AGU期刊一周Research Spotlight
AGU期刊一周Research Spotlight (Jun 22~Jun 28, 2018)
时间:2018年06月28日 17:35来源: 点击数:

I. Climate Change

1.New Version of Popular Climate Model Released

After spending months addressing a big glitch, researchers released the second version of the Community Earth System Model.


II.Hydrology, Cryosphere & Earth Surface

1.Coldest Place on Earth Is Colder than Scientists Thought

Tiny valleys near the top of Antarctica’s ice sheet reach temperatures of nearly minus 100 degrees Celsius (minus 148 degrees Fahrenheit) in the winter, a new study finds. The results could change scientists’ understanding of just how low temperatures can get at Earth’s surface, according to the researchers.


2.Exploring a More Dynamic Arctic Icescape

A joint special issue presents new findings from a field campaign in the Arctic Ocean which highlights key processes that need to be taken into account to predict the future of the Arctic ice pack.


III. Education

1.If Disney Princesses Were Earth and Environmental Scientists

Welcome to an alternate universe where happily ever after includes a dedication to the scientific method.


IV. Planetary Sciences

1.The Case of the Missing Lunar Heat Flow Data Is Finally Solved

Decades-old data analyzed for the first time suggest that astronauts’ disturbance of the Moon surface increased solar heat intake, warming the ground below.


V. Biogeosciences

1.Refining Remote Sensing of Dissolved Organic Carbon in Waterways

A pond full of decaying oak leaves soon turns as brown as tea. Eventually, much of that rotting organic matter is released into the atmosphere as carbon dioxide. Now, a new study could improve scientists’ ability to track such emissions by improving how satellites detect dissolved organic carbon (DOC) in freshwater.


VI. Geophysical Research Letters

1.Numerical modeling of the concentric gravity wave seeding of low‐latitude nighttime medium‐scale traveling ionospheric disturbances

The first‐principles three‐dimensional ionosphere model Naval Research Laboratory SAMI3/ESF is used to study the low‐latitude nighttime medium‐scale traveling ionospheric disturbances (MSTIDs) triggered by the typhoon‐induced concentric gravity waves (CGWs) for the first time. Simulation results demonstrate that the electrodynamic coupling between CGWs and Perkins instability can initiate the rarely observed low‐latitude nighttime MSTIDs by accelerating their growth rates. Both the simulations and observations show the westward and westward/equatorward propagating CGWs with similar wavefront alignments to the Perkins instability could enhance the generation of MSTIDs rather than the northward propagating CGWs. The CGWs penetrating to the ionospheric F layer without severe dissipation can induce greater polarization electric fields to accelerate the Perkins instability via E×B drifts.


2.A comparison of model‐based ionospheric and ocean tidal magnetic signals with observatory data

Observed tidal geomagnetic field variations are due to a combination of electric currents in the ionosphere, ocean, and their induced counterparts. Using these variations to constrain subsurface electrical conductivity in oceanic regions is a promising frontier; however, properly separating the ionospheric and oceanic tidal contributions of the magnetic field is critical for this. We compare semi‐diurnal lunar tidal magnetic signals (i.e. the signals due to the M2 tidal mode) estimated from 64 global observatories to physics‐based forward models of the ionospheric M2 magnetic field and the oceanic M2magnetic field. At ground level, predicted ionospheric M2 amplitudes are strongest in the horizontal components, whereas the predicted oceanic amplitudes are strongest in the vertical direction. There is good agreement between the predicted and estimated M2phases for the Y component, however the F and X components experience deviations that may be indicative of unmodeled ionospheric processes or unmodeled coastal effects. Overall, we find that the agreement between the physics‐based model predictions and the observations is very encouraging for electromagnetic sensing applications, especially since the predicted ionospheric vertical component is very weak.


3.Observation of Oblique Lower Band Chorus Generated by Nonlinear Three‐Wave Interaction

Oblique whistler mode waves have been suggested to play an important role in radiation belt electron dynamics. Recently, Fu et al. [2017] proposed that highly oblique lower band whistler waves could be generated by nonlinear three‐wave resonance. Here we present the first observational evidence of such process, using Van Allen Probes data, where an oblique lower band chorus wave is generated by two quasi‐parallel waves through nonlinear three‐wave interaction. The wave resonance condition is satisfied even in the presence of frequency chirping of one of the pump waves. Different from the simulation results of Fu et al. [2017], simultaneous particle data do not show a plateau in the electron distribution, which could be due to the very weak intensity of the generated waves. These results should help to better understand the generation of oblique waves in the inner magnetosphere and their relative roles in energetic electron dynamics.


VII. AGU Blogs

1.Deformed conglomerate of Frog Lakes, California

I’ve been lucky to spend the past week+ in California with friends, including geoscience outreach wonder duo Ryan and LauraHollister. We spent an enjoyable 4 days on the east side of the Sierra Nevada, attending field trips through the Mono Basin Bird Chautauqua alternating with excursions to entertain our collective posse of four kids. One day, we took the kids up to Virginia Lakes to go fishing, and Laura and I were able to get in some geologizing. We hiked up to the Frog Lakes, where there is a beautiful deformed conglomerate exposed.


2.Honeycomb Glacier Retreat, Washington New Lake Lost Nunatak

Honeycomb Glacier in Google Earth imagery from 1998 and 2016.  The dark orange line is the 1998 margin, we mapped the margin in the field in 1995 and in 2002.  The light orange line is the 2007 margin and the yellow line the 2016 margin. Note crevassing diminished as well.



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