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Introduction

Authors
Affiliations
Michigan Technological University
UC Davis
University of Maryland, College Park
University of California - Berkeley
Michigan Technological University
Brookhaven National Laboratory
The University of Miami (Florida)
United States Air Force
Argonne National Laboratory
The University of Alabama in Huntsville
Brookhaven National Laboratory
Pacific Northwest National Laboratory
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Introduction

What is the relationship between aerosol concentration, clouds, and precipitation?

Today we analyze a convection event and the associated heavy precipitation that occurred at the BNF site from 2025‑05‑08 to 2025‑05‑11.
Our workflow is organized as follows:

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Why Aerosols and Clouds Matter

Aerosols act as cloud condensation nuclei (CCN), altering cloud properties and precipitation:

  1. More and Smaller CCN

    • ↑ CCN number → same water mass spreads over more droplets → droplets shrink in size

  2. Reflecting More Sunlight (Twomey Effect)

    • Smaller droplets → larger total surface area → ↑ cloud albedo → more solar radiation is scattered back to space

  3. Lifetime Effect

    • Smaller droplets collide less efficiently → suppressed rainfall → extended cloud lifetime → further cooling
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cite: SMPS: Kuang, C., Singh, A., Howie, J., Salwen, C., & Hayes, C. Scanning mobility particle sizer (AOSSMPS), 2025-05-08 to 2025-05-11, Bankhead National Forest, AL, USA; Long-term Mobile Facility (BNF), Bankhead National Forest, AL, AMF3 (Main Site) (M1). Atmospheric Radiation Measurement (ARM) User Facility. Kuang et al. (2021)

CPCU: Shilling, J., Levin, M., & Zawadowicz, M. ACSM, corrected for composition- dependent collection efficiency (ACSMTOFCDCE), 2025-05-08 to 2025-05-11, Bankhead National Forest, AL, USA; Long-term Mobile Facility (BNF), Bankhead National Forest, AL, AMF3 (Main Site) (M1). Atmospheric Radiation Measurement (ARM) User Facility. Shilling et al. (2022)

CPCf: Koontz, A., Kuang, C., Andrews, E., Hayes, C., Singh, A., & Salwen, C. Condensation Particle Counter (AOSCPCF), 2025-05-08 to 2025-05-11, Bankhead National Forest, AL, USA; Long-term Mobile Facility (BNF), Bankhead National Forest, AL, AMF3 (Main Site) (M1). Atmospheric Radiation Measurement (ARM) User Facility. Koontz et al. (2013)

ACSM: Shilling, J., Levin, M., & Zawadowicz, M. ACSM, corrected for composition- dependent collection efficiency (ACSMTOFCDCE), 2025-05-08 to 2025-05-11, Bankhead National Forest, AL, USA; Long-term Mobile Facility (BNF), Bankhead National Forest, AL, AMF3 (Main Site) (M1). Atmospheric Radiation Measurement (ARM) User Facility. Shilling et al. (2022)

References
  1. Kuang, C., Singh, A., Howie, J., Salwen, C., & Hayes, C. (2021). Scanning Mobility Particle Sizer, b1 level. Atmospheric Radiation Measurement (ARM) Archive, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (US); ARM Data Center, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). 10.5439/1476898
  2. Shilling, J., Levin, M., & Zawadowicz, M. A. (2022). acsmtofcdce.c1: Aerosol Chemical Speciation Monitor Time-Of-Flight Composition-Dependent Collection Efficiency. Atmospheric Radiation Measurement (ARM) Archive, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (US); ARM Data Center, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). 10.5439/1878136
  3. Koontz, A., Kuang, C., Andrews, E., Hayes, C., Singh, A., & Salwen, C. (2013). aoscpcf.b1. Atmospheric Radiation Measurement (ARM) Archive, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (US); ARM Data Center, Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). 10.5439/1352536
Aerosol Cloud Interactions Deposition (ACID)
Cloud Condensation Nuclei Plots