Errors in mobile mesonet observations of equivalent potential temperature and wind velocity: Results from the Airdata Verification and Integrated Airborne Tempest Experiment (AVIATE)

The Airdata Verification and Integrated Airborne Tempest Experiment (AVIATE), a collaboration involving the Research and Engineering Center for Unmanned Vehicles at the University of Colorado at Boulder, the University of Nebraska – Lincoln, and the NOAA National Severe Storms Laboratory (NSSL), was conducted in June 2013. During AVIATE, multiple transects were made by a NSSL mobile mesonet (NSSL-MM) across thunderstorm gust fronts. These data along with modeled sensor response to step-function airmass changes reveal O(10K) errors in equivalent potential temperature that result from differences in the time constants of the NSSL-MM temperature and humidity sensors. Common practices for “correcting” the hysteresis of the observed relative humidity are found to significantly increase the magnitude and spatiotemporal extent of the errors. Potentially improved correction methods will be discussed in the presentation.

The AVIATE data also reveal a systematic bias in contemporaneous measurements of wind velocity made by the NSSL-MM and a proximity 5-hole probe that is used on the Tempest unmanned aircraft system. In order to conduct this sensor comparison, the 5-hole probe was mounted to the mobile mesonet rack near the position of the mesonet's propeller-vane anemometer. Based on CFD wind tunnel simulations made using the NSSL-MM parent vehicle, the observed systematic bias was determined to be a consequence of the modified airstream over the vehicle. Potential calibration methods will be discussed in the presentation.