Unmanned aircraft observations of airmass boundaries: The Collaborative Colorado-Nebraska Unmanned Aircraft System Experiment

Unmanned aircraft (UA) can provide observations of atmospheric phenomena that are either difficult or impossible to attain with existing platforms. It is for this reason that facilitating the maturation of this relatively new technology has become a high priority in the atmospheric sciences. Most recent applications of UA have involved the high altitude, long endurance (HALE) configuration. The utility of smaller UA tasked with missions in the planetary boundary layer has only recently begun to be explored.

One of the advantages of UA over conventional platforms is the ability of UA to collect thermodynamic data that represent meteorological phenomena with small horizontal scales. Multiple Doppler radar data can represent similar scales but only as manifested in the wind velocity (derived thermodynamic measurements have limited practical use). Upsondes and dropsondes can sample both temperature and moisture but practical limitations in sonde deployment mean that they are incapable of representing phenomena with horizontal scales less than ~20-50km. Manned aircraft can sample the same data at the same scale as UA but their high cost and restrictive flight plans generally render them less efficient/effective than unmanned aircraft.

Despite the potential benefits of UA, their use in sampling low-level meteorological phenomena (particularly over land) is extremely rare. This rarity is due in part to stringent FAA regulations. While such regulations are sometimes viewed as impediments to scientific progress they are largely designed to protect people both on land and in the air. Nevertheless, the procedure required to obtain authorization to operate UA in the low-levels of the National Airspace System (NAS) does limit the many potential scientific applications of UA.

Ultimately, the complicated marriage of engineering, meteorology, and policy involved in using UA to observe atmospheric phenomena in the NAS planetary boundary layer over land has meant that the feasibility of this endeavor is unknown. However, an NSF-funded field project to be conducted during the summer of 2008 aims to examine this feasibility.

The project (the Collaborative Colorado-Nebraska UA Experiment – CoCoNUE) is led by the Research and Engineering Center for Unmanned Vehicles (RECUV) at the University of Colorado at Boulder and the University of Nebraska – Lincoln and involves the participation of Colorado State University (CSU) and NCAR's Atmospheric Technology Division (NCAR-ATD). For this project, an UA will collect in situ data across airmass boundaries located over the Pawnee Grasslands of northeast Colorado and identified primarily by the CSU CHILL and Pawnee radars. The specific objectives of this work are as follows:

• Demonstrate the targeting of a mesoscale atmospheric phenomenon that has been identified with supplemental observing platforms

• Examine flight strategies for sampling airmass boundaries with UA

• Test the rapid deployment of the UA system (UAS)

Results from CoCoNUE will be presented at the conference. The implications of these results for future field campaigns involving UA will be discussed.