This study investigates the shapes and fall speeds of freezing and frozen raindrops through field observations using an instrument called the High-Speed Optical Disdrometer (HOD) that we developed recently. Separate 'drag coefficientв€’Reynolds number' relationships for freezing and frozen raindrops were developed. The drag coefficients for the observed hydrometeors were compared with the predictions of the available drag coefficient models.

Frozen raindrops showed a larger scatter of fall speeds around the mean fall speed of a given drop size than those of the freezing raindrops due to the shape variety among the frozen raindrops with the aforementioned distinct features. For the fall speeds of freezing and frozen raindrops, field observations demonstrated a good agreement with the predictions of the available parameterizations. Separate empirical axis ratio parameterizations were developed for the freezing and frozen raindrops using the HOD field observations and extensions to an available shape model were also incorporated. ratio of the vertical to horizontal chord) and fall speeds were compared with the predictions of available models. volume equivalent diameter, D) resemble the shapes of warm raindrops, majority of frozen raindrops (61 % of the frozen raindrops with D > 1.0 mm) exhibited a distinct feature such as a spicule, bulge, cavity, or aggregation. Our field observations showed that while the shapes of all of the observed freezing raindrops and a portion of the frozen raindrops (39% of the frozen raindrops that are larger than 1.0 mm in.

This data provided valuable insights into fall speeds of freezing and frozen raindrops, which will be discussed in our presentation. In this study, field data was collected using a new instrument called the High-speed Optical Disdrometer (HOD) that we recently developed. The information on freezing and frozen raindrop fall speeds has important meteorological applications: for example, identification of precipitation type and radar retrieval of precipitation rates during such events. Moreover, the parameterizations developed for predicting the terminal fall speeds of warm raindrops are not applicable to freezing and frozen raindrops.

raindrops that are in liquid state during fall and after impact on a surface), yielding a number of parameterizations to predict the terminal fall speed of warm raindrops, such studies are limited for freezing and frozen raindrops. While there have been many studies on the fall speed of warm raindrops (i.e. In this study, we investigated the fall speeds of freezing and frozen raindrops through field observations.

Frozen raindrops are called