Peatlands are becoming recognized as important carbon sequestration centers where, through restoration projects, peatlands may stop being considered as carbon sources and become carbon neutral or possibly carbon negative. Restoration projects require a knowledge of intra-peat variation across these, sometimes, vast areas. The integration of multidimensional geophysical tools, digital elevation models and satellite remote sensing products combined with modern data analytic techniques may provide a rapid means of accessing variations over broad spatial scale. In this study an airborne radiometric survey, being flown nationally over the Republic of Ireland, is shown to be able to delineate potential management zones within an industrial raised peat bog. Radiometric data is particularly suited to peat studies as they are sensitive to water content. Peat, as a mostly organic material, acts as a low signal environment where variations in the signal are linked to intra-peat variation of either depth or water content. This study uses an unsupervised, self-organizing map clustering methodology to group the radiometric signal into three zones interpreted as 1) the edge of the bog where peat layer is thinning and there is influence on the radiometric signal from non-peat soils outside of the bog, 2) the normal peat conditions where depth and saturation appear as a relative constant in the radiometric response and 3) areas where the peat is either thinner, drier, or potentially somewhat mineralised. The addition of other data layers such as elevation, slope and satellite imagery may help better define these zones and a ground geophysical survey is planned to test the results of this study. The definition of such potential management zones could aid any restoration project in the initial stages or act as a baseline study to monitor changes to the peatland during and after a restoration project is complete.

This study examines the occurrence of riparian lenses adjacent to partially penetrating rivers under the controlled conditions of a laboratory sand tank. Laboratory experiments and numerical modeling of the freshwater lens extent are used to provide physical verification (in light of limited examples of well-characterized field cases) of the analytical methodology, thereby evaluating the underlying assumptions. Parameter calibration and uncertainty analysis are applied to assess both the experimental conditions and the benefit of lens observations in applying the analytical approach. The experimental freshwater lens was reproduced by both analytical and numerical models, with the exception of small mismatches (between analytical results and measured data) in the lens thickness in the near-river region. These are most likely due to vertical flow effects that arise from the partial river penetration and saltwater inflows to the river bottom, and that are only partly accounted for in the analytical approach. Uncertainty analysis highlighted that accurate lens predictions based on the analytical method requires calibration to direct lens measurements; a similar finding from earlier studies of fully penetrating river conditions. Sensitivity analysis highlighted that the saltwater head boundary, freshwater and saltwater densities, and the aquifer depth below the riverbed (in descending order of sensitivity) are lthe most important factors in controlling freshwater lens occurrence and saltwater discharge. The results provide the first physical verification of the occurrence of stable riparian lenses adjacent to partially penetrating, gaining rivers, and verify a recent analytical solution for lens extent and saltwater discharge.

2D thermospheric wind fields, at both E- and F-region altitudes within a common vertical volume, were made using a Scanning Doppler Imager (SDI) at Poker Flat, Alaska, during a substorm event. Coinciding with these observations were F-region plasma velocity measurements from the Super Dual Auroral Radar Network (SuperDARN), and estimations of the total downward and upward field-aligned current density from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). This combination of instruments gives an excellent opportunity to examine the spatial characteristics of high latitude ionosphere-thermosphere coupling, and how a process which is triggered in the magnetosphere (the substorm) affects that coupling at different altitudes. We find that during the substorm growth phase, the F-region thermospheric winds respond readily to an expanding ionospheric plasma convection pattern, whilst the E-region winds appear to take a much longer period of time. The differing response timescales of the E- and F-region winds is likely due to differences in neutral density at those altitudes, resulting in E-region neutrals being much more ‘sluggish’ with regards to ion-drag. We also observe increases in the F-region neutral temperature, associated with neutral winds accelerating during both substorm growth and recovery phases.

Recent studies of anthropogenically induced seismicity have improved our understanding of the causal relationships between earthquakes and industrial activity. Whether larger-magnitude earthquakes can be triggered and how human injection and production of fluids interact with active faults remain poorly understood. The 2017 Mw 6.5 Leyte earthquake nucleated at a depth near the production zone and within 1 km of an actively producing geothermal field in the Philippines. We use satellite radar data to constrain the pre-earthquake ground deformation across the field and the Leyte fault and to determine the coseismic source parameters. From consideration of regional historical seismicity and fluid extraction model constrained by fluid injection and extraction rates, we find evidence suggesting that the mainshock is directly associated with the geothermal production efforts. Our findings demonstrate that the extraction of geothermal power close to active fault zones is capable of triggering damaging earthquakes, a hazard that was previously underappreciated.

Using a reduced-gravity model, this study explores the ocean’s response to wind forcing in the South-East Tropical Indian Ocean (SETIO) during the development phase (July-September) of positive phases of the Indian Ocean Dipole (IOD), using the years of 2009 and 2019 for comparison. Findings show that IOD variability is exclusively controlled by zonal equatorial wind anomalies. In the average situation, represented by the 2009 season, westerly equatorial winds create downwelling Kelvin waves that operate to suppress the Sumatran upwelling. In contrast, positive phases of the IOD, represented by the 2019 season, are characterized by easterly equatorial winds that reverse the equatorial influence, which leads to strong coastal upwelling off Sumatra’s southeast coast. In addition, findings show that the Sumatran upwelling involves the formation of a strong northwestward surface flow, the South-East Sumatra Current, that transports colder seawater into the region, which contributes to the IOD anomaly.

Worldwide, the fisheries sector is growing with improved technologies to meet the ever-growing demand for seafood. However, with climate change and increasing marine pollution, there are also significant concerns about declining biodiversity and its impact on income and livelihoods for small-scale fishers. There is a significant shift from traditional fishing methods to mechanization and aquaculture in India. However, the new alternatives have come with many downsides which often go unnoticed. Mechanized fishing contributes to GHGs emissions, destruction of the seabed, overexploitation, and disrupting the ocean food chain. Likewise, coastal aquaculture emits GHGs during feed production, discharges organic and inorganic wastes, involves LULC changes and destroys ecologically sensitive areas (ESAs), leading to loss of various ecosystem services that increase environmental vulnerability and leads to higher ecological footprint. The impacts of climate change on the fishing sector and coastal areas are well established. However, there is a need to understand the impact of changes in fishing techniques on coastal zones and climate change. In this paper, the changes in the fishing sector are evaluated, followed by the development of a framework to assess the impacts of those changes on coastal zones and climate change. The changes in commercial fishing techniques are assessed by determining the dominant fishing techniques prevailing across India, along with reasons for a shift from traditional methods. A Life-Cycle Cost Assessment (LCCA) of the dominant techniques, aquaculture and mechanized fishing, helped to verify the need for such a shift. Two case study areas are selected for sample data collection for computing LCCA of aquaculture and mechanized fishing - Worli in Mumbai and Bhimavaram in Andhra Pradesh for studying mechanized fishing and aquaculture respectively. LCCA of the dominant techniques against traditional techniques showed that economic viability is one of the major reasons for the shift, which was later confirmed during the interviews with fishermen. These methods though profitable have various impacts on coastal ecosystems and emit GHGs making them unsustainable. The paper develops a framework to categorize the impacts of these changes on coastal zones and climate change and suggests appropriate methods to compute those impacts.

Accurate precipitation monitoring is crucial for understanding climate change and rainfall-driven hazards at a local scale. However, the current suite of monitoring approaches have different insufficiencies, including low spatial and temporal resolutions, and the inability to monitor potentially destructive precipitation events such as hailstorms. In this study, we develop an array-based solution to monitor rainfall with seismic nodal stations, offering both high spatial and high temporal resolutions. We analyze seismic records from densely spaced, high-frequency seismometers in Oklahoma, and identify signals from all 9 precipitation events that occurred during the one-month station deployment in 2016. After removing anthropogenic noise and Earth structure response, the obtained precipitation spatial pattern mimics the one from an operational weather radar, while offering higher spatial and temporal resolutions. We further show the potential of this approach to monitor hail with joint analysis of seismic intensity and independent precipitation rate measurements, and advocate for coordinated seismological-meteorological field campaign design.

Himalaya is one of the most seismically active and earthquake-prone regions of the world. Recently an Earthquake Early Warning System (EEWS) for Northern India has been developed which includes around 165 strong ground motion accelerometers installed in Uttarakhand (India). A timely earthquake early warning of few seconds can save people’s lives and thus the development of an improved Warning Dissemination System (WDS) component of EEWS is much required. For this purpose, an improved WDS has been developed. This system currently uses newly designed low-cost public sirens and smartphone apps to alert people in case of an earthquake. The developed sirens have been currently installed in two major cities of Uttarakhand (India) and in all district emergency operations centers for the last 2 years. On 4th August 2021, the newly developed app “Uttarakhand Bhookamp Alert” for WDS has been officially launched by the Uttarakhand State Disaster Management Authority for operational use. Further, a GIS-based maintenance system is also developed for the maintenance of the complete system, which automatically checks the health and keeps records of the sirens along with the smartphone users. This app gives the facility to the users for sharing their current location with disaster rescue teams after the earthquake early warning alert. Detailed scientific principles and working mechanism of newly developed dissemination system along with its applicability to disseminate the real-time information in case of an earthquake will be presented.

A short watercolor comic about the broken connection between humans and mountains. Funded by Sharing Science grants of the AGU, 2021.

We use Interferometric Synthetic Aperture Radar (InSAR) data collected by the Sentinel-1 mission to study the co- and postseismic deformation due to the 2017 Mw 7.3 Sarpol-e Zahab earthquake that occurred near the Iran-Iraq border in Northwest Zagros. We find that most of the coseismic moment release is between 15 and 21 km depth, well beneath the boundary between the sedimentary cover and underlying basement. Data from four satellite tracks reveal robust postseismic deformation during ~ 12 months after the mainshock (from November 2017 to December 2018). Kinematic inversions show that the observed postseismic InSAR LOS displacements are well explained by oblique (thrust + dextral) afterslip both updip and downdip of the coseismic peak slip area. The dip angle of the shallow afterslip fault plane is found to be significantly smaller than that of the coseismic rupture, corresponding to a shallowly dipping detachment located near the base of the sediments or within the basement, depending on the thickness of the sedimentary cover, which is not well constrained over the epicentral area. Aftershocks during the same time period exhibit a similar temporal evolution as the InSAR time series, with most of aftershocks being located within and around the area of maximum surface deformation. The postseismic deformation data are consistent with stress-driven afterslip models, assuming that the afterslip evolution is governed by rate-strengthening friction. The inferred frictional properties updip and downdip of the coseismic rupture are significantly different, which likely reflect differences in fault zone material at different depths along the Zagros.

Our limited understanding of millennial-scale variability in the context of the last glacial period can be explained by the lack of a reliable modelling framework to study abrupt climate changes under realistic glacial backgrounds. In this article, we describe a new set of long-run Last Glacial Maximum experiments where such climate shifts were triggered by different snapshots of ice-sheet meltwater derived from the early stages of the last deglaciation. Depending on the location and the magnitude of the forcing, we observe three distinct dynamical regimes and highlight a subtle window of opportunity where the climate can sustain oscillations between cold and warm modes. We identify the European-Arctic and Nordic Seas regions as being most sensitive to meltwater discharge in the context of switching to a cold mode, compared to freshwater fluxes from the Laurentide ice sheets. These cold climates follow a consistent pattern in temperature, sea ice and convection, and are largely independent from freshwater release as a result of effective AMOC collapse. Warm modes, on the other hand, show more complexity in their response to the regional pattern of the meltwater input, and within them, we observe significant differences linked to the reorganisation of deep water formation sites and the subpolar gyre. Broadly, the main characteristics of the oscillations, obtained under full-glacial conditions with realistically low meltwater discharge, are comparable to δ18O records of the last glacial period, although our simplified experiment design prevents detailed conclusions from being drawn on whether these represent actual Dansgaard-Oeschger events.

Oceanic transform faults are intriguing in that they do not produce earthquakes as large as might be expected given their dimensions. We use 1-year of local seismicity recorded on an array of ocean bottom seismometers (OBS) and geophysical data to study the seismotectonic properties of the Chain transform, located in the equatorial Mid-Atlantic. We extend our analysis back in time by considering stronger earthquakes (MW ≥ 5.0) from global catalogs. We divide Chain into three areas (eastern, central, and western) based on multi-dimensional OBS seismicity cluster analysis. Seismic activity recorded by the OBS is the highest at the eastern area of Chain where there is a lozenge shaped topographic high, a negative rMBA gravity anomaly, and only a few historical MW ≥ 5.5 events. OBS seismicity rates are lower in the western and central areas. However, these areas accommodate the majority of seismic moment release, as inferred from both OBS and historical data. We find no evidence of remote dynamic triggering and only weak evidence of tidal and static stress triggering. Higher b-values are significantly correlated with lower rMBA and also with shallower bathymetry, potentially related to thickened crust. Our results suggest high lateral heterogeneity along Chain: Patches with moderate to low OBS seismicity rates that occasionally host MW ≥ 6.0 earthquakes are interrupted by segments with abundant OBS activity but few historical events with 5.5 ≤ MW < 6.0. This segmentation is possibly due to variable fluid circulation and alteration, which may also be variable in time.

To capture the effects of mesoscale turbulent eddies, coarse-resolution Eulerian ocean models resort to tracer diffusion parameterizations. Likewise, the effect of eddy dispersion needs to be parameterized when computing Lagrangian pathways using coarse flow fields. Dispersion in Lagrangian simulations is traditionally parameterized by random walks, equivalent to diffusion in Eulerian models. Beyond random walks, there is a hierarchy of stochastic parameterizations, where stochastic perturbations are added to Lagrangian particle velocities, accelerations, or hyper-accelerations. These parameterizations are referred to as the 1st, 2nd and 3rd order ‘Markov models’ (Markov-N), respectively. Most previous studies investigate these parameterizations in two-dimensional setups, often restricted to the ocean surface. On the other hand, the few studies that investigated Lagrangian dispersion parameterizations in three dimensions, where dispersion is largely restricted to neutrally buoyant surfaces, have focused only on random walk (Markov-0) dispersion. Here, we present a three-dimensional isoneutral formulation of the Markov-1 model. We also implement an anisotropic, shear-dependent formulation of random walk dispersion, originally formulated as a Eulerian diffusion parameterization. Random walk dispersion and Markov-1 are compared using an idealized setup as well as more realistic coarse and coarsened (50 km) ocean model output. While random walk dispersion and Markov-1 produce similar particle distributions over time when using our ocean model output, Markov-1 yields Lagrangian trajectories that better resemble trajectories from eddy-resolving simulations. Markov-1 also yields a smaller spurious dianeutral flux.

Urbanization manifests rainfall anomalies both in and around the city. While prior studies have assessed the effect of urban expansion as well as city size, little is known about the impact of city shape on rainfall. Here, idealized large eddy simulations (LES) coupled with the Weather Research and Forecasting (WRF) model are conducted to bridge the knowledge gap. Results indicate difference in the timing for urban-induced rainfall in the inland versus coastal environment. This is associated with contrasting diurnal cycles of vertical velocity and cloud water mixing ratio driven by the land-sea breeze. The impact of city shape on rainfall is more evident in the coastal environment, as buoyancy flows arise from cities alter the interactions between urban-rural circulation and sea breeze. A circular city show nearly 22.0% larger rainfall accumulation and 78.6% greater rainfall intensity compared to a triangular city over urban surfaces. Results highlight the need for considering city shape for coastal urban planning, as a potential adaptation strategy to manage rainfall under future climate. Results indicate that coarser models which represent impervious surface area but not the right shape would have a higher uncertainty in simulating rainfall changes.

Extratropical low-level mixed-phase clouds (MPCs) are difficult to represent in global climate models and generate substantial uncertainty in global climate projections. In this study we evaluate the simulated properties of Southern Ocean (SO) boundary layer MPCs for August 2016 in the ICOsahedral Nonhydrostatic (ICON) model. The bulk of the simulations are part of the DYnamics of the Atmospheric general circulation Modeled On Non-hydrostatic Domain (DYAMOND) initiative. The analysis shows that previous and current versions of ICON overestimate cloud ice occurrence in low-level clouds across all latitudes in the SO. Furthermore, cloud seeding from upper-level ice clouds into low-level supercooled liquid layers is found to strongly impact MPC occurrence in ICON. Like many other global climate models, ICON underestimates the reflectivity of SO boundary layer clouds. We can show that this effect is resolution dependent and largely due to an underestimation in cloud fraction, rather than optical depth. Additional sensitivity experiments show a pronounced sensitivity of the Wegener-Bergeron Findeisen (WBF) process with respect to temporal discretisation. Long integration intervals overestimate WBF growth due to the artificially prolonged co-existence of ice and water within the MPC regime. Furthermore, grid-imposed phase homogeneity will likely yield an overestimation in WBF growth rates in simulations performed at the scale of traditional climate models and likely at the convection-permitting scale also. In addition, WBF growth is likely overestimated due to the high bias in low-level cloud ice occurrence. Changes with respect to cloud ice detrainment from shallow convection are of secondary importance for SO MPC statistics.

Please kindly refer to the accepted version in the journal GMD (https://doi.org/10.5194/gmd-2024-38).Irrigated cultivation, as a prevalent anthropogenic activity, exerts a significant influence on land use and land cover, resulting in notable modifications to land-atmosphere interaction and the hydrological cycle. Given the extensive cropland, high productivity, compact rotation, semi-arid climate, intense irrigation, and groundwater depletion in the North China Plain (NCP), the development of a comprehensive crop-irrigation-groundwater model becomes imperative for understanding agricultural-induced climate response in this region. This study presents an integrated crop model explicitly tailored to the NCP, which incorporates double-cropping rotation, irrigation practice, and groundwater interactions into the regional climate model. The modifications are implemented to: (1) enable a seamless transition from field scale application to regional scale application, facilitating the incorporation of spatial variability, (2) capture the distinctive attributes of the NCP region, ensuring the model accurately reflects its unique characteristics, and (3) reinforce the direct interaction among crop-related variables, thereby enhancing the model’s capacity to simulate their dynamic behaviors. The integrated crop modeling system demonstrates a commendable performance in crop simulations using climatic conditions, which is substantiated by its identification of crop stages, estimation of field biomass, prediction of crop yield, and finally the projection of monthly leaf area index. In our next phase, this integrated crop modeling system will be employed in long-term simulations to enhance our understanding of the intricate relationship between agricultural development and climate change.

A document by Vivian Lynn Turner. Click on the document to view its contents.

In this paper, we present the variations of IMF-Bz, Solar wind Parameters (Vsw, Nsw, and Psw), and Geomagnetic Indices (AE and SYM-H), and the variation of Vertical Total Electron Content (VTEC) using simultaneous VTEC data from 12 GPS-TEC stations over the Indian, Australian, Brazilian and South African regions. We describe contrast in Total Electron Content (TEC) throughout the globe using global ionospheric maps at regular 2-hour interval of UT during the three intense geomagnetic storms. Moreover, we observed that heavily TEC influenced areas were found to be transposing through equatorial plane starting from eastern sectors to the western sectors. Indian Ocean, Atlantic Ocean and South Pacific Ocean sectors were affected flowingly. Global Ionospheric Maps evince that Indian and Brazilian sectors were affected heavily explaining the TID and Equatorial Anomaly as seen on those areas. The equatorial and low-latitude regions have been mainly affected by the geomagnetic storms. All these results suggested that the acute disruption of global winds (surging towards the equator from higher latitudes) and electric fields commenced from magnetosphere-ionosphere interaction cause the severe modification in the equatorial, low-latitude region. We checked the cross correlation during the period of high solar and geomagnetic activities; the correlation gradually increased with the near by stations by latitudes in most of the cases which was another intriguing result. the storms were affected globally which is why we believe that variation of TEC over various stations of the globe could turn out to be very helpful in predicting solar wind coupling with magnetosphere-ionospehere.