3D Reconstruction of 2DVD-measured Raindrops for Precise Prediction of Propagation Parameters

Raindrop shapes and fall velocities in “turbulent times”

“…The inset pictures show two examples of drop shapes reconstructed from the two orthogonal camera images after correcting for drop horizontal velocity (Schönhuber et al, 2016). These horizontal velocity directions, determined for all moderate-to-large drops with axis of rotational symmetry, are shown as black points in panel (e).…”

“…In vast majority of the cases, drop shape measurements show that they largely conform to "intrinsic" low amplitude axisymmetric oscillations that can be maintained against viscous dissipation, and the velocity measurements show good agreement with the Gunn-Kinzer variation, with altitude adjustments in the appropriate cases. However, there have been very few studies of shapes and fall speeds in windy conditions (i.e., turbulence) (e.g., Tokay and Beard, 1996;Bringi et al, 2018;Montero-Martinez and Garcia-Garcia, 2016;Stout et al, 1995) and the possible coupling between the two.…”

Analysis of Raindrop Shapes and Scattering Calculations: The Outer Rain Bands of Tropical Depression Nate

“…It is the only disdrometer that gives the drop images in two orthogonal planes and the fall speed for each drop that falls in the 10 cm × 10 cm measurement area. Recently, the contoured shapes in the two orthogonal planes were used to derive the 3-dimensional particle shapes which have been described in [8,9,11]. The procedure involved in the drop contour derivation also includes a 'deskewing' technique which not only yields the corrected contoured shapes for each drop but also enables the magnitude and direction of the horizontal drop velocity to be determined.…”

“…The 3D shapes of each raindrop were reconstructed with Matlab-software using the procedure described in [8,9]. For each drop a STL-file (STL for stereolithography) was generated that characterizes the surface geometry of the drop without specifying material or scale information.…”

“…A relatively recent advance has been the use of 2DVD in reconstructing the 3D shapes of natural rain drops even if they are asymmetric [8,9] and further to calculate the scattering matrices of such asymmetric drops using advanced electromagnetic scattering codes [10,11]. This enables simulation of what is termed 'drop-by-drop' integration to arrive at the radar reflectivity, the differential reflectivity and the copolar correlation coefficient [12].…”