Estimation of the global net primary productivity using NOAA images and meteorological data: changes between 1988 and 1993

Awaya, Y.; Kodani, Eiji; Tanaka, Kunihiro; Liu, Jiyuan; Zhuang, Dafang; Meng, Yonqing

doi:10.1080/0143116031000139782

Cited by 30 publications

(18 citation statements)

References 28 publications

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“…5a) agrees with maps of net primary production (NPP) derived from satellite and additional data (Awaya et al 2004;Goetz et al 2000;Running et al 2004). CumNDVI is used here as a proxy for NPP and is strongly related to abundance of natural resources.…”

Section: Discussionsupporting

confidence: 66%

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Variability of African farming systems from phenological analysis of NDVI time series

2011

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Food security exists when people have access to sufficient, safe and nutritious food at all times to meet their dietary needs. The natural resource base is one of the many factors affecting food security. Its variability and decline creates problems for local food production. In this study we characterize for sub-Saharan Africa vegetation phenology and assess variability and trends of phenological indicators based on NDVI time series from 1982 to 2006. We focus on cumulated NDVI over the season (cumNDVI) which is a proxy for net primary productivity. Results are aggregated at the level of major farming systems, while determining also spatial variability within farming systems. High temporal variability of cumNDVI occurs in semiarid and subhumid regions. The results show a large area of positive cumNDVI trends between Senegal and South Sudan. These correspond to positive CRU rainfall trends found and relate to recovery after the 1980's droughts. We find significant negative cumNDVI trends near the south-coast of West Africa (Guinea coast) and in Tanzania. For each farming system, causes of change and variability are discussed based on available literature (Appendix A). Although food security comprises more than the local natural resource base, our results can perform an input for food security analysis by identifying zones of high variability or downward trends. Farming Climatic Change (2011) 109:455-477 systems are found to be a useful level of analysis. Diversity and trends found within farming system boundaries underline that farming systems are dynamic.

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Section: Discussionsupporting

confidence: 66%

“…Phenological metrics have also been used to assess food production (Funk and Budde 2009). A phenological metric of special interest is the seasonally cumulated NDVI (cumNDVI) as it is related to net primary productivity (NPP: Awaya et al 2004;Lo Seen Chong et al 1993).…”

Section: Introductionmentioning

confidence: 99%

Variability of African farming systems from phenological analysis of NDVI time series

2011

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“…However, the exact causes for the post-Agung and postPinatubo CO 2 -drawdown has not yet been fully elucidated. A relative atmospheric CO 2 -reduction may also be explained by an increase in net primary production (NPP) of the terrestrial biomass, although several studies indicate a decrease in terrestrial NPP of up to eight years after the Pinatubo eruption, possibly due to a decrease in mean summer temperatures and a shortening of the growing season (Lucht et al, 2002;Nemani et al, 2003;Awaya et al, 2004;Krakauer and Randerson, 2003).…”

Section: Biological Effects In the Surface Ocean In The Earth's Historymentioning

confidence: 99%

The role of airborne volcanic ash for the surface ocean biogeochemical iron-cycle: a review

et al. 2010

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Abstract. Iron is a key micronutrient for phytoplankton growth in the surface ocean. Yet the significance of volcanism for the marine biogeochemical iron-cycle is poorly constrained. Recent studies, however, suggest that offshore deposition of airborne ash from volcanic eruptions is a way to inject significant amounts of bio-available iron into the surface ocean. Volcanic ash may be transported up to several tens of kilometers high into the atmosphere during largescale eruptions and fine ash may stay aloft for days to weeks, thereby reaching even the remotest and most ironstarved oceanic regions. Scientific ocean drilling demonstrates that volcanic ash layers and dispersed ash particles are frequently found in marine sediments and that therefore volcanic ash deposition and iron-injection into the oceans took place throughout much of the Earth's history. Natural evidence and the data now available from geochemical and biological experiments and satellite techniques suggest that volcanic ash is a so far underestimated source for iron in the surface ocean, possibly of similar importance as aeolian dust. Here we summarise the development of and the knowledge in this fairly young research field. The paper Correspondence to: S. Duggen (svend duggen@skoleforeningen.de) covers a wide range of chemical and biological issues and we make recommendations for future directions in these areas. The review paper may thus be helpful to improve our understanding of the role of volcanic ash for the marine biogeochemical iron-cycle, marine primary productivity and the ocean-atmosphere exchange of CO 2 and other gases relevant for climate in the Earth's history.

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“…In this paper, we report findings on the SOS and the cumulative NDVI as the most meaningful across the diverse ecosystems. Variation in SOS in Western Africa due to sowing delays can translate into yield reductions (Buerkert et al, 2001) while cumulative NDVI is indicative of net primary productivity (Awaya et al, 2004).…”

Section: Phenological Analysismentioning

confidence: 99%

The response of African land surface phenology to large scale climate oscillations

Brown

Beurs

Vrieling

2010

Remote Sensing of Environment

130

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Variations in agricultural production due to rainfall and temperature fluctuations are a primary cause of food insecurity on the African continent. Analysis of changes in phenology can provide quantitative information on the effect of climate variability on growing seasons in agricultural regions. Using a robust statistical methodology, we describe the relationship between phenology metrics derived from the 26 year AVHRR NDVI record and the North Atlantic Oscillation index (NAO), the Indian Ocean Dipole (IOD), the Pacific Decadal Oscillation (PDO), and the Multivariate ENSO Index (MEI). We map the most significant positive and negative correlation for the four climate indices in Eastern, Western and Southern Africa between two phenological metrics and the climate indices. Our objective is to provide evidence of whether climate variability captured in the four indices has had a significant impact on the vegetative productivity of Africa during the past quarter century. We found that the start of season and cumulative NDVI were significantly affected by large scale variations in climate. The particular climate index and the timing showing highest correlation depended heavily on the region examined. In Western Africa the cumulative NDVI correlates with PDO in September-November. In Eastern Africa the start of the June-October season strongly correlates with PDO in March-May, while the PDO in December-February correlates with the start of the FebruaryJune season. The cumulative NDVI over this last season relates to the MEI of March-May. For Southern Africa, high correlations exist between SOS and NAO of September-November, and cumulative NDVI and MEI of March-May. The research shows that climate indices can be used to anticipate late start and variable vigor in the growing season of sensitive agricultural regions in Africa.Published by Elsevier Inc.

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Estimation of the global net primary productivity using NOAA images and meteorological data: changes between 1988 and 1993

Cited by 30 publications

References 28 publications

Variability of African farming systems from phenological analysis of NDVI time series

Variability of African farming systems from phenological analysis of NDVI time series

The role of airborne volcanic ash for the surface ocean biogeochemical iron-cycle: a review

The response of African land surface phenology to large scale climate oscillations

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