The Effect of Vegetation on the Seasonality of Precipitation in the Amazon: Preliminary Insights and Observations

Abstract:

The interactions between vegetation activity and climate have been widely recognized as important drivers of the dynamics of the earth system. This is particularly relevant in the context of global change, where both ecosystems and the climate system are changing. In recent years, several studies have concentrated in the relationship between vegetation activity and hydro-climatic processes in the Amazon basin, with particular interest in the relationship between vegetation activity and the dynamics of precipitation. Some studies suggest a lengthening of the dry season in this region during recent decades, leading to a regime of late onsets of the Amazon rainy season. Although some explanations include physical mechanisms involving large-scale ocean-atmosphere processes, local processes, such as vegetation activity, should influence the dynamics of precipitation. However, lacking are studies that directly explore the effect of recent changes in vegetation dynamics with the lengthening of the dry season in the region. We use long-term observations, derived from climate reanalysis data in the central and southern portions of the Amazon basin, to characterize the dynamics of the transition between seasons and contrast it with key indicators of vegetation dynamics derived from remotely-sensed observations of vegetation activity. Our preliminary observations suggest a clear differentiation between years with long and short dry seasons. Further, this differentiation corresponds with energy and water fluxes, mediated by vegetation activity. Collectively our insights highlight important connections between local-to-regional ecological dynamics with larger scale hydroclimatic processes that are relevant in the dynamics of the Earth system.