Stratocumulus Precipitation Properties Over the Southern Ocean Observed From Aircraft During the SOCRATES Campaign

Journal of Geophysical Research Atmospheres, Journal Year: 2024, Volume and Issue: 129(6)

Published: March 11, 2024

Abstract Precipitation plays an important role in cloud and aerosol processes over the Southern Ocean (SO). The main objective of this study is to characterize SO precipitation properties associated with stratocumulus clouds. We use data from Clouds Radiation Aerosol Transport Experimental Study (SOCRATES), leverage observations airborne radar, lidar, situ probes. find that for cold‐topped clouds (cloud‐top‐temperature <0°C), phase reflectivity >0 dBZ predominantly ice, while < −10 liquid. Liquid‐phase are retrieved where radar lidar zenith‐pointing. Power‐law relationships between (Z) rain rate (R) developed, derived Z–R show vertical dependence sensitivity presence droplets diameters 10 40 μm. Using relationships, a reflectivity‐velocity (ZV) retrieval method, radar‐lidar we derive other properties. all three methods shows good agreement in‐situ aircraft estimates, rates typically being quite light (<0.1 mm hr −1 ). examine distribution properties, rate, number concentration, liquid water decrease as one gets closer surface, size width increases. also how base ( R CB ) depends on depth (H) concentration N particles diameter greater than 70 nm, proportional .

Language: Английский

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Above-cloud concentrations of cloud condensation nuclei help to sustain some Arctic low-level clouds

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(6), P. 3529 - 3540

Published: March 20, 2024

Abstract. Previous studies have found that low-level Arctic clouds often persist for long periods even in the face of very low surface cloud condensation nuclei (CCN) concentrations. Here, we investigate whether these conditions could occur due to continuous entrainment aerosol particles from free troposphere (FT). We use an idealized large eddy simulation (LES) modeling framework, where concentrations are boundary layer (BL) but increased up 50× troposphere. find tests with higher tropospheric simulated clouds, which persisted longer and maintained liquid water paths (LWPs). This is direct into layer, results a precipitation suppression increase droplet number stronger cloud-top radiative cooling, causes circulations maintaining absence forcing. Together, two responses result more well-mixed top remains contact reservoir can maintain those particles. The concentrations, however, remained all simulations. free-tropospheric concentration necessary consistent frequently seen observations.

Language: Английский

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Measurement report: Insights into the chemical composition and origin of molecular clusters and potential precursor molecules present in the free troposphere over the southern Indian Ocean: observations from the Maïdo Observatory (2150 m a.s.l., Réunion)

Atmospheric chemistry and physics, Journal Year: 2024, Volume and Issue: 24(6), P. 3785 - 3812

Published: March 27, 2024

Abstract. New particle formation (NPF) in the free troposphere (FT) is thought to be a significant source of particles over oceans. The entrainment initially formed marine FT further suspected major contributor cloud condensation nuclei (CCN) number concentrations boundary layer (BL). Yet, little known about process and, more broadly, composition FT, which remains poorly explored due access difficulties. Here we report measurements performed April 2018 at Maïdo Observatory with nitrate-based chemical ionization atmospheric pressure interface time-of-flight mass spectrometer, have allowed first molecular-level characterization remote composition. A molecules and clusters were identified classified into nine groups according their composition; among species, containing methanesulfonic acid (MSA) C2 amines show signals that are on average significantly higher when site under conditions representative (compared BL). correlation analysis revealed apparent connections between compounds several variables concurrently measured (under conditions) or related air history, suggesting oxalic acid, malonic observed could terrestrial origin, with, addition, possible for amines, while iodic sulfur maleic dominant origin. Identification was based standard deviation wind direction; this parameter, can easily derived from continuous site, shown part study relevant tracer compared predictions Meso-NH model. Similar other high-altitude sites, mainly encountered night Maïdo; therefore, link NPF not established, research needed assess precursors nanoparticle FT.

Language: Английский

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Aitken Mode Aerosols Buffer Decoupled Mid‐Latitude Boundary Layer Clouds Against Precipitation Depletion

Journal of Geophysical Research Atmospheres, Journal Year: 2024, Volume and Issue: 129(12)

Published: June 22, 2024

Abstract Aerosol‐cloud‐precipitation interactions are a leading source of uncertainty in estimating climate sensitivity. Remote marine boundary layers where accumulation mode (∼100–400 nm diameter) aerosol concentrations relatively low very susceptible to changes. These regions also experience heightened Aitken (∼10–100 nm) associated with ocean biology. aerosols may significantly influence cloud properties and evolution by replenishing condensation nuclei droplet number lost through precipitation (i.e., buffering). We use large‐eddy simulation an Aitken‐mode enabled microphysics scheme examine the role buffering mid‐latitude decoupled layer regime observed on 15 July 2017 during Aerosol Cloud Experiments Eastern North Atlantic flight campaign: cumulus rising into stratocumulus under elevated (∼100–200 mg −1 ). In situ measurements used constrain evaluate this case study. Our accurately captures aerosol‐cloud‐precipitation reveals time‐evolving processes driving development evolution. activation provides reservoir for turbulence convection carry drizzling above. Further occurs aloft layer. Together, these events buffer against removal, reducing break‐up increases heterogeneity. sensitivity initial conditions. With halved number, restore concentrations, maintain similar original values, prevent break‐up. Without aerosols, precipitation‐driven rapidly. regime, sustains brighter, more homogeneous clouds longer.

Language: Английский

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Reply on RC2

Published: Jan. 6, 2025

Abstract. Aerosol-cloud interactions (aci) are the largest source of uncertainty in inferring magnitude future warming consistent with observational record. The effective radiative forcing due to aci (ERFaci) is dominated by liquid clouds and composed two terms: change cloud albedo redistributing over a larger number droplets (N_d) macrophysical properties changes microphysics. These terms respectively referred as (RFaci) aerosol-cloud adjustments. While RFaci uncertain, its sign confidently negative results cooling historical In contrast, adjustment water path (LWP) enhanced N_d associated uncertain sign. Increased LWP response increased precipitation suppression while decreased evaporation from top. Observational constraints these processes poor part because causal ambiguity relationship between LWP. To better understand this relationship, (P), N_d, surface observations Eastern North Atlantic (ENA) atmospheric observatory combined output perturbed parameter ensemble (PPE) hosted Community Atmosphere Model version 6 (CAM6). This allows interpretation observed covariability. Observations ENA constrain range possible adjustments relative prior PPE 15 %, resulting global value that positive (a cooling) ranging 2.1 6.9 g/m². It found covariability N_d and coalescence scavenging not strongly related

Language: Английский

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