B.6

Due to the fundamental role of Groundwater (GW) in the Earth's water and energy cycles, GW has been declared as an Essential Climate Variable (ECV) by GCOS, the Global Climate Observing System. However, within Copernicus - the European Earth Observation Programme - there is no service available yet to deliver data on this fundamental resource, nor is there any other data source worldwide that operationally provides information on changing groundwater resources in a consistent way, observation-based, and with global coverage. Hence, the Global Gravity-based Groundwater Product (G3P) aims at developing a satellite-based groundwater storage (GW) data set as a new product for the EU Copernicus Climate Change Service. G3P capitalizes from the unique capability of GRACE and GRACE-FO satellite gravimetry as the only remote sensing technology to monitor subsurface mass variations, and from other satellite-based water storage products to provide a data set of groundwater storage change for large areas with global coverage. G3P is obtained by using a mass balance approach, i.e., by subtracting satellite-based water storage compartments (WSCs) such as snow water equivalent, root-zone soil moisture, glacier mass, and surface water storage from GRACE/GRACE-FO monthly terrestrial water storage anomalies (TWSA). For a consistent subtraction of all individual WSCs from GRACE-TWSA, the individual WSCs are filtered in a similar way as GRACE-TWSA, where optimal filter types were derived by analyses of spatial correlation patterns. G3P groundwater variations are provided for almost two decades (from 04-2002 to 12-2020), with monthly resolution, and at a 0.5-degree spatial resolution globally. In this contribution, we also illustrate some results of the G3P data set and of its uncertainties, as well as its evaluation by independent in-situ groundwater observation.

This study has received funding from the European Union’s Horizon 2020 research and innovation programme for G3P (Global Gravity-based Groundwater Product) under grant agreement nº 870353.

How to cite: Sharifi, E., Güntner, A., Haas, J., Dorigo, W., Jäggi, A., and Ruz Vargas, C. and the G3P team: The Global Gravity-based Groundwater Product (G3P), GRACE/GRACE-FO Science Team Meeting 2022, Potsdam, Germany, 18–20 Oct 2022, GSTM2022-79, https://doi.org/10.5194/gstm2022-79, 2022.

Several continental regions on Earth are getting wetter, while others are drying out not only in terms of precipitation but also measured by the increase or decrease in surface water, water stored in the soils, the plant root zone, and in groundwater. Drying and wetting as seen in terrestrial e.g. rainfall or soil moisture, GRACE/GRACE-FO and remote sensing data are generally ascribed to combined effects of global warming due to greenhouse gas forcing, natural variability, and anthropogenic modification of the water cycle. Existing climate models that account for these effects fail to explain observed patterns of hydrological change sufficiently. Contrary to common beliefs, observations also do not support a simple dry-gets-dryer and wet-gets-wetter logic. Instead, the observed trends, in total water storage TWSA but also precipitation, soil moisture, or river discharge, differ considerably from a simplified logic, and characteristic regions not necessarily match each other. The new collaborative research centre CRC1502, funded by the German Research Foundation and run at the Universities Bonn, Cologne, Göttingen and the FZ Jülich and DWD, targets at closing this gap of understanding. To better comprehend the origin of these patterns, we have started to build a modelling framework that explains past observations as realistically as possible (reanalysis), accounts for potential drivers of change that may have been understudied in the past, and that can predict future changes.

Climate change and anthropogenic interactions are already affecting the frequency of extreme events such as heat waves, droughts and floods. More intense, more frequent, and longer-lasting heat waves are projected for the 21st century; surface and ground water buffer the effects of such heat waves, but large-scale drying may amplify them to an as yet unknown extent. Societal, environmental and economic consequences include increased risk in agricultural production, threats to agricultural productivity and food security and increasing health risks. This CRC proposes the hypothesis that humans – through several decades of land use change, and intensified water use and management – have caused persistent modifications in the coupled land and atmospheric water and energy cycles. These human-induced modifications contribute considerably, compared to greenhouse gas forcing and natural variability, to the observed trends in water storage at the regional scale. We hypothesize that land management and land and water use changes have modified the regional atmospheric circulation and related water transports. These changes in the spatial patterns of the water balance are hypothesized to have created and magnified imbalances that lead to excessive drying or wetting in more remote regions. We test this hypothesis for Europe in the 1st phase. In later phases, we evaluate the transferability of our approach for regions with different environmental conditions. We propose to develop evidence-based sustainability criteria for land and water use activities.

The presentation will introduce the objectives of the new CRC and the approaches that we will pursue, including how we will utilize GRACE/GRACE-FO data in combination with other remote sensing data and with coupled modelling.

How to cite: Kusche, J. and the CRC1502 Team: GRACE/GRACE-FO, remote sensing, land use modelling, and coupled simulations for understanding the causes of regional climate change, GRACE/GRACE-FO Science Team Meeting 2022, Potsdam, Germany, 18–20 Oct 2022, GSTM2022-36, https://doi.org/10.5194/gstm2022-36, 2022.

Aquifer recharge is an essential component of sustainable groundwater management plans in California. The Sierra Nevada Mountain’s snow pack during winter months is believed to be important for aquifer recharge and studies support that a significant amount of  late winter to spring snow melt infiltrates as mountain front and mountain block recharge. Details of the connections between the Sierra’s mountain groundwater recharge processes to the adjacent Central Valley basin aquifer remain unclear. With the purpose to achieve a better understanding of this connection, we investigate geodetic, hydrologic, and climate datasets. These include total water storage variations from GRACE JPL Mascons and composite hydrology to quantify groundwater storage changes in the Central Valley. We study seasonal variations in this and other groundwater related observables, after isolating them through wavelet multi-resolution analysis of all datasets. The results for valley wide timing and amplitude of the various datasets provide insight into seasonal recharge mechanisms and they indicate that the Sierra Nevada Mountains play a more prominent role in the recharge of California’s deep Valley aquifers than previously assumed. We further support this finding through process-based model experiments. The time that is needed for vertical pressure propagation from the Sierra Nevadas to deep aquifer layers in the Valley is consistent with observed time difference between occurance of maximum water availability for groundwater recharge in the Sierra Nevadas and that of maximum groundwater levels in deep aquifer layers. Based on our findings, we suggest that models used for groundwater management plans need to include the Sierra Nevada Mountains for accurate predictions of human and climate change impacts on the Central Valley’s groundwater resources.

How to cite: Werth, S., Shirzaei, M., and Carlson, G.: The importance of Sierra Nevada Mountain snowpack to Central Valley aquifer recharge, GRACE/GRACE-FO Science Team Meeting 2022, Potsdam, Germany, 18–20 Oct 2022, GSTM2022-82, https://doi.org/10.5194/gstm2022-82, 2022.

PO.DAAC has pioneered data migration to the NASA Earthdata Cloud (Amazon Web Service – AWS) beginning in January 2021. Today, the entire active data collections archived at PO.DAAC have been successfully migrated. The migration effort includes not just the datasets, but also the access tools/services and documentation, together forming the new PO.DAAC-in-Cloud (POCLOUD) data ecosystem, which brings challenges but also opportunities to the users with many new capabilities. In the new cloud paradigm, the traditional PO.DAAC data search portal will continue to serve as the main data discovery platform for its datasets. In addition, NASA has designed an Earthdata search portal for discovering the earth science datasets and granules across all 12 NASA data centers. To access the POCLOUD data, most of the on-premise tools and services are (will be) made available except PO.DAAC Drive, which will be retired after the cloud data migration. Currently, the data direct download (https), AWS S3 buckets access, OPeNDAP, the Level 2 subsetting tool HiTIDE, and the visualization tool SOTO have been added to POCLOUD datasets. A collection of Harmony APIs, which are a common family of services for discovering , accessing and transforming the Earth observation data in the cloud from different NASA data centers, are also made available to most POCLOUD data, including services for subsetting, Zarr reformatting, and regridding. Users are encouraged to find helpful tutorials, demos and recipes from PO.DAAC Cloud Data page, such as, the powerful and efficient podaac-data-subscriber script, tutorials on OPeNDAP, Amazon S3 bucket direct access, and many more cloud data applications.

How to cite: Li, W.-H. and Finch, C.: GRACE (-FO) data discovery, access and download from NASA Earthdata Cloud, GRACE/GRACE-FO Science Team Meeting 2022, Potsdam, Germany, 18–20 Oct 2022, GSTM2022-20, https://doi.org/10.5194/gstm2022-20, 2022.