Modeling the dispersion of Ambrosia artemisiifolia L. pollen with the model system COSMO-ART

Abstract

Common ragweed (Ambrosia artemisiifolia L.) is a highly allergenic plant that is spreading throughout Europe. Ragweed pollen can be transported over large distances by the wind. Even low pollen concentrations of less than 10 pollen m(-3) can lead to health problems in sensitive persons. Therefore, forecasting the airborne concentrations of ragweed pollen is becoming more and more important for public health. The question remains whether distant pollen sources need to be considered in reliable forecasts. We used the extended numerical weather prediction system COSMO-ART to simulate the release and transport of ragweed pollen in central Europe. A pollen episode (September 12-16, 2006) in north-eastern Germany was modeled in order to find out where the pollen originated. For this purpose, several different source regions were taken into account and their individual impact on the daily mean pollen concentration and the performance of the forecast were studied with the means of a 2 × 2 contingency table and skill scores. It was found that the majority of the pollen originated in local areas, but up to 20% of the total pollen load came from distant sources in Hungary. It is concluded that long-distance transport should not be neglected when predicting pollen concentrations.

Fig. 1

Ragweed (Ambrosia artemisiifolia) distribution map for Germany, Austria, the Czech Republic, and Hungary, showing the percentage of the grid box covered with ragweed plants as used in the simulations

Fig. 2

Pollen monitoring sites in Germany. The stations that are mentioned in the text are 1 Berlin, 2 Dresden, 3 Garz, 4 Potsdam, and 5 Treuenbrietzen

Fig. 3

2 × 2 contingency table. Hits (a), misses (b), false alarms (c), and correct negatives (d) are summed in order to compute skill scores

Fig. 4

Simulated temperature and wind vectors on the lowest model level from September 13 to 16, 2006

Fig. 5

Simulated and measured pollen concentrations from September 13 to 16, 2006. Dots represent measurements, while the shaded area depicts the simulated concentration. The concentrations are given in daily mean values of pollen m⁻³ of air. The color scheme is the same for measurements and simulation. All available source regions (Germany, Austria, the Czech Republic, and Hungary) were used in the simulation

Fig. 6

Values of the 2 × 2 contingency table and skill scores for the 15 simulations (compare Table 2 for the different combinations of source regions). The threshold value for the pollen concentration was 1 pollen m⁻³. The uppermost panel shows the number of entities a, b, c, and d of the 2 × 2 contingency table. The 2nd panel shows the values of the skill scores Proportion Correct (PC) and Threat Score (TS). The 3rd panel shows the values of the skill scores Bias (B), Hit Rate (H), and False Alarm Rate (F). The lowest panel shows the values of the Heidke Skill Score (HSS)