A004-0010
Ice nucleating particles variability at a high elevation tropical monitoring station: atmospheric boundary layer vs. free troposphere
Monday, 7 December 2020
Poster
Camila Rodriguez-Gomez1, Javier Miranda2, Harry Alvarez3, Giovanni Alberto Carabali-Sandoval Sr3, Diego Cabrera1, Graciela B. Raga4, José Villanueva1, Irma Rosas3, Dara Salcedo5, Michel Grutter6 and Luis Ladino7, (1)Universidad Nacional Autonoma de Mexico, Atmospheric science centre, Mexico City, Mexico, (2)Universidad Nacional Autonoma de Mexico, Physics institute, Mexico City, Mexico, (3)Universidad Nacional Autonoma de Mexico, Mexico City, Mexico, (4)Centro de Ciencias de la Atmósfera, Universidad Nacional Autonoma de Mexico, Mexico City, Mexico, (5)UNAM - Campus Juriquilla, Queretaro, Mexico, (6)Universidad Nacional Autónoma de México, Centro de Ciencias de la Atmósfera, Mexico City, Mexico, (7)Universidad Nacional Autónoma de México, Centre of Atmospheric Sciences, Mexico City, Mexico
Abstract:
Mexico´s City megalopolis (MCM) is one of the most populous cities in North America. Similarly to other cities in the world, the MCM precipitation pattern is changing with time. Mixed-phase clouds provides the majority of the continental precipitation being a fundamental aspect of the hydrological cycle. Such clouds are composed of ice crystals and supercooled water droplets, formed by the presence of ice nucleating particles (INPs) and cloud condensation nuclei, respectively. Therefore, it is important to understand the variability, chemical composition, and sources of the INPs in the MCM to reduce uncertainties of the impacts of locally emitted and transported particles in mixed-phase cloud formation and the precipitation development.
The high-altitude, monitoring station in Altzomoni (~ 4,000 m a.s.l. and 50 km ESE of Mexico City) is exposed to boundary layer air from MCM as well as to free tropospheric air. Samples were collected between April 2019 and February 2020, under different conditions, e.g., cold fronts, biomass burning, summer, and rainy season. Aerosol particle concentration, size distribution, chemical composition, and INP concentrations were analyzed in the collected samples.
The aerosol chemical composition was found to be significantly different between the sampling periods. As expected, the lowest particle concentration was found during the rainy season, while the highest particle concentration was measured during the episodes of biomass burning. The all-seasons average INP concentration for all seasons varied from 0.1 L⁻¹ (-15°C) to 20 L⁻¹ (-30°C), with higher values found in the boundary layer air at temperatures above -15°C. Our results indicate that aerosol particles emitted from the MCM have the potential to impact cloud formation.
