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Atmospheric Measurement Techniques An interactive open-access journal of the European Geosciences Union

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doi:10.5194/amt-2016-321
© Author(s) 2016. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
12 Oct 2016
Review status
A revision of this discussion paper was accepted for the journal Atmospheric Measurement Techniques (AMT) and is expected to appear here in due course.
Assessing the accuracy of microwave radiometers and radio acoustic sounding systems for wind energy applications
Laura Bianco1,2, Katja Friedrich3, James Wilczak2, Duane Hazen1,2, Daniel Wolfe1,2, Ruben Delgado4, Steve Oncley5, and Julie K. Lundquist3,6 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
4University 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 300-m tower equipped at 6 levels (50, 100, 150, 200, 250, and 300 m) with 12 sonic anemometers and 6 temperature and relative humidity 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, as well as virtual temperature measured by co-located wind profiling radars equipped with radio acoustic sounding systems. Results indicate a mean absolute error in the temperature retrieved by the microwave radiometers below 1.5 °C in the lowest 5 km of the atmosphere, and a mean absolute error in the virtual temperature measured by the radio acoustic sounding systems below 0.8 °C in the layer of the atmosphere covered by these measurements (up to approximately 1.6–2 km). We also investigated the benefit of the vertical velocity 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 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 0.5 g m−3 in the lowest 5 km 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 300 m 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.


Citation: Bianco, L., Friedrich, K., Wilczak, J., Hazen, D., Wolfe, D., Delgado, R., Oncley, S., and Lundquist, J. K.: Assessing the accuracy of microwave radiometers and radio acoustic sounding systems for wind energy applications, Atmos. Meas. Tech. Discuss., doi:10.5194/amt-2016-321, in review, 2016.
Laura Bianco et al.
Laura Bianco et al.

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Short summary
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. 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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