ams/awma_ PROCESS-BASED ANALYSIS OF THE ROLE OF THE GULF BREEZE IN SIMULATING OZONE CONCENTRATIONS ALONG THE EASTERN GULF COAST Sharon G. Douglas Jay L. Haney Ana R. Alvarez ICF Consulting/SAI San Rafael, California AMS/AWMA 11 th Joint Conference on Air Pollution Meteorology Paper 6.4

ams/awma_ Overview of the UAM-V Process Analysis Technique u Concept introduced by Jeffries and Tonnesen (1994) u As implemented in UAM-V, provides detailed information on the physical and chemical process that occur during a simulation u Process-level information includes – photochemical production/consumption – horizontal advection/diffusion – vertical advection – vertical diffusion – deposition – emissions (for precursor pollutants)

ams/awma_ Typical Uses of UAM-V Process Analysis u Model performance evaluation and diagnostic analysis u Examination of the response of the UAM-V modeling system to emission reductions u Obtaining an improved understanding of the modeling results through quantification of the various simulation processes

ams/awma_ Gulf Coast Ozone Study Modeling/Analysis Components u Episode selection (using an objective/regional optimization approach)  4 multi-day simulation periods u Detailed emission inventory preparation (incorporating data from participating states and industries) u Meteorological and photochemical modeling (using MM5 and an enhanced version of UAM-V) u Future-year modeling for 2005/Examination of regional and sub-regional attainment strategies u Corroborative analyses of observed data

ams/awma_ Gulf Coast Ozone Study UAM-V Modeling Domain Approximate process analysis subregion 4 km grid FL,AL,MS,LA Gulf Coast

ams/awma_ Simulated Process Contributions to Ozone for Pensacola: 16 September 1997 OzoneppbOzoneppb Hour Simulated — and observed ozone concentration

ams/awma_ Simulated Process Contributions to Ozone for Pensacola: 16 September 1997 OzoneppbOzoneppb Hour Simulated — and observed ozone concentration

ams/awma_ Simulated Process Contributions to Ozone for Pensacola: 16 September 1997 OzoneppbOzoneppb Hour Simulated — and observed ozone concentration

ams/awma_ Simulated Process Contributions to Ozone for Pensacola: 16 September 1997 OzoneppbOzoneppb Hour Simulated — and observed ozone concentration

ams/awma_ Simulated Process Contributions to Ozone for Pensacola: 16 September 1997 OzoneppbOzoneppb Hour Simulated — and observed ozone concentration Onset of the gulf breeze

ams/awma_ Simulated Process Contributions to Ozone for Pensacola: 16 September 1997 OzoneppbOzoneppb Hour Simulated — and observed ozone concentration Breakup of the nocturnal inversion

ams/awma_ Simulated Process Contributions to Ozone for Pensacola: 16 September 1997 OzoneppbOzoneppb Hour Simulated — and observed ozone concentration Ozone production reverses when the effective mixing height collapses

ams/awma_ Simulated Process Contributions to Ozone for Pensacola: 16 September 1997 OzoneppbOzoneppb Hour Simulated — and observed ozone concentration Advection of ozone by the gulf breeze appears to contribute to the sustained/secondary peak

ams/awma_ Simulated Process Contributions to Ozone for Pensacola: 16 September 1997 OzoneppbOzoneppb Hour Simulated — and observed ozone concentration

ams/awma_ KEY FINDINGS RELATED TO THE ROLE OF THE GULF BREEZE u MM5 produces a gulf breeze circulation (that is consistent with conceptual models) u Horizontal advection of ozone into the region by the gulf breeze contributes to the sustained/secondary ozone peak on 16 September (as well as several other of the simulation days) u Recirculation of ozone by the gulf breeze may explain why areas along the gulf coast are potential non- attainment areas for 8-hour ozone (but not for 1-hour ozone) — gulf breeze extends the period over which relatively high ozone concentrations occur

ams/awma_ OTHER KEY FINDINGS FROM USING PROCESS ANALYSIS AS PART OF GCOS u Vertical resolution of the UAM-V – there appears to be a point beyond which increased vertical resolution does not enhance representation of the meteorological/simulation processes – for the GCOS modeling platform, use of more than 8 model layers does not alter the relative contribution of simulation processes u Deposition – deposition becomes negligible under very light wind speed conditions – modified/enhanced the calculation of friction velocity (u * ) for use in the deposition algorithm