Magnitude and timescale of liquid water path adjustments to cloud droplet number concentration perturbations for nocturnal non-precipitating marine stratocumulus

Details

• Journal Title:
  Atmospheric Chemistry and Physics
• Personal Author:
  Chen, Yao-Sheng ; Prabhakaran, Prasanth ; Hoffmann, Fabian ; Kazil, Jan ; Yamaguchi, Takanobu ; Feingold, Graham
• NOAA Program & Office:
  OAR (Oceanic and Atmospheric Research) ; CIRES (Cooperative Institute for Research in Environmental Sciences) ; CSL (Chemical Sciences Laboratory)
• Description:
  Cloud liquid water path (L) adjusts to perturbations in cloud droplet number concentration (N) over time. We explore the magnitude and timescale of this adjustment in nocturnal non-precipitating marine stratocumuli using large eddy simulations of baseline conditions and aerosol seeding experiments for 22 meteorological conditions. The results confirm that the L adjustment (δL) slope (k) is more negative for simulation pairs with relatively low N and less negative for high N. Overall, k is unlikely to be lower than −0.4 within 24 h of seeding start, meaning the L adjustment is unlikely to fully offset the brightening due to the Twomey effect. After seeding, the δL becomes increasingly negative, which can be characterized by an exponential convergence. This evolution is governed by a short timescale around 5 h and lasts for around 8–12 h. It is driven by the feedback between entrainment, L, and boundary layer (BL) turbulence. Other processes, including radiation, surface fluxes, and subsidence, respond to the seeding weakly. This short timescale is insensitive to the amount of seeding, making the evolution of δL and some other deviations similar for different seeding amounts after appropriate scaling. The timescale of k evolution is closely related to the δL timescale and hence also short, while it could also be affected by the δN evolution. The results are most relevant to conditions where seeding is applied to a large area of marine stratocumulus in well-mixed and overcast BL where shear is not a primary source of turbulence.
• Source:
  Atmospheric Chemistry and Physics, 25(12), 6141-6159
• DOI:
  https://doi.org/10.5194/acp-25-6141-2025
• ISSN:
  1680-7324
• Format:
  pdf
• Publisher:
  Copernicus GmbH
• Document Type:
  Journal Article
• Funding:
  Grant no. NA17OAR4320101 ; Grant no. NA22OAR4320151
• License:
  https://creativecommons.org/licenses/by/4.0/
• Rights Information:
  CC BY
• Compliance:
  Submitted
• Main Document Checksum:
  urn:sha-512:73df8bfa32f6b6659a6b70a96710c4a93e3239b10d0eeb15e45ebd5739f58569aa169814fa96529c07a767ec663b88422e58e213e666a80f7778b130311091fd
• Download URL:
  https://repository.library.noaa.gov/view/noaa/71489/noaa_71489_DS1.pdf
• File Type:
  [PDF - 3.70 MB ]