scholarly journals Final technical report on SciDac Award Expanding the computational frontier of multi-scale atmospheric simulation to advance understanding of low cloud feedbacks

2020 ◽  
Author(s):  
Michael Pritchard
Keyword(s):  
Cloud Feedbacks ◽  
Multi Scale ◽  
Technical Report ◽  
Low Cloud

scholarly journals On the relationship between low cloud variability and lower tropospheric stability in the Southeast Pacific

2011 ◽  
Vol 11 (2) ◽  
pp. 3777-3811
Author(s):  
F. Sun ◽  
A. Hall ◽  
X. Qu
Keyword(s):  
Climate Change ◽  
Seasonal Cycle ◽  
Austral Summer ◽  
Cloud Amount ◽  
Anthropogenic Climate Change ◽  
Cloud Feedbacks ◽  
Southeast Pacific ◽  
Low Cloud ◽  
Lower Tropospheric Stability ◽  
The Relationship

Abstract. In this study, we examine observed marine low cloud variability in the southeast Pacific and its association with lower-tropospheric stability (LTS) across a spectrum of timescales. On both daily and interannual timescales, LTS and low cloud amount are very well correlated in austral summer (DJF). Meanwhile in winter (JJA), when ambient LTS increases, the LTS-low cloud relationship disintegrates. The DJF LTS-low cloud relationship also weakens in years with unusually large ambient LTS values. These are generally strong El Niño years, in which DJF LTS values are comparable to those typically found in JJA. Thus the LTS-low cloud relationship is strongly modulated by the seasonal cycle and the ENSO phenomenon. We also investigate the origin of LTS anomalies closely associated with low cloud variability during austral summer. We find that the ocean and atmosphere are independently involved in generating anomalies in LTS and hence variability in the southeast Pacific low cloud deck. This highlights the coupled nature of the climate system in this region, and raises the possibility of cloud feedbacks related to LTS. We conclude by addressing the implications of the observed LTS-low cloud relationship in the southeast Pacific for low cloud feedbacks in anthropogenic climate change.

Low-Cloud Feedbacks from Cloud-Controlling Factors: A Review

2017 ◽  
pp. 135-157 ◽  
Author(s):  
Stephen A. Klein ◽  
Alex Hall ◽  
Joel R. Norris ◽  
Robert Pincus
Keyword(s):  
Controlling Factors ◽  
Cloud Feedbacks ◽  
Low Cloud

scholarly journals The Strength of Low-Cloud Feedbacks and Tropical Climate: A CESM Sensitivity Study

2019 ◽  
Vol 32 (9) ◽  
pp. 2497-2516 ◽  
Author(s):  
Ehsan Erfani ◽  
Natalie J. Burls
Keyword(s):  
Climate Sensitivity ◽  
Cloud Cover ◽  
Hydrological Cycle ◽  
Tropical Climate ◽  
Cloud Feedback ◽  
Cloud Feedbacks ◽  
Feedback Strength ◽  
Low Cloud ◽  
Low Cloud Cover ◽  
The Impact

Abstract Variability in the strength of low-cloud feedbacks across climate models is the primary contributor to the spread in their estimates of equilibrium climate sensitivity (ECS). This raises the question: What are the regional implications for key features of tropical climate of globally weak versus strong low-cloud feedbacks in response to greenhouse gas–induced warming? To address this question and formalize our understanding of cloud controls on tropical climate, we perform a suite of idealized fully coupled and slab-ocean climate simulations across which we systematically scale the strength of the low-cloud-cover feedback under abrupt 2 × CO2 forcing within a single model, thereby isolating the impact of low-cloud feedback strength. The feedback strength is varied by modifying the stratus cloud fraction so that it is a function of not only local conditions but also global temperature in a series of abrupt 2 × CO2 sensitivity experiments. The unperturbed decrease in low cloud cover (LCC) under 2 × CO2 is greatest in the mid- and high-latitude oceans, and the subtropical eastern Pacific and Atlantic, a pattern that is magnified as the feedback strength is scaled. Consequently, sea surface temperature (SST) increases more in these regions as well as the Pacific cold tongue. As the strength of the low-cloud feedback increases this results in not only increased ECS, but also an enhanced reduction of the large-scale zonal and meridional SST gradients (structural climate sensitivity), with implications for the atmospheric Hadley and Walker circulations, as well as the hydrological cycle. The relevance of our results to simulating past warm climate is also discussed.

scholarly journals Simulating the Role of Subtropical Stratocumulus Clouds in Driving Pacific Climate Variability

2014 ◽  
Vol 27 (13) ◽  
pp. 5119-5131 ◽  
Author(s):  
Katinka Bellomo ◽  
Amy Clement ◽  
Thorsten Mauritsen ◽  
Gaby Rädel ◽  
Bjorn Stevens
Keyword(s):  
Climate Variability ◽  
General Circulation ◽  
Large Scale ◽  
Circulation Model ◽  
Cloud Feedback ◽  
Decadal Climate Variability ◽  
Cloud Feedbacks ◽  
Southeast Pacific ◽  
Low Cloud ◽  
Pacific Climate Variability

This study examines the influence of the northeast and southeast Pacific subtropical stratocumulus cloud regions on the modes of Pacific climate variability simulated by an atmospheric general circulation model (ECHAM6) coupled to a slab ocean. The sensitivity of cloud liquid water to underlying SST is changed in the radiation module of the atmospheric model to increase the strength of positive low-cloud feedback in the two regions. Enhanced low-cloud feedback increases the persistence and variance of the leading modes of climate variability at decadal and longer time scales. Additional integrations show that the southeast Pacific influences climate variability in the equatorial ENSO region, whereas the effects of the northeast Pacific remain confined to the North Pacific. The results herein suggest that a positive feedback among SST, cloud cover, and large-scale atmospheric circulation can explain decadal climate variability in the Pacific Ocean. In particular, cloud feedbacks over the subtropical stratocumulus regions set the time scale of climate variability. A proper representation of low-level cloud feedbacks in the subtropical stratocumulus regions could therefore improve the simulation of Pacific climate variability.

scholarly journals Observed Sensitivity of Low-Cloud Radiative Effects to Meteorological Perturbations over the Global Oceans

2020 ◽  
Vol 33 (18) ◽  
pp. 7717-7734
Author(s):  
Ryan C. Scott ◽  
Timothy A. Myers ◽  
Joel R. Norris ◽  
Mark D. Zelinka ◽  
Stephen A. Klein ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Speed ◽  
Relative Humidity ◽  
Surface Temperature ◽  
Sea Surface ◽  
Cloud Feedbacks ◽  
Low Level ◽  
Low Clouds ◽  
Low Cloud ◽  
Global Oceans

AbstractUnderstanding how marine low clouds and their radiative effects respond to changing meteorological conditions is crucial to constrain low-cloud feedbacks to greenhouse warming and internal climate variability. In this study, we use observations to quantify the low-cloud radiative response to meteorological perturbations over the global oceans to shed light on physical processes governing low-cloud and planetary radiation budget variability in different climate regimes. We assess the independent effect of perturbations in sea surface temperature, estimated inversion strength, horizontal surface temperature advection, 700-hPa relative humidity, 700-hPa vertical velocity, and near-surface wind speed. Stronger inversions and stronger cold advection greatly enhance low-level cloudiness and planetary albedo in eastern ocean stratocumulus and midlatitude regimes. Warming of the sea surface drives pronounced reductions of eastern ocean stratocumulus cloud amount and optical depth, and hence reflectivity, but has a weaker and more variable impact on low clouds in the tropics and middle latitudes. By reducing entrainment drying, higher free-tropospheric relative humidity enhances low-level cloudiness. At low latitudes, where cold advection destabilizes the boundary layer, stronger winds enhance low-level cloudiness; by contrast, wind speed variations have weak influence at midlatitudes where warm advection frequently stabilizes the marine boundary layer, thus inhibiting vertical mixing. These observational constraints provide a framework for understanding and evaluating marine low-cloud feedbacks and their simulation by models.

Low-level cloud feedbacks in CMIP6 models and EUREC4A observations

2020 ◽  
Author(s):  
Anna Lea Albright ◽  
Sandrine Bony ◽  
Jean-Louis Dufresne ◽  
Jessica Vial
Keyword(s):  
Time Series ◽  
Global Warming ◽  
Simple Model ◽  
Vertical Structure ◽  
Controlling Factors ◽  
Cloud Feedbacks ◽  
Low Level ◽  
Low Cloud ◽  
Profile Changes ◽  
Cloud Response

<p>How will low-level clouds respond to global warming? We approach this question by first investigating the spread of climate sensitivity and cloud feedbacks in CMIP6 models. We stratify the cloud response by circulation regime and focus in greater detail on the cloud response in tropical regimes of subsidence and weak ascent  (i.e., their vertical structure in the present-day and future climate, how cloud profile changes relate to changes in cloud-controlling factors). This CMIP6 model analysis dovetails with an observational analysis of low cloud responses from the EUREC4A field campaign. We seek to employ a simple model of low cloud behavior, constrained with observations from EUREC4A and longer time series from the Barbados Cloud Observatory, to better constrain the range of low cloud behavior spanned by CMIP6 models. </p>

scholarly journals Cloud Feedbacks from CanESM2 to CanESM5.0 and their Influence on Climate Sensitivity

2021 ◽  
Author(s):  
John G. Virgin ◽  
Christopher G. Fletcher ◽  
Jason N. S. Cole ◽  
Knut von Salzen ◽  
Toni Mitovski
Keyword(s):  
Climate Sensitivity ◽  
Radiative Forcing ◽  
Coupled Model ◽  
Sea Surface ◽  
System Model ◽  
Surface Temperature Change ◽  
Cloud Optical Depth ◽  
Cloud Feedbacks ◽  
Low Cloud ◽  
Underlying Causes

Abstract. The newest iteration of the Canadian Earth System Model (CanESM5.0.3) has an Effective Climate Sensitivity (ECS) of 5.65 kelvin, which is a 54 % increase relative to the model's previous version (CanESM2 – 3.67 K), and the highest sensitivity of all current models participating in the sixth phase of the coupled model inter-comparison project (CMIP6). Here, we explore the underlying causes behind CanESM5's increased ECS via comparison of forcing and feedbacks between CanESM2 and CanESM5. We find only modest differences in radiative forcing as a response to CO2 between model versions. Through the use of cloud area fraction output and radiative kernels, we find that more positive shortwave cloud feedbacks – particularly with regards to low clouds across the equatorial pacific, as well as sub/extratropical free troposphere cloud optical depth – are the dominant contributors to CanESM5's increased climate sensitivity. Additional simulations with prescribed sea surface temperatures reveal that the spatial pattern of surface temperature change explains the pattern of change in low cloud fraction, but does not fully explain the increased ECS in CanESM5. The results from CanESM5 are consistent with increased ECS in several other CMIP6 models, which has been primarily attributed to changes in shortwave cloud feedbacks.

scholarly journals The CGILS experimental design to investigate low cloud feedbacks in general circulation models by using single-column and large-eddy simulation models

2012 ◽  
Vol 4 (4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Minghua Zhang ◽  
Christopher S. Bretherton ◽  
Peter N. Blossey ◽  
Sandrine Bony ◽  
Florent Brient ◽  
...  
Keyword(s):  
Experimental Design ◽  
Large Eddy Simulation ◽  
General Circulation ◽  
Simulation Models ◽  
General Circulation Models ◽  
Cloud Feedbacks ◽  
Eddy Simulation ◽  
Large Eddy ◽  
Single Column ◽  
Low Cloud
Sign in / Sign up

Export Citation Format

Share Document