CFD-based Characterization of a WxUAS Sensor Housing for In-situ Atmospheric Sampling

Accurate information within the atmosphere’s first 1.5 km, where several relevant weather phenomena occur, remains limited even though observations are collected by a variety of systems. Unmanned Aerial Weather Measurement Systems (WxUAS) have been used as a complementary tool to collect meteorological observations and address this low-altitude data gap. However, driven by diverse research objectives, their unstructured development has resulted in poor measurement standardization. These inconsistencies have been documented and explored in the literature, reflecting an ongoing community interest in identifying WxUAS design features that support more representative and intercomparable observations. A relevant example of a design incorporating several WxUAS-community-identified desirable features, such as an aspiration fan, multi-layer shielding and intake overhangs, is the sensor housing developed by Azevedo et al. Because this design was developed for winter-weather precipitation observations, it was optimized to protect the sensing elements from contaminants present in that environment. As a result, it was not evaluated under conditions where other sources of measurement bias, such as solar radiation, are present. Consequently, this study uses Computational Fluid Dynamics (CFD) to evaluate Azevedo et al.’s sensor housing in an effort to assess whether the desirable design features included in the housing may support accurate measurements under emulated solar radiation conditions. Although Azevedo et al. met their design objectives for winter-weather observations, the results showed that the housing depends on the aspiration fan to deliver reliable airflow over the sensing elements and exhibited temperature biases under solar radiation conditions. Additionally, to evaluate the 90◦ overhangs, responsible for "filtering" large droplets in Azevedo et al.’s design, a particle study was conducted, which showed that particle counts at the sensing region decreased with increasing particle diameter. As this work aims to contribute to community efforts to improve WxUAS design and support measurement standardization and address the low-altitude in situ data gap, it leverages the strengths and limitations of Azevedo et al.’s design by developing an improved sensor housing. This redesign was evaluated through similar solar radiation simulations and a particle study and results indicated that the particle-filtration capabilities were kept, making the design suitable for a wider range of environments, while improving measurement performance.