We present the first Northern Hemisphere high-resolution Holocene methane (CH4) record obtained from the Renland Ice Cap (ReCAP) – 71.3N 26.6W 2300 m a.s.l. in 2015. The total length of the core is 584 m containing 532 m of the Holocene ice without brittle ice zone thus allowing to obtain an uninterrupted CH4 record over the Holocene. An ice core analytical technique developed in 2010 – continuous flow analysis (CFA) provides a unique opportunity of revealing high-resolution greenhouse gas record of the past. Considering a mean annual layer thickness the depth resolution translates to a nominal temporal resolution of 35 data points 100 yr-1 over the Meghalayan (back to 4.2 ka BP) Holocene section. Note that due to the average residence time of CH4 in the atmosphere and the gas age distribution width in the firn, the maximum temporal effective resolution is lower by a factor of 10. The pattern of the centennial scale variability seen in the ReCAP CH4 record is coherent with the earlier published Southern Hemisphere record based on the West Antarctic Ice Divide (WAIS) CH4 record. The wavelet coherence analysis identifies a high correlation on the long- and midterm variability (600-700, 200-500 yr periodicity) as expected; the Meghalayan Holocene section reveals a common variability down to 70 yr. Inter-laboratory offsets of the absolute CH4 values are likely constant as the entire cores were running over continuing measurement campaigns. The elevated ReCAP CH4 level due to the local dust presence is disproved for at least the Last Glacial section. Gas trapping uncertainties should not matter on a decadal scale besides probable layered bubble trapping. Melt layers are untraceable prior to 2 ka BP due to the annual layers thinning. The analysis was performed on the ReCAP record cleaned from the possible melting- and the CFA technique-related spikes. This study leads, however, to a more detailed evaluation of the interpolar difference in the future work as the absolute value remains unresolved though we are confident that there were no big variations. We argue that the centennial variability in the CH4 is explained by the intertropical convergence zone global teleconnection and its influence on the monsoon activity and thus the CH4 production by tropical wetlands. The duration of the periods in CH4 concentration evolves through the time, which could potentially suggest a change in the atmospheric residence time of CH4.

A document by Jing Wei. Click on the document to view its contents.

We demonstrate scintillation analysis from a network of geodetic Global Positioning System (GPS) receivers which provide data at 1-second resolution. We introduce proxy phase ($\sigma_{TEC}$) and amplitude ($SNR_4$) scintillation indices and validate them against the rate of change of TEC index (ROTI), and $S_4$. Additionally, we validate scintillation observations against a CASES scintillation receiver. We develop receiver dependent scintillation event thresholding using hardware-dependent noise variance. We analyze six-days adjacent to the 7-8 September 2017 geomagnetic storm, using 169 receivers covering magnetic latitudes between 15$^\circ$ and 65$^\circ$ in the American longitude sector. We leverage the available spatial sampling coverage to construct 2-D maps of scintillation and present episodic evolution of scintillation intensifications during the storm. We show that low-latitude and high-latitude scintillation morphology match well-established scintillation climatology patterns. At mid-latitudes, spatiotemporal evolution of scintillation partially agrees with known scintillation patterns. Additionally, the results reveal previously undocumented mid-latitude scintillation producing structures. The results provide an unprecedented view into the spatiotemporal development of scintillation-producing plasma irregularities and provide a resource to further exploit scintillation evolution at large spatial scales.

Large-scale electrical resistivity investigations of the Antarctic crust and upper mantle utilizing the magnetotelluric method (MT) are limited in number compared to temperate regions, but provide physical insights difficult to obtain with other techniques. Key to the method’s success in polar environments are instrumentation advances that allow micro-volt level measurements of the MT electric field in the face of mega-ohm contact resistances. In this presentation, we analyze MT data from four campaigns over the Antarctic interior using modern 3D non-linear inversion analysis and offer additional geophysical conclusions and context beyond the original studies. A profile of MT soundings over transitional Ellsworth-Whitmore block in central West Antarctica implies near-cratonic lithospheric geothermal conditions with interpreted graphite-sulphide horizons deformed along margins of high-grade silicate lithologic blocks. Data across South Pole soundings confirms large-scale low resistivity spanning Moho depths that is consistent with limited seismic tomography and elevated crustal thermal regime inferences. Upper mantle under a presumed adiabatic thermal gradient below the Ross Ice Shelf region of West Antarctica appears to be of a moderately hydrated state but not sufficient so as to induce melting. The degree of hydration there is comparable to that below the north-central Great Basin extensional province of the western U.S. Comprehensive 3D coverage of Mount Erebus and Ross Island reveals unprecedented views of the magmatic plumbing feeding the phonolitic volcanic system. This includes a lower middle crustal staging area for episodic magmatic replenishment of the upper middle crustal chamber hosting phonolitic differentiation, which in turn is fed from an upper mantle source region of the parental basanite.

Foredune growth results predominantly from sand that is blown from the beach and backshore. Predictions of multi-year potential sand supply that are based on time series of wind speed and direction measured at a regional (offshore or coastal) meteorological station, however, often grossly overpredict measured deposition volumes on the foredune. This is commonly ascribed to supply limiting factors, such as beach surface moisture or shell deposits, or to fetch limitations. Here we show that differences between regional and local (i.e., on the beach) wind characteristics can also contribute substantially to this overprediction. Using wind data collected during a five-week field experiment on a Dutch beach backed by a 20-m high, steep (1:2) foredune we found that the wind speed on the beach is lower and that the wind direction on the backshore is more alongshore than expected from the regional wind data. Both the difference in speed and direction were a function of the regional wind direction, with the largest speed reduction (to about 70% of the regional value) for shore-normal winds and the largest alongshore deflection (about 15 degrees) for shore-oblique winds. When these functional dependencies are applied to a 10-year series of regional wind data, we found that the potential annual onshore sand transport at our site, predicted with the aeolian sand transport equation of Hsu (1971), reduces from 86 to 24 m3/m. The latter is now comparable, although still somewhat higher than the measured annual deposition volume of 10 to 15 m3/m. Further analysis of the computations shows that most of this reduction is due to the difference between regional and local wind speed. In future work we will explore how much of the remaining overprediction is due to surface moisture and fetch limitations.

The ionospheric modification experiments are providing the means for understanding mechanisms and physical processes leading to the generation and evolution of ionospheric irregularities. We present experimental results concentrating on the features and evolution, generation conditions and mechanisms of small-scale field-aligned irregularities (FAIs) in the high latitude ionosphere F region induced by the controlled injection of the powerful HF radio waves from the ground into the ionosphere. Experiments have been carried out at the EISCAT HF Heating facility near Tromsø, Norway, at heater frequencies of 4.5 – 8.0 MHz with an effective radiated power of 200 – 750 MW. HF pump wave with ordinary (O-mode) or extraordinary (X-mode) polarization was injected along the magnetic field-aligned direction. Instrument diagnostics included the CUTLASS (Co-operative UK Twin Located Auroral Sounding System) radar, the European Incoherent Scatter (EISCAT) UHF radar at 931 MHz near Tromsø and the EISCAT ionosonde (dynasonde). It was found that the features and physical driving mechanisms of FAIs with the spatial scale across the geomagnetic field of 7.5 – 15 m are significantly different for O- and X-mode HF pumping, presenting challenges for understanding the relevant processes. The main attention is paid to the recently discovered X-mode FAIs. By a contrast to the O-mode FAIs excited by a thermal parametric (resonance) instability at the upper hybrid resonance altitude, the X-mode FAIs are generated via two-step process. In the first step the generation of elongated large-scale irregularities (with the spatial scale across the geomagnetic field of the order of 1 -10 km depending on the background geophysical conditions and the pump frequency) is occurred. As a second step, we suggest that the filamentation instability can be responsible for the generation of small-scale FAIs. As is found from EISCAT UHF radar measurements FAIs greatly impact on the development of strong artificial turbulence such as Langmuir and ion-acoustic plasma waves.

A negative shortwave cloud feedback associated with higher extratropical liquid water content in mixed-phase clouds is a common feature of global warming simulations, and multiple mechanisms have been hypothesized. A set of process-level experiments performed with an idealized global climate model (a dynamical core with passive water and cloud tracers and full Rotstayn-Klein single-moment microphysics) show that the common picture of the liquid water path (LWP) feedback in mixed-phase clouds being controlled by the amount of ice susceptible to phase change is not robust. Dynamic condensate processes—rather than static phase partitioning—directly change with warming, with varied impacts on liquid and ice amounts. Here, three principal mechanisms are responsible for the LWP response, namely higher adiabatic cloud water content, weaker liquid-to-ice conversion through the Bergeron-Findeisen process, and faster melting of ice and snow to rain. Only melting is accompanied by a substantial loss of ice, while the adiabatic cloud water content increase gives rise to a net increase in ice water path (IWP) such that total cloud water also increases without an accompanying decrease in precipitation efficiency. Perturbed parameter experiments with a wide range of climatological LWP and IWP demonstrate a strong dependence of the LWP feedback on the climatological LWP and independence from the climatological IWP and supercooled liquid fraction. This idealized setup allows for a clean isolation of mechanisms and paints a more nuanced picture of the extratropical mixed-phase cloud water feedback than simple phase change.

The nature of the variability of the Total Electron Content (TEC) over Europe is investigated during the 2009 and 2019 Northern Hemisphere (NH) SSW events in this study. As the TEC variability is driven by geomagnetic and lower atmospheric forcing mechanisms, we investigate the dominant drivers and their respective contributions to TEC changes during both SSW events. We simulate the SSWs using the Whole Atmosphere Community Climate Model eXtended version (WACCM-X) and compare the semidiurnal solar and lunar tidal variabilities in the mesosphere-lower thermosphere (MLT) region. Further, in order to assess the mechanisms responsible for the TEC variability during both SSWs, we run numerical experiments using the National Center for Atmospheric Research (NCAR) Thermosphere-Ionosphere Electrodynamics General Circulation Model (TIE-GCM). We constrain the TIE-GCM lower boundary with the WACCM-X fields and carry out simulations both with and without geomagnetic forcing for each of the SSWs. The TIE-GCM simulations allow us to isolate the geomagnetic and lower atmospheric forcing effects on the TEC. We find that there was a major enhancement in daytime TEC over Europe during the 2019 SSW event, which was predominantly geomagnetically forced (~80%), while for the 2009 SSW, the major variability in TEC was accounted for by lower atmospheric forcing.

Forecasting hydroclimatic extremes holds significant importance considering the increasing trends in natural cascading climate-induced hazards such as wildfires, floods, and droughts. This study evaluates the performance of five Copernicus Climate Change Service (C3S) seasonal forecast models (i.e., CMCC, DWD, ECCC, UK-Met, and Météo-France) in predicting extreme precipitation events from 1993 to 2016 using 28 extreme precipitation indices reflecting timing and intensity of precipitation in a seasonal timescale. We design indices using various precipitation thresholds to reflect model skill in capturing the distribution and intensity of precipitation over a season. We use percentage bias, the Kendall Tau rank correlation, and ROC scores for skill evaluation. We introduce an impact-based framework to evaluate model skill in capturing extreme events over regions prone to natural disasters such as floods and wildfires. The performance of models varies across regions and seasons. The model skill is highlighted primarily in the tropical and inter-tropical regions, while skill in extra-tropical regions is markedly lower. Elevated precipitation thresholds correlate with heightened model bias, revealing deficiencies in modelling severe precipitation events. The impact-based framework analysis highlights the superior predictive capabilities of the UK-Met and Météo-France models for extreme event forecasting across many regions and seasons. In contrast, other models exhibit strong performance in specific regions and seasons. These results advance our understanding of an impact-based framework in capturing a broad spectrum of extreme climatic events through the strategic amalgamation of diverse models across different regions and seasons, offering valuable insights for disaster management and risk analysis.

A document by Xianwei Wang. Click on the document to view its contents.

Black carbon (BC), organic carbon (OC) and dust (or Absorbing Aerosols - AA) strongly absorb visible solar radiation, leading to impacts on the atmospheric radiation budget, climate, water cycle, and more. Recent attempts have been made to elucidate the spatial-temporal concentrations and radiative forcing of AA over East Asia using the UV band OMAERUV product from OMI. The product provides global coverage of AAOD in the UV bands, limiting the results to where retrievals can be made, and to cases where the average aerosol size is not too small. For these reasons, this approach cannot estimate the magnitude of total AAOD and/or radiative forcing. To achieve this, we include relevant data from multiple bands in the visible and NIR in tandem with the UV, so that a more complete relationship can be made to understand the magnitude and properties of AA globally. We employ a MIE model to simulate the absorption of core-shell coated mixtures of AA (specifically a mixture of BC core with sulfate shell (MBS) and OC core with sulfate shell (MOS) across multiple individual wavelengths. These values are then merged with individual inversions of SSA from AERONET at each individual wavelength across the spectrum from the UV through the NIR. Fitting is done based on the temporally varying magnitude band of the measured AOD and the inverted SSA incorporating all individual data points where both calculations exist at each station, from 2010 to 2016. The relationship between core and shell sizes that is consistent with AERONET is then fitted to OMI measurements that overlap AERONET in space and time. A sensitivity matrix of optical uncertainties is made to compute the robustness of the constrained aerosol size, chemical composition and refractive indices. Initial results show that retrieved aerosol properties of MBS and MOS are consistent with known properties over urban areas, biomass burning areas, and those regions frequently impacted by long-range transport events, as observed over Asia. A few interesting scientific findings include mixing between these different sources and detection of otherwise missing sources. It is hoped that ongoing calculations allowing our approximation to be extended spatially away from sites where AERONET measurements exist will also be ready to present.

Processes and timescales of magmas: U-series, 40Ar/39Ar chronology, and ternary feldspars, for the Quaternary Suswa volcano, Central Kenya Peralkaline Province, East African Rift Vanessa V. Espejel-García a, Elizabeth Y. Anthony b, Peter A. Omenda c, Alan L. Deino d, John C. White e a Facultad de Ingeniería, Universidad Autónoma de Chihuahua, Circuito No. 1, Campus Universitario 2, C.P. 31125, Chihuahua, Chih., México. b University of Texas at El Paso, El Paso, TX 79968, USA c Scientific and Engineering Power Consultants, P.0. Box 38991, Nairobi, Kenya d Berkeley Geochronology Center, Ridge Road, Berkeley, CA, 94709, USA. e Eastern Kentucky University, Richmond, KY 40475, USA Corresponding author. Vanessa V. Espejel-García, [email protected], Tel. (52) 614 221 7549. ORCID a 0000-0002-0486-8726 b 0000-0001-7951-1724 c —- d 0000-0002-0099-9382 e 0000-0001-5107-6847 Suswa is a Late Pleistocene to recent volcano in the axis of the East African Rift. Early activity saw construction of a trachytic shield volcano, followed by mafic-felsic magma mixing, explosive volcanism, and caldera collapse. Recent activity includes drawn down of the magma chamber to create a second, inner caldera, a resurgent dome, and eruption of phonolites (White et al., 2012, Lithos, 152, 88-104). 40Ar/39Ar ages for the initial shield volcano are ca. 110 ka. Formation of the outer caldera occurred at ca. 46 ka, and initial post-caldera eruptions followed soon thereafter at 32.5 ka. Final eruptions are ca. 11 ka to “zero age”. 230Th/232Th confirms simultaneity of mafic eruptions in the peripheral fields and the youthfulness of the final events. The 203Th/232Th data also demonstrate that depth for initial magma generation lies below the spinel peridotite field within garnet peridotite. Ground deformation includes deflation of 4.6 cm from 1997 to 2000 (Biggs et al., 2009) and subsequent inflation of 4.3 +/- 0.8 cm/yr from 2015 to 2020 (Albino and Biggs, 2021, G3). Alkali feldspar from pre- and most syn-caldera has a limited compositional range. Feldspars in mingled lavas include bimodal distribution of these alkali feldspar and plagioclase identical in composition to similar-age cinder cones and fissure flows adjacent to the volcano. Alkali feldspar shifts to greater An content in the post-caldera phonolite. Oscillatory and tabular textures record rapid crystal growth and turbulence in the phonolite magma chamber. However, neither the textures nor the composition range necessitate renewed addition of mafic material.

A document by Rowan Alethea Dayton-Oxland. Click on the document to view its contents.

The planetary boundary layer (PBL) is a layer in the lowest part of the atmosphere where Earth’s surface strongly influences temperature, moisture, and wind through the turbulent transfer of air mass. It is a key component of air pollution transport studies. An urban heat island (UHI) is a metropolitan area which is significantly warmer than its surrounding rural areas. The El Paso - Juarez Metropolitan area, with a combined population of ~ 1.972 million (in 2010) and growing urban infrastructure, can be studied as an UHI surrounded by rural areas. In this study, we have analyzed the temperature fields for the lower levels of the troposphere for the El Paso - Juarez metropolitan area and neighboring rural areas during the day and night hours both for the summer and winter seasons. The Vaisala Boundary Layer View Software (BLView) was used to obtain the aerosol mixing layer height (ML), a proxy for the PBL height, using data from a Vaisala ceilometer, model CL31. The ceilometer is situated at the University of Texas at El Paso (UTEP) campus. The BLView analyzes the ceilometer backscatter profile data and provided the ML structure. In addition, the Weather Research Forecast Model (WRF) was used to simulate PBL heights for the El Paso - Juarez Airshed and its surrounding rural areas. The overall objective of the project is to contribute to a better understanding of the PBL structure and the effect the UHI has for the El Paso - Juarez Airshed.

Predicting the thermal performance of an enhanced geothermal system (EGS) requires a comprehensive characterization of the underlying fracture flow patterns from practically available data such as tracer data. However, due to the inherent complexities of subsurface fractures and the generally insufficient geological/geophysical data, interpreting tracer data for fracture flow characterization and thermal prediction remains a challenging task. The present study aims to tackle the challenge by leveraging a data assimilation method to maximize the utilization of information inherently contained in tracer data, and meanwhile maintain the flexibility to handle various uncertainties. A tracer data interpretation framework was proposed with the following three components integrated: 1) We use principal component analysis (PCA) to reduce the dimensionality of model parameter space. 2) We use ES-MDA (ensemble smoother with multiple data assimilation) to invert for fracture aperture/flow fields and obtain posterior model ensembles for uncertainty quantification. Various data types are assimilated jointly to improve the predictive ability of the posterior ensemble. 3) The inverted fracture aperture fields are then incorporated into reservoir models to predict thermal performance. We developed a field-scale EGS model to verify the ability of the framework to characterize highly heterogeneous fracture aperture/flow fields and predicting thermal performance. We also applied the framework to a meso-scale field experiment to demonstrate its potential application in real-world geothermal reservoirs. The results indicate that the proposed framework can effectively retrieve fracture flow information from tracer data for thermal prediction and uncertainty quantification, and thus provide informative guidance for EGS optimization and risk management.

Midstream oil and gas infrastructure comprises vast networks of gathering and transmission pipelines that connect upstream extraction sites to downstream processors, exporters, and consumers. In the United States (US), public policies and corporate decisions continue to promote the extraction and consumption of oil and gas, and they have prompted a wave of proposals for gathering and transmission pipelines in recent years. The ongoing build-out of midstream infrastructure calls for close scrutiny of associated human health risks and related societal impacts. Urgency is warranted considering that at least part of this infrastructure, the US natural gas pipeline network, is concentrated more heavily in areas of high social vulnerability than areas of low social vulnerability, highlighting inequity in the distribution of societal harms. Emerging research on ways in which midstream pipelines affect Indigenous peoples and rural communities in the US demonstrates the complex nature of potential harms. The spatial distribution of midstream infrastructure, together with the complexity of societal impacts underscore the need to clearly understand and carefully consider these impacts during infrastructure planning and permitting. We offer recommendations for scientists and decision-makers who are interested in evaluating these impacts through the lens of environmental justice.

We propose a new nonparametric approach for assessing future changes in annual stream flows in extreme drought years based on an ensemble of climate projections. We apply the method to the Potomac River basin, investigating whether future flows in the river may be impacted by “hot drought”, that is, increasing severity of hydrological drought caused by rising temperatures coupled with variability in precipitation. Long time series representative of annual climate in time periods of interest are constructed by pooling and concatenating shorter time series sampled from an ensemble of bias corrected and spatially downscaled climate projections, where the K-nearest neighbor method is used to select pool members. The pooled time series are of sufficient length to allow estimation of the probability distribution of a full range of future annual flows, including 1st percentile values, indicative of flow in an extreme drought year. An empirically derived climate response function for annual mean flow is used as this study’s simple hydrologic model. The resulting set of cumulative probability distributions can be used to compute scaling factors for future annual Potomac River flow which demonstrate the disparate impacts of climate change on high flow, average flow, and low flow years. For most scenarios considered, results indicate that though long-term mean precipitation and river flow will increase modestly in future years, annual flows in an extreme drought year will decrease. This new approach can provide multi-model consensus inputs for water supply planning models to support decision-making regarding new infrastructure for climate resilience.

The rainfall-runoff model is essential to derive a relationship between Rainfall and Runoff, in which the hydrological response of the catchment can be derived. A real case study is chosen to simulate the rainfall-runoff modeling, in which small urban catchments are selected and are located in the center part of Vizianagaram Town. The present case study aims to develop an event-based rainfall-runoff model for upstream and downstream catchments of peddacheruvu catchment (PC). In this study, Cartosat-10mDEM, Hourly rainfall data are taken from (weather station), i.e., 1st July to 30th September, the Maximum and Minimum Infiltration rates, Evaporation data, soil data, Groundwater parameters, and dry weather flow patterns are used as in input for model simulation to know the wet weather flow and dry weather flow quantity contributing from the catchment. The model simulation is carried out by using the stormwater management model i.e., PC-SWMM version 5.7.1868. The model simulation is performed at two outlet points in the catchment. The upstream and downstream catchments are selected for computing the total runoff hydrographs. The model calibration is done for nine selected streamflow events from 1st July to 31st August 2019, and the remaining three streamflow events are chosen from 1st to 30th September 2019 are set for model validation. The model performance was checked by computing nine goodness of fit measures. The results of this study suggest that simulated runoff values have satisfactory results with the observed streamflow. In recent years, understanding the hydrological modeling and process has become more important in water resource management, especially in analyzing extreme hydrological events like floods or droughts. The availability of metrological and hydrological data is often scarce in a semi-urban catchment. Some of the significant issues are associated with obtaining reliable long-term hydrological data in the semi-urban region. This study investigates the performance of event-based modeling for data-scarce semi-urban catchments using PC-SWMM in computing the total runoff hydrograph. A real case study, i.e., Peddacheruvu (PC) Upstream and Downstream catchment, were selected, and model performance was examined using 12 streamflow events from 1 July 2019 to 31 September 2019. The model performances are evaluated using five goodness of fit measures like root mean square error (RMSE), Nash Sutcliffe efficiency (NSE), coefficient of determination (R2), RSR, and Kling Gupta efficiency (KGE). The model performance is acceptable throughout model calibration (1 July to 31 August 2019) as the NSE and R2 varies between 0.75 to 0.77 and 0.76 to 0.78, respectively. Similarly, the model validation performances (1 September to 31 September 2019) revealed best fitted with the observed hydrograph for NSE and R2 were 0.62 to 0.64 and 0.62 to 0.85. KGE for model calibration and validation model varies between 0.65 to 0.75 and 0.62 to 0.75.