Yueh-Chen Wang1, Sheng-Hsiang Wang  1,2, Jasper R. Lewis3, Shuenn-Chin Chang4,5, Stephen M. Griffith1

1 Department of Atmospheric Sciences, National Central University, Taoyuan, Taiwan
2 Center for Environmental Monitoring and Technology, National Central University, Taoyuan, Taiwan
3 University of Maryland Baltimore County, Maryland, USA
4 Environmental Protection Administration, Taipei, Taiwan
5 School of Public Health, National Defense Medical Center, Taipei, Taiwan


Received: June 21, 2020
Revised: December 31, 2020
Accepted: December 31, 2020

 Copyright The Author(s). This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are cited.


Download Citation: ||https://doi.org/10.4209/aaqr.200336  

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Cite this article:

Wang, Y.C., Wang, S.H., Lewis, J.R., Chang, S.C., Griffith, S.M. (2021). Determining Planetary Boundary Layer Height by Micro-pulse Lidar with Validation by UAV Measurements. Aerosol Air Qual. Res. 21, 200336. https://doi.org/10.4209/aaqr.200336


HIGHLIGHTS

  • Use the volume depolarization ratio from MPL observations to determine PBLHs.
  • Use a series of methods to retrieve the PBLH in northern Taiwan during summer time.
  • A combination of PBLH determination methods can better describe the PBLH evolution.
  • The hybrid image processing technique shows good performance of retrieving PBLHs.
  • The UAV measurements bring a new idea in the validation methods.
 

ABSTRACT


Planetary boundary layer height (PBLH) is often used to characterize the structure of the lower atmosphere. Aerosol lidar, a ground-based remote sensing method, provides the vertical distribution of aerosol at a high temporal resolution observation data, from which, the PBL structure and the position of the PBL top can be comprehensively studied. PBLH determination with lidar data depends primarily on the characteristic turbulent motions in the atmosphere and the geophysical location. However, lidar determination of PBLH over densely populated subtropical locations has rarely been discussed; thus, developing retrieval techniques suitable to these areas is necessary. In this study, four PBLH determination methods (Gradient, δ–threshold, Haar wavelet transform, and hybrid image processing) are applied to estimate the PBLH from lidar observations over an urban area in East Asia, and one—the Gradient method—relied on potential temperature measurements from an unmanned aerial vehicle (UAV) flights to validate our results. Our results indicate that a combination of the gradient method and δ-threshold method can provide better results, in terms of diurnal pattern, than using either method individually. Furthermore, the Haar wavelet and the Hybrid image processing can detect the PBL development comparably well, but both methods are dependent on their initial conditions and optimized algorithm settings. In addition, the accompanying UAV observations are conclusively shown to have a high degree of efficacy for validating the lidar data. This research highlights that a combination of PBLH determination methods can better describe the PBLH evolution throughout a day in some cases, while in others less common determination methods are proving useful, and a suite of retrieval methods should still be explored for precisely mapping the PBL in densely populated subtropical areas.


Keywords: Micro-pulse lidar (MPL), Unmanned aerial vehicle (UAV), Planetary boundary layer (PBL)




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