Geographical, biological and remote sensing aspects of the hydrologic atmospheric pilot experiment in the sahel (HAPEX-Sahel)

Prince, Stephen D.; Kerr, Yann H.; Goutorbe, J.P.; Lebel, Thierry; Tinga, A.; Bessemoulin, P.; Brouwer, J.; Dolman, A. J.; Engman, Edwin T.; Gash, J. H. C.; Hoepffner, Michel; Kabat, P.; Monteny, Bruno; Saïd, F.; Sellers, P. J.; Wallace, Jim

doi:10.1016/0034-4257(94)00076-y

Cited by 122 publications

(45 citation statements)

References 15 publications

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“…Keeping these features in perspective, additional differences such as vegetation phenology, effects of thermal stress, and rooting depth can be deduced for the surface-atmosphere exchanges. Our intent is to analyze the net direct and interactive surface feedback pathways using data from two specialized field experiments, one conducted in the semiarid Tropics [Hydrological Atmospheric Pilot Experiment (HAPEX)-Sahel; Goutorbé et al 1994;Prince et al 1995] and the other in the midlatitudes [First International Satellite Land Surface Climatology Project Field Experiment (FIFE); Sellers et al 1988;Sellers and Hall 1992] using a soil vegetation hydrological scheme [Simplified Simple Biosphere (SSiB) model; Xue et al 1991]. A series of statistical-dynamical experiments are performed using a combination of modeling and observational approach.…”

Section: Assessing Midlatitudinal and Semiarid Tropical Surface Effectsmentioning

confidence: 99%

“…HAPEX-Sahel data based on Sellers and Hall (1992) and Prince et al (1995), or 2) parametric results from model calibrations and sensitivity studies (Sellers et al 1989, Dirmeyer and Shukla 1994, Xue et al 1996, or 3) model parameterization default values for the FIFE and HAPEX-Sahel domain [based on Sellers et al (1986), Dolman and Sellers (1989), and Xue et al (1991)]. …”

Section: B Statistical Design Of Experimentsmentioning

confidence: 99%

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Hydrological Land Surface Response in a Tropical Regime and a Midlatitudinal Regime

Niyogi¹,

Xue²,

Raman³

2002

J. Hydrometeor

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Section: Assessing Midlatitudinal and Semiarid Tropical Surface Effectsmentioning

confidence: 99%

Section: B Statistical Design Of Experimentsmentioning

confidence: 99%

Hydrological Land Surface Response in a Tropical Regime and a Midlatitudinal Regime

Niyogi¹,

Xue²,

Raman³

2002

J. Hydrometeor

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“…The landscape consisted of various landcover types: tiger bush, millet, and fallow areas. The main purpose of the campaign was to obtain a better understanding of the changes in the atmospheric circulation due to changes in the land surface conditions in the Sahel from year to year [Prince et al, 1995;Goutorbe et al, 1994]. The most important feature of this campaign was its larger area (110 km x 110 km) compared to FIFE (15 km x 15 km).…”

Section: Fife the First Islscp (International Satellite Land Surfacementioning

confidence: 99%

Comparison of TOVS‐derived land surface variables with ground observations

Lakshmi¹,

Susskind²

2000

J. Geophys. Res.

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Abstract. The Tiros Operational Vertical Sounder (TOVS) Pathfinder Path A retrieved surface skin temperature, surface air temperatures, and surface specific humidity are compared with data obtained from three large-scale field campaigns: the First ISLSCP (International Satellite Land Surface Climatology Project) Field Experiment (FIFE), the Hydrologic Atmospheric Pilot Experiment (HAPEX) in the Sahel, and the Boreal Ecosystem-Atmosphere Study (BOREAS). The long-term estimates of surface skin temperatures, surface air temperatures, and surface vapor pressure were unbiased, and the standard deviations of the errors were about 4øC, 3.5øC, and 3.5 mbar, respectively. The monthly mean variables obtained from the TOVS data at four times of the day (corresponding to the AM and PM overpass for each of two satellites) exhibited realistic diurnal and seasonal cycles when compared with corresponding ground observations.

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“…There are several possible explanations for this pattern. The potential of using the meteorological satellite the Advanced Very High Resolution Radiometer (AVHRR) for wide scale observation of vegetation productivity was increasingly being recognized in the SSZ during the late 1980s (Tucker et al 1983, Tucker et al 1985, and the accessibility of such data increased considerably with the installation of local ground receiving stations, for example the AGRHYMET Regional Centre in Niamey, Niger (Prince et al 1995). At this time, AVHRR time series also began to become reasonably long (~10 years) to enable analysis of vegetation changes (Tucker, Dregne, and Newcomb 1991).…”

Section: Literature Reviewmentioning

confidence: 99%

Remote Sensing of Woodland Structure and Composition in the Sudano-Sahelian zone : Application of WorldView-2 and Landsat 8

Karlson¹

2015

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Woodlands constitute the subsistence base of the majority of people in the Sudano-Sahelian zone (SSZ). Trees and grasses provide key ecosystem goods and services, including soil protection, fuelwood, food products and fodder. However, climate change in combination with rapidly increasing populations and altered land use practices put increasing pressure on the vegetation cover in this region. Low availability of in situ data on vegetation structure and composition hampers research and monitoring of this essential resource. Satellite and aerial remote sensing represents important alternative data sources in this context. The main advantages of remote sensing are that information can be collected with high frequency over large geographical areas at relatively low costs. This thesis explores the utility of remote sensing for mapping and analysing vegetation, primarily trees, in the SSZ. A comprehensive literature review was first conducted to describe how the application of remote sensing for analysing vegetation has developed in the SSZ between 1975 and 2014, and to identify important research gaps. Based on the gaps identified in the literature review, the capabilities of two new satellite sensors (WorldView-2 and Landsat 8) for mapping woodland structure and composition were tested in an agroforestry landscape located in central Burkina Faso. The tree attributes in focus included tree crown area (m 2 ), tree species, tree canopy cover (%) and aboveground biomass (tons ha -1 ). The data processing methods encompassed objectbased image analysis for tree crown delineation, and use of the Random Forest algorithm for tree species classification (WorldView-2) and estimation of tree canopy cover and aboveground biomass (Landsat 8).The literature review revealed that the use of remote sensing has increased extensively in the SSZ, especially since 2010. Remote sensing is increasingly used by diverse scientific disciplines although the contribution from African authors remains relatively low. The main application area has been to analyze changes in vegetation productivity and broad vegetation types, while relatively few studies have used remote sensing to map tree attributes at a higher level of detail, and to analyze interactions between the vegetation cover and environmental factors.This thesis shows that the WorldView-2 satellite represents a useful data source for mapping individual tree attributes, including tree crown area and tree species. The individual tree crown delineation achieved promising results: 85.4% of the reference trees were detected in the WorldView-2 data and tree crown area was estimated with an average error of 45.6%. Both detection and delineation accuracy was influenced by tree size, the degree of crown closure and the composition of the undergrowth vegetation. In addition, WorldView-2 data produced high classification accuracies for five locally important tree species, which are common throughout the SSZ. The highest overall classification accuracy (82.4%) was produced using multi-tempor...

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Geographical, biological and remote sensing aspects of the hydrologic atmospheric pilot experiment in the sahel (HAPEX-Sahel)

Abstract: H A P E X Sahel (Hydrologic Atmospheric Pilot Experiment in the Sahel) was an international program focused on the soil-plant-atmosphere energy, water and carbon balance in the west African Sahel. I t was intended to

Cited by 122 publications

References 15 publications

Hydrological Land Surface Response in a Tropical Regime and a Midlatitudinal Regime

Hydrological Land Surface Response in a Tropical Regime and a Midlatitudinal Regime

Comparison of TOVS‐derived land surface variables with ground observations

Remote Sensing of Woodland Structure and Composition in the Sudano-Sahelian zone : Application of WorldView-2 and Landsat 8

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