Assessing the Impact of Initial and Boundary Conditions on WRF Microphysics in Northeast U.S. Winter Cyclones with the Support of Extensive NASA Field Campaign Instrumentation

Northeast U.S. Winter Cyclones, Nor’easters, can cause significant impacts to daily life for society through disruptions to transportation and electric power distribution. While Nor’easters have been investigated in many different types of research studies over the years, the ability to accurately forecast these storms, particularly precipitation phases, amounts and locations, is still insufficient and presents many challenges. Over the last three winters, two separate NASA field campaigns have provided additional instrumentation and datasets to sample and validate Nor’easters. These include the Investigation of Microphysics and Precipitation for Atlantic Coast-Threatening Snowstorms (IMPACTS, McMurdie et al. 2022) and a GPM Ground Validation mission at the University of Connecticut (Filipiak et al. 2024, in review).

In this study, multiple Miller type (A and B) Nor’easters are examined using high resolution Weather Research and Forecasting Model (WRF, v4.5.2) simulations with a focus on the sensitivity of precipitation microphysics due to initial and boundary conditions. Here, four different initialization datasets are analyzed ranging from ~0.1 degree to ~0.3 degree grid spacing including: NAM Analysis (12km), NCEP-Final Analysis (0.25 degree), ERA5 (31km), and NARR (32km). Ground validation data from both field campaigns are used to validate precipitation and key meteorological outputs and features from WRF. This includes additional radiosondes, Micro Rain Radars (MRRs), Weighing Precipitation Gauges, multiple types of disdrometers, and additional meteorological surface observations located across the Northeast United States. In addition to the field campaigns, Stage IV precipitation and National Snowfall Analysis data are used to validate the precipitation output in different simulations. We will present a variety of results that highlight the differences, influences, and challenges of the initial conditions on microphysics and precipitation in the Nor’easters.