Articles | Volume 10, issue 10
Atmos. Meas. Tech., 10, 3963–3983, 2017
Atmos. Meas. Tech., 10, 3963–3983, 2017

Research article 25 Oct 2017

Research article | 25 Oct 2017

Assessment of mixed-layer height estimation from single-wavelength ceilometer profiles

Travis N. Knepp1,2, James J. Szykman3,4, Russell Long3, Rachelle M. Duvall3, Jonathan Krug3, Melinda Beaver3, Kevin Cavender3, Keith Kronmiller5, Michael Wheeler5, Ruben Delgado6, Raymond Hoff6, Timothy Berkoff2, Erik Olson7, Richard Clark8, Daniel Wolfe9, David Van Gilst10, and Doreen Neil2 Travis N. Knepp et al.
  • 1Science Systems and Applications Inc., Hampton, Virginia 23666, USA
  • 2NASA Langley Research Center, Hampton, Virginia 23681, USA
  • 3US EPA, Research Triangle Park, Durham, North Carolina 27709, USA
  • 4Currently assigned to NASA Langley Research Center, Hampton, Virginia 23681, USA
  • 5Jacobs Technology Inc., Tullahoma, Tennessee 37388, USA
  • 6Joint Center for Earth Systems Technology, University of Maryland Baltimore County, Baltimore, Maryland 21250, USA
  • 7Space Science and Engineering Center, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
  • 8Department of Earth Sciences, Millersville University, Millersville, Pennsylvania 17551, USA
  • 9NOAA/ESRL Physical Sciences Division, Boulder, Colorado 80305, USA
  • 10National Suborbital Education and Research Center, University of North Dakota, Grand Forks, North Dakota 58202, USA

Abstract. Differing boundary/mixed-layer height measurement methods were assessed in moderately polluted and clean environments, with a focus on the Vaisala CL51 ceilometer. This intercomparison was performed as part of ongoing measurements at the Chemistry And Physics of the Atmospheric Boundary Layer Experiment (CAPABLE) site in Hampton, Virginia and during the 2014 Deriving Information on Surface Conditions from Column and Vertically Resolved Observations Relevant to Air Quality (DISCOVER-AQ) field campaign that took place in and around Denver, Colorado. We analyzed CL51 data that were collected via two different methods (BLView software, which applied correction factors, and simple terminal emulation logging) to determine the impact of data collection methodology. Further, we evaluated the STRucture of the ATmosphere (STRAT) algorithm as an open-source alternative to BLView (note that the current work presents an evaluation of the BLView and STRAT algorithms and does not intend to act as a validation of either). Filtering criteria were defined according to the change in mixed-layer height (MLH) distributions for each instrument and algorithm and were applied throughout the analysis to remove high-frequency fluctuations from the MLH retrievals. Of primary interest was determining how the different data-collection methodologies and algorithms compare to each other and to radiosonde-derived boundary-layer heights when deployed as part of a larger instrument network. We determined that data-collection methodology is not as important as the processing algorithm and that much of the algorithm differences might be driven by impacts of local meteorology and precipitation events that pose algorithm difficulties. The results of this study show that a common processing algorithm is necessary for light detection and ranging (lidar)-based MLH intercomparisons and ceilometer-network operation, and that sonde-derived boundary layer heights are higher (10–15 % at midday) than lidar-derived mixed-layer heights. We show that averaging the retrieved MLH to 1 h resolution (an appropriate timescale for a priori data model initialization) significantly improved the correlation between differing instruments and differing algorithms.

Short summary
Herein we compare the mixed-layer data products from differing ceilometer instruments and meteorological sondes.