Remote sensing observations in the microwave frequencies have been intensively used to map and investigate water dynamics at the land surface. Microwave observations are also increasingly used to observe changes in vegetation structure and function and to study interactions between water and vegetation. For example, microwave observables such as brightness temperature, radar backscatter, polarization, SAR interferometry, GNSS reflectometry, and variables retrieved from them such as vegetation optical depth and soil moisture allow one to map ecosystem states. All these variables can be used to study processes, states, and temporal changes in vegetation–water interactions such as in vegetation phenology, canopy structure, biomass, photosynthesis, evapotranspiration, interception, dew formation, vegetation water content, water stress, surface and root-zone soil moisture, and irrigation.

The special issue aims to advance our understanding on existing and new techniques, methods, and applications of microwave remote sensing for vegetation–water interactions. We welcome studies that use active or passive microwave satellite, airborne, tower, and field observations to monitor processes, states, and temporal dynamics of vegetation–water interactions by

1. developing and evaluating microwave radiative transfer models for vegetation and water;
2. retrieving land surface variables through radiative transfer model inversion, machine learning, or hybrid approaches;
3. evaluating and constraining land surface, ecosystem, crop, forest, and hydrological models with microwave observations; and
4. assessing field experiments on the impacts of plant water dynamics on microwave observations.

This special issue is an outcome of sessions BG3.20 (Global Earth observation for improved understanding of terrestrial ecosystem dynamics) and HS6.4 (Remote sensing of interactions between vegetation and hydrology) held at the General Assembly 2020 of the European Geoscience Union and of the related precursor sessions in previous years. However, the special issue is open for all submissions within its scope.