More biomass burning aerosol is being advected westward over the southern tropical Atlantic since 2003

EarthArXiv (California Digital Library), Journal Year: 2024, Volume and Issue: unknown

Published: July 26, 2024

Each year, agricultural fires in southern continental Africa emit approximately one third of the world’s biomass burning aerosol. This is advected westward by prevailing circulation winds over a subtropical stratocumulus cloud deck. The radiative effects from aerosol and aerosol-cloud interactions impact regional circulations hydrology. Here we examine how changes coupled African earth system past 20 years southeast Atlantic. We combine satellite-derived burned area datasets with ECMWF-reanalysis carbon monoxide, black carbon, meteorology season (May-October) Africa. begins May woody savannas northwest shifts to open savanna grassland southeast, small (less than 1 km2) contributing significantly total area. More are occurring middle overall shorter, corroborated reanalysis monoxide fields. Significantly increased free tropospheric winds, shifted southward, transport smoke further southwest advection shift south Atlantic high an increase low fraction on edge While emissions sources have not changed significantly, pathway, attributed increasing surface temperatures tropical expansion, combined altered distribution, explain radiation balance has more top-of-atmosphere cooling recent decades.

Language: Английский

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Stratus and Stratocumulus Cloud Microphysics and Drizzle Relationships With CCN Modality

Journal of Geophysical Research Atmospheres, Journal Year: 2024, Volume and Issue: 129(21)

Published: Nov. 7, 2024

Abstract High resolution extended‐range cloud condensation nuclei (CCN) spectral comparisons with microphysics and drizzle of the Physics Stratocumulus Tops (POST) field experiment confirmed results in Marine Stratus/Stratocumulus Experiment (MASE). Both these stratus projects demonstrated that bimodal CCN spectra typically caused by processing were associated clouds exhibited higher concentrations smaller droplets narrower distributions less than unimodal spectra. Resulting brighter increased cloudiness could enhance both indirect aerosol effects (IAE). These findings are opposite analogous measurements two cumulus projects, which showed fewer larger more broadly distributed CCN. reduced brightness reduce IAE. flights air masses concentrations, N , extremes characteristics. However, POST lower droplet characteristics similar to clouds, yet still CCN, but not as much . Since all MASE polluted masses, while clean we deduce from four dynamic stratus/cumulus differences (vertical wind) responsible for among projects. This is because a hybrid between MASE/POST high

Language: Английский

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Diurnal evolution of non-precipitating marine stratocumuli in a large-eddy simulation ensemble

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(22), P. 12661 - 12685

Published: Nov. 14, 2024

Abstract. We explore the cloud system evolution of non-precipitating marine stratocumuli with a focus on impacts diurnal cycle and free-tropospheric (FT) humidity based an ensemble 244 large-eddy simulations generated by perturbing initial thermodynamic profiles aerosol conditions. Cases are categorized their degree decoupling liquid water path (LWPc, model columns optical depths greater than one). A budget analysis method is proposed to analyze in both coupled decoupled boundary layers. More clouds start relatively low LWPc fraction (fc) but experience least decrease fc during daytime. undergo daytime reduction fc, especially those higher at sunrise because they suffer from faster weakening net radiative cooling. During nighttime, positive correlation between FT emerges, consistent reducing cooling jump, which reduce entrainment increase LWPc. The more likely nighttime for larger inversion base height (zi), conditions under dominates as turbulence develops. In morning, rate depends sunrise, zi, decoupling, distinct contributions subsidence radiation.

Language: Английский

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Improving Prediction of Marine Low Clouds Using Cloud Droplet Number Concentration in a Convolutional Neural Network

Journal of Geophysical Research Machine Learning and Computation, Journal Year: 2024, Volume and Issue: 1(4)

Published: Nov. 30, 2024

Abstract Marine low clouds play a crucial role in cooling the climate, but accurately predicting them remains challenging due to their highly non‐linear response various factors. Previous studies usually overlook effects of cloud droplet number concentration (N d ) and non‐local information target grids. To address these challenges, we introduce convolutional neural network model (CNN Met‐Nd that uses both local includes N as cloud‐controlling factor enhance predictive ability daily cover, albedo, radiative (CRE) for global marine clouds. CNN demonstrates superior performance, explaining over 70% variance three variables scenes 1° × 1°, notable improvement past efforts. also replicates geographical patterns trends from 2003 2022. In contrast, similar without Met struggles predict long‐term properties effectively. Permutation importance analysis further highlights critical Met‐N 's success. Further comparisons with an artificial (ANN model, which same inputs considering spatial dependence, show performance R 2 values CRE being 0.16, 0.12, 0.18 higher, respectively. This incorporating information, at least on scale, into predictions climate parameterizations.

Language: Английский

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