Ponente
Descripción
The National Oceanic and Atmospheric Administration (NOAA) National Air Quality Forecast Capability (NAQFC) utilizes the offline-coupled Global Forecast System (GFS) with the Community Multiscale Air Quality (CMAQ) modeling system (GFS-CMAQ). Although NAQFC has used carbon-bond (CB) series mechanisms, its capability of deploying different mechanisms for operational forecasting has not been demonstrated. In this work, we configured an experimental version of NAQFC, driven by meteorological forecast from GFS v15, to drive CMAQ v5.3.1 for four representative months (January, April, July, and October) in 2019. GFS-CMAQ simulations with the mechanisms of CB6r3_AE6/7, RACM2_AE6, SAPRC07tc_AE6, and SAPRC07tic_AE6i/7i are intercompared to assess the underlying causes of their different performance and to identify further needs in reducing the biases in predictions of ozone, aerosol, and their key precursors. RACM2 and SAPRC07 give higher O3 predictions comparing to CB6r3, due to the difference in reaction rate constants and photolysis rates. While RACM2 gives lower formaldehyde than CB6r3 due to a higher photolysis rate, SAPRC07 gives higher formaldehyde than RACM2 and CB6r3 due to greater chemical production. RACM2 coupled with AE6 aerosol mechanism yields overall higher secondary organic aerosol (SOA) and inorganic aerosols than CB6r3_AE6 due to its higher OH radical concentrations, except in the Southeast due to a lack of the reactive uptake of dicarbonyls. The implementation of detailed isoprene chemistry in SAPRC07tic_AE6i increases O3 and aerosol concentrations compared to S07tc_AE6. The updates of monoterpene-SOA in the AERO7 aerosol mechanism increase biogenic SOA significantly. Excluding potential SOA from combustion from the residential wood combustion emissions largely reduces the overprediction of organic carbon during cooler months. This work demonstrates the forecasting capability of various gas-phase and aerosol mechanisms in CMAQ v5.3.1, and identifies the key factors in causing biases for future development and improvement of NAQFC.
