Diurnal Patterns in the Observed Cloud Liquid Water Path Response to Droplet Number Perturbations DOI Open Access
Kevin M. Smalley, Matthew Lebsock, Ryan Eastman

et al.

Authorea (Authorea), Journal Year: 2023, Volume and Issue: unknown

Published: Nov. 22, 2023

A key uncertainty in Aerosol-cloud interactions is the cloud liquid water path (LWP) response to increased aerosols (λ). LWP can either increase due precipitation suppression or decrease entrainment-drying. Previous research suggests that dominates thick clouds, while entrainment-drying prevails thin clouds. The time scales of two competing effects are vastly different, requiring temporally resolved observations. We analyze 3-day Lagrangian trajectories stratocumulus clouds over southeast Pacific using geostationary data. find with a exceeding 200 g m-2 exhibit positive response, lower show negative response. observe significant diurnal cycle λ, indicating more strongly daytime adjustment driven by In contrast, at night, occasionally fully counteract mechanism. time-integrated appears weaker than previously suggested studies do not account for cycle.

Language: Английский

General circulation models simulate negative liquid water path–droplet number correlations, but anthropogenic aerosols still increase simulated liquid water path DOI Creative Commons

Johannes Mülmenstädt,

Edward Gryspeerdt, Sudhakar Dipu

et al.

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(12), P. 7331 - 7345

Published: June 27, 2024

Abstract. General circulation models' (GCMs) estimates of the liquid water path adjustment to anthropogenic aerosol emissions differ in sign from other lines evidence. This reduces confidence effective radiative forcing climate by aerosol–cloud interactions (ERFaci). The discrepancy is thought stem part GCMs' inability represent turbulence–microphysics cloud-top entrainment, a mechanism that leads reduction response an increase aerosols. In real atmosphere, enhanced entrainment be dominant for path, weakening overall ERFaci. We show latest generation GCMs includes models produce negative correlation between present-day cloud droplet number and key piece observational evidence supporting aerosols one earlier-generation could not reproduce. However, even with this correlation, preindustrial values still simulated due parameterized precipitation suppression mechanism. adds correlations are necessarily causal. investigate sources confounding explain noncausal number. These results reminder assessments parameters based on multiple must carefully consider complementary strengths different when disagree.

Language: Английский

Citations

12
Diurnal Patterns in the Observed Cloud Liquid Water Path Response to Droplet Number Perturbations DOI Creative Commons
Kevin M. Smalley, Matthew Lebsock, Ryan Eastman

et al.

Geophysical Research Letters, Journal Year: 2024, Volume and Issue: 51(4)

Published: Feb. 10, 2024

Abstract A key uncertainty in Aerosol‐cloud interactions is the cloud liquid water path (LWP) response to increased aerosols ( λ ). LWP can either increase due precipitation suppression or decrease entrainment‐drying. Previous research suggests that dominates thick clouds, while entrainment‐drying prevails thin clouds. The time scales of two competing effects are vastly different, requiring temporally resolved observations. We analyze 3‐day Lagrangian trajectories stratocumulus clouds over southeast Pacific using 2019–2021 geostationary data. find with a exceeding 200 g m −2 exhibit positive response, lower show negative response. observe significant diurnal cycle , indicating more strongly daytime adjustment driven by In contrast, at night, occasionally fully counteract mechanism. Overall, appears weaker than previously suggested studies do not account for cycle.

Language: Английский

Citations

10
Cloud water adjustments to aerosol perturbations are buffered by solar heating in non-precipitating marine stratocumuli DOI Creative Commons
Jianhao Zhang,

Yao‐Sheng Chen,

Takanobu Yamaguchi

et al.

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(18), P. 10425 - 10440

Published: Sept. 19, 2024

Abstract. Marine low-level clouds are key to the Earth's energy budget due their expansive coverage over global oceans and high reflectance of incoming solar radiation. Their responses anthropogenic aerosol perturbations remain largest source uncertainty in estimating radiative forcing climate. A major challenge is quantification cloud water response perturbations. In particular, presence feedbacks through microphysical, dynamical, thermodynamical pathways at various spatial temporal scales could augment or weaken response. Central this problem evolution adjustment, governed by entangled feedback mechanisms. We apply an innovative conditional Monte Carlo subsampling approach a large ensemble diurnal large-eddy simulation non-precipitating marine stratocumulus study role heating governing relationship between droplet number water. find persistent negative trend night, confirming that microphysically enhanced cloud-top entrainment. After sunrise, appears buffered converges ∼-0.2 late afternoon. This buffering effect attributed strong dependence cloud-layer shortwave absorption on liquid path. These cycle characteristics further demonstrate tight connection brightening potential which has implications for impact timing advertent

Language: Английский

Citations

6
Aerosol-induced closure of marine cloud cells: enhanced effects in the presence of precipitation DOI Creative Commons
Matthew W. Christensen, Peng Wu, Adam Varble

et al.

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(11), P. 6455 - 6476

Published: June 3, 2024

Abstract. The Weather Research Forecasting (WRF) version 4.3 model is configured within a Lagrangian framework to quantify the impact of aerosols on evolving cloud fields. Kilometer-scale simulations utilizing meteorological boundary conditions are based 10 case study days offering diverse meteorology during Aerosol and Cloud Experiments in Eastern North Atlantic (ACE-ENA). Measurements from aircraft, ground-based Atmosphere Radiation Measurement (ARM) site at Graciosa Island Azores, A-Train geostationary satellites utilized for validation, demonstrating good agreement with WRF-simulated aerosol properties. Higher concentration leads suppressed drizzle increased water content all days. These changes lead larger radiative cooling rates top, enhanced vertical velocity variance, horizontal wind speed near base lower-tropospheric inversion. As result, marine cell area expands, narrowing gap between shallow clouds increasing optical thickness, liquid content, top-of-atmosphere outgoing shortwave flux. While similar effects observed lightly non-raining clouds, they tend be smaller by comparison. show relationship expansion adjustments caused path fraction changes. positive scale as 74 % 51 %, respectively, relative Twomey effect. higher-resolution large-eddy may provide improved representation cloud-top mixing processes, these results emphasize importance addressing mesoscale cloud-state transitions quantification forcing that cannot attained traditional climate models.

Language: Английский

Citations

4
Evaluation of liquid cloud albedo susceptibility in E3SM using coupled eastern North Atlantic surface and satellite retrievals DOI Creative Commons
Adam Varble, Po‐Lun Ma, Matthew W. Christensen

et al.

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(20), P. 13523 - 13553

Published: Oct. 27, 2023

Abstract. The impact of aerosol number concentration on cloud albedo is a persistent source spread in global climate predictions due to multi-scale, interactive atmospheric processes that remain difficult quantify. We use 5 years geostationary satellite and surface retrievals at the US Department Energy (DOE) Atmospheric Radiation Measurement (ARM) eastern North Atlantic (ENA) site Azores evaluate representation liquid susceptibility for overcast scenes DOE Exascale Earth System Model version 1 (E3SMv1) provide possible reasons model–observation discrepancies. overall distribution 0.2 % CCN values reasonably simulated, but simulated water path (LWP) lower than observed layer mean droplet (Nd) comparisons are highly variable depending Nd retrieval technique. E3SMv1's greater given LWP effective radius observed. However, response suppressed correlation between solar zenith angle (SZA) created by seasonal cycle not Controlling this effect examining optical depth (COD) shows COD For surface-based retrievals, only true after controlling adiabaticity because adiabaticities much Assuming constant as done top-of-atmosphere (TOA) narrows retrieved ln distribution, which increases sensitivity match TOA sensitivity. caused Twomey TOA-retrieved Nd, once differences removed, also surface-retrieved Nd. E3SMv1 negative Despite reproducing LWP–Nd relationship, clouds become more adiabatic increases, while do not, associated with heavily precipitating partially completely deeper weaker inversions E3SMv1. These property indicate relationship likely same mechanisms observations. fails mute excessively strong effect, highlighting potentially important confounding factor effects render non-causal. scales assumptions, particularly related adiabaticity, contribute substantial spreads comparisons, though enough consistency exists suggest activation, drizzle, entrainment critical areas focus development improving fidelity aerosol–cloud interactions E3SM.

Language: Английский

Citations

10
Mesoscale Cellular Convection Detection and Classification Using Convolutional Neural Networks: Insights From Long‐Term Observations at ARM Eastern North Atlantic Site DOI Creative Commons
Jingjing Tian, J. M. Comstock, Andrew Geiss

et al.

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

Citations

0
Climatology, trend and correlations of aerosol, cloud and meteorology over the climatologically important monsoon and adjacent northern regions of Pakistan DOI
Kashif Anwar,

Syed Shakeel Ahmad Shah,

Abdulhaleem H. Labban

et al.

Atmospheric Research, Journal Year: 2025, Volume and Issue: unknown, P. 108136 - 108136

Published: April 1, 2025

Language: Английский

Citations

0
Rapid saturation of cloud water adjustments to shipping emissions DOI Creative Commons
Peter Manshausen, Duncan Watson‐Parris, Matthew W. Christensen

et al.

Atmospheric chemistry and physics, Journal Year: 2023, Volume and Issue: 23(19), P. 12545 - 12555

Published: Oct. 9, 2023

Abstract. Human aerosol emissions change cloud properties by providing additional condensation nuclei. This increases droplet numbers, which in turn affects other like liquid-water content and ultimately albedo. These adjustments are poorly constrained, making effects the most uncertain part of anthropogenic climate forcing. Here we show that number water react differently to changing emission amounts shipping exhausts. We use information about ship positions modeled together with reanalysis winds satellite retrievals properties. The analysis reveals numbers respond linearly amount over a large range (1–10 kg h−1) before response saturates. Liquid raining clouds, anomalies constant ranges observed. There is evidence this independence due compensating under drier more humid conditions, consistent suppression rain enhanced aerosol. has implications for our understanding processes may improve way clouds represented models, particular parameterizations responses

Language: Английский

Citations

9
Drivers of Cloud Condensation Nuclei in the Eastern North Atlantic as Observed at the ARM Site DOI Creative Commons
Virendra P. Ghate,

Thomas Surleta,

Leehi Magaritz‐Ronen

et al.

Journal of Geophysical Research Atmospheres, Journal Year: 2023, Volume and Issue: 128(22)

Published: Nov. 27, 2023

Abstract Seven years of data collected at the Atmospheric Radiation Measurement's Eastern North Atlantic (ENA) site are analyzed to understand controls Cloud Condensation Nuclei (CCN) concentrations in region. Day‐night differences aerosol as segregated by wind direction demonstrate observations be impacted local emissions when (wdir) is between 90° and 310° (measured clockwise from where air coming from). Data during marine conditions (wdir <90° or wdir >310°) show CCN higher summer months compared winter months. budget analysis revealed advection precipitation scavenging being primarily responsible for modulating on monthly timescales, with rain rates driving term. High (greater than 75th percentile) low (lower 25th events were identified each month characterize sub‐monthly variability concentrations. Low had thicker clouds, stronger rates, lower reanalysis reported free‐tropospheric pseudo number concentration ENA high events. Analysis satellite air‐parcels 48 hr prior their arrival demonstrated parcels encounter cloudiness, cloud top heights The results presented herein provide key constraints model evaluation studies climatological conducted site.

Language: Английский

Citations

7
Improving Low‐Cloud Fraction Prediction Through Machine Learning DOI Creative Commons
Haipeng Zhang, Youtong Zheng, Zhanqing Li

et al.

Geophysical Research Letters, Journal Year: 2024, Volume and Issue: 51(15)

Published: Aug. 3, 2024

Abstract In this study, we evaluated the performance of machine learning (ML) models (XGBoost) in predicting low‐cloud fraction (LCF), compared to two generations community atmospheric model (CAM5 and CAM6) ERA5 reanalysis data, each having a different cloud scheme. ML show substantial enhancement LCF regarding root mean squared errors correlation coefficients. The good is consistent across full spectrums stability large‐scale vertical velocity. Employing an explainable approach, revealed importance including amount available moisture for representing spatiotemporal variations midlatitudes. Also, demonstrated marked improvement capturing during stratocumulus‐to‐cumulus transition (SCT). This study suggests models' great potential address longstanding issues “too few” low clouds rapid” SCT global climate models.

Language: Английский

Citations

2