The Lagrangian Analysis Tool



Heini Wernli

Michael Sprenger


Sebastian Schemm


Lagrangian parcel trajectories are widely used in the atmospheric and oceanic sciences, for instance, to identify flow structures in extratropical cyclones (e.g., warm conveyor belts) or ocean eddies, long-range transport pathways of moisture, or to study the physical processes underlying the formation of sea surface temperature, salinity or potential vorticity anomalies.


Is the version used to compute air-parcel trajectories based on the output of the COSMO mode. An online and offline version of the tools is available. For the online computation the actual model time step is used, which increase the accuracy of the trajectories.


Miltenberger, A.K., Pfahl S., and Wernli H. (2013): An online trajectory module (version 1.0) for the nonhydrostatic numerical weather prediction model COSMO, Geosci. Model Dev., 6, 1989–2004, doi:10.5194/gmd-6-1989-2013.


The ocean version is the latest member of the LAGRANTO family. It can be used to compute ocean-parcel trajectories based on ECMWF's Ocean Reanalysis data (ORAS5). The triangular grid of the input data is transformed and rotated into a regular lat/lon grid. At the boundaries no-normal and no-slip boundary conditions are applied. This version is under development.


Schemm, S., A. Nummelin, N. G. Kvamstø, and Ø. Breivik (2017): The ocean version of the Lagrangian analysis tool LAGRANTO, J. Atmos. Oceanic Technol., 6, n/a, doi:10.1175/JTECH-D-16-0198.1.