The top panel shows seasonal variation in the TRMM (precipitation) data for each season from 2001–2006 illustrating the drought that occurred during 2004 (grey). Precipitation data were standardized by subtracting mean values and dividing by the standard deviation of all seasonal values. Horizontal lines at ± 1 SD highlight the magnitude of the drought. The lower panel shows corresponding changes in the untransformed "normalized difference vegetation index" (NDVI). Seasonal abbreviations reference three-month averages corresponding to winter (Dec, Jan, Feb), spring (Mar, Apr, May), summer (Jun, Jul, Aug) and fall (Sep, Oct, Nov). The grey bar highlights the drought year and is congruent with the figures from the main text.
Calsbeek et al. BMC Evolutionary Biology 2009 9:3 doi:10.1186/1471-2148-9-3