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Geophysical Research Letters | Page 2

A N Jaynes, A F Ali, S R Elkington, D M Malaspina, D N Baker, X Li, S G Kanekal, M G Henderson, C A Kletzing, J R Wygant
Inward radial diffusion driven by ULF waves has long been known to be capable of accelerating radiation belt electrons to very high energies within the heart of the belts, but more recent work has shown that radial diffusion values can be highly event-specific, and mean values or empirical models may not capture the full significance of radial diffusion to acceleration events. Here we present an event of fast inward radial diffusion, occurring during a period following the geomagnetic storm of 17 March 2015...
October 28, 2018: Geophysical Research Letters
G Myhre, R J Kramer, C J Smith, Ø Hodnebrog, P Forster, B J Soden, B H Samset, C W Stjern, T Andrews, O Boucher, G Faluvegi, D Fläschner, M Kasoar, A Kirkevåg, J-F Lamarque, D Olivié, T Richardson, D Shindell, P Stier, T Takemura, A Voulgarakis, D Watson-Parris
Different climate drivers influence precipitation in different ways. Here we use radiative kernels to understand the influence of rapid adjustment processes on precipitation in climate models. Rapid adjustments are generally triggered by the initial heating or cooling of the atmosphere from an external climate driver. For precipitation changes, rapid adjustments due to changes in temperature, water vapor, and clouds are most important. In this study we have investigated five climate drivers (CO2 , CH4 , solar irradiance, black carbon, and sulfate aerosols)...
October 28, 2018: Geophysical Research Letters
Eurico J D'Sa, Ishan Joshi, Bingqing Liu
Dissolved and particulate organic carbon, suspended particulate matter concentrations, and their optical proxies colored dissolved organic matter absorption and backscattering coefficients were studied in Galveston Bay, Texas, following the extreme flooding of Houston and surrounding areas due to Hurricane Harvey (25-29 August 2017) using field and ocean color observations. A three-step empirical-semianalytic algorithm for determination of colored dissolved organic matter absorption and backscattering coefficients revealed the dynamics of dissolved organic carbon and particle distribution from Visible and Infrared Imaging Radiometric Suite ocean color...
October 16, 2018: Geophysical Research Letters
Evan S Miles, Ian Willis, Pascal Buri, Jakob F Steiner, Neil S Arnold, Francesca Pellicciotti
Glaciers in High Mountain Asia, many of which exhibit surface debris, contain the largest volume of ice outside of the polar regions. Many contain supraglacial pond networks that enhance melt rates locally, but no large-scale assessment of their impact on melt rates exists. Here we use surface energy balance modeling forced using locally measured meteorological data and monthly satellite-derived pond distributions to estimate the total melt enhancement for the four main glaciers within the 400-km2 Langtang catchment, Nepal, for a 6-month period in 2014...
October 16, 2018: Geophysical Research Letters
Dimitris A Herrera, Toby R Ault, John T Fasullo, Sloan J Coats, Carlos M Carrillo, Benjamin I Cook, A Park Williams
The Caribbean islands are expected to see more frequent and severe droughts from reduced precipitation and increased evaporative demand due to anthropogenic climate change. Between 2013 and 2016, the Caribbean experienced a widespread drought due in part to El Niño in 2015-2016, but it is unknown whether its severity was exacerbated by anthropogenic warming. This work examines the role of recent warming on this drought, using a recently developed high-resolution self-calibrating Palmer Drought Severity Index data set...
October 16, 2018: Geophysical Research Letters
Scott R Stephenson, Wenshan Wang, Charles S Zender, Hailong Wang, Steven J Davis, Philip J Rasch
As global temperatures increase, sea ice loss will increasingly enable commercial shipping traffic to cross the Arctic Ocean, where the ships' gas and particulate emissions may have strong regional effects. Here we investigate impacts of shipping emissions on Arctic climate using a fully coupled Earth system model (CESM 1.2.2) and a suite of newly developed projections of 21st-century trans-Arctic shipping emissions. We find that trans-Arctic shipping will reduce Arctic warming by nearly 1 °C by 2099, due to sulfate-driven liquid water cloud formation...
September 28, 2018: Geophysical Research Letters
Kathrin Wehrli, Benoit P Guillod, Mathias Hauser, Matthieu Leclair, Sonia I Seneviratne
Global climate models present systematic biases, among others, a tendency to overestimate hot and dry summers in midlatitude regions. Here we investigate the origin of such biases in the Community Earth System Model. To disentangle the contribution of dynamics and thermodynamics, we perform simulations that include nudging of horizontal wind and compare them to simulations with a free atmosphere. Prescribing the observed large-scale circulation improves the modeled weather patterns as well as many related fields...
August 28, 2018: Geophysical Research Letters
H K Nowell, C D Holmes, K Robertson, C Teske, J K Hiers
Florida, United States, government records provide a new resource for studying fire in landscapes managed with prescribed fire. In Florida, most fire area (92%) is prescribed. Current satellite fire products, which underpin most air pollution emission inventories, detect only 25% of burned area, which alters airborne emissions and environmental impacts. Moreover, these satellite products can misdiagnose spatiotemporal variability of fires. Overall fire area in Florida decreases during drought conditions as prescribed fires are avoided, but satellite data do not reflect this pattern...
August 16, 2018: Geophysical Research Letters
Lukas Brunner, Nathalie Schaller, James Anstey, Jana Sillmann, Andrea K Steiner
The impact of atmospheric blocking on European heat waves (HWs) and cold spells (CSs) is investigated for present and future conditions . A 50-member ensemble of the second generation Canadian Earth System Model is used to quantify the role of internal variability in the response to blocking. We find that the present blocking-extreme temperature link is well represented compared to ERA-Interim, despite a significant underestimation of blocking frequency in most ensemble members. Our results show a strong correlation of blocking with northern European HWs in summer, spring, and fall...
June 28, 2018: Geophysical Research Letters
Piercarlo Giacomel, Elena Spagnuolo, Manuela Nazzari, Andrea Marzoli, François Passelegue, Nasrrddine Youbi, Giulio Di Toro
The safe application of geological carbon storage depends also on the seismic hazard associated with fluid injection. In this regard, we performed friction experiments using a rotary shear apparatus on precut basalts with variable degree of hydrothermal alteration by injecting distilled H2 O, pure CO2 , and H2 O + CO2 fluid mixtures under temperature, fluid pressure, and stress conditions relevant for large-scale subsurface CO2 storage reservoirs. In all experiments, seismic slip was preceded by short-lived slip bursts...
June 28, 2018: Geophysical Research Letters
X Ma, H Jia, F Yu, J Quaas
The Moderate Resolution Imaging Spectroradiometer (MODIS) C6 L3 and the European Centre for Medium-Range Weather Forecasts (ECMWF) ERA-Interim reanalysis data from 2003 to 2016 are employed to study aerosol-cloud correlations over three industrial regions and their adjacent oceans, as well as explore the impact of meteorological conditions on the correlations. The analysis focusing on liquid and single-layer clouds indicates an opposite aerosol-cloud correlation between land and ocean; namely, cloud effective radius is positively correlated with aerosol index over industrial regions (positive slopes), but negatively correlated over their adjacent oceans (negative slopes), for a quasi-constant liquid water path...
June 16, 2018: Geophysical Research Letters
Catherine A Rychert, Nick Harmon
The ocean lithosphere is classically described by the thermal half-space cooling (HSC) or the plate models, both characterized by a gradual transition to the asthenosphere beneath. Scattered waves find sharp seismic discontinuities beneath the oceans, possibly from the base of the plate. Active source studies suggest sharp discontinuities from a melt channel. We calculate synthetic S -to- P receiver functions and SS precursors for the HSC and plate models and also for channels. We find that the HSC and plate model velocity gradients are too gradual to create interpretable scattered waves from the base of the plate...
June 16, 2018: Geophysical Research Letters
J P Eastwood, R Mistry, T D Phan, S J Schwartz, R E Ergun, J F Drake, M Øieroset, J E Stawarz, M V Goldman, C Haggerty, M A Shay, J L Burch, D J Gershman, B L Giles, P A Lindqvist, R B Torbert, R J Strangeway, C T Russell
Magnetospheric Multiscale observations are used to probe the structure and temperature profile of a guide field reconnection exhaust ~100 ion inertial lengths downstream from the X-line in the Earth's magnetosheath. Asymmetric Hall electric and magnetic field signatures were detected, together with a density cavity confined near 1 edge of the exhaust and containing electron flow toward the X-line. Electron holes were also detected both on the cavity edge and at the Hall magnetic field reversal. Predominantly parallel ion and electron heating was observed in the main exhaust, but within the cavity, electron cooling and enhanced parallel ion heating were found...
May 28, 2018: Geophysical Research Letters
Krzysztof Wargan, Clara Orbe, Steven Pawson, Jerald R Ziemke, Luke D Oman, Mark A Olsen, Lawrence Coy, K Emma Knowland
1998-2016 ozone trends in the lower stratosphere (LS) are examined using the Modern-Era Retrospective Analysis for Research and Applications Version 2 (MERRA-2) and related NASA products. After removing biases resulting from step-changes in the MERRA-2 ozone observations, a discernible negative trend of -1.67±0.54 Dobson units per decade (DU/decade) is found in the 10-km layer above the tropopause between 20°N and 60°N. A weaker but statistically significant trend of -1.17±0.33 DU/decade exists between 50°S and 20°S...
May 28, 2018: Geophysical Research Letters
W T Crow, F Chen, R H Reichle, Y Xia, Q Liu
Accurate partitioning of precipitation into infiltration and runoff is a fundamental objective of land surface models tasked with characterizing the surface water and energy balance. Temporal variability in this partitioning is due, in part, to changes in pre-storm soil moisture, which determine soil infiltration capacity and unsaturated storage. Utilizing the NASA Soil Moisture Active Passive Level-4 soil moisture product in combination with streamflow and precipitation observations, we demonstrate that land surface models (LSMs) generally underestimate the strength of the positive rank correlation between pre-storm soil moisture and event runoff coefficients (i...
May 28, 2018: Geophysical Research Letters
C Köhn, O Chanrion, T Neubert
Bursts of X-rays and γ -rays are observed from lightning and laboratory sparks. They are bremsstrahlung from energetic electrons interacting with neutral air molecules, but it is still unclear how the electrons achieve the required energies. It has been proposed that the enhanced electric field of streamers, found in the corona of leader tips, may account for the acceleration; however, their efficiency is questioned because of the relatively low production rate found in simulations. Here we emphasize that streamers usually are simulated with the assumption of homogeneous gas, which may not be the case on the small temporal and spatial scales of discharges...
May 28, 2018: Geophysical Research Letters
Tom Goren, Daniel Rosenfeld, Odran Sourdeval, Johannes Quaas
This study examines the relationships between marine stratocumulus clouds (MSC) coupling state with the ocean surface, their precipitation rate and fractional cloud cover (CF). This was possible by developing a novel methodology for satellite retrieval of the clouds coupling state. Decks of overcast MSC were reported in previous studies to break up often as their precipitation rate increases significantly, thus reducing CF and cloud radiative effect substantially. Here we show that decks of precipitating decoupled MSC have larger CF compared to similarly precipitating coupled MSC...
May 28, 2018: Geophysical Research Letters
Clemens Schwingshackl, Martin Hirschi, Sonia I Seneviratne
The evolution of near-surface air temperature is influenced by various dynamical, radiative, and surface-atmosphere exchange processes whose contributions are still not completely quantified. Applying stepwise multiple linear regression to Coupled Model Intercomparison Project phase 5 (CMIP5) model simulations and focusing on radiation (diagnosed by incoming shortwave and incoming longwave radiation) and land surface conditions (diagnosed by soil moisture and albedo) about 79% of the interannual variability and 99% of the multidecadal trend of monthly mean daily maximum temperature over land can be explained...
May 28, 2018: Geophysical Research Letters
Tianle Yuan, Lazaros Oreopoulos, Steven E Platnick, Kerry Meyer
Modeling studies have shown that cloud feedbacks are sensitive to the spatial pattern of sea surface temperature (SST) anomalies, while cloud feedbacks themselves strongly influence the magnitude of SST anomalies. Observational counterparts to such patterned interactions are still needed. Here we show that distinct large-scale patterns of SST and low-cloud cover (LCC) emerge naturally from objective analyses of observations and demonstrate their close coupling in a positive local SST-LCC feedback loop that may be important for both internal variability and climate change...
May 16, 2018: Geophysical Research Letters
Andreas Fichtner, Dirk-Philip van Herwaarden, Michael Afanasiev, Saulė Simutė, Lion Krischer, Yeşim Çubuk-Sabuncu, Tuncay Taymaz, Lorenzo Colli, Erdinc Saygin, Antonio Villaseñor, Jeannot Trampert, Paul Cupillard, Hans-Peter Bunge, Heiner Igel
We present a general concept for evolutionary, collaborative, multiscale inversion of geophysical data, specifically applied to the construction of a first-generation Collaborative Seismic Earth Model. This is intended to address the limited resources of individual researchers and the often limited use of previously accumulated knowledge. Model evolution rests on a Bayesian updating scheme, simplified into a deterministic method that honors today's computational restrictions. The scheme is able to harness distributed human and computing power...
May 16, 2018: Geophysical Research Letters
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