TRACER-VNATS

The formation of 1 nm-sized atmospheric clusters is an important environmental nano-scale process, with field measurements and modeling studies indicating that freshly nucleated particles can contribute significantly to the global population of aerosol and cloud condensation nuclei (Kerminen et al. 2005; Kuang et al. 2009; Lihavainen et al. 2003; Merikanto et al. 2010). While there have been an increasing number of atmospheric cluster measurements from surface-based platforms, there have been very few measurements of the vertically-resolved ambient cluster size distribution from aerial platforms. Vertically-resolved atmospheric cluster measurements are needed because aerosol formation in the upper troposphere may be a significant source of cloud condensation nuclei (Chen et al. 2018; Wang et al. 2016). Furthermore, these vertically-resolved measurements are needed to: [1] connect the atmospheric conditions that drive atmospheric NPF with large-scale boundary layer transport processes and meteorology, and [2] evaluate the extent to which surface-based aerosol measurements are representative of the atmospheric aerosol aloft. The campaign seeks to develop process-level understanding for the formation and growth of atmospheric aerosol aloft, through vertically-resolved measurements of the atmospheric cluster number and size distribution. These observations will be carried out as part of the TRACER (Tracking Aerosol Convection Interactions Experiment) campaign, whose main objective is to provide high temporal and spatial resolution observations of convective clouds in the Houston region, over a broad range of environmental and aerosol regimes. An ancillary site (ANC) will be deployed during TRACER in a region that is expected to experience cleaner aerosol conditions and be more representative of the background atmospheric state for this region. Measurements of vertically resolved NPF at the ANC site will constrain an important background aerosol source, while measurements at the Smith Point site will constrain the role of NPF on aerosol that is representative of a maritime coastal environment strongly influenced by a bay breeze circulation. These vertically-resolved atmospheric cluster observations will be combined with observations of the atmospheric thermodynamics and meteorology to contextualize the evolution of boundary layer transport processes, including influences from the bay breeze, that control aerosol formation aloft. Furthermore, TBS-measurements of atmospheric state will provide the foundation for understanding boundary layer development, the influence of the bay breeze circulation and related cloud formation.

Timeline