Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:p>We introduce a novel agent‐based model for simulating interactions between migrating barchan dunes. A new two‐flank representation of barchans allows modeling of bedform asymmetries that are intrinsic to collision dynamics but have not been explored before. Although simple compared with real‐world barchans or those in continuum and cellular automata simulations, all known barchan behaviors emerge from the rules of our model. In particular, the two mechanisms for asymmetry growth in bimodal winds are observed and qualitatively agree with existing theories. We also reproduce the emergence of calving and all types of collisions that have been reported in reductionist models, water‐tank experiments, and field observations. The computational efficiency of the new model, compared with continuum simulations, enables the simulation of large swarms of dunes while maintaining the complex phenomenology of these bedforms, some of which has been lacking in previous agent‐based models.</jats:p>

<jats:p>No abstract is available for this article.</jats:p>

<jats:title>Abstract</jats:title><jats:p>During the Arctic night, clouds regulate surface energy budgets through longwave warming alone. During fall, any increase in low‐level clouds will increase surface cloud warming and could potentially delay sea ice formation. While an increase in clouds due to fall sea ice loss has been observed, quantifying the surface warming is observationally challenging. Here, we use a new observational data set of surface cloud warming at instantaneous 330 m × 90 m spatial resolution. By instantaneously co‐locating surface cloud warming and sea ice observations in regions where sea ice varies, we find October large surface cloud warming values (&gt;80 W m<jats:sup>−2</jats:sup>) are much more frequent (∼+50%) over open water than over sea ice. Notably, in November large surface cloud warming values (&gt;80 W m<jats:sup>−2</jats:sup>) occur more frequently (∼+200%) over open water than over sea ice. These results suggest more surface warming caused by low‐level opaque clouds in the future as open water persists later into the fall.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The influence of climate feedbacks on regional hydrological changes under warming is poorly understood. Here, a moist energy balance model (MEBM) with a Hadley Cell parameterization is used to isolate the influence of climate feedbacks on changes in zonal‐mean precipitation‐minus‐evaporation (<jats:italic>P</jats:italic> − <jats:italic>E</jats:italic>) under greenhouse‐gas forcing. It is shown that cloud feedbacks act to narrow bands of tropical <jats:italic>P</jats:italic> − <jats:italic>E</jats:italic> and increase <jats:italic>P</jats:italic> − <jats:italic>E</jats:italic> in the deep tropics. The surface‐albedo feedback shifts the location of maximum tropical <jats:italic>P</jats:italic> − <jats:italic>E</jats:italic> and increases <jats:italic>P</jats:italic> − <jats:italic>E</jats:italic> in the polar regions. The intermodel spread in the <jats:italic>P</jats:italic> − <jats:italic>E</jats:italic> changes associated with feedbacks arises mainly from cloud feedbacks, with the lapse‐rate and surface‐albedo feedbacks playing important roles in the polar regions. The <jats:italic>P</jats:italic> − <jats:italic>E</jats:italic> change associated with cloud feedback locking in the MEBM is similar to that of a climate model with inactive cloud feedbacks. This work highlights the unique role that climate feedbacks play in causing deviations from the “wet‐gets‐wetter, dry‐gets‐drier” paradigm.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The Southern Ocean plays a major role in controlling the evolution of Antarctic glaciers and in turn their impact on sea level rise. We present the Southern Ocean high‐resolution (SOhi) simulation of the MITgcm ocean model to reproduce ice‐ocean interaction at 1/24° around Antarctica, including all ice shelf cavities and oceanic tides. We evaluate the model accuracy on the continental shelf using Marine Mammals Exploring the Oceans Pole to Pole data and compare the results with three other MITgcm ocean models (ECCO4, SOSE, and LLC4320) and the ISMIP6 temperature reconstruction. Below 400 m, all the models exhibit a warm bias on the continental shelf, but the bias is reduced in the high‐resolution simulations. We hypothesize some of the bias is due to an overestimation of sea ice cover, which reduces heat loss to the atmosphere. Both high‐resolution and accurate bathymetry are required to improve model accuracy around Antarctica.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The South Atlantic Anomaly (SAA) refers to a region where the strength of the magnetic field is notably weaker compared to a dipole field. While previous studies have primarily focused on its effects on the inner radiation belt, this study investigates its impact on the aurora system. By analyzing 2 years' worth of data obtained by the Fengyun‐3E/ACMag instrument, we discover that magnetic fluctuations within the auroral oval are significantly weaker in the longitude sector corresponding to the SAA, as compared to those outside this area. This characteristic remains permanent and independent of seasons and geomagnetic activities. Additional investigation using Defense Meteorological Satellite Program/Special Sensor Ultraviolet Spectrographic Imager (DMSP/SSUSI) observations reveals a similar phenomenon in the auroral intensity. Therefore, our results demonstrate that the SAA substantially weakens the aurora system, shedding new light on the effects of magnetic anomalies on planetary auroras and magnetosphere‐ionosphere‐thermosphere coupling.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Flux transfer events (FTEs) are transient magnetic flux ropes at Earth's dayside magnetopause formed due to magnetic reconnection. As they move across the magnetopause surface, they can generate disturbances in the ultralow frequency (ULF) range, which then propagate into the magnetosphere. This study provides evidence of ULF waves in the Pc2 wave frequency range (&gt;0.1 Hz) caused by FTEs during dayside reconnection using a global 3D hybrid‐Vlasov simulation (Vlasiator). These waves resulted from FTE formation and propagation at the magnetopause are particularly associated with large, rapidly moving FTEs. The wave power is stronger in the morning than afternoon, showing local time asymmetry. In the pre and postnoon equatorial regions, significant poloidal and toroidal components are present alongside the compressional component. The noon sector, with fewer FTEs, has lower wave power and limited magnetospheric propagation.</jats:p>

<jats:title>Abstract</jats:title><jats:p>Detecting the response of the Atlantic meridional overturning circulation (AMOC) to anthropogenic warming can only be made with fingerprints indirectly because of the lack of sufficiently long direct measurements. However, whether the relationship between the AMOC and its fingerprints is stationary is rarely examined. This study uses coupled and ocean‐alone model simulations to investigate the sensitivity of two typical AMOC fingerprints under future anthropogenic warming. We found a lower sensitivity of the North Atlantic warming hole fingerprint in future warming scenarios associated with the differing vulnerability of deep‐water origins to external forcing and climate feedback. In contrast, the remote South Atlantic salinity pile‐up fingerprint is relatively insensitive to variations in AMOC sources, and its sensitivity to the AMOC is slightly enhanced by an intensified hydrological cycle. Our study implies that fingerprints outside the northern deep convection region may become more suitable in representing the response of AMOC to future warming.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The temporal relationship between global glaciations and the Great Oxidation Event (GOE) suggests that climate change played an important role in Earth's oxygenation. The potential role of temperature is captured by the stratigraphic proximity between glacial deposits and sediments containing mass‐independent fractionation of sulfur isotopes (MIF‐S). We use a time‐dependent one‐dimensional photochemical model to investigate whether temperature changes associated with global glaciations can drive oscillations in atmospheric O<jats:sub>2</jats:sub> levels and MIF‐S production across the GOE. We find that extreme climate change can cause atmospheric O<jats:sub>2</jats:sub> to oscillate between pre (&lt;10<jats:sup>−6</jats:sup> times the present atmospheric level, PAL) and post‐GOE (&gt;10<jats:sup>−5</jats:sup> PAL) levels. Post‐glacial hot‐moist greenhouse climates lead to post‐GOE O<jats:sub>2</jats:sub> levels because the abundant H<jats:sub>2</jats:sub>O vapor and oxidizing radicals drive the depletion of reduced species. This pattern is generally consistent with the MIF‐S signal observed in the sedimentary record, suggesting a link between global glaciations and O<jats:sub>2</jats:sub> oscillations across the GOE.</jats:p>

<jats:title>Abstract</jats:title><jats:p>The complex and diverse cloud vertical distribution (CVD) largely impacts radiative and precipitation properties of clouds. Using 10‐year active satellite observations, we classified CVD over the Tibetan Plateau into 12 categories and found that overlapping clouds have less frequency but stronger radiative effect, heating rate and larger precipitation (partly reflecting the seeding effect) compared with single‐layer non‐strong convective clouds. Under a warming climate due to uniform sea surface temperature increase of 4K (quadrupling CO<jats:sub>2</jats:sub> increase), extremely high (&gt;10 km) ice clouds will increase, particularly those below the tropopause will increase slightly (largely), accompanied by clear (weak) increases in stratospheric clouds. Simultaneously, a moderate to rapid decrease will occur in clouds below 10 km. Such CVD changes could further exacerbate tropopause warming. The probability of cloud overlap is also likely to increase in warmer climates, thus possibly further causing non‐convective cloud systems with stronger intra‐atmospheric heating, larger precipitation intensity and proportion.</jats:p>