Prof. Dr. Z. Su
University of Twente, Faculty of Geo-Information Science and Earth Observation (ITC), Department of Water Resources 
Hengelosestraat 99, P.O.Box 217, 7500 AE Enschede, The Netherlands

e-mail: [email protected], http://www.itc.nl/WRS, Phone: +31 (0)53 4874 311

Key qualification

• Scientist and educator with 30 years of experience in research, education, and project and human resources management
• Expertise in spatial hydrology, earth observation, water cycle and climate, land-atmosphere interaction, and water resources management

Professor Bob Su holds the Chair of Spatial Hydrology and Water Resources Management, and previously served for 15 years as Chairman of Department of Water Resources in Faculty of Geo-Information and Earth Observation (ITC) of University of Twente, Enschede, the Netherlands. Bob Su is a recognized international expert in land-atmosphere processes and interactions and earth observation of water cycle. His research covers remote sensing and numerical modeling of land-atmosphere processes and land–atmosphere interactions, earth observation of water cycle and applications in climate, ecosystem and water resources studies, as well as monitoring food security and water-related disasters. He has coordinated and participated in numerous international projects and experiments and served as committee member of various science communities. His current research focuses on integrating radiative transfer, photosynthesis and energy fluxes with simultaneous transfer of energy, mass and momentum in unsaturated soil via the water-soil-plant-atmosphere pathway as a component of earth system model, modelling microwave signature of land surface and retrieval of soil moisture and vegetation properties, and developing data driven machine learning algorithms for digital twin earth.

Bob Su was Netherlands representative to the intergovernmental ad hoc Group on Earth Observation (GEO). He chaired the sub-division of Remote Sensing and Data Assimilation of European Geosciences Union (EGU) and was a member of the Hydrology Section Technical Committee of American Geophysical Union (AGU). He was also a member of the Earth Science Advisory Committee (ESAC) of the European Space Agency (a 12-member senior advisory body to advise the director of earth observation for satellite mission selections and earth sciences) and served as the chair of land panel in the Earth Explorer 8 selection. He acted as a member of the science evaluation panel for the Earth Observation Envelope Programme of ESA to evaluate its 1490 million EURO EOEP-3 programme 2008-2012 (an 8-member body). Recently, he served as vice president of the International Commission on Remote Sensing of the International Association of Hydrological Sciences (IAHS) and as a member of the Netherlands Science Organization (NWO VIDI & NWA) committees for earth and life sciences. He was also the chairman of the Boussinesq Center for Hydrology and the national representative of the Netherlands in IAHS. Most recently he severed on the ESA L-band SAR mission (ROSE-L) Mission Advisory Group (MAG) in 2018-2019 (Phase AB-1).

Bob Su was also appointed as guest professor at Changan University in Xian and Foreign Evaluation Expert of the Chinese Academy of Sciences. He currently serves on the World Climate Research Programme GEWEX Scientific Steering Group (SSG).

Bob Su provided leadership and direction to education in the Department of Water Resources and renewed the Water Resources and Environmental Management MSc course with emphases on in-situ and satellite observation of water cycle processes, numerical modeling and data assimilation. He has led the ESA TIGER capacity building facility (2007-2012) that supports African scientists and practitioners in managing water resources using earth observation techniques and data. He currently leads the ESA Dragon advanced training courses (2005-present) that provide training for PhD and postdocs researchers in using advanced Earth observation for atmosphere, ocean and land research and applications. He serves also on the Committee on Space Research (COSPAR) Capacity Building panel.

He supervises PhD students and postdocs and lectures in water resources and environmental management. He has graduated 35 doctorates and currently supervises 13 PhD candidates (Prajwal Khanal; Enting Tang; Jiangtao Cai; Ting Duan; Zengjing Song; Qianqian Han; Yunfei Wang; Anne van Gijsel; Mengna Li; Pei Zhang; Sammy Njuki; Jan Hofste; Donald Rwasoka).

Bob Su has directed and participated as Coordinator, Principal Investigator and Co-PI, 53 externally funded contract research projects by EU, ESA, KNAW, NWO and other agencies. Ongoing projects are:

(53)  PI: WUNDER-Water Use and Drought Ecohydrological Responses of Agricultural and Nature Ecosystems in the Netherlands - Towards Climate-Robust Production Systems and Water Management. NWO KIC (TUD, WU, HAS, Planet, Deltares, WEnR, HKV+ stakeholders, 2022-2028) (€ 1,516,238)

(52) CO-I: EcoExtreML: Accelerating Process Understanding for Ecosystem Functioning under Extreme Climates with Physics-Aware Machine Learning. NL eScience Center (PI: Y. Zeng, 2021-2025) (€ 253,000)

(51) PI: MINERVA: MIcrowaves for a New Era of Remote sensing of Vegetation for Agricultural monitoring. NWO PIPP (Partnerships for space Instruments & Applications Preparatory Programme) (TUD, WU, + stakeholders, 2020-2023) (€ 155,373, plus bench fee)

(50) PI: CLIMATE-Pan-TPE: Monitoring and Modelling Climate Change in Water, Energy and Carbon Cycles in the Pan-Third Pole Environment. ESA-MOST Dragon Programme IV (Young scientist, 2020-2024) (ID.58516, € 50,000)

(49) PI: iAqueduct: An integrative information aqueduct to close the gaps between global satellite observation of water cycle and local sustainable management of water resources, EU ERA-net Water JPI, 2019-2022 (Co-Is: Y. Zeng, Uni Twente; F. Francés, Uni Politecnic Vallencia; G. Vico, Swedish Uni Agr Sci., S. Manfreda, Uni Basilicata; B. Tóth, Hungary Academy Sci; N. Romano, Uni Naples; E. Ben-Dor, Tel Avis Uni) (total budget: 1,247,018 EUR; NWO ENWWW.2018.5, € 262,755)

Scientific Achievements: Bob Su and his research group aim at advancing our knowledge in the water, energy and carbon processes and their interactions with climate, ecosystem and humans in the earth system. Our activities focus to improve the quality of EO products and the fidelity and prediction capabilities of hydrometeorological models by intensive data acquisitions on the ground and from space and by advancing EO based hydrometeorological modeling and ensemble-algorithms. Our specific achievements are in the following fields.

1. Remote sensing and numerical modelling of land surface processes and land-atmosphere interactions

The author has created a research programme of quantitative remote sensing and in-situ observation network for land surface processes, land-atmosphere interactions and collected first-hand data and information on remote sensing and surface processes in Europe, Asia and Africa, and developed and improved numerical models.

• Systematic analyses of the hydrological and climatic changes over the Tibetan Plateau and its interaction with the Asian monsoon have been conducted (Su et al. 2013, JGR; Zheng et al. 2016, JGR).
• An observation network of soil moisture and soil temperature on the Tibetan Plateau (Tibet-Obs) has been established for validating satellite data, numerical model outputs and for developing data merging methods and data products (Su et al. 2011, HESS; Zeng et al. 2016, RS). The Tibet-Obs serves as calibration and validation sites for ESA’s SMOS and NASA’s SMAP satellite missions. An L-band radiometer (ELBARA III provided by the European Space Agency for SMOS validation) has been in operation since 2016 (Zheng et al., 2017, TGRS; Su et al., 2020, SciData; Zhao et al., 2021, JRS) and a scatterometer was in operation in 2017-2018 at the Maqu site of Tibet-Obs (Hofste et al., 2018, IGARSS; Hofste et al., 2021, ESSD).
• A similar observation network of soil moisture and soil temperature has also been established in Twente region in the Netherlands (Dente et al. 2012, Sensors; van der Velde et al., HESS).
• Three EO flux validation and calibration observatories have been established, including the Speulderbos Flux Observatory in 2006 (Su et al., 2009), the Enschede Urban hydroclimate Observatory in 2017, and the East African Monsoon Observatory Networks in Naivasha in 2012 (Odongo et al., 2016, Ecohydrology) and in Masai Mara in 2017.

These networks provide essential data and process knowledge for advancing remote sensing and numerical modeling of land surface processes and land-atmosphere interactions.

2. Climate data records for climate services

The author initiated the European Union funded Copernicus research project - Coordinating Earth Observation Data Validation for Reanalysis for Climate Services (CORE-CLIMAX, http://www.coreclimax.eu) which aimed to substantiate how Copernicus observations and products can contribute to climate change analyses. CORE-CLIMAX assessed the European capability to provide climate data records (CDRs) of essential climate variables (ECVs), prepared a structured process to derive CDRs, developed a harmonized approach for validating essential climate variable CDRs, identified the integration of CDRs into the reanalysis chain, and formulated a process to compare the results of different reanalysis techniques. With respect to the Copernicus Climate Change Service (C3S), the systematic application and further development of the CORE-CLIMAX system maturity matrix (SMM) and the application performance metric (APM) were strongly endorsed for future implementations of C3S.

CORE-CLIMAX has set a new paradigm for data handling and data quality regarding the development of climate services (Su et al. 2018, BAMS; Zeng et al. 2017, JAG; Zeng et al. 2019, RS).

3. Observation of global water cycle

Reliable modeling of water cycle and climate interactions requires the availability of water cycle data, such as precipitation, evaporation, soil moisture and groundwater fluxes from basin to global scales.

The author coordinated the ESA WACMOS project in which the first version of global water cycle products based on ESA EO data was generated (Su et al. 2016, JAG), including global radiation, precipitation, evaporation and soil moisture.

• The development of a set of long-term global surface flux and evaporation data products, as a contribution to the International GEWEX programme, has played a key role in the study of the hydrospheric balance of mass and energy, the interaction of land-atmosphere and its impact on the monsoon (Chen et al., 2014, ACP; Chen et al., 2019, AFM; Chen et al., 2021, JGR-Atmospheres);
• The developed first version of the WACMOS soil moisture led to the production of the ESA Climate Change Initiative Soil Moisture Essential Climate Variable (http://www.esa-soilmoisture-cci.org/node/93).

4. Theory for retrieval of turbulent heat fluxes and evaporation

Using remote sensing technology, the author developed the theory and method for retrieving surface turbulent heat flux and evaporation under heterogeneous surface conditions (the SEBS model - Surface Energy Balance System, Su 2002, HESS, currently cited 2116 times in google scholar) and experimentally studied the transfers of water vapor, energy, carbon dioxide between land and atmosphere (Su et al. 2008, IJRS; Su et al., 2009, HESS; Chen et al., 2014, ACP; Chen et al., 2019, JGR).

5. Simulating radiative transfer, photosynthesis and energy fluxes

Investigating the relationships among climate, vegetation functioning and vegetation structure as related to the water cycle components requires a combination of earth observation, field measurements and simulation at leaf, whole-tree, canopy and landscape scales.

The author initiated a major project funded by the Netherlands Scientific Organisation (NWO) - Modeling radiation, heat and mass (water vapour and carbon) exchanges at the land-atmosphere interface using multi-angular optical and thermal measurements. The major achievement was the development of the SCOPE model for simulating radiative transfer, photosynthesis and energy fluxes in vegetation and soil (van der Tol et al., 2009, BG). Currently the SCOPE model is used in the European Space Agency (ESA) Earth Explorer 8 FLEX satellite mission.

6. Unravelling climate and human impacts in hydrology and water resources

Understanding the role of the terrestrial hydrosphere in Earth’s climate system relies on analysing long term EO data products and model predictions of hydro-climatic variables, such as radiation, precipitation, evaporation, soil moisture, clouds, water vapor, surface water and runoff.

The major contributions are the development of a method by use of satellite and reanalysis product to unravel climatic and human drivers in river basin hydrology and water resources (Su et al., 2018, BAMS; Huang et al., 2015, WRR) and the development of downscaling methods for water cycle products for water management (Su et al., 2019, Water).

7. Coupled Simultaneous Transfer of Energy, Mass and Momentum in Unsaturated Soil as a component of earth system model

Current Earth system models lack detailed description of coupled transfer of energy, mass and momentum, in particular with respect to the unsaturated soil and the vegetation rooting systems, resulting in deficiency in model simulation and vast difference in outputs by different models.

The author has overseen the development of the Coupled Simultaneous Transfer of Energy, Mass and Momentum in Unsaturated Soil as a component of earth system model (STEMMUS, Zeng et al. 2011, JGR, WRR, 2013; Zeng and Su, 2013, WRR; Yu et al., 2016, HESS; Yu et al., 2018, JGR). The coupled STEMMUS-SCOPE model enables to deal with plant hydraulics in drought stress and is a major contribution to Earth System Science and modelling (Wang et al., 2021, GMD)

8. Modelling microwave signature of land surface and retrieval of soil moisture

The effective use and processing of passive and active microwave observation of the Earth with satellite e.g. by ESA’s SMOS and NASA’s SMAP satellite, require a fundamental understanding of the emission and scattering processes of the land. The author proposed the effective roughness slope concept (Su et al. 1997, IJRS) for the retrieval of surface soil moisture and pioneered the simultaneous use of passive and active microwave signal to constrain the retrieval (Dente et al. 2014, RSE; Wang et al. 2016, RSE, 2019, JAG) and to simulate the radiometric observations (Zheng et al., 2017, TGRS).

In the NWO funded project - Modelling Freeze-Thaw Processes with Active and Passive Microwave Observations, a forward simulation system is developed by coupling a physical process model (the Noah-A model) and a microwave radiative transfer model (Tor Vergata model) that is capable to accurately simulate radiometric (in situ and satellite) observation signal by using meteorological input (Zheng et al., 2017, TGRS; Lv et al., 2014, RSE, 2016, RSE, 2018, RS, 2019, IEEE TGRS). This is a significant advance in the field of microwave remote sensing of land surface and soil moisture.

The system is currently being upgraded for simulation of multi-frequency active and passive microwave observations of the land surface (Hong, et al. 2021, JRS).