Analysis of the radiation of coronal suprathermal streams

This paper reports on the first measurements of the color index of the coronal suprathermal streams. Observations performed during the total eclipse of 2001 in Angola imply that the color index of streams differs markedly from that for adjacent parts of the surrounding corona taken as reference. The registered drifts to the longwave and shortwave domains of the spectrum are in agreement with theoretical results obtained recently by the authors.Published in Astrofizika, Vol. 48, No. 1, pp. 79–85 (February 2005).     

A global river routing network for use in hydrological modeling

In this paper a relatively simple procedure is presented to construct a global river routing network on a 0.5° latitude–longitude grid. In this network all grid cells in a catchment are coupled and have a flow direction, making it a useful tool in the modeling of river flow on a global scale. The flow directions are based on a digital elevation model and on information on the locations of major rivers (‘stream burning’). The presented river routing network is specifically designed for the assessment of fresh water shortages. We tested the validity of the river routing network by comparing the computed drainage areas with published estimates. This comparison revealed a good similarity and it is concluded that the presented river routing network has sufficient quality to be implemented in global climate models. This could mean a considerable improvement of the surface parameterization in these models.     

A soft hydrological monitoring approach for comparing runoff on a network of small poorly gauged catchments

Catchments in many parts of the world are either ungauged or poorly gauged, and the dominant processes governing their streamflow response are still poorly understood. The analysis of runoff coefficients provides essential insight into catchment response, particularly if both range of catchments and a range of events are compared. This paper investigates how well the hydrological runoff of 11 small, poorly gauged catchments with ephemeral streams (0·1‐0·6 km²) can be compared using estimated runoff with the associated uncertainty. Data of rainfall and water depth at a catchment's outlet were recorded using automatic logging equipment during 2008‐2009. The hydrological regime is intermittent and the annual precipitation ranged between 569 and 727 mm. Discharge was estimated using Manning's equation and channel cross‐section measurements. Innovative work has been performed under controlled experimental conditions to estimate Manning's coefficient values for the different cover types observed in studied streams: non‐aquatic vegetations (giant reed, bramble and thistle), grass and coarse granular deposits. The results show that estimates derived using roughness coefficients differ from those previously established for larger streams with aquatic vegetation. Catchment runoff was compared at both the event and the annual scale. The results indicate significant variability between the catchment's responses. This variability allows for classification in spite of all the uncertainty associated with runoff estimation. This study highlights the potential of using a network of poorly gauged catch ments. From almost no catchment understanding the proposed methodology allows to compare poorly gauged catchments and highlights similarity/dissimilarity between catchment responses. Copyright © 2011 John Wiley & Sons, Ltd.     

Collocation of hydrological and biological attenuation of nitrate in an urban stream

The hydrologic and biogeochemical processes that control nutrient export in urban streams are not well understood. Attenuation can occur by tributary dilution, groundwater discharge, and biological processing both in the water column and the hyporheic zone. A wastewater treatment plant on Pennypack Creek, an urban stream near Philadelphia, PA, provided high nitrate concentrations for analysis of downstream attenuation processes. Longitudinal sampling for an 8‐km reach revealed decreases in nitrate concentration of 2 mg l^?1 at high flow and 4.5 mg l^?1 during low flow. During high flow, δ¹⁵N‐NO₃ increased from 9.5 to 10.5‰ and during low flow increased from 10.1 to 11.1‰. Two reaches were sampled at fine spatial intervals (approximately 200 m) to better identify attenuation processes. Mixing analysis indicated that groundwater discharge and biological processing both control nitrate concentration and isotope signatures. However, fine‐scaled sampling did not reveal spatially discrete zones; instead, these processes were occurring simultaneously. While both processes attenuate nitrate, they have opposite isotope signatures, which may have muted changes in δ¹⁵N‐NO₃. At high flow, a decrease in Cl/NO₃ ratios helped distinguish groundwater discharge occurring along both finely sampled reaches. At low flow, biological processing seemed to be occurring more extensively, but the δ¹⁵N‐NO₃ signature was not consistent with either a single process or a sequential combination of groundwater dilution and biological nitrate attenuation. The collocation of processes makes it more difficult to assess biological processing hot spots and predict how urbanization and subsequent stream restoration influence nitrate attenuation. Copyright © 2016 John Wiley & Sons, Ltd.     

Late Quaternary paleoenvironments and paleoclimatic conditions in the distal Andean piedmont, southern Mendoza, Argentina

The Andean piedmont of Mendoza is a semiarid region covered by extensive and partially vegetated dune fields consisting of mostly inactive aeolian landforms of diverse size and morphology. This paper is focused on the San Rafael plain (SRP) environment, situated in the distal Andean piedmont of Mendoza (34° 30′S), and reports the sedimentology and OSL chronology of two representative exposures of late Quaternary deposits, including their paleoenvironmental and paleoclimatic significance. Eleven facies, including channel, floodplain, fluvio–aeolian interaction, and reworked pyroclastic and aeolian deposits, were described and grouped into two facies associations (FA1 and FA2). FA1 was formed by unconfined sheet flows, minor channelized streams and fluvial–aeolian interaction processes. FA2 was interpreted as aeolian dune and sand-sheet deposits. OSL chronology from the SRP sedimentary record indicates that between ca. 58–39 ka and ca. 36–24 ka (MIS 3), aggradation was governed by ephemeral fluvial processes (FA1) under generally semiarid conditions. During MIS 2, the last glacial maximum (ca. 24–12 ka), a major climatic shift to more arid conditions is documented by significant aeolian activity (FA2) that became the dominant sedimentation process north of the Diamante–Atuel fluvial system. The inferred paleoenvironmental conditions from the SRP sections are in broad agreement with regional evidence.     

Bimodal Structure of Gas Streams in Interacting Binaries

There are two modes of gas streams in close binary systems: geometrically thick for low mass transfer rate or geometrically thin for higher mass transfer. Geometrical thickness of the streams is not proportional to the amount of transferred mass. The limit between the two possibilities is discussed.     

Bedform patterns, subglacial meltwater events, and Late Devensian ice sheet dynamics in north-central Ireland

Glacial bedform patterns and sediments deposited by the temperate and polythermal Late Devensian ice sheet in north-central Ireland record changes in the processes, location, and magnitude of subglacial meltwater throughout the last full glacial cycle (21–14 ¹⁴C kyear BP). Meltwater characteristics are related directly to basal ice thermal regime and ice dynamics, including ice velocity and shifts in the location of ice centres. Therefore, reconstructed meltwater characteristics may provide insight into wider controls on dynamic ice behaviour. A range of meltwater-related features are present across north-central Ireland. These include tunnel valleys, drumlin leeside sequences, eskers, and boulder lags. Other bedforms including Rogen moraines were modified by meltwater activity along ice streams. Meltwater was stored subglacially in two contrasting regions located beneath or near ice centres in north-central Ireland. (1) The Lough Erne Basin is developed in a lowland depression occupied partly by subglacial Rogen moraine ridges which were formed around the time of the last glacial maximum. Meltwater was stored between Rogen ridge crests and released by hydraulic jacking associated with drumlinisation (16.6 ¹⁴C kyear BP) and ice streaming (13.8 ¹⁴C kyear BP). (2) The Lough Neagh Basin occupies a similar lowland depression and was the location of an ice sheet centre throughout the last glacial cycle. No bedforms are present beneath or immediately surrounding Lough Neagh. A larger, more continuous meltwater lake existed in the Lough Neagh depression, probably sealed by a region of cold-based ice outside lake margins. Water escaped through regional-scale tunnel valleys, particularly the Poyntzpass channel which was active during the Carlingford ice readvance (Killard Stadial, correlated with Heinrich event 1 at 14.5 ¹⁴C kyear BP). Overall, reconstructed subglacial lake characteristics and drainage mechanisms are related closely to basal ice thermal regime and substrate relief (controlling lake geometry), and provide insight into controls on overall ice sheet dynamics.     

Explaining radical policy change: Norwegian climate policy and the ban on cultivating peatlands

For decades Norwegian climate policy has largely ignored the agricultural sector and focused on cost-effective emission reductions abroad. Yet in June 2020, Norway decided to ban the cultivation of peatlands to protect critical carbon sinks, and the issue became ‘high politics’. We explain this radical policy change by combining an adapted version of the Multiple Streams framework with the Punctuated Equilibrium model of agenda-setting. We argue that the two models combined can provide a holistic explanatory framework, albeit with two revisions. Firstly, the window of opportunity or punctuation was in our case of a longer duration than both models anticipate. Secondly, we find that multiple complete couplings can take place within the opening of a policy (or more specifically, a decision) window. Both findings can be explained by party competition, thus underlining the need to revise agenda-setting models to better account for party politics.     

Land-use influence on the functional organization of Afrotropical macroinvertebrate assemblages

Studies investigating the effects of human activities on the functional organization of macroinvertebrate communities in tropical streams and rivers are very limited, despite these areas witnessing the greatest loss of natural forests globally. We investigated changes in taxon richness, numerical abundance and biomass of macroinvertebrate functional feeding groups (FFGs) in streams draining different land-use types in the Sosiani-Kipkaren River in western Kenya. Twenty-one sites in river reaches categorized as forested, mixed, urban or agricultural were sampled during the dry and wet seasons. Collected macroinvertebrates were identified to the lowest taxon possible (mainly genus) and classified into five major FFGs; collector-gatherers, collector-filterers, scrapers, predators and shredders. There were significant (p < 0.05) spatial variation in habitat quality, organic matter standing stocks, total suspended solids, electrical conductivity, dissolved oxygen, temperature and nutrient concentrations across land-uses, with forested sites recording lowest values in mean water temperature, electrical conductivity and nutrients while recording highest levels in dissolved oxygen concentrations. Responses in macroinvertebrates to changes in land-use varied with richness, abundance and biomass showing differences within FFGs. Biomass-based metrics responded more strongly to change in land-use while taxon richness was the least predictive, indicating replacement of taxa within FFGs across land-use types. Higher shredder abundance, biomass and richness were recorded in forested streams which were cooler with protected riparian areas and high biomass of coarse particulate organic matter. Collector-gatherers dominated agricultural and urban streams owing to an abundance of particulate organic matter and nutrients, while scrapers responded positively to increased nutrient levels and open canopy in mixed and agricultural streams where primary production and algal biomass was likely increased. Overall, this study provides further evidence of the effects of agricultural and urban land-uses on tropical streams and rivers and contributes to the use of macroinvertebrate FFGs as indicators of ecological health.     

Analysis of rill step–pool morphology and its comparison with stream case

In this paper, the morphology of step–pool features is analysed using rill measurements and literature data for streams. Close-range photogrammetry was used to carry out ground measurements on rills with step–pool units, shaped on a plot having slope equal to 14, 15, 22, 24 and 26%. Data were used to compare the relationships between H/L, in which H is the step height and L is the step length, and the mean gradient of the step–pool sequence, S_m, for streams or the slope of the step–pool unit, S, for rills. The relationship of H/L against S_m is widely used to test the occurrence of the maximum flow resistance condition in streams, which is associated with the range 1 ≤ (H/L)/S_m ≤ 2. Further analyses were carried out to compare both the formation process and the profile of the pool in rills with those related to streams. Moreover, for a single rill channel, an analysis of flow characteristics expressed in terms of Darcy–Weisbach friction factor and Froude number was developed. The results allowed us to state: (i) the relationships of H/L versus S_m and S are quite similar and the steepness ratio for streams, (H/L)/S_m, and for rills, (H/L)/S, generally ranges from 1 to 2; (ii) the formation process and the profile of the pool in rills are not consistent with those occurring in streams; (iii) in the rills, the longitudinal size of the pool is dominant with respect to the maximum scour depth; (iv) the presence of a sequence of step–pool units within a rill segment noticeably increases flow resistance compared to segments with a flat bed; (v) the Froude number of the flow over the sequence of step–pool units in rills is slightly below the range of 0.8–1 corresponding to the maximum flow resistance in step–pool units.