نتایج جستجو برای: ndvi

تعداد نتایج: 5798  

Journal: :Remote Sensing 2014
Jonathan Barichivich Keith R. Briffa Ranga B. Myneni Gerard van der Schrier Wouter Dorigo Compton J. Tucker Timothy J. Osborn Thomas M. Melvin

Recent warming has stimulated the productivity of boreal and Arctic vegetation by reducing temperature limitations. However, several studies have hypothesized that warming may have also increased moisture limitations because of intensified summer drought severity. Establishing the connections between warming and drought stress has been difficult because soil moisture observations are scarce. He...

2004
K. C. SETO E. FLEISHMAN J. P. FAY C. J. BETRUS

The ability to predict spatial patterns of species richness using a few easily measured environmental variables would facilitate timely evaluation of potential impacts of anthropogenic and natural disturbances on biodiversity and ecosystem functions. Two common hypotheses maintain that faunal species richness can be explained in part by either local vegetation heterogeneity or primary productiv...

2001
Lin ZHU Ryutaro TATEISHI

This research explores the possibility of using linear mixture model to generate fraction images from 1km time series NOAA AVHRR monthly composite NDVI data. The percentages of forest, grassland and farmland in the pixels are determined by applying the Constrained Least Squares (CLS) method over the study area in the northeast region of China. The validation of the model for AVHRR monthly compo...

Journal: :Biology letters 2014
Juan J Gaitán Donaldo Bran Gabriel Oliva Fernando T Maestre Martín R Aguiar Esteban Jobbágy Gustavo Buono Daniela Ferrante Viviana Nakamatsu Georgina Ciari Jorge Salomone Virginia Massara

Drought is an increasingly common phenomenon in drylands as a consequence of climate change. We used 311 sites across a broad range of environmental conditions in Patagonian rangelands to evaluate how drought severity and temperature (abiotic factors) and vegetation structure (biotic factors) modulate the impact of a drought event on the annual integral of normalized difference vegetation index...

پایان نامه :وزارت علوم، تحقیقات و فناوری - دانشگاه تربیت مدرس - دانشکده علوم انسانی 1389

هدف این رساله مدل سازی و ارزیابی ارتباط وردایی عناصر اقلیمی با مقدار وردایی ndvi می باشد. به این منظور داده های بارش، دما و رطوبت نسبی (حداکثر، میانگین و حداقل) 141 ایستگاه هواشناسی و 1115 تصویر ماهوارهای noaa-avhrr، در دوره آماری 2006-1987 استفاده گردید. در این پژوهش ابتدا روش بهینه درون یابی عناصر اقلیمی تعیین گردید. بعد از تصحیح هندسی تصاویر و اعمال شاخص ndvi، ترکیب مقادیر حداکثر ماهانه استخ...

2007
P. E. DENNISON

Normalized Difference Vegetation Index (NDVI) and Normalized Difference Water Index (NDWI) were compared for monitoring live fuel moisture in a shrubland ecosystem. Both indices were calculated from 500 m spatial resolution Moderate Resolution Imaging Spectroradiometer (MODIS) reflectance data covering a 33 month period from 2000 to 2002. Both NDVI and NDWI were positively correlated with live ...

2005
Felix Rembold Fabio Maselli

This current work is aimed at developing and testing a methodology which can be applied to low spatial resolution satellite data to assess inter-annual crop area variations on a regional scale. The methodology is based on the assumption that within mixed pixels, such variations are reflected by changes of the related multitemporal Normalised Difference Vegetation Index (NDVI) profiles. This imp...

Journal: :Remote Sensing 2015
Xianfeng Liu Xiufang Zhu Shuangshuang Li Yanxu Liu Yaozhong Pan

In recent decades, the monitoring of vegetation dynamics has become crucial because of its important role in terrestrial ecosystems. In this study, a satellite-derived normalized difference vegetation index (NDVI) was combined with climate factors to explore the spatiotemporal patterns of vegetation change during the growing season, as well as their driving forces in China from 2001 to 2012. Ou...

2002
Todd M. Scanlon John D. Albertson Kelly K. Caylor Chris A. Williams

Savanna ecosystems are water limited and responsive to rainfall on short time scales, characteristics that can be exploited to estimate fractional cover of trees, grass, and bare soil over large-scale areas from synthesis of remote sensing and rainfall measurements. A method is presented to estimate fractional cover based upon the differing ways in which grasses and trees respond to rainfall, a...

2007
A. Lobo P. Henry M. Hafeez

The modelling of water and energy exchanges between Soil-Vegetation and the ATmosphere (SVAT) often assimilates remotely sensed time series of Vegetation Indices (VIs). At first order, spectral combinations like the Normalized Difference Vegetation Index (NDVI) are known for their ability to witness the geographic and seasonal distribution of greenness on continental surfaces. Another usual com...

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