Observations of Atmospheric, Surface, and Subsurface Processes from a Combination of Ship-Based Instrumentation and Ship-Launched UAVs

We present measurements obtained during the October 2012 EquatorMix experiment (0N, 140W), in which we deployed ship-launched and recovered Boeing-Insitu ScanEagle unmanned aerial vehicles (UAVs) to measure momentum and energy fluxes, ocean surface processes, and the marine atmospheric boundary layer (MABL). The UAV dataset is complemented by measurements from a suite of ship-based instrumentation, including a foremast eddy covariance system, scanning and point lidar altimeters, a laser Doppler wind profiler, and a digitized X-band radar system. The combination of the unmanned aircraft and ship instrumentation provides a unique and valuable dataset of many air-sea interaction phenomena, extending from 100s of meters below the surface to 1500 m above. UAV-based flux measurements at low altitudes (down to 30 meters) are consistent with ship-based eddy covariance measurements, but reveal differences between along- and crosswind sampling flight legs associated with longitudinal roll structures that are not captured by the ship measurements. Additionally, surface elevation modulations observed with the UAV lidar altimeter (coupled with a GPS/IMU) give evidence of high-frequency equatorial internal waves, with measurements consistent and coherent with those from ship-based X-band radar, the Hydrographic Doppler Sonar System (HDSS), and a theoretical model.