Physical and Chemical Properties of Aerosol Particles in the Rural Area Near Houston, Texas
JING LI, Jiaoshi Zhang, Xianda Gong, Steven Spielman, Chongai Kuang, Ashish Singh, Maria Zawadowicz, Lu Xu, Jian Wang,
Washington University in St. Louis Abstract Number: 587
Working Group: Aerosols, Clouds and Climate
AbstractConvective clouds play a critical role in the Earth’s climate system. While theoretical and modeling studies have shown that aerosols could have a strong impact on convection, robust observational quantification of an aerosol effect on convective clouds remains elusive. The Tracking Aerosol Convection Interactions ExpeRiment (TRACER) campaign took place in the greater Houston area from 2021 to 2022, with the main objective of providing observations of convective clouds over a broad range of aerosol regimes. Here we present a comprehensive analysis of aerosol measurements conducted at a rural site southwest of Houston from June to September 2022 during the intensive observation period of the TRACER campaign. Based on the air mass back-trajectories, air masses arriving at the site were classified into three types, including (1) dominated by marine aerosols from the gulf, (2) strongly influenced by urban (i.e., Houston) emissions, and (3) mixtures of marine and continental aerosols. Among the three types, marine aerosols have the lowest number concentration (0.65 to 7.17 × 10
3 cm
-3) and PM
1 mass (1.28 to 9.04 μg m
-3), and they exhibit a bimodal size distribution. In comparison, air masses strongly influenced by urban emission show a unimodal aerosol size distribution and the highest number and PM
1 mass concentrations, 1.51 to 18.27 × 10
3 cm
-3 and 2.09 to 18.98 μg m
-3, respectively. For marine aerosols, sulfate represents the largest component of PM
1 mass (41%), while organics dominate the composition of aerosols strongly influenced by urban emissions. This is consistent with the observed higher hygroscopicity of marine aerosols. In all air mass types, elevated nucleation mode aerosol concentrations were observed around noon time, followed by particle growth, indicating new particle formation. Positive matrix factorization (PMF) analysis of aerosol mass spectrometry data was carried out to identify organic components. The major aerosol sources and their influences on aerosol size distribution, composition, and cloud condensation nuclei (CCN) concentration are discussed.