Evaluating and Constraining Models’ Stratocumulus and Cumulus Cloud Feedbacks in the Tropics using Satellite Observations to Reduce Uncertainties in Future Climate Projections

Lead PI: Dr. Gregory V Cesana , Prof. Robert Pincus

Unit Affiliation: Center for Climate Systems Research (CCSR)

Unit Affiliation: Lamont-Doherty Earth Observatory (LDEO)

September 2020 - August 2021
Pacific Ocean ; Atlantic Ocean ; Indian Ocean
Project Type: Research

DESCRIPTION: In this project, we propose to use a new observational constraint derived from CloudSat- Cloud-Aerosols Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) observations, which discriminate Sc from Cu clouds, in concert with three different methods to separate Sc- from Cu-dominated regimes, to:

• Evaluate the Sc and Cu cloud amount (geographical distributions and profiles) as simulated by coupled model intercomparison project phase 5 (CMIP5) and phase 6 (CMIP6) climate models as well as their associated radiative fluxes on a global scale.
• Characterize and evaluate the interannual variation of the Sc and Cu fraction (including the vertical change) in response to surface temperature forcings and their feedbacks.
• Investigate the relationships between cloud-controlling factors and each Sc-Cu cloud type in the observations and use it to not only evaluate how well they are replicated in CMIP5 and CMIP6 models (informing us on how well cloud processes are represented in the PBL parametrizations) but also to infer observationally-based future cloud feedbacks.
• Assess the impact of the Sc-Cu cloud partitioning and feedbacks on the ECS, analyze the mechanisms behind it and estimate an observationally-constrained ECS.
• Determine what type of the parametrizations in the planetary boundary layer (turbulence and convection) produce the most plausible Sc-Cu distribution, feedbacks and relationships with cloud-controlling factors and for what reasons (to provide better guidance for future model development).