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.
Select a Period option to control how the time series is presented along the radius of the plot. 'Default' produces a plot showing the diurnal variation by hour of the day and wind direction which can for example highlight a road traffic source. 'Weekday' will plot variation by day of the week so is helpful in highlighting differences throughout the working week and weekends. Selecting 'Season' will bin the data into proper seasons showing the trend across seasons. 'Trend' does not bin the data, instead showing variation by wind direction over the whole time series.