundary layer; therefore, it might be anticipated that entrainment processes could have large impacts on lake effect formation and snowfall production overall. Using data taken during the Ontario Winter Lake Effect Systems (OWLeS) project provided by the University of Wyoming Cloud LIDAR (WCL) on 17 intensive operations periods (IOPs), we have documented spatial variations in the top of the lake-effect clouds, indicative of the boundary layer top, over Lake Ontario and surrounding land areas. The WCL cannot penetrate thick lake effect clouds, resulting in a thin layer of high backscatter with markedly lower backscatter values below. The backscatter variability is used to determine how cloud tops vary spatially along the flight leg, which gives an idea of the depth of the entrainment zone. 264 one-minute observations of the boundary layer top observations were identified when the UWKA flew mostly horizontal above the lake-effect cloud top. For each, average boundary layer top height and its variability have been calculated, with the intent of relating these factors to environmental conditions within and above the entrainment zone. Results indicate that the boundary layer top behaves much like is expected for convective boundary layers (CBL). Surprisingly, the lake effect cloud tops only penetrate the base of the entrainment zone.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Atmospheric Sciences

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Sagrestano, Sophia Mary

Contributors dc:contributor

• Kristovich, David
• Dominguez, Francina
• Lasher-Trapp, Sonia
• Bhimireddy, Sudheer Reddy

• Boundary Layer
• Entrainment
• Lake-effect
• Lidar Meteorology
• Remote Sensing

Statement dc:rights

• Copyright 2023 Sophia Sagrestano

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/121534

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F121534