Inspired by Comrie (2021), we discuss a few issues related to dust storms and Coccidioidomycosis (Valley fever). There is inconsistency in the term “dust storm” as used by science communities, and the dust data from NOAA Storm Events Database are from diverse sources, unsuitable for assessing dust-Coccidioidomycosis relationships. Population exposure to dust or Coccidioides needs to consider the frequency, magnitude, duration, and spatial coverage of dust events. Given abundant evidence that dust storms are a viable driver to transport Coccidioides, it is in best public interest to advocate that dust storms may put people at risk for contracting Valley fever.

The St. Lawrence Estuary connects the Great Lakes with the Atlantic Ocean. During summer, the Estuary’s surface layer receives its nutrient supply from vertical mixing processes caused by the estuarine circulation and tidal-upwelling at the Head of the Laurentian Channel (HLC). There has been few oceanographic process studies during winter when ice forms and flows on the surface. Winter monitoring is typically confined to vertical profiles of salinity and temperature and near-surface water samples collected from a helicopter. In 2018, however, the Canadian Coast Guard approved a science team to sample in tandem with its icebreaking and ship escorting operations. This opportunistic sampling provided the first winter turbulence observations, which covered the largest spatial extent ever measured during any season within the St. Lawrence Estuary and Gulf. The nitrate enrichment from tidal mixing resulted in an upward nitrate flux of about 30 nmol m$^{-2}$s$^{-1}$, comparable to summer values obtained at the same tidal phase. Further downstream, deep nutrient-rich water from the Gulf was mixed into the subsurface nutrient-poor layer at a rate more than an order of magnitude smaller than at the HLC. These fluxes were compared to the nutrient load of the upstream St. Lawrence River. Contrary to previous assumptions, fluvial nitrate inputs are the most significant source of nitrate in the Estuary. Nitrate loads from vertical mixing processes would only exceed those from fluvial sources at the end of summer when fluvial inputs reach their annual minimum.

Accurate photoionization rates are vital for the study and understanding of planetary ionospheres. Previous model calculations of terrestrial photoionization rates lack sufficient spectral resolution to account for highly structured photoionization cross sections as well as the solar spectral irradiance. We present new photoionization rate calculations from CPI’s Atmospheric Ultraviolet Radiance Integrated Code [AURIC; Strickland et al., 1999] using high-resolution (0.01 Å) solar spectra and high-resolution (0.01 Å) atomic oxygen (O) and molecular nitrogen (N2) photoionization cross sections. Theoretical photoionization cross sections of O are determined utilizing the R-matrix plus pseudo-states (RMPS) approximation whereas N2 cross sections are determined using the R-matrix approximation. We include 34 high-resolution partial O state photoionization cross sections and 3 high-resolution partial N2 state photoionization cross sections with supplemental Conway [1988] tabulations for molecular oxygen and the remaining N2 states. We find that photoionization rates computed at 0.01 Å resolution differ substantially from rates computed using low-resolution cross sections, especially in the lower thermosphere below 200 km. Specifically, we find that ionization production rate ratios exhibit variations in altitude of more than ±40% between the high- and low-resolution cases. Past low-resolution calculations at various low spectral resolutions do not sufficiently account for or preserve the highly structured auto-ionization lines in the photoionization cross sections [Meier et al., 2007]. These features, in combination with high-resolution solar spectra, allow photons to penetrate deeper into the Earth’s atmosphere producing larger total ionization rates. These higher ionization rates may finally resolve data-model discrepancies in altitude profiles of electron densities due to the use of low-resolution photoionization cross sections in current E-region models.

A multi-model hydrological assessment in the Congo Basin is performed to assess water availability conditions for historical and future periods (1913–2099). With models limited by scarce in situ observations, a combination of GRACE satellite data and soil-moisture-based drought indices is shown to be capable of estimating water budget, streamflow, and drought and storage variability. Changes in land use and land cover played a role in modifying the hydrologic responses but were found to be within the uncertainties of other inputs, including weather, soil, and model parameters. Seasonal and annual variability in total water storage anomalies (TWSAs) and the modified Palmer drought severity index (MPDSI) display a good correlation with each other. A selected set of global climate models is used to characterize the future temperature and precipitation patterns. It is expected that subbasin-scale variability in future temperature and precipitation increases will result in increased evapotranspiration, decreased runoff, and more drought events in the Congo Basin.

This study examines the role of the mean state in the propagation of the Madden-Julian Oscillation (MJO) over the Maritime Continent (MC). We use an ensemble of simulations made with a single model - the Community Earth System Model version 2 (CESM2) – to assess the effect of the mean state that is unaffected by that of model components such as parameterization schemes. Results show that one ensemble member with an exceptionally stronger MJO propagation also exhibits a much steeper background meridional moisture gradient (MMG) over the southern MC region than the other ensemble members. The simulated mean state affects MJO via its impacts on moisture dynamics - a column water vapor budget reveals a greater advection of mean moisture by MJO wind in the southern MC is responsible for the anomalous MJO activity.

The air pollutant NO is derived largely from transportation sources, and is known to cause various respiratory diseases. Substantial reduction in transport and industrial processes around the globe stemming from the novel SARS-CoV-2 coronavirus and subsequent pandemic resulted in sharp declines in emissions, including for NO. Additionally, the COVID-19 disease that results from the coronavirus may present in its most severe form in those who have been exposed to high levels of air pollution and thus have various co-morbidities. To explore these links, we compared ground-based NOsensor data from 15 US cities from a one month window in 2019 versus the same window during shutdown in 2020. Levels of NO declined roughly 20-60% in 13 of the 15 cities in 2020, linked to similar declines in traffic volume in those cities. To broaden the spatial analysis beyond the individual ground-based monitors, satellite data for tropospheric NO was also analyzed, and was largely consistent with the ground measurements. Many of the cities studied had a substantial percentage of the population with various pre-existing conditions, and a relationship was found between NO levels, respiratory disease, and COVID-19 case counts. This finding indicates that substantial improvements in air pollution and health outcomes can be achieved quickly with local and state policy directives, perhaps leading to more population-level health resilience in the face of future pandemics.

Sedimentary records provide an invaluable background for understanding of complex phenomena that vary within multiple spatio--temporal scales, such as climate and the seismic cycle. Understanding the latter in southern Chile has yielded motivation to develop new tools to deal with such records, in order to build a comprehensive peleoseismic catalog from them. The region inherited an extensive chain of lakes from the pleistocene glaciations, and a strong tephrochronological framework has been developed during the last two decades. Lake deposits have been extensively studied and shown to contain an incredibly sensitive paleoseismic record in the form of lacustrine turbidites. The task is thus to build the best possible chronology making use of all available data. Age--depth modeling is now routinely done by means of bayesian techniques, by using a sedimentation model as prior information and a set of age determinations as data. This approach provides the best results for any single record, but not necessarily for a set of records taken together. This is the goal of the shared chronologies approach, to build the tools for estimating the best chronologies for a set of sedimentary records given some chronological data for each and a set of shared events or stratigraphic markers. We use for this purpose the fact that two or more of such layers should yield age differences close to zero, within the general age uncertainty. This fact is incorporated to the model as prior information, along with the sedimentation model. The idea is clearly usable in a wide range of contexts, and for this reason we would like to share the implementation in a very early stage of development in order to incorporate feedback into design decisions that could affect extensibility and modularity, and to forge collaboration. This contribution shares an early experiment against a simulated data set, as well as the current R implementation and future plans.

This study identifies the role of mid-latitude teleconnection in determining the interannual variability of the Indian summer monsoon in the CFSv2 model. Since CFSv2 has been identified as a potential forecast model for the Indian summer monsoon, it is important to understand the factors that determine its prediction skills at seasonal timescales. ENSO is one of the most important factors driving Indian monsoon variability at seasonal timescales. It is represented realistically in CFSv2. The model, however, misses associated mid-latitude teleconnections. We show that the inadequate strength of mid-latitude teleconnections, especially from the North Atlantic and North-western Pacific can be the primary reasons for the weaker monsoon variability, despite strong ENSO-Monsoon relationship in the model.

For decades the scientific community has been trying to reconcile abundant evidence for fluvial activity on Noachian and early Hesperian Mars with the faint young Sun and reasonable constraints on ancient atmospheric pressure and composition. Recently, the investigation of H2-CO2 collision induced absorption has opened up a new avenue to warm Noachian Mars. We use the ROCKE-3D global climate model to simulate plausible states of the ancient Martian climate with this absorptive warming and reasonable constraints on surface paleopressure. We find that 1.5-2 bar CO2-dominated atmospheres with 3% H2 can produce global mean surface temperatures above freezing, while also providing sufficient warming to avoid surface atmospheric CO2 condensation at 0°-45° obliquity. Simulations conducted with both modern topography and a paleotopography, before Tharsis formed, highlight the importance of Tharsis as a cold trap for water on the planet. Additionally, we find that low obliquity (modern and 0°) is more conducive to rainfall over valley network locations than high (45°) obliquity.

This paper reports on the progresses obtained through the analysis of thermomagnetic features of the region between the southern part of Tocantins state and the northern part of Goias state, in Central Brazil. For that, we made use of data collected through aeromagnetic surveys. Techniques of shading applied to vertical derivative of Anomaly Magnetic Field (AMF) have been used to identify magnetic lineaments. The depth estimates of these structures were obtained by means of spectral Analysis of AMF (Centroid method). The results reveal the existence of a set of near-linear magnetic features in the region between the longitudes of 480W and 510W and between the latitudes of 120S and 140S. This is also an area of moderate microseismic activity and recent studies indicate anomalous geothermal conditions at the upper crust. However, direct evidences of the occurrence of magmatic intrusions at shallow crustal levels are absent. We postulate the hypothesis that the features identied as a result of aeromagnetic survey are indicative of fracture systems, thereby enabling the ow of carbonic uids observed at the region’s thermal springs and transporting geothermal heat.

Magnetic holes (MHs) are pressure-balanced structures characterized by distinct decreases in the interplanetary magnetic field (IMF) strength in otherwise unperturbed solar wind. In this paper we present an analysis of MHs upstream of the Martian bow shock based on three months of observations by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft. Plasma properties within and around these structures as well as their shape characteristics are examined. We find an occurrence rate of around 2.1 events per day. About 48 percent of all events are of linear type with magnetic field rotation across the hole less than 10 degrees. We observe linear magnetic holes both as isolated events and as part of a train of magnetic holes. The proton temperature anisotropy inside MHs increases while alpha particles remain mostly isotropic. The average electron temperature inside MHs modestly increases with increasing hole depth. The duration of linear holes at 1.5 AU shows an increase compared to durations at smaller heliocentric distances, but the structures remain asymmetrical and ellipsoid. A case study of MHs accompanied by a population of heavy pickup ions is also discussed.

As the number of man-made Earth-orbiting objects increases, satellite operators need enhanced space traffic management capabilities to ensure safe space operations. For objects in Low-Earth orbit, orbit determination and prediction require accurate estimates of the local thermospheric density. In previous work, the estimation of thermospheric densities using two-line element data and a reduced-order model for the upper atmosphere was demonstrated. In this paper we demonstrate an approach for density estimation using radar and GPS tracking data. For this, we assimilate the tracking data in a dynamic reduced-order density model using a Kalman filter by simultaneously estimating the orbits and global density. We used the radar range and range-rate measurements of 20 objects and the GPS position measurements of 10 commercial satellites. The estimated density was validated against accurate SWARM density data and compared with NRLMSISE-00, JB2008, and TLE-estimated densities. We found that the estimated densities are significantly more accurate than NRLMSISE-00 and JB2008 densities. In particular, using the GPS data of 10 satellites, we obtain density estimates with a daily 1-σ error of only 5% compared to 14% and 22% for empirical models and 10% for TLE-estimated density. These accurate density estimates can be used to improve orbit determination and the use of real-time tracking data would enable real-time density estimation.

A document by Jhonatan Andres A. Manco. Click on the document to view its contents.

Adjoint tomography (i.e., full-waveform inversion) has been recently applied to ambient seismic noise and teleseismic P waves separately to unveil fine-scale lithospheric structures beyond the resolving ability of traditional ray-based traveltime tomography. In this study, we propose a joint inversion scheme that alternates between frequency-dependent traveltime inversions of ambient noise surface waves and waveform inversions of teleseismic P waves to take advantage of their complementary sensitivities to the Earth’s structure. We apply our method to ambient noise empirical Green’s functions from 60 virtual sources, direct P and scattered waves from 11 teleseismic events recorded by a dense linear array (～ 7 km station spacing) and other regional stations (～ 40 km average station spacing) in central California. To evaluate the performance of the method, we compare tomographic results from ambient noise adjoint tomography, full-waveform inversion of teleseismic P waves, and the joint inversion of the two data sets. Both applications to practical field data sets and synthetic checkerboard tests demonstrate the advantage of the joint inversion over individual inversions as it combines the complementary sensitivities of the two independent data sets towards a more unified model. The 3D model from our joint inversion not only shows major features of velocity anomalies and discontinuities in agreement with previous studies. but also reveals small-scale heterogeneities which provide new constraints on the geometry of the Isabella Anomaly and mantle dynamic processes in central California. The proposed joint inversion scheme can be applied to other regions with similar array deployments for high-resolution lithospheric imaging.

porousMedia4Foam is a package for solving flow and transport in porous media using OpenFOAM - a popular open-source numerical toolbox. We introduce and highlight the features of a new generation open-source hydro-geochemical module implemented within porousMedia4Foam. It opens up a new dimension to investigate hydro-geochemical processes occurring at multiple scales i.e. at the pore-scale, reservoir-scale and at the hybrid-scale relying on the concepts of micro-continuum. The package is designed such that only the chemistry part of the solver is handled by an external package, the geochemical package, which is coupled to the flow and transport solver of OpenFOAM. The evolution of the porous media and fluid properties, such as porosity, permeability, reactive surface area, or diffusivity of chemical species, are handled by various models that we implemented in the package. For the present work, PHREEQC was chosen as the geochemical solver. We conducted benchmarks across different scales to validate the accuracy of our simulator. We further looked at the evolution of mineral dissolution/ precipitation in a hybrid system comprising of a fracture and reactive porous medium.

As soon as the outer plasmasphere gets eroded during geomagnetic storms, the greatly depleted plasmasphere is replenished by cold, dense plasma from the ionosphere. A strong correlation has been revealed between plasmaspheric refilling rates and ambient densities in the topside ionosphere and exosphere, particularly that of atomic hydrogen (H). Although measurements of H airglow emission at plasmaspheric altitudes exhibit storm-time response, temporally static distributions have typically been assumed in the H density in plasmasphere modeling. In this presentation, we evaluate the impact of a realistic distribution of the dynamic H density on the plasmaspheric refilling rate during the geomagnetic storm on March 17, 2013. The temporal and spatial evolution of the plasmaspheric density is calculated by using the Ionosphere-Plasmasphere Electrodynamics (IPE) model, which is driven by a global, 3-D, and time-dependent H density distribution reconstructed from the exospheric remote sensing measurements by NASA’s TWINS and TIMED missions. We quantify the spatial and temporal scales of the refilling rate and its correlation with H densities.

During geomagnetic storms, magnetospheric wave activity drives the ion precipitation which can become an important source of energy flux into the ionosphere and strongly affect the dynamics of the Magnetosphere-Ionosphere (MI) coupling. In this study, we investigate the role of Electro Magnetic Ion Cyclotron (EMIC) waves in causing ion precipitation into the ionosphere using simulations from the RAM-SCBE model with and without EMIC waves included. The global distribution of H-band and He-band EMIC wave intensity in the model is based on three different EMIC wave models statistically derived from satellite measurements. Comparisons among the simulations and with observations suggest that the EMIC wave model based on recent Van Allen Probes observations is the best in reproducing the realistic ion precipitation into the ionosphere. Specifically, the maximum precipitating proton fluxes appear at L=4-5 in the afternoon-to-night sector which is in good agreement with statistical results, and the temporal evolution of integrated proton energy fluxes at auroral latitudes is consistent with earlier studies of the stormtime precipitating proton energy fluxes and vary in close relation to the Dst index. Besides, the simulations with this wave model can account for the enhanced precipitation of <20 keV proton energy fluxes at regions closer to earth (L<5) as measured by NOAA/POES satellites, and reproduce reasonably well the intensity of <30 keV proton energy fluxes measured by DMSP satellites. It is suggested that the inclusion of H-band EMIC waves improves the intensity of precipitation in the model leading to better agreement with the NOAA/POES data.

Artisanal and small-scale gold mining (ASGM) represents a significant economic activity for communities in developing countries. In south-eastern Senegal, this activity has increased in recent years and has become the main source of income for the local population. However, it is also associated with negative environmental and social impacts. Considering the recent development of ASGM in Senegal, and the difficulties of the government in monitoring and regulating this activity, this article proposes a method for detecting and mapping ASGM sites in Senegal using Sentinel 2 data and the Google Earth Engine. Two artisanal mining site in Eastern Senegal are selected to develop and test this approach. Detection and mapping are achieved using Principle Component Analysis (PCA), Separability and Threshold (SEaTH) and Support Vector Machine classifier (SVM). The results are validated by ground-truth observations. The PCA indicates that the best period for identifying artisanal mining sites against other types of land-use is the end of dry season, when vegetation is minimal. This result is confirmed by examining the spectral evolution over time of different types of land-use. Input variables for SVM classification are defined by the SEaTH. The classification results are presented as a map with 5 color-coded categories of land-use. The method can be used to map the evolution of mining sites as a function of time using future Sentinel acquisitions. This approach may also be extrapolated to other areas in the Sahel where authorities are also confronted with the difficult regulation of artisanal gold mining activities in remote areas.