Wind Analysis

Wind Analysis consists in coupling concentration data at a sampling site and collocated wind measurements, i.e. direction and/or speed. Various methodologies exist, and the philosophy of ZeFir is to make most of them available to the scientific community.

As of now, ZeFir allow the use of Non-parametric Wind Regressions, and pollution roses. For more information on these techniques, go to Background on Wind Analysis.

Even if "only" 4 approaches are available, there are many ways to present the data, depending on the information needed. Below is an example, showing four ways to plot 1-h NOx data from Metz (France) during 2015.

The Clock rose is obtained by using the “Pollution Rose” statistic, with WD Wave being angles representing hours (i.e. here, WD=mod(hour*30,360)). The dataset have been divided into subsets following an external variable, being the hour values between 0 to 11h, and 12h to 23h.

The Annular plot is similar to what can be done with Openair. It is a NWR calculation, where wind speed is replaced by the hours. There is thus information about diurnal variation, and wind direction dependence.

This example puts the emphasis on the fact that they are many ways possible to explore any kind of dataset, some of them being available in ZeFir. The user should not hesitate to go beyond the proposed features. For example, ambient temperature or RH can be used as a “pollutant” to illustrate its wind dependence, or as bivariate variables using Cartesian coordinates.