Browse Articles
Annual Appearance of Hydrogen Chloride on Mars and a Striking Similarity With the Water Vapor Vertical Distribution Observed by TGO/NOMAD
-  3 June 2021
Key Points
-
Increase of hydrogen chloride (HCl) during the southern summer is annually repeated. It shows that HCl formation is independent from a global dust storm
-
Vertical distributions of HCl are strikingly similar to water vapor. It suggests that uptake by water ice clouds plays an important role
-
A rapid decrease of HCl at the end of the southern summer suggests the presence of a strong sink in addition to the photochemical loss
Revisiting Acetonitrile as Tracer of Biomass Burning in Anthropogenic‐Influenced Environments
-  1 June 2021
Key Points
-
Several ppbv of CH3CN can be measured in anthropogenic-influenced environments with minor biomass burning impact
-
Good correlation between high CH3CN and CO were revealed showing their shared sources in anthropogenic-influenced environments
-
Biomass burning can be distinguished from other CH3CN sources using the enhancement ratios of CH3CN and CO
Evidence and Inferred Mechanism of Collisions of Downward Stepped‐Leader Branches in Negative Lightning
-  1 June 2021
Key Points
-
A negative stepped leader branch tip can collide with the lateral surface of adjacent branch, as previously observed for streamers
-
Collision can be caused by the attracting force of upward moving positive-charge wave associated with stepping at the leading branch tip
-
A heavily branched negative leader creates a highly structured and rapidly changing electric field pattern inside the volume it occupies
Mid‐Latitude Thermosphere‐Ionosphere Na (TINa) Layers Observed With High‐Sensitivity Na Doppler Lidar Over Boulder (40.13°N, 105.24°W)
-  1 June 2021
Key Points
-
Tenuous thermosphere-ionosphere Na (TINa) layers occur regularly descending from ∼150 km before dawn and from ∼125 km after dusk with semidiurnal tidal phase speeds
-
Enhanced mixing ratios above the Na slope turning points suggest in situ production of TINa via neutralization of converged TINa+ layers
-
Vertical drift velocity of TINa+ calculated with inferred tidal winds shows convergent flow phases aligned well with Boulder TINa layers
The Long Sinuous Rille System in Northern Oceanus Procellarum and Its Relation to the Chang'e‐5 Returned Samples
-  31 May 2021
Key Points
-
The lunar sinuous rille Rima Sharp is associated with the mare unit sampled by Chang'e-5, and may have emplaced the unit
-
Rima Sharp is actually formed by two rilles, ∼320 km long Rima Sharp and ∼150 long km Rima Mairan, that meet in the middle of the unit
-
Rima Sharp formed first, emplacing most of the lava forming the young basalt unit, followed closely by Rima Mairan, embaying Rima Sharp
Magnetopause Reconnection and Indents Induced by Foreshock Turbulence
-  31 May 2021
Key Points
-
Foreshock turbulence can reach the magnetopause under a northward quasi-radial interplanetary magnetic field with zero dawn-dusk component
-
The turbulence can create large magnetic shear angles across the magnetopause, leading to local bursty reconnection
-
Bombardments of the turbulence cause Earth-sized magnetopause indents under constant interplanetary magnetic field and solar wind
Nonmonotonic Change of the Arctic Ocean Freshwater Storage Capability in a Warming Climate
-  25 May 2021
Key Points
-
Sea ice decline leads to both enhanced freshwater Ekman transport and increased occupation of Atlantic-origin water in the Arctic Ocean
-
Counterbalance between the two processes renders a first increasing and then decreasing liquid freshwater content while sea ice declines
-
Stronger river runoff modulates the counterbalance and causes nonmonotonic changes of freshwater storage capability in a warming world
Robust asymmetry of the future Arctic polar vortex is driven by tropical Pacific warming
-  2 June 2021
Key Points
-
The Arctic stratospheric cooling in the future is most pronounced over Eurasia, whereas over North America stratospheric warming occurs
-
Tropical Pacific warming takes the place of Arctic sea ice loss as the dominating forcing of the polar vortex
-
The asymmetric polar vortex could act to increase the cold extreme events over mid- to high-latitudes of Eurasia in the near future
Storm Waves may be the Source of Some ‘Tsunami’ Coastal Boulder Deposits
-  1 June 2021
Key Points
-
Size, elevation, and distance inland in storm-wave-generated coastal boulder deposits are all functions of climatological wave heights
-
Clear data ranges exist where storm wave coastal boulder deposits do/do not exist
-
Some coastal boulder deposits previously identified as having tsunami origin may have been generated by storm waves
Evidence of the 1950 great Assam earthquake surface break along the Mishmi Thrust at Namche Barwa Himalayan Syntaxis
-  1 June 2021
Key Points
-
We provide the first evidence of surface rupture by the 1950 great Assam earthquake from the Mishmi Thrust in the eastern syntaxis.
-
We suggest a dual rupture style for the 1950 earthquake along the Himalayan Frontal Thrust and Mishmi Thrust.
-
A slip deficit of ∼1.4 m since 1950 is capable to generate an earthquake of Mw ∼7.7 along the Mishmi Thrust in the present day.
Modelling Antarctic krill circumpolar spawning habitat quality to identify regions with potential to support high larval production
-  1 June 2021
Key Points
-
Mechanistic model for Antarctic krill spawning habitat uses thermal and food constraints on egg production, and predation on egg survival.
-
Optimizing from regional data we generate circumpolar predictions to show half of quality spawning habitat is in the southwest Atlantic.
-
Spatial management units for the krill fishery do not all represent optimal spawning habitat, suggesting some areas rely on recruit import.
Zircon U‐Pb geochronology constrains continental expression of Great Meteor Hotspot magmatism
-  1 June 2021
Key Points
-
Zircon U-Pb geochronology tests hotspot model for origin of continental magmatism typically associated with the Great Meteor Hotspot
-
New ages indicate a relatively brief episode of magmatism at ca. 122.8 – 126.1 Ma
-
Modeled hotspot tracks spatially consistent with igneous centers but generally underestimate timing of magmatism by ca. 10 Myr
Subsurface heat channel drove sea surface warming in the high‐latitude North Atlantic during the Mid‐Pleistocene Transition
-  1 June 2021
Key Points
-
Warming of the subtropical gyre at depth strengthens the subsurface heat transport from the subtropical gyre to the subpolar gyre
-
Precession-paced northward heat transport may affect ice-sheet mass balance by either contributing moisture or triggering destabilization
-
Onset of precession-paced northward heat transport began around 930 ka, promoting the transition to 100-kyr cyclicity
Spatial, temporal, and multivariate bias in regional climate model simulations
-  1 June 2021
Key Points
-
RCM simulations with bias corrected GCM boundary conditions better capture both temporal and spatial dependence of surface variables.
-
RCM simulations show reasonable performance for spatial dependence, implying it is the RCM that imparts the spatial relationships observed.
-
All RCM simulations do not show improvement in the dependence across variables.
Hot spots of glacier mass balance variability in Central Asia
-  1 June 2021
Key Points
-
Annual glacier mass balance for Central Asia (1999/00–2017/18) is derived by combining transient snowlines, geodetic surveys and modelling.
-
Strong spatio-temporal heterogeneity with contrasting patterns of mass gain and loss are found.;
-
Hot spots of heterogeneous mass balance variability are associated with highly variable glacier melt water runoff.
Tropical Stratospheric Circulation and Ozone Coupled to Pacific Multi‐Decadal Variability
-  1 June 2021
Key Points
-
Low frequency variability in the Brewer-Dobson circulation is coupled with low frequency Pacific Ocean sea surface temperature variability
-
Accounting for this allows the detection of an enhanced Brewer-Dobson circulation trend in model hindcasts of 7–10% dec-1 over 1979–2010
-
The low frequency variability also explains 50% of the observed trends in mid-stratospheric tropical ozone from 1990 to 2010
Temporal Seismic Velocity Changes During the 2020 Rapid Inflation at Mt. Þorbjörn‐Svartsengi, Iceland, Using Seismic Ambient Noise
-  1 June 2021
Key Points
-
Ambient noise-based temporal seismic wave velocity variations provide insights into volcanic unrest in the Reykjanes Peninsula
-
Seismic velocity drops down to -1% during repeated magma intrusions
-
The evolution of dv/v (%) correlates with deformation data
The Atlantic Multidecadal Oscillation and its relation to rainfall and river flows in the continental U.S.
- Geophysical Research Letters
-  2077-2080
-  15 May 2001
The Arctic oscillation signature in the wintertime geopotential height and temperature fields
- Geophysical Research Letters
-  1297-1300
-  1 May 1998
The gravity recovery and climate experiment: Mission overview and early results
- Geophysical Research Letters
-  8 May 2004
Global depletion of groundwater resources
- Geophysical Research Letters
-  26 October 2010
Radar interferogram filtering for geophysical applications
- Geophysical Research Letters
-  4035-4038
-  1 November 1998
Evidence linking Arctic amplification to extreme weather in mid‐latitudes
- Geophysical Research Letters
-  17 March 2012
Key Points
- Enhanced Arctic warming reduces poleward temperature gradient
- Weaker gradient affects waves in upper-level flow in two observable ways
- Both effects slow weather patterns, favoring extreme weather
A generalized approach to parameterizing convection combining ensemble and data assimilation techniques
- Geophysical Research Letters
-  38-1-38-4
-  25 July 2002
A global inventory of lakes based on high‐resolution satellite imagery
- Geophysical Research Letters
-  6396-6402
-  12 August 2014
Key Points
- Earth has 117 million lakes > 0.002 km2
- Large and intermediate lakes dominate the total surface area of lakes
- Power law-based extrapolations do not adequately estimate lake abundance
Large wildfire trends in the western United States, 1984–2011
- Geophysical Research Letters
-  2928-2933
-  4 April 2014
Key Points
- Number of large fires and large fire area have increased across the western U.S.
- Fire activity trends were most significant in southern and mountain ecoregions
- Increased fire in these ecoregions coincided with increased drought severity
Polar Drift in the 1990s Explained by Terrestrial Water Storage Changes
- Geophysical Research Letters
-  22 March 2021
Key Points
-
Past climate-driven polar motion was quantified by modeling terrestrial water storage under two different scenarios
-
One scenario was based on GRACE and reanalysis data; another scenario was based on extra glacier change observations
-
Rapid terrestrial water storage decline caused by ice melting over glacial areas drove the polar drift toward the east in the 1990s
Plain Language Summary
The Earth's pole, the point where the Earth's rotational axis intersects its crust in the Northern Hemisphere, drifted in a new eastward direction in the 1990s, as observed by space geodetic observations. Generally, polar motion is caused by changes in the hydrosphere, atmosphere, oceans, or solid Earth. However, short-term observational records of key information in the hydrosphere (i.e., changes in terrestrial water storage) limit a better understanding of new polar drift in the 1990s. This study introduces a novel approach to quantify the contribution from changes in terrestrial water storage by comparing its drift path under two different scenarios. One scenario assumes that the terrestrial water storage change throughout the entire study period (1981–2020) is similar to that observed recently (2002–2020). The second scenario assumes that it changed from observed glacier ice melting. Only the latter scenario, along with the atmosphere, oceans, and solid Earth, agrees with the polar motion during the period of 1981–2020. The accelerated terrestrial water storage decline resulting from glacial ice melting is thus the main driver of the rapid polar drift toward the east after the 1990s. This new finding indicates that a close relationship existed between polar motion and climate change in the past.
Climate Impacts of COVID‐19 Induced Emission Changes
- Geophysical Research Letters
-  29 December 2020
Key Points
-
COVID-19 induced lockdowns significantly altered emissions of aerosols, leading to simulated changes in cloud properties in two Earth System Models
-
Aerosol Cloud Interactions from reduced emissions result in significant increases in radiative forcing, up to +0.29 ± 0.15 Wm−2
-
Aerosol radiative forcing reductions are the largest contributor to surface temperature changes
Plain Language Summary
The COVID-19 pandemic changed emissions of gases and particulates. These gases and particulates affect climate. In general, human emissions of particles cool the planet by scattering away sunlight in the clear sky and by making clouds brighter to reflect sunlight away from the earth. This paper focuses on understanding how changes to emissions of particulates (aerosols) affect climate. We use estimates of emissions changes for 2020 in two climate models to simulate the impacts of the COVID-19 induced emission changes. We tightly constrain the models by forcing the winds to match observed winds for 2020. COVID-19 induced lockdowns led to reductions in aerosol and precursor emissions, chiefly soot or black carbon and sulfate (SO4). This is found to reduce the human caused aerosol cooling: creating a small net warming effect on the earth in spring 2020. Changes in cloud properties are smaller than observed changes during 2020. The impact of these changes on regional land surface temperature is small (maximum +0.3 K). The impact of aerosol changes on global surface temperature is very small and lasts over several years. However, the aerosol changes are the largest contribution to COVID-19 affected emissions induced radiative forcing and temperature changes, larger than ozone, CO2 and contrail effects.
A high‐accuracy map of global terrain elevations
- Geophysical Research Letters
-  5844-5853
-  31 May 2017
Key Points
- A high-accuracy global digital elevation model (DEM) was developed by removing multiple height error components from existing DEMs
- Landscape representation was improved, especially in flat regions where height error magnitude was larger than actual topography variation
- The improved-terrain DEM is helpful for any geoscience applications which are terrain dependent, such as flood inundation modelling
Plain Language Summary
Terrain elevation maps are fundamental input data for many geoscience studies. While very precise Digital Elevation Models (DEMs) based on airborne measurements are available in developed regions of the world, most areas of the globe rely on spaceborne DEMs which still include non-negligible height errors for geoscience applications. Here we developed a new high accuracy map of global terrain elevations at 3" resolution (~90m at the equator) by eliminating multiple error components from existing spaceborne DEMs. The height errors included in the original DEMs were separated from actual topography signals and removed using a combination of multiple satellite datasets and filtering techniques. After error removal, global land areas mapped with ±2m or better accuracy increased from 39% to 58%. Significant improvements were found, especially in flat regions such as river floodplains. Here detected height errors were larger than actual topography variability, and following error removal landscapes features such as river networks and hill-valley structures at last became clearly represented. The developed high accuracy topography map will expand the possibility of geoscience applications that require high accuracy elevation data such as terrain landscape analysis, flood inundation modelling, soil erosion analysis, and wetland carbon cycle studies.
Source location of the 26 sec microseism from cross‐correlations of ambient seismic noise
- Geophysical Research Letters
-  26 September 2006
Diurnal temperature range as an index of global climate change during the twentieth century
- Geophysical Research Letters
-  13 July 2004
Causes of Higher Climate Sensitivity in CMIP6 Models
- Geophysical Research Letters
-  3 January 2020
Key Points
- Climate sensitivity is larger on average in CMIP6 than in CMIP5 due mostly to a stronger positive low cloud feedback
- This is due to greater reductions in low cloud cover and weaker increases in low cloud water content, primarily in the extratropics
- These changes are related to model physics differences that are apparent in unforced climate variability
Plain Language Summary
The severity of climate change is closely related to how much the Earth warms in response to greenhouse gas increases. Here we find that the temperature response to an abrupt quadrupling of atmospheric carbon dioxide has increased substantially in the latest generation of global climate models. This is primarily because low cloud water content and coverage decrease more strongly with global warming, causing enhanced planetary absorption of sunlight—an amplifying feedback that ultimately results in more warming. Differences in the physical representation of clouds in models drive this enhanced sensitivity relative to the previous generation of models. It is crucial to establish whether the latest models, which presumably represent the climate system better than their predecessors, are also providing a more realistic picture of future climate warming.
Radiative forcing of carbon dioxide, methane, and nitrous oxide: A significant revision of the methane radiative forcing
- Geophysical Research Letters
-  12,614-12,623
-  27 December 2016
Key Points
- Calculated CH4 radiative forcing is about 25% higher than earlier estimates
- New simplified expressions for forcing are presented for CO2, N2O, and CH4
- Forcing for high CO2 concentrations is 9% higher than previous expressions
Plain Language Summary
“Radiative forcing” is an important method to assess the importance of different climate change mechanisms, and is used, for example, by the Intergovernmental Panel on Climate Change (IPCC). Increased concentrations of greenhouse gases, such as carbon dioxide, methane and nitrous oxide, are the major component of the human activity that led the IPCC, in its 2013 Assessment, to conclude that “it is extremely likely that human influence is the dominant cause of warming since the mid-20th century.” In this letter, we report new and detailed calculations that aimed to update the simpler methods of computing the radiative forcing that have been used in IPCC assessments, and elsewhere. The major result is that radiative forcing due to methane is around 20-25% higher than that found using the previous simpler methods. The main reason for this is the inclusion of the absorption of solar radiation by methane, a mechanism that had not been included in earlier calculations. We examine the mechanisms by which this solar absorption causes this radiative forcing.The work has significance for assessments of the climate impacts of methane emissions due to human activity, and for the way methane is included in international climate agreements.
Arctic Sea Ice in CMIP6
- Geophysical Research Letters
-  17 April 2020
Key Points
- CMIP6 model simulations of Arctic sea-ice area capture the observational record in the multimodel ensemble spread
- The sensitivity of Arctic sea ice to changes in the forcing is better captured by CMIP6 models than by CMIP5 and CMIP3 models
- The majority of available CMIP6 simulations lose most September sea ice for the first time before 2050 in all scenarios
Plain Language Summary
We examine simulations of Arctic sea ice from the latest generation of global climate models. We find that the observed evolution of Arctic sea-ice area lies within the spread of model simulations. In particular, the latest generation of models performs better than models from previous generations at simulating the sea-ice loss for a given amount of CO2 emissions and for a given amount of global warming. In most simulations, the Arctic Ocean becomes practically sea-ice free (sea-ice area <1 million km2) in September for the first time before the Year 2050.
Changing Lengths of the Four Seasons by Global Warming
- Geophysical Research Letters
-  19 February 2021
Key Points
-
Climate change has driven longer and hotter summers, shorter and warmer winters, shorter springs and autumns
-
The onsets of spring and summer are advanced, while the onsets of autumn and winter are delayed
-
Such changes in four seasons can be mainly attributed to greenhouse-warming, and will be amplified under the business-as-usual scenario
Plain Language Summary
A series of phenomena such as early flowering of plants and early migratory birds are suggesting that the traditional four seasons may have changed. We focus on how the four seasons changed during 1952–2011 and will change by the end of this century in the warming Northern Hemisphere midlatitudes. We find that lengths and start dates of the four seasons have changed, and the changes will be amplified in the future. Over the period of 1952–2011, the length of summer increased from 78 to 95 days and that of spring, autumn and winter decreased from 124 to 115, 87 to 82, and 76 to 73 days, respectively. In addition, summer is projected to last nearly half a year, but winter less than 2 months by 2100. Such changes can trigger a chain of reactions in agriculture, policy-making for agricultural management and disaster prevention requires adjustment accordingly. The seasonal-related topics involving ecology, the ocean and the atmosphere also need to be revisited.