Observing the Relationship between Reflectivity Changes and Vertical Velocity in Convection.

The upcoming INCUS project is a cooperative effort that will estimate convective mass fluxes in the tropics by monitoring changes in reflectivity over time (∆Z method) using three Ka-band radar satellites. TIME-SLICE CO 2024 was a field campaign that aimed to verify INCUS methods and test data collection and analysis techniques. This project utilizes data collected during TIME-SLICE CO to observe the relationship between ∆Z and vertical velocity (w) on timescales under 120s. Reflectivity data were collected via a scanning C-band radar that primarily took RHI scans. Vertical velocity data were collected via a vertically pointing S-band radar with corrections for hydrometeor fall speeds. Reflectivity images were gridded at 100m resolution and a coarser “INCUS-like” resolution. To properly observe the relationship between ∆Z and w, corrections for advection needed to be applied to the reflectivity data. This was done by tracking a column that passed over the vertically pointing radar to two radials on which the scanning radar had collected RHIs, estimating the travel time of the column between radials using HRRR analysis, and comparing the ∆Z on the tracked column to the w from the vertically pointing radar. When comparing ∆Z and w, we found a reasonably consistent positive correlation above 5km in the two cases analyzed. However, significant +∆Z anomalies appeared at the top of the cloud in both cases, which could not be attributed solely to vertical advection.