The Role of Mesoscale Cloud Morphology in the Shortwave Cloud Feedback

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(2)

Published: Jan. 18, 2023

Abstract A supervised neural network algorithm is used to categorize near‐global satellite retrievals into three mesoscale cellular convective (MCC) cloud morphology patterns. At constant amount, patterns differ in brightness associated with the amount of optically thin features. Environmentally driven transitions from closed MCC other patterns, typically accompanied by more features, are as a framework quantify contribution optical depth component shortwave feedback. marine heat wave an out‐of‐sample test occurrence predictions. Morphology shifts between 65°S and 65°N under projected environmental changes (i.e., abrupt quadrupling CO 2 ) assuming cover contributes 0.04 0.07 W m −2 K −1 (aggregate 0.06) global mean

Language: Английский

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Cloud adjustments from large-scale smoke–circulation interactions strongly modulate the southeastern Atlantic stratocumulus-to-cumulus transition

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(18), P. 12113 - 12151

Published: Sept. 19, 2022

Abstract. Smoke from southern Africa blankets the southeastern Atlantic Ocean June to October, producing strong and competing aerosol radiative effects. effects on transition between overcast stratocumulus scattered cumulus clouds are investigated along a Lagrangian (air-mass-following) trajectory in regional climate large eddy simulation models. Results compared with observations three recent field campaigns that took place August 2017: ObseRvations of Aerosols above CLouds their intEractionS (ORACLES), Aerosol Radiative Impacts Forcing: Year 2017 (CLARIFY), Layered Interactions Clouds (LASIC). The case study is set up around joint ORACLES–CLARIFY flight near Ascension Island 18 2017. sampled upstream an ORACLES 15 likely entrained into marine boundary layer later during flight. first simulated WRF-CAM5 model distinct setups: (1) FireOn, which smoke emissions any resulting smoke–cloud–radiation interactions included; (2) FireOff, no (3) RadOff, microphysical included but does not interact directly radiation. Over course trajectory, differences free tropospheric thermodynamic properties FireOn FireOff nearly identical those showing aerosol–radiation primarily responsible for These non-intuitive: addition expected heating within core plume, there also “banding” effect cooler temperature (∼1–2 K) greatly enhanced moisture (>2 g kg−1) at plume top. This banding caused by vertical displacement former continental troposphere anomalous diabatic due absorption sunlight manifests as few hundred meters per day reduction large-scale subsidence over ocean. A (LES) then forced fields taken outputs runs. Cases run selectively perturbing one variable (e.g., number concentration, temperature, moisture, velocity) time better understand contributions different indirect (microphysical), “large-scale” semi-direct (above-cloud changes), “local” (below-cloud absorption) Despite more than 5-fold increase cloud droplet concentration when including concentrations, minimal fraction evolution LES comparing base perturbed dynamic forcings. factor 2 decrease background concentrations shifts classical entrainment-driven “deepening–warming” trade precipitation-driven “drizzle-depletion” open cells, however. changes WRF-simulated adjustments strongly influence terms both rate deepening (especially inversion jump subsidence) final effect). Such would have been possible simulate using small-domain alone.

Language: Английский

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Effects of intermittent aerosol forcing on the stratocumulus-to-cumulus transition

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

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Impacts of Mesoscale Cloud Organization on Aerosol‐Induced Cloud Water Adjustment and Cloud Brightness

Geophysical Research Letters, Journal Year: 2023, Volume and Issue: 50(13)

Published: July 6, 2023

Abstract The role of mesoscale cellular convection (MCC) in regulating aerosol‐induced cloud brightness remains unaddressed. Using 7 years satellite‐based observations water adjustment to perturbations for closed MCCs across different sizes (8, 16, 32, and 64 km) over the North Atlantic Ocean, we show that MCC cell‐size plays a nontrivial via adjustment. In cells are primarily non‐precipitating, small‐scale can be 10 times more negative than large‐scale MCCs, consistent with stronger evaporation top entrainment. Consequently, response is significantly MCCs. We also find notable intra‐cell co‐variability between liquid path (LWP) drop concentration ( N d ) within varies cell size. Erroneously considering such as LWP lead significant positive bias, especially small scale

Language: Английский

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Wind, Rain, and the Closed to Open Cell Transition in Subtropical Marine Stratocumulus

Journal of Geophysical Research Atmospheres, Journal Year: 2022, Volume and Issue: 127(20)

Published: Sept. 27, 2022

Abstract Lagrangian transitions in mesoscale cellular convective (MCC) clouds beginning as closed cell MCC and transitioning to open cells or disorganized but are explored on timescales from 12 72 hr. Potential drivers of shown act multiple timescales. Closed‐to‐open cloud preceded by strong surface winds large moisture fluxes at lead times up hr; high water content, reduced drop concentrations, intense rain rates 12–36 The relationship between the formation is consistent with a cold pool convergence mechanism. A analysis shows that anomalously associated higher well subsequent increases through modifications flux content boundary layer. closed‐open transition contrasts closed‐to‐disorganized which long warm sea temperature diurnal‐scale variables related top entrainment drying such deepening layer, weakening subsidence inversion strength, drier free troposphere. conceptual model proposed where excess layer wind breaks stratocumulus closed‐to‐open transition, while dry‐air transition.

Language: Английский

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Mesoscale Cellular Convection Detection and Classification Using Convolutional Neural Networks: Insights From Long‐Term Observations at ARM Eastern North Atlantic Site

Journal of Geophysical Research Machine Learning and Computation, Journal Year: 2025, Volume and Issue: 2(1)

Published: March 1, 2025

Abstract Marine boundary layer clouds are crucial in Earth's climate system. They frequently manifest as closed or open cell mesoscale cellular convection (MCC). MCC challenging to represent accurately current models, highlighting the need for detailed observational data sets and in‐depth analyses. This study utilizes over 8 years of observations from U.S. Department Energy (DOE) Atmospheric Radiation Measurement (ARM) User Facility Eastern North Atlantic (ENA) site at Graciosa Island, Azores, investigate these clouds. We first apply a convolutional neural network with U‐Net architecture classify cells, marking application such an approach automatically detecting patterns ground‐based radar measurements. method addresses some gaps satellite related low temporal resolution, nighttime challenges, limited vertical structure capture. The analysis cases shows clear differences between MCCs: Closed characterized by lower cloud tops bases, shallower geometrical depth, weaker horizontal wind speeds, stronger atmospheric stability, more homogeneous liquid water path than MCCs. Finally, we demonstrate two potential applications our radar‐based classifications: (a) facilitating investigation aerosol‐cloud interactions (b) exploring meteorological factors along MCC's evolution integrating imagery back‐trajectory analysis. identified offer valuable resource scientific community processes further improve model accuracy.

Language: Английский

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Co-variability drives the inverted-V sensitivity between liquid water path and droplet concentrations

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

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Machine-Learning Based Analysis of Liquid Water Path Adjustments to Aerosol Perturbations in Marine Boundary Layer Clouds Using Satellite Observations

Atmosphere, Journal Year: 2022, Volume and Issue: 13(4), P. 586 - 586

Published: April 5, 2022

Changes in marine boundary layer cloud (MBLC) radiative properties response to aerosol perturbations are largely responsible for uncertainties future climate predictions. In particular, the relationship between droplet number concentration (Nd, a proxy aerosol) and liquid water path (LWP) remains challenging quantify from observations. this study, satellite observations multiple polar-orbiting platforms 2006–2011 used combination with atmospheric reanalysis data regional machine learning model predict changes LWP MBLCs Southeast Atlantic. The impact of predictor variables on output is analysed using Shapley values as technique explainable learning. Within model, precipitation fraction, top height, Nd identified important state predictors LWP, dynamical proxies sea surface temperature (SST) being most environmental predictors. A positive nonlinear found, weaker sensitivity at high concentrations. This found be dependent other model: Nd–LWP higher precipitating clouds decreases increasing SSTs.

Language: Английский

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Exploring relations between cloud morphology, cloud phase, and cloud radiative properties in Southern Ocean's stratocumulus clouds

Atmospheric chemistry and physics, Journal Year: 2022, Volume and Issue: 22(15), P. 10247 - 10265

Published: Aug. 10, 2022

Abstract. Marine stratocumuli are the most dominant cloud type by area coverage in Southern Ocean (SO). They can be divided into different self-organized cellular morphological regimes known as open and closed mesoscale-cellular convective (MCC) clouds. Open cells two frequent types of organizational SO. Using liDAR-raDAR (DARDAR) version 2 retrievals, we quantify 59 % all MCC clouds this region mixed-phase (MPCs) during a 4-year time period from 2007 to 2010. The net radiative effect SO is governed changes albedo. Both morphology phase have previously been shown impact albedo individually, but their interactions combined on remain unclear. Here, investigate relationships between phase, patterns, differences regarding properties fraction, which defined number MPCs sum MPC supercooled liquid (SLC) pixels, at given cloud-top temperature (CTT) varies considerably austral summer winter. We further find that seasonal CTT across latitudes largely independent thus seemingly constrained other external factors. Overall, our results show stronger dependence height (CTH) than for below 2.5 km altitude. Preconditioning through ice-phase processes has observed accelerate individual closed-to-open cell transitions extratropical stratocumuli. hypothesis preconditioning substantiated large-eddy simulations MPCs. In study, do not primarily climatological statistics Meanwhile, in-cloud analysis reveals SLCs particular, few optically thick (cloud optical thickness >10) characterized ice-free SLCs. These found alter 21 39 W m−2 depending season phase.

Language: Английский

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Characterizing Mesoscale Cellular Convection in Marine Cold Air Outbreaks With a Machine Learning Approach

Journal of Geophysical Research Atmospheres, Journal Year: 2024, Volume and Issue: 129(14)

Published: July 24, 2024

Abstract During marine cold‐air outbreaks (MCAOs), when cold polar air moves over warmer ocean, a well‐recognized cloud pattern develops, with open or closed mesoscale cellular convection (MCC) at larger fetch water. The Cold‐Air Outbreaks in the Marine Boundary Layer Experiment provided comprehensive set of ground‐based situ and remote sensing observations MCAOs coastal location northern Norway. MCAO periods that unambiguously exhibit MCC are determined. Individual cells observed profiling Ka‐band radar identified using watershed segmentation method. Using self‐organizing maps (SOMs), these then objectively classified based on variability their vertical structure. SOM nodes contain some information about cell transect relative to center MCC. This adds classification noise, requiring numerous transects isolate dynamical information. SOM‐based shows comparatively intense occurs only undergoes an apparent lifecycle. Developing associated stronger updrafts, large spectrum width, amounts liquid water, lower surface precipitation rates, tops than mature weakening cells. is development precipitation‐induced pools. also reveals less convection, similar More stratiform structures weak motions common during separated into precipitating non‐precipitating cores. Convection occasionally environment.

Language: Английский

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