Abstract
Slow Slip Events (SSEs) are like long-duration slow earthquakes during which stress is gradually released over several days to months, and a comprehensive catalog of SSEs is essential for a better understanding of the earthquake cycle. However, SSEs usually only produce mm to cm surface deformations, making them a challenge to identify from raw Global Navigation Satellite System (GNSS) time series, which are often obscured by low-frequency background noise. We devise an approach that first employs variational Bayesian Independent Component Analysis to improve the signal-to-noise ratio of GNSS time series and then utilizes deep learning combining bidirectional Long Short-Term Memory and two different attention mechanisms to identify SSEs. We apply this new method to the GNSS three-component time series at 240 stations along the Cascadia subduction zone from 2012 to 2022. A total of 56 SSEs are detected, 18 more than the number in the existing SSEs catalogs during the same period. The starting time, duration, spatial and propagation pattern of the 56 SSEs are consistent with the tremor catalog, which helps to gain new insights into the slip behavior in the Cascadia subduction zone. In general, our work provides an effective framework for extracting subtle signals hidden in GNSS time series.
Abstract
Multipath effect is one of the major challenges for Global Navigation Satellite Systems (GNSS) to achieve millimeter-level high-precision positioning and orbit determination. Wavelet Transform (WT) and Sidereal Filtering (SF) can effectively extract and mitigate multipath errors. Therefore, they are widely used in ground deformation monitoring and high precise GNSS applications. In view of this, the selection of refined wavelet decomposition levels and thresholds is critical for better extraction and mitigation of multipath errors. In this paper, we systematically analyze the performance of multipath error mitigation in Single-Difference (SD) and Double-Difference (DD) residuals based on different wavelet decomposition levels, thresholds and threshold functions. The results show that both DD SF and SD SF can effectively mitigate multipath errors. Compared to the traditional positioning, the positioning accuracy using the adopted SD SF in the east, north and up direction are improved by about 30.42%, 8.54% and 12.49%, respectively, which is slightly better than DD SF. For wavelet decomposition levels, the RMS of the rigrsure (Stein unbiased risk estimate), heursure (universal threshold, square root log), sqtwolog (combination of sqtwolog and rigrsure methods) and minimax (minimize the maximum mean squared error) thresholds at level 6 is the smallest among levels 1–10 of wavelet decomposition. For wavelet thresholds, the positioning performance of the heursure and sqtwolog thresholds is better that that of the rigrsure and minimax thresholds. For threshold functions, the positioning performance of four thresholds in the soft threshold function is slightly better than that in the hard threshold function.
A Rutgers University-New Brunswick-led research team employing an emerging technique to detect signs of past hurricanes in coastal sediments has found evidence of storms dating back more than 400 years. In doing so, they have confirmed an approach that could give them a better understanding of how the frequency of storms changes when the climate changes.
Scientists from The University of Manchester, The University of Aberdeen and Newcastle University have found that the restoration of upland peatlands is a highly effective strategy for reducing downstream flooding.
To better predict long-term flooding risk, scientists at the Department of Energy's Oak Ridge National Laboratory developed a 3D modeling framework that captures the complex dynamics of water as it flows across the landscape. The framework seeks to provide valuable insights into which communities are most vulnerable as the climate changes, and was developed for a project that's assessing climate risk and mitigation pathways for an urban area along the Southeast Texas coast.
How are rivers characterized? Traditional methods rely on plant forms and sedimentological techniques, focusing on deposits. Riccardo Maitan, a Ph.D. candidate at the University of Padova, is developing a novel approach based on river hydrological behavior, emphasizing morphodynamics. His work aims to identify the signature of peak discharge variability—a key hydrological metric—in meandering rivers. This research spans over 15 years of USGS data and Google Earth image time series.
An oxidation flow reactor for simulating and accelerating secondary aerosol formation in aerosol liquid water and cloud droplets
Ningjin Xu, Chen Le, David R. Cocker, Kunpeng Chen, Ying-Hsuan Lin, and Don R. Collins
Atmos. Meas. Tech., 17, 4227–4243, https://doi.org/10.5194/amt-17-4227-2024, 2024
A flow-through reactor was developed that exposes known mixtures of gases or ambient air to very high concentrations of the oxidants that are responsible for much of the chemistry that takes place in the atmosphere. Like other reactors of its type, it is primarily used to study the formation of particulate matter from the oxidation of common gases. Unlike other reactors of its type, it can simulate the chemical reactions that occur in liquid water that is present in particles or cloud droplets.
Unfiltering of the EarthCARE Broadband Radiometer (BBR) observations: the BM-RAD product
Almudena Velázquez Blázquez, Edward Baudrez, Nicolas Clerbaux, and Carlos Domenech
Atmos. Meas. Tech., 17, 4245–4256, https://doi.org/10.5194/amt-17-4245-2024, 2024
The Broadband Radiometer measures shortwave and total-wave radiances filtered by the spectral response of the instrument. To obtain unfiltered solar and thermal radiances, the effect of the spectral response needs to be corrected for, done within the BM-RAD processor. Errors in the unfiltering are propagated into fluxes; thus, accurate unfiltering is required for their proper estimation (within BMA-FLX). Unfiltering errors are estimated to be <0.5 % for the shortwave and <0.1 % for the longwave.
Using metal oxide gas sensors to estimate the emission rates and locations of methane leaks in an industrial site: assessment with controlled methane releases
Rodrigo Rivera-Martinez, Pramod Kumar, Olivier Laurent, Gregoire Broquet, Christopher Caldow, Ford Cropley, Diego Santaren, Adil Shah, Cécile Mallet, Michel Ramonet, Leonard Rivier, Catherine Juery, Olivier Duclaux, Caroline Bouchet, Elisa Allegrini, Hervé Utard, and Philippe Ciais
Atmos. Meas. Tech., 17, 4257–4290, https://doi.org/10.5194/amt-17-4257-2024, 2024
We explore the use of metal oxide semiconductors (MOSs) as a low-cost alternative for detecting and measuring CH4 emissions from industrial facilities. MOSs were exposed to several controlled releases to test their accuracy in detecting and quantifying emissions. Two reconstruction models were compared, and emission estimates were computed using a Gaussian dispersion model. Findings show that MOSs can provide accurate emission estimates with a 25 % emission rate error and a 9.5 m location error.
The CHIMERE chemistry-transport model v2023r1
Laurent Menut, Arineh Cholakian, Romain Pennel, Guillaume Siour, Sylvain Mailler, Myrto Valari, Lya Lugon, and Yann Meurdesoif
Geosci. Model Dev., 17, 5431–5457, https://doi.org/10.5194/gmd-17-5431-2024, 2024
A new version of the CHIMERE model is presented. This version contains both computational and physico-chemical changes. The computational changes make it easy to choose the variables to be extracted as a result, including values of maximum sub-hourly concentrations. Performance tests show that the model is 1.5 to 2 times faster than the previous version for the same setup. Processes such as turbulence, transport schemes and dry deposition have been modified and updated.
As sea ice disappears and grows less reflective, the Arctic has lost around a quarter of its cooling power since 1980, and the world has lost up to 15%, according to new research led by University of Michigan scientists.
In August 2023, 14,000 cubic meters of sandstone and shale detached from a slope in the French Alps. This rockslide at La Praz closed a road and a major railway between France and Italy at least until the end of 2024.
Micro-business participation in collective flood adaptation: lessons from scenario-based analysis in Ho Chi Minh City, Vietnam
Javier Revilla Diez, Roxana Leitold, Van Tran, and Matthias Garschagen
Nat. Hazards Earth Syst. Sci., 24, 2425–2440, https://doi.org/10.5194/nhess-24-2425-2024, 2024
Micro-businesses, often overlooked in adaptation research, show surprising willingness to contribute to collective adaptation despite limited finances and local support. Based on a study in Ho Chi Minh City in Vietnam, approximately 70 % are ready for awareness campaigns, and 39 % would provide financial support if costs were shared. These findings underscore the need for increased involvement of micro-businesses in local adaptation plans to enhance collective adaptive capacity.
When it comes to diatoms that live in the ocean, new research suggests that photosynthesis is not the only strategy for accumulating carbon. Instead, these single-celled plankton are also building biomass by feeding directly on organic carbon in wide swaths of the ocean.
Skoltech researchers and their colleagues from Sber have proposed deep learning models that predict droughts using climate data. Long-term forecasts of this kind are sought by agricultural producers planning their operations, as well as by insurance companies and banks evaluating climate risks and fine-tuning corporate credit ratings.
Scientists have for the first time taken in-situ ocean measurements during the collapse of a giant iceberg in the sub-Antarctic. These new observations reveal how ocean ecosystems may be affected if more icebergs calve due to warmer ocean temperatures around Antarctica.
An international team of scientists led by Dr. Luis Guanter, UPV professor and head of the LARS Group of the Institute of Water and Environmental Engineering of the Universitat Politècnica de València (IIAMA-UPV), has documented the largest methane leak ever recorded in an oil well. The well is located in the Karaturun East field (Kazajistán).
Where hidden water tables meet the Earth's surface, life can thrive even in the driest locations. Offering refuge during times of drought, shallow groundwater aquifers act like water savings accounts that can support ecosystems with the moisture required to survive, even as precipitation dwindles.
Despite facing regional threats like deforestation and wildfires, the world's forests continue to be a powerful weapon in the fight against climate change. A new study reveals these vital ecosystems have consistently absorbed carbon dioxide for the past three decades, even as disruptions chip away at their capacity.
Abstract
Tropospheric ozone (O3) is an important greenhouse gas that is also hazardous to human health. The formation of O3 is sensitive to the levels of its precursors NOx (≡NO + NO2) and peroxy radicals, for example, generated by the oxidation of volatile organic compounds (VOCs). A better understanding of this sensitivity will show how changes in the levels of these trace gases could affect O3 levels today and in the future, and thus air quality and climate. In this study, we investigate O3 sensitivity in the tropical troposphere based on in situ observations of NO, HO2 and O3 from four research aircraft campaigns between 2015 and 2023. These are OMO (Oxidation Mechanism Observations), ATom (Atmospheric Tomography Mission), CAFE Africa (Chemistry of the Atmosphere Field Experiment in Africa) and CAFE Brazil, in combination with simulations using the EMAC atmospheric chemistry—climate model. We use the metric α(CH3O2) together with NO to investigate the O3 formation sensitivity. We show that O3 formation is generally NOx-sensitive in the lower and middle tropical troposphere and is in a transition regime in the upper troposphere. By distinguishing observations impacted by lightning or not we show that NO from lightning is the most important driver of O3 sensitivity in the tropics. NOx-sensitive chemistry predominates in regions without lightning impact, with α(CH3O2) ranging between 0.56 and 0.82 and observed average O3 levels between 35 and 55 ppbv. Areas affected by lightning exhibit strongly VOC-sensitive O3 chemistry with α(CH3O2) of about 1 and average O3 levels between 55 and 80 ppbv.
