Satellite-Observed Vegetation Responses to Intraseasonal Precipitation Variability

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  • There is limited understanding of how vegetation responds to intraseasonal modes of rainfall variability despite their importance in many tropical regions. We use observations of precipitation and X-band Vegetation Optical Depth (VOD) from 2000 to 2018 to assess the relationships between rainfall and vegetation water content on 25-60-day timescales. Cross-spectral analysis identifies coherent intraseasonal relationships between precipitation and VOD, mostly in arid or semi-arid regions where vegetation is water-limited. Changes in VOD tend to lag anomalous rainfall, usually within 7 days. The fastest vegetation response is observed in sparsely vegetated areas (median 3 days). Following strong intraseasonal wet events, anomalously high VOD can persist for 2 months after the rainfall peak. This vegetation response can feed back onto the atmosphere, so improved representation of vegetation responses in models has the potential to improve subseasonal-to-seasonal forecasts.

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