Florian Tornow
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View article: High Accumulation Mode Aerosol Concentration and Moderate Aerosol Hygroscopicity Limit Impacts of Recent Particle Formation on Northwest Atlantic Post‐Frontal Clouds
High Accumulation Mode Aerosol Concentration and Moderate Aerosol Hygroscopicity Limit Impacts of Recent Particle Formation on Northwest Atlantic Post‐Frontal Clouds Open
Postfrontal cloud regime transitions often result from strong aerosol‐cloud‐precipitation interaction. Using ACTIVATE measurements from 40 flights, we show a diurnal pattern of evolving aerosol particle size distributions (PSD) in the mari…
Seeking TOA SW Flux Closure over Synthetic 3D Cloud Fields: Exploring the Accuracy of two Angular Distribution Models Open
To accurately estimate outgoing top-of-atmosphere (TOA) shortwave (SW) fluxes from measurements of broadband radiances, angular distribution models (ADMs) are necessary. ADMs rely on radiance-predicting models that are trained on hemispher…
View article: The NASA ACTIVATE Mission
The NASA ACTIVATE Mission Open
The NASA Aerosol Cloud Meteorology Interactions over the Western Atlantic Experiment (ACTIVATE) conducted 162 joint flights with two aircraft over the northwest Atlantic to study aerosol–cloud interactions (ACIs), which represent the large…
View article: Measurement report: A survey of meteorological and cloud properties during ACTIVATE’s postfrontal flights and their suitability for Lagrangian case studies
Measurement report: A survey of meteorological and cloud properties during ACTIVATE’s postfrontal flights and their suitability for Lagrangian case studies Open
Postfrontal clouds, often appearing as marine cold-air outbreaks (MCAOs) along eastern seaboards, undergo overcast-to-broken cloud regime transitions. Earth system models exhibit diverse radiative biases connected to postfrontal clouds, re…
View article: Effect of Ice Number Concentration on the Evolution of Boundary Layer Clouds During Arctic Marine Cold‐Air Outbreaks
Effect of Ice Number Concentration on the Evolution of Boundary Layer Clouds During Arctic Marine Cold‐Air Outbreaks Open
Marine cold‐air outbreaks (MCAOs) are crucial for Arctic Ocean heat loss, featuring convective cloud rolls that transition into convection cells downstream. Understanding factors controlling this transformation is the key for improving MCA…
View article: Can general circulation models (GCMs) represent cloud liquid water path adjustments to aerosol–cloud interactions?
Can general circulation models (GCMs) represent cloud liquid water path adjustments to aerosol–cloud interactions? Open
General circulation models (GCMs), unlike other lines of evidence, indicate that anthropogenic aerosols cause a global-mean increase in cloud liquid water path (ℒ) and thus a negative adjustment to radiative forcing of the climate by aeros…
View article: Measurement Report: A survey of meteorological and cloud properties during ACTIVATE's postfrontal flights and their suitability for Lagrangian case studies
Measurement Report: A survey of meteorological and cloud properties during ACTIVATE's postfrontal flights and their suitability for Lagrangian case studies Open
Postfrontal clouds, often appearing as marine cold-air outbreaks (MCAOs) along Eastern seaboards, undergo overcast-to-broken cloud regime transitions. Earth system models exhibit diverse radiative biases connected to postfrontal clouds, re…
View article: Aerosol size distribution properties associated with cold-air outbreaks in the Norwegian Arctic
Aerosol size distribution properties associated with cold-air outbreaks in the Norwegian Arctic Open
The aerosol particles serving as cloud condensation and ice nuclei contribute to key cloud processes associated with cold-air outbreak (CAO) events but are poorly constrained in climate models due to sparse observations. Here we retrieve a…
View article: General circulation models simulate negative liquid water path–droplet number correlations, but anthropogenic aerosols still increase simulated liquid water path
General circulation models simulate negative liquid water path–droplet number correlations, but anthropogenic aerosols still increase simulated liquid water path Open
General circulation models' (GCMs) estimates of the liquid water path adjustment to anthropogenic aerosol emissions differ in sign from other lines of evidence. This reduces confidence in estimates of the effective radiative forcing of the…
View article: Comment on egusphere-2024-778
Comment on egusphere-2024-778 Open
Abstract. General circulation models (GCMs), unlike other lines of evidence, indicate that anthropogenic aerosols cause a global-mean increase in cloud liquid water path (𝓛), and thus a negative adjustment to radiative forcing of the clima…
View article: Comment on egusphere-2024-778
Comment on egusphere-2024-778 Open
Abstract. General circulation models (GCMs), unlike other lines of evidence, indicate that anthropogenic aerosols cause a global-mean increase in cloud liquid water path (𝓛), and thus a negative adjustment to radiative forcing of the clima…
View article: Comment on egusphere-2024-778
Comment on egusphere-2024-778 Open
Abstract. General circulation models (GCMs), unlike other lines of evidence, indicate that anthropogenic aerosols cause a global-mean increase in cloud liquid water path (𝓛), and thus a negative adjustment to radiative forcing of the clima…
Aerosol Size Distribution Properties Associated with Cold-Air Outbreaks in the Norwegian Arctic Open
The aerosol particles that provide cloud condensation and ice nuclei contribute to key cloud processes associated with cold-air outbreak (CAO) events but are poorly constrained in climate models due to sparse observations. Here we retrieve…
View article: Can GCMs represent cloud adjustments to aerosol–cloud interactions?
Can GCMs represent cloud adjustments to aerosol–cloud interactions? Open
General circulation models (GCMs), unlike other lines of evidence, indicate that anthropogenic aerosols cause a global-mean increase in cloud liquid water path (𝓛), and thus a negative adjustment to radiative forcing of the climate by aero…
View article: General circulation models simulate negative liquid water path–droplet number correlations, but anthropogenic aerosols still increase simulated liquid water path
General circulation models simulate negative liquid water path–droplet number correlations, but anthropogenic aerosols still increase simulated liquid water path Open
General circulation models' (GCMs) estimates of the liquid water path adjustment to anthropogenic aerosol emissions differ in sign from other lines of evidence. This reduces confidence in estimates of the effective radiative forcing of the…
Microphysical evolution in mixed-phase mid-latitude marine cold-air outbreaks Open
Five cold-air outbreaks are investigated with aircraft offshore of continental northeast American. Flight paths aligned with the cloud-layer flow span cloud-top temperatures of -5 to -12 0C, in situ liquid water paths of up to 600 g m-2, w…
View article: Wintertime Synoptic Patterns of Midlatitude Boundary Layer Clouds Over the Western North Atlantic: Climatology and Insights From In Situ ACTIVATE Observations
Wintertime Synoptic Patterns of Midlatitude Boundary Layer Clouds Over the Western North Atlantic: Climatology and Insights From In Situ ACTIVATE Observations Open
The winter synoptic evolution of the western North Atlantic and its influence on the atmospheric boundary layer is described by means of a regime classification based on Self‐Organizing Maps applied to 12 years of data (2009–2020). The reg…
The impact of dry intrusions on midlatitude cold-air outbreak cloud transitions Open
Cold-air outbreaks (CAOs) form marine boundary layer (MBL) clouds that undergo rapid overcast-to-broken cloud regime transitions, initiated by substantial rain. CAOs are usually accompanied by dry intrusions (DIs) that subside as free-trop…
Large-Eddy Simulations of Marine Boundary Layer Clouds Associated with Cold-Air Outbreaks during the ACTIVATE Campaign. Part II: Aerosol–Meteorology–Cloud Interaction Open
Aerosol effects on micro/macrophysical properties of marine stratocumulus clouds over the western North Atlantic Ocean (WNAO) are investigated using in situ measurements and large-eddy simulations (LES) for two cold-air outbreak (CAO) case…
Dilution of Boundary Layer Cloud Condensation Nucleus Concentrations by Free Tropospheric Entrainment During Marine Cold Air Outbreaks Open
Recent aircraft measurements over the northwest Atlantic enable an investigation of how entrainment from the free troposphere (FT) impacts cloud condensation nucleus (CCN) concentrations in the marine boundary layer (MBL) during cold‐air o…
Dilution of boundary layer cloud condensation nucleus concentrations by free tropospheric entrainment during marine cold air outbreaks Open
Mid-latitude marine cold air outbreaks (CAOs) occur in the post-frontal sector of extratropical cyclones. Once advected over the ocean, the marine boundary layer (MBL) quickly deepens and hosts near-overcast clouds that transition into an …
Large-eddy simulations of marine boundary-layer clouds associated with cold air outbreak during the ACTIVATE campaign. Part II: aerosol-meteorology-cloud interaction Open
Aerosol effects on micro-/macro-physical properties of marine stratocumulus clouds over the Western North Atlantic Ocean (WNAO) are investigated using in-situ measurements and large-eddy simulations (LES) for two cold air outbreak (CAO) ca…
Dilution of boundary layer cloud condensation nucleus concentrations by free tropospheric entrainment during marine cold air outbreaks Open
Recent aircraft measurements over the northwest Atlantic enable an investigation of how entrainment from the free troposphere (FT) impacts cloud condensation nuclei (CCN) in the marine boundary layer (MBL) during cold-air outbreaks (CAOs),…
Large-Eddy Simulations of Marine Boundary Layer Clouds Associated with Cold-Air Outbreaks during the ACTIVATE Campaign. Part I: Case Setup and Sensitivities to Large-Scale Forcings Open
Large-eddy simulation (LES) is able to capture key boundary layer (BL) turbulence and cloud processes. Yet, large-scale forcing and surface turbulent fluxes of sensible and latent heat are often poorly prescribed for LESs. We derive these …
View article: On Assessing ERA5 and MERRA2 Representations of Cold‐Air Outbreaks Across the Gulf Stream
On Assessing ERA5 and MERRA2 Representations of Cold‐Air Outbreaks Across the Gulf Stream Open
The warm Gulf Stream sea surface temperatures strongly impact the evolution of winter clouds behind atmospheric cold fronts. Such cloud evolution remains challenging to model. The Gulf Stream is too wide within the ERA5 and MERRA2 reanalys…
Preconditioning of overcast-to-broken cloud transitions by riming in marine cold air outbreaks Open
Marine cold air outbreaks (CAOs) commonly form overcast cloud decks that transition into broken cloud fields downwind, dramatically altering the local radiation budget. In this study, we investigate the impact of frozen hydrometeors on the…
View article: On assessing ERA5 and MERRA2 representations of cold-air outbreaks across the Gulf Stream
On assessing ERA5 and MERRA2 representations of cold-air outbreaks across the Gulf Stream Open
The warm Gulf Stream sea surface temperatures (SSTs) strongly impact the evolution of winter clouds behind atmospheric cold fronts. Such cloud evolution remains challenging to model. The Gulf Stream is too wide within the ERA5 and MERRA2 r…