Impact of assimilating AERI and Doppler Wind Lidar Retrievals on Convection-Allowing Ensemble Forecasts of Thunderstorms

Reports from the National Research Council and instrumentation workshops have recommended that networks of ground-based profiling systems (e.g., microwave and infrared radiometers, Doppler wind profilers and lidars, and water vapor lidars) be developed for monitoring rapid changes in the local severe convective environment. To explore the potential of these systems for severe weather forecasting applications, the University of Oklahoma and the National Severe Storms Laboratory have developed the Collaborative Lower Atmosphere Mobile Profiling System (CLAMPS-2), which contains a Microwave radiometer and an Atmospheric Emitted Radiance Interferometer (AERI) to retrieve temperature and water vapor, a Doppler Wind Lidar (DWL) to profile the wind in the lower atmosphere, and a radiosonde system.

In 2016 and 2017, CLAMPS-2 was deployed in the pre-convective and near-storm environment for 14 severe weather events. The impacts from assimilating AERI retrievals of temperature and water vapor and the DWL retrievals of the horizontal wind (derived from a VAD technique) within an ensemble of convection-allowing model forecasts of thunderstorms will be presented. The CLAMPS-2 observations were guided by real-time ensemble sensitivity analysis (ESA) to increase the likelihood that observations were obtained in regions of the environment that impact later forecasts of thunderstorms. The retrievals (along with routine observations, including reflectivity and radial velocity from nearby WSR-88Ds) are assimilated simultaneously on a 15-km grid and a nested 3-km grid using the WRF-DART assimilation system and is driven by initial conditions from the continuously-cycled ensemble analyses produced by the NCAR ensemble. These ensemble analyses are used to initialize an ensemble of 10-h forecasts on the 3-km grid. Changes to these forecasts with and without the targeted AERI and DWL observations over 12 days will be presented. Initial results indicate substantial impacts are made to the boundary layer state that improve the positioning of a forward-propagating MCS for many hours into the forecasts (on May 16, 2016), increase the confidence of a tornadic supercell along a weak dryline (May 23, 2016), and correctly decrease the likelihood of severe weather through the assimilation of convectively-induced drying sampled by the AERI (May 26, 2016). The aggregate impacts across all 12 cases will be presented at the conference.