pinecone/core-2020-05-10-deduplication huggingface dataset:
Spatiotemporal evolution of a severe winter dust event in the western Mediterranean: Aerosol optical and physical properties

An outstanding Saharan dust event affected the Iberian Peninsula during winter 2016 (20 to 25 February). The impact of this event on ambient PM10 surface levels and its spatial and temporal evolution was investigated by means of data from 250 air quality stations across mainland Spain and the Balearic Islands. The event had a significant impact on surface PM10 levels, and on 22 February, 90% of the air quality monitoring sites registered PM10 concentrations above the EU daily limit value of 50 µg/m3. The study of the attenuated backscattering vertical profiles associated with African dust evidenced a complex structure, with a thick aerosol layer that was at higher altitudes over the pre-Pyrenees compared to the coastal area of Barcelona but closer to the surface than typically observed at both sites. Optical and physical properties of dust particles were investigated at the continental background Global Atmosphere Watch mountain observatory of Montsec (MSA) in the pre-Pyrenees. Good agreement was found between in situ and passive remote sensing methodologies once the aloft dust layer reached the MSA station. Scattering Ångström exponent values decreased to values close to zero (even below zero for surface in situ measurements) indicating the predominance of coarse particles. On the contrary, absorption Ångström exponent values increased during the Saharan dust outbreak denoting an absorption enhancement at shorter wavelengths, characteristic of mineral dust particles. Furthermore, the performance of NMMB/BSC-Dust and BSC-DREAM8b models has been qualitatively evaluated for the dust spatial distribution across Spain and the vertical structure over MSA and Barcelona showing good agreement.Postprint (published version
A predictive model for the spectral bioalbedo of snow

We present the first physical model for the spectral ‘bioalbedo’ of snow, which predicts the spectral reflectance of snow packs contaminated with variable concentrations of red snow algae with varying diameters and pigment concentrations, and then estimates the effect of the algae on snow melt. The bio-optical model estimates the absorption coefficient of individual cells, a radiative transfer scheme calculates the spectral reflectance of snow contaminated with algal cells, which is then convolved with incoming spectral irradiance to provide albedo. Albedo is then used to drive a point-surface energy balance model to calculate snow pack melt rate. The model is used to investigate the sensitivity of snow to algal biomass and pigmentation, including subsurface algal blooms. The model is then used to recreate real spectral albedo data from the High Sierra (California, USA) and broadband albedo data Mittivakkat Gletscher (SE Greenland). Finally, spectral ‘signatures’ are identified that could be used to identify biology in snow and ice from remotely sensed spectral reflectance data. Our simulations indicate that algal blooms can influence snowpack albedo and melt rate, but also highlight that “indirect” feedbacks related to their presence are a key uncertainty that must be investigated
Microbes influence the biogeochemical and optical properties of maritime Antarctic snow.

Snow melt in the Antarctic Peninsula Region has increased significantly in recent decades, leading to greater liquid water availability across a more expansive area. As a consequence, changes in the biological activity within wet Antarctic snow require consideration if we are to better understand terrestrial carbon cycling on Earth's coldest continent. This paper therefore examines the relationship between microbial communities and the chemical and physical environment of wet snow habitats on Livingston Island of the maritime Antarctic. In so doing, we reveal a strong reduction in bacterial diversity and autotrophic biomass within a short (<1 km) distance from the coast. Coastal snowpacks, fertilized by greater amounts of nutrients from rock debris and marine fauna, develop obvious, pigmented snow algal communities that control the absorption of visible light to a far greater extent than with the inland glacial snowpacks. Absorption by carotenoid pigments is most influential at the surface, whilst chlorophyll is most influential beneath it. The coastal snowpacks also indicate higher concentrations of dissolved inorganic carbon and CO2 in interstitial air, as well as a close relationship between chlorophyll and dissolved organic carbon (DOC). As a consequence, the DOC resource available in coastal snow can support a more diverse bacterial community that includes microorganisms from a range of nearby terrestrial and marine habitats. Therefore, since further expansion of the melt zone will influence glacial snowpacks more than coastal ones, care must be taken when considering the types of communities that may be expected to evolve there
Revised cloud processes to improve the mean and intraseasonal variability of Indian summer monsoon in climate forecast system: Part 1

The National Centre for Environmental Prediction (NCEP) Climate Forecast System (CFS) is being used for operational monsoon prediction over the Indian region. Recent studies indicate that the moist convective process in CFS is one of the major sources of uncertainty in monsoon predictions. In this study, the existing simple cloud microphysics of CFS is replaced by the six-class Weather Research Forecasting (WRF) single moment (WSM6) microphysical scheme. Additionally, a revised convective parameterization is employed to improve the performance of the model in simulating the boreal summer mean climate and intraseasonal variability over the Indian summer monsoon (ISM) region. The revised version of the model (CFSCR) exhibits a potential to improve shortcomings in the seasonal mean precipitation distribution relative to the standard CFS (CTRL), especially over the ISM region. Consistently, notable improvements are also evident in other observed ISM characteristics. These improvements are found to be associated with a better simulation of spatial and vertical distributions of cloud hydrometeors in CFSCR. A reasonable representation of the subgrid-scale convective parameterization along with cloud hydrometeors helps to improve the convective and large-scale precipitation distribution in the model. As a consequence, the simulated low-frequency boreal summer intraseasonal oscillation (BSISO) exhibits realistic propagation and the observed northwest-southeast rainband is well reproduced in CFSCR. Additionally, both the high and low-frequency BSISOs are better captured in CFSCR. The improvement of low and high-frequency BSISOs in CFSCR is shown to be related to a realistic phase relationship of clouds
Direct MSTID mitigation in precise GPS processing

This is the peer reviewed version of the following article: Hernandez, M., Wielgosz, P., Paziewski, J., Krypiak-Gregorczyk, A., Krukowska, M., Stepniak, K., Kaplon, J., Hadas, T., Sosnica, K., Bosy, J., Orús, R., Monte, E., Yang, H., Garcia-Rigo, A., Olivares-Pulido, G. Direct MSTID mitigation in precise GPS processing. "Radio science", Març 2017, vol. 52, núm. 3, p. 321-337, which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/2016RS006159/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-ArchivingIn this paper, the authors summarize a simple and efficient approach developed to mitigate the problem in precise GNSS positioning originated by the most frequent ionospheric wave signatures: the Medium Scale Travelling Ionospheric Disturbances (MSTIDs). The direct GNSS Ionospheric Interferometry technique (hereinafter dGII), presented in this paper, is applied for correcting MSTID effects on precise Real Time Kinematic (RTK) and tropospheric determination. It consists of the evolution of the former climatic Differential Delay Mitigation Model for MSTIDs (DMTID), for real-time conditions, using ionospheric data from a single permanent receiver only. The performance is demonstrated with networks of GNSS receivers in Poland, treated as users under real-time conditions, during two representative days in winter and summer seasons (days 353 and 168 of year 2013). In range domain, dGII typically reduces the ionospheric delay error up to 10-90% of the value when the MSTID mitigation model is not applied. The main dGII impact on precise positioning is that we can obtain reliable RTK position faster. In particular the ASR (ambiguity success rate) parameter increases, from 74% to 83%, with respect to the original uncorrected observations. The average of time to first fix is shortened from 30s to 13s. The improvement in troposphere estimaton, due to any potential impact of the MSTID mitigation model, was most difficult to demonstrate.Peer ReviewedPostprint (author's final draft
Scale dependence of the hydraulic properties of a fractured aquifer estimated using transfer functions

This is the peer reviewed version of the following article: [Pedretti, D., A. Russian, X. Sanchez-Vila, and M. Dentz (2016), Scale dependence of the hydraulic properties of a fractured aquifer estimated using transfer functions, Water Resour. Res., 52, 5008–5024, doi:10.1002/2016WR018660. ], which has been published in final form at http://onlinelibrary.wiley.com/doi/10.1002/2016WR018660/abstract. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.We present an investigation of the scale dependence of hydraulic parameters in fractured media based on the concept of transfer functions (TF). TF methods provide an inexpensive way to perform aquifer parameter estimation, as they relate the fluctuations of an observation time series (hydraulic head fluctuations) to an input function (aquifer recharge) in frequency domain. Fractured media are specially sensitive to this approach as hydraulic parameters are strongly scale-dependent, involving nonstationary statistical distributions. Our study is based on an extensive data set, involving up to 130 measurement points with periodic head measurements that in some cases extend for more than 30 years. For each point, we use a single-porosity and dual-continuum TF formulation to obtain a distribution of transmissivities and storativities in both mobile and immobile domains. Single-porosity TF estimates are compared with data obtained from the interpretation of over 60 hydraulic tests (slug and pumping tests). Results show that the TF is able to estimate the scale dependence of the hydraulic parameters, and it is consistent with the behavior of estimates from traditional hydraulic tests. In addition, the TF approach seems to provide an estimation of the system variance and the extension of the ergodic behavior of the aquifer (estimated in approximately 500 m in the analyzed aquifer). The scale dependence of transmissivity seems to be independent from the adopted formulation (single or dual-continuum), while storativity is more sensitive to the presence of multiple continua.Peer ReviewedPostprint (author's final draft
Tracer-based characterization of hyporheic exchange and benthic biolayers in streams

Este artículo contiene 20 páginas, 2 tablas. 5 figuras.Shallow benthic biolayers at the top of the streambed are believed to be places of enhanced\ud
biogeochemical turnover within the hyporheic zone. They can be investigated by reactive stream tracer\ud
tests with tracer recordings in the streambed and in the stream channel. Common in-stream measurements\ud
of such reactive tracers cannot localize where the processing primarily takes place, whereas isolated vertical\ud
depth profiles of solutes within the hyporheic zone are usually not representative of the entire stream. We\ud
present results of a tracer test where we injected the conservative tracer bromide together with the reactive\ud
tracer resazurin into a third-order stream and combined the recording of in-stream breakthrough curves\ud
with multidepth sampling of the hyporheic zone at several locations. The transformation of resazurin was\ud
used as an indicator of metabolism, and high-reactivity zones were identified from depth profiles. The\ud
results from our subsurface analysis indicate that the potential for tracer transformation (i.e., the reaction\ud
rate constant) varied with depth in the hyporheic zone. This highlights the importance of the benthic biolayer,\ud
which we found to be on average 2 cm thick in this study, ranging from one third to one half of the\ud
full depth of the hyporheic zone. The reach-scale approach integrated the effects of processes along the\ud
reach length, isolating hyporheic processes relevant for whole-stream chemistry and estimating effective\ud
reaction rates.J.L.A.K. was supported as a visiting\ud
scientist at the U.S. Geological Survey\ud
in Reston, VA, USA by the German\ud
Academic Exchange Service (DAAD)\ud
through a DAAD Doctoral Scholarship\ud
and by a Carl Zeiss Stiftung scholarship\ud
for Ph.D. research. Further support\ud
came from NSF grants EAR 08-38338\ud
and HRD-1345169 (R.G.P.), NSF grant\ud
EAR 08-10140 (J.D.D.), and NSF grant\ud
EAR 08-14990, and the USGS National\ud
Water Quality and Water Availability\ud
and Use Programs (J.W.H. and L.G.L.).Peer reviewe
Overtopping induced failure of non-cohesive, homogenous fluvial dikes

Accurate predictions of breach characteristics are necessary to reliably estimate the outflow hydrograph and the resulting inundation close to fluvial dikes. Laboratory experiments on the breaching of sand-filled fluvial dikes were performed, considering a flow parallel to the dike axis. The breach was triggered by overtopping of the dike crest. A detailed monitoring of the transient evolution of the breach geometry was conducted, providing key insights into the gradual and complex processes involved in fluvial dike failure. The breach develops in two phases: (1) the breach becomes gradually wider and deeper eroding on the downstream side along the main channel, and (2) breach widening controlled by side slope failures, continuing in the downstream direction only. Increasing the inflow discharge in the main channel, the breach formation time decreases significantly and the erosion occurs preferentially on the downstream side. The downstream boundary condition has a strong influence on the breach geometry and the resulting outflow hydrograph.Peer reviewe
Improving degradation of emerging organic compounds by applying chaotic advection in Managed Aquifer Recharge in randomly heterogeneous porous media

Improving degradation rates of emerging organic compounds (EOCs) in groundwater is still a challenge. Although their degradation is not fully understood, it has been observed that some substances are preferably degraded under specific redox conditions. The coupling of Managed Aquifer Recharge with soil aquifer remediation treatment, by placing a reactive layer containing organic matter at the bottom of the infiltration pond, is a promising technology to improve the rate of degradation of EOCs. Its success is based on assuming that recharged water and groundwater get well mixed, which is not always true. It has been demonstrated that mixing can be enhanced by inducing chaotic advection through extraction-injection-engineering. In this work, we analyze how chaotic advection might enhance the spreading of redox conditions with the final aim of improving degradation of a mix of benzotriazoles: benzotriazole, 5-methyl-benzotriazole, and 5-chloro-benzotriazole. The degradation of the first two compounds was fastest under aerobic conditions whereas the third compound was best degraded under denitrification conditions. We developed a reactive transport model that describes how a recharged water rich in organic matter mixes with groundwater, how this organic matter is oxidized by different electron acceptors, and how the benzotriazoles are degraded attending for the redox state. The model was tested in different scenarios of recharge, both in homogenous and in heterogenous media. It was found that chaotic flow increases the spreading of the plume of recharged water. Consequently, different redox conditions coexist at a given time, facilitating the degradation of EOCs.Peer ReviewedPostprint (author's final draft
Magnetosheath propagation time of solar wind directional discontinuities

Observed delays in the ground response to solar wind directional discontinuities have been explained as the result of larger than expected magnetosheath propagation times. Recently, Samsonov et al. (2017, https://doi.org/10.1002/2017GL075020) showed that the typical time for a southward interplanetary magnetic field (IMF) turning to propagate across the magnetosheath is 14 min. Here by using a combination of magnetohydrodynamic simulations, spacecraft observations, and analytic calculations, we study the dependence of the propagation time on solar wind parameters and near‐magnetopause cutoff speed. Increases in the solar wind speed result in greater magnetosheath plasma flow velocities, decreases in the magnetosheath thickness and, as a result, decreases in the propagation time. Increases in the IMF strength result in increases in the magnetosheath thickness and increases in the propagation time. Both magnetohydrodynamic simulations and observations suggest that propagation times are slightly smaller for northward IMF turnings. Magnetosheath flow deceleration must be taken into account when predicting the arrival times of solar wind structures at the dayside magnetopause
Volcano and ship tracks indicate excessive aerosol-induced cloud water increases in a climate model

Aerosol-cloud interaction is the most uncertain mechanism of anthropogenic radiative forcing of Earth’s climate, and aerosol-induced cloud water changes are particularly poorly constrained in climate models. By combining satellite retrievals of volcano and ship tracks in stratocumulus clouds, we compile a unique observational dataset and confirm that liquid water path (LWP) responses to aerosols are bidirectional, and on average the increases in LWP are closely compensated by the decreases. Moreover, the meteorological parameters controlling the LWP responses are strikingly similar between the volcano and ship tracks. In stark contrast to observations, there are substantial unidirectional increases in LWP in the Hadley Centre climate model, because the model accounts only for the decreased precipitation efficiency and not for the enhanced entrainment drying. If the LWP increases in the model were compensated by the decreases as the observations suggest, its indirect aerosol radiative forcing in stratocumulus regions would decrease by 45%
Estimating sea surface temperature measurement methods using characteristic differences in the diurnal cycle

Lack of reliable observational metadata represents a key barrier to understanding sea surface temperature (SST) measurement biases, a large contributor to uncertainty in the global surface record. We present a method to identify SST measurement practice by comparing the observed SST diurnal cycle from individual ships with a reference from drifting buoys under similar conditions of wind and solar radiation. Compared to existing estimates, we found a larger number of engine room-intake (ERI) reports post War World II and in the period 1960 – 1980. Differences in the inferred mixture of observations lead to a systematic warmer shift of the bias adjusted SST anomalies from 1980 compared to previous estimates, while reducing the ensemble spread. Changes in mean field differences between bucket and ERI SST anomalies in the Northern Hemisphere over the period 1955 – 1995 could be as large as 0.5 °C and are not well reproduced by current bias adjustment models
Multi-TID detection and characterization in a dense Global Navigation Satellite System receiver network

The medium-scale traveling ionospheric disturbances (MSTIDs) constitute the most frequent ionospheric wave signatures. We propose a method for detecting the number of simultaneous MSTIDs from a time series of high-pass-filtered Vertical Total Electron Content (VTEC) maps and their parameters. The method is tested on the VTEC map corresponding to a simulated realistic scenario and on actual data from dual-frequency Global Positioning System (GPS) measurements gathered by +1200 GPS receivers of the GPS Earth Observation Network (GEONET) in Japan. The contribution consists of the detection of the number of independent MSTIDs from a nonuniform sampling of the ionospheric pierce points. The problem is set as a sparse decomposition on elements of a dictionary of atoms that span a linear space of possible MSTIDs. These atoms consist of plane waves characterized by a wavelength, direction, and phase on a surface defined, the part of the ionosphere sounded by the GEONET (i.e., 25°N to 50°N of latitude and 125°E to 155°E of longitude). The technique is related to the atomic decomposition and least absolute shrinkage and selection operator. The geophysical contribution of this paper is showing (a) the detection of several simultaneous MSTIDs of different characteristics, with a continuous change in the velocity; (b) detection of circular MSTID waves compatible by time and center with a specific earthquake; (c) simultaneous superposition of two distinct MSTIDs, with almost the same azimuth; and (d) the presence at nighttime of MSTIDs with velocities in the range 400–600 m/s.Peer ReviewedPostprint (published version
Solar wind plasma parameter variability across solar cycles 23 and 24 : from turbulence to extremes

Solar wind variability spans a wide range of amplitudes and timescales, from turbulent fluctuations to the 11 year solar cycle. We apply the data quantile-quantile (DQQ) method to NASA/Wind observations spanning solar cycles 23 and 24, to study how the uniqueness of each cycle maximum and minimum manifests in the changing statistical distribution of plasma parameters in fast and slow solar wind. The DQQ method allows us to discriminate between two distinct components of the distribution: the core region simply tracks the solar cycle in its moments but shows little sensitivity to solar wind state or the specific activity of each cycle. This would be consistent with an underlying in situ process such as turbulence driving the evolution of fluctuations up to an outer scale. In contrast, the tail component of the distribution is sensitive both to the differences between the maxima and minima of cycles 23 and 24, and the fast or slow state of the solar wind. The tail component varies over the solar cycle in such a way as to maintain a constant functional form, with only its moments varying with solar activity. Finally, after isolating the core region of the distribution, we test its lognormality over the solar cycle in each solar wind state and find the lognormal provides a more robust description of the statistics in slow wind than fast; however, in both states the goodness of fit is significantly reduced at solar maximum.\u