**5. Conclusions**

The failures of 2010 short rains (rainfall in OND) and subsequent long rains (rainfall in MAM) in East Africa caused a pronounced decrease in productivity, leading to a humanitarian crisis. Here we characterize the atmospheric and terrestrial response of tropical East Africa to the 2010–2011 drought. The 2010–2011 drought was extraordinary in temporal, spatial, and intensity anomalies even as compared to previous drought events. A stronger understanding of drought dynamics in East Africa will contribute to improved drought predictions [46] with hopes that their impacts can be prepared for in advance.

The successive failure of the rainy seasons in the 2010–2011 drought resulted in a devastating humanitarian crisis in East Africa. The decreasing trend of the long rains [12], particularly when the short rains fail as a result of the ENSO activity, could yield land cover changes and biome redistribution while fomenting social unrest and food insecurity. Future work related to the 2010–2011 East Africa drought will focus on determining the spatial variability of previous regional droughts to contextualize the unique features of the 2010–2011 event. An improved understanding of the ecosystem productivity response to water stress in these regions is critical due to the carbon impacts of increased drought incidence as a consequence of climate change. In the context of global changes in precipitation seasonality [47], this analysis concludes that SIF is an effective tool to track the response of vegetation to water stress. SIF responds to the water stress of the 2010–2011 East African drought, and it captures the response almost as well as the NDVI even if it has lower spatial resolution and much smaller energy.

**Author Contributions:** Conceptualization, J.-E.L.; Methodology, E.S.R., X.Y., J.-E.L.; Formal Analysis, E.S.R., X.Y.; Writing—Original Draft Preparation, E.S.R.; Writing—Review & Editing, E.S.R., X.Y., J.-E.L.; Visualization, E.S.R., X.Y.

**Funding:** This research received no external funding.

**Acknowledgments:** ESR thanks Greg Jordan-Detamore for his help with layout and design of figures. All data used in this study can be accessed online (see methods section).

**Conflicts of Interest:** The authors declare no conflict of interest.
