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1. eCloud: A Vision for the Evolution of the Edge-Cloud Continuum

   https://doi.org/10.1109/MC.2021.3059737  

   Arulraj, Joy; Chatterjee, Abhijit; Daglis, Alexandros; Dhekne, Ashutosh; Ramachandran, Umakishore (May 2021, Computer)

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2. Evolution and Kinematics of Protostellar Envelopes in the Perseus Molecular Cloud

   https://doi.org/10.3847/1538-4357/ac448e  

   Heimsoth, Daniel J.; Stephens, Ian W.; Arce, Héctor G.; Bourke, Tyler L.; Myers, Philip C.; Dunham, Michael M. (March 2022, The Astrophysical Journal)

   Abstract We present a comprehensive analysis of the evolution of envelopes surrounding protostellar systems in the Perseus molecular cloud using data from the MASSES survey. We focus our attention to the C 18 O(2–1) spectral line, and we characterize the shape, size, and orientation of 54 envelopes and measure their fluxes, velocity gradients, and line widths. To look for evolutionary trends, we compare these parameters to the bolometric temperature T bol , a tracer of protostellar age. We find evidence that the angular difference between the elongation angle of the C 18 O envelope and the outflow axis direction generally becomes increasingly perpendicular with increasing T bol , suggesting the envelope evolution is directly affected by the outflow evolution. We show that this angular difference changes at T bol = 53 ± 20 K, which includes the conventional delineation between Class 0 and I protostars of 70 K. We compare the C 18 O envelopes with larger gaseous structures in other molecular clouds and show that the velocity gradient increases with decreasing radius ( ∣  ∣ ∼ R − 0.72 ± 0.06 ). From the velocity gradients we show that the specific angular momentum follows a power-law fit J / M ∝ R 1.83±0.05 for scales from 1 pc down to ∼500 au, and we cannot rule out a possible flattening out at radii smaller than ∼1000 au. 

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3. Magnetohydrodynamic Turbulent Evolution of a Magnetic Cloud in the Outer Heliosphere

   https://doi.org/10.3847/2041-8213/abcb03  

   Telloni, Daniele; Zhao, Lingling; Zank, Gary P.; Liang, Haoming; Nakanotani, Masaru; Adhikari, Laxman; Carbone, Francesco; D’Amicis, Raffaella; Perrone, Denise; Bruno, Roberto; et al (December 2020, The Astrophysical Journal)

   null (Ed.)
4. Diurnal Differences in Tropical Maritime Anvil Cloud Evolution

   https://doi.org/10.1175/JCLI-D-21-0211.1  

   Gasparini, Blaž; Sokol, Adam B.; Wall, Casey J.; Hartmann, Dennis L.; Blossey, Peter N. (March 2022, Journal of Climate)

   Abstract Satellite observations of tropical maritime convection indicate an afternoon maximum in anvil cloud fraction that cannot be explained by the diurnal cycle of deep convection peaking at night. We use idealized cloud-resolving model simulations of single anvil cloud evolution pathways, initialized at different times of the day, to show that tropical anvil clouds formed during the day are more widespread and longer lasting than those formed at night. This diurnal difference is caused by shortwave radiative heating, which lofts and spreads anvil clouds via a mesoscale circulation that is largely absent at night, when a different, longwave-driven circulation dominates. The nighttime circulation entrains dry environmental air that erodes cloud top and shortens anvil lifetime. Increased ice nucleation in more turbulent nighttime conditions supported by the longwave cloud-top cooling and cloud-base heating dipole cannot compensate for the effect of diurnal shortwave radiative heating. Radiative–convective equilibrium simulations with a realistic diurnal cycle of insolation confirm the crucial role of shortwave heating in lofting and sustaining anvil clouds. The shortwave-driven mesoscale ascent leads to daytime anvils with larger ice crystal size, number concentration, and water content at cloud top than their nighttime counterparts. Significance Statement Deep convective activity and rainfall peak at night over the tropical oceans. However, anvil clouds that originate from the tops of deep convective clouds reach their largest extent in the afternoon hours. We study the underlying physical mechanisms that lead to this discrepancy by simulating the evolution of anvil clouds with a high-resolution model. We find that the absorption of sunlight by ice crystals lofts and spreads the daytime anvil clouds over a larger area, increasing their lifetime, changing their properties, and thus influencing their impact on climate. Our findings show that it is important not only to simulate the correct onset of deep convection but also to correctly represent anvil cloud evolution for skillful simulations of the tropical energy balance. 

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5. Investigating the evolution of water-soluble organic carbon in evaporating cloud water

   https://doi.org/10.1039/d0ea00005a  

   Pratap, Vikram; Christiansen, Amy E.; Carlton, Annmarie G.; Lance, Sara; Casson, Paul; Dukett, Jed; Hassan, Hesham; Schwab, James J.; Hennigan, Christopher J. (January 2021, Environmental Science: Atmospheres)

   null (Ed.)

   Cloud cycling plays a key role in the evolution of atmospheric particles and gases, producing secondary aerosol mass and transforming the optical properties and impacts of aerosols globally. In this study, bulk cloud water samples collected at Whiteface Mountain (Wilmington, NY) in the summer of 2017 were aerosolized, dried to 50% RH, and analyzed for the evaporative loss of water soluble organic carbon (WSOC) and for brown carbon (BrC) formation. Systematic WSOC evaporation occurred in all cloud water samples, while no evidence for drying induced BrC formation was observed. On average, 11% (±3%) of WSOC evaporated when the aerosolized cloud droplets were dried to 50% RH, though this represents a lower bound on the WSOC reversibly partitioned to clouds due to experimental constraints. To our knowledge, this represents the first direct measurements of organic evaporation from actual cloud water undergoing drying. Formate and acetate contributed 19%, on average, to the evaporated WSOC, while no oxalate evaporation occurred. GECKO-A model simulations were carried out to predict the production of WSOC compounds that reversibly partition to cloud water from photooxidation of an array of VOCs. The model results suggest that precursor VOC identity and oxidation regime (VOC:NO x ) have a dramatic effect on the reversible partitioning of WSOC to cloud water and the abundance of aqSOA precursors, though the higher abundance of reversibly partitioned WSOC predicted by the model may be due to aqueous production of low-volatility material in the actual cloud samples. This study underscores the importance of the large fraction of unidentified compounds that contribute to WSOC in cloud water and their aqueous processing. 

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