Comment on egusphere-2023-1720 DOI Creative Commons
Prasanth Prabhakaran, Fabian Hoffmann, Graham Feingold

et al.

Published: Sept. 8, 2023

Abstract. We explore the role of intermittent aerosol forcing (e.g., ship tracks, or injections associated with marine cloud brightening) on stratocumulus-to-cumulus transition (SCT). simulate a three-day Lagrangian trajectory in north-east Pacific using large-eddy simulation model coupled to bin-emulating, two-moment, bulk microphysics scheme that captures evolution and droplet concentrations. By varying background concentration, we consider two baseline systems - pristine polluted. perturb cases range injection strategies by rate, number injectors, timing injection. Our results show dispersal is more efficient under conditions due transverse circulation created gradients precipitation rates across plume track. Furthermore, see substantial enhancement radiative effect (CRE) evident both systems. In polluted system, albedo (smaller but numerous droplets causing brighter clouds at constant liquid water) dominant contributor initial days. The contributions from water path (LWP) fraction adjustments are important third fourth day, respectively. CRE all three days, followed effect. these systems, SCT delayed aerosol, extent delay proportional particles injected into boundary layer.

Language: Английский

Spatial Aggregation of Satellite Observations Leads to an Overestimation of the Radiative Forcing due to Aerosol‐Cloud Interactions DOI Creative Commons
Tom Goren, Odran Sourdeval, Jan Kretzschmar

et al.

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(18)

Published: Sept. 14, 2023

Abstract The estimation of cloud radiative forcing due to aerosol‐cloud interactions, RF aci (also known as the first indirect effect), relies on approximating albedo susceptibility changes in droplet concentration, β . depends and both which can be observed by satellites. Satellite observations are often spatially aggregated coarser resolutions, typically 1 × 1° scenes. However, such spatial scales, tends heterogeneous, whereas approximation assumes homogeneity. Here, we demonstrate that common practice aggregating satellite data neglecting heterogeneity results an average overestimation 10% previous estimates Additionally, establish a relationship between magnitude bias Stratocumulus morphologies, providing physical context for associated bias. Lastly, propose correction method applied gridded data.

Language: Английский

Citations

15
Overview and statistical analysis of boundary layer clouds and precipitation over the western North Atlantic Ocean DOI Creative Commons
Simon Kirschler, Christiane Voigt, B. E. Anderson

et al.

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(18), P. 10731 - 10750

Published: Sept. 27, 2023

Abstract. Due to their fast evolution and large natural variability in macro- microphysical properties, the accurate representation of boundary layer clouds current climate models remains a challenge. One regions with intermodel spread Coupled Model Intercomparison Project Phase 6 ensemble is western North Atlantic Ocean. Here, statistically representative situ measurements can help develop constrain parameterization global models. To this end, we performed comprehensive clouds, aerosol, trace gases, radiation Ocean during NASA Aerosol Cloud meTeorology Interactions oVer ATlantic Experiment (ACTIVATE) mission. In total, 174 research flights 574 flight hours for cloud precipitation were HU-25 Falcon three winter (February–March 2020, January–April 2021, November 2021–March 2022) summer seasons (August–September May–June 2022). Here present statistical evaluation 16 140 individual events probed by droplet probe two-dimensional stereo 155 repetitive strategy allowing robust data analyses. We show that vertical profiles distributions liquid water content effective diameter (ED) increase altitude marine layer. higher updraft speeds, number concentrations (Nliquid) measured compared despite lower condensation nucleus abundance. Flight cover derived from analysis reduced shows variability. This seasonal contrast coverage consistent dominance synoptic pattern favors conditions formation stratiform at edge cyclones (post-cyclonic). contrast, dominant anticyclone concomitant occurrence shallow cumulus coverage. The Nliquid ED phase space sheds light on liquid, mixed-phase, ice properties helps categorize data. Ice precipitation, often masked statistics high abundance observed throughout cloud. ACTIVATE provide wealth information useful assessing airborne satellite remote-sensing products, weather model evaluations, dedicated process studies address aerosol–cloud interactions.

Language: Английский

Citations

15
Frontiers in Satellite‐Based Estimates of Cloud‐Mediated Aerosol Forcing DOI
Daniel Rosenfeld, Alexander Kokhanovsky, Tom Goren

et al.

Reviews of Geophysics, Journal Year: 2023, Volume and Issue: 61(4)

Published: Oct. 18, 2023

Abstract Atmospheric aerosols affect the Earth's climate in many ways, including acting as seeds on which cloud droplets form. Since a large fraction of these particles is anthropogenic, clouds' microphysical and radiative characteristics are influenced by human activity global scale leading to important climatic effects. The respective change energy budget at top atmosphere defined effective forcing due aerosol‐cloud interaction (ERF aci ). It estimated that ERF offsets presently nearly 1/4 greenhouse‐induced warming, but uncertainty within factor two. A common method calculate multiplication susceptibility effect changes anthropogenic aerosol concentration. This has be done integrating it over all regimes. Here we review various methods estimation. Global measurements require satellites' coverage. challenge quantifying amounts cloudy atmospheres met with rapid development novel methodologies reviewed here. can retrieved from space based their optical properties, polarization. concentrations serve drop condensation nuclei also impact satellite‐retrieved number concentrations. These observations critical for reducing calculated models (GCMs), further required allow GCMs properly simulate benefit observables.

Language: Английский

Citations

15
Investigating the development of clouds within marine cold-air outbreaks DOI Creative Commons
Rebecca J. Murray-Watson, Edward Gryspeerdt, Tom Goren

et al.

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(16), P. 9365 - 9383

Published: Aug. 24, 2023

Abstract. Marine cold-air outbreaks are important parts of the high-latitude climate system and characterised by strong surface fluxes generated air–sea temperature gradient. These promote cloud formation, which can be identified in satellite imagery distinct transformation stratiform “streets” into a broken field cumuliform clouds downwind outbreak. This evolution morphology changes radiative properties therefore is importance to energy budget. While drivers stratocumulus-to-cumulus transitions, such as aerosols or sea gradient, have been extensively studied for subtropical clouds, factors influencing transitions at higher latitudes relatively poorly understood. work uses reanalysis data create set composite trajectories moving off Arctic ice edge co-locates these with generate unique view liquid-dominated development within outbreaks. The results this analysis show that embedded distinctive relative following other region. initial strength outbreak shows lasting effect on properties, differences between weak events visible over 30 h after air has left edge. However, while (measured magnitude marine index) affects it does not affect timing transition top-of-atmosphere albedo. In contrast, aerosol conditions do strongly but correlated break-up, leading an enhanced cooling through high-aerosol due delayed break-up. Both environment frequency expected change future Arctic, provide insight how will clouds. also highlight need information about present-day sources correctly model development.

Language: Английский

Citations

14
Global observations of aerosol indirect effects from marine liquid clouds DOI Creative Commons
Casey J. Wall, Trude Storelvmo, Anna Possner

et al.

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(20), P. 13125 - 13141

Published: Oct. 18, 2023

Abstract. Interactions between aerosols and liquid clouds are one of the largest sources uncertainty in historical radiative forcing climate. One widely shared goal to reduce this is decompose anomalies arising from aerosol–cloud interactions into components associated with changes cloud-droplet number concentration (Twomey effect), liquid-water-path adjustments, cloud-fraction adjustments. However, there has not been a quantitative foundation for simultaneously estimating these global satellite observations. Here we present method assessing shortwave flux Twomey effect cloud adjustments over ocean 55∘ S N. We find that larger aerosol concentrations widespread brightening effect, positive adjustment decreasing water path subtropical stratocumulus regions, negative increasing fraction subtropics midlatitudes. The total have contributed −0.77 ± 0.25 −1.02 0.43 W m−2, respectively, effective since 1850 domain (95 % confidence). Our findings suggest make contribution than commonly believed.

Language: Английский

Citations

14
Effects of intermittent aerosol forcing on the stratocumulus-to-cumulus transition DOI Creative Commons
Prasanth Prabhakaran, Fabian Hoffmann, Graham Feingold

et al.

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(3), P. 1919 - 1937

Published: Feb. 13, 2024

Abstract. We explore the role of intermittent aerosol forcing (e.g., injections associated with marine cloud brightening) in stratocumulus-to-cumulus transition (SCT). simulate a 3 d Lagrangian trajectory northeast Pacific using large-eddy simulation model coupled to bin-emulating, two-moment, bulk microphysics scheme that captures evolution and droplet concentrations. By varying background concentration, we consider two baseline systems – pristine polluted. perturb cases range injection strategies by rate, number injectors, timing injection. Our results show dispersal is more efficient under conditions due transverse circulation created gradients precipitation rates across plume track. Furthermore, see substantial enhancement radiative effect (CRE) evident both systems. In polluted system, albedo (smaller but numerous droplets causing brighter clouds at constant liquid water) dominant contributor initial 2 d. The contributions from water path (LWP) fraction adjustments are important on third fourth day, respectively. CRE all d, followed effect. these systems, SCT delayed aerosol, extent delay proportional particles injected into boundary layer.

Language: Английский

Citations

5
Thin Clouds Control the Cloud Radiative Effect Along the Sc‐Cu Transition DOI Creative Commons
Goutam Choudhury, Tom Goren

Journal of Geophysical Research Atmospheres, Journal Year: 2024, Volume and Issue: 129(10)

Published: May 14, 2024

Abstract In situ and spaceborne studies reveal the prevalence of thin clouds in major Stratocumulus‐to‐Cumulus Transition (SCT) regions. Using instantaneous satellite reanalysis data, this study investigates properties Southeast Pacific Ocean their impact on cloud radiative effect (CRE). Our findings demonstrate that are intrinsic to SCT. The overcast stratocumulus‐dominated regime exhibits a minimal presence clouds, which become notably prominent after breakup into cumulus‐dominated regime. dependence occurrence is also observed terms marine cold‐air outbreak parameter sea surface temperature. Thin at given cover significantly modulate shortwave (SW) longwave (LW) components CRE. SW CRE decreases by 46 %–65 % with increasing cover. They account for larger variance albedo than combined influence liquid water path effective radius. Furthermore, LW about 12 %–52 An increase fraction leads negative offset positive This compensation ranges from approximately 8 as much 19 50 These elucidate crucial role thus morphology, modulating underscore necessity accurate representation climate models.

Language: Английский

Citations

4
Co-variability drives the inverted-V sensitivity between liquid water path and droplet concentrations DOI Creative Commons
Tom Goren, Goutam Choudhury, Jan Kretzschmar

et al.

Atmospheric chemistry and physics, Journal Year: 2025, Volume and Issue: 25(6), P. 3413 - 3423

Published: March 21, 2025

Abstract. Climatological data of the liquid water path (LWP) and droplet concentration (Nd) often reveal an inverted-V relationship, where LWP increases then decreases as Nd increases. Our findings show that while this response to increase in aligns with proposed causal mechanisms, such entrainment evaporation feedback precipitation suppression, pattern is primarily driven by co-variability between Nd. This arises from (1) large-scale meteorology, which controls both Nd, causing them vary opposite directions simultaneously, (2) microphysical processes, typically accompanied a decrease Consequently, we suggest sensitivity should not be used evidence for positive radiative forcing through adjustments aerosols it largely explained co-variability. We further demonstrate relationship essentially reflects climatological evolution Stratocumulus clouds (Sc). Therefore, background anthropogenic changes should, principle, reflected redistribution occurrences across inverted V maintaining its shape.

Language: Английский

Citations

0
Shallow cumulus cloud fields are optically thicker when they are more clustered DOI Creative Commons
Pouriya Alinaghi, Martin Janssens, Goutam Choudhury

et al.

Quarterly Journal of the Royal Meteorological Society, Journal Year: 2024, Volume and Issue: unknown

Published: June 17, 2024

Abstract Shallow trade cumuli over subtropical oceans are a persistent source of uncertainty in climate projections. Mesoscale organization cumulus clouds has been shown to influence their cloud radiative effect (CRE) through cover. We investigate whether can explain CRE variability independently cloud‐cover variability. By analyzing satellite observations and high‐resolution simulations, we show that more clustered fields feature geometrically thicker with larger domain‐averaged liquid water paths, smaller droplets, consequently optical depths. The relationships between these variables shaped by the mixture deep cores shallower interstitial or anvils characterize organization. Eliminating effects, reflect up 20 W/m instantaneous shortwave radiation back space.

Language: Английский

Citations

3
Global Observations of Aerosol Indirect Effects from Marine Liquid Clouds DOI Creative Commons
Casey J. Wall, Trude Storelvmo, Anna Possner

et al.

Published: June 29, 2023

Abstract. Interactions between aerosols and liquid clouds are one of the largest sources uncertainty in historical radiative forcing climate. One widely shared goal to reduce this is decompose anomalies arising from aerosol-cloud interactions into components associated with changes cloud-droplet number concentration (Twomey effect), water path adjustments, cloud-fraction adjustments. However, there has not been a quantitative foundation for simultaneously estimating these global satellite observations. Here we present method assessing shortwave flux Twomey effect cloud adjustments over ocean 55° S N. We find that larger aerosol concentrations widespread brightening effect, positive adjustment decreasing subtropical stratocumulus regions, negative increasing fraction subtropics midlatitudes. The total contribute -0.77±0.25 W m-2 -1.02±0.43 m-2, respectively, effective since 1850 domain (95 % confidence). Our findings suggest make contribution than commonly believed.

Language: Английский

Citations

2