Grass vegetation covers large parts of our globe. Its heat-insulating properties have large impact on temperatures we experience in daily life. Yet, surprisingly little is known about this thin, green layer. Its complex microclimate has hardly been studied and its description in weather and climate models is highly empirical, resulting in large prediction errors. With novel, fine-scale measuring and modeling techniques we aim to unravel the fascinating 3D complexity of grass. The new, physics-based formulations will be implemented and tested in narrow collaboration with weather forecast institutes and companies, to solve an urgent problem in weather and climate modeling.

This project explores the future multi-century coupled evolution of the Greenland ice sheet (GrIS) surface mass balance (SMB, the difference between snow accumulation and surface ablation) and ice flow with the global and regional climate. To date, there are very few coupled studies with Atmosphere-Ocean General Circulation Models and GrIS flow models. These studies have used highly parameterized SMB calculations, regardless of SMB being a major component of the GrIS mass budget. We will use an advanced Earth System Model that bi-directionally couples GrIS surface melt and runoff with an Atmosphere-Ocean General Circulation Model and a dynamical ice sheet flow model. This Earth System Model has been shown to be the first global model capable of realistic GrIS SMB simulation. In this project we explore the processes of interaction between the GrIS and local and global climate, focusing on these aspects: 1) interaction between local and global climate and GrIS surface processes (albedo-melt feedback, cloud impacts on the GrIS surface energy budget, effects of a weakened ocean circulation and associated regional climate change on the GrIS SMB); 2) relationship between atmospheric variability and GrIS melt extremes; and 3) interaction between GrIS flow, surface elevation and SMB. To investigate these processes, we will use a) coupled climate-SMB simulations with a fixed GrIS topography under pre-industrial, historical and two different RCP scenarios for the period 1850-2200, and b) two fully coupled climate-SMB-flow multi-century simulations.

Reactive nitrogen compounds emitted from agriculture, traffic and industry are quickly becoming dominant air pollutants worldwide. This has severe consequences for air quality, ecosystems, and global climate. CAINA aims towards fully understanding the aerosol-cloud interactions under high reactive nitrogen concentrations. We focus on the Netherlands, where ammonia emissions from agriculture combine with NOx from industry and traffic, resulting in high concentrations of ammonium nitrate. These regularly exceed concentrations of sulfates, the main air pollutants in most other regions, by a factor of 5 or more. This makes the selected study region ideal for understanding the chemistry of the future global atmosphere. Clouds are an important component in the life-cycle of reactive nitrogen. First, they are crucial for wet deposition of nitrogen, which has detrimental effects on vulnerable ecosystems. In addition, via chemical reactions in cloud droplets, clouds contribute to the production of nitrogen-containing inorganic (e.g., ammonium nitrate) and organic aerosol particles, with important consequences for air quality and human health. However, it is uncertain how these aqueous-phase reactions proceed under high concentrations of reactive nitrogen and at the relatively high pH values associated with nitrogen-dominated aerosols. Clouds themselves can also be changed by nitrogen pollutants. Increases of cloud condensation nuclei (CCN) and nitric acid concentrations lead to clouds with more, but smaller droplets. This potentially results in more reflective clouds, with possible cooling effects on global climate. However, we do not yet fully understand the role of reactive nitrogen in CCN production and cloud droplet activation. Therefore, field and laboratory experiments combined with model studies are urgently needed to better understand how cloud properties are modified by reactive nitrogen pollutants. Our consortium combines strong expertise in aerosol/cloud physics with expertise in atmospheric chemistry to answer the following research questions: i. How are inorganic and organic pollutants produced in clouds under high reactive nitrogen concentrations? ii. How important is this pathway for the overall air pollution in regions with high nitrogen emissions? iii. What is the concurrent effect on cloud microphysics and cloud reflectivity? A central role in the CAINA project will be played by the Ruisdael Observatory, equipped with extensive observational tools for pollutants, wind fields, and clouds. This creates an ideal outdoor laboratory to study pollutant-cloud interactions under varying nitrogen regimes. We will combine long-term observations and intensive field experiments to study processes that govern CCN concentrations, effects of nitrogen pollutants on cloud microphysics, and cloud processing of aerosols. The field measurements will be interpreted with the help of controlled cloud chamber experiments in the dynamic AIDA cloud chamber, and with the use of high-resolution, cloud-resolving modelling. The observational strategies will optimally constrain a unique Large Eddy Simulation (LES) model that can simulate both non-equilibrium chemistry of nitrogen pollutants and cloud-aerosol interactions. The constrained LES model will quantify both the relevance of cloud processes for nitrogen-containing pollutant levels as well as the pollutant effects on cloud properties. This knowledge is of vital importance to better predict the impact of the anticipated global shift to nitrogen-dominated pollution regimes.

The multidisciplinary MUST2SEA project aims at a better understanding of the current tectonic evolution of Sulawesi (Indonesia) with more emphasis on both inter- and post-seismic plate deformations. It will combine up to two decades of space geodetic data (global navigation systems, synthetic aperture radar and radar altimetry missions) with scientific findings obtained during previous successful NWO/GO and EU-ASEAN projects (GEODYSSEA, SEAMERGES, GEO2TECDI-1/2). The final goal is to provide a better assessment of seismic risk, in particular for the area of Palu, the second largest city on the island. Our exclusive GPS database (1992-present) remains key input to this study as it provides a high spatial coverage in SE Asia. Our project includes making data and processing products readily accessible (online) to the global scientific community and disseminating the final results to the (local) authorities and the general public in Palu. The GPS time series (displacement rates) exhibit numerous co- and post-seismic 3D deformation patterns, as well as measurements of vertical motions that provide valuable input to absolute land-subsidence and relative sea-level change studies. We will exploit the latest state-of-the-art geodetic techniques to re-analyze the entire geodetic database and also try detect any additional land surface (vertical) deformation signals that might have been overlooked in previous analyses (e.g. earthquake pre-cursor events) and evaluate their significance using state of the art geophysical models. This requires a multi-disciplinary approach combining different expertise, methods and data, both in situ and by satellites.