The Graz Lagrangian (GRAL) system is a Lagrangian particle model with a free Graphic User Interface (GUI) available in both Linux and Windows and it is well know among odour modellers. Now the developers have released the version 21.09 with plenty of bug fixes and new features.
One more year, the GRAL GRAMM team have been working on changes and modifications in the code, and correcting bugs. This is the list of new features and bugs corrected for GRAL, GRAMM and the Graphic User Interface (GUI) for this release.

A fundamental operation performing odor impact assessment is the analysis of meteorological data, particularly wind direction and speed. Such an analysis allows for example to evaluate the number of calms, which may give raise to high concentration values, and to spot possible errors in meteorological data before using them in an atmospheric dispersion models. Moreover, the determination of the prevailing wind direction allows to understand if possible sources are generally upwind of the potential receptors.