NDVI-LAI relationship in Napa Valley L. F. Jolznson I 1 TemporaI stability of the NDVI-LA1 relationship in a Napa VaIIey vineyard 2 3 L.F. JO~TSON*32 I 4 5 I 1E arth Systems Science & Policy, California State UniversityMonterey Bay, '6 Seaside, CA, 93955, USA 7 2Earth Science Division, NASA Ames Research Center, Moffett Field, CA, 8 94035, USA 9 10 Tel: (650) 604-3331, Fax: (650) 604-4680, Ernail: 11 12 Keywords: rezmte sensing, multitemporal noni:or;li;g, viaeyaid leaf area, spectral 13 vegetation indices, NDVI, IXONOS sztellite 14 15 Abbreviated title: NDVI-LA1 relationship in Napa Valley 16 17 Abstract 18 Remotely sensed normalized difference vegetation index (AQVI) values, derived 19 from high-resolution satellite images, were compared with ground measurements 20 of vineyard leaf area index &AI) periodically during the 2001 growing season. 21 The two variables were strongly related at six ground calibration sites on each of 22 four occasions (r2 = 0.91 to 0.98). Linear regression equations relating the two 23 vz~abledsi d not sipificantly differ by observation date, and a single equation 24 accounted for 92 percent of the variance in the combined dataset. Temporal 25 stability of the relationship opens the possibility of transforming hQVI maps to 26 LA1 in the absence of repeated ground calibration fieldwork. In order to take 27 advantage of this circumstance, however, steps should be taken to assure temporal 28 consistexy ir; spectral data vahes comprising the hDy1g. /