Details

Autor(en) / Beteiligte

• Mangiarotti, S.
• Mazzega, P.
• Hiernaux, P.
• Mougin, E.

Titel

The vegetation cycle in West Africa from AVHRR–NDVI data: Horizons of predictability versus spatial scales

Ist Teil von

• Remote sensing of environment, 2010-09, Vol.114 (9), p.2036-2047

Ort / Verlag

New York, NY: Elsevier Inc

Erscheinungsjahr

2010

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• The predictability of the vegetation cycle is analyzed as a function of the spatial scale over West Africa during the period 1982–2004. The NDVI–AVHRR satellite data time series are spatially aggregated over windows covering a range of sizes from 8 × 8 km 2 to 1024 × 1024 km 2. The times series are then embedded in a low-dimensional pseudo-phase space using a system of time delayed coordinates. The correlation dimension ( D c ) and entropy of the underlying vegetation dynamics, as well as the noise level (σ) are extracted from a nonlinear analysis of the time series. The horizon of predictability ( H P ) of the vegetation cycle defined as the time interval required for an n% RMS error on the vegetation state to double (i.e. reach 2n% RMS) is estimated from the entropy production. Compared to full resolution, the intermediate scales of aggregation (in the range of 64 × 64 km 2 to 256 × 256 km 2) provide times series with a slightly improved signal to noise ratio, longer horizon of predictability (about 2 to 5 decades) and preserve the most salient spatial patterns of the vegetation cycle. Insights on the best aggregation scale and on the expected vegetation cycle predictability over West Africa are provided by a set of maps of the correlation dimension ( D c ), the horizon of predictability ( H P ) and the level of noise (σ).