Contributors: Jacqueline Bannwart (University of Zurich), Inés Dussailan (University of Zurich), Frank Paul (University of Zurich), Michael Zemp (University of Zurich)
Issued b: UZH / Ines Dussaillant
Date: 07/08/2023
Ref: C3S2_312a_Lot4.WP3-SQAD-GL-v1_202301_MC_System_Quality_Assurance_i1.1
Official reference number service contract: 2021/C3S2_312a_Lot4_EODC/SC1
History of modifications
List of datasets covered by this document
Related documents
Acronyms
General definitions
Brokered Product: A brokered product is a pre-existing dataset to which the Copernicus Climate Change Service (C3S) acquires a license, for the purpose of including it in the Climate Data Store (CDS).
Geodetic method: Any method for determining mass balance by repeated mapping of glacier surface elevations to estimate the volume balance; cartographic method and topographic method are synonyms. The conversion of elevation change to mass balance requires information on the density of the mass lost or gained, or an assumption about the time variations in density (Cogley et al., 2011).
Glaciological method: A method of determining mass balance in-situ on the glacier surface by measurements of accumulation and ablation, generally including measurements at stakes and in snow pits; direct method has long been a synonym. The measurements may also rely on depth probing and density sampling of the snow and firn, and coring. They are made at single points, the results from a number of points being extrapolated and integrated to yield the surface mass balance over a larger area such as an elevation band or the entire glacier (Cogley et al., 2011).
Elevation change: Vertical change in glacier surface elevation (altitude), typically derived from two elevation measurements, adjusted if necessary for the difference of their respective datum surfaces, at the same (or nearly the same) horizontal coordinates (Cogley et al., 2011).
Scope of the document
This document is the System Quality Assurance Document (SQAD) for the Copernicus glacier change service. This service provides to the Climate Data Store (CDS) a global gridded annual glacier mass-change product corresponding to the latest version of the Fluctuations of Glaciers (FoG) database brokered by the World Glacier Monitoring Service (WGMS).
The SQAD describes the C3S data production system for glacier changes. It describes how the data processing system is organised in general and how product updates are implemented in the CDS and FoG databases. Glacier distribution and glacier change service products are developed in parallel at the WGMS, having a similar system organization. For a better overview, the figures in this document also include the datasets provided by the glacier distribution service, glacier area product (see RD1) but only the change product is discussed.
Executive summary
This document provides an overview on the principal set-up of the data production system elements and interfaces and how the various contributors feed into the existing databases and the CDS. To better understand the overall data processing workflow for the Essential Climate Variable (ECV) Glaciers, we describe the set-up for the glacier change and area products collectively, but only the glacier change system is discussed in this document.
The glaciological community provides glacier change data directly to the WGMS after a yearly call-for-data. Improvements and quality checking of the newly acquired glacier observations are performed by the University of Zurich (UZH) team and integrated in the FoG database. The glacier change product Climate Data Record (CDR) is then produced using the latest version of the FoG database. The data processing for the glacier change product is mostly performed by individual analysts on standard desktop computers or servers, with operational processing chains written in Python language.
Upgrade cycle implementation procedure takes place also on a yearly basis, following the FoG database update cycle. New versions of the glacier change product CDR are reprocessed every year directly after the latest release of the FoG database has been published by the WGMS.
This document includes a description of the Copernicus User Support Jira Service Desk System to answer enquiries specific to their products, by direct interaction with the user through the Jira helpdesk.
1. System overview
1.1. System elements and interfaces
To better understand the overall data processing workflow for the Essential Climate Variable (ECV) Glaciers, we describe the set-up for the glacier change and area products collectively in Figure 1. Both products provided by Copernicus Climate Change Service (C3S) via the Climate Data Store (CDS) are created by the team at the University of Zurich (UZH) and the global science community (light blue cloud in Figure 1).
For the development of the CDS glacier change product, the global science community involved consist of national correspondents and principal investigators of the World Glacier Monitoring Service (WGMS) network providing glacier change observation from the glaciological and geodetic methods to the Fluctuations of Glaciers (FoG) database. The community provides their data directly to the WGMS after a yearly call-for-data. Improvements and quality checking of the newly acquired glacier observations are performed by the UZH team and integrated in the WGMS internal database. A validated, homogenized and updated FoG database version is then released by the WGMS once per year. The glacier change Climate Data Record (CDR) uses the latest version of the FoG database as input data.
We define our global gridded annual glacier mass-change product as the glacier change CDR with the public version name corresponding to the latest release of the FoG database (gridded FoG 1 and 2 in Figure 1). A new version of the glacier change CDR is provided once per year after the latest release of the FoG database has been published by the WGMS. We note that since the FoG database is updated only once per year (around August/September), the glacier change product is produced as well only once per year, considering all updates, data corrections and improvements of the glacier datasets at once. Because we provide a fully new CDR on a yearly basis, there is basically no ‘’interim’’ state (ICDR) of the glacier change product.
Figure 1: Schematic overview of the C3S Data Production System for glaciers. The glacier inventory and glacier change production systems are green, existing data repositories are blue and forwarding of CDRs to the EODC database and the CDS is shown in grey. Note that only the glacier change side is discussed in this document. Glacier inventory, GLIMS (Global Land Ice Measurements from Space) and RGI (Randolph Glacier Inventory) are relevant for the glacier Area product and are discussed in [RD1].
1.2. Hardware, supercomputers and cloud computing
Data processing for the glacier change product is performed by individual analysts on standard desktop computers or servers. There is no need for special hardware, supercomputers or cloud computing. Processing chains are operational and written in Python language.
2. Upgrade cycle implementation procedure
As mentioned in Section 1.1, the update cycle for the FoG database is every 12 months. These are listed in the quarterly reports (provided as internal contractual documents). The community is informed about the updates of the CDRs via the cryolist email distribution list.
Figure 2 depicts the system set up steps, timelines and upgrade cycle of the glacier product CDR. First, the new elevation and mass change observations are collected by the UZH-WGMS team after the yearly call for data (ICDRs – in green). Secondly, the data is checked, integrated in the FoG database and the new version of the glacier product is produced (CDRs – in blue). Finally, the CDR is forwarded to the C3S Climate Data Store (in grey). After one cycle ends, a new cycle begins.
Figure 2: Principle set up steps and timeline of glacier change product. Data production step (ICDRs – in green): new elevation and mass change observations (dz/dt) are collected by UZH-WGMS. Data integration step (CDRs – in blue): new observations are integrated in the respective databases and the glacier product is produced. C3S CDS step (grey): the glacier product is forwarded to the C3S Climate Data Store).
3. Procedures for reprocessing CDR's
The FoG database is being constantly extended with the latest datasets becoming available (e.g. glaciological and geodetic observations). New versions of the mass and elevation change from the FoG database are released each year (as described in Section 1.1 above and illustrated in Figure 2). New versions of the glacier change CDR are reprocessed on a yearly basis after the latest release of the FoG database has been published by the WGMS.
We expect the glacier change product to be improved with every new observation: longer time series of glaciological observations, and better resolved geodetic observations. Improvements to the processing chain will be addressed if needed.
4. System maintenance and system failures
The chance of system failure is small, as the system is globally distributed rather than centralised. It does not have a core and is, thus, difficult to stop. Moreover, key processing algorithms are very simple and can be used in various processing environments.
5. User support
The glacier change service has a team account with the Copernicus User Support (CUS) Jira Service Desk System, to provide level 2 user support, i.e. to answer enquiries specific to their products, by direct interaction with the user through the Jira helpdesk. Once a request is sent, the Copernicus User Support Service team at European Centre for Medium-Range Weather Forecasts (ECMWF) will handle the requests within 8 hours (level 1).
For any scientific and special enquiries that cannot be answered by the CUS team at ECMWF or addressed to the Knowledge Base, the request will be forwarded to the Copernicus User Support Specialists (level 2).
Enquiries forwarded to the Copernicus User Support Specialist team will be acknowledged within 3 working days (target 100%) and a notification sent to the user. In case of specific scientific issues, the enquiries will be channelled to the ECV and data specialist of the C3S2_312a_Lot4 project and should be resolved within 3 working weeks (target 85%). In each quarter, we aim for User Support satisfaction scoring 3 in 90% of all voluntary based feedbacks by users, with 1 (very unsatisfied) to 5 (very satisfied). We will also list the number of tickets in the Quarterly Report.
All products made by the team, including the glacier change and area products, are handled by the same system.
References
Cogley, J. G., Hock, R., Rasmussen, L. A., Arendt, A. A., Bauder, A., Braithwaite, R. J., et al. (2011). Glossary of Glacier Mass Balance and Related Terms. IHP-VII Technical Documents in Hydrology No. 86. IACS Contribution No. 2 UNESCO-IHP, Paris.
