Open AccessEvolution of aerosol properties impacting visibility and direct climate forcing in an ammonia‐rich urban environment
Author(s) -
Langridge Justin M.,
Lack Daniel,
Brock Charles A.,
Bahreini Roya,
Middlebrook Ann M.,
Neuman J. Andrew,
Nowak John B.,
Perring Anne E.,
Schwarz Joshua P.,
Spackman J. Ryan,
Holloway John S.,
Pollack Ilana B.,
Ryerson Thomas B.,
Roberts James M.,
Warneke Carsten,
Gouw Joost A.,
Trainer Michael K.,
Murphy Daniel M.
Publication year - 2012
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 - 10.1029/2011jd017116
Subject(s) - aerosol , radiative forcing , environmental science , ammonium nitrate , nitrate , plume , atmospheric sciences , forcing (mathematics) , ammonium , relative humidity , environmental chemistry , extinction (optical mineralogy) , visibility , ammonia , trace gas , climatology , meteorology , chemistry , mineralogy , geography , organic chemistry , geology
Airborne measurements of sub‐micron aerosol and trace gases downwind of Los Angeles are used to investigate the influence of aging on aerosol properties relevant to climate forcing and visibility. The analysis focuses on the Los Angeles plume, which in addition to strong urban emissions is influenced by local agricultural emissions. Secondary organic aerosol formation and repartitioning of semi‐volatile ammonium nitrate were identified as key factors controlling the optical behavior observed. For one case study, ammonium nitrate contributed up to 50% of total dry extinction. At 85% relative humidity, extinction in the fresh plume was enhanced by a factor of ∼1.7, and 60–80% of this was from water associated with ammonium nitrate. On this day, loss of ammonium nitrate resulted in decreasing aerosol hygroscopicity with aging. Failing to account for loss of ammonium nitrate led to overestimation of the radiative cooling exerted by the most aged aerosol by ∼35% under dry conditions. These results show that changes to aerosol behavior with aging can impact visibility and climate forcing significantly. The importance of ammonium nitrate and water also highlight the need to improve the current representation of semi‐volatile aerosol species in large‐scale climate models.