Analysis of atmospheric dispersion of olive pollen in southern Spain using SILAM and HYSPLIT models

Abstract

SILAM atmospheric dispersion model and the HYSPLIT trajectory model were used to detect the source areas and calculate transport dynamics for airborne olive pollen observed in the city of Cordoba, southwest of Iberian Peninsula. The ECMWF weather data with 3-h time interval and spatial resolution of 25 × 25 km2 and 75 hybrid vertical levels were used as meteorological inputs in both models to produce a coherent set of results in order to compare these two different approaches. Seven episodes recorded before and after the local flowering season in 2006 were analyzed using both models. The results provided an indication of the origins of olive pollen recorded in the city of Cordoba, revealing the influence of three main source areas at specific periods. One area was located nearby, to the southwest of the city (early May), another in the south of the province (mid-May) and the third to the east (late May/early June). The SILAM model yielded more detailed and quantitative results when identifying olive pollen sources and charting transport dynamics. The results from the HYSPLIT trajectory approach and SILAM footprints were qualitatively similar. However, a weak point of back trajectories was their lower sensitivity to details of the transport, as well as the necessity of subjective analysis of the trajectory plots, which were subject for possible misinterpretations. Information on both pollen source locations and local tree flowering phenology was required in order to ensure consistent analysis of the influence of olive sources for both models. Further than this, due to the fact that both models are widely used in other research areas, the results of this work could have a widespread range of application, such as to simulate the transport of radionuclides, e.g., in emergency preparedness exercises.