Observing Vertical Motion of Deep Convective Clouds by Stereo Photogrammetry

Using stereo photography, the vertical velocities of convective clouds are measured over Biscayne Bay in Miami. When applied to deep convection, the stereo cameras observe typical ascent speeds in excess of 10 m/s. With a high frame rate, fine spatial resolution, and long range, the cameras are able to reconstruct the trajectories -- in three-dimensional space -- of individual convective plumes through their lifecycle deep into the upper troposphere. To ensure high accuracy when looking out over water, a novel algorithm has been designed to calibrate the orientation of the cameras in the absence of traditional landmarks. The accuracy is validated by comparing the cloud heights obtained from the stereo cameras to data from a colocated ceilometer, and by comparing the stereo-camera winds to data from nearby radiosondes. With the ability to capture full field-of-view data at a high frame rate (i.e., 0.1 to 10 Hz), stereo photography provides a unique and powerful complement to traditional radar technology.