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In August 2017, a smoke plume from wildfires in British Columbia and the Northwest Territories recirculated and persisted over northern Canada for over two weeks. We compared a full‐factorial set of NASA Goddard Institute for Space Studies ModelE simulations of the plume to satellite retrievals of aerosol optical depth and carbon monoxide, finding that ModelE performance was dependent on the model configuration, and more so on the choice of injection height approach, aerosol scheme and biomass burning emissions estimates than to the choice of horizontal winds for nudging. In particular, ModelE simulations with free‐tropospheric smoke injection, a mass‐based aerosol scheme and comparatively high fire NOxemissions led to unrealistically high aerosol optical depth. Using paired simulations with and without fire emissions, we estimated that for 16 days over an 850,000 km2region, the smoke decreased planetary boundary layer heights by between 253 and 547 m, decreased downward shortwave radiation by between 52 and 172 Wm−2, and decreased surface temperature by between 1.5°C and 4.9°C, the latter spanning an independent estimate from operational weather forecasts of a 3.7°C cooling. The strongest surface climate effects were for ModelE configurations with more detailed aerosol microphysics that led to a stronger first indirect effect. Smoke from biomass burning is known to have effects on surface weather. We used the NASA GISS ModelE to estimate these effects for a large 2017 smoke plume over northern Canada that persisted for two weeks. We first found that the height of the smoke release at the source was the most important factor influencing agreement between ModelE and satellite retrievals of aerosols and carbon monoxide, and that specific, plausible configurations of the model led to unrealistically high aerosol amounts. By comparing simulations with and without fire, we estimated a 16‐day cooling over a 850,000 km2region of between 1.5°C and 4.9°C, depending on the model configuration. We captured the overall pattern and magnitude of a large 2017 smoke plume over Canada with the NASA GISS ModelEOf the sixteen plausible model configurations tested under a full‐factorial design, two with higher NOxemissions, free‐tropospheric smoke release and mass‐based aerosols led to unrealistically high aerosol optical depthOver an 850,000 km2region, we estimated a 16‐day surface cooling of between 1.5°C and 4.9°C We captured the overall pattern and magnitude of a large 2017 smoke plume over Canada with the NASA GISS ModelE Of the sixteen plausible model configurations tested under a full‐factorial design, two with higher NOxemissions, free‐tropospheric smoke release and mass‐based aerosols led to unrealistically high aerosol optical depth Over an 850,000 km2region, we estimated a 16‐day surface cooling of between 1.5°C and 4.9°C

Shifts in Southern Ocean (SO, 40–85°S) shortwave cloud feedback (SWFB) toward more positive values are the dominant contributor to higher effective climate sensitivity (ECS) in Coupled Model Intercomparison Project Phase 6 (CMIP6) models. To provide an observational constraint on the SO SWFB, we use a simplified physical model to connect SO SWFBwith the response of column‐integrated liquid water mass (LWP) to warming and the susceptibility of albedo to LWP in 50 CMIP5 and CMIP6 GCMs. In turn, we predict the responses of SO LWP using a cloud‐controlling factor (CCF) model. The combination of the CCF model and radiative susceptibility explains about 50% of the variance in the GCM‐simulated SWFBin the SO. Observations of SW radiation fluxes, LWP, and CCFs from reanalysis are used to constrain the SO SWFB. Observations suggest a SO LWP increase in response to warming and albedo susceptibility to LWP that is on the lower end relative to GCMs. The overall constraint on the contribution of SO to global mean SWFBis −0.168 to +0.051 W m−2K−1, relative to −0.277 to +0.270 Wm−2 K−1. In summary, observations suggest SO SWFBis less likely to be as extremely positive as predicted by some CMIP6 GCMs, but more likely to range from moderately negative to weakly positive. Previous studies suggest that SO clouds reflect more sunlight in response to global warming and more strongly cool the planet ‐ a negative shortwave cloud feedback (SWFB). The SO SWFBin the latest generation of global climate models (GCMs) participating in the Coupled Model Intercomparison Project Phase 6 (CMIP6) has shifted toward more positive values, leading to the larger predicted temperature responses to greenhouse gas increases in these GCMs. In this study, we examine if this more positive SWFBis consistent with observations. We connect the effect of SO clouds on reflected sunlight with the predicted response of cloud liquid content to global warming. The linkage between cloud liquid water content and large‐scale meteorology is applied to predict this cloud liquid response. Satellite observations of reflected sunlight, cloud liquid, and observations of large‐scale meteorology are applied to constrain the SO SWFBfor 50 CMIP5 and CMIP6 GCMs. The results suggest that SO cloud liquid will increase with warming around the average of predictions of 50 GCMs. Satellite records suggest that SO SWFBis moderately negative to weakly positive, instead of extremely positive or negative as suggested by some GCMs. Southern Ocean liquid water path increased over the past two decades due to enhanced moisture convergenceEnhanced moisture convergence contributes to a negative cloud feedback in the Southern OceanAcross global climate models, the sensitivity of upwelling shortwave to cloud opposes the sensitivity of cloud to moisture convergence Southern Ocean liquid water path increased over the past two decades due to enhanced moisture convergence Enhanced moisture convergence contributes to a negative cloud feedback in the Southern Ocean Across global climate models, the sensitivity of upwelling shortwave to cloud opposes the sensitivity of cloud to moisture convergence

To improve cloud feedback understanding and simulation, observations have been used to quantify the rate of change of cloud radiative properties as a function of specific environmental metrics (or cloud controlling factors; CCFs). The study focuses on low‐level cloud dominated regions during 2006–2010. For each ocean gridpoint, Spearman's rank correlation coefficients of daily mean observed cloud fraction versus (a) 10‐m wind, (b) sensible heat flux (SHF), (c) sea surface temperature, (d) estimated inversion strength (EIS), (e) 850 hPa vertical velocity, and (f) the Mparameter (∆θskin800hPa${\increment}{\theta }_{\text{skin}}^{800\text{hPa}}$) are sorted to identify the dominant CCFs in both extratropics (30°–60°N/S) and subtropics (30°S–30°N). A novel map for visualizing dominant CCFs for low‐level cloud fraction reveals that: ∆θskin800hPa${\increment}{\theta }_{\text{skin}}^{800\text{hPa}}$dominates in the subtropical stratocumulus regions while 10‐m winds dominate in shallow cumulus regions but in the extratropics, a different inversion structure diagnostic (EIS) dominates, while SHF dominates in western boundary current areas. Clouds in the lower levels of the atmosphere cover up to 80% of the oceans in some specific areas within the ±30° latitude band (i.e., the subtropics regions) but also cover a large portion of the mid‐latitude oceans (i.e., the extratropics). In the subtropics, cloud cover has been found to depend principally on sea surface temperature and the stability or thermal structure of the lower levels of the troposphere. Using satellite observations and reanalysis data, we test whether these relationships are found everywhere, and importantly, we find that these dependencies are not uniform across the global oceans. Where cloud cover is large, stability is the strongest driver of cloud cover, but the atmospheric vertical structure of this stability most strongly correlated with the clouds differs between the subtropics and extratropics. Where cloud cover is relatively small, near surface wind speed has the strongest relationship with cloud cover in the subtropics, while at higher latitudes and more specifically in the western boundary current regions, air‐sea energy exchanges (i.e., sensible heat flux) dominate. These regionally varying relationships are depicted with a novel map of dominant cloud controlling factors. This map can help with evaluation and development of climate models. A novel map of dominant controlling factors for low‐level oceanic cloud fraction reveals regionally varying patternsSubtropical and extratropical low clouds depend on stability, but the dominant stability metric varies by region, challenging modelsSurface wind speed dominates in cumulus‐dominated regions, sensible heat fluxes dominate in western boundary current regions in winter A novel map of dominant controlling factors for low‐level oceanic cloud fraction reveals regionally varying patterns Subtropical and extratropical low clouds depend on stability, but the dominant stability metric varies by region, challenging models Surface wind speed dominates in cumulus‐dominated regions, sensible heat fluxes dominate in western boundary current regions in winter

This study provides observational evidence for feedbacks that amplify the short‐term hydrological response associated with the warm phase of the El Niño‐Southern Oscillation. Our analyses make use of a comprehensive set of independent satellite observations collected over decades to show that much larger local changes to cloud (~50%/K) and precipitation (~60%/K) occur than would be expected from the guidance of Clausius‐Clapeyron theory (~7%/K). This amplification comes from atmospheric feedbacks involving shifts in the patterns of latent and radiative heating that mutually act on the dynamics enhancing changes to the hydrological cycle. We also confirm the existence of an opposing negative flux feedback at the ocean surface, driven largely by solar radiation changes, that opposes the surface warming. Estimates of the strength of this and other feedback factors associated with warming in the Niño3 region are provided from observations. These observations are also used to examine comparative processes and feedbacks in model experiments from the Coupled Model Intercomparison Project Phase 5 Atmospheric Model Intercomparison Project. It is a widely held paradigm of a warming world the “wet gets wetter and dry drier.” It is also argued that in this context precipitation in wet areas is expected to increase at a rate of approximately 7%/K, which is in accordance with expected increases in water vapor availability from elementary theory (the so‐called Clausius‐Clapeyron response). One of the main wet regions of the planet is the region of deep tropical convection organized into broad convective zones referred to as the Inter‐Tropical Convergence Zone, and this region undergoes variability that is often used to test ideas thought to be relevant to climate change. Our study pieces together several independent measurements collected over multiple decades to reveal a strong, positive feedback on tropical convection associated with the short‐term climate variations of the El Niño/Southern Oscillation. The feedback is a result of coupled dynamical‐radiative processes that combine to produce intensification of the tropical hydrological cycle that is more than twice that expected from the CC response alone. Satellite data demonstrate regional super C‐C intensification of hydrological cycle in response to warm phase of ENSOObservations and global climate models show similar responses and evidence for large‐scale dynamical response to ENSOAtmospheric feedbacks involve shifts in patterns of latent and radiative heating acting on dynamics that enhance hydrological cycle response

Deep convective system maximum areal extent is driven by the stratiform anvil area since convective area fractions are much less than unity when systems reach peak size. It is important to understand the processes that drive system size given the impact large systems have on rainfall and that of anvils on high cloud feedbacks. Using satellite diabatic heating and convective‐stratiform information mapped to convective systems, composite analyses suggest that system maximum sizes occur at the temporal mid‐point of system lifecycles with both maximum size and duration correlating with peak heating above the melting level. However, variations in system growth rates exist, with the overall smooth composites emerging as the average of highly variable system trajectories. Thus, this study focuses on understanding convective system growth rates on short (30‐min) timescales via development of a simple analytical source—sink model that predicts system area changes. Growth occurs when detrained convective mass (inferred from the vertical gradient of diabatic heating and temperature lapse rates) and/or generation of convective area exceeds a sink term whose magnitude is proportional to the current cloud shield size. The model works well for systems over land and ocean, and for systems characterized by varying degrees of convective organization and duration (1.5–35 hr, with correlations often >0.8 across lifetime bins). The model may serve as a useful foundation for improved understanding of processes driving changes in tropics‐wide convective system cloud shields, and further supports conceptual development and evaluation of prognostic climate model stratiform anvil area parameterizations. Thunderstorms are prolific producers of ice higher up in the atmosphere, and those that produce more ice also produce more heating since ice formation releases heat (known as “latent heating”). That heating varies with altitude, and in this study, we develop a simple model that connects the variations in heating with altitude to the rate at which thunderstorms produce lightly to moderately raining areas that many people experience for minutes‐hours after the most intense part of the thunderstorm passes. A simple analytical model for cloud area growth and decay rates is developed, with a source term driven by convective cell diabatic heatingThe model works equally well for convective systems of varying duration and degrees of convective organization over both land and oceanThe model suggests that a system convective area fraction of approximately 0.15 is needed for stratiform cloud area maintenance A simple analytical model for cloud area growth and decay rates is developed, with a source term driven by convective cell diabatic heating The model works equally well for convective systems of varying duration and degrees of convective organization over both land and ocean The model suggests that a system convective area fraction of approximately 0.15 is needed for stratiform cloud area maintenance

Shortwave (SW) cloud feedback (SWFB) is the primary driver of uncertainty in the effective climate sensitivity (ECS) predicted by global climate models (GCMs). ECS for several GCMs participating in the sixth assessment report exceed 5K, above the fifth assessment report “likely” maximum (4.5K) due to extratropical SWFB's that are more positive than those simulated in the previous generation of GCMs. Here we show that across 57 GCMs Southern Ocean SWFBcan be predicted from the sensitivity of column‐integrated liquid water mass (LWP) to moisture convergence and to surface temperature. The response of LWP to moisture convergence and the response of albedo to LWP anti‐correlate across GCMs. This is because GCMs that simulate a larger response of LWP to moisture convergence tend to have higher mean‐state LWPs, which reduces the impact of additional LWP on albedo. Observational constraints suggest a modestly negative Southern Ocean SWFB— inconsistent with extreme ECS. As the climate warms, moisture convergence into the extratropics strengthens, increasing cloudiness, reflected sunlight, and precipitation. Increased cloudiness in response to moisture convergence is affected by how efficiently clouds condense from water vapor relative to how efficiently precipitation depletes them. Simulations where clouds form efficiently cannot reflect much more sunlight in the extratropics because they are already very cloudy and bright. Observations constrain both the sensitivity of reflected sunlight to cloud and of cloud to moisture. Combining these constraints with constraints on other cloud regimes rules out extremely small and large future warming. Enhanced moisture convergence with warming creates a negative extratropical cloud feedbackCloud source and sink efficiency set the extratropical cloud responseConstraint by observations suggests a weakly negative feedback‐ and a moderate effective climate sensitivity Enhanced moisture convergence with warming creates a negative extratropical cloud feedback Cloud source and sink efficiency set the extratropical cloud response Constraint by observations suggests a weakly negative feedback‐ and a moderate effective climate sensitivity

Partitioning deep convective cloud condensates into components that sediment and detrain, known to be a challenge for global climate models, is important for cloud vertical distribution and anvil cloud formation. In this study, we address this issue by improving the convective microphysics scheme in the National Center for Atmospheric Research Community Atmosphere Model version 5.3 (CAM5.3). The improvements include: (1) considering sedimentation for cloud ice crystals that do not fall in the original scheme, (2) applying a new terminal velocity parameterization that depends on the environmental conditions for convective snow, (3) adding a new hydrometeor category, “rimed ice,” to the original four‐class (cloud liquid, cloud ice, rain, and snow) scheme, and (4) allowing convective clouds to detrain snow particles into stratiform clouds. Results from the default and modified CAM5.3 models were evaluated against observations from the U.S. Department of Energy Tropical Warm Pool‐International Cloud Experiment (TWP‐ICE) field campaign. The default model overestimates ice amount, which is largely attributed to the underestimation of convective ice particle sedimentation. By considering cloud ice sedimentation and rimed ice particles and applying a new convective snow terminal velocity parameterization, the vertical distribution of ice amount is much improved in the midtroposphere and upper troposphere when compared to observations. The vertical distribution of ice condensate also agrees well with observational best estimates upon considering snow detrainment. Comparison with observed convective updrafts reveals that current bulk model fails to reproduce the observed updraft magnitude and occurrence frequency, suggesting spectral distributions be required to simulate the subgrid updraft heterogeneity. Graupel is added to a convective microphysics scheme for global climate modelsNew convective ice particle terminal velocity schemes are implemented and convective snow is allowed to detrainVertical distribution of ice mass in the midtroposphere and upper troposphere is improved Graupel is added to a convective microphysics scheme for global climate models New convective ice particle terminal velocity schemes are implemented and convective snow is allowed to detrain Vertical distribution of ice mass in the midtroposphere and upper troposphere is improved