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    Geophysical Research Letters: Volume 47, Issue 23

    16 December 2020
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Open Access

Issue Information

  • First Published: 23 November 2020

Research Letters

Oceans

Open Access

Detection of Coccolithophore Blooms With BioGeoChemical-Argo Floats

L. Terrats,  H. Claustre,  M. Cornec,  A. Mangin,  G. Neukermans, 
  • First Published: 09 November 2020
Key Points

  • We matched profiling float trajectories with ocean-color satellite observations of coccolithophore blooms
  • Two simple bio-optical indices permitted successful identification of coccolithophore blooms from floats in the Southern Ocean
  • A method for identifying coccolithophore blooms at the global scale is proposed using regional thresholds of bio-optical float measurements

Space Sciences

Open Access

A Persistent Depletion of Plasma Ions Within Jupiter's Auroral Polar Caps

C. J. Pollock,  R. W. Ebert,  F. Allegrini,  F. Bagenal,  D. J. McComas,  J. R. Szalay,  P. Valek, 
  • First Published: 16 November 2020
Key Points

  • Ion at energies per charge between 10 V and 46 kV is persistently depleted within the Jovian auroral polar caps
  • Probability of observing such fluxes increases with increasing distance from the centers of the statistical north and south main ovals
  • Absence of ion plasma is consistent with formation of large downward E fields above the Jovian polar caps as previously reported

Cryosphere

Open Access

Detection of Melt Ponds on Arctic Summer Sea Ice From ICESat-2

R. Tilling,  N. T. Kurtz,  M. Bagnardi,  A. A. Petty,  R. Kwok, 
  • First Published: 16 November 2020
Key Points

  • We present a first assessment of NASA's ICESat-2 over a range of individual Arctic sea ice melt ponds
  • ICESat-2 backscatter signatures over melt ponds vary significantly, depending on surface roughness
  • Our ability to estimate melt pond width, fraction, and depth and improve ICESat-2 sea ice freeboard products depends on surface backscatter

Solid Earth

Open Access

Analytical Prediction of Seismicity Rate Due to Tides and Other Oscillating Stresses

Elías R. Heimisson,  Jean-Philippe Avouac, 
  • First Published: 20 November 2020
Key Points

  • We derive a simple analytical model for seismicity rate based on rate-and-state friction
  • The model can be applied to perpetually oscillating stresses on Earth and other solid-surface bodies
  • We reevaluate recent work on possible tidally triggered seismicity on Mars

Space Sciences

Open Access

Alpha Transmitter Signal Reflection and Triggered Emissions

Wenyao Gu,  Lunjin Chen,  Zhiyang Xia,  Xin An,  Richard B. Horne, 
  • First Published: 16 November 2020
Key Points

  • Both ducted reflected signals and triggered emissions from transmitters are observed in the magnetosphere
  • Ducted propagation is confirmed using time delay analysis and ray tracing model
  • The interaction region for nonlinear growth is determined to be off the equator

Open Access

Lunar Dust Fountain Observed Near Twilight Craters

Lianghai Xie,  Xiaoping Zhang,  Lei Li,  Bin Zhou,  Yiteng Zhang,  Qi Yan,  Yongyong Feng,  Dawei Guo,  Shuoran Yu, 
  • First Published: 29 October 2020
Key Points

  • We find five dust enhancements events near twilight craters, with the in situ dust measurements of the LADEE mission
  • The dust enhancement events can be caused by an electrostatic dust lofting from the leeward wall of a twilight crater
  • The lunar horizon glow observed in the Apollo missions can be also related to a twilight crater

Cryosphere

Open Access

Out of the Ice Age: Megatides of the Arctic Ocean and the Bølling-Ållerød, Younger Dryas Transition

Jesse Velay-Vitow,  W. Richard Peltier, 
  • First Published: 16 November 2020
Key Points

  • The Arctic Ocean was megatidal from the LGM to the beginning of the Bølling-Ållerød
  • Extremely high tides are predicted to have occurred in the Amundsen Gulf, potentially destabilizing the ice stream which existed there
  • This instability cleared the channel through which the freshwater outflow that caused the YD later occurred

Space Sciences

Open Access

Pitch-Angle Scattering of Inner Magnetospheric Electrons Caused by ECH Waves Obtained With the Arase Satellite

M. Fukizawa,  T. Sakanoi,  Y. Miyoshi,  Y. Kazama,  Y. Katoh,  Y. Kasahara,  S. Matsuda,  A. Matsuoka,  S. Kurita,  M. Shoji,  M. Teramoto,  S. Imajo,  I. Sinohara,  S.-Y. Wang,  S. W.-Y. Tam,  T.-F. Chang,  B.-J. Wang,  C.-W. Jun, 
  • First Published: 29 October 2020
Key Points

  • We found an event that electron cyclotron harmonic wave intensity correlated with electron flux in a loss cone with ~5 keV energy
  • The pitch-angle diffusion coefficient of 5 keV is larger than those of other energies when the electron temperature is 8 eV and the wave normal angle is 88.5°
  • The electron flux correlated with the ECH wave intensity can cause 557.7 nm auroral emission with ~200 R intensity

Climate

Open Access

African Lightning and its Relation to Rainfall and Climate Change in a Convection-Permitting Model

D. L. Finney,  J. H. Marsham,  J. M. Wilkinson,  P. R. Field,  A. M. Blyth,  L. S. Jackson,  E. J. Kendon,  S. O. Tucker,  R. A. Stratton, 
  • First Published: 17 October 2020
Key Points

  • Lightning and its relationship to rainfall vary considerably across Africa, with indication of dry lightning in arid regions
  • Opposite changes in lightning days and intensity lead to little change in total flashes under climate change, unlike many past studies
  • Graupel increases are smaller than column water increases, and therefore, lightning intensity mostly increases less than rain intensity

Open Access

Dependence Types in a Binarized Precipitation Network

C. De Michele,  V. Meroni,  L. Rahimi,  C. Deidda,  A. Ghezzi, 
  • First Published: 23 November 2020
Key Points

  • We investigate the wet-wet, dry-dry, and wet-dry (dry-wet) pairwise dependence within a precipitation network
  • We develop a methodology and a procedure to test the dependence between each pair of nodes and applied it to a network of rain gauges covering Europe and North Africa
  • We identify geographic areas where the wet-wet and/or dry-dry connections are frequent and where the wet-dry and/or dry-wet connections are observed

Atmospheric Science

Open Access

On the Dependency of Atlantic Hurricane and European Windstorm Hazards

M. Angus,  G. C. Leckebusch, 
  • First Published: 16 November 2020
Key Points

  • Above average Atlantic hurricane seasons are followed by above average European windstorm seasons less often than if they were independent
  • The El Niño–Southern Oscillation is a consistent factor for both seasons, several months ahead of the European windstorm season
  • This has important predictability implications for both the actuarial and seasonal forecasting communities

Solid Earth

Open Access

Heat Transfer From Convecting Magma Reservoirs to Hydrothermal Fluid Flow Systems Constrained by Coupled Numerical Modeling

Christine Andersen,  Philipp Weis, 
  • First Published: 20 November 2020
Key Points

  • Novel coupled numerical simulations of magma convection and hydrothermal fluid flow show how permeability controls heat transfer rates
  • Magma convection leads to faster cooling of an intrusion by up to 15% due to heat transfer toward the magma-hydrothermal interface
  • Partially counteracting this acceleration, magma flow can prevent permeability creation and hydrothermal cooling at the reservoir edges

Open Access

Present-Day Stress Field Influences Bedrock Fracture Openness Deep Into the Subsurface

Seulgi Moon,  J. Taylor Perron,  Stephen J. Martel,  Bradley W. Goodfellow,  Diego Mas Ivars,  Adrian Hall,  Jakob Heyman,  Raymond Munier,  Jens-Ove Näslund,  Assen Simeonov,  Arjen P. Stroeven, 
  • First Published: 16 November 2020
Key Points

  • We calculate three-dimensional present-day subsurface stress fields in a low-relief landscape at Forsmark, Sweden
  • Present-day stress fields correlate strongly with the fraction of observed open fractures in cores down to ~500 m depth
  • Subsurface bedrock stress influenced by surface conditions and pore pressure contributes to the formation of the deep critical zone

Atmospheric Science

Open Access

Why Are There More Summer Afternoon Low Clouds Over the Tibetan Plateau Compared to Eastern China?

Yinjun Wang,  Xubin Zeng,  Xiangde Xu,  Joshua Welty,  Donald H. Lenschow,  Mingyu Zhou,  Yang Zhao, 
  • First Published: 02 November 2020
Key Points

  • There are more summer afternoon low clouds over the Tibetan Plateau (TP) than over eastern China as a result of two mechanisms
  • Compared to eastern China, with the same relative humidity, lower temperature over the TP results in a lower lifting condensation level
  • With the same surface sensible heat flux, lower air density over the TP results in a larger buoyancy flux and a deeper boundary layer

Open Access

SABER Observations of Gravity Wave Responses to the Madden-Julian Oscillation From the Stratosphere to the Lower Thermosphere in Tropics and Extratropics

Jintai Li,  Xian Lu, 
  • First Published: 16 November 2020
Key Points

  • The 17-year SABER-observed GWs show strong response to MJO phase (6–16% anomaly to seasonal mean) from 30–100 km in tropics and extratropics
  • Response has salient latitudinal dependences that reverse signs from Phases 3/4 positive to Phases 7/8 negative anomaly in northern winter
  • Responses in tropics and northern extratropic are consistent with the MJO modulation of convective GW source and polar vortex, respectively

Climate

Open Access

Observational and Model Evidence for an Important Role for Volcanic Forcing Driving Atlantic Multidecadal Variability Over the Last 600 Years

Amanda J. Waite,  Jeremy M. Klavans,  Amy C. Clement,  Lisa N. Murphy,  Volker Liebetrau,  Anton Eisenhauer,  Ralf J. Weger,  Peter K. Swart, 
  • First Published: 16 November 2020
Key Points

  • A high-resolution 600-year proxy temperature record from the subtropical Atlantic shows multidecadal temperature variability
  • In both models and observations, surface temperatures at this site are reflective of basin-wide multidecadal variability
  • Comparison with Last Millennium climate model simulations shows the fingerprint of volcanically induced cooling

Solid Earth

Open Access

Seismic Attenuation Monitoring of a Critically Stressed San Andreas Fault

Luca Malagnini,  Tom Parsons, 
  • First Published: 20 November 2020
Key Points

  • Variations in seismic attenuation can be interpreted in terms of changes in crustal permeability
  • Prefailure conditions along the San Andreas fault correspond to clear positive anomalies in seismic attenuation
  • Seismic attenuation may be used as a crustal stress meter

Planets

Open Access

Mars Climate Sounder Observation of Mars' 2018 Global Dust Storm

D. M. Kass,  J. T. Schofield,  A. Kleinböhl,  D. J. McCleese,  N. G. Heavens,  J. H. Shirley,  L. J. Steele, 
  • First Published: 12 September 2019
Key Points

  • Mars Climate Sounder observed the impacts of a Martian global dust storm in 2018 on the atmospheric temperature, dust, and water ice profiles
  • The 2018 global dust storm was remarkably similar to the 2001 storm in seasonal timing, peak temperature, opacity and in global evolution
  • Regional and global dust storms can be clearly distinguished on the basis of the maximum zonal mean peak 50 Pa daytime temperatures

Atmospheric Science

Open Access

Scaling Laws for the Length Scale of Energy-Containing Eddies in a Sheared and Thermally Stratified Atmospheric Surface Layer

A. Ayet,  G. G. Katul, 
  • First Published: 16 November 2020
Key Points

  • Numerical Weather Prediction models use a master turbulence length scale linked to the characteristic wavelength of energy-containing eddies
  • A relation predicting variations of this wavelength with atmospheric stability is derived
  • Predictions agree with experiments and offer a new perspective on return-to-isotropy approaches

Open Access

Quasi-10-Day Wave and Semidiurnal Tide Nonlinear Interactions During the Southern Hemispheric SSW 2019 Observed in the Northern Hemispheric Mesosphere

Maosheng He,  Jorge L. Chau,  Jeffrey M. Forbes,  Denise Thorsen,  Guozhu Li,  Tarique Adnan Siddiqui,  Yosuke Yamazaki,  Wayne K. Hocking, 
  • First Published: 20 November 2020
Key Points

  • Mesospheric winds from multiple longitudes in the NH are combined to diagnose zonal wave numbers of waves during the Antarctic SSW 2019
  • Diagnosed are Q6DW, Q10DW, M2, SW1, SW2, SW3, and LSB and USB of Q10DW-SW2 nonlinear interactions
  • LSB and USB are generated asynchronously, during which their parent waves evolve following the Manley-Rowe energy relations

Open Access

Two-Point Mixing, Buoyancy Sorting, and Updraft Dilution in the RACORO Campaign

Xin Wei,  Pak Wah Chan,  Zhiming Kuang, 
  • First Published: 16 November 2020
Key Points

  • Aircraft measurements of shallow cumuli show two-point mixing but no ongoing buoyancy sorting
  • Around half of the instances of two-point mixing show no noticeable updraft dilution
  • Including surface heterogeneity yields better agreement of the cloud layer horizontal moisture variation between LES and observations

Open Access

Diurnal Variations in Tropical Cyclone Intensification

Qiaoyan Wu,  Jiacheng Hong,  Zhenxin Ruan, 
  • First Published: 10 November 2020
Key Points

  • Maximum intensification rate is found at 03–08 LST for global TCs
  • No diurnal signals are detected for TC decay
  • The highest TC intensification rate at 03–08 LST is associated with the largest coverage of the very deep convective clouds at 03–06 LST

Climate

Open Access

Skewness of Temperature Data Implies an Abrupt Change in the Climate System Between 1985 and 1991

A. Skelton,  N. Kirchner,  I. Kockum, 
  • First Published: 20 November 2020
Key Points

  • Skewness is used to search for abrupt changes in temperature time series from Europe
  • An abrupt change is identified at 17 sites between 1985 and 1991
  • Arctic sea ice loss potentially coupled with sulfate aerosol emission reductions is a possible cause

Atmospheric Science

Open Access

Variation in Concentration and Sources of Black Carbon in a Megacity of China During the COVID-19 Pandemic

Liang Xu,  Jian Zhang,  Xin Sun,  Shengchen Xu,  Meng Shan,  Qi Yuan,  Lei Liu,  Zhenhong Du,  Dantong Liu,  Da Xu,  Congbo Song,  Bowen Liu,  Gongda Lu,  Zongbo Shi,  Weijun Li, 
  • First Published: 16 November 2020
Key Points

  • BC concentrations during the COVID-lockdown were reduced by 44% in a megacity of China
  • BC from fossil fuels has the largest reduction in urban area during the COVID-lockdown
  • Vehicles and industrial activities are the major contributors of BC in the megacity, followed by and biomass burning

Hydrology and Land Surface Studies

Open Access

An Innovative Application of Generative Adversarial Networks for Physically Accurate Rock Images With an Unprecedented Field of View

Yufu Niu,  Ying Da Wang,  Peyman Mostaghimi,  Pawel Swietojanski,  Ryan T. Armstrong, 
  • First Published: 09 November 2020
Key Points

  • The connectivity and petrophysical properties of super-resolution data are comparable to that provided by high-resolution ground truth data
  • The presented approach offers a unique opportunity to provide physically accurate digital rock images with a large field of view
  • The methodology narrows the gap between sample sizes used for digital rock studies and those used for petrophysical experiments in laboratory

Atmospheric Science

Open Access

The Reduction in Near-Global Cloud Cover After Correcting for Biases Caused by Finite Resolution Measurements

Soumi Dutta,  Larry Di Girolamo,  Sagnik Dey,  Yizhe Zhan,  Catherine M. Moroney,  Guangyu Zhao, 
  • First Published: 20 November 2020
Key Points

  • The 50°N to 50°S cloud fraction reduced from 0.65 to 0.47 based on new MISR cloud product that corrects for measurement resolution effects
  • Largest reductions (up to ~0.4) in cloud fraction occur over trade cumulus regions and smallest (<0.1) occur over stratocumulus regions
  • New MISR cloud fractions are within ±0.05–0.08 of regional ASTER benchmarks compared to overestimates of 0.4–0.5 from original MISR and MODIS

Open Access

Determinant Role of Aerosols From Industrial Sources in Hurricane Harvey's Catastrophe

Bowen Pan,  Yuan Wang,  Timothy Logan,  Jen-Shan Hsieh,  Jonathan H. Jiang,  Yixin Li,  Renyi Zhang, 
  • First Published: 20 November 2020
Key Points

  • Aerosol increases accumulative precipitation by a factor of 2T and invigorates lightning activities in Houston during Hurricane Harvey
  • Observations show intense lightning over Houston which exhibits geographic similarity to climatological maximum lightning flash density
  • To better forecast extreme weather events, it is essential to account for aerosol effects in operational weather forecast models

Hydrology and Land Surface Studies

Open Access

Characterizing Tracer Transport Behavior in Two-Phase Flow System: Implications for CO2 Geosequestration

Minji Kim,  Kue-Young Kim,  Chan Yeong Kim,  Gi-Tak Chae,  Weon Shik Han,  Eungyu Park, 
  • First Published: 16 November 2020
Key Points

  • We present experimental observations with numerical results for characterizing the tracer transport behavior in two-phase flow system
  • The key features of breakthrough curves and tracer velocity highly depend on whether the formation was previously swept by CO2
  • A series of tracer pulse can be used to identify whether new pathways have been developed during CO2 injection

Atmospheric Science

Open Access

A Comparison of Convective Raindrop Size Distributions in the Eyewall and Spiral Rainbands of Typhoon Lekima (2019)

Xuwei Bao,  Liguang Wu,  Shuai Zhang,  Huizhen Yuan,  Huihui Wang, 
  • First Published: 20 November 2020
Key Points

  • A different convective RSD along with shape-slope (μ-Λ) relationship is found in the eyewall and various spiral rainbands of Lekima
  • The average raindrop diameter Dm generally decreases radially from the TC center, whereas the average concentration log10Nw increases
  • Most rain samples with an intense rain rate >50 mm hr−1 are concentrated in the convection-dominated portion of inner rainbands

Open Access

Convective Invigoration Traced to Warm-Rain Microphysics

Xin Rong Chua,  Yi Ming, 
  • First Published: 09 November 2020
Key Points

  • Higher cloud droplet number concentration increases convective mass flux, even in the absence of ice microphysics
  • The convective invigoration coincides with higher tropospheric relative humidity and reevaporation efficiency
  • The dynamical mechanism involves a vertical dipole (cooling-above-warming) pattern

Hydrology and Land Surface Studies

Open Access

Urban Scaling as Validation for Predictions of Imperviousness From Population

Christa Brelsford,  Ethan T. Coon,  Edward Moran V,  Melissa Allen-Dumas, 
  • First Published: 25 November 2020
Key Points

  • Urban Scaling theory can validate process-based models of urban growth, measured by impervious surface area
  • ICLUS projections are consistent with urban scaling theory

Atmospheric Science

Open Access

The Role of Diabatic Heating in Ferrel Cell Dynamics

Orli Lachmy,  Yohai Kaspi, 
  • First Published: 23 November 2020
Key Points

  • Diabatic heating plays a key role in the midlatitude heat budget controlling the Ferrel cell
  • Diabatic heating is concentrated at the Ferrel cell ascending branch during summer and around the Ferrel cell center during winter
  • The diabatic heating rate is positively correlated with the wintertime separation between the eddy heat flux and the eddy-driven jet

Oceans

Open Access

Interannual Variability of the South Atlantic Ocean Heat Content in a High-Resolution Versus a Low-Resolution General Circulation Model

Alexandra Gronholz,  Shenfu Dong,  Hosmay Lopez,  Sang-Ki Lee,  Gustavo Goni,  Molly Baringer, 
  • First Published: 16 November 2020
Key Points

  • Interannual variability of South Atlantic Ocean heat is determined by different mechanisms in high- and low-resolution simulations
  • Signals enter from the south in the high-resolution and from the north in the low-resolution simulation
  • Ekman heat transport contributes significantly in the low-resolution while geostrophic heat transport dominates in the high-resolution

Atmospheric Science

Open Access

Spatial and Temporal Variability of Brown Carbon in the United States: Implications for Direct Radiative Effects

Nicole A. June,  Xuan Wang,  L.-W. Antony Chen,  Judith C. Chow,  John G. Watson,  Xiaoliang Wang,  Barron H. Henderson,  Yiqi Zheng,  Jingqiu Mao, 
  • First Published: 16 November 2020
Key Points

  • Model with whitening can largely reproduce spatial and temporal variability of brown carbon in US.
  • Biogenic SOA appears to be of minor importance to BrC.
  • BrC absorption direct radiative effects appear to be most significant over Arctic region during spring and summer.

Climate

Open Access

Northward Propagation of the Intertropical Convergence Zone and Strengthening of Indian Summer Monsoon Rainfall

Vittal Hari,  Gabriele Villarini,  Subhankar Karmakar,  Laura J. Wilcox,  Mat Collins, 
  • First Published: 20 November 2020
Key Points

  • The dynamics of the Intertropical Convergence Zone has a significant role in changing the characteristics of the Indian monsoon rainfall
  • Since 2002, the ITCZ has strengthened and propagated northward, thereby increasing the magnitude of the Indian monsoon rainfall
  • The reduced aerosol emissions is the main driver of the changing characteristics of ITCZ, which caused the revival of monsoon rainfall

Solid Earth

Open Access

Sinking CO2 in Supercritical Reservoirs

Francesco Parisio,  Victor Vilarrasa, 
  • First Published: 16 November 2020
Key Points

  • We propose a novel geologic carbon storage concept that reduces the buoyancy-driven CO2 leakage risk
  • By injecting CO2 in reservoirs where the resident water stays in supercritical conditions, CO2 sinks because it is denser than pore water
  • Supercritical reservoirs are found at relatively shallow depths between 3 and 5 km in deep volcanic areas

Planets

Open Access

The Ice Content of the Dorsa Argentea Formation From Radar Sounder Data

Jennifer L. Whitten,  Bruce A. Campbell,  Jeffrey J. Plaut, 
  • First Published: 20 November 2020
Key Points

  • Loss tangent values are consistent with the DAF being largely composed of volatile-poor material
  • MARSIS reflections provide evidence that the DAF continues underneath the SPLD
  • Most water ice deposits have not persisted in the DAF through large changes in obliquity

Solid Earth

Open Access

Fault-Zone Damage Promotes Pulse-Like Rupture and Back-Propagating Fronts via Quasi-Static Effects

B. Idini,  J.-P. Ampuero, 
  • First Published: 09 November 2020
Key Points

  • Highly damaged fault zones promote pulse-like ruptures even without the dynamic effects of reflected waves
  • Slip complexity induced by fault damage involves multiple back-propagating rupture fronts
  • A new mechanism for rapid tremor reversals is observed during episodic tremor and slip

Oceans

Open Access

Eddy-Induced Transport and Kinetic Energy Budget in the Arabian Sea

Peng Zhan,  Daquan Guo,  Ibrahim Hoteit, 
  • First Published: 23 November 2020
Key Points

  • Eddy activities and eddy-induced transport play a crucial role in maintaining oceanic heat and salt conditions in the Arabian Sea
  • The western Arabian Sea is identified as a new hot spot in the global ocean with noticeable upward eddy-induced heat transport
  • Baroclinic and barotropic instabilities are the primary sources of eddy kinetic energy in the Arabian Sea

Atmospheric Science

Open Access

Thunderstorm High-Frequency Radio Bursts With Weak Low-Frequency Radiation

Ningyu Y. Liu,  Joseph R. Dwyer, 
  • First Published: 23 November 2020
Key Points

  • A theory is developed to understand the generation mechanism of thunderstorm high-frequency radio bursts with weak low-frequency radiation
  • Many high-frequency radio emitting streamers or streamer-like discharges that propagate in random directions can generate such radio bursts
  • Lightning initiation may begin with a short burst of many randomly occurring small-scale discharges in a localized thundercloud region

Planets

Open Access

Probing Venus Surface Iron Contents With Six-Band Visible Near-Infrared Spectroscopy From Orbit

M. D. Dyar,  J. Helbert,  A. Maturilli,  N. T. Müller,  D. Kappel, 
  • First Published: 29 October 2020
Key Points

  • Accuracies of wt% FeOtotal are ±0.50 for subalkaline rocks, ±0.42 for alkali rocks, and ±2.47 for 440°C lab spectra of both
  • Six-band remote sensed spectra can easily distinguish basalt ( urn:x-wiley:00948276:media:grl61452:grl61452-math-0001 = 9.80 wt% FeO) from granitic/rhyolitic ( urn:x-wiley:00948276:media:grl61452:grl61452-math-0002 = 2.19 wt% FeO) rocks
  • Partial least squares models show that total iron content can be accurately predicted from high-temperature lab spectra

Oceans

Open Access

Subsurface Evolution and Persistence of Marine Heatwaves in the Northeast Pacific

H. A. Scannell,  G. C. Johnson,  L. Thompson,  J. M. Lyman,  S. C. Riser, 
  • First Published: 16 November 2020
Key Points

  • Return of The Blob, with warming and freshening, hence more buoyancy
  • Summertime heatwaves, increase stratification, inhibit mixing
  • Wintertime mixing, warming penetrates the deep, provides memory

Climate

Open Access

Distinguishing Variability Regimes of Hawaiian Summer Rainfall: Quasi-Biennial and Interdecadal Oscillations

Xiao Luo,  Bin Wang,  Abby G. Frazier,  Thomas W. Giambelluca, 
  • First Published: 20 November 2020
Key Points

  • Summer rainfall in Hawai'i has two distinct regimes: quasi-biennial and interdecadal, but no significant trend during 1920–2019
  • The quasi-biennial variability roots in biennial variation of the western North Pacific High driven by ENSO and atmosphere-ocean interaction
  • The interdecadal variation of summer rainfall in Hawai'i is modulated by PDO through affecting the upstream low-level humidity

Solid Earth

Open Access

Size Polydispersity Tunes Slip Avalanches of Granular Gouge

Gang Ma,  Yuxiong Zou,  Ke Gao,  Jidong Zhao,  Wei Zhou, 
  • First Published: 16 November 2020
Key Points

  • The avalanche behaviors from quasi-static shear of granular materials with different size polydispersity are investigated
  • The critical behaviors of granular materials can be tuned by adjusting its size polydispersity
  • The effective temperature volatility can be used to explain the tuned criticality of granular gouge

Atmospheric Science

Open Access

How Does the Tibetan Plateau Dynamically Affect Downstream Monsoon Precipitation?

Jun-Hyeok Son,  Kyong-Hwan Seo,  Bin Wang, 
  • First Published: 23 November 2020
Key Points

  • Topographically forced stationary Rossby wave theory well explains the seasonal evolution of the downstream East Asian precipitation
  • As the season approaches the summer monsoon period, the monsoonal rainband shifts to the west from the western North Pacific to East Asia
  • The subtropical zonal wind impinging on the Tibetan Plateau is a primary factor for the enhancement of meridional wind in the EASM region

Commentaries

Atmospheric Science

Open Access

On the Covariation of Chlorophyll Fluorescence and Photosynthesis Across Scales

Troy S. Magney,  Mallory L. Barnes,  Xi Yang, 
  • First Published: 23 November 2020
Key Points

  • Solar-induced fluorescence (SIF) is widely used as a remote estimate of ecosystem gross primary productivity (GPP), but why does it work?
  • Three recent studies point to inherent nonlinearities in the fluorescence-photosynthesis relationship at fine spatiotemporal scales
  • We synthesize mechanisms to suggest that these results are not contradictory to the increasingly linear SIF:GPP relationship across scales

Research Letters

Planets

Open Access

Boulder Fall Activity in the Jezero Crater, Mars

R. K. Sinha,  A. Rani,  S. J. Conway,  S. Vijayan,  A. Basu Sarbadhikari,  M. Massé,  N. Mangold,  Anil Bhardwaj, 
  • First Published: 09 November 2020
Key Points

  • We report on previously unrecognized boulder fall activity in Jezero crater—landing site of Mars 2020 Perseverance rover
  • Hazardous boulders bigger (length >2.7 m) than the rover have recently fallen on the front of the western delta deposits within the crater
  • Recently fallen boulders may have freshly exposed surfaces, which can be ideal targets for astrobiological investigations by the rover

Atmospheric Science

Open Access

An Analysis of Abandoned Oil Well Characteristics Affecting Methane Emissions Estimates in the Cherokee Platform in Eastern Oklahoma

Patricia M. B. Saint-Vincent,  Matthew D. Reeder,  James I. Sams III,  Natalie J. Pekney, 
  • First Published: 09 November 2020
Key Points

  • Abandoned oil and gas wells are an understudied source of methane emissions
  • Geographic region or oil basin, as well as well depth and plugging status, is related to observed emissions
  • Categorized emissions factors could greatly improve emissions estimates

Open Access

Moisture- Versus Wind-Dominated Flavors of Atmospheric Rivers

Katerina R. Gonzales,  Daniel L. Swain,  Elizabeth A. Barnes,  Noah S. Diffenbaugh, 
  • First Published: 20 November 2020
Key Points

  • Atmospheric rivers (ARs) can be characterized as moisture or wind dominated (“wet” or “windy”)
  • For a given level of vapor transport, “windy” ARs generally produce greater precipitation than do “wet” ARs
  • Pacific Northwest ARs are becoming increasingly moisture dominated

Space Sciences

Open Access

Ionospheric and Solar Wind Contributions to the Storm-Time Near-Earth Plasma Sheet

L. M. Kistler, 
  • First Published: 23 November 2020
Key Points

  • Ionospheric and solar wind sources to the near-earth plasma sheet are tracked during one storm using the AMPTE/CHEM instrument
  • There is a sharp change from a predominantly solar wind to ionospheric source during both intensifications in the storm's main phase
  • The source changes back to predominantly solar wind during the recovery phase

Atmospheric Science

Open Access

Impacts of Traffic Reductions Associated With COVID-19 on Southern California Air Quality

H. A. Parker,  S. Hasheminassab,  J. D. Crounse,  C. M. Roehl,  P. O. Wennberg, 
  • First Published: 23 November 2020
Key Points

  • SoCAB maximum 1-hr NOx and 24-hr PM2.5 concentrations decreased 27% and 29%, respectively, between 19 March and 30 June of 2015–2019 and 2020
  • The 8-hr daily maximum O3 showed inconsistent changes across the basin during the COVID-19 associated decrease of atmospheric NOx concentrations
  • During a shift to a NOx-limited regime, a better understanding of VOC emission sources is needed to improve air quality in the SoCAB

Hydrology and Land Surface Studies

Open Access

Active Sediment Generation on Coral Reef Flats Contributes to Recent Reef Island Expansion

M. R. Ford,  P. S. Kench,  S. D. Owen,  Q. Hua, 
  • First Published: 20 November 2020
Key Points

  • Island merging and expansion were observed over the last 70 yr using remote imagery
  • Radiocarbon dating of recent deposits indicates island growth is driven by the generation of modern sediment
  • Island formation and change were observed over both rising and falling sea level

Open Access

Well Log Generation via Ensemble Long Short-Term Memory (EnLSTM) Network

Yuntian Chen,  Dongxiao Zhang, 
  • First Published: 16 November 2020
Key Points

  • We proposed an ensemble long short-term memory (EnLSTM) network to process sequential data based on a small dataset
  • The EnLSTM solved a well log generation problem with higher prediction accuracy than the previously best model on a published dataset
  • The EnLSTM accurately generated 12 hard-to-measure well logs based on LWD logs, resulting in a reduction of cost and time in practice

Oceans

Open Access

Spatial Variability of Antarctic Bottom Water in the Australian Antarctic Basin From 2018–2020 Captured by Deep Argo

George Thomas,  Sarah G. Purkey,  Dean Roemmich,  Annie Foppert,  Stephen R. Rintoul, 
  • First Published: 17 October 2020
Key Points

  • A new Deep Argo pilot array improves spatial and temporal resolution of bottom water sampling in the Australian Antarctic Basin
  • The floats capture the return of high salinity Ross Sea Bottom Water to the region after a period of multi-decadal freshening
  • A simple Optimum Multiparameter calculation quantifies the local zonal variation in the new water mass concentrations from 2018 to 2020

Hydrology and Land Surface Studies

Open Access

Annually Resolved Monsoon Onset and Withdrawal Dates Across the Himalayas Derived From Local Precipitation Statistics

C. F. Brunello,  C. Andermann,  O. Marc,  K. A. Schneider,  F. Comiti,  S. Achleitner,  N. Hovius, 
  • First Published: 23 November 2020
Key Points

  • We propose a new statistical definition of monsoon onset and withdrawal applicable a posteriori to daily precipitation time series
  • Monsoon bounds show longitudinal delays and strong year-to-year variations, crossing commonly used seasonal calendric boundaries
  • The long-term increase of annual precipitation in Nepal seems to be driven primarily by higher premonsoon rainfall

Atmospheric Science

Open Access

Two Propagation Scenarios of Isolated Breakdown Lightning Processes in Failed Negative Cloud-to-Ground Flashes

Ivana Kolmašová,  Ondřej Santolík,  Eric Defer,  Petr Kašpar,  Andrea Kolínská,  Stéphane Pedeboy,  Sylvain Coquillat, 
  • First Published: 16 November 2020
Key Points

  • Preliminary breakdown radio wave pulses typical for negative cloud-to-ground flashes are exceptionally observed without return strokes
  • Data show evidence of two possible propagation scenarios: The discharge leader either extends horizontally inside the cloud or fades out
  • The first analysis of a large number of events shows that waveform characteristics of pulse trains are very similar for both scenarios

Climate

Open Access

Interdecadal Pacific Oscillation Drives Enhanced Greenland Surface Temperature Variability During the Last Glacial Maximum

Zhaoyang Song,  Mojib Latif,  Wonsun Park,  Yuming Zhang, 
  • First Published: 23 November 2020
Key Points

  • Oxygen isotope records and climate modeling show large reductions in Greenland surface temperature variability from the LGM to modern times
  • Atmospheric teleconnections from the Interdecadal Pacific Oscillation intensify under glacial conditions
  • Greenland surface temperature is forced by atmospheric heat transport and sea ice linked to the Interdecadal Pacific Oscillation

Space Sciences

Open Access

Temporal Evolution of Flux Tube Entanglement at the Magnetopause as Observed by the MMS Satellites

Y. Qi,  C. T. Russell,  Ying-Dong Jia,  M. Hubbert, 
  • First Published: 20 November 2020
Key Points

  • IMF clock angles associated with 17 flux tube entanglement events present peaks near horizontal direction
  • The entanglement process evolves in three distinguishable stages
  • Magnetic tension force contributes to the pressure balance at the entanglement interface

Open Access

Relation Between Shock-Related Impulse and Subsequent ULF Wave in the Earth's Magnetosphere

Dianjun Zhang,  Wenlong Liu,  Xinlin Li,  Theodore E. Sarris,  Yongfu Wang,  Chao Xiao,  Zhao Zhang,  John R. Wygant, 
  • First Published: 20 November 2020
Key Points

  • The 51 shock-related impulse events are investigated based on Van Allen Probes measurement with 39% of them followed by poloidal ULF wave while 61% not
  • The time scale of shock-induced electric field impulse is more related to fast-mode wave propagation than field line resonance
  • The shock-related ULF wave is more likely excited when the shock-induced impulse's equivalent frequency matches the local eigenfrequency

Climate

Open Access

Seasonal Dependent Impact of Ice Cloud Longwave Scattering on the Polar Climate

Yi-Hsuan Chen,  Xianglei Huang,  Ping Yang,  Chia-Pang Kuo,  Xiuhong Chen, 
  • First Published: 23 November 2020
Key Points

  • Cloud longwave scattering is more important in the polar regions than the extrapolar regions
  • By surface-atmosphere radiative coupling, cloud longwave scattering can warm the polar surface, more in the winter than in the summer
  • Cloud longwave scattering is a necessity instead of an option for correctly simulating polar climate and surface energy budget

Atmospheric Science

Open Access

Revealing the Dynamical Transition of Anisotropy Behind the HOST by Koopman Analysis

Licheng Li,  Hongchao Zuo,  Bolong Chen,  Yang Guo,  Mengmeng Ma,  Longxiang Dong, 
  • First Published: 09 November 2020
Key Points

  • The Koopman operator is acted on the Ri series to discover the primary mode of coherent structures effected by submesoscale motions
  • The horizontal kinetic energy transport with a vertical downward flux coupled mechanism causes the unique evolution of turbulence anisotropy
  • A group of quadratic curves is discovered about the shear and vertical momentum when the anisotropy crossed over the transition point

Hydrology and Land Surface Studies

Open Access

Efficiency of the Summer Monsoon in Generating Streamflow Within a Snow-Dominated Headwater Basin of the Colorado River

Rosemary W. H. Carroll,  David Gochis,  Kenneth H. Williams, 
  • First Published: 23 November 2020
Key Points

  • Monsoon rains generate 10 ± 6% of annual streamflow while late spring snowfall delivers twice as much for the same water input
  • The influence of monsoon rain on streamflow is half of late spring snow due to evapotranspiration in the lower subalpine forest
  • Monsoon efficiency in generating streamflow decreases in warm years with low snow accumulation

Atmospheric Science

Open Access

High Temporal Resolution Satellite Observations of Fire Radiative Power Reveal Link Between Fire Behavior and Aerosol and Gas Emissions

Elizabeth B. Wiggins,  Amber J. Soja,  Emily Gargulinski,  Hannah S. Halliday,  R. Bradley Pierce,  Christopher C. Schmidt,  John B. Nowak,  Joshua P. DiGangi,  Glenn S. Diskin,  Joseph M. Katich,  Anne E. Perring,  Joshua P. Schwarz,  Bruce E. Anderson,  Gao Chen,  Ewan C. Crosbie,  Carolyn Jordan,  Claire E. Robinson,  Kevin J. Sanchez,  Taylor J. Shingler,  Michael Shook,  Kenneth L. Thornhill,  Edward L. Winstead,  Luke D. Ziemba,  Richard H. Moore, 
  • First Published: 23 November 2020
Key Points

  • Geostationary satellite observations of fire radiative power are highly correlated with in situ airborne measurements of primary-emission smoke tracers
  • High-resolution satellite observations are needed to disentangle how fire activity and plume dilution impact the downwind evolution of smoke
  • Diurnal fire activity for wildfires observed during FIREX-AQ is best parameterized using a bimodal Gaussian distribution to inform models

Solid Earth

Open Access

Mapping the Sources of Proximal Earthquake Infrasound

J. B. Johnson,  T. D. Mikesell,  J. F. Anderson,  L. M. Liberty, 
  • First Published: 23 November 2020
Key Points

  • A network of arrays is used to locate proximal infrasound sources for a M3.6 Idaho earthquake
  • “Local infrasound” (at recording site) and “secondary infrasound” (from the epicentral region and from elevated topography) are identified
  • Intermediate slowness values are common and are attributed to superposition of subhorizontal and subvertical propagating infrasound

Hydrology and Land Surface Studies

Open Access

Microwave Retrievals of Soil Moisture Improve Grassland Wildfire Predictions

Angela J. Rigden,  Robert S. Powell,  Aleyda Trevino,  Kaighin A. McColl,  Peter Huybers, 
  • First Published: 02 November 2020
Key Points

  • Using remotely sensed soil moisture and vapor pressure deficit allows for more skillful wildfire prediction
  • Improvements are for when vapor pressure deficit already indicates higher fire risk
  • Improvements are greater for grasslands than for shrublands or forests

Solid Earth

Open Access

A Subgrain-Size Piezometer Calibrated for EBSD

R. M. Goddard,  L. N. Hansen,  D. Wallis,  M. Stipp,  C. W. Holyoke III,  K. M. Kumamoto,  D. L. Kohlstedt, 
  • First Published: 10 November 2020
Key Points

  • We present a new subgrain-size piezometer calibrated for EBSD, with a 1° critical misorientation angle
  • This subgrain-size piezometer can be applied to multiple minerals and appears to be independent of the deformation geometry
  • This subgrain-size piezometer should be unaffected by the presence of secondary minerals and thus applicable to polymineralic rocks

Open Access

Repeating Earthquakes With Remarkably Repeatable Ruptures on the San Andreas Fault at Parkfield

Rachel E. Abercrombie,  Xiaowei Chen,  Jiewen Zhang, 
  • First Published: 16 November 2020
Key Points

  • All individual earthquakes in a repeating sequence at Parkfield exhibit identical directivity, unaffected by 2004 M6
  • One sequence (M ~ 2.7) ruptures to the NW and one (M ~ 2.5) to the SE, at ~0.8 × shear wave velocity
  • Smallest magnitude sequences show most response to M6 earthquake, but we cannot fully distinguish between path and source effects

Atmospheric Science

Open Access

Revealing the Intensity of Turbulent Energy Transfer in Planetary Atmospheres

Simon Cabanes,  Stefania Espa,  Boris Galperin,  Roland M. B. Young,  Peter L. Read, 
  • First Published: 16 November 2020
Key Points

  • We present a new and universal diagnostic to reveal the intensity of turbulent energy transfer in planetary atmospheres
  • We show that turbulent energy transfer in Saturn's atmosphere is 4 times less intense than Jupiter's

Space Sciences

Open Access

A Long-Lasting Auroral Spiral Rotating Around Saturn's Pole

B. Palmaerts,  Z. H. Yao,  N. Sergis,  R. L. Guo,  D. Grodent,  K. Dialynas,  J.-C. Gérard,  D. G. Mitchell, 
  • First Published: 23 November 2020
Key Points

  • The main auroral emission forms a spiral observed during two consecutive days
  • The spiral morphology is due to the presence of a hot plasma population in the magnetodisc
  • The auroral spiral winds while the hot plasma bubble expands due to gradient and curvature drifts

Oceans

Open Access

Shear Instability and Turbulence Within a Submesoscale Front Following a Storm

Jeffrey R. Carpenter,  Arthur Rodrigues,  Larissa K. P. Schultze,  Lucas M. Merckelbach,  Nobuhiro Suzuki,  Burkard Baschek,  Lars Umlauf, 
  • First Published: 20 November 2020
Key Points

  • An autonomous ocean glider observed turbulence, currents, and stratification in surface mixed layer submesoscale fronts following a storm
  • Submesoscale fronts provide both a damping and generation of surface mixed layer turbulence
  • Shear instability within the front could represent a significant energy transfer in frontal evolution

Climate

Open Access

An Abrupt Aging of Dissolved Organic Carbon in Large Arctic Rivers

Melissa S. Schwab,  Robert G. Hilton,  Peter A. Raymond,  Negar Haghipour,  Edwin Amos,  Suzanne E. Tank,  Robert M. Holmes,  Edward T. Tipper,  Timothy I. Eglinton, 
  • First Published: 04 November 2020
Key Points

  • A widespread pulse of aged dissolved organic carbon (DOC) occurred in the Mackenzie River and its tributaries in June 2018
  • Export of aged DOC is consistent with a prolonged warming period and the formation of supra-permafrost taliks
  • Mobilization of aged DOC and nitrate suggests percolation of supra-permafrost groundwater through previously frozen soil layers

Open Access

Larger Sensitivity of Arctic Precipitation Phase to Aerosol than Greenhouse Gas Forcing

Shifeng Pan,  Tingfeng Dou,  Lei Lin,  Jiao Yang,  Feng Zhang,  Mingkeng Duan,  Chuanfeng Zhao,  Hong Liao,  Cunde Xiao, 
  • First Published: 20 November 2020
Key Points

  • Warming forced by global aerosol reduction and increased GHG emission leads to a solid-to-liquid precipitation transition in the Arctic
  • The sensitivity of Arctic precipitation phase to the aerosol forcing is approximately three times that to the GHG forcing
  • The most sensitive phase changes of Arctic precipitation to the aerosol forcing are observed in Greenland and the eastern Arctic Ocean

Oceans

Open Access

Eddy-Like Features Near St. Matthew Island, Eastern Bering Sea Shelf: Observations From the Oculus Coastal Glider

C. Ladd,  S. W. Bell,  D. G. Kimmel,  C. W. Mordy,  P. J. Stabeno,  S. Stalin, 
  • First Published: 09 November 2020
Key Points

  • Glider observations allowed identification of eddy-like features within the north/south transition zone of the eastern Bering Sea Shelf
  • Eddy-like features resulted in shallower deep chlorophyll maxima and were associated with coastal waters around St. Matthew Island
  • These features had not been previously observed during 15 years of ship surveys due to lower horizontal resolution sampling

Cryosphere

Open Access

Repeat Subglacial Lake Drainage and Filling Beneath Thwaites Glacier

G. Malczyk,  N. Gourmelen,  D. Goldberg,  J. Wuite,  T. Nagler, 
  • First Published: 09 November 2020
Key Points

  • There is evidence of drainage and filling of sub-glacial lakes under Thwaites Glacier in 2017, four years after previous activity
  • There is contrasting lake behavior, drainage volume, discharge, and timing of drainage onset between the 2013 and 2017 events
  • Observations of recharge rates suggest that modeled melt water production is underestimated