Search results for "DIFFERENCE VEGETATION INDEX"

Forecasting the vegetation photosynthetic activity over the Sahel: a Model Output Statistics approach

2009

The predictability of the mean August–September photosynthetic activity of vegetation over the Sahel for the period 1982–2002 is explored through a Model Output Statistics approach using ECHAM4.5 retrospective forecasts. Given the poor ability of Atmospheric General Circulation Models (AGCMs) to correctly simulate rainfall over the Sahel, the stress is put on using atmospheric dynamics alone. The mean July–September predicted fields of zonal wind at 600 hPa, and humidity flux at 850 hPa, are selected because of their key role in the West African Monsoon system and their consistency in AGCMs. Coupled modes of NDVI/atmospheric dynamics are extracted using Canonical Correlation Analyses perfor…

Comparison of differences in resolution and sources of controlling factors for gully erosion susceptibility mapping

2018

Abstract Gully erosion has been identified as an important soil degradation process and sediment source, especially in arid and semiarid areas. Thus, it is useful to identify the spatial occurrence of this form of water erosion in the landscape and the most vulnerable areas. In this study, we explored the effects of different pixel sizes on some controlling factors extracted from a digital elevation model and remote sensing data when producing a gully erosion susceptibility map (GESM) of Ekbatan Dam Basin, Hamadan, Iran. An inventory map of the gully landforms was prepared based on global positioning system routes of the gullies, extensive field surveys, and visual interpretations of satell…

Estudio crítico de los índices de severidad y la superficie afectada por el incendio de Sierra de Luna (Zaragoza)

2017

[EN] To determine the area burned by fire and its associated severity related to this forest fire taken place in Sierra de Luna (Zaragoza), on July 4th, 2015, three spectral indices derived from Landsat-8 imagery have been calculated: NDVI, NBR and BAI. Comparing the results obtained from each of them, in a wildland fire with extensive crop areas surrounded by forested areas, it has been demonstrated that combination of ΔNBR and BAI substantially improves the calculation of the burned area, concerning both in its external perimeter and in the unburned zones inside of the perimeter. For severity calculation is proposed a new methodology based on before and after NBR differences and its BAI c…

Intraspecific Differences in Spectral Reflectance Curves as Indicators of Reduced Vitality in High-Arctic Plants

2017

Remote sensing is a suitable candidate for monitoring rapid changes in Polar regions, offering high-resolution spectral, spatial and radiometric data. This paper focuses on the spectral properties of dominant plant species acquired during the first week of August 2015. Twenty-eight plots were selected, which could easily be identified in the field as well as on RapidEye satellite imagery. Spectral measurements of individual species were acquired, and heavy metal contamination stress factors were measured contemporaneously. As a result, a unique spectral library of dominant plant species, heavy metal concentrations and damage ratios were achieved with an indication that species-specific chan…

Global vegetation monitoring through multitemporal analysis of pathfinder AVHRR land database

2005

We have applied a Land Surface Temperature algorithm to the whole Pathfinder AVHRR Land (PAL) database, aiming at studying the evolution of the vegetation at a global scale. The Land Surface Temperature parameter, along with NDVI, will allow retrieving vegetation changes between July 1981 and September 2001. We have also built a classification which takes into account both vegetation variations and thermal patterns, from NDVI and Air Temperature at 2 meters height data. This classification allows differentiating areas which present close vegetation changes throughout the year, but totally different climates, as for example in mountainous and semiarid regions. The main quality of this classi…

NDVI seasonal amplitude and its variability

2008

NDVI (Normalized Difference Vegetation Index) is a remotely sensed index of vegetation greenness. Its yearly cycle gives information on vegetation type or health, and monitoring its temporal evolut...

2015

In this study we present a hyperspectral flying goniometer system, based on a rotary-wing unmanned aerial vehicle (UAV) equipped with a spectrometer mounted on an active gimbal. We show that this approach may be used to collect multiangular hyperspectral data over vegetated environments. The pointing and positioning accuracy are assessed using structure from motion and vary from σ = 1° to 8° in pointing and σ = 0.7 to 0.8 m in positioning. We use a wheat dataset to investigate the influence of angular effects on the NDVI, TCARI and REIP vegetation indices. Angular effects caused significant variations on the indices: NDVI = 0.83–0.95; TCARI = 0.04–0.116; REIP = 729–735 nm. Our analysis high…

Relation between reflectance of rice crop and indices of pollution by heavy metals in soils of albufera natural park (Valencia, Spain)

1993

13 páginas, 3 figuras, 4 tablas, 1 foto.

Childhood intermittent and persistent rhinitis prevalence and climate and vegetation: a global ecologic analysis

2014

Abstract Background The effect of climate change and its effects on vegetation growth, and consequently on rhinitis, are uncertain. Objective To examine between- and within-country associations of climate measures and the normalized difference vegetation index with intermittent and persistent rhinitis symptoms in a global context. Methods Questionnaire data from 6- to 7-year-olds and 13- to 14-year-olds were collected in phase 3 of the International Study of Asthma and Allergies in Childhood. Associations of intermittent (>1 symptom report but not for 2 consecutive months) and persistent (symptoms for ≥2 consecutive months) rhinitis symptom prevalences with temperature, precipitation, vapor…

Timing and patterns of the ENSO signal in Africa over the last 30 years: insights from normalized difference vegetation index data.

2014

Abstract A more complete picture of the timing and patterns of the ENSO signal during the seasonal cycle for the whole of Africa over the three last decades is provided using the normalized difference vegetation index (NDVI). Indeed, NDVI has a higher spatial resolution and is more frequently updated than in situ climate databases, and highlights the impact of ENSO on vegetation dynamics as a combined result of ENSO on rainfall, solar radiation, and temperature. The month-by-month NDVI–Niño-3.4 correlation patterns evolve as follows. From July to September, negative correlations are observed over the Sahel, the Gulf of Guinea coast, and regions from the northern Democratic Republic of Congo…