Time Variation

Select a site by clicking on it. This tool is capable of plotting multiple sites together. To choose multiple sites, first select a single site, then hold the CTRL key while clicking additional sites.

Select a variable by clicking on it. The pollutants available will depend on the selections of other parameters (e.g. site and date range selected). This tool is limited to plotting up to 10 variables together. To choose multiple variables, first select one then hold the CTRL key while selecting additional variables.

Choose to enter either 'Specific Dates' or 'Specific Years'. 'Specific Dates' allow you to choose day, month and year to start and stop your analysis. 'Specific Years' will allow you to quickly choose the years of interest to you and the analysis will commence on 1st January and run until 31st December of those selected years.

This option allows you to compare the trends in pollutants with very different concentration scales (for example NO_X with CO) in the same plot. The variables are divided by their mean values in order to normalise them.

Confidence Interval If this option is selected then the coloured shading (representing the 95% confidence interval) for each pollutant is shown. Where multiple pollutants are selected in the same plot, it may be more useful to remove this option to better show the trend lines themselves.