Turbulence, temperature changes, water vapor, carbon dioxide, ozone, methane, and other gases absorb, reflect, and scatter sunlight as it passes through the atmosphere, bounces off the Earth's surface, and is collected by a sensor on a remote sensing satellite. As a result, the spectral data received at the sensor is distorted.
Consistent point data assimilation in Firedrake and Icepack
Reuben W. Nixon-Hill, Daniel Shapero, Colin J. Cotter, and David A. Ham
Geosci. Model Dev., 17, 5369–5386, https://doi.org/10.5194/gmd-17-5369-2024, 2024
Scientists often use models to study complex processes, like the movement of ice sheets, and compare them to measurements for estimating quantities that are hard to measure. We highlight an approach that ensures accurate results from point data sources (e.g. height measurements) by evaluating the numerical solution at true point locations. This method improves accuracy, aids communication between scientists, and is well-suited for integration with specialised software that automates processes.
STORM v.2: A simple, stochastic rainfall model for exploring the impacts of climate and climate change at and near the land surface in gauged watersheds
Manuel F. Rios Gaona, Katerina Michaelides, and Michael Bliss Singer
Geosci. Model Dev., 17, 5387–5412, https://doi.org/10.5194/gmd-17-5387-2024, 2024
STORM v.2 (short for STOchastic Rainfall Model version 2.0) is an open-source and user-friendly modelling framework for simulating rainfall fields over a basin. It also allows simulating the impact of plausible climate change either on the total seasonal rainfall or the storm’s maximum intensity.
The Ensemble Consistency Test: From CESM to MPAS and Beyond
Teo Price-Broncucia, Allison Baker, Dorit Hammerling, Michael Duda, and Rebecca Morrison
Geosci. Model Dev. Discuss., https//doi.org/10.5194/gmd-2024-115,2024
Preprint under review for GMD (discussion: open, 0 comments)
The Ensemble Consistency Test (ECT) and its Ultra-Fast variant (UF-ECT) have become powerful tools in the development community for the identification of unwanted changes in the Community Earth System Model (CESM). We develop a generalized setup framework to enable easy adoption of the ECT approach for other model developers and communities. This framework specifies test parameters to accurately characterize model variability and balance test sensitivity and computational cost.
Although it is surrounded by stressed coral reefs, an island in the Indonesian Spermonde Archipelago has not shrunk but continued to grow. Reef islands hence react dynamically to environmental changes that disturb their reef systems, according to a new study by researchers from the Leibniz Center for Tropical Marine Research (ZMT) in Bremen, Germany.
Severe droughts in the Amazon basin over the past two decades have caused low water level periods to last around a month longer than usual, triggering profound impacts on the local population.
New Monash research has untangled the influence of regional climate drivers, including the Southern Annular Mode (SAM) and the El Niño-Southern Oscillation (El Niño), on the Antarctic Ice Sheet. Snow accumulation and surface melting are two important processes that are key to predicting how Antarctica will contribute to future sea level rise.
Abstract
The fault zone architecture may provide reliable information about the deformations in both on-fault and off-fault media. The outer damage zones of faults may extend for kilometers and exhibit structural anisotropy, which potentially causes electrical anisotropy in rocks. Thus, electrically anisotropic structures may indicate the dimensions and extent of fault damage zones. We investigated the electrical anisotropic structure of the sinistral Altyn Tagh fault (ATF), NW China, using magnetotelluric data collected in and around the Subei Basin. Our three-dimensional resistivity model reveals widespread anisotropic anomalies at depths <∼5 km. The directions of the minimum horizontal resistivity values of the anomalies inside the Qilian Shan southeast of the ATF are dominantly subparallel to the fault traces at the surface. At deeper levels (∼15–19 km and ∼33–43 km), the anisotropic anomalies are mainly concentrated near the northern strand of the ATF (NATF) and the North Yemahe fault (NYMF) in the northeastern Subei area. The mid-lower crust (∼33–43 km) inside the Qilian Shan is characterized by isotropy or weak anisotropy with low resistivities (∼10 Ωm), which deviate significantly from the values along the NATF. Our results indicate the presence of a ∼30 km wide off-fault damage zone along the NATF and NYMF in the shallow crust that thins downward to the lower crust. We propose that the distribution of anisotropic anomalies is influenced primarily by neighboring faults. An independent deformation model could be appropriate for evaluating the relationships between the ATF and thrust faults within the Qilian Shan.
The retreat of high mountain glaciers has accelerated since the 1980s, resulting in increased glacier runoff. However, it remains uncertain whether melting mountain glaciers enhance or release greenhouse gases, and whether areas exposed to glacier retreat emit or absorb such gases.
When it comes to inland surface water bodies, saline lakes are unique. They make up 44% of all lakes worldwide and are found on every continent including Antarctica. These lakes' existence depends on a delicate balance between a river basin's water input (precipitation and inflows) and output (evaporation and seepage).
Abstract
We investigate why the North American Multi-Model Ensemble (NMME) upper-level height forecast for December–February (DJF) 2023/24 differs from the expected El Niño response. These atypical height anomalies emerged despite the fact a strong El Niño was forecast. The analysis focuses on diagnosing the NMME forecasts of DJF 2023/24 for SSTs and 200-hPa heights initialized at the beginning of November 2023 relative to other ensemble mean NMME DJF forecasts dating back to 1982. The results demonstrate that forecasts of the 200-hPa height anomalies had a large contribution from warming trends in global SSTs. It is the combination of trends and the expected El Niño teleconnection that results in the forecast height anomalies. Increasingly, for forecasts of geopotential height anomalies during the recent El Niño winters, the amplitude of trends is nearly equal to the signal from El Niño and has implications for the climatological base period selection for seasonal forecasts.
Abstract
The interaction between volcanic activity and flank instability during the Christmas Eve eruption at Mount Etna in 2018 is explored, using a mechanically consistent inverse model fitting high spatial resolution SAR data. Inversions search for fractures that may be curved and can accommodate co-eval pressure and shear stress changes. Displacements associated with the eruption result from the interaction between two intrusion sources: a buried dyke and a curved sheared intrusion that fed the eruption. Moreover, we identify that the sheared magmatic intrusion induced the observed eastward slip on the Pernicana fault, while the Fiandaca fault was undergoing stress accumulation, which was suddenly released during a M5.0 seismic event. The Fiandaca fault is determined to be listric, rooting beneath the mobile eastern flank of the volcano. This study highlights the role of curved fractures, acting as sheared intrusions or as faults, in volcanoes exhibiting flank instabilities.
Abstract
Grabens, or valleys formed during extensional tectonic events, are common but rarely observed during formation. In November 2023, inelastic surface deformation formed abruptly along Iceland's plate boundary in Grindavík. We documented graben formation in real-time through satellite mapping (InSAR), seismicity, GNSS data, repeated lidar surveys, and field mapping. Five normal faults and ∼12 fissures ruptured the surface delineating two grabens separated by a horst, a context not present in other contemporary case studies. The graben normal faults slipped rapidly (over hours) and maximum surface motions coincided with the occurrence of turbulent seismic swarms in both space and time. Although 3 eruptions took place ∼15 km northeast of Grindavík from 2021 to 2023, attributed to magma intrusions (i.e., dikes), none of these also formed grabens. Thus, the Grindavík grabens shows evidence for tectonic origins. Real-time monitoring of these phenomena provide insight into graben formation on Earth and potentially on other planets.
Abstract
State-of-the-art coupled climate models struggle to accurately simulate historical variability and trends of Antarctic sea ice, impacting their reliability for future projections. Increasing horizontal resolution is expected to improve the representation of coupled atmosphere-ice-ocean processes at high latitudes. Here, we examine the historical changes in the Antarctic sea ice area and volume in High Resolution Model Intercomparison Project simulations against satellite data sets and ocean reanalyzes to assess the benefits of increased spatial resolution. Our results do not show considerable benefits when horizontal resolutions up to 0.25° in the ocean and 25 km in the atmosphere. Limited improvements are reported in the simulated historical sea ice trends, which are nevertheless model-dependent, and associated with the use of model components with more complex sea-ice parameterizations. Given the high computational cost of climate-scale simulations at high spatial resolution, we advocate prioritizing enhancements in sea-ice physics and the interactions among model components in coupled climate simulations.
Bridging classical data assimilation and optimal transport: the 3D-Var case
Marc Bocquet, Pierre J. Vanderbecken, Alban Farchi, Joffrey Dumont Le Brazidec, and Yelva Roustan
Nonlin. Processes Geophys., 31, 335–357, https://doi.org/10.5194/npg-31-335-2024, 2024
A novel approach, optimal transport data assimilation (OTDA), is introduced to merge DA and OT concepts. By leveraging OT's displacement interpolation in space, it minimises mislocation errors within DA applied to physical fields, such as water vapour, hydrometeors, and chemical species. Its richness and flexibility are showcased through one- and two-dimensional illustrations.
Characteristic features of latitudinal manifestations of the 23–24 April 2023 geomagnetic storm
Leonid Chernogor
Ann. Geophys. Discuss., https//doi.org/10.5194/angeo-2024-9,2024
Revised manuscript under review for ANGEO (discussion: final response, 6 comments)
Ground-based magnetometer observations show that part of the near-Earth cross-tail current closed itself via the ionosphere, to which it was linked by the substorm current wedge, and manifested itself in the magnetograms acquired at high and equatorial latitude stations on the night side of the Earth. Observations suggest that the Bz interplanetary magnetic field component threshold for the formation of the substorm current wedge lies in the –(22–30) nT interval.
Author(s): Zifan Zhou, Yael Sternfeld, Jacob Scheuer, and Selim M. Shahriar
We describe a generalized algorithm for evaluating the steady-state solution of the density matrix equation of motion, for the pump-probe scheme, when two fields oscillating at different frequencies couple the same set of atomic transitions involving an arbitrary number of energy levels, to an arbit…
[Phys. Rev. E 110, 015304] Published Fri Jul 12, 2024
Lakes, with their rich biodiversity and important ecological services, face a concerning trend: rapidly increasing temperatures. A recent study published in Nature Geoscience by an international team of limnologists and climate modelers reveals that if current anthropogenic warming continues until the end of this century, lakes worldwide will likely experience pervasive and unprecedented surface and subsurface warming, far outside the range of what they have encountered before.
Abstract
Temperatures and pressures from high explosive detonations far exceed atmospheric conditions in typical combustion reactions, and consequently, detonation soot forms with physiochemical properties distinct from soot formed by combustion. In this study, samples of detonation soot from two high explosives, PBX 9502 and Composition B-3, were analyzed. Ice nucleation experiments on soot collected after controlled detonations were conducted in the laboratory to probe immersion and contact mode freezing. Samples nucleated ice at temperatures warmer than commercially available nanodiamonds, which has a mean nucleation temperature of −20.7°C. Ice nucleation rate coefficients increase rapidly by two to three orders of magnitude below −20°C for every sample. Size-selected 137 μm diameter particles produced during detonation in an ambient air atmosphere yield bimodal distributions of freezing temperature with primary and secondary nucleation modes centered at −20°C and −13°C, respectively. The presence of a secondary mode allows for enhanced ice nucleation rate coefficients (one to two orders of magnitude greater than samples without a secondary mode) at temperatures outside the influence of the primary mode (>−17°C). Given the observed onset nucleation temperatures of −9.2°C, our results imply that detonation soot of the type studied here would only need to reach an altitude of approximately 4 km to facilitate ice formation.
Abstract
The Atmospheric InfraRed Sounder (AIRS) aboard Aqua provides essential long-term data on vertical cloud fraction, particularly valuable in the Arctic region. This study offers a comprehensive assessment of Arctic vertical cloud fraction derived from AIRS through a comparison with independent ground- and space-based radar and lidar observations. In comparison to the measurements at the North Slope Alaska site, results reveal a significant underestimation of low-level cloud cover by AIRS, especially for near-surface clouds, while mid- and high-level cloud fractions show better consistency. In comparison to the satellite-based product from 3S-GEOPROF-COMB, the accuracy varies across different underlying surfaces (land vs. sea) and seasons. AIRS shows significant positive biases in mid-level cloud fraction over sea surfaces with sea ice concentration below 15%, indicating potential limitations in the cloud retrieval algorithm in regions with large sea ice variations. The issue of low-level clouds identification is primarily caused by the limited penetrating capability of infrared hyperspectral sensing and the accuracy of preceding surface and atmospheric state products, which diminish the accuracy of AIRS low-level cloud fraction.
