The DOE Atmospheric Radiation Measurement Program’s LES ARM Symbiotic Simulation and Observation (LASSO) Workflow: Initialization, Forcing and Multiscale Data Assimilation

Abstract:

The Department of Energy Atmospheric Radiation Measurement (ARM) Program is developing a routine large-eddy simulation (LES) modeling framework at the ARM Climate Research Facility sites, known as the “LES ARM Symbiotic Simulation and Observation” (LASSO) Workflow. The routine simulations will be assessed using comprehensive ARM observations of the atmosphere and land-surface states, particularly cloud observations. Since small changes in thermodynamic profiles can manifest large changes in cloud properties, successful simulations require careful initialization, appropriate forcing, and possibly suitable lateral boundary conditions. We use a multiscale data assimilation (MS-DA) system as a major methodology for producing forcing datasets required by the LES modeling. The MS-DA will be implemented in the regional Weather Research and Forecasting (WRF) model at a cloud resolving resolution (~1 km). MS-DA leverages existing reanalyses (e.g., the NCEP North American Regional Reanalysis, NARR) and operational forecasting products (e.g. the North American Mesoscale Forecast System, NAM; the High-Resolution Rapid Refresh, HRRR) products, and takes advantage of ARM observations to directly constrain the spectra of horizontal scales down to a few km. The analysis from the MS-DA allows deriving initial conditions and forcing datasets for a range of spatial and temporal scales, developing hydrometeor forcing, exploring time-varying boundary conditions, and diagnosing other needed thermodynamic variables. It is stressed that the datasets from the MS-DA are integrated with datasets from other sources to form ensembles to account for uncertainties. The methodologies, implementation and evaluations are presented.