TheilSen

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. sites and date range selected). This tool is set up for analysing the trend in a single pollutant over time.

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.

Use this drop-down menu to select the way you want your data split. The default option will produce a single plot covering the entire range of the data. Where multiple sites are selected, this menu is greyed out, multiple plots split by site are produced. Selecting 'Hour' will produce an individual plot for each of the 24 hours throughout the day and so helps to represent diurnal differences. Selecting 'Weekday' will produce an individual plot for each day of the week and so is helpful in highlighting differences throughout the working week and weekends. Selecting 'Month' will show twelve plots, one for each month, helping to visualise seasonal changes through the year. Selecting 'Wind Direction' will split into eight compass point sectors, and selecting 'Wind Speed' will split into four quartiles using the modelled wind direction or speed from the UK air quality forecast which can be useful in identifying particular sources.

Choose from the drop-down box either to plot monthly means or annual means. At least 6 years of data are required to plot annual means. A data capture threshold of 75% has been set for averaging.

Checking this option will amend the plot to account for statistically calculated seasonal variation. If this option is not selected, then a single plot of the original data will be plotted.