The PALM model system


PALM is an advanced and state-of-the-art meteorological modeling system for atmospheric and oceanic boundary layer flows. It was developed as a turbulence-resolving large-eddy simulation (LES) model specifically designed to run on massively parallel computer architectures. Meanwhile, turbulence closure based on the Reynolds-averaged Navier-Stokes (RANS) equations has been added so that PALM can run not only in turbulence-resolving mode (i.e., LES) but also in RANS mode, in which the entire turbulence spectrum is parameterized.

Due to the extensive extensions to the model, PALM is no longer an abbreviation, but rather the name in its own right. It describes the PALM model system, which consists of the PALM model core and the PALM-4U components. These components are shipped along PALM and 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). We kindly request that you cite PALM in all your publications. For details, see citing PALM.


[ 2024-15-04 ] We are pleased to share details about this year’s PALM Model Conference. Check it out:
[ 2023-11-03 ] We have started to create a new documentation web page, which is always up-to-date for the current PALM release. Check it out:

We are currently working on the new official PALM documentation. Since the transition will take some time, those parts that have been already finished are linked to the existing old documentation. Please don't hesitate to contact us via the ticket system in case you find any dead or wrong links. We apologize for any inconvenience.


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 is 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)
  • online 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
  • ocean mode with salinity equation and equation of state for seawater
  • bulk cloud physics (Seifert-Beheng scheme)
  • 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
  • dynamic core and thermodynamics runs on multiple GPUs using CUDA-aware MPI

PALM-4U components

For urban applications, the PALM-4U components offer a variety of capabilities and features to answer research questions and to tackle 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 the 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:

PALM-4U Logo

  • 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 have been, are, 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

PALM users world map1

  1. 1. The world map shows groups carrying out scientific research with PALM and that have published at least one paper in a peer-reviewed journal. You want to be listed in the map? Let us know!

Last modified 2 months ago Last modified on Apr 15, 2024 7:13:03 AM

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