A column-based multi-platform assessment of atmospheric river events observed in complex terrain during the NASA GPM OLYMPEX field campaign

The GPM Olympic Mountains Experiment (OLYMPEX) was conducted over the 2015-2016 winter season with the goal of observing precipitation processes in Pacific frontal systems transitioning over the coastal and complex terrain of northwest Washington. Several atmospheric river-type events occurred during the field campaign and exhibited clear orographic enhancement, resulting in copious precipitation totals. GPM's full suite of specialized remote sensing and in situ instrumentation captured these events from multiple sampling perspectives and spatial and temporal scales. These platforms included the GPM Microwave Imager (GMI) and Dual-frequency Precipitation Radar (DPR) on board the Core Observatory satellite; ground-based scanning and profiling radars spanning S- to Ka-bands; several gauges and disdrometers; soundings; and a host of sensors mounted on the University of North Dakota Citation and NASA ER-2 and DC-8 aircraft.

Here, we utilize the SIMBA (System for Integrating Multi-platform data to Build the Atmospheric column) data-fusion system, developed specifically for synthesizing ground- and space-based GPM GV data to a single reference frame, to evaluate precipitation characteristics and processes in OLYMPEX's atmospheric river cases. The SIMBA data product provides multi-sensor observations on a common 3D grid to support efficient analysis of the vertical profile of precipitation. We will present results of a profile-based investigation of these events by focusing on the application of the SIMBA data-fusion tool to document characteristics and changes in precipitation variability, including but not limited to radar signatures, precipitation rates and amounts, and drop/particle size distribution parameters. By integrating data from several well-sampled events during the campaign, results will show a bulk perspective of the range of these parameters and how precipitation processes evolve across the transitioning oceanic, coastal, and mountainous terrain of the region. Additionally, aircraft-based measurements will be considered to provide further insight to the longer-duration ground-based observations available. This effort serves, in part, as an expansion of previous SIMBA-based OLYMPEX case study work, further demonstrating the usefulness of this unique data-fusion tool.