Coordinated Unmanned Aircraft System (UAS) and Ground-Based Weather Measurements to Predict Lagrangian Coherent Structures (LCSs).

Peter Nolan,Roger Laurence,Christina Vezzi,James Pinto,Craig Powers,Anders Jensen,Hosein Foroutan,Shane Ross,Constantin Diehl,Javier González-Rocha,Sean Bailey,David Schmale,Gijs De Boer

doi:10.3390/s18124448

Abstract

Concentrations of airborne chemical and biological agents from a hazardous release are not spread uniformly. Instead, there are regions of higher concentration, in part due to local atmospheric flow conditions which can attract agents. We equipped a ground station and two rotary-wing unmanned aircraft systems (UASs) with ultrasonic anemometers. Flights reported here were conducted 10 to 15 m above ground level (AGL) at the Leach Airfield in the San Luis Valley, Colorado as part of the Lower Atmospheric Process Studies at Elevation—a Remotely-Piloted Aircraft Team Experiment (LAPSE-RATE) campaign in 2018. The ultrasonic anemometers were used to collect simultaneous measurements of wind speed, wind direction, and temperature in a fixed triangle pattern; each sensor was located at one apex of a triangle with ∼100 to 200 m on each side, depending on the experiment. A WRF-LES model was used to determine the wind field across the sampling domain. Data from the ground-based sensors and the two UASs were used to detect attracting regions (also known as Lagrangian Coherent Structures, or LCSs), which have the potential to transport high concentrations of agents. This unique framework for detection of high concentration regions is based on estimates of the horizontal wind gradient tensor. To our knowledge, our work represents the first direct measurement of an LCS indicator in the atmosphere using a team of sensors. Our ultimate goal is to use environmental data from swarms of sensors to drive transport models of hazardous agents that can lead to real-time proper decisions regarding rapid emergency responses. The integration of real-time data from unmanned assets, advanced mathematical techniques for transport analysis, and predictive models can help assist in emergency response decisions in the future.

Highlights

Atmospheric wind velocity measurements are critical to air quality [1], weather forecasting [2], and climate studies [3]
We describe the use of multiple unmanned aircraft systems (UASs) equipped with ultrasonic anemometers to measure wind and temperature and forecast Lagrangian coherent structures (LCSs)
Eight coordinated flights (Table 1) were conducted at 15 m above ground level (AGL) in a fixed triangle pattern (Figure 4)

Summary

Introduction

Atmospheric wind velocity measurements are critical to air quality [1], weather forecasting [2], and climate studies [3]. Unmanned aircraft systems (UASs) are an emerging technology for atmospheric wind velocity measurements near the surface of Earth [4] where it is difficult and expensive to operate conventional atmospheric sensors reliably. Small UASs, both fixed- and rotary-wing, are low-cost, mobile, and portable with some trade-offs involving flight characteristics. Fixed-wing UASs can fly for periods of around 45 min continuously, but are limited by their flight envelope to open-space operations for launch, maneuvering, and recovery. Rotary-wing UASs can hover, allowing for operations in complex environments, but have limited battery power and generally have shorter flight periods. Efforts to measure atmospheric properties with UASs began as early as 1971 with [5] using a small fixed-wing platform to carry sensors for direct measurements of atmospheric properties [6]. Similar studies have since followed suit using different mission-specific aircraft designs as detailed in [6]

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