80 research outputs found
Regional foliar phenology along a sw-ne climatic gradient in Argentina
Se caracteriza la fenología foliar regional de Argentina mediante parámetros diná- micos que describen una serie temporal de nueve años de imágenes mensuales de índice de vegetación NDVI. Se aplica la Transformada Rápida de Fourier. Se analizan las variaciones de los parámetros obtenidos a lo largo del gradiente climático en una transecta SW-NE. Las variaciones del NDVI medio responden a la disponibilidad hídrica. La amplitud a un año refleja la variación intraanual del NDVI: muy baja en condiciones de alta (clima subtropical muy húmedo) y baja (diagonal árida) disponibilidad hídrica, máxima en los bosques andino-patagónicos caducifolios e intermedia en oasis bajo riego y región semiárida. La amplitud a 0,5 año (variabilidad intraanual) caracteriza regiones agrícolas intensivas en secano (dos cosechas anuales). La fase es más corta en regiones húmedas y más largas en regiones áridas. La amplitud a nueve años caracteriza la variabilidad climática interanual de las zonas áridas.Argentina’s regional foliar phenology is characterized through parameters that describe a nine-year time series of monthly NDVI images. Fast Fourier Transform is applied. Variations in the obtained parameters are analyzed across the climatic gradient of a SW-NE transect. Variations in mean NDVI respond to water availability. Amplitude at one year reflects the intra-annual NDVI variation: the lowest amplitudes occur in conditions of high (very wet sub-humid climate) and low (arid diagonal) water availability, the highest amplitudes occur in deciduous Andean-Patagonian forests, and intermediate values in irrigated oasis and semiarid region. Amplitude at 0.5 years (intra-annual variability) characterizes rainfed areas under intensive agriculture. Phase is shorter in wet regions and longer in arid regions. Amplitude at nine years characterizes the inter-annual climate variability in arid zones.Fil: Gonzalez Loyarte, Maria Margarita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Menenti, Massimo. University Of Delft; Países Bajo
Evaluation of algorithms to estimate daily evapotranspiration from instantaneous measurements under all-sky conditions
Instantaneous EvapoTranspiration (ET) can be estimated using a single set of instantaneous observations by polar orbiting satellites during the day. Daily, weekly or monthly total ET is required for hydrological studies and water resources assessment. This requires daily total ET regardless of cloud cover. The daily total ET is usually determined assuming that the evaporative fraction (EF) remains constant during at least the central hours of the day and that the product of EF times the daily total net radiation gives a satisfactory estimate of daily total ET. The impact of cloud cover is rarely discussed. In this paper, we used data collected at two experimental sites in the Heihe River basin in northwestern China: Arou with grassland in an alpine region and Yingke with agricultural crops in a semi-arid region. Two methods were evaluated to determine daily total ET with instantaneous observations: a) self-conservation of evaporative fraction (EF-const); b) assuming the diurnal course of ET is the same sinusoidal function of the time of the instantaneous observation as the solar irradiance (Rs) (ET-Rs). Daily ET calculated with the two methods were evaluated against observed daily values. The results showed that these assumptions did not hold and the accuracy of ET estimates obtained with either method was reduced by: a) diurnal variation of ET and b) the time lag between ET and net radiation under clear skies. Larger errors occurred when applying both methods under cloudy conditions during the growing season, while in the remaining part of the year the impact of cloud cover was lower.</p
Bioclimatic map for the travesías (vast plains) of Mendoza province (Argentina) based on foliar phenology
El objetivo fue generar un mapa bioclimático
de la llanura de Mendoza que reflejara las diferencias
climáticas expresadas por la actividad
de la vegetación (fenología foliar) a escala regional.
Se partió de la imagen digital del índice
bioclimático de aridez P/ETP, generada en una
etapa anterior a partir de una serie temporal de
imágenes de índice verde (IVDN), y se recodificó
en clases bioclimáticas. Se evaluó en cada
clase la influencia antrópica y edáfica sobre las
condiciones climáticas de aridez reflejadas por
la vegetación. Se graficó la marcha fenológica
anual media para cada bioclima a partir de
una reconstrucción del IVDN. Las clases de
clima húmedo y subhúmedo son de carácter
edáfico debido al riego (oasis). Se proponen
las clases: subdesértico (8,4%), árido inferior
(15,3%), árido superior (24,2 %), semiárido
inferior (25%) y semiárido superior (27,1%).
Cada bioclima tiene una expresión vegetativa
diferente en condiciones naturales. La marcha
fenológica anual muestra que a mayor aridez
menor es el contraste entre el IVDN mínimo
y máximo, y que el momento de máxima cobertura vegetal varía de enero (semiárido) a
abril (subdesértico). Esta propuesta permite
extender y optimizar el conocimiento climático
de las estaciones meteorológicas a través de
toda la llanura mediante la expresión fenológica
de la vegetación.The aim was to propose a bioclimatic
map of the plain of Mendoza province reflecting
the climatic differences expressed by
vegetation activity (foliar phenology) at regional
scale. The digital image of the bioclimatic
aridity index P/ETP, resulting from a previous
research on time series of NDVI images, was
recoded into bioclimatic classes. Each class
was analysed, assessing whether factors such
as soil or human activities are influencing aridity,
as expressed by vegetation. Mean annual
phenological rhythm was graphed for each
bioclimate by reconstructing the yearly NDVI
curve. Results show that humid and subhumid
classes are due to irrigation. The proposed
map presents five classes: subdesert (8.4%),
lower arid (15.3%), upper arid (24.2%), lower
semiarid (25%) and upper semiarid (27.1%).
Each climatic class has a different expression
of vegetation activity under natural conditions,
all year long. The phenological rhythm shows
that aridity reduces the contrast between
minimum and maximum NDVI and that time
of maximal vegetation cover varies from
January, under semiarid climate, to April, in
subdesert climate. This proposal allows enhancement
and optimization of meteorological
data throughout the whole plain by means of
vegetation phenology.Fil: González Loyarte, María Margarita.
Instituto Argentino de Investigaciones de las Zonas Áridas Fil: Menenti, Massimo.
Istituto per i Sistemi Agricoli e Forestali del Mediterraneo (Italia)Fil: Diblasi, Ángela.
Universidad Nacional de Cuyo. Facultad de Ciencias Económica
Spectral region identification versus individual channel selection in supervised dimensionality reduction of hyperspectral image data
Methodological proposal for assessing peripheral lands to the Lavalle irrigated oasis, Mendoza (Argentina)
La factibilidad de obtener productos agrícolas
de calidad, irrigados con agua salina,
hace necesario evaluar áreas periféricas al
oasis irrigado para determinar su aptitud para
el cultivo. El objetivo es articular diversas
metodologías para cartografiar y evaluar unidades
ecológicamente homogéneas en tierras
marginales de Mendoza utilizando las
comunidades vegetales como indicador. Se
relevó un área piloto mediante procesamiento
de imagen LANDSAT/TM y se analizó la
vegetación, suelo y freática. Las unidades
evaluadas y sus respectivos rangos de
salinidad, en dS m-1, hasta 50 cm fueron: estepa
de Heterostachys ritteriana, 91-83; matorral
de Allenrolfea vaginata con H. ritteriana,
83-48; matorral abierto de A.vaginata con
Prosopis strombulifera, 62-55; estepa abierta
de Suaeda divaricata con Atriplex argentina,
52-83; matorral de S. divaricata con Lycium
tenuispinosum, 40-43; bosquecillo abierto de
Prosopis flexuosa, 37-26; matorral denso de
Prosopis alpataco, 7-6. La concentración de
sales solubles sobrepasa los niveles críticos
tolerados por las plantas cultivadas. No se detectaron
niveles freáticos en los primeros 15 m
de profundidad. Se considera que los suelos
tienen buen drenaje interno, por lo que pueden
ser recuperados sin inversiones elevadas. Este
enfoque metodológico mostró una buena correspondencia
entre las comunidades vegetales,
su expresión espectral y las condiciones de
salinidad y drenaje del suelo.The feasibility to obtain quality agricul
tural products, irrigated with saline water,
makes it necessary to assess areas peripheral
to the irrigated oasis in order to determine their
suitability for cropping. The goal is to combine
diverse methodologies for mapping and
assessing ecologically homogeneous units in
marginal lands of Mendoza, using plant
communities as an indicator of these units. A
pilot area was surveyed using LANDSAT/TM
image processing, and vegetation, soil and
water table were analysed. Assessed vegetation
units and their respective salinity ranges
(dS m-1), up to 50 cm depth, were: steppe of
Heterostachys ritteriana, 91-83; shrubland of
Allenrolfea vaginata with H. ritteriana, 83-48;
open shrubland of A.vaginata con Prosopis
strombulifera, 62-55; open steppe of Suaeda
divaricata with Atriplex argentina, 52-83;
shrubland of S. divaricata con Lycium tenuispinosum,
40-43; open woodland of Prosopis
flexuosa, 37-26; dense shrubland of Prosopis
alpataco, 7-6. The concentration of soluble
salts exceeds the critical levels tolerated by
cultivated plants. No water tables were
detected within 15 m from the surface. It is
considered that soils have good drainage
conditions, so they can be recovered without
high investment. This methodological approach
showed good correspondence among plant
communities, their spectral expression, and soil
salinity and drainage conditions.Fil: González Loyarte, María Margarita.Fil: Gaviola, Silvia.
Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Ingeniería AgrícolaFil: Buk, Enrique.
Instituto Argentino de Nivología, Glaciología y Ciencias AmbientalesFil: Rodeghiero, Alfio G..
Universidad Nacional de Cuyo. Facultad de Ciencias Agrarias. Departamento de Ciencias BiológicasFil: Menenti, Massimo
Bioclimatic map for the Travesías (vast plains) of Mendoza province (Argentina) based on foliar phenology
El objetivo fue generar un mapa bioclimático de la llanura de Mendoza que reflejara las diferencias climáticas expresadas por la actividad de la vegetación (fenología foliar) a escala regional. Se partió de la imagen digital del índice bioclimático de aridez P/ETP, generada en una etapa anterior a partir de una serie temporal de imágenes de índice verde (IVDN), y se recodificó en clases bioclimáticas. Se evaluó en cada clase la influencia antrópica y edáfica sobre las condiciones climáticas de aridez reflejadas por la vegetación. Se graficó la marcha fenológica anual media para cada bioclima a partir de una reconstrucción del IVDN. Las clases de clima húmedo y subhúmedo son de carácter edáfico debido al riego (oasis). Se proponen las clases: subdesértico (8,4%), árido inferior (15,3%), árido superior (24,2 %), semiárido inferior (25%) y semiárido superior (27,1%). Cada bioclima tiene una expresión vegetativa diferente en condiciones naturales. La marcha fenológica anual muestra que a mayor aridez menor es el contraste entre el IVDN mínimo y máximo, y que el momento de máxima co-bertura vegetal varía de enero (semiárido) a abril (subdesértico). Esta propuesta permite extender y optimizar el conocimiento climático de las estaciones meteorológicas a través de toda la llanura mediante la expresión fenológica de la vegetación.The aim was to propose a bioclimatic map of the plain of Mendoza province reflecting the climatic differences expressed by vegetation activity (foliar phenology) at regional scale. The digital image of the bioclimatic aridity index P/ETP, resulting from a previous research on time series of NDVI images, was recoded into bioclimatic classes. Each class was analysed, assessing whether factors such as soil or human activities are influencing aridity, as expressed by vegetation. Mean annual phenological rhythm was graphed for each bioclimate by reconstructing the yearly NDVI curve. Results show that humid and subhumid classes are due to irrigation. The proposed map presents five classes: subdesert (8.4%), lower arid (15.3%), upper arid (24.2%), lower semiarid (25%) and upper semiarid (27.1%). Each climatic class has a different expression of vegetation activity under natural conditions, all year long. The phenological rhythm shows that aridity reduces the contrast between minimum and maximum NDVI and that time of maximal vegetation cover varies from January, under semiarid climate, to April, in subdesert climate. This proposal allows enhancement and optimization of meteorological data throughout the whole plain by means of vegetation phenology.Fil: Gonzalez Loyarte, Maria Margarita. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Provincia de Mendoza. Instituto Argentino de Investigaciones de las Zonas Áridas. Universidad Nacional de Cuyo. Instituto Argentino de Investigaciones de las Zonas Áridas; ArgentinaFil: Massimo Menenti. Istituto Per I Sistemi Agricoli E Forestali del Mediter; ItaliaFil: Diblasi, Angela Magdalena. Universidad Nacional de Cuyo; Argentin
Determination of regional distributions and seasonal variations of land surface heat fluxes from Landsat-7 Enhanced Thematic Mapper data over the central Tibetan Plateau area
An overview of monitoring methods for assessing the performance of nature-based solutions against natural hazards
To bring to fruition the capability of nature-based solutions (NBS) in mitigating hydro-meteorological risks (HMRs) and facilitate their widespread uptake require a consolidated knowledge-base related to their monitoring methods, efficiency, functioning and the ecosystem services they provide. We attempt to fill this knowledge gap by reviewing and compiling the existing scientific literature on methods, including ground-based measurements (e.g. gauging stations, wireless sensor network) and remote sensing observations (e.g. from topographic LiDAR, multispectral and radar sensors) that have been used and/or can be relevant to monitor the performance of NBS against five HMRs: floods, droughts, heatwaves, landslides, and storm surges and coastal erosion. These can allow the mapping of the risks and impacts of the specific hydro-meteorological events. We found that the selection and application of monitoring methods mostly rely on the particular NBS being monitored, resource availability (e.g. time, budget, space) and type of HMRs. No standalone method currently exists that can allow monitoring the performance of NBS in its broadest view. However, equipments, tools and technologies developed for other purposes, such as for ground-based measurements and atmospheric observations, can be applied to accurately monitor the performance of NBS to mitigate HMRs. We also focused on the capabilities of passive and active remote sensing, pointing out their associated opportunities and difficulties for NBS monitoring application. We conclude that the advancement in airborne and satellite-based remote sensing technology has signified a leap in the systematic monitoring of NBS performance, as well as provided a robust way for the spatial and temporal comparison of NBS intervention versus its absence. This improved performance measurement can support the evaluation of existing uncertainty and scepticism in selecting NBS over the artificially built concrete structures or grey approaches by addressing the questions of performance precariousness. Remote sensing technical developments, however, take time to shift toward a state of operational readiness for monitoring the progress of NBS in place (e.g. green NBS growth rate, their changes and effectiveness through time). More research is required to develop a holistic approach, which could routinely and continually monitor the performance of NBS over a large scale of intervention. This performance evaluation could increase the ecological and socio-economic benefits of NBS, and also create high levels of their acceptance and confidence by overcoming potential scepticism of NBS implementations
Nature-based solutions efficiency evaluation against natural hazards: modelling methods, advantages and limitations
Nature-based solutions (NBS) for hydro-meteorological risks (HMRs) reduction and management are becoming increasingly popular, but challenges such as the lack of well-recognised standard methodologies to evaluate their performance and upscale their implementation remain. We systematically evaluate the current state-of-the art on the models and tools that are utilised for the optimum allocation, design and efficiency evaluation of NBS for five HMRs (flooding, droughts, heatwaves, landslides, and storm surges and coastal erosion). We found that methods to assess the complex issue of NBS efficiency and cost-benefits analysis are still in the development stage and they have only been implemented through the methodologies developed for other purposes such as fluid dynamics models in micro and catchment scale contexts. Of the reviewed numerical models and tools MIKE-SHE, SWMM (for floods), ParFlow-TREES, ACRU, SIMGRO (for droughts), WRF, ENVI-met (for heatwaves), FUNWAVE-TVD, BROOK90 (for landslides), TELEMAC and ADCIRC (for storm surges) are more flexible to evaluate the performance and effectiveness of specific NBS such as wetlands, ponds, trees, parks, grass, green roof/walls, tree roots, vegetations, coral reefs, mangroves, sea grasses, oyster reefs, sea salt marshes, sandy beaches and dunes. We conclude that the models and tools that are capable of assessing the multiple benefits, particularly the performance and cost-effectiveness of NBS for HMR reduction and management are not readily available. Thus, our synthesis of modelling methods can facilitate their selection that can maximise opportunities and refute the current political hesitation of NBS deployment compared with grey solutions for HMR management but also for the provision of a wide range of social and economic co-benefits. However, there is still a need for bespoke modelling tools that can holistically assess the various components of NBS from an HMR reduction and management perspective. Such tools can facilitate impact assessment modelling under different NBS scenarios to build a solid evidence base for upscaling and replicating the implementation of NBS
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