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AGU Research Spotlight (Dec 29-Jan 05, 2016)

2017-01-06 10:34:25

I.Atmospheric Sciences

1.New Way to Gauge Lightning's Role in Ozone Formation

Comparing satellite data on a key airborne ozone precursor to readings from a lightning sensor network reveals how much different types of lightning strokes affect atmospheric ozone chemistry.


2.Wave Gliding in the Eye of the Storm

Scientists use a new remote-controlled robot to capture data from the middle of an open ocean typhoon.


II.Space & Planets

1.Retracing the First Spaceborne Electric Field Measurement

Fifty years ago, a sounding rocket made history by taking the first measurement of an electric field in space. What techniques were used to capture this data?


III.Hydrology, Cryosphere & Earth Surface

1.West Antarctic Ice Shelf Breaking Up from the Inside Out

Researchers trace the origin of a 2015 iceberg to a crack that formed deep beneath the ice.


2.The Pace of Change on Tropical Landscapes

Emerging Issues in Tropical Ecohydrology; Cuenca, Ecuador, 5–9 June 2016


3.Using Landsat to Take the Long View on Greenland's Glaciers

A new web-based data portal gives scientists access to more than 40 years of satellite imagery, providing seasonal to long-term insights into outflows from Greenland's ice sheet.


IV. Hazards & Disasters

1.Pinpointing the Trigger Behind Yellowstone's Last Supereruption

Geologists suggest that mixing of magma melt pockets could have caused the explosion a little more than 600,000 years ago.


V. Geophysical Research Letters

1. Statistical distribution of EMIC wave spectra: Observations from Van Allen Probes

It has been known that electromagnetic ion cyclotron (EMIC) waves can precipitate ultrarelativistic electrons through cyclotron resonant scattering. However, the overall effectiveness of this mechanism has yet to be quantified, because it is difficult to obtain the global distribution of EMIC waves that usually exhibit limited spatial presence. We construct a statistical distribution of EMIC wave frequency spectra and their intensities based on Van Allen Probes measurements from September 2012 to December 2015. Our results show that as the ratio of plasma frequency over electron gyrofrequency increases, EMIC wave power becomes progressively dominated by the helium band. There is a pronounced dawn-dusk asymmetry in the wave amplitude and the frequency spectrum. The frequency spectrum does not follow the commonly used single-peak Gaussian function. Incorporating these realistic EMIC wave frequency spectra into radiation belt models is expected to improve the quantification of EMIC wave scattering effects in ultrarelativistic electron dynamics.


2. ENSO modulation of tropical Indian Ocean subseasonal variability

In this study, we use 30?years of retrospective climate model forecasts and observational estimates to show that El Ni?o/Southern Oscillation (ENSO) affects the amplitude of subseasonal variability of sea surface temperature (SST) in the southwest Indian Ocean, an important Tropical Intraseasonal Oscillation (TISO) onset region. The analysis shows that deeper background mixed-layer depths and warmer upper ocean conditions during El Ni?o reduce the amplitude of the subseasonal SST variability over Seychelles-Chagos Thermocline Ridge (SCTR), which may reduce SST-wind coupling and the amplitude of TISO variability. The opposite holds for La Ni?a where the shallower mixed-layer depth enhances SST variability over SCTR, which may increase SST-wind coupling and the amplitude of TISO variability.


3. Dust-infused baroclinic cyclone storm clouds: The evidence, meteorology, and some implications

Desert mineral dust is a critical yet still poorly understood component of atmospheric composition, weather, and climate. Long-range transport of dust is well known, yet uncertainty persists regarding the pathway from the desert floor to the free troposphere. Here we will show that a recurrent pathway for dust into the uppermost troposphere involves passage through an extratropical baroclinic cyclonic storm. The evidence derives from a synergistic use of satellite-based, multispectral nadir-image data and lidar. The dust-infused baroclinic storm (DIBS) exhibits peculiar cirrus cloud top reflected and emitted radiance from the UV through thermal IR, involving positive UV absorbing aerosol index, muted visible reflectivity, visible cumuliform texture, and systematically intense visible lidar backscatter on a synoptic scale. Proof that the DIBS is microphysically impacted by storm-scale dust infusion is the occurrence of anomalously large daytime 3.9–11μm brightness temperature difference indicative of small ice crystals. We present multispectral snapshots of two DIBS, over two desert source regions, in comparison with a pristine baroclinic storm cloud. Each storm snapshot is presented in the context of the baroclinic cyclone's lifetime and dust source region (the Gobi desert and the Sahara). These and other cases discussed show that the DIBS is a recurring conduit for long-range transport and a natural experiment in dust-related aerosol indirect effects.


4. First mesopause Na retrievals from satellite Na D-line nightglow observations

We report the retrieval of Na concentration profiles in the mesopause region from satellite observations of the Na D-line nightglow emission near 589 nm made by the Scanning Imaging Absorption Spectrometer for Atmospheric Chartography (SCIAMACHY) on the Envisat spacecraft. The retrieval assumes the Na D-line excitation mechanism originally proposed by Chapman in 1939. The retrieval approach, including treatment of self-absorption by Na, a retrieval uncertainty budget, and first retrieval results, is presented. The retrieved Na profiles are compared to independent satellite measurements. Good agreement in terms of peak altitude, peak concentration, and vertical column density is found. The retrievals constitute the first Na profile retrievals from satellite observations of the Na D-line nightglow emission profile. They enable our understanding of the Na nightglow excitation mechanism to be tested.


5. A quasi-global assessment of changes in remotely sensed rainfall extremes with temperature

The dependence between extreme rainfall and temperature is used to understand climatic relationships, constrain model predictions, and evaluate future changes to rainfall. Understanding this dependence, however, is limited by the fact that many areas worldwide lack gauged data, particularly at short time scales. The advent of remote sensing allows a new insight into this dependence quasi-globally. Here we address whether remotely sensed daily rainfall and temperature can be used in ungauged areas to understand extreme rainfall scaling with temperature. Using the multisensor Tropical Rainfall Measuring Mission 3B42 (v7) rainfall product and remotely sensed air temperature, we examine the spatial homogeneity in remotely sensed rainfall scaling with temperature and demonstrate that it replicates the spatial variation in the scaling observed in ground data. Finally, changes to duration and percentile are examined showing that the scaling response is climatologically sensitive.


6. A study of the dissociative recombination of CaO+ with electrons: Implications for Ca chemistry in the upper atmosphere

The dissociative recombination of CaO+ ions with electrons has been studied in a flowing afterglow reactor. CaO+ was generated by the pulsed laser ablation of a Ca target, followed by entrainment in an Ar+ ion/electron plasma. A kinetic model describing the gas-phase chemistry and diffusion to the reactor walls was fitted to the experimental data, yielding a rate coefficient of (3.0?±?1.0)?×?10?7?cm3?molecule?1?s?1at 295?K. This result has two atmospheric implications. First, the surprising observation that the Ca+/Fe+ ratio is ~8 times larger than Ca/Fe between 90 and 100?km in the atmosphere can now be explained quantitatively by the known ion-molecule chemistry of these two metals. Second, the rate of neutralization of Ca+ ions in a descending sporadic E layer is fast enough to explain the often explosive growth of sporadic neutral Ca layers.



1.Gas released from rocks can predict impending breakage

Small amounts of helium and argon gas released from rocks under stress could be used to predict rock breakage before it occurs, such as during an earthquake or in an underground mine, according to new research. This kind of early-warning signal could be useful for keeping people safe in situations where rock is under high stress, like mining or construction operations, according to the study’s authors.


2.Scientists test less invasive methods of locating oil in deep sea

New techniques for finding oil beneath the seafloor could reduce the frequency of seismic testing or exploratory drilling, which is harmful to marine animals, according to new research.


3.2016 Ends With Astonishing Warmth and Gloomy News from Antarctica

My fellow science geeks have been posting some rather astonishing climate plots on Twitter over the past few days, and it’s reached the point of doing a post about them. So here are some graphs/info about the warmth, along with some frightening news from Antarctica that didn’t get the attention it deserved. First of all, 2016 will be the new hottest year on record globally, and we’ve also reached 25 consecutive months …


4.The Smoking Gun of Arctic Warmth Leads To A Stunning Indictment

It normally takes many months to get a paper through peer review and into a journal, but a group of scientists has released their detection and attribution study early, and it’s a stunning indictment. We now know the culprit for the astonishing Arctic warmth of November and December. It seemed very likely that the guilty party was rising greenhouse gasses with Arctic amplification as the accomplice, and that’s JUST what …



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