The PALM model system

PALM is an advanced and modern meteorological model system for atmospheric and oceanic boundary-layer flows. It has been developed as a turbulence-resolving large-eddy simulation (LES) model that is especially designed for performing on massively parallel computer architectures. Since PALM 5.0, the model is shipped along with several PALM-4U (PALM for urban applications, read: PALM for you) components that allow to employ the model for various urban applications ranging from the meso- to the microscale.

The PALM model system is free software. It can be redistributed and/or modified under the terms of the GNU General Public License (v3).

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PALM is regularly tested. The test status of the current revision is: More details here

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PALM

The model PALM consists of a dynamic solver for the Navier-Stokes equations and the first law of thermodynamics. By default, the model is used in an LES mode in which the bulk of the turbulent motions in the atmospheric boundary are explicitly resolved.

Further highlights and features of the PALM core are

• excellent scaling, so far tested up to 32,000 cores
• complex terrain is realized on a Cartesian grid (allows for steep orography and vertically oriented buildings)
• on-the-fly data analysis (during model runs) in order to avoid I/O bottlenecks
• interactive land surface model, coupled to the RRTMG radiation model
• wind turbine model (ADM-R) is implemented
• code can be switched to ocean version with salinity equation and equation of state for seawater
• embedded parallelized Lagrangian particle model for various applications (footprint calculation, simulation of cloud droplet growth, visualization, etc.)
• interface allowing users to plug in their own code extensions without modifying the default code

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PALM-4U components

For urban applications, the PALM-4U components offer a variety of capabilities and features to answer research questions and to tackles issues in modern city planning related to the urban microclimate and climate change. Above all, this includes the representation of buildings on a Cartesian grid at grid spacings down to 1 m and below. PALM-4U components are shipped with PALM and are available after installation of PALM. PALM-4U components are thus also available in PALM and might be used without being limited to urban area applications. Per definition, starting from PALM version 5.0, the user runs PALM-4U as soon as buildings are placed within the model domain and at least one of the following PALM-4U components is used:

• Energy balance solvers for building and paved surfaces
• Radiative transfer within the urban canopy layer, including shadowing effects and multiple reflections between urban structures
• Wall material model for heat transfer between atmosphere and building
• Indoor climate module, predicting indoor temperature, energy demand, and waste heat
• Chemistry module for the transport and conversion of reactive species
• Model self-nesting that allows to increase either model domain size or to focus on near-surface processes
• A multi-agent system for urban residents, allowing for biometeorological studies and escape scenarios
• Quasi-automatic external forcing by COSMO-DE model data
• A Reynolds-averaged Navier Stokes (RANS) type turbulence parameterization can be used instead of LES to reduce computational costs
• Analysis tools and direct output of biometeorological quantities

The PALM-4U components are have been and will be further developed by a consortium of institutions within the framework of the funding programme "[UC²] - Urban climate under change", funded by the German Federal Ministry of Education and Research (BMBF). For more information, see ​http://uc2-mosaik.org.

PALM news

[ 2017-12-16 ] Release of PALM 5.0 with PALM-4U components (beta) (Release notes)
[ 2017-06-02 ] This years PALM seminar is held at the Institute of Meteorology and Climatology, Leibniz Universität Hannover, 25th - 29th September (details)
[ 2017-05-30 ] New topography and surface-modeling concept implemented (details).