Comparison of open access global climate services for hydrological data

Abstract

There is a high demand for openly accessible hydroclimatic data for climate change adaptation. Different data sources are available, however, discrepancy between the data can confuse users and should be evaluated and explained. This study, investigates how climate impact indicators (CIIs) developed for global users in the Copernicus Climate Change Service (C3S) are comparable to other openly available global data for water and climate. We found that, for temperature, datasets are comparable and climate impacts are thus considered robust. Important discrepancies arise in the precipitation indicators. Of the CIIs analysed in this study, the hydrological CIIs differ most so they should be used with care. These differences are probably caused by model uncertainty (hydrological model, HM; global climate model, GCM), ensemble size and model selection. A HM ensemble, as well as a GCM ensemble combined with improved model performance and selection criteria, should be used to ensure high-quality global water and climate services.

Large-Scale Hydrological and Sediment Modeling in Nested Domains under Current and Changing Climate

“…However, different number of GCMs used in different studies together with other assumptions, e.g., on reference period of bias-adjustment methods make the comparison of the impacts difficult. Merks et al (2020) found large differences between both current discharges and future changes projected with WW-HYPE using the full ensemble of 18 GCMs and those simulated with the variable infiltration capacity (VIC) model (Liang et al 1994;van Vliet et al 2015). The differences were partly attributed to propagation of change in areas with low annual precipitation and discharge, where it is difficult to predict runoff, and partly to differences between the models themselves (hydrological versus land-surface model), the evapotranspiration routines, and GCM ensembles.…”

“…A variety of models can be strategically chosen to explore these key processes as well as a parameter space for the model calibration. Model performance also affects the agreement among the hydrological models (Merks et al 2020). A standardized evaluation, e.g., over smaller regions, would further help in these evaluations.…”

Designing a Climate Service for Planning Climate Actions in Vulnerable Countries

“…A quality assured production chain which is frequently used in climatic services (including hydro services; [17]) was implemented to produce Climate Indicators (CI) and Water Indicators (WI) from Essential Climate Variables (ECV) available in the Climate Information platform (Figure 1). The production follows a rigorous quality assurance protocol developed in previous projects and adjusted to fit the current needs.…”

“…The ensemble of CMIP5 models previously used in a Copernicus Climate Change Service Sectoral Information System (C3S SIS, [17]) was also used to provide a complete global coverage. The ensemble was modified to fit the current requests (different reference period (1981-2010), which differs from C3S (1971-2000)); the ensemble is also available in Appendix A.…”

“…The validity of spatial patterns in hydrological variables was assessed through visual inspection of mapped aggregates (averages, sums) of WW-HYPE output variables. Values of the model variables at selected spatial points, e.g., large river outlets, are semi-quantitatively assessed through comparison with expected ranges based on external data, e.g., observations or previous model results (runs with CMIP5, [17]), to make sure values are within a reasonable range.…”