نتایج جستجو برای: تفاضل ndvi
تعداد نتایج: 8128 فیلتر نتایج به سال:
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...
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...
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...
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...
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 ...
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...
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...
Determining land surface fractional cover from NDVI and rainfall time series for a savanna ecosystem
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...
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...
خاک به عنوان مهمترین منابع طبیعی ایران، شدیدا توسط فرسایش آبی تهدید می شود. یکی از عوامل فرسایش آبی فرسایندگی باران است. هدف از این تحقبق پهنه بندی مکانی و زمانی تغییرات فرسایندگی باران در جنوب غرب ایران است. خصوصیات حدود 10000 رگبار متعلق به 27 ایستگاه هواشناسی تجزیه و تحلیل گردید و میزان انرژی جنبشی (e) و حداکثر شدت 30 دقیقه ای (i30) رگبارها محاسبه شد. روش اسپلاین (spline) برای پهنه بندی ماها...
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