The focus of our study is to develop the measurement concepts, observational architecture, and experiments that will increase our capacity to understand and predict the response of forest ecosystems to droughts and future climate extremes. We envisioned two workshops dedicated to the study. The first workshop, held in October 2019, addressed the state-of-the-art theory, models and measurement techniques for studying the water flow in soil-plant-atmosphere continuum and explored the mechanisms underlying the stress and response of plants to droughts. The participants discussed how these mechanisms are spatially and temporally scaled and to what extent the existing remote sensing observations can capture the forest water dynamics from space. Key science questions linking the water dynamics of forest ecosystems to carbon and energy cycles from plants to regional scales were discussed and several gaps in observations and modeling were identified.
In the second workshop, to be held in May 2020, we will pursue a number of avenues that would support needed technology development and science advancements to address the science questions identified in the first workshop. First, we will focus on developing the traceability between the science questions and observables in order to identify the needed measurements, and any necessary breakthroughs in observing architecture and performance. In particular, the study will explore how planned and potential exploratory microwave observations from space and their synergism with optical, hyperspectral, and/or thermal sensing can be used in sensing forest water dynamics from space. Second, we anticipate devising a strategy to support the goals of the study by a series of collaborative activities, including airborne and/or field campaigns, that include existing advanced technologies. These activities will address specific components of science and technology that are needed to improve our readiness and capability for a dedicated spaceborne mission going forward. Finally, we will outline the findings of the workshop to prepare a report and potentially a peer-reviewed publication.