Abstract
A three-dimensional winter (DJF) climatology of Lagrangian diffusivity characterizing eddy mixing and transport in the northern middle atmosphere is presented. To emphasize aspects other than zonal averages, we use the theory of Lagrangian diffusivity (κ
yy
) hitherto not applied in stratospheric contexts to our knowledge. Our formulation of Lagrangian diffusivity requires the calculation of parcel trajectories, which is made on isentropic surfaces. A Lagrangian descriptor is used to estimate the boundary of the stratospheric polar vortex (SPV). To characterize quasi-geostrophic motions and their influence on the SPV we apply the wave activity flux (W) and Local Wave Activity (A) $(\mathcal{A})$. Our data set is the ERA5 reanalysis for the period 1979–2013. Results for κ
yy
show important zonal asymmetries. In the lower and middle stratosphere, κ
yy
is highest at midlatitudes, particularly around the prime meridian. This location is surrounded by manifolds associated with hyperbolic trajectories emanating from the outer SPV boundary. κ
yy
is also high within the SPV, and near the locations where the SPV boundary is open. Zonal asymmetries are also clear in W at midlatitudes. The larger values of A $\mathcal{A}$ are at high latitudes and upstream of the opening of the vortex boundary. The role of quasi-geostrophic waves on the south-north shift of the midlatitude westerlies is highlighted. In particular, the waves contribute to open the SPV boundary at around 90W. The interannual variability of κ
yy
is explored by contrasting winters with positive-negative Northern Annular Mode index, and Sudden Stratospheric Warmings of displacement-split type.
Abstract
The benefit of real-world applicable indicators in resolving robust traffic-related source contributions was investigated using tunnel measurement. PM2.5/CO was introduced as a metric to present evidence in non-exhaust identification indirectly in terms of PM2.5 accumulation and dilution scenarios, and the rates (hourly variation of the difference between PM2.5 and PM2.5/CO) were 0.59−1.88 and −0.79 to −0.65, corresponding to peak and off-peak hours, respectively. Real-world PAHs indicators were examined, among which the exhaust indicators showed stable applicability from BghiP, and the non-exhaust indication noted by BkF and DahA in peak hours were largely weakened in off-peak hours, showing noticeable profile mixing between exhaust, brake and tyre wear. Source contributions were resolved by principal component analysis (PCA) with support of linear discriminant analysis (LDA) on inter-group centroid diagnosis. The rate of vehicular non-exhaust (brake and tyre wear) contribution lifted 10.3 times in peak hours compared with off-peak hours, and its emission factor was noticeably enhanced 16 times, from 0.03 mg/(km·veh) to 0.48 mg/(km·veh). Guided by global vehicle electrification, the contribution of non-exhaust in vehicular emissions were estimated to increase with larger ratio of emission factor between non-exhaust and exhaust, and the growing market share of electric vehicles, under each mode of regenerative braking. The monetary impact of non-exhaust caused by electric vehicles was calculated reaching the exhaust when electric vehicles increase to 50% in busy commuting megacities. The results provide applicable indicators for accurate source apportionment and support data for the refined control of non-exhaust emission under rapid vehicle electrification.
Abstract
Dust transported from rangelands of the Southwestern United States (US) to mountain snowpack in the Upper Colorado River Basin during spring (March-May) forces earlier and faster snowmelt, which creates problems for water resources and agriculture. To better understand the drivers of dust events, we investigated large-scale meteorology responsible for organizing two Southwest US dust events from two different dominant geographic locations: (a) the Colorado Plateau and (b) the northern Chihuahuan Desert. High-resolution Weather Research and Forecasting coupled with Chemistry model (WRF-Chem) simulations with the Air Force Weather Agency dust emission scheme incorporating a MODIS albedo-based drag-partition was used to explore land surface-atmosphere interactions driving two dust events. We identified commonalities in their meteorological setups. The meteorological analyses revealed that Polar and Sub-tropical jet stream interaction was a common upper-level meteorological feature before each of the two dust events. When the two jet streams merged, a strong northeast-directed pressure gradient upstream and over the source areas resulted in strong near-surface winds, which lifted available dust into the atmosphere. Concurrently, a strong mid-tropospheric flow developed over the dust source areas, which transported dust to the San Juan Mountains and southern Colorado snowpack. The WRF-Chem simulations reproduced both dust events, indicating that the simulations represented the dust sources that contributed to dust-on-snow events reasonably well. The representativeness of the simulated dust emission and transport in different geographic and meteorological conditions with our use of albedo-based drag partition provides a basis for additional dust-on-snow simulations to assess the hydrologic impact in the Southwest US.
Abstract
Current global climate models (GCMs), limited to grid-scale land-atmosphere coupling, cannot represent subgrid urban-rural precipitation contrasts. This study develops an innovative two-way subgrid land-atmosphere coupling framework in the National Center for Atmospheric Research (NCAR) Community Earth System Model version 2 (CESM2) to explicitly resolve land-atmosphere interaction over subgrid individual land units. Results show that urban heat island (UHI) leads to the urban rainfall effect (URE), which in turn alleviates overestimated UHI over China in CESM2. The URE manifests as a shift toward more heavy precipitation and less light precipitation in world urban areas than in surrounding rural counterparts. This feature is consistent with available observations. In heavy precipitation situations, the UHI promotes atmospheric instability and enhances atmospheric water vapor holding capacity, resulting in more heavy precipitation in urban areas. Conversely, in light precipitation situations, the UHI and decreased evaporation from urban impermeable surfaces diminish atmospheric relative humidity, suppressing light precipitation.
JAXA Level2 algorithms for EarthCARE mission from single to four sensors: new perspective of cloud, aerosol, radiation and dynamics
Hajime Okamoto, Kaori Sato, Tomoaki Nishizawa, Yoshitaka Jin, Takashi Nakajima, Minrui Wang, Masaki Satoh, Kentaroh Suzuki, Woosub Roh, Akira Yamauchi, Hiroaki Horie, Yuichi Ohno, Yuichiro Hagihara, Hiroshi Ishimoto, Rei Kudo, Takuji Kubota, and Toshiyuki Tanaka
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-101,2024
Preprint under review for AMT (discussion: open, 0 comments)
This article gives overviews of the JAXA L2 algorithms and products by Japanese science teams for EarthCARE. The algorithms provide corrected Doppler velocity, cloud particle shape and orientations, microphysics of clouds and aerosols, and radiative fluxes and heating rate. The retrievals by the algorithms are demonstrated and evaluated using NICAM/J-simulator outputs. The JAXA EarthCARE L2 products will bring new scientific knowledge about the clouds, aerosols, radiation and convections.
Abstract
Foehn winds have been a focus of research in mid-latitude mountainous regions for more than 150 years, where their onset is typically associated with warm, dry, and gusty winds. This research has now extended into high latitude regions, yet research of foehn winds in subtropical and tropical regions remains scarce. Here we present results from the first investigation of foehn winds in the subtropics of Southeast Queensland (SEQ), Australia. Analysis of meteorological records found that foehn winds occur throughout the year with peak frequency and duration in late winter (August) associated with the passage of shortwave troughs over southern Australia. Modeling of wind fields and atmospheric boundary layer conditions for three case studies was conducted using the Weather Research and Forecasting (WRF) model. Results showed foehn events in SEQ can be associated with mountain waves and hydraulic jump features in the lee of topographic barriers. Over lee slopes, acceleration of wind speeds and topographic channeling of foehn winds was found to occur, along with substantial increases in air temperature, and decreases in relative humidity. Warming of the foehn airstream is believed to occur primarily through isentropic drawdown with a likely contribution from surface sensible heat flux. Recommendations for future research are made in light of the importance of foehn winds to wildfire management and mitigation in SEQ.
Selecting and weighting dynamical models using data-driven approaches
Pierre Le Bras, Florian Sévellec, Pierre Tandeo, Juan Ruiz, and Pierre Ailliot
Nonlin. Processes Geophys., 31, 303–317, https://doi.org/10.5194/npg-31-303-2024, 2024
The goal of this paper is to weight several dynamic models in order to improve the representativeness of a system. It is illustrated using a set of versions of an idealized model describing the Atlantic Meridional Overturning Circulation. The low-cost method is based on data-driven forecasts. It enables model performance to be evaluated on their dynamics. Taking into account both model performance and codependency, the derived weights outperform benchmarks in reconstructing a model distribution.
Abstract
On days 2023-364 and 2024-034, the Juno spacecraft made close passages of Jupiter's moon Io, at altitudes of about 1,500 km. Data obtained from the first flyby, when the spacecraft was on magnetic field lines connected to both Jupiter and Io, revealed deep flux decreases. In addition, Juno's energetic particle detectors observed tens to hundreds of keV electron and proton beams. Such beams could be generated near Jupiter on field lines associated with Io. The second encounter occurred in the plasma wake and a more modest flux decrease was observed. Furthermore, data from both encounters suggest a spatially extensive decrease in >1 MeV electrons that includes regions inward of Io's orbit. In the immediate vicinity of Io, signatures of absorption likely dominate the data whereas diffusion and wave-particle interactions are expected to be needed to understand MeV electron data in the wider spatial region around Io.
Abstract
Atmospheric rivers (ARs) deliver significant and essential precipitation to the western United States (US) with consequential interannual variability. The intensity and frequency of ARs strongly influence reservoir levels, mountain snowpack, and groundwater recharge, which are key drivers of water-resource availability and natural hazards. Between October 2022 and April 2023, western states experienced exceptionally heavy precipitation from several families of powerful ARs. Using observations of surface-loading deformation from Global Navigation Satellite Systems, we find that terrestrial water-storage gains exceeded 100% of normal within vital California watersheds. Independent water-storage solutions derived from different data-analysis and inversion methods provide an important measure of precision. The sustained storage increases, which we show are closely associated with ARs at daily-to-weekly timescales, alleviated both meteorological and hydrological drought conditions in the region, with a lag in hydrological-drought improvements. Quantifying water-storage recovery associated with extreme precipitation after drought advances understanding of an increasingly variable hydrologic cycle.
Abstract
Local meteorology over the Great Barrier Reef (GBR) can significantly influence ocean temperatures, which in turn impacts coral ecosystems. While El Niño–Southern Oscillation (ENSO) provides insight into the expected synoptic states, it lacks details of anticipated sub-seasonal weather variability at local scales. This study explores the influence of the Madden-Julian oscillation (MJO) on Australian tropical climate, both independently and in combination with ENSO, focusing on GBR impacts. We find that during El Niño periods, including the summer of 2009/10, faster propagating MJO patterns can disrupt background warm, dry conditions, and potentially provide cooling relief via increased cloud cover and stronger winds. In La Niña periods, such as the summer of 2021/22, the MJO tends to be prevented from passing the Maritime continent, forcing it to remain in a standing pattern in the Indian Ocean. This leads to decreased cloud cover and weaker winds over the GBR, generating warm ocean anomalies.
Abstract
Geophysical subsurface characterization plays a key role in the success of geologic carbon sequestration (GCS). While deterministic inversion methods are commonly used due to their computational efficiency, they often fail to adequately quantify the model uncertainty, which is essential for informed decision-making and risk mitigation in GCS projects. In this study, we propose the SVGD-AE method, a novel geostatistical inversion approach that integrates geophysical data with prior geological knowledge to estimate subsurface properties. SVGD-AE combines Stein Variational Gradient Descent (SVGD) for sampling high-dimensional distributions with an autoencoder (AE) neural network for re-parameterizing reservoir models, aiming to accurately preserve geologic characteristics of reservoir models derived from prior knowledge. Through a synthetic example of pre-stack seismic inversion, we demonstrate that the SVGD-AE method outperforms traditional probabilistic methods, particularly in inverse problems with complex posterior distributions. Then, we apply the SVGD-AE method to the Illinois Basin—Decatur Project (IBDP), a large-scale CO2 storage initiative in Decatur, Illinois, USA. The resulting petrophysical models with quantified uncertainty enhance our understanding of subsurface properties and have broad implications for the feasibility, decision making, and long-term safety of CO2 storage at the IBDP.
Abstract
Quantitative understanding of the land water loading is a prerequisite to the construction of reliable tectonic deformation velocity field in the Tibetan Plateau (TP). Here, for the first time, we image the three-dimensional crustal loading deformation velocity field of each land water component in the TP. Our results reveal that the loading signal strength of the six land water components ranks from largest to smallest as groundwater, glacier, lake, soil water, permafrost, and snow, with the maximum vertical velocity close to ±1.60 mm/yr and the maximum horizontal velocity exceeding 0.40 mm/yr. All land water components can achieve a strong enough vertical loading velocity exceeding the present-day Global Positioning System (GPS) velocity at some sites. But for horizontal loading, apparent impacts are only from glacier, lake and groundwater, however, are very limited, with the absolute ratio of loading velocity to GPS velocity being smaller than 5% at almost all the sites.
Abstract
Near-term projections of drought in the southwestern United States (SWUS) are uncertain. The observed decrease in SWUS precipitation since the 1980s and heightened drought conditions since the 2000s have been linked to a cooling sea surface temperature (SST) trend in the Equatorial Pacific. Notably, climate models fail to reproduce these observed SST trends, and they may continue doing so in the future. Here, we assess the sensitivity of SWUS precipitation projections to future SST trends using a Green's function approach. Our findings reveal that a slight redistribution of SST leads to a wetting or drying of the SWUS. A reversal of the observed cooling trend in the Central and East Pacific over the next few decades would lead to a period of wetting in the SWUS. It is critical to consider the impact of possible SST pattern trends on SWUS precipitation trends until we fully trust SST evolution in climate models.
Abstract
To investigate the impact of CO2-rich fluids on compaction behaviors and transport properties in carbonate fault zones, we conducted compaction-coupled fluid flow experiments with CO2-rich fluids percolating precompacted calcite aggregates. Our findings reveal distinct responses among samples subjected to different fluid conditions. Specifically, samples exposed to dry conditions exhibited negligible compaction strain, while those under wet-closed conditions displayed relatively minor strain. In contrast, samples subjected to flow-through conditions demonstrated significant compaction strain, with strain rates higher by 2–3 orders of magnitude than closed conditions due to enhanced pressure solution, subcritical cracking, and chemical dissolution. Strain rate, permeability, and grain size distribution exhibited spontaneous variations in response to fluid flow and compaction. Microstructures and mechanical and transport data suggest that deformation during the initial infiltration of CO2-rich fluids was dominated by subcritical cracking, followed by pressure solution as grain size evolved, which resulted in compaction and reduced permeability. The persistent infiltration of CO2-rich fluids further enhanced inhomogeneous dissolution-precipitation with preferred dissolution channels serving as fluid pathways. The re-precipitations may cement fault rocks and form low permeability seals, resulting in anisotropic fluid flow and localized fluid pressure in fault zones. As applied to nature, our results provide experimental evidence for the evolution of internal structures and transport behaviors, shedding important light on the mechanisms and sealing potential of carbonate faults in response to the infiltration of CO2-rich fluids during the post-seismic and inter-seismic processes.
Abstract
This study presents a recent finding of magnetic shelf structures and packages of whistler-mode waves in the data obtained from the Magnetospheric Multiscale (MMS) mission satellite in the equatorial magnetosphere. These observations are compared with the waves observed on density shelves by the NASA Van Allen Probes (aka RBSP) mission. By employing simulations of the electron-MHD model, we explain that similar to the density shelf ducting, magnetic shelves effectively guide whistler-mode waves along the ambient magnetic field with little attenuation. The parameters of the guided waves depend on the parameters of the shelves. We discuss the similarities and differences of the wave guided by the density and magnetic field shelf-like structures. The simulations successfully reproduce the parameters of the observed waves.
Brief communication: Lessons learned and experiences gained from building up a global survey on societal resilience to changing droughts
Marina Batalini de Macedo, Marcos Roberto Benso, Karina Simone Sass, Eduardo Mario Mendiondo, Greicelene Jesus da Silva, Pedro Gustavo Câmara da Silva, Elisabeth Shrimpton, Tanaya Sarmah, Da Huo, Michael Jacobson, Abdullah Konak, Nazmiye Balta-Ozkan, and Adelaide Cassia Nardocci
Nat. Hazards Earth Syst. Sci., 24, 2165–2173, https://doi.org/10.5194/nhess-24-2165-2024, 2024
With climate change, societies increasingly need to adapt to deal with more severe droughts and the impacts they can have on food production. To make better adaptation decisions, drought resilience indicators can be used. To build these indicators, surveys with experts can be done. However, designing surveys is a costly process that can influence how experts respond. In this communication, we aim to deal with the challenges encountered in the development of surveys to help further research.
The impact of long-term changes in ocean waves and storm surge on coastal shoreline change: a case study of Bass Strait and south-east Australia
Mandana Ghanavati, Ian R. Young, Ebru Kirezci, and Jin Liu
Nat. Hazards Earth Syst. Sci., 24, 2175–2190, https://doi.org/10.5194/nhess-24-2175-2024, 2024
The paper examines the changes in shoreline position of the coast of south-east Australia over a 26-year period to determine whether changes are consistent with observed changes in ocean wave and storm surge climate. The results show that in regions where there have been significant changes in wave energy flux or wave direction, there have also been changes in shoreline position consistent with non-equilibrium longshore drift.
An easy-to-use water vapor sampling approach for stable isotope analysis using affordable membrane valve multi-foil bags
Adrian Dahlmann, John D. Marshall, David Dubbert, Mathias Hoffmann, and Maren Dubbert
Atmos. Meas. Tech. Discuss., https://doi.org/10.5194/amt-2024-43,2024
Preprint under review for AMT (discussion: open, 0 comments)
Water-stable isotopes are commonly used in hydrological and ecological research. Until now, measurements were obtained either destructive or directly in the field. Here, we present a novel, affordable, and easy-to-use approach to measure the stable isotope signatures of soil water. Our gas bag approach demonstrates a high accuracy and extends the usability by allowing water vapor samples to be collected and stored in the field without the need for an instrument or a permanent power supply.
Lidar–radar synergistic method to retrieve ice, supercooled water and mixed-phase cloud properties
Clémantyne Aubry, Julien Delanoë, Silke Groß, Florian Ewald, Frédéric Tridon, Olivier Jourdan, and Guillaume Mioche
Atmos. Meas. Tech., 17, 3863–3881, https://doi.org/10.5194/amt-17-3863-2024, 2024
Radar–lidar synergy is used to retrieve ice, supercooled water and mixed-phase cloud properties, making the most of the radar sensitivity to ice crystals and the lidar sensitivity to supercooled droplets. A first analysis of the output of the algorithm run on the satellite data is compared with in situ data during an airborne Arctic field campaign, giving a mean percent error of 49 % for liquid water content and 75 % for ice water content.
Catchment-scale assessment of drought impact on environmental flow in the Indus Basin, Pakistan
Khalil Ur Rahman, Songhao Shang, Khaled Saeed Balkhair, Hamza Farooq Gabriel, Khan Zaib Jadoon, and Kifayat Zaman
Nat. Hazards Earth Syst. Sci., 24, 2191–2214, https://doi.org/10.5194/nhess-24-2191-2024, 2024
This paper assesses the impact of drought (meteorological drought) on the hydrological alterations in major rivers of the Indus Basin. Threshold regression and range of variability analysis are used to determine the drought severity and times where drought has caused low flows and extreme low flows (identified using indicators of hydrological alterations). Moreover, this study also examines the degree of alterations in river flows due to drought using the hydrological alteration factor.
