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| Titel |
Drought and vegetation stress monitoring in Portugal using satellite data |
| VerfasserIn |
C. Gouveia, R. M. Trigo, C. C. Dacamara |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 9, no. 1 ; Nr. 9, no. 1 (2009-02-18), S.185-195 |
| Datensatznummer |
250006618
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| Publikation (Nr.) |
 copernicus.org/nhess-9-185-2009.pdf |
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| Zusammenfassung |
| Remote sensed information on vegetation and soil moisture, namely the
Normalised Difference Vegetation Index (NDVI) and the Soil Water Index (SWI),
is employed to monitor the spatial extent, severity and persistence of
drought episodes over Continental Portugal, from 1999 to 2006. The severity
of a given drought episode is assessed by evaluating the cumulative impact
over time of drought conditions on vegetation. Special attention is given to
the drought episodes that have occurred in the last decade, i.e., 1999, 2002
and particularly the major event of 2005. During both the 1999 and 2005
drought episodes negative anomalies of NDVI are observed over large sectors
of Southern Portugal for up to nine months (out of eleven) of the vegetative
cycle. On the contrary, the 2002 event was characterized by negative
anomalies in the northern half of Portugal and for a shorter period (eight
out of eleven months). The impact of soil moisture on vegetation dynamics is
evaluated by analyzing monthly anomalies of SWI and by studying the annual
cycle of SWI vs. NDVI. While in the case of the drought episode of 1999 the
scarcity of water in the soil persisted until spring, in the recent episode
of 2005 the deficit in greenness was already apparent at the end of summer.
The impact of dry periods on vegetation is clearly observed in both arable
land and forest, and it is found that arable land presents a higher
sensitivity. From an operational point of view, obtained results reveal the
possibility of using the developed methodology to monitor, in quasi
real-time, vegetation stress and droughts in Mediterranean ecosystems. |
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