TRACERO3

TRACER-Sonde: O3 as a tracer for convective mixing

1 July 2022 - 31 August 2022

Lead Scientist: Paul Walter

Observatory: AMF (ARM Mobile Facility 1) - HOU

The ARM Tracking Aerosol Convection Interactions ExpeRiment (TRACER) set for Houston, April 2021-April 2022, will investigate convective cloud life cycles and aerosol-convection interactions through a comprehensive data collection. Measurements taken as part of the TRACER-Sonde ARM field campaign (July-August 2021) will allow for a more extensive evaluation of the boundary layer and free troposphere conditions and provide vertical context for the ground-based measurements at AMF1. TRACER-Sonde also supports the science objectives of ASR/ARM project TRACER-MAP, to map aerosol processes across Houston during convective cell events.

The intensive period is based on previous field experiments and local knowledge from the PI team combined with the convective cell frequency documented by the TRACER PI team. The convective cell frequency is higher in June and July, while frontal passages start to become more common in August-September in Houston. Conversely, the timing of highest oxidizing conditions (as noted by high ozone and high secondary organic aerosol) due to recirculation of local air masses is August-September. In order to characterize convective mixing during both regimes of the four-month TRACER intensive operational period (IOP), the July-August window has been targeted.

These profiles will provide a chemical profile of the atmosphere, which can be used as an additional method to validate boundary-layer height determinations, and vertical mixing in pre- and post-storm environments. The TRACER Science Plan notes that “the isolated cells that form under onshore flow conditions occur when the boundary layer is growing during the daytime and can be considered relatively well mixed such that surface aerosol may be relatively more representative of cloud-base conditions than during the morning or night”. By launching electrochemical concentration cell (ECC) ozonesondes twice daily during the TRACER-Sonde campaign, both pre-dawn and during the daytime, both the well-mixed assumption and the initialization conditions prior to convection can be verified.