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The Southern Ocean (SO) provides a unique natural laboratory for studying cloud formation and cloud-aerosol interactions with minimal anthropogenic influence. The Southern Ocean Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES), was an aircraft-based campaign conducted from January 15 to February 28, 2018, off the coast of Hobart, Tasmania. During SOCRATES, the NSF/NCAR GV research aircraft, equipped with in-situ probes and remote sensors, observed aerosol, cloud, and precipitation properties, and provided detailed vertical structure of clouds over the SO, particularly for the low-level clouds (below 3 km). The HIAPER Cloud Radar (HCR) and in-situ cloud and drizzle probes (CDP and 2DS) measurements were used to provide comprehensive statistical and phase-relevant macrophysical properties for the low-level clouds sampled by the 15 research flights during SOCRATES. A new method based on HCR reflectivity and spectrum width gradient was developed to estimate cloud boundaries (cloud-base and -top heights) and classify cloud types based on their top and base heights. Low-level clouds were found to be the most prevalent, with an almost 90 % occurrence frequency. A new phase determination method was also developed to identify the single-layered low-level clouds as liquid, ice, and mixed phases, with occurrence frequencies of 45.4 %, 32.5 %, and 22.2 %, respectively. Low-level clouds over the SO have significantly higher SLW concentrations, with liquid being most prevalent at higher temperatures, ice phase dominating at lower temperatures, and mixed-phase being least common due to its thermodynamic instability. Regarding their vertical distributions, the liquid phase occurs most frequently in the lower mid-cloud range (from 500 m to 1 km), the mixed phase dominates at cloud bases lower than 1 km but is well distributed along the vertical cloud layer, while the ice phase is prevalent from the middle to upper cloud levels (1–3 km). The higher occurrence of the mixed phase at the cloud base could be attributed to large drizzle-sized drops and/or ice particles. [ABSTRACT FROM AUTHOR]

Biomass burning smoke aerosols are efficient at attenuating incoming solar radiation. The Layered Atlantic Smoke Interactions with Clouds campaign was conducted from June 2016 to October 2017. The U. S. Department of Energy mobile Atmospheric Radiation Measurement site located on Ascension Island (AMF‐ASI) identified several instances of smoke plume intrusions. Increases in surface and column measurements of aerosol loading were directly related to increases in fine mode fraction, number concentrations of aerosols (Na), and cloud condensation nuclei (NCCN). During periods of weak lower tropospheric stability, smoke particles were more likely to be advected downward either by boundary layer turbulence or cloud top entrainment under non‐overcast sky conditions. Backward trajectory analysis illustrated that smoke aerosols reaching the AMF‐ASI site were fine mode, less aged, strongly absorbing, and had shorter boundary layer trajectories while longer boundary layer trajectories denoted mixtures of weakly absorbing smoke and coarse mode marine aerosols. The most polluted smoke cases of August 2016 and 2017 revealed a notable contrast in radiative forcing per unit aerosol optical depth or radiative forcing efficiency (ΔFeff) at the top of the atmosphere (TOA) and near‐surface (BOA). The weakly (strongly) absorbing 2016 cases exhibited weaker (stronger) ΔFeff at the TOA and BOA suggesting a warming (cooling) effect within the boundary layer. The 2017 cases featured the strongest ΔFeff suggesting more of a cooling effect at the TOA and BOA due to mixing of fresh smoke with marine aerosols during transport. Plain Language Summary: Fires are often observed in Central Africa throughout the year due to agricultural and natural processes. As a result of changes in pressure patterns along with wind direction and strength, the smoke aerosols can transport to regions thousands of kilometers away from the fires. The aerosols can aid in cloud development while at the same time, have variable impacts on the amount of solar radiation reaching the surface and returning to space which can cause either warming or cooling along their transport pathway. In the Southern Hemisphere tropics, there are few observations to document aerosol radiative forcing impacts on global climate. This study uses short‐term and long‐term measurements of aerosol physical properties in conjunction with meteorological analysis to diagnose the impact of smoke aerosols on incoming solar radiation and cloud development during transport. Key Points: African biomass burning smoke plumes feature highly variable top of the atmosphere and BOA radiative forcing efficiencies when mixed with marine aerosolsSmoke aerosols with stronger radiative forcing efficiencies present a cooling effect which can stabilize the marine boundary layerLonger back trajectories suggest aging of smoke aerosols and mixing with marine aerosols which facilitate cloud development [ABSTRACT FROM AUTHOR]

The aerosol-cloud-precipitating interaction within the cloud-topped Marine Boundary Layer (MBL), are being examined using aircraft in-situ measurements from Aerosol and Cloud Experiments in the Eastern North Atlantic (ACE-ENA) and Southern Ocean Clouds Radiation Aerosol Transport Experimental Study (SOCRATES) field campaigns. SOCRATES clouds have a larger number of smaller cloud droplets compared to ACE-ENA summertime and wintertime clouds. The ACE-ENA clouds, especially in wintertime, exhibit pronounced drizzle formation and growth, attributed to the strong in-cloud turbulence that enhances the collision-coalescence process. Furthermore, the Aerosol-Cloud Interaction (ACI) indices from the two aircraft field campaigns suggest distinct sensitivities. The aerosols during ACE-ENA winter are more likely to be activated into cloud droplets due to more larger aerosols and strong vertical turbulence. The enriched aerosol loading during SOCRATES generally leads to smaller cloud droplets competing for available water vapor and exhibiting a stronger ACI. The ACI calculated near the cloud base was noticeably larger than the layer-mean and near-cloud-top, owing to the closer connection between the cloud layer and sub-cloud aerosols. Notably, the sensitivities of cloud base precipitating rates to cloud-droplet number concentrations are more pronounced during the ACE-ENA than during the SOCRATES campaigns. The in-cloud drizzle evolutions significantly alter sub-cloud cloud condensation nuclei (CCN) budgets through the coalescence-scavenging effect, and in turn, impact the ACI assessments. The results of this study can enhance the understanding and aid in future model simulation and assessment of the aerosol-cloud interaction. [ABSTRACT FROM AUTHOR]

Resistive switching random‐access memory (RRAM) has attracted tremendous interest for applications in both embedded memory and neuromorphic computing. In this paper, two distinct types of resistive switching in Ti/TiOx/Pd‐based RRAM devices depending on the bottom electrode morphology is reported. One is filamentary resistive switching where the bottom Pd electrode has spikes caused by liftoff. The enhancement of local electric field caused by the spikes induces the formation of conductive filaments and hence leads the device to be nonvolatile. The other one is dynamic resistive switching, where the bottom electrode is flat without spikes and the device resistance changes dynamically with time. For such devices, the electric field and the oxygen ion concentration gradient in the TiOx layer have competing effects on the oxygen ion movement, which makes the Schottky barrier height at metal/oxide interface vary dynamically with time. Based on detailed physical analysis, a compact behavioral model of the dynamic RRAM device is established. The model fits well with experimentally measured device characteristics, and can be easily incorporated in deep learning algorithms. The work paves the road for further optimization of dynamic RRAM device and also its application in dynamic signal processing. [ABSTRACT FROM AUTHOR]