Aerosol Enhancement in the Tropical Tropopause Layer

SHANG LIU, Troy Thornberry, Pengfei Yu, Sarah Woods, Karen Rosenlof, Ru-Shan Gao, Northeastern University

     Abstract Number: 57
     Working Group: Remote and Regional Atmospheric Aerosol

Abstract
As the main pathway for the transport of tropospheric air into the stratosphere, the tropical tropopause layer (TTL) largely determines the entry values for the materials entering the stratosphere. The properties of the TTL air and the processes occurring in the TTL thus affect the global stratosphere and climate. Aerosol particles play a critical role in the TTL through cloud formation and heterogeneous chemistry, influencing the radiative and chemical balance of the stratosphere. However, aerosol measurements in the TTL are sparse, resulting in poor knowledge of aerosol abundance and distribution in this important region. To gain a deeper insight into the abundance, spatial distribution, and formation mechanisms of TTL aerosols, we carried out aircraft measurements of aerosols over the western Pacific warm pool during the Pacific Oxidants, Sulfur, Ice, Dehydration, and cONvection (POSIDON) campaign in October 2016 using the NASA WB-57F high-altitude aircraft stationed in Guam. To complement the measurements, we employed the CESM-CARMA model to obtain insights into the chemical composition of the aerosols. The combined approach of aerosol measurements, tracer analysis, and modeling offers insight into aerosol abundance and formation mechanisms within the TTL. Our measurements reveal a persistent and altitude-dependent enhancement of aerosol mass in the TTL compared to the convectively influenced troposphere below. Notably, our data demonstrate a striking positive correlation between aerosol mass and ozone. Model simulations suggest that organic materials constitute a substantial fraction of the total aerosol mass within the TTL. We further derived an empirical parameterization of TTL aerosol mass as a function of ozone based on their linear relationship. This framework holds potential for estimating the TTL aerosol abundance but requires further validation and refinement through future measurements. The work has been published in Geophysical Research Letters in 2024.