Articles | Volume 10, issue 1
Atmos. Meas. Tech., 10, 247–264, 2017

Special issue: Pushing the limits: The eXperimental Planetary boundary layer...

Atmos. Meas. Tech., 10, 247–264, 2017

Research article 23 Jan 2017

Research article | 23 Jan 2017

Evaluation of single and multiple Doppler lidar techniques to measure complex flow during the XPIA field campaign

Aditya Choukulkar1,2, W. Alan Brewer2, Scott P. Sandberg2, Ann Weickmann1,2, Timothy A. Bonin1,2, R. Michael Hardesty1,2, Julie K. Lundquist3,4, Ruben Delgado5, G. Valerio Iungo6, Ryan Ashton6, Mithu Debnath6, Laura Bianco1,7, James M. Wilczak7, Steven Oncley8, and Daniel Wolfe7 Aditya Choukulkar et al.
  • 1Cooperative Institute for Research in Environmental Sciences, Boulder, CO, USA
  • 2Chemical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, USA
  • 3Department of Atmospheric and Oceanic Sciences, University of Colorado Boulder, CO, USA
  • 4National Renewable Energy Laboratory, Golden, CO, USA
  • 5Atmospheric Physics Department, University of Maryland Baltimore County, MD, USA
  • 6Department of Mechanical Engineering, University of Texas at Dallas, Richardson, TX, USA
  • 7Physical Sciences Division, National Oceanic and Atmospheric Administration, Boulder, CO, USA
  • 8National Center for Atmospheric Research, Boulder, CO, USA

Abstract. Accurate three-dimensional information of wind flow fields can be an important tool in not only visualizing complex flow but also understanding the underlying physical processes and improving flow modeling. However, a thorough analysis of the measurement uncertainties is required to properly interpret results. The XPIA (eXperimental Planetary boundary layer Instrumentation Assessment) field campaign conducted at the Boulder Atmospheric Observatory (BAO) in Erie, CO, from 2 March to 31 May 2015 brought together a large suite of in situ and remote sensing measurement platforms to evaluate complex flow measurement strategies.

In this paper, measurement uncertainties for different single and multi-Doppler strategies using simple scan geometries (conical, vertical plane and staring) are investigated. The tradeoffs (such as time–space resolution vs. spatial coverage) among the different measurement techniques are evaluated using co-located measurements made near the BAO tower. Sensitivity of the single-/multi-Doppler measurement uncertainties to averaging period are investigated using the sonic anemometers installed on the BAO tower as the standard reference. Finally, the radiometer measurements are used to partition the measurement periods as a function of atmospheric stability to determine their effect on measurement uncertainty.

It was found that with an increase in spatial coverage and measurement complexity, the uncertainty in the wind measurement also increased. For multi-Doppler techniques, the increase in uncertainty for temporally uncoordinated measurements is possibly due to requiring additional assumptions of stationarity along with horizontal homogeneity and less representative line-of-sight velocity statistics. It was also found that wind speed measurement uncertainty was lower during stable conditions compared to unstable conditions.

Short summary
This paper discusses trade-offs among various wind measurement strategies using scanning Doppler lidars. It is found that the trade-off exists between being able to make highly precise point measurements versus covering large spatial extents. The highest measurement precision is achieved when multiple lidar systems make wind measurements at one point in space, while highest spatial coverage is achieved through using single lidar scanning measurements and using complex retrieval techniques.