Sökning: "African Sahel"

Visar resultat 1 - 5 av 10 avhandlingar innehållade orden African Sahel.

  1. 1. Mapping Primary Production for the West African Sahel with Satellite Data

    Författare :Jonathan Seaquist; Institutionen för naturgeografi och ekosystemvetenskap; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Physical geography; Sahel; CENTURY; Monte Carlo; GPP; transpiration; LUE; CLAVR; PAR; compositing; MVC; geostatistics; noise; NDVI; NOAA AVHRR; geomorphology; pedology; cartography; climatology; Fysisk geografi; geomorfologi; marklära; kartografi; klimatologi;

    Sammanfattning : A light Use Efficiency (LUE) model is developed that allows the mapping of total growing season Gross Primary Production (GPP) for the West African Sahel, using the Normalized Difference Vegetation Index (NDVI) together with other data. Image quality may be poor in monthly NDVI maximum value composites as shown by an improved geostatistical noise estimation technique. LÄS MER

  2. 2. Demographic History and Adaptation in African Populations

    Författare :Mário Vicente; Carina Schlebusch; Mattias Jakobsson; Lluis Quintana-Murci; Uppsala universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; African demography; human evolutionary genetics; population structure; population admixture; genetic adaptation;

    Sammanfattning : Africa is the continent where modern humans originated and yet, African demographic history remains largely unknown. Through analyzing the genetic composition of extant and extinct individuals, it is possible to reveal signals of past demographic history and adaptation. LÄS MER

  3. 3. On Sahelian-Sudan rainfall and its moisture sources

    Författare :Abubakr A. M. Salih; Qiong Zhang; Michael Tjernström; Alessandra Giannini; Stockholms universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; Sudan; Sahel; rainfall; land use; deforestation; moisture sources; moisture transport; Lagrangian; moisture tagging; regional model; climate modeling; Atmospheric Sciences and Oceanography; atmosfärvetenskap och oceanografi;

    Sammanfattning : The African Sahel is one of the most vulnerable regions to climate variability at different time scales. It is an arid to semi-arid region with limited water resources. The summer rainfall is one of these sources, but it exhibits pronounced interannual variability. This thesis presents several aspects of Sahelian Sudan rainfall. LÄS MER

  4. 4. Spatio-Temporal Estimation for Mixture Models and Gaussian Markov Random Fields - Applications to Video Analysis and Environmental Modelling

    Författare :Johan Lindström; Matematisk statistik; []
    Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; vegetation; time series analysis; video segmentation; spatio-temporal modelling; precipitation; Markov chain Monte Carlo; Gaussian Markov random fields; expectation maximisation; change point detection; Bayesian recursive estimation; African Sahel; adaptive Gaussian mixtures;

    Sammanfattning : In this thesis computationally intensive methods are used to estimate models and to make inference for large, spatio-temporal data sets. The thesis is divided into two parts: the first two papers are concerned with video analysis, while the last three papers model and investigate environmental data from the Sahel area in northern Africa. LÄS MER

  5. 5. Linking Landscapes and Livelihoods : Ecosystem services as a lens in Sudano-Sahelian West Africa

    Författare :Hanna Sinare; Line Gordon; Anders Malmer; Stockholms universitet; []
    Nyckelord :NATURAL SCIENCES; NATURVETENSKAP; NATURVETENSKAP; NATURAL SCIENCES; ecosystem services; landscapes; livelihoods; agroforestry; Sudano-Sahel; West Africa; Natural Resources Management; naturresurshushållning;

    Sammanfattning : Integrated landscape approaches are increasingly called for to reconcile multiple objectives from the perspectives of agriculture, forestry, poverty alleviation and biodiversity conservation. Sudano-Sahelian West Africa with low agricultural productivity and widespread poverty is a hotspot for these issues and has attracted international interest in interventions to improve livelihoods. LÄS MER