DROP

Dust and Regional Organic aerosol Profiling for Land-atmosphere Exchange and Transport for DUSTIEAIM (DROPLET-DUSTIEAIM)

1 October 2025 - 30 September 2026

Lead Scientist: Daniel Feldman

Observatory: AMF (ARM Mobile Facility 1)

The DROPLET experiment consists of three separate deployments of the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) User Facility tethered balloon system (TBS) between April 2026 and September 2026 in collaboration with ARM’s Desert-Urban System Integrated Atmospheric Monsoon (DUSTIEAIM) field campaign. DROPLET will focus on atmospheric and surface processes in the Phoenix, Arizona metropolitan area, and in particular focus on dust and other aerosols from urban and agricultural sources, as well as occasional wildfires and prescribed burning, with the latter an emerging means for managing the Sonoran Desert. Through the deployments of the TBS, DROPLET will collect data to enable the development of a quantitative understanding of particles sourced from within the region and those transported exogenously.  DROPLET will work with the Environmental Molecular Sciences Laboratory (EMSL) to measure the chemical composition and morphology of dust aerosol particles in the Phoenix metropolitan area to understand how these distinct sources impact radiation, clouds, and precipitation within the Earth energy system for the desert Southwestern (SW) U.S. These observations will help us understand the influence of local meteorology and particle physicochemical properties on how regional aerosols can be transported longer distances, including to the northeast where they impact the Colorado River Basin. These key observations are also required to understand which particles are present up to cloud base and are likely important for warm- and cold-phase cloud activation via their role as cloud condensation nuclei (CCN) and ice nucleating particles (INP). Single-particle imaging and chemical techniques at EMSL are critical components for this work.

Science Questions that DROPLET observations will help answer include:

• How often are the dust-containing particles coated with organic material from urban sources and processing such as secondary organic aerosol (SOA)?
• What size are the particles from different sources, e.g., urban versus rural versus agricultural versus wildland, and how does this change within the vertical profile?
• How prevalent are bioaerosols and are they internally mixed with other species?

DROPLET supports ARM’s mission to improve the understanding of clouds and aerosols, their interactions and coupling with the Earth’s surface and supports DUSTIEAIM Science Objectives: (1) land-atmosphere interactions and impacts and (2) aerosol processes and interactions. This campaign will also advance EMSL’s Environmental Transformations and Interactions Science Area focused on atmospheric aerosol predictive understanding.