Assessing vegetation response to precipitation in northwest Morocco during the last decade: an application of MODIS NDVI and high resolution reanalysis data
Understanding vegetation dynamics provides information on changes in land cover that can directly be related to regional changes in the climate system. In data-sparse regions, i.e. northwest Morocco studies are limited by the availability of comprehensive information on precipitation. We extracted precipitation data of high spatiotemporal resolution (2 km, 1 day) from the Northwest Africa Reanalysis (NwAR) and gridded Normalized Difference Negetation Index (NDVI) of the Moderate Resolution Imaging Spectroradiometer (MODIS) that cover northwest Morocco over ten hydrological years (September 2000 to August 2010). The results are based on a sequence of linear regression analyses. The mean precipitation of different input timeframes is systematically applied as the predicting variables to the mean NDVI of the growing seasons. Results show that 73 % of the variance in mean NDVI is explained by the variance in mean precipitation at the beginning of the growing season (November to the end of December). The results also show that 75 % of the variance in the mean NDVI of agriculturally used areas is explained by the variance in mean precipitation of beginning September to the end of December. Potentially irrigated land cover of low to medium explained variance but of a high seasonal range in NDVI cover about 14 % of the study region. We conclude that a considerable part of agricultural used areas are still potentially rain-fed. The applied methods and especially the re-analysed precipitation data of high spatiotemporal resolution open a new quality of analysis valuable for, e.g. monitoring aspects, policy decisions or regulatory actions.
KeywordsLand Cover Grid Point Precipitation Data Land Cover Type Vegetation Response
This study was funded by the German Federal Ministry of Education and Research (BMBF) within the project “Urban Agriculture as an Integrative Factor of Climate-Optimised Urban Development, Casablanca” (grant number 01LG0504A1). This project is part of the megacity research programme “Research for the Sustainable Development of Megacities of Tomorrow, Focus: Energy- and climate-efficient structures in urban growth centres”. We thank Mr. Christopher Brown for revisions and advice.
- Huete A, Justice C, Van Leuwen W (1999) MODIS vegetation index (MOD13). Algorithm theoretical basis document version 3. NASA 129 pp. available at: http://modis.gsfc.nasa.gov/data/atbd/land_atbd.php, access: 28 April 2011
- Janjic ZI (2002) Nonsingular implementation of the Mellor-Yamada level 2.5 scheme in the NCEP meso model. Tech Rep 437Google Scholar
- Malo AR, Nicholson SE (1990) A study of rainfall and vegetation dynamics in the African Sahel using normalized difference vegetation index. J Arid Environ 19:1–24Google Scholar
- Schneider U, Becker A, Finger P, Meyer-Christoffer A, Ziese M, Rudolf B (2013) GPCC’s new land surface precipitation climatology based on quality-controlled in situ data and its role in quantifying the global water cycle. Theoretical App Climatology 115(1–2):15–40. doi: 10.1007/s00704-013-0860-x Google Scholar
- Timbal B, Arblaster JM (2006) Land cover change as an additional forcing to explain the rainfall decline in the south west of Australia. Geophys Res Lett 33(7)L07717. doi: 10.1029/2005gl025361
- WIST (Warehouse Inventory Search Tool) available at: https://wist.echo.nasa.gov/~wist/api/imswelcome/. Accessed 21 February 2011