Movie: Ozone precursor transport simulation using the CAPITA Monte Carlo model

Description:

This is a simulation of the transport of ozone precursors over the Eastern US. It is similar to the flow visualization movie: Flow visualization with the CAPITA Monte Carlo model; however, the particles have been colored based on the cummulative weighted sum of the particle's VOC and NOX mass, i.e., "ozone" mass = VOC+6*NOX. At each time step the particle's mass is increased in proportion to the cummulative emission rates from the 1985 NAPAP VOC and NOX emission inventory. Red particles indicate high precursor accumulation.

Purpose:

To simulate the continental scale transport of ozone precursor species, with particular emphasis on three-dimensional transport.

Method:

The transport simulation was created using the CAPITA Monte Carlo Model. Particles were released from sources uniformly distributed over the Eastern US. 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. The VOC and NOX mass for each particle was estimated from the 1985 NAPAP annual emission fields. 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.

Interpretation:

The simulation clearly illustrates that synoptic-scale weather systems tend to accumulate precursors in stagnation and convergence zones. On the other hand, weather fronts act like "shovels" that sweep out much of the continent. The vertical crossections indicate an almost "boiling" behavior in the lowest 4 km, with frequent "bubbles" escaping to the troposphere.

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