Open AccessCharacterization of an eastern U.S. severe air pollution episode using WRF/Chem
Author(s) -
Yegorova E. A.,
Allen D. J.,
Loughner C. P.,
Pickering K. E.,
Dickerson R. R.
Publication year - 2011
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2010jd015054
Subject(s) - weather research and forecasting model , ozone , environmental science , nox , atmospheric sciences , air quality index , climatology , pollution , maxima , meteorology , geology , chemistry , physics , art , ecology , organic chemistry , performance art , art history , biology , combustion
On 8–11 July 2007 the eastern United States experienced a severe heat wave and smog event with maximum temperatures approaching 38°C and maximum 8 h average ozone mixing ratios of 125 ppbv. We examine this episode with observations and numerical simulations using the Weather Research and Forecasting model with online chemistry (WRF/Chem with RADM2). The general features of this severe smog event–a broad area of high pressure, weak winds and heavy pollution, terminated by the passage of a cold front–were well simulated by the model. WRF/Chem underpredicted O 3 maxima by 5–8 ppbv where air quality was poor, usually in the northeast, but overpredicted maxima by up to 16 ppbv where ozone amounts were low, usually in the southeast. Simulated O 3 vertical profiles over Beltsville, Maryland, showed good agreement with ozonesonde measurements, but the model boundary layer was too deep on 9 July, contributing to the low bias over this region. The representation of NO x chemistry in RADM2 may lead to an underestimation of NO x lifetime and is likely partially responsible for low O 3 biases in the most polluted area in the northeast. To simulate the maximum effect of nighttime multiphase NO y loss, we set the N 2 O 5 heterogeneous hydrolysis reaction rate constant to zero. This increased the mean bias outside the area of highest ozone concentration but substantially improved O 3 and NO y over most of the domain, especially in smoggy areas such as the rural, Pinnacles site.