The meteorological service MeteoSwiss is compiling annual graphs of the average daily pollen load for the stations in the Swiss pollen monitoring network. The 14 most important allergens are depicted graphically for each station. The graphs are updated on a weekly basis during the pollen season.
The black bars represent the average daily birch pollen concentration (pollen grains per m3) for 2016 in Bern. The blue curve shows the average daily pollen values, calculated using the 20-year comparison period from 1996 to 2015. The axis for the pollen concentration has been limited at the top end in order to be able to show the values at the lower end, as it is these lower values which are important to allergy sufferers. This means that the exact figures for the highest loads are not shown. The exact value of the maximum concentrations has little relevance to allergy sufferers, as the threshold value for a high birch pollen load is as low as 70 pollen grains per m3. The graph clearly shows the pollen load as being frequently below average in this example.
Boxplot graphs are ideal for depicting the blossoming onset dates, the number of days with high pollen counts, and total pollen counts. The example shows the number of days with high pollen loads in 2016 in Bern, in comparison with the 20-year average from long-series data taken between 1996 and 2015. The current year is shown by the black diamond. The blue box indicates the 25% and 75% quantiles and overlays the average 50% values for the comparison period. The median (50%) is shown by a vertical line inside the box. Lines on the left and right hand sides indicate the maximum and minimum distributions. The graphs for the current year show the interim status of the seasonal developments to date.
The example shows there to have been a high pollen loads for hazel pollen on 17 days This value is significantly higher than that of an average pollen season, which is represented by the blue box. The hazel pollen season in 2016 in Bern was at a similar level to that of the most intense season in previous years.