Proceedings of the Symposium on Global and Environmental Monitoring: Proceedings of the Symposium on Global and Environmental Monitoring

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Multivolume work

Persistent identifier:: 856665355

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts ; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856665355

Language:: English

Document type:: Multivolume work

Volume

Persistent identifier:: 856669164

Title:: Proceedings of the Symposium on Global and Environmental Monitoring

Sub title:: techniques and impacts; September 17 - 21, 1990, Victoria Conference Centre, Victoria, British Columbia, Canada

Scope:: XIV, 912 Seiten

Year of publication:: 1990

Place of publication:: Victoria, BC

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 856669164

Illustration:: Illustrationen, Diagramme, Karten

Signature of the source:: ZS 312(28,7,1)

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Editor:: International Society for Photogrammetry and Remote Sensing, Commission of Photographic and Remote Sensing Data

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Volume

Collection:: Earth sciences

Chapter

Title:: [WA-4 GLOBAL MONITORING (2)]

Document type:: Multivolume work

Structure type:: Chapter

Chapter

Title:: SENEGALESE LAND SURFACE CHANGE ANALYSIS AND BIOPHYSICAL PARAMETER ESTIMATION USING NOAA AVHRR SPECTRAL DATA. David L. Toll, Fred M. Yukovich

Document type:: Multivolume work

Structure type:: Chapter

SENEGALESE LAND SURFACE CHANGE ANALYSIS AND BIOPHYSICAL PARAMETER ESTIMATION USING NOAA AVHRR SPECTRAL DATA David L. Toll NASA/Goddard Space Flight- Center Greenbelt, MD 20771 Fred M. Yukovich Research Triangle Institute Research Triangle Park, NC ABSTRACT Surface biophysical estimates were derived from analysis of NOAA Advanced Very High Spectral Resolution (AVHRR) spectral data of the Senegalese area of west Africa. The derived surface parameters were of solar albedo, spectral visible and near-infrared band reflectance, spectral vegetative index, and ground temperature. Wet and dry linked AVHRR scenes from 1981 through 1985 in Senegal were analyzed for a semi-wet southerly site near Tambacounda and a predominantly dry northerly site near Podor. Related problems were studied to convert satellite derived radiance to biophysical estimates of the land surface. Problems studied were associated with sensor miscalibration, atmospheric correction, surface anisotropy of reflected radiation, narrow satellite band reflectance to broad solar band conversion, and ground emissivity correction. Solar albedo derived estimates for both sites were indicated not to change markedly with significant antecedent precipitation events or correspondingly from increases in green leaf vegetation density. The bright soil/substrate contributed to a high albedo for the dry related scenes, whereas the high internal leaf reflectance in green vegetation canopies in the near-IR contributed to high solar albedo for the wet related scenes. Furthermore, the relationship between solar albedo and ground temperature was poor, indicating the solar albedo had little control of the ground temperature. NDVI and the derived visible reflectance were more sensitive to antecedent rainfall amounts and green vegetation changes than were near-IR changes. The information in the NDVI related to green leaf density changes primarily was from the visible reflectance. The contribution of the near-IR reflectance to explaining green vegetation is largely reduced When there is a bright substrate or the canopy has significant woody vegetation amounts. KEYWORDS: Albedo, NDVI, AVHRR, Senegal, Land Change 1 1- TMRCJXX7TEDN The western sub-Saharan region has over the last decade undergone periods of severe drought followed by periods of near—average rainfall (Motha et al. 1980 and Nicholson 1985) . Analysis of the polar orbiting NOAA Advanced Very High Resolution Radiometer (AVHRR) spectral data may provide a means to study regional land surface changes associated with drought and anthropogenic activities and provide further insight to land surface and atmosphere interactions. However, the extraction of biophysical parameters of the land surface from the AVHRR using directional and spectral radiance is associated with numerous difficulties that were examined for this study: 1) radiometric calibration of the optical bands (i.e., the AVHRR. bands without an on-board calibrator) (Hoiben et al. 1989a); 2) land surface anisotropy sensed by directional derived AVHRR sensors (Kimes et al. 1985); 3) solar albedo estimation from AVHRR narrow band passes (Toll 1989); 4) heterogeneous ground emissivity complicating the land surface temperature estimate (Becker 1987); and 5) atmospheric aerosol and water vapor temporal and spatial variability affecting ground surface derivations (D’Almeida 1986). The primary objective of the study is to use AVHRR derived spectral data to evaluate land surface changes and to provide biophysical information derived from the satellite: radiance to examine land surface-climatology interactions. To characterize the landscape, surface derived estimates of solar albedo, spectral vegetation index and ground temperature are extracted from the AVHRR spectral data. Surf ace meteorological data of the western sub-Saharan for Tambacounda and Podor (available from the NOAA National Climate Data Center, .NCDC) were used to report climatic conditions and to describe the state of the atmosphere (e.g., temperature, rain, aerosol loading, wind, and clouds) for the time of the satellite overpass. 2. STUDY SUB The area selected for study is the Senegalese area in the sub-Saharan encompassing two ecological areas from north to south, the Sahel (averaging 100-400 mm of precipitation) and the Soudan (400-800 mm) (Nicholson 1983) . The study region area is diverse because of a steep south to north precipitation gradient, with mean annual isohyets occurring parallel to equal lines of latitude. The vegetation is largely steppe, with changes to desert in the north and changes to savannah in the the south (Monad 1986). The area has extensive pastoral lands, largely from insufficient rainfall to support agriculture. Man induced effects from overgrazing of livestock and gathering of firewood has compounded the environmental effects from drought. Justice and Hiemauz (1986) report these changes in addition to drought have led to an overall lower net primary productivity as derived through analysis of NOAA AVHRR spectral data. Tucker et al.

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