Features

General            -            Specific Features            -            Background on Traj. Analysis

ZeFir includes several innovative features in order to get and more comprehensive understanding of trajectory analyses. All this, with user-friendly panels....

- Temporal extension of dataset

Sometimes, for low time resolution dataset, only one trajectory is associated to each point, being not necessarily representative of the whole diversity of air masses that came over the site during sampling time. By enlarging the dataset, more backtrajectories are used, leading to more robust results.

One example is sodium ion obtained from high volume filter sampling in Metz, East of France. Sampling has been performed daily, 1d/3, during 2015. From previous studies, we can reasonably expect sodium to mainly originate from sea salt, and thus to show a clear oceanic origin. However, when using the original dataset, this origin is not obvious, as results show highest concentrations in French inlands. But adding backtrajectories at +3h, +6h, +9h, 12h, +15h, +18h and +21h greatly helped to highlight the oceanic origin of sodium ion.

- Explore trajectories

Although backtrajectories don't need to be physically imported for trajectory analyses, ZeFir allows an automatic (or manual) import to visualize them, using different color-codes:

- Trajectory cut-off options

One key aspect of trajectory analysis is to remove any unrepresentative part of trajectories. For instance, if rain occured along the path of the trajectory, or if trajectory altitude goes above a certain threshold, there is no need to take the rest of the trajectory into account.

- Continuous weighing function

As regularly performed, weighing function consists in a discrete function, where coefficients are empirically determined upon certain ranges of n values. Four ranges are usually used, meaning that 7 parameters need to be set (4 weighing coefficients, and 3 range limits). But a continuous function could be used instead, from a sigmoid-like function, because they also describe a transition state. With the equation below, only 3 coefficients need to be determined.

- Re-weight panel

As the weighing function is empirical, the determination of the weighing coefficients can be time consuming, mainly because the user needed to re-run the analysis as many times as necessary. In ZeFir, a weighing panel is dedicated to enable re-weighing any previous run, which greatly reduces the time needed for this step.

- HYSPLIT trajectory calculations

Through a simplified panel, ZeFir allows the calculation of backtrajectories by controlling the scripts provided in the HYSPLIT software package.