The meteorological service MeteoSwiss is compiling annual graphs of the average daily pollen count 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 count per m3) for 2021 in Bern. The blue curve shows the average daily pollen values, calculated against the 30-year comparison period from 1991 to 2020. 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 these lower values are important to allergy sufferers. This means that the exact figures for the highest counts are not shown. The exact value of the maximum count has little relevance to allergy sufferers, as the threshold value for a high birch pollen count is as low as 70 pollen particles per m3. The graph clearly shows the pollen count as being significantly 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 counts in 2021 in Bern, in comparison with the 30-year average from long-series data taken between 1991 and 2020. 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 count for hazel pollen on 11 days. This value is significantly higher than that of an average pollen season, shown by the blue box. However, there have been even more severe years over the 30-year comparison period, with seasons containing up to 20 days with high pollen counts.