The Effect of Intra-Volume Scans on MRMS Derived Products Using Numerically Simulated Radar Data

The implementation of two adaptive intra-volume scanning options in volume coverage pattern (VCP) 212 named the Supplemental Adaptive Intra-Volume Low-Level Scan (SAILS) and the Mid-Volume Rescan of Low-Level Elevations (MRLE) recently have enhanced the low-level temporal resolution of the weather surveillance radar 88 Doppler (WSR-88D). These options augment the number of 0.5 degree elevation angles for SAILS and up to the lowest 4 elevation angles for MRLE. These adaptive scanning strategies increase the revisit time of certain portions of the atmosphere, but concurrently lengthen revisit time by several minutes on the mid and upper level elevation angles. The Multi Radar Multi Sensor (MRMS) system uses a combination of many radars across the United States and Canada and merges the data together to form a rapidly updating gridded dataset of radar data. MRMS is updated every 2 minutes taking in the newest produces and integrating them into the system. Changes in VCP and these intra-volume options across several neighboring WSR-88Ds affect MRMS output by creating sampling differences of the storm by the radar than VCPs have done in the past.

In a previous observational study, vertically integrated products were shown to be altered due to the changes implemented in these intra-volume options. To investigate the effect of intra-volume scans further, two high resolution idealized simulations are performed simulating a supercell and a quasi-linear convective system (QLCS). The model result will then be decomposed to create synthetic WSR-88Ds observations using these different VCP and intra-volume options. The synthetic observations generated at several locations and distances from the simulated storm to mimic WSR-88D spacing are merged together using the MRMS system. Merged output are created consisting of different VCPs and scanning strategies that may occur during an event. The merged output is compared to the original simulated storms investigating how well these intra-volume options are sampling the simulated storm and how these VCP changes alter the MRMS products. This study discusses positive and negative effects of these adaptive intra-volume options on the MRMS system, including storm coverage by WSR-88D, vertically derived products, and new challenges created by these intra-volume options that are currently operational.