August 5, 2020 

The Environmental Predictions Department of The Cyprus Institute Climate and Atmosphere Research Center (CARE-C) has used the HYSPLIT model to track and forecast the potential atmospheric transport of pollution originating from the explosion of 4 August 2020 at Beirut, Lebanon.

In the HYSPLIT particle model, a fixed number of particles are advected about the model domain by the mean wind field and spread by a turbulent component. The model calculates a 3-dimensional particle distribution (horizontal and vertical).

The modelled meteorological conditions, including wind speed and direction, were used to calculate air parcel trajectories for 72 hours after the explosion. The trajectory ensemble includes multiple trajectories from the location of the explosion. Based on the model, air masses above the accident site were transported to the East and South of Lebanon.

Each member of the trajectory ensemble is calculated by offsetting the meteorological data by a fixed grid factor (one grid meteorological grid point in the horizontal and 0.01 sigma units in the vertical) based on the meteorological forecast of the GFS global model at 0.25 degrees resolution. This results in 27 members for all-possible offsets (shown with different colours). It is also worth mentioning that The Cyprus Institute used similar models to track and forecast the potential atmospheric transport of pollution in Mari and Fukushima cases.

Trajectory ensemble over 72 hours of atmospheric transport of air parcels originating from the 4 August 2020 explosion at Beirut, Lebanon: