The atmospheric boundary layer is the lowermost layer of the atmosphere and is host to a plethora of physical processes that significantly affect weather, climate, and air quality. In many applications, detailed information about the boundary layer is required at high temporal and spatial resolution. The main purpose of the current model is to provide accurate and finely resolved inspace and time predictions of the atmospheric boundary layer. High-resolution predictions of the boundary layer are typically pertinent in the development and evaluation of weather and climate models, in fundamental studies of atmospheric dynamics including clouds and precipitation, the dispersion of pollutants, and the development of remote sensing instruments.

Although the current model simulates atmospheric flows at much higher resolution, typically 1 to 100 meters, than regional or global atmospheric models, the smallest scales of atmospheric motions are considerably smaller, about 1 mm. Because the resolution of all scales is impractical by current computing capabilities, the modeling technique of large-eddy simulation (LES) is used to account for the effects of unresolved motions. LES is extensively used in many engineering and scientific applications because it is considered the most accurate method for the high-resolution simulation of fluid flows.

The current software is a high-fidelity LES model of the atmospheric boundary layer. That is, it simulates a region of the Earth’s atmosphere in a rectangular domain, where the bottom plane is the Earth’s surface. The simulation tracks the time evolution of the atmosphere in the three-dimensional domain given initial and boundary conditions. The model includes the interaction of various physical processes, including turbulence, clouds, precipitation, and radiation. The output includes the three-dimensional state of the atmosphere (i.e., winds, temperature, water content) at user-selected time intervals, and statistical information (i.e. mean and covariance profiles) of various quantitates of interest.

The novel elements of the LES model are a new turbulence closure that is faithful to the physics of atmospheric turbulence and the use of a fully conservative scheme for the advection terms discretization. The main advancements of the software are in the areas of atmospheric turbulence modeling and the numerical methods that are used to solve the discrete equations. The software results in predictions of the atmospheric boundary layer of unprecedented realism and fidelity. It is the only model of atmospheric flows that yields predictions that are independent of the grid resolution. Moreover, the model can capture diverse atmospheric conditions without any parameter tuning. That is, an identical model setup can be used regardless of the meteorological conditions. Existing models of the atmospheric boundary layer require different model parameters depending on the atmospheric conditions and cloud types that are simulated.

This work was done by Georgios Matheou of Caltech, Daniel Chung of the University of Melbourne, and Michio Inoue for NASA’s Jet Propulsion Laboratory. For more information, contact This email address is being protected from spambots. You need JavaScript enabled to view it..

The software used in this innovation is available for commercial licensing. Please contact Dan Broderick at This email address is being protected from spambots. You need JavaScript enabled to view it.. Refer to NPO-49379.

NASA Tech Briefs Magazine

This article first appeared in the April, 2015 issue of NASA Tech Briefs Magazine.

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