U.S. Department of Energy Office of Biological and Environmental Research

BER Research Highlights


ARM Lassos a New Parameterization
Published: January 23, 2019
Posted: March 07, 2019

The ARM LASSO project provides the high resolution simulations and observations needed to comprehensively evaluate a new model formulation of boundary layer mixing and shallow cloud formation.

The Science
Shallow cumulus fields have important effects on the surface and atmosphere, but are challenging to model and difficult to observe.  Within weather and climate models, numerical formulations (called parameterizations) are needed to represent turbulent mixing processes that cannot be explicitly resolved in the model.  A new class of parameterizations, which integrate both the boundary layer mixing processes and cloud formation, are starting to be used more widely in weather and climate models.  These formulations are known as “eddy diffusivity mass flux (EDMF)” parameterizations.  In this study, a new EDMF parameterization implemented in the Weather and Research Forecasting (WRF) model is evaluated against a set of observationally-forced high resolution large eddy simulations and observations produced from the Atmospheric Radiation Measurement (ARM) user facility’s LASSO project. 

The Impact
The new EDMF parameterization for boundary layer mixing and cloud performed very well in the single column tests conducted in this work.  The 15 cases examined in this study are far more than shown in previous work evaluating new parameterizations, and allow scientists to consider how the boundary layer and shallow cloud schemes handle the variation in cloud amount from day to day and across different forcing data. This study shows the value of the LASSO dataset in moving beyond single case studies and the typical idealized test cases used during previous studies. Using multiple simulated days under the same meteorological regime of shallow convection helps identify how well EDMF captures this regime.

Summary
Representation of shallow cumulus is a challenge for mesoscale numerical weather prediction models. These cloud fields have important effects on temperature, solar irradiance, convective initiation, and pollutant transport, among other processes. Recent improvements to physics schemes available in the Weather Research and Forecasting (WRF) Model aim to improve representation of shallow cumulus, in particular over land. The DOE large-eddy simulation (LES) Atmospheric Radiation Measurement (ARM) Symbiotic Simulation and Observation Workflow (LASSO) project provides several cases that are used here to test the new physics improvements. The LASSO cases use multiple large-scale forcings to drive large-eddy simulations, and the model output is easily compared to output from WRF single-column simulations driven with the same initial conditions and forcings. The new Mellor-Yamada-Nakanishi-Niino (MYNN) eddy diffusivity mass-flux (EDMF) boundary layer and shallow cloud scheme produces clouds with timing, liquid water path, and cloud fraction that agree well with LES over a wide range of those variables. Here we examine those variables and test the scheme’s sensitivity to perturbations of a few key parameters. We also discuss the challenges and uncertainties of single-column tests. The older, simpler total energy mass-flux (TEMF) scheme is included for comparison, and its tuning is improved. This is the first published use of the LASSO cases for parameterization development, and the first published study to use such a large number of cases with varying cloud amount. This is also the first study to use a more precise combined infrared and microwave retrieval of liquid water path to evaluate modeled clouds.

Contacts (BER PM)
Sally McFarlane
ARM Program Manager
Sally.McFarlane@science.doe.gov

PI Contact
Wayne M. Angevine
NOAA Earth System Research Laboratory
wayne.m.angevine@noaa.gov

Funding
This work was supported by the NOAA Atmospheric Science for Renewable Energy program. Gustafson and Endo are supported by the DOE Office of Science Biological and Environmental Research via the Atmospheric Radiation Measurement User Facility. Kay Suselj’s research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. Parts of his research were supported by the NASA MAP Program and the NOAA/CPO MAPP Program.

Publication
Angevine, WM, J Olson, J Kenyon, WI Gustafson, S Endo, K Suselj, and DD Turner. "Shallow Cumulus in WRF Parameterizations Evaluated against Lasso Large-Eddy Simulations." Monthly Weather Review 146(12), 4303-4322 (2018). [DOI:10.1175/mwr-d-18-0115.1]

Topic Areas:

  • Facility: DOE ARM User Facility

Division: SC-23.1 Climate and Environmental Sciences Division, BER

 

BER supports basic research and scientific user facilities to advance DOE missions in energy and environment. More about BER

Recent Highlights

May 10, 2019
Quantifying Decision Uncertainty in Water Management via a Coupled Agent-Based Model
Considering risk perception can improve the representation of human decision-making processes in age [more...]

May 09, 2019
Projecting Global Urban Area Growth Through 2100 Based on Historical Time Series Data and Future Scenarios
Study provides country-specific urban area growth models and the first dataset on country-level urba [more...]

May 05, 2019
Calibrating Building Energy Demand Models to Refine Long-Term Energy Planning
A new, flexible calibration approach improved model accuracy in capturing year-to-year changes in bu [more...]

May 03, 2019
Calibration and Uncertainty Analysis of Demeter for Better Downscaling of Global Land Use and Land Cover Projections
Researchers improved the Demeter model’s performance by calibrating key parameters and establi [more...]

Apr 22, 2019
Representation of U.S. Warm Temperature Extremes in Global Climate Model Ensembles
Representation of warm temperature events varies considerably among global climate models, which has [more...]

List all highlights (possible long download time)