Boundary layer temporal evolution observed by doppler lidar upwind of a lake-effect snow event

King, David Raymond

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https://hdl.handle.net/2142/105074 Copy

Description

Title

Boundary layer temporal evolution observed by doppler lidar upwind of a lake-effect snow event

Author(s)

King, David Raymond

Issue Date

2019-04-24

Director of Research (if dissertation) or Advisor (if thesis)

Kristovich, David

Department of Study

Atmospheric Sciences

Discipline

Atmospheric Sciences

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• lake-effect snow
• lidar
• buckingham pi
• snow
• lake michigan

Abstract

A Halo Photonics Doppler Wind LiDAR (LiDAR) was deployed during a lake-effect snow event over Lake Michigan to develop a method of processing and reviewing the data collected by the LiDAR, create a conceptual model of the temporal evolution of the atmospheric boundary layer on the lake’s upwind shore, and investigate its influence on the larger lake-effect snow process. The analysis of the data retrieved by the LiDAR, in conjunction with supporting datasets, will be focused on 8 to 9 December 2016 at locations surrounding Lake Michigan as well as at Illinois Beach State Park in Waukegan, IL, where the LiDAR was stationed. The study utilizes the concept of mass continuity for an idealized turbulent eddy which is used to visualize the planetary boundary layer for a given time period. By applying this concept to the LiDAR dataset, a new method to approximate the depth of the boundary layer using statistical values of vertical motions for each time step of data collection is developed. The approximations made for the top of the boundary layer at specific time intervals were then plotted as a time series. This time series was the skeleton for the final conceptual model which shows a growing convective wintertime boundary layer for each day, with a shallow boundary layer during the night. Additionally, the Buckingham Pi method was utilized to evaluate various parameters hypothesized to influence the boundary layer depth. Buckingham Pi was chosen as an appropriate method as it employs the use of dimensionless analysis which is useful to compare variables that do not have similar units, as was the case for the parameters in this study. The resulting equation attempts to describe the individual proportional relationships between parameters and their influence on the temporal change of boundary layer depth. When data from this case were used to evaluate these relationships, it was found that no individual parameter had a higher order of magnitude than any other for a time period shorter than a day. It was concluded that it cannot be said that one single parameter was responsible for the evolution of the BL more so than another. Lastly, snowfall totals on the downwind shore were recorded at various locations in Western Michigan and Northern Indiana and analyzed. This was undertaken as a first step in an attempt to connect upwind boundary layer depth to snowfall accumulations downwind. Surface stations reported measurements of snowfall on both 8 and 9 December 2016, as well as on 10 December; however, the data was only recorded once a day. This made attributing snowfall to a specific time frame difficult. Without higher temporal resolution snowfall measurements, conclusions drawn are considered hypotheses needing further evaluation.

Graduation Semester

2019-05

Type of Resource

text

Permalink

http://hdl.handle.net/2142/105074

Copyright and License Information

Copyright 2019 David King

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