Javascript verkar inte påslaget? - Vissa delar av Lunds universitets webbplats fungerar inte optimalt utan javascript, kontrollera din webbläsares inställningar.
Du är här

Influence of solar zenith angles on observed trends in the NOAA/NASA 8-km Pathfinder normalized difference vegetation index over the African Sahel

Publiceringsår: 2006
Språk: Engelska
Sidor: 1973-1991
Publikation/Tidskrift/Serie: International Journal of Remote Sensing
Volym: 27
Nummer: 9-10
Dokumenttyp: Artikel i tidskrift
Förlag: Taylor & Francis


The strong systematic change in solar zenith angles (SZA) due to annual orbital drift of the NOAA satellites has raised the suspicion of the influence of residual illumination on the calibrated normalized difference vegetation index (NDVI) derived from the Pathfinder AVHRR Land (PAL) database. The aim of this work is to analyse if trends in AVHRR NDVI from 1982 to 2000 over the Sahel region in Africa depend on variations in SZA. The analysis uses both ordinary least squares regression and cointegration to analyse possible linear dependencies between NDVI and SZA on a per satellite basis. Tests for integration and cointegration fail to find any significant evidence for either. This, together with the ability of simple deterministic models to explain primarily SZA constitutes evidence against integration and cointegration, indicating that linear relationships can be examined using ordinary linear regression. Regression gives no consistent relationship between NDVI and SZA and the explanatory power (R 2) of the regression is low (on average 0.08). However there is some evidence for downward bias in NDVI due to nonlinear interactions between NDVI and SZA when SZA is large (>= 80 degrees) leading to the conclusion that PAL data from the year 2000 should not be used for analyses in these environments.


  • Physical Geography
  • Probability Theory and Statistics


  • ISSN: 1366-5901

Box 117, 221 00 LUND
Telefon 046-222 00 00 (växel)
Telefax 046-222 47 20
lu [at] lu [dot] se

Fakturaadress: Box 188, 221 00 LUND
Organisationsnummer: 202100-3211
Om webbplatsen