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Volume 10, issue 5 | Copyright

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

Atmos. Meas. Tech., 10, 1707-1721, 2017
https://doi.org/10.5194/amt-10-1707-2017
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 09 May 2017

Research article | 09 May 2017

Assessing the accuracy of microwave radiometers and radio acoustic sounding systems for wind energy applications

Laura Bianco1,2, Katja Friedrich3, James M. Wilczak2, Duane Hazen1,2, Daniel Wolfe1,2, Ruben Delgado4, Steven P. Oncley5, and Julie K. Lundquist3,6 Laura Bianco et al.
  • 1Cooperative Institute for Research in Environmental Sciences (CIRES), Boulder, CO, USA
  • 2National Oceanic and Atmospheric Administration, Earth Systems Research Laboratory, Physical Science Division, Boulder, CO, USA
  • 3Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder, CO, USA
  • 4Atmospheric Physics Department, University of Maryland, Baltimore County, Baltimore, MA, USA
  • 5National Center for Atmospheric Research, Boulder, CO, USA
  • 6National Renewable Energy Laboratory, Golden, CO, USA

Abstract. To assess current remote-sensing capabilities for wind energy applications, a remote-sensing system evaluation study, called XPIA (eXperimental Planetary boundary layer Instrument Assessment), was held in the spring of 2015 at NOAA's Boulder Atmospheric Observatory (BAO) facility. Several remote-sensing platforms were evaluated to determine their suitability for the verification and validation processes used to test the accuracy of numerical weather prediction models.

The evaluation of these platforms was performed with respect to well-defined reference systems: the BAO's 300m tower equipped at six levels (50, 100, 150, 200, 250, and 300m) with 12 sonic anemometers and six temperature (T) and relative humidity (RH) sensors; and approximately 60 radiosonde launches.

In this study we first employ these reference measurements to validate temperature profiles retrieved by two co-located microwave radiometers (MWRs) as well as virtual temperature (Tv) measured by co-located wind profiling radars equipped with radio acoustic sounding systems (RASSs). Results indicate a mean absolute error (MAE) in the temperature retrieved by the microwave radiometers below 1.5K in the lowest 5km of the atmosphere and a mean absolute error in the virtual temperature measured by the radio acoustic sounding systems below 0.8K in the layer of the atmosphere covered by these measurements (up to approximately 1.6–2km). We also investigated the benefit of the vertical velocity correction applied to the speed of sound before computing the virtual temperature by the radio acoustic sounding systems. We find that using this correction frequently increases the RASS error, and that it should not be routinely applied to all data.

Water vapor density (WVD) profiles measured by the MWRs were also compared with similar measurements from the soundings, showing the capability of MWRs to follow the vertical profile measured by the sounding and finding a mean absolute error below 0.5gm−3 in the lowest 5km of the atmosphere. However, the relative humidity profiles measured by the microwave radiometer lack the high-resolution details available from radiosonde profiles. An encouraging and significant finding of this study was that the coefficient of determination between the lapse rate measured by the microwave radiometer and the tower measurements over the tower levels between 50 and 300m ranged from 0.76 to 0.91, proving that these remote-sensing instruments can provide accurate information on atmospheric stability conditions in the lower boundary layer.

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XPIA is a study held in 2015 at NOAA's Boulder Atmospheric Observatory facility, aimed at assessing remote-sensing capabilities for wind energy applications. We use well-defined reference systems to validate temperature retrieved by two microwave radiometers (MWRs) and virtual temperature measured by wind profiling radars with radio acoustic sounding systems (RASSs). Water vapor density and relative humidity by the MWRs were also compared with similar measurements from the reference systems.
XPIA is a study held in 2015 at NOAA's Boulder Atmospheric Observatory facility, aimed at...
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