Predicting the Initiation of Convection Using Unmanned Aircraft System Data

The potential for using Low-Altitude, Short Endurance (LASE)-type Unmanned Aircraft Systems (UAS) for predicting Convection Initiation (CI) is explored. An experiment was conducted in Oklahoma in Spring 2017 to test the capabilities of both fixed-wing UAS to measure the spatial heterogeneity of the atmosphere between Oklahoma Mesonet sites, and rotary-wing UAS to obtain frequently sampled profiles of winds, temperature, and humidity within the atmospheric boundary layer with exceedingly high vertical resolution. The accuracy of the UAS measurements was validated against independent observing systems, including ground-based remote sensing systems, instrumented towers, and special rawinsondes. This validation exercise provided needed information about the selected UAS sensor and platform performances outside the laboratory wherein sensor calibration normally occurs. Also, an assessment of the utility of UAS data in real-time operations was conducted in a coordinated activity involving a National Weather Service (NWS) Forecast Office.

Recommendations based on the experimental findings included the required vertical and temporal sampling intervals, the minimum flight altitudes needed for CI forecasting purposes, and logistical considerations. Challenges in obtaining waivers for FAA Certificates of Authorization to fly beyond the nominal 400-ft AGL limit, in conditions Beyond Visual Line-Of-Sight, and multiple UAS operating simultaneously, will be addressed. The future vision is one of targeted, adaptive sampling within preapproved COA regions that would be executed in a semi-autonomous manner by the NWS as needed when severe weather threatens.