JWG C.7: Satellite geodetic data assimilation for hydro-climate research

Chair: Mehdi Khaki (Australia)
(Affiliation: Commission 2, GGOS)

Introduction

The recent advancements in the space geodetic techniques have gained a lot of attention for improving our understanding of Earth's climate system and its hydrology. Traditionally, various types of models such as hydrologic and atmospheric models have been used for modelling/simulating and predicting hydro‐meteorological processes at regional and global scales. Nevertheless, due to various sources of uncertainties such as imperfect modelling, data limitations on both temporal and spatial resolutions, their errors, as well as limited knowledge about empirical model parameters, the accuracy of model simulations can be degraded. Assimilation of satellite geodetic data such as satellite gravimetry, satellite radar and radiometer measurements, synthetic-aperture radar (SAR) and radar interferometry data, and satellite altimetry has been shown to be effective for improving the models’ performance and their forecasting skills. This allows us to better study, for example, water resources and their distributions, mass variations and balance, extreme events such as droughts and floods, ice transfer, and help to adapt to long-term environmental challenges posed by climate changes on continental scales.

Data assimilation (DA) facilitates this data integration by constraining the models’ simulations based on observations and error associated with them. The method has become more popular with the advent of the space era since scientific observational methods were not limited any more to terrestrial only and offer high spatiotemporal resolution data with global coverage. Specifically, the application of satellite geodetic measurement has been proven to successfully improve various models such as atmospheric and oceanic models, hydrological models and also coupled (e.g., land-atmosphere) systems. For example, the Gravity Recovery And Climate Experiment (GRACE) terrestrial water storage (TWS) data has been used to enhance land surface model performance. Satellite radar altimetry data over the ocean has been used for enhancing oceanic models. Altimetry-derived surface water over land has been recently applied for improved routing as well as rainfall-runoff estimates. Satellite soil moisture, e.g., from Soil Moisture and Ocean Salinity (SMOS) radiometer and Soil Moisture Active Passive (SMAP) has been used for hydrologic DA and more recently for land-atmosphere coupled DA to better study soil moisture feedback to atmospheric components. The use of space geodetic techniques for DA can be further extended with the development of new missions such as NASA's Surface Water and Ocean Topography (SWOT) global surface water, GRACE Follow-on, and Cyclone Global Navigation Satellite System (CYGNSS) soil moisture. Therefore, satellite geodetic DA has a great potential in hydro-climate studies and it requires more concentrations within the geodesy community. The main objective of establishing this working group within IAG is to bring together people with this expertise to share their knowledge, address the current challenges, and draw more attention to the application of geodetic techniques for DA. 

Objectives

• To investigate the contributions of space geodetic DA in Earth systems.
• To develop and analyze theoretical and numerical methods for the efficient integration of satellite measurements with models.
• To better analyze model-data uncertainties in satellite DA and their influence on the model’s simulations.
• To explore the application of satellite DA for model calibrations
• To investigate the application of new geodetic platforms for DA objectives.

Program of Activities

• To actively participate in geodetic meetings and promote space geodetic DA, and to monitor current progress and identify challenges.
• To share efforts, ideas, and information regarding the working group objectives.
• To organize related sessions at international events.
• To provide opportunities for more collaborations between group members (within the joint working groups) on satellite DA and publishing important findings.
• To create a web page with information relevant to the working group, bibliographic list of publications, and available research opportunities to also share significant DA outcomes with the public.

Members

• Joseph Awange (Australia)
• Luca Brocca (Italy)
• Harrie-Jan Hendricks Franssen (Germany)
• Ibrahim Hoteit (Saudi-Arabia)
• Jayaluxmi Indu (India)
• Gabrielle J. M. De Lannoy (Belgium)
• Hamid Moradkhani (USA)
• Christian Massari (Italy)
• John T. Reager (USA)
• Jan Saynisch (Germany)
• Ashkan Shokri (Australia)
• Natthachet Tangdamrongsub (USA)
• Yoshihide Wada (Austria)
• Benjamin Zaitchik (USA)