Estimating the snow-rain transition zone in a semi-arid Andean catchment

2021 ◽  
Author(s):  
Simone Schauwecker ◽  
Gabriel Palma ◽  
Shelley MacDonell ◽  
Katerina Goubanova
Keyword(s):  
Transition Zone ◽  
Early Warning Systems ◽  
Mountain Range ◽  
Arid Environments ◽  
Local Conditions ◽  
The Andes ◽  
Snow Line ◽  
Snow Cover Extent ◽  
Semi Arid ◽  
Precipitation Events

<p>The height of the snow-rain transition during infrequent but high impact precipitation events, closely related to the 0⁰C-isotherm, is a crucial variable for snow cover extent, high discharge flows and flash floods in semi-arid northern Chile. Estimations of the snow-rain transition zone and its past and future changes are therefore fundamental for adaptation strategies and might eventually serve to develop early warning systems in this region. However, there are important challenges that hinder the assessment of the snow-rain transition zone in semi-arid environments and little is known about past and future changes under different global warming scenarios. For example, there are few radiosonde observations along the Andes and most weather stations are located in valley bottoms, influenced by local conditions and the assumption of free-air temperature lapse rates contributes to the uncertainty. We combine different data sets to estimate the past snow-rain transition zone of our study site, the semi-arid Elqui river catchment. Pictures of the snow line after precipitation events - available from social networks - are used to visually estimate the snow line elevation. These values are in high agreement with vertically extrapolated temperature from meteorological stations. Furthermore, we identified considerable biases between the extrapolated 0⁰C-isotherm from meteorological stations and ERA5 reanalysis data. These large biases are probably due to the lowering of the freezing level over complex terrain and need further analysis. Our results contribute to an improved understanding of the snow-rain transition in this region, but also serve to derive a climatology of this key variable along the Andes mountain range, needed for future projections.</p>

scholarly journals Climatology of Winter Orographic Precipitation over the Subtropical Central Andes and Associated Synoptic and Regional Characteristics

2011 ◽  
Vol 12 (4) ◽  
pp. 481-507 ◽  
Author(s):  
Maximiliano Viale ◽  
Mario N. Nuñez
Keyword(s):  
Water Vapor ◽  
Water Vapor Transport ◽  
Windward Side ◽  
Leeward Side ◽  
Orographic Precipitation ◽  
Mountain Range ◽  
The Andes ◽  
Precipitation Regimes ◽  
Fourth Quartile ◽  
Precipitation Events

Abstract Winter orographic precipitation over the Andes between 30° and 37°S is examined using precipitation gauges in the mountains and adjacent lowlands. Because of the limited number of precipitation gauges, this paper focuses on the large-scale variation in cross-barrier precipitation and does not take into account the fine ridge–valley scale. The maximum amount of precipitation was observed on the windward slope of the mountain range below the crest, which was twice that observed on the low-windward side between 32.5° and 34°S. Toward the east of the crest, precipitation amounts drop sharply, generating a strong cross-barrier gradient. The rain shadow effect is greater in the north (32°–34.5°S) than in the south (35°–36.5°S) of the low-lee side, which is probably due to more baroclinic activity in southernmost latitudes and a southward decrease in the height of the Andes enabling more spillover precipitation. The effect of the Andes on winter precipitation is so marked that it modifies the precipitation regimes in the adjacent windward and leeward lowlands north of 35°S. Based on the fact that ~75% of the wintertime precipitation accumulated in the fourth quartile, through four or five heavy events on average, the synoptic-scale patterns of the heavy (into fourth quartile) orographic precipitation events were identified. Heavy events are strongly related to strong water vapor transport from the Pacific Ocean in the pre-cold-front environment of extratropical cyclones, which would have the form of atmospheric rivers as depicted in the reanalysis and rawinsonde data. The composite fields revealed a marked difference between two subgroups of heavy precipitation events. The extreme (100th–95th percentiles) events are associated with deeper cyclones than those for intense (95th–75th percentiles) events. These deeper cyclones lead to much stronger plumes of water vapor content and cross-barrier moisture flux against the high Andes, resulting in heavier orographic precipitation for extreme events. In addition, regional airflow characteristics suggest that the low-level flow is typically blocked and diverted poleward in the form of an along-barrier jet. On the lee side, downslope flow dominates during heavy events, producing prominent rain shadow effects as denoted by the domain of downslope winds extending to low-leeward side (i.e., zonda wind).

scholarly journals Advanced numerical models for the propagation of floods with high-sediment concentrations in mountain rivers

2018 ◽  
Vol 40 ◽  
pp. 06039
Author(s):  
María Teresa Contreras ◽  
Jorge Gironás ◽  
Joannes Westerink ◽  
Cristián Escauriaza
Keyword(s):  
Early Warning ◽  
Flood Hazard ◽  
Numerical Models ◽  
Warning System ◽  
Mass Conservation ◽  
Sediment Concentration ◽  
Early Warning Systems ◽  
Mountain Range ◽  
The Andes ◽  
Wide Range

Rapid floods induced by extreme precipitation are common events in regions near the Andes mountain range. Growing urban development, combined with the changing climate and the influence of El Niño, have increased the exposure of the population in many regions of South America. Simulations of flash floods in these watersheds are very challenging, due to the complex morphology, the insufficient hydrometeorological data, and the uncertainty posed by the variability of sediment concentration. To address these issues, we develop a high-resolution numerical model of the non-linear shallow water equations, coupled with the mass conservation of sediment, and considering the density effects and changes of rheology in the momentum equation. Based on these simulations we develop a real-time early-warning system, by creating a surrogate model or meta-model from the simulations. Using a small set of parameters, we define storms for a wide range of meteorological conditions, and utilize the high-fidelity model results to create a database of flood propagation under different conditions. Through this second model we perform a sophisticated interpolation/regression, and approximate efficiently the flow depths and velocities. This is the first application of its kind in the Andes region, which can be used to improve the prediction of flood hazard in real conditions, employing low computational resources. We also create a framework to develop early warning systems, and to help decision makers and city planners in these mountain regions.

scholarly journals Exogenously Used 24-Epibrassinolide Promotes Drought Tolerance in Maize Hybrids by Improving Plant and Water Productivity in an Arid Environment

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 354
Author(s):  
El-Sayed M. Desoky ◽  
Elsayed Mansour ◽  
Mohamed M. A. Ali ◽  
Mohamed A. T. Yasin ◽  
Mohamed I. E. Abdul-Hamid ◽  
...  
Keyword(s):  
Drought Tolerance ◽  
Agronomic Traits ◽  
Water Productivity ◽  
Positive Association ◽  
Net Photosynthesis ◽  
Antioxidant Enzyme Activities ◽  
Severe Drought ◽  
Arid Environments ◽  
Maize Hybrids ◽  
Semi Arid

The influence of 24-epibrassinolide (EBR24), applied to leaves at a concentration of 5 μM, on plant physio-biochemistry and its reflection on crop water productivity (CWP) and other agronomic traits of six maize hybrids was field-evaluated under semi-arid conditions. Two levels of irrigation water deficiency (IWD) (moderate and severe droughts; 6000 and 3000 m3 water ha−1, respectively) were applied versus a control (well-watering; 9000 m3 water ha−1). IWD reduced the relative water content, membrane stability index, photosynthetic efficiency, stomatal conductance, and rates of transpiration and net photosynthesis. Conversely, antioxidant enzyme activities and osmolyte contents were significantly increased as a result of the increased malondialdehyde content and electrolyte leakage compared to the control. These negative influences of IWD led to a reduction in CWP and grain yield-related traits. However, EBR24 detoxified the IWD stress effects and enhanced all the above-mentioned parameters. The evaluated hybrids varied in drought tolerance; Giza-168 was the best under moderate drought, while Fine-276 was the best under severe drought. Under IWD, certain physiological traits exhibited a highly positive association with yield and yield-contributing traits or CWP. Thus, exogenously using EBR24 for these hybrids could be an effective approach to improve plant and water productivity under reduced available water in semi-arid environments.

scholarly journals Quaternary Glaciations in the Andes of North-Central Chile

1975 ◽  
Vol 14 (70) ◽  
pp. 155-170 ◽  
Author(s):  
Cesar N. Caviedes ◽  
Roland Paskoff
Keyword(s):  
Polar Front ◽  
Southern Andes ◽  
North Central ◽  
Central Chile ◽  
The Andes ◽  
Semi Arid ◽  
Quaternary Glaciations ◽  
Chilean Andes

The extension of the Quaternary glaciations has been studied in the semi-arid Andes of north-central Chile, where the glacial modelling is striking. In the Elqui valley (lat. 30°S.), two glacial advances were identified reaching down to 3 100 m (Laguna glaciation) and 2 500 m (Tapado glaciation). In the Aconcagua valley (lat. 33°S.), moraines from three major glacial advances were found, at 2 800 m (Portillo glaciation), 1 600 m (Guardia Vieja glaciation) and 1 300 m (Salto del Soldado glaciation).The Quaternary glaciations were linked with a decrease of temperature, but more significantly with a marked increase of precipitation probably related to an equatorward shift of 5–6 degrees of the austral polar front. The results obtained in the semi-arid Chilean Andes are correlated with those recently reported from other sectors of the southern Andes.

Changing perceptions of the effect of plant phenolics on nutrient supply in the ruminant

1996 ◽  
Vol 47 (6) ◽  
pp. 829 ◽  
Author(s):  
JB Lowry ◽  
CS McSweeney ◽  
B Palmer
Keyword(s):  
Phenolic Compounds ◽  
Acute Toxicity ◽  
Protein Interactions ◽  
Nutrient Supply ◽  
Arid Environments ◽  
Plant Phenolics ◽  
Ruminant Nutrition ◽  
Forage Plants ◽  
Hydrolysable Tannins ◽  
Semi Arid

Mammalian metabolism of plant phenolics, initially studied in monogastric animals, gave an emphasis to their toxic and antinutrient effects. Subsequent studies in tropical ruminants and wild herbivores have highlighted the high levels than can occur in some diets and the extensive microbial modification and degradation that can occur in the tract. This paper reviews aspects of plant phenolics as they relate to ruminant nutrition in tropical or semi-arid environments in which some forage plants contain high levels of phenolic compounds. Effects range from occasional acute toxicity of hydrolysable tannins, to acetate-releasing microbial degradations that apparently enable certain phenolics to act as nutrients. The most important and complex effects are those due to tannin-protein interactions. Although these can clearly reduce feed intake, nutrient digestibilities, and protein availability, many of the interactions are still not understood. The diverse effects of plant phenolics on nutrient flow probably result from the balance between adverse effects on some organisms and the rate at which they are degraded or inactivated by other organisms, and improved animal performance can likely be obtained by manipulation of rumen microbial metabolism.

scholarly journals Evolution of prehistoric dryland agriculture in the arid and semi-arid transition zone in northern China

PLoS ONE ◽  
2018 ◽  
Vol 13 (8) ◽  
pp. e0198750 ◽  
Author(s):  
Yige Bao ◽  
Xinying Zhou ◽  
Hanbin Liu ◽  
Songmei Hu ◽  
Keliang Zhao ◽  
...  
Keyword(s):  
Transition Zone ◽  
Northern China ◽  
Dryland Agriculture ◽  
Semi Arid

scholarly journals Identification of the degree of impact of dams on the hydrologic regime of semi-arid rivers: an evaluation of the DHRAM method

RBRH ◽  
2017 ◽  
Vol 22 (0) ◽  
Author(s):  
Naiah Caroline Rodrigues de Souza ◽  
◽  
Andrea Sousa Fontes ◽  
Lafayette Dantas da Luz ◽  
Sandra Maria Conceição Pinheiro ◽  
...  
Keyword(s):  
Hydrological Regime ◽  
Flow Regulation ◽  
Hydrologic Regime ◽  
Local Conditions ◽  
Operating Rules ◽  
Hydrologic Variability ◽  
High Degree ◽  
The Impact ◽  
Semi Arid

ABSTRACT The flow regulation that results from the implantation of dams causes consequences to the river ecosystems due to the modification on the characteristics of the hydrologic regime. The investigation of these changes become relevant, mainly in semi-arid regions where there is a great amount of these hydraulic structures and lack of such analyzes. Considering the above, this paper aims to evaluate the Dundee Hydrological Regime Alteration Method (DHRAM) through the classification of the degree of impact of dams located on rivers Itapicuru, Paraguaçu and their tributaries, verifying the adequacy of its use to represent the semi-arid hydrologic regime. Thereby, the DHRAM was applied in three versions: considering the thresholds that define the scores to classify the degree of impact in its original set (accordingly to Black et al. (2005)); with the adjustment of those thresholds to local conditions; and, with the regrouping of variables and adjustment of thresholds. The results showed that the method in its original set is applicable to semi-arid rivers, however it tends to be very restrictive against the high natural hydrologic variability characteristic of these rivers, and it ends up pointing to a high degree of alteration for dams that are known for not causing a very siginifcant flow regulation. The DHRAM with the regrouping of variables and the adjustment of thresholds presented the classification that approached the most to the known characteristics of the studied dams, being useful for the evaluation of the impact of dams still in project, and also to guide the adoption of operating rules that minimize the most significant hydrologic alterations that are identified.

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