A NUMERICAL-ANALYSIS OF LOS-ANGELES BASIN POLLUTION TRANSPORT TO THE GRAND-CANYON UNDER STABLY STRATIFIED, SOUTHWEST FLOW CONDITIONS

This paper presents a numerical investigation of air pollutant transpo rt from the Los Angeles Basin to Grand Canyon National Park (GCNP) und er the stably stratified wintertime, synoptic high-pressure conditions that existed during 10-13 February 1987. The Colorado State Universit y Regional Atmospheric Modeling System (CSU-RAMS) is used to develop f ields of different atmospheric variables for 54 simulated hours. These fields are applied in a Lagrangian particle dispersion model (LPDM) t o simulate the advection of pollutant particles for this period. It is found that under the generally southwest flow conditions presented, p articles released from the Los Angeles Basin will impact the Grand Can yon but only in small amounts. By comparing a flat to complex terrain simulation, the importance of the terrain features between Los Angeles and GCNP to the dispersion of Los Angeles Basin pollutants is made ob vious. Mountain barriers and undulating land reduce what could otherwi se be a very serious pollutant impact on GCNP. Based on these results the conclusion is made that despite southwest average flow aloft durin g the Winter Haze Intensive Tracer EXperiment (WHITEX) period of 10-13 February 1987, Los Angeles Basin pollution did not contribute signifi cantly to the observed visibility reduction in the Grand Canyon during that time period.