Inter-Comparison of Unmanned Aircraft-Borne and Mobile Mesonet Atmospheric Sensors: Results from the Airdata Verification and Integrated Airborne Tempest Experiment

Results from a novel method of evaluating the performance of unmanned aircraft (UA)-borne and mobile mesonet (MM) atmospheric sensors are presented. Conducted as part of the Airdata Verification and Integrated Airborne Tempest Experiment (AVIATE) in June 2013, this inter-comparison has four principal foci. The first is to evaluate the response times of the temperature and humidity sensor packages on the Tempest unmanned aircraft system and the National Severe Storms Laboratory's mobile mesonet (NSSL-MM). The second focus is to assess the behavior of the temperature and humidity sensors in rain. The third focus is to determine the agreement in the absolute and ground-relative (inertial) winds measured by the Tempest and the NSSL-MM. The final focus is to validate simulations of the flow field over the NSSL-MM parent vehicle and thereby assess the impact of flow field modification on the NSSL-MM wind measurements.

The inter-comparison was facilitated by mounting the UA fuselage and a single wing to the NSSL-MM instrument rack such that the wing-mounted temperature/humidity and wind sensors could collect observations contemporaneous with the NSSL-MM sensors and within a nearly identical air stream. By incorporating the fuselage and wing, potential effects of the airframe on the sensors would be included in the observations. Although the NSSL-MM and Tempest-borne sensors could be compared without the NSSL-MM parent vehicle, mounting both systems to the vehicle enabled the investigators to 1) examine sensor sensitivity in a variety of atmospheric phenomena (these phenomena could be “chased”) and 2) examine the impact of the parent vehicle on the airstream within which both sensors resided.

During AVIATE, multiple transects across atmospheric airmass boundaries were executed. Response times of the temperature and humidity sensors were found to be similar but notable differences will be discussed along with the implications of response differences for the characterization of near-surface baroclinicity. The most significant impact of precipitation on the temperature/humidity sensors was observed when the vehicle entered and exited precipitation and therefore this impact is presumed to be a consequence of differences in the relative humidity sensor responses. Analysis of the measured winds along with numerical experiments designed to test hypotheses concerning the impact of the NSSL-MM parent vehicle on the flow field and wind sensors are underway.