Uncrewed Aircraft System Measurements of Atmospheric Surface-Layer Structure During Morning Transition

This study applies uncrewed aircraft systems towards the investigation of surface-layer structure during the morning transition. Three uncrewed aircraft systems simultaneously measuring horizontal transects were partnered with a fourth measuring vertical profiles during two consecutive mornings as part of the 2017 Collaboration Leading Operational Unmanned Aerial System Development for Meteorology and Atmospheric Physics (CLOUDMAP) measurement campaign near Stillwater, Oklahoma, USA. Data were analyzed to extract time-dependent single-point statistics of kinematic and thermodynamic variables from the uncrewed aircraft systems. In addition, an approach is presented by which multi-point spatial statistics in the form of auto- and cross-correlations could be calculated from the measurements. The results reflect differences in the evolution of spatial statistics with altitude for each of the two days at scales smaller than 500 m, despite very similar synoptic conditions. Conditional averaging was also applied to identify the structure of sweep and ejection motions and results revealed similarities to observations from canonical wall-bounded flow.