A Stereo Photogrammetric Technique Applied to Orographic Convection

This paper describes a technique for photogrammetric analysis of stereo pairs of images that is applied to the study of orographic convection. The technique is designed for use with digital images and assumes detailed knowledge of the camera properties (focal length and imaging chip) but that the position and orientation are known as a first guess. An iterative scheme using known landmarks on the frame is used to determine the camera orientation. The scheme is accurate to 10 – 100 meters at a distance of 15 km from the camera pair. The transition from shallow to deep convection over the Santa Catalina Mountains in southern Arizona on July 26, 2005 is presented. The three-dimensional structure of the visible portion of the cloud is determined and compared with the composite reflectivity from the National Weather Service WSR-88D radar and the tropopause height from the 12 UTC sounding in Tucson, providing additional validation of the scheme. Tracking of individual turrets characterized the shallow to deep transition, with the cloud heights limited to beneath 6000 m asl for the first 1 1/2 hours followed by the development of deep convection. The motion and location of the turrets was consistent with the idea that moistening by shallow convection conditions the atmosphere for deep convection.