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Title: Low-Cloud Feedback in CAM5-CLUBB: Physical Mechanisms and Parameter Sensitivity Analysis

Journal Article · · Journal of Advances in Modeling Earth Systems
DOI:https://doi.org/10.1029/2018MS001423· OSTI ID:1496795
ORCiD logo [1]; ORCiD logo [1];  [2];  [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [4]; ORCiD logo [3]; ORCiD logo [3];  [5]; ORCiD logo [6]
  1. School of Atmospheric SciencesNanjing University Nanjing China; Joint International Research Laboratory of Atmospheric and Earth System Sciences &, Institute for Climate and Global Change ResearchNanjing University Nanjing China
  2. State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid DynamicsInstitute of Atmospheric Physics, Chinese Academy of Sciences Beijing China
  3. Pacific Northwest National Laboratory Richland WA USA
  4. Department of Mathematical SciencesUniversity of Wisconsin‐Milwaukee Milwaukee WI USA
  5. Lawrence Livermore National Laboratory Livermore CA USA
  6. National Center for Atmospheric Research Boulder CO USA
+ Show Author Affiliations

The physical mechanism of low-cloud feedbacks is examined by using perturbed-parameter ensemble (PPE) experiments in a unified scheme of boundary layer turbulence and shallow convection, named Cloud Layers Unified by Binormals (CLUBB) coupled to Community Atmosphere Model version 5 (CAM5). The shortwave cloud feedbacks in CAM5-CLUBB are positive in the most stable tropical regime, which is related to the weaker turbulence in the planetary boundary layer (PBL) in a warmer climate that is possibly triggered by the strengthened stability of the cloud layer. The positive feedback between low cloud cover (LCC), cloud top radiative cooling and PBL turbulent mixing may further enhance the decrease in LCC. The stronger inversion stability of PBL partly counters the decrease in LCC, and a recently developed index, the estimated cloud-top entrainment index (ECTEI), is a better predictor for LCC changes than conventional stability indices. The relative strength of shallow convection increases in the warmer climate, but its effect on low-cloud feedback is complicated by the unified treatment of shallow convection and PBL turbulence in CLUBB. Stronger shallow convection means more convective drying, but also less PBL turbulence and less LCC in the present climate, which leads to less reduction in LCC. The parameters related to dynamic turbulent structure and double Gaussian closure in CLUBB are the most influential parameters on low-cloud feedbacks. Our results suggest that a unified treatment of shallow convection and turbulence may give rise to the predominate role of the PBL turbulent mixing in determining low-cloud feedback.

Research Organization:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Organization:
USDOE
DOE Contract Number:
AC05-76RL01830
OSTI ID:
1496795
Report Number(s):
PNNL-SA-139280
Journal Information:
Journal of Advances in Modeling Earth Systems, Vol. 10, Issue 11; ISSN 1942-2466
Publisher:
American Geophysical Union (AGU)
Country of Publication:
United States
Language:
English

References (54)

Elucidating Model Inadequacies in a Cloud Parameterization by Use of an Ensemble-Based Calibration Framework journal December 2007
Marine boundary layer clouds at the heart of tropical cloud feedback uncertainties in climate models journal January 2005
The vertical distribution of cloud feedback in coupled ocean-atmosphere models: VERTICAL DISTRIBUTION OF CLOUD FEEDBACK journal June 2011
Simulation of shallow cumuli and their transition to deep convective clouds by cloud-resolving models with different third-order turbulence closures journal January 2006
Multivariate Probability Density Functions with Dynamics in the GFDL Atmospheric General Circulation Model: Global Tests journal March 2014
Revealing differences in GCM representations of low clouds journal November 2009
Coupling between lower-tropospheric convective mixing and low-level clouds: Physical mechanisms and dependence on convection scheme: SHALLOW CONVECTIVE MIXING AND LOW-CLOUDS journal December 2016
On the contribution of local feedback mechanisms to the range of climate sensitivity in two GCM ensembles journal February 2006
Aquaplanets, Climate Sensitivity, and Low Clouds journal October 2008
A New Two-Moment Bulk Stratiform Cloud Microphysics Scheme in the Community Atmosphere Model, Version 3 (CAM3). Part I: Description and Numerical Tests journal August 2008
A PDF-Based Model for Boundary Layer Clouds. Part I: Method and Model Description journal December 2002
Positive tropical marine low‐cloud cover feedback inferred from cloud‐controlling factors journal September 2015
How may low‐cloud radiative properties simulated in the current climate influence low‐cloud feedbacks under global warming? journal October 2012
CGILS: Results from the first phase of an international project to understand the physical mechanisms of low cloud feedbacks in single column models: CGILS Results On Low Cloud Feedback journal December 2013
Interpretation of Factors Controlling Low Cloud Cover and Low Cloud Feedback Using a Unified Predictive Index journal November 2017
Sensitivity of climate simulations to the parameterization of cumulus convection in the Canadian climate centre general circulation model journal September 1995
Monte Carlo and quasi-Monte Carlo methods journal January 1998
Global simulations of ice nucleation and ice supersaturation with an improved cloud scheme in the Community Atmosphere Model journal January 2010
Shallowness of tropical low clouds as a predictor of climate models’ response to warming journal October 2015
Small-Scale and Mesoscale Variability in Cloudy Boundary Layers: Joint Probability Density Functions journal December 2002
Parametric behaviors of CLUBB in simulations of low clouds in the Community Atmosphere Model (CAM): PARAMETRIC BEHAVIORS OF CLUBB IN CAM journal July 2015
Using Probability Density Functions to Derive Consistent Closure Relationships among Higher-Order Moments journal April 2005
Interactions between Hydrological Sensitivity, Radiative Cooling, Stability, and Low-Level Cloud Amount Feedback journal March 2018
A PDF-Based Model for Boundary Layer Clouds. Part II: Model Results journal December 2002
Using a Multiphysics Ensemble for Exploring Diversity in Cloud–Shortwave Feedback in GCMs journal August 2012
Unified parameterization of the planetary boundary layer and shallow convection with a higher-order turbulence closure in the Community Atmosphere Model: single-column experiments journal January 2012
Mechanisms of marine low cloud sensitivity to idealized climate perturbations: A single-LES exploration extending the CGILS cases: LES OF BOUNDARY-LAYER CLOUD FEEDBACK journal May 2013
Intercomparison and interpretation of climate feedback processes in 19 atmospheric general circulation models journal January 1990
Interpretation of Cloud-Climate Feedback as Produced by 14 Atmospheric General Circulation Models journal August 1989
Higher-Order Turbulence Closure and Its Impact on Climate Simulations in the Community Atmosphere Model journal December 2013
Observed vertical structure of tropical oceanic clouds sorted in large-scale regimes journal January 2008
The Seasonal Cycle of Low Stratiform Clouds journal August 1993
On the Relationship between Stratiform Low Cloud Cover and Lower-Tropospheric Stability journal December 2006
A sensitivity analysis of cloud properties to CLUBB parameters in the single-column Community Atmosphere Model (SCAM5) journal August 2014
On the interpretation of inter-model spread in CMIP5 climate sensitivity estimates journal March 2013
PDF Parameterization of Boundary Layer Clouds in Models with Horizontal Grid Spacings from 2 to 16 km journal January 2012
An important constraint on tropical cloud - climate feedback: TROPICAL CLOUD-CLIMATE FEEDBACK journal October 2002
Lower-Tropospheric Mixing as a Constraint on Cloud Feedback in a Multiparameter Multiphysics Ensemble journal September 2016
Quantifying Climate Feedbacks Using Radiative Kernels journal July 2008
Uncertainty quantification and parameter tuning in the CAM5 Zhang-McFarlane convection scheme and impact of improved convection on the global circulation and climate: PARAMETERS TUNING IN CAM5 AND ITS IMPACT journal January 2013
Error Reduction and Convergence in Climate Prediction journal December 2008
Spread in model climate sensitivity traced to atmospheric convective mixing journal January 2014
Coupling between subtropical cloud feedback and the local hydrological cycle in a climate model journal December 2012
Why is longwave cloud feedback positive? journal January 2010
On the Use of Cloud Forcing to Estimate Cloud Feedback journal October 2004
Insights into low-latitude cloud feedbacks from high-resolution models journal November 2015
The impact of parametrized convection on cloud feedback
  • Webb, Mark J.; Lock, Adrian P.; Bretherton, Christopher S.
  • Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, Vol. 373, Issue 2054 https://doi.org/10.1098/rsta.2014.0414
journal November 2015
Cloud feedback mechanisms and their representation in global climate models: Cloud feedback mechanisms and their representation in GCMs journal May 2017
On dynamic and thermodynamic components of cloud changes journal March 2004
The eastward shift of the Walker Circulation in response to global warming and its relationship to ENSO variability journal March 2014
A New Two-Moment Bulk Stratiform Cloud Microphysics Scheme in the Community Atmosphere Model, Version 3 (CAM3). Part II: Single-Column and Global Results journal August 2008
Parametric sensitivity analysis of precipitation at global and local scales in the Community Atmosphere Model CAM5 journal April 2015
Subtropical Low Cloud Response to a Warmer Climate in a Superparameterized Climate Model. Part I: Regime Sorting and Physical Mechanisms: REGIME SORTING AND PHYSICAL MECHANISMS journal March 2009
Low cloud reduction in a greenhouse-warmed climate: Results from Lagrangian LES of a subtropical marine cloudiness transition: LAGRANGIAN BOUNDARY-LAYER CLOUD FEEDBACK journal February 2014

Cited By (2)

Review of Chinese atmospheric science research over the past 70 years: Atmospheric physics and atmospheric environment journal November 2019
The Single Column Atmosphere Model Version 6 (SCAM6): Not a Scam but a Tool for Model Evaluation and Development journal May 2019

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Related Subjects

CAM5
Cloud Layers Unified by Binormals (CLUBB)