158 
Figure 7b: same as Fig 7a but at 830nm 
Figure 9: comparison of histogram of corrected , uncorrected 
and previous year NVDI for 1991 after the eruption effect 
Figure 8: Histogram of NDVI over Africa (10°S to 
10°N) before Mt Pinatubo aerosol effect 
ATMOSPl 
Figure 10: same as Fig. 9 but for 1992 
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the last decade, p 
method for correc 
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meteorological da 
RMS error on cor 
KEY-WORDS : 
1 - INTRODUCI 
forestry and envii 
have been hardly 
the difficulties m 
estimated blackbc 
such atmospheric 
atmospheric profi 
et al., 1989 ; Wu 
overpass, particul; 
1985) and especia 
recently, Moran e 
conditions, surfac 
LE=LEp) to a ma 
these surface ene 
temperature) of th 
2 - THEORY AN 
2.1. Estimation o 
obtained with : 
where K .2 = 1260. 
Digital Numbers (