Boundary Layer Observations with Unmanned Aircraft - Results from the 2016-2018 CLOUD-MAP Flight Campaign

CLOUD-MAP – the Collaboration Leading Operational UAS Development for Meteorology and Atmospheric Physics – is a 4 year, 4 university partnership funded by the National Science Foundation to develop capabilities that will allow meteorologists and atmospheric scientists to use unmanned aircraft as a common, useful everyday tool following recognized needs as outlined in a 2009 US National Research Council Report:

The vertical component of ¼ mesoscale observations is inadequate. Assets required to profile the lower troposphere above the near-surface layer ¼ are too limited in what they measure, too sparsely or unevenly distributed, sometimes too coarse in vertical resolution, sometimes limited to regional areal coverage, and clearly do not qualify as a mesoscale network of national dimensions. Likewise, vertical profiles above the Earth’s surface are inadequately measured in both space and time¼

Unmanned Aircraft Systems (UAS) are a potential solution to this problem as they are well suited for the lower atmosphere, namely the lower boundary layer that has a large impact on the atmosphere and where much of the weather phenomena begin.

The CLOUD-MAP team is examining numerous systems including both fixed wing and rotary wing solutions predominantly focused on atmospheric boundary layer measurements. Multiple field campaigns have been conducted over the 3 years the project has been underway with . In June 2016 over 100 paricipating team members from the 4 partner institutions (Oklahoma State University, the University of Oklahoma, the University of Kentucky, and the University of Nebraska at Lincoln) and other collaborating agencies. Selected sites included the Oklahoma State University Unmanned Aircraft Flight Station, the Marena Mesonet, the Kessler Ecological Field Station, and the US Department of Energy Atmospheric Radiation Monitoring Climate Research Facility Southern Great Plains site. Over multiple periods, the team has conducted thousands of individual flights and logged hundreds of total flight hours focused on gathering comprehensive, accurate, and relevant atmospheric data. Sensors included standard meteorological sensors for pressure, temperature, and relative humidity, various wind sensors such as five-hole probes, hot wire sensors, and IMUs, gas concentration sensors including CO₂ and CH₄, and small inexpensive meteorological packages designed for aerial deployment.

The presentation will discuss results from selected platform and sensor suite flight-testing of various CLOUD-MAP UAS as well as operational and logistical considerations for such a large exercise. The exercises have also designed to evaluate operational considerations of a large, multi-institutional teams and effectiveness of various technological solutions to observe similar quantities. This includes evaluation of sampling techniques and calibration/validation tests for PTU, wind, and gas sampling. For the former, importance of sensor integration is discussed, particularly location on rotary wing aircraft. Likewise, measurement of wind, including turbulence quantities, is an important observation that is oftern difficult to obtain using sUAS. Techniques for wind characterization from both probes and IMUS. For gas sampling, tests were conducted over a controlled release of CO₂ and CH₄ in addition to over controlled rangeland fires which released carbon dioxide over a large area as would be expected from a carbon sequestration source. 3D maps of carbon dioxide were developed from the system telemetry that clearly illustrated increased CO₂ levels from the fires. These tests demonstrated the system’s ability to detect increased carbon dioxide concentrations in the atmosphere. Variogram analysis is used to insight into the distance over which spatial correlations can be used to provide optimal spatial separation between measurements from sUAS swarms.