Browse Articles
Atmospheric Circulation Patterns Conducive to Severe Haze in Eastern China Have Shifted Under Climate Change
-  29 November 2021
Key Points
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Atmospheric circulation anomalies associated with the most severe haze pollution are identified
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Haze formation in eastern China has shifted from causes of local accumulation in northern China to regional transport in southern China
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Climate change under the sustainable and intermediate development scenarios are the ideal paths to reduce haze in China
Helheim Glacier Poised for Dramatic Retreat
-  24 November 2021
Key Points
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Helheim Glacier is more retreated and the near-terminus region is up to 100 m thinner than during its much-reported dramatic retreat in 2005
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Helheim, one of Greenland's largest ice dischargers, is now more vulnerable than at any point since the Little Ice Age
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Helheim's new configuration offers potential for sustained dynamic instability and a major contribution to global sea-level rise
Titan's Global Radiant Energy Budget During the Cassini Epoch (2004–2017)
-  24 November 2021
Key Points
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With Cassini multiinstrument observations (CIRS, ISS, and VMIS), we provide measurements of the seasonal variations of Titan's Bond albedo
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Our measurements suggest a net energy excess (2.9 ± 0.8% of the emitted energy) over the Cassini era (2004–2017) on Titan
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The energy imbalance changes from an energy excess (10.7 ± 0.7%) in 2004–2005 to an energy deficit (−3.4 ± 0.6%) in 2017
Multi‐MeV Electron Dynamics Near the Inner Edge of the Outer Radiation Belt
-  24 November 2021
Key Points
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Multiple orders of magnitude dynamics of multi-MeV electron flux and phase space density are shown near the inner edge of the outer belt
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These dynamics, and their timescales, appear to be energy-dependent, with variations on the timescales of hours to one week within L ⪅ 3
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Quiet-time formation of a local peak at L ≈ 3 of ⪆6 MeV electron phase space density and its rapid decay during storms are shown
California's Volatile Hydroclimate: Lessons From the Paleoclimate Record
-  24 November 2021
Key Points
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Paleoclimate data provides key constraints on natural hydroclimate variability, but quantitative records are rare
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Speleothem calcium isotopes are a useful new proxy with potential for quantitative precipitation reconstructions
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Early Holocene precipitation variability in California met or exceeded that observed in the instrumental record
A Novel Experimental Study on Density‐Driven Instability and Convective Dissolution in Porous Media
-  24 November 2021
Key Points
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Empirical linear correlation between reflected visible light intensity and in situ solute concentration
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Experimental determination of the critical Rayleigh-Darcy number for the onset of density-driven instability
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Experimental determination of the critical time scales for the onset of density-driven instability and convective dissolution
Tropical Pacific Forcing of Hydroclimate in the Source Area of the Yellow River
-  24 November 2021
Key Points
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Proxy-based hydroclimate reconstruction in the source area of the Yellow River over the past ∼2000 years from Ngoring Lake sediments
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Ngoring Lake sediments document a long-term drying in the source area of the Yellow River, coherent with the records from north China
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Wetness conditions in the source area of the Yellow River are linked to tropical Pacific zonal sea surface temperature gradients
Multispacecraft Observation of the Presubstorm Long‐Lasting Poloidal ULF Wave
-  24 November 2021
Key Points
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The ultralow frequency wave was detected on the dayside 30 min before the substorm onset and lasted for 15 hr
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Substorm injections did not affect the wave structure
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The energy was transferred from 100 keV protons to the poloidal Alfven wave via the gradient instability
A Dusty Atmospheric River Brings Floods to the Middle East
-  1 December 2021
Key Points
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Atmospheric rivers can cause heavy rains, rapid snowmelt, and floods in regions far from the oceans such as the Middle East
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A distinct characteristic of ARs in the Middle East is their contribution to dust transport from the major sources along their pathways
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Based on its intensity and duration, the AR in this study is classified as “balance of beneficial and hazardous”
Atmospheric Rivers Bring More Frequent and Intense Extreme Rainfall Events over East Asia under Global Warming
-  1 December 2021
Key Points
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Atmospheric rivers bring extreme rainfall over East Asia in current and future climates
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Atmospheric rivers are responsible for a large fraction of the increase in extreme rainfall over East Asia under global warming
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Intensified water vapor transports by atmospheric rivers cause record-breaking extreme rainfall events in a warmer climate
Airborne Electromagnetic Signatures of an Ancient River in the Water‐Stressed Ganga Plain, Prayagraj, India: A Potential Groundwater Repository
-  1 December 2021
Key Points
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A comprehensive 3D map of aquifer system of the Ganga-Yamuna doab, India
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Discovery of a 45 km long buried river with dimensions comparable to those of Ganga and Yamuna rivers, near Prayagraj, India
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These findings offer a new possibility for management of the dwindling groundwater in the Ganga-Yamuna doab
Warm phase of AMV damps ENSO through weakened thermocline feedback
-  1 December 2021
Key Points
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AMV weakens ENSO sea surface temperature anomalies by 10% and local ENSO precipitation anomalies by up to 45%
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The thermocline feedback in the tropical Pacific is weakened in boreal autumn, reducing ENSO growth rate
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AMV causes changes in the Pacific mean state that lead to wind stress anomalies being more confined in the west Pacific during ENSO onset
Origin of frequency‐doubling and shoulder‐like magnetic pulsations in ULF waves
-  1 December 2021
Key Points
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Frequency doubling and shoulder-like pulsations are observed in compressional and azimuthal magnetic fields, respectively, of Pc5 waves
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Both features are simultaneously reproduced by a model of north/south flux tube oscillations in a ballooning-mirror structure
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In this model, spacecraft off the equator would observe more complicated features due to the coexistence of multiple harmonic variations
Multiple strokes along the same channel to ground in positive lightning produced by a supercell
-  1 December 2021
Key points
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54 of 84 multiple-stroke +CG flashes produced by a supercell in Argentina had subsequent strokes following pre-existing channels to ground
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Speeds of descending positive leaders that traverse a channel created by a previous positive stroke are reported for the first time
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Subsequent leaders in positive lightning initiated in the same way as counterparts in negative lightning
Subduction Polarity Reversal Triggered by Oceanic Plateau Accretion: Implications for Induced Subduction Initiation
-  29 November 2021
Key Points
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Subduction polarity reversal during oceanic plateau accretion is numerically studied
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Buoyant and thick oceanic plateau favors subduction polarity reversal
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Extension is not a unique phenomenon in spontaneous subduction initiation
Responses of biogenic sulfur compounds concentrations to dust aerosol enrichment and ocean acidification in the western Pacific Ocean
-  29 November 2021
Key Points
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The concentrations of biogenic sulfur compounds (BSCs) in response to dust aerosol deposition and ocean acidification were examined
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The dust aerosol additions elevated the relative abundance of strong DMSP and DMSO producers
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The mean concentrations of the three sulfur compounds increased in the acidified treatments
Conjugate photoelectron energy spectra derived from coincident FUV and radio measurements
-  29 November 2021
Key Points
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Nightglow emissions excited by photoelectrons originating in the magnetically conjugate hemisphere are observed by the ICON mission
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Conjugate photoelectron energy spectra are derived for the first time using global scale far-ultraviolet and radio-occultation observations
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Comparison of estimated photoelectron fluxes with measurements on a rocket flight shows consistent characteristics at all altitudes
Stratospheric temperature and ozone anomalies associated with the 2020 Australian New Year Fires
-  29 November 2021
Key Points
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Stratospheric aerosol levels were elevated to record levels over the entire Southern hemisphere for months following the Australian fires
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The fires caused warming uncorrelated between low latitudes versus extra-tropics, as in the volcanic eruptions of Pinatubo and El Chichon
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Ozone reduction was observed in midlatitude and polar regions, similar in magnitude to that following the Calbuco volcanic eruption in 2015
The Arctic oscillation signature in the wintertime geopotential height and temperature fields
- Geophysical Research Letters
-  1297-1300
-  1 May 1998
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 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 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
A generalized approach to parameterizing convection combining ensemble and data assimilation techniques
- Geophysical Research Letters
-  38-1-38-4
-  25 July 2002
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
The Global Fingerprint of Modern Ice‐Mass Loss on 3‐D Crustal Motion
- Geophysical Research Letters
-  16 August 2021
Key Points
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Early 21st century ice-mass loss generates a global pattern of 3-D crustal motion
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Deformation driven by melting of Greenland Ice Sheet and Arctic glaciers extends across the Northern Hemisphere
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Far-field motions are several tenths of a millimeter per year, with horizontal rates often exceeding vertical rates
Plain Language Summary
As ice sheets and glaciers melt and water is redistributed to the global oceans, the Earth's crust deforms, generating a complex pattern of 3-D motions at Earth's surface. In this study, we use satellite-derived constraints on early 21st century ice-mass balance of the Greenland and Antarctic Ice Sheets and a global database of mountain glaciers and ice caps, to predict how the crust has deformed over the last two decades. We show that, rather than only being localized to regions of ice loss, melting of the Greenland Ice Sheet and Arctic glaciers has caused significant horizontal and vertical deformation of the crust that extends over much of the Northern Hemisphere. This 3-D surface motion is on average several tenths of a millimeter per year, and it varies significantly year-to-year. We conclude that future work analyzing measurements of crustal motion (across various fields in Earth science) should correct for the deformation associated with modern ice-mass loss at sites distant from melting ice.
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.
Polar Drift in the 1990s Explained by Terrestrial Water Storage Changes
- Geophysical Research Letters
-  22 March 2021
Key Points
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Past climate-driven polar motion was quantified by modeling terrestrial water storage under two different scenarios
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One scenario was based on GRACE and reanalysis data; another scenario was based on extra glacier change observations
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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
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COVID-19 induced lockdowns significantly altered emissions of aerosols, leading to simulated changes in cloud properties in two Earth System Models
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Aerosol Cloud Interactions from reduced emissions result in significant increases in radiative forcing, up to +0.29 ± 0.15 Wm−2
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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.
BedMachine v3: Complete Bed Topography and Ocean Bathymetry Mapping of Greenland From Multibeam Echo Sounding Combined With Mass Conservation
- Geophysical Research Letters
-  11,051-11,061
-  18 September 2017
Key Points
- We present a comprehensive, seamless bed topography across the ice-ocean margin around Greenland
- Two to 4 times more glaciers have calving fronts grounded below 200 m compared to previous mappings
- Total ice volume of Greenland is 2.99 ± 0.02 times 106 km3, yielding a potential sea level rise of 7.42 m, 7 cm greater than previous estimates
Californian Wildfire Smoke Over Europe: A First Example of the Aerosol Observing Capabilities of Aeolus Compared to Ground‐Based Lidar
- Geophysical Research Letters
-  15 March 2021
Key Points
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Smoke from the extraordinary 2020 Californian wild fires traveled within 3–4 days toward Europe
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Highest Aerosol Optical Thickness ever measured in the free troposphere over Leipzig, Germany, Central Europe, with ground-based lidar
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Unique opportunity for a first assessment of the aerosol optical profiles of the spaceborne wind lidar mission Aeolus
Plain Language Summary
In September 2020, extremely strong wildfires in the western USA (i.e., mainly in California) produced large amounts of smoke. These biomass burning aerosol (BBA) layers were transported from the US west coast towards central Europe within 3-4 days. This smoke plume was observed above Leipzig, Germany, for several days turning the sky milky and receiving high media attention - it was the highest perturbation of the troposphere in terms of AOT ever observed over Leipzig. The first smoke plume arrived on 11 September 2020, just in time for a regular overpass of the Aeolus satellite of the European Space Agency (ESA). Aeolus accommodates the first instrument in space that actively measures profiles of a horizontal wind component in the troposphere and lower stratosphere. Aeolus has been launched to improve weather forecasts while assimilating the Aeolus wind profile data in near–real time. But Aeolus also delivers profiles of aerosol and cloud optical properties as spin-off products. We performed a first assessment of the aerosol profiling capabilities of Aeolus while precisely analyzing the smoke plume above Leipzig with a ground-based multiwavelength-Raman-polarization lidar. But we also show the dramatic impact of fires in the western USA on atmospheric conditions over central Europe.
Tropical Atlantic surface current variability from 10 years of TOPEX/Poséïdon altimetry
- Geophysical Research Letters
-  12 February 2004
The 2020 Eruption and Large Lateral Dike Emplacement at Taal Volcano, Philippines: Insights From Satellite Radar Data
- Geophysical Research Letters
-  22 March 2021
Key Points
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We present a comprehensive interferometric synthetic aperture radar (InSAR)-based data, analyses, and models of Taal’s pre- to post-eruptive state
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During the eruptive crisis, Taal’s magma reservoir lost 0.531 ± 0.004 km3 of volume while a 0.643 ± 0.001 km3 lateral dike was emplaced
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Low-latency InSAR-derived products provided crucial and significant information to PHIVOLCS during the January 2020 eruptive event
Plain Language Summary
Taal volcano in the Philippines erupted on January 12, 2020. Here, we present the pre-, co-, and post-eruption data, model, and analyses using interferometric synthetic aperture radar (InSAR) data acquired by various satellite systems. We find that: (1) prior to the eruption, the volcano experiences a sequence of long-term (>1 year) deflation followed by short-term (≤1 year) inflation as a result of the depressurization-pressurization of its ∼5 km depth magma reservoir; (2) during the eruption, the magma reservoir lost a volume of 0.531 ± 0.004 km3 while a 0.643 ± 0.001 km3 lateral dike was emplaced; and (3) post-eruption analyses reveal that the magma reservoir is in recovery starting ∼3 weeks after the main eruptive phase. We propose a conceptual analysis to explain the 2020 Taal eruption and the dike emplacement. We also report the unique and significant contribution of remote sensing data, particularly InSAR during the peak of the crisis.
Satellite and Ocean Data Reveal Marked Increase in Earth’s Heating Rate
- Geophysical Research Letters
-  15 June 2021
Key Points
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Satellite and in situ observations independently show an approximate doubling of Earth's Energy Imbalance (EEI) from mid-2005 to mid-2019
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Anthropogenic forcing, internal variability, and climate feedbacks all contribute to the positive trend in EEI
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Marked decreases in clouds and sea-ice and increases in trace gases and water vapor combine to increase the rate of planetary heat uptake
Plain Language Summary
Climate is determined by how much of the sun's energy the Earth absorbs and how much energy Earth sheds through emission of thermal infrared radiation. Their sum determines whether Earth heats up or cools down. Continued increases in concentrations of well-mixed greenhouse gasses in the atmosphere and the long time-scales time required for the ocean, cryosphere, and land to come to thermal equilibrium with those increases result in a net gain of energy, hence warming, on Earth. Most of this excess energy (about 90%) warms the ocean, with the remainder heating the land, melting snow and ice, and warming the atmosphere. Here we compare satellite observations of the net radiant energy absorbed by Earth with a global array of measurements used to determine heating within the ocean, land and atmosphere, and melting of snow and ice. We show that these two independent approaches yield a decadal increase in the rate of energy uptake by Earth from mid-2005 through mid-2019, which we attribute to decreased reflection of energy back into space by clouds and sea-ice and increases in well-mixed greenhouse gases and water vapor.
Quasi‐Stationary Intense Rainstorms Spread Across Europe Under Climate Change
- Geophysical Research Letters
-  30 June 2021
Key Points
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Following an ingredients-based method, future changes in intense rainstorms in Europe are studied using convection-permitting simulations
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Environments favoring high rainfall rates are projected to be 7× more frequent by 2100, while the figure for quasi-stationary ones is 11×
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Reduction in storm speeds due to weaker jets, possibly via Arctic Amplification, can enhance accumulations further increasing flood risk
Plain Language Summary
Intense rainstorms are expected to be more frequent due to global warming, because warmer air can hold more moisture. Here, using very detailed climate simulations (with a 2.2 km grid), we show that the storms producing intense rain across Europe might move slower with climate change, increasing the duration of local exposure to these extremes. Our results suggest such slow-moving storms may be 14× more frequent across land by the end of the century. Currently, almost-stationary intense rainstorms are uncommon in Europe and happen rarely over parts of the Mediterranean Sea, but in future are expected to occur across the continent, including in the north. The main reason seems to be a reduced temperature difference between the poles and tropics, which weakens upper-level winds in the autumn, when these short-duration rainfall extremes most occur. This slower storm movement acts to increase rainfall amounts accumulated locally, enhancing the risk of flash floods across Europe beyond what was previously expected.