Red particles indicate high precursor accumulation.
Five particles were released from each source every two hours, and were tracked for five days. The calculation of the particle transport was done using the Eulerian wind fields generated from the National Meteorological Centers Nested Grid Model with 180 km resolution. These emission fields contained point and area sources, and were transformed to the meteorological grid used by the wind fields. At each time step, the precursor emissions from each grid cell were evenly distributed to all particles that were within the grid cell. The simulation clearly illustrates that synoptic-scale weather systems tend to accumulate precursors in stagnation and convergence zones.