NASA Radar and Disdrometer Observations During the Iowa Flood Survey (IFloodS)

During the spring of 2013, NASA, in collaboration with other government agencies and members of the U.S. academic research community, including the University of Iowa and Colorado State University, conducted a precipitation-measurement field campaign referred to as Iowa Flood Studies (IFloodS). The main goal of IFloodS was to support Ground Validation program activities of the Global Precipitation Measurement (GPM) satellite mission: specifically, IFloodS was the first of several planned integrated hydrologic field experiment (other campaigns being the Integrated Precipitation Hydrology Experiment (IPHEX) in North Carolina, Spring 2014, as well as the Olympic Mountain Experiment (OLYMPEx) in the Washington Cascades in winter of 2014-15). Iowa was chosen as a site because of its relatively uniform land use, the absence of orographic and coastal effects, the areas frequent flooding with climatological peak in May and June, and the existing observational and logistical support provided by the Iowa Flood Center of the University of Iowa. IFloodS science objectives envisage the production of accurate, high-resolution time and space ground reference rainfall and stream flow datasets as a means to assess uncertainties in the satellite algorithms and products.

NASA provided significant resources for the IFloodS field campaign, including the NASA dual-POLarimetric (NPOL) and the Dual-frequency, Dual-polarization, Doppler Radar (D3R), 14 Automated Parsivel2 Units (APU), six 2-Dimensional Video Disdrometers (2DVD) and 25 automated rain gauge platforms. The NPOL and D3R were used in a synergistic mode whereby they both sampled the same geometrical and temporal volumes along a southeast sector that was well populated by both rain gauges and disdrometers. In this study, we will use high temporal and spatial resolution radar data from NPOL and disdrometer observations to evaluate currently employed radar retrievals of the drop size distribution (DSD) and its integral parameters such as reflectivity and liquid water content. It is envisaged that these comparisons will provide further refinements of existing NPOL retrievals and thus can be used to provide more robust data sets from additional post-launch campaigns for validating satellite-based DSD retrievals from GPM, which is currently scheduled for launch in early 2014.