References of "Ozer, Pierre"
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See detailBulletin agrométéorologique - Avril 2004
Tychon, Bernard ULg; Ozer, Pierre ULg; Horion, S. et al

in Bulletin Agrométéorologique (2004), 3(1), 1-4

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See detailAnalyse de la campagne agricole 2003 en terme de stress hydrique
DE LONGUEVILLE, FLORENCE; Horion, Stéphanie ULg; Tychon, Bernard ULg et al

in Bulletin de la Société Géographique de Liège (2004), 44

This article presents the evaluation of the crop water stress in 2003 using the Belgian Crop Growth Monitoring System (B-CGMS). The indicator used is the Relative Soil Moisture Index (RSMI), and is based ... [more ▼]

This article presents the evaluation of the crop water stress in 2003 using the Belgian Crop Growth Monitoring System (B-CGMS). The indicator used is the Relative Soil Moisture Index (RSMI), and is based on a calculation integrating soil moisture data. This index shows the differences between needed and effectively available soil water for different crop types. It is one of the outputs of the B-CGMS agrometeorological model. Based on a fixed threshold, days affected by water stress have been identified and computed for specific periods during which lack of soil water is likely to have dramatic impacts on crop production. The cumulative number of days affected by water stress indicator has then been integrated into a GIS to spatially represent the situation of winter wheat and maize during the 2003 crop season. Results suggest that only maize was affected by the water stress in northern and southern Belgium. In the latter area, the lack of water at key periods provoked a yield reduction ranging between 2 and 50%. [less ▲]

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See detailMise en évidence des zones touchées par la désertification par télédétection a basse résolution au Niger
Hountondji, Yvon ULg; Ozer, Pierre ULg; Nicolas, Jacques ULg

in Cybergeo : Revue Européenne de Géographie = Cybergeo - European Journal of Geography (2004)

In order to identify areas where desertification may have occurred over the last two decades, 109 stations located in three bioclimatic zones of Niger are analyzed. Time series of remote sensing data are ... [more ▼]

In order to identify areas where desertification may have occurred over the last two decades, 109 stations located in three bioclimatic zones of Niger are analyzed. Time series of remote sensing data are well suited to this task. Here, we use time series of NOAA AVHRR normalized difference vegetation index (NDVI) data and rainfall data. In this study, trend analysis is used to identify areas within the biomes from 1981 to 1999 in Niger with apparent land degradation in semi-arid areas. It appears that most of Niger (98%) recorded increasing rainfall while only 76% experienced increasing maximum NDVI. However, the combination of the two variables through the ratio shows a widespread reduction of the rain-use efficiency with non significant trend for the stations located in northern Sahel (p=0.52), highly significant for those located in central Sahel (p=0.00009) and significant in southern Sahel (p=0.041). Overall, 75.3% of the sample recorded a significant reduction of the NDVIMax/RR ratio. Only one station out of four (24.7%) presented a stability of the ratio. These negative trends suggest a progressive diminution of the vegetation productivity as highlighted by the lowering of the NDVIMax/RR ratio. This situation suggest a consistently environmental degradation and that desertification processes continued during the last two decades over most of the Sahelian belt of Niger. [less ▲]

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See detailL’enseignement en gestion des risques naturels.
Ozer, Pierre ULg; Tychon, Bernard ULg; Ozer, André ULg et al

in Demarée, Gaston; De Dapper, Morgan; Alexandre, Jean (Eds.) Tropical Climatology, Meteorology and Hydrology: Climate-related risk analysis and sustainable development in tropical areas. (2004)

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See detailUtilisation de la visibilité horizontale pour l’estimation de la qualité de l’air à Niamey, Niger
Ozer, Pierre ULg

in Bulletin de la Société Géographique de Liège (2004), 44

It is now irrefutable that air pollution caused by large amounts of Total Suspended Particulates (TSP) has numerous undesired consequences on human health. Air quality deterioration in the US and in ... [more ▼]

It is now irrefutable that air pollution caused by large amounts of Total Suspended Particulates (TSP) has numerous undesired consequences on human health. Air quality deterioration in the US and in Europe caused by high concentration of African dust is seen as a major health threat although most of these countries are very distant from the Sahara. Surprisingly, no estimates of TSP levels near the Saharan dust source are available. Based on horizontal visibility measurements reduced by dust in the air, TSP levels are estimated at Niamey-Aéroport (Niger) by using different relations found in the literature. It appears that excessive TSP concentration levels are very important in magnitude and frequency. These very high TSP levels represent a tremendous public health threat that should be absolutely taken into consideration by national and international decision makers. [less ▲]

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See detailBois de feu et déboisement au Sahel: mise au point
Ozer, Pierre ULg

in Science et changements planétaires / Sécheresse (2004), 15(3), 243-251

A major environmental issue of the XXIst century, deforestation due to firewood consummation is an increasing problem within the Sahel of West Africa. This article underlines the difficulties to obtain ... [more ▼]

A major environmental issue of the XXIst century, deforestation due to firewood consummation is an increasing problem within the Sahel of West Africa. This article underlines the difficulties to obtain reliable statistics to correctly monitor deforestation. Field data on firewood consumption are dramatically lacking and inventories of forest cover are very poor. In this context, scientists and policymakers often use the data published by FAO to understand the deforestation topic. Unfortunately, we clearly demonstrate that those data are also inaccurate and not coherent. The analysis of several official documents shows that no institution is currently able to produce any reliable data on firewood and its impact on the environment. [less ▲]

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See detailAre the 1999 and 2000 urban floods in Senegal due to exceptional rainfall events?
Sene, Souleymane; Ozer, Pierre ULg

in Demarée, Gaston; De Dapper, Morgan; Alexandre, Jean (Eds.) Tropical Climatology, Meteorology and Hydrology: Climate-related risk analysis and sustainable development in tropical areas. (2004)

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See detailCan dust variability be a regional indicator of land degradation trend in arid and semi-arid areas? Analysis in the Sahel.
Ozer, Pierre ULg

in Demarée, Gaston; De Dapper, Morgan; Alexandre, Jean (Eds.) Tropical Climatology, Meteorology and Hydrology: Climate-related risk analysis and sustainable development in tropical areas. (2004)

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See detailMonitoring drought stress in north-eastern China by means of rainfall data and diachrone indices derived from Pathfinder AVHRR-imagery.
Ozer, Pierre ULg; Tychon, Bernard ULg; Eerens, Herman

in Smits, Paul; Bruzzone, Lorenzo (Eds.) Analysis of Multi-Temporal Remote Sensing Images (2004)

For climatic stress detection and monitoring in the Heilongjiang Province, north-eastem China, an indicator on the interannual vegetation state was extracted from the AVHRR Pathfinder image set (1981-2000 ... [more ▼]

For climatic stress detection and monitoring in the Heilongjiang Province, north-eastem China, an indicator on the interannual vegetation state was extracted from the AVHRR Pathfinder image set (1981-2000) and compared to the rainfall variations over the growing season (June to August). The results show that the vegetation status does not closely depend on rainfall variations in this region. Temperatures, which showed a rapid augmentation in the northern high latitudes since the early 1980s, seem to be a more crucial limiting factor for vegetation growth. Rapid land cover change and large natural disasters are also likely to impact the relationship between rainfall and vegetation. [less ▲]

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See detailBulletin agrométéorologique - Septembre 2003
Tychon, Bernard ULg; Ozer, Pierre ULg; Eerens, H. et al

in Bulletin Agrométéorologique (2003)

Le mois de septembre a été caractérisé par des précipitations et des vitesses moyennes du vent faibles. Par contre, les températures et le rayonnement furent relativement élevés sur l’ensemble du pays ... [more ▼]

Le mois de septembre a été caractérisé par des précipitations et des vitesses moyennes du vent faibles. Par contre, les températures et le rayonnement furent relativement élevés sur l’ensemble du pays. Cette année, les rendements prévus pour les cultures de maï s fourrager et de betterave sucrière, sont respectivement équivalents et inférieurs à ceux observés en 2002. [less ▲]

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See detailA field-based crop and land use map over Sanjiang plain in Heilongjiang derived from multi-temporal imagery of Landsat7-ETM+
Eerens, Herman; Dong, Qinghan; Ozer, Pierre ULg et al

in Cybergeo : Revue Européenne de Géographie = Cybergeo - European Journal of Geography (2003)

Multitemporal Landsat7-ETM+ imagery and supplementary field survey data were used to establish a crop and land use map for an area of ±20 000 km² of Sanjiang Plain in China’s north-eastern province ... [more ▼]

Multitemporal Landsat7-ETM+ imagery and supplementary field survey data were used to establish a crop and land use map for an area of ±20 000 km² of Sanjiang Plain in China’s north-eastern province Heilongjiang. The “field-based” map is based on data of the year 2002 and is created by combining the results of a supervised Maximum Likelihood classification with the estimated field boundaries extracted by an automatic segmentation procedure. No sufficient ground truth was available to perform an independent validation, and some classes are certainly confused. Nevertheless, given the minimal investments and the unexplored potentials for improvement, the approach seems very promising and cost-effective. By superimposing the classification with the map of the administrative counties, regional statistics were derived with the acreage distributions of the concerned crops and land use types. [less ▲]

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See detailBulletin agrométéorologique - Août 2003
Tychon, Bernard ULg; de Longueville, F.; Ozer, Pierre ULg et al

in Bulletin Agrométéorologique (2003)

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See detailBulletin agrométéorologique - Juillet 2003
Tychon, Bernard ULg; Ozer, Pierre ULg; Eerens, H. et al

in Bulletin Agrométéorologique (2003)

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See detailBulletin météorologique - Mai 2003
Tychon, Bernard ULg; Ozer, Pierre ULg; Eerens, M. et al

in Bulletin Agrométéorologique (2003)

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See detailEtude des modifications environnementales à partir des données pluviométriques et NDVI de NOAA-AVHRR en Afrique de l’Ouest
Hountondji, Yvon ULg; Ozer, Pierre ULg; Tychon, Bernard ULg

in Schmitz, Serge; Meert, Henk (Eds.) Les Journées des Géographes Belges: Evaluer la capacité du milieu (2003)

Since the late 1960s, The Sahel of West Africa is affected by a long-term drought and increasing human pressure on the environment leading to desertification processes. The Normalised Difference ... [more ▼]

Since the late 1960s, The Sahel of West Africa is affected by a long-term drought and increasing human pressure on the environment leading to desertification processes. The Normalised Difference Vegetation Index (NDVI), calculated from satellite imagery, is a reliable index of the vegetation status as the vegetation response to rainfall is very strong in semiarid environments. This article presents the NDVI and rainfall evolution from 1981 to 1999 in nine locations along a north-south transect from north-western Niger to north-eastern Benin. These two parameters are then statistically analysed to identify breaks in the trends within the datasets. Over the 19 years analysed, it appears that five out of the nine locations have recorded a significant increase of rainfall, while only two presented a significant increase in NDVI. This dichotomy in observed trends may highlight the on-going slow processes of environmental degradation. [less ▲]

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See detailMonitoring drought using rainfall based and AVHRR Pathfinder image set derived vegetation indices in north-eastern China.
Ozer, Pierre ULg; Eerens, Herman; Tychon, Bernard ULg

in Tychon, Bernard (Ed.) Belgian and Chinese Crop Growth Monitoring Systems: comparison, adaptation and improvement (2003)

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See detailBelgian and Chinese Crop Growth Monitoring Systems: comparison, adaptation and improvement – An introduction
Tychon, Bernard ULg; Ozer, Pierre ULg; Pêcheur, Céline et al

in Tychon, Bernard (Ed.) Belgian and Chinese Crop Growth Monitoring Systems: comparison, adaptation and improvement (2003)

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See detailAdaptation of the Heilongjiang Province Institute of Meteorological Sciences “Crop Growth Dynamic Model” to the Belgian conditions.
Weinzaepflen, Emmanuelle; Ozer, Pierre ULg; Tychon, Bernard ULg

in Tychon, Bernard (Ed.) Belgian and Chinese Crop Growth Monitoring Systems: comparison, adaptation and improvement (2003)

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See detailThe NDWI as a drought index applied to Belgium and Heilongjiang
Tychon, Bernard ULg; Pêcheur, Céline; Ozer, Pierre ULg

in Tychon, Bernard (Ed.) Belgian and Chinese Crop Growth Monitoring Systems: comparison, adaptation and improvement (2003)

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See detailThe Sahelian drought may have ended during the 1990s
Ozer, Pierre ULg; Erpicum, Michel ULg; Demarée, Gaston et al

in Hydrological Sciences Journal = Journal des Sciences Hydrologiques (2003), 48(3), 489-492

The severe drought that affects the Sahel since the late 1960s has been very closely studied and monitored during the last three decades. Recently, after several wet years, it was questioned from a ... [more ▼]

The severe drought that affects the Sahel since the late 1960s has been very closely studied and monitored during the last three decades. Recently, after several wet years, it was questioned from a statistical point of view whether the drought was over. The conclusions of a recent study were that the rainfall deficit was not over at the end of 2000 and that the drought continues. The analysis of the change points in the station rainfall time series suggests differentiating these findings. There is now growing evidence that there is a potential shift towards a more humid state. However, the present analysis shows that the assumption that a significant increase in rainfall may have occurred around the early 1990s could only be verified at the customary confidence level in about 10 years from now. [less ▲]

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