Anticipating the Impact of Wind on UAS-Based Atmospheric Profiling in the Lower Atmosphere

We are moving into an era in which the emerging technology of unmanned aircraft systems (UAS) could dramatically impact the field of meteorology. The deployment of small unmanned aircraft to collect in situ measurements of the atmospheric state in conjunction with other weather observing systems will likely lead to significant improvements in both weather forecasting skill and resolution. However, before we can realize the potential of weather-monitoring UAS (WxUAS), many technical and logistical questions must be confronted and resolved. For example, what is the optimal choice of sensor and sensor integration for different types of aircraft and observing strategies and data collection goals? How can we best integrate manned and unmanned aircraft into the National Airspace System? What types of meteorological conditions should the WxUAS be designed for, e.g., temperature extremes, icing conditions, clouds, wind conditions, and turbulence?

In this presentation, we focus on the prospects of using WxUAS to collect vertical atmospheric measurements (profiles) at fixed surface observing sites. In this framework, the WxUAS would be expandable and modular to accommodate several different sensor packages and provide accurate in situ measurements in varying meteorological conditions. In particular, we concentrate on the expected wind conditions to be experienced by WxUAS when operating in profiling mode. Our goal is to examine, for a given location and desired flight ceiling, how much wind loading one can expect for different times of day and different periods throughout the year. For example, if a particular WxUAS is rated as being able to operate in winds up to a certain maximum, at what percentage of the time should one expect the aircraft to reach its maximum flight height? Moreover, from a statistical perspective, for those flights when the aircraft would not be able to reach its maximum height, to what altitude would it have been able to fly? Such information will be useful when planning the concept of operations for WxUAS deployments.

We have examined wind climatology metrics in Oklahoma based on an evaluation of North American Regional Reanalysis (NARR) and High Resolution Rapid Refresh (HRRR) data. A limited number of Oklahoma Mesonet sites were selected as suitable for routine atmospheric profiling using WxUAS. Selection criteria included spatial distribution, airspace considerations, proximity to urban areas, and similar factors. Vertical profiles of wind speed and direction were then constructed from the nearest corresponding column of model data for each of the sites. From these data we were able to calculate the statistics mentioned above for different types of WxUAS and their corresponding specifications, such as recommended range of wind speed for safe operations. Additionally, we have evaluated the representativeness of the NARR and HRRR wind estimates through comparisons with wind measurements from radiosondes launched from the KOUN site in central Oklahoma. Results from this analysis will be presented and discussed, especially in the context of how prevailing wind conditions can impact both the design of WxUAS and their operations when sampling the atmosphere. Having developed the analysis framework as applied to sites in Oklahoma, we plan to extend the study to other areas of the US.