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Aerosol-Cloud Interactions Centered on MAGIC: Insights from Measurements and Lagrangian Large Eddy Simulation

Active Dates 9/1/2023-8/31/2026
Program Area Atmospheric System Research
Project Description
Aerosol-Cloud Interactions Centered on MAGIC: Insights from Measurements and Lagrangian Large Eddy Simulation

Principal Investigator: Graham Feingold, NOAA Chemical Sciences Laboratory

Co-Investigators: Takanobu Yamaguchi, Yaosheng Chen, and Xiaoli Zhou, NOAA Chemical Sciences Laboratory/Cooperative Institute for Research in the Environmental Sciences, University of Colorado at Boulder

Unfunded collaborator: J. Christine Chiu, Colorado State University

Traditionally aerosol-cloud interactions have been separated into the “albedo effect” (brightening under constant cloud amount, characterized by both cloud liquid water path, and cloud fraction; Twomey 1974) and the “lifetime effect” (adjustments in cloud amount). The magnitudes of adjustments in liquid water path (LWP) and cloud fraction (CF) in marine boundary layer (MBL) clouds are poorly understood; both positive and negative adjustments have been documented (e.g., Albrecht 1989; Xue et al. 2008; Gryspeerdt et al. 2019). Positive adjustments tend to occur under conditions that are likely to precipitate, i.e., when the addition of aerosol particles suppresses precipitation and increases cloud amount. Negative adjustments appear to be prevalent in non-precipitating stratocumulus (Sc) when drop-size dependent evaporation reduces cloud amount (Wang et al. 2003; Ackerman et al. 2004; Bretherton et al. 2007). These negative adjustments have been demonstrated to offset the albedo effect very significantly, with cloud ‘darkening’ possible when losses in liquid water path and cloud fraction exceed certain thresholds (Glassmeier et al. 2021; Zhang et al. 2022; Zhang and Feingold 2023; Zheng, 2022). The cloud fraction adjustment is particularly poorly quantified, in part because cloud fraction is a quantity that is contingent on instrument detection limits and thresholds (Schwartz et al. 2017). Moreover, the timescales of both the liquid water path and cloud fraction adjustments over the course of the diurnal cycle have received very little attention. In this proposal we will address these cloud amount adjustments in the NE Pacific using a combination of Marine ARM (Atmospheric Radiation Measurement) GPCI Investigation of Clouds (MAGIC) ship-based data, large ensembles of realistic Lagrangian large eddy simulations (LESs), and satellite remote-sensing. MAGIC data will be used to enhance understanding of cloud processes in well-established geophysical variable spaces that are key to the problem. We will focus our attention on the extent to which aerosol perturbations both augment and offset the Twomey brightening by changing cloud amount, and the meteorological and cloud conditions in which these different responses occur. We will use this framework to evaluate the climate effect of aerosol-cloud interactions in one of the major stratocumulus decks, and provide constraints on the regional indirect effect simulated by climate models. We will also consider the effects of aerosol perturbations on the stratocumulus-to-cumulus transition.
Award Recipient(s)
  • NOAA/OAR (PI: Feingold, Graham)