Assessing State-of-the-Art Capabilities for Probing the Atmospheric Boundary Layer: The XPIA Field Campaign

Andrew Clifton, Julie Lundquist, James Wilczak, Ryan Ashton, Laura Bianco, W. Brewer, Aditya Choukulkar, Mithu Debnath, Ruben Delgado, Katja Friedrich, Scott Gunter, Armita Hamidi, Giacomo Iungo, Branko Kosovic, Patrick Langan, Adam Lass, Evan Lavin, Joseph Lee, Robert Newsom, Steven OncleyPaul Quelet, Scott Sandberg, John Schroeder, William Shaw, Lynn Sparling, Clara Martin, Alexander Pé, Edward Strobach, Ken Tay, Brian Vanderwende, Ann Weickmann, Daniel Wolfe, Rochelle Worsnop, Aleya Kaushik, Katherine McCaffrey, David Noone

Research output: Contribution to journalArticlepeer-review

63 Scopus Citations


To assess current capabilities for measuring flow within the atmospheric boundary layer, including within wind farms, the U.S. Dept. of Energy sponsored the eXperimental Planetary boundary layer Instrumentation Assessment (XPIA) campaign at the Boulder Atmospheric Observatory (BAO) in spring 2015. Herein, we summarize the XPIA field experiment, highlight novel measurement approaches, and quantify uncertainties associated with these measurement methods. Line-of-sight velocities measured by scanning lidars and radars exhibit close agreement with tower measurements, despite differences in measurement volumes. Virtual towers of wind measurements, from multiple lidars or radars, also agree well with tower and profiling lidar measurements. Estimates of winds over volumes from scanning lidars and radars are in close agreement, enabling assessment of spatial variability. Strengths of the radar systems used here include high scan rates, large domain coverage, and availability during most precipitation events, but they struggle at times to provide data during periods with limited atmospheric scatterers. In contrast, for the deployment geometry tested here, the lidars have slower scan rates and less range, but provide more data during non-precipitating atmospheric conditions. Microwave radiometers provide temperature profiles with approximately the same uncertainty as Radio-Acoustic Sounding Systems (RASS). Using a motion platform, we assess motion-compensation algorithms for lidars to be mounted on offshore platforms. Finally, we highlight cases for validation of mesoscale or large-eddy simulations, providing information on accessing the archived dataset. We conclude that modern remote sensing systems provide a generational improvement in observational capabilities, enabling resolution of fine-scale processes critical to understanding inhomogeneous boundary-layer flows.
Original languageAmerican English
Pages (from-to)289-314
Number of pages26
JournalBulletin of the American Meteorological Society
Issue number2
StatePublished - 2017

NREL Publication Number

  • NREL/JA-5000-64812


  • atmospheric boundary layer
  • remote sensing
  • technology
  • thermodynamics
  • wind
  • wind energy


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