AGU期刊一周Research Spotlight (April 28~ May 04, 2017)

发布时间:2017-5-5 10:15:20 点击次数:421

I. Science Policy

1. A Framework for Decisions on Science and Policy

Human reasoning has helped us become one of the most successful species to populate the planet, but we still struggle with cognitive biases.

2. Trump’s Early Actions Target Science, Environment

Although the administration declares “historic accomplishments” during its first 100 days, a look back at Earth and space science impacts sees funding threats, rollbacks, and controversial appointees.

II. Ocean Sciences

1. Packing Science into a Shipping Vessel

Oleander Workshop II: 25 Years of Operations; Narragansett, Rhode Island, 26–27 October 2016

III. Hazards & Disasters

1. Understanding Kamchatka’s Extraordinary Volcano Cluster

An international seismological collaboration in Kamchatka, Russia, investigates the driving forces of one of the world’s largest, most active volcano clusters.

2. Reducing Uncertainty in Hazard Prediction

The editors of a new book describe how to characterize uncertainty in natural hazards, the incorporation of uncertainty into modeling, its contribution to better decision-making, and research needs.

IV. Climate Change

1. More Intense Rains in U.S. Midwest Tied to Farm Mechanization

Replacement of horses by machines since the 1940s allowed central U.S. farmers to change the crops they planted, which may have altered regional climate.

2. Climate Change’s Pulse Is in Central America and the Caribbean

Nations that border the Gulf of Mexico and Caribbean Sea are ideally placed for tracking the effects of global climate change and testing innovative ways to adapt to future changes.

3. Iceberg Surge During Last Deglaciation May Have Had Two Pulses

Seafloor sediment cores provide new clues that could help clarify the influence of ice sheet collapse on a period of ocean cooling marked by slowed deepwater circulation.

VI. Geophysical Research Letters

1. Climate impacts of the Atlantic Multidecadal Oscillation simulated in the CMIP5 models: A re-evaluation based on a revised index

The Atlantic Multidecadal Oscillation (AMO) has pronounced influences on weather and climate across the globe. This study provides a direct comparison of the observed AMO-related surface temperature and precipitation anomalies to those simulated in the Coupled Model Intercomparison Project Phase 5 (CMIP5) models. It is found that the model-simulated AMO-related features are obscured by the global signal in some key regions if the North Atlantic sea surface temperature (SST) itself is used to represent the AMO as in previous studies. After the global mean SST is removed from the North Atlantic SST, the CMIP5 models show substantially better agreement with the observations in terms of the AMO-related worldwide impacts, such as the Pacific SST and the rainfall over the United States and India. These results suggest the removal of the global signal or signals originating in other ocean basins is a necessary procedure to uncover the AMO features in climate model simulations.

2. Venus's winds and temperatures during the MESSENGER's flyby: An approximation to a three-dimensional instantaneous state of the atmosphere

Even though many missions have explored the Venus atmospheric circulation, its instantaneous state is poorly characterized. In situ measurements vertically sampling the atmosphere exist for limited locations and dates, while remote sensing observations provide only global averages of winds at altitudes of the clouds: 47, 60, and 70 km. We present a three-dimensional global view of Venus's atmospheric circulation from data obtained in June 2007 by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) and Venus Express spacecrafts, together with ground-based observations. Winds and temperatures were measured for heights 47–110 km from multiwavelength images and spectra covering 40°N–80°S and local times 12 h–21 h. Dayside westward winds exhibit day-to-day changes, with maximum speeds ranging 97–143 m/s and peaking at variable altitudes within 75–90 km, while on the nightside these peak below cloud tops at ~60 km. Our results support past reports of strong variability of the westward zonal superrotation in the transition region, and good agreement is found above the clouds with results from the Laboratoire de Météorologie Dynamique (LMD) Venus general circulation model.

3. Bed elevation of Jakobshavn Isbræ, West Greenland, from high-resolution airborne gravity and other data

Jakobshavn Isbræ, West Greenland, which holds a 0.6 m sea level volume equivalent, has been speeding up and retreating since the late 1990s. Interpretation of its retreat has been hindered by difficulties in measuring its ice thickness with airborne radar depth sounders. Here we employ high-resolution, helicopter-borne gravity data from 2012 to reconstruct its bed elevation within 50 km of the ocean margin using a three-dimensional inversion constrained by fjord bathymetry data offshore and a mass conservation algorithm inland. We find the glacier trough to be asymmetric and several 100 m deeper than estimated previously in the lower part. From 1996 to 2016, the grounding line migrated at 0.6 km/yr from 700 m to 1100 m depth. Upstream, the bed drops to 1600 m over 10 km then slowly climbs to 1200 m depth in 40 km. Jakobshavn Isbræ will continue to retreat along a retrograde slope for decades to come.

4. Population and energy elasticity of tornado casualties

Tornadoes are capable of catastrophic destruction and mass casualties, but there are yet no estimates of how sensitive the number of casualties are to changes in the number of people in harm's way or to changes in tornado energy. Here the relationship between tornado casualties (deaths and injuries), population, and energy dissipation is quantified using the economic concept of “elasticity.” Records of casualties from individual tornadoes over the period 2007–2015 are fit to a regression model. The coefficient on the population term (population elasticity) indicates that a doubling in population increases the casualty rate by 21% [(17, 24)%, 95% credible interval]. The coefficient on the energy term (energy elasticity) indicates that a doubling in energy dissipation leads to a 33% [(30, 35)%, 95% credible interval] increase in the casualty rate. The difference in elasticity values show that on average, changes in energy dissipation have been relatively more important in explaining tornado casualties than changes in population. Assuming no changes in warning effectiveness or mitigation efforts, these elasticity estimates can be used to project changes in casualties given the known population trends and possible trends in tornado activity.

5. Subsynoptic-scale features associated with extreme surface gusts in UK extratropical cyclone events

Numerous studies have addressed the mesoscale features within extratropical cyclones (ETCs) that are responsible for the most destructive winds, though few have utilized surface observation data, and most are based on case studies. By using a 39-station UK surface observation network, coupled with in-depth analysis of the causes of extreme gusts during the period 2008–2014, we show that larger-scale features (warm and cold conveyer belts) are most commonly associated with the top 1% of UK gusts but smaller-scale features generate the most extreme winds. The cold conveyor belt is far more destructive when joining the momentum of the ETC, rather than earlier in its trajectory, ahead of the approaching warm front. Sting jets and convective lines account for two thirds of severe surface gusts in the UK.

6. Spiral gravity waves radiating from tropical cyclones

Internal gravity waves are continuously generated by deep moist convection around the globe. Satellite images suggest that tropical cyclones produce short-wavelength, high-frequency waves that radiate outward, with the wave fronts wrapped into tight spirals by the large differential advection of the sheared tangential flow. This letter presents new in situ observations of such waves from two sources: flight level data from research aircraft that show radial wavelengths of 2–10 km and vertical velocity magnitudes from 0.1 to 1.0 ms−1 and surface observations from a research buoy in the Pacific that indicate the passage of gravity waves overhead as tropical cyclones pass by at distances of 100 to 300 km. Numerical simulations are used to interpret these observations and to understand the broader horizontal and vertical structures of the radiating waves. The simulations suggest a correlation between wave amplitude and cyclone intensity, which could be used to make remote estimates of peak wind speeds.

7. Competition between outer zone electron scattering by plasmaspheric hiss and magnetosonic waves

We quantify the electron scattering effects of simultaneous plasmaspheric hiss and magnetosonic waves that occurred in two neighboring time intervals but with distinct wave intensity profiles on 21 August 2013. Their combined scattering is found capable of causing electron distribution variations largely distinguishable from the consequences of individual waves. The net effect of electron diffusion relies strongly on the relative dominance of the two wave intensities, which also controls the relative contribution of each wave mode. In combination, MS waves slow down the hiss-induced loss of ~100 keV electrons, and hiss efficiently inhibits the electron butterfly distribution caused by MS waves to produce a gradual acceleration process. Our results strongly suggest that comprehensive simulations of the radiation belt electron dynamics should carefully incorporate the combined scattering and complex competition resulting from simultaneous occurrences of various magnetospheric emissions, including, but not limited to, plamaspheric hiss and magnetosonic waves.

VII. AGU Blogs

1. Study of historic Chilean quake warns of a future tsunami

The most populated central region of Chile could be vulnerable to large tsunamis generated by a deceptively moderate kind of earthquake that might be overdue, say scientists who have sorted out the source of an earthquake and tsunami that struck the area 287 years ago. The region is the same that trembled from a magnitude 6.9 earthquake on April 24.

2. Glass formed by volcanic lightning could be used to study eruptions

Researchers have developed a method to measure one of the most striking and difficult to measure volcanic features – volcanic lightning – using the tiny glass spheres formed by hot volcanic ash.

3. Smart People Listen to Those Who Dwell in Facts, Even When They Are Uncomfortable!

I was invited to a seminar at NASA Goddard last week which combined some top climate experts with meteorologists who work in media. We shared ideas on how to better communicate science, but the highlight was an update from some top NASA and NOAA climate experts. Dr Ben Santer went over the satellite temperature record, (and in the process destroyed some of the lingering myths that keep being repeated), and …

4. Accretionary lapilli from Archean volcanic eruptions

When a volcano erupts ash into the atmosphere, static charges in the eruptive plume can sometimes producespectacular displays of lightning. Those same electrostatic charges, coupled with the presence of water vapor, can encourage the ash to clump together in small concentrically-layered orbs called accretionary lapilli. The individual lapillus grows by adding layers of new ash on its exterior. A hailstone forms through a similar process, though made of ice. Both hailstones and lapilli have a concentrically-zoned structure.

Here is a suite of accretionary lapilli images from the Msauli Chert, exposed in the Barberton Greenstone Belt, South Africa, a kilometer or so from the Swaziland border.



WASHINGTON, DC – Discover the latest in Earth and space science research at the JpGU-AGU Joint Meeting 2017 taking place 20-25 May at the Makuhari Messe International Conference Hall in Chiba, Japan. The meeting will bring together researchers from theAmerican Geophysical Union and the Japan Geoscience Union.