The benefits of spatial resolution increase in global simulations of the hydrological cycle evaluated for the Rhine and Mississippi basins

Abstract. To study the global hydrological cycle and its response to a changing climate, we rely on global climate models (GCMs) and global hydrological models (GHMs). The spatial resolution of these models is restricted by computational resources and therefore limits the processes and level of detail that can be resolved. Increase in computer power therefore permits increase in resolution, but it is an open question where this resolution is invested best: in the GCM or GHM. In this study, we evaluated the benefits of increased resolution, without modifying the representation of physical processes in the models. By doing so, we can evaluate the benefits of resolution alone. We assess and compare the benefits of an increased resolution for a GCM and a GHM for two basins with long observational records: the Rhine and Mississippi basins. Increasing the resolution of a GCM (1.125 to 0.25∘) results in an improved precipitation budget over the Rhine basin, attributed to a more realistic large-scale circulation. These improvements with increased resolution are not found for the Mississippi basin, possibly because precipitation is strongly dependent on the representation of still unresolved convective processes. Increasing the resolution of the GCM improved the simulations of the monthly-averaged discharge for the Rhine, but did not improve the representation of extreme streamflow events. For the Mississippi basin, no substantial differences in precipitation and discharge were found with the higher-resolution GCM and GHM. Increasing the resolution of parameters describing vegetation and orography in the high-resolution GHM (from 0.5 to 0.05∘) shows no significant differences in discharge for both basins. A straightforward resolution increase in the GHM is thus most likely not the best method to improve discharge predictions, which emphasizes the need for better representation of processes and improved parameterizations that go hand in hand with resolution increase in a GHM.

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An evaluation of the importance of spatial resolution in a global climate and hydrological model based on the Rhine and Mississippi basin

10.5194/hess-2017-473 ◽

2017 ◽

Cited By ~ 1

Author(s):

Imme Benedict ◽

Chiel C. van Heerwaarden ◽

Albrecht H. Weerts ◽

Wilco Hazeleger

Keyword(s):

High Resolution ◽

Spatial Resolution ◽

Large Scale ◽

Climate Models ◽

Hydrological Cycle ◽

Global Climate ◽

Global Scale ◽

Global Climate Models ◽

Convective Processes ◽

Parameter Values

Abstract. The hydrological cycle of river basins can be simulated by combining global climate models (GCMs) and global hydrological models (GHMs). The spatial resolution of these models is restricted by computational resources and therefore limits the processes and level of detail that can be resolved. To further improve simulations of precipitation and river-runoff on a global scale, we assess and compare the benefits of an increased resolution for a GCM and a GHM. We focus on the Rhine and Mississippi basin. Increasing the resolution of a GCM (1.125° to 0.25°) results in more realistic large-scale circulation patterns over the Rhine and an improved precipitation budget. These improvements with increased resolution are not found for the Mississippi basin, most likely because precipitation is strongly dependent on the representation of still unresolved convective processes. Increasing the resolution of vegetation and orography in the high resolution GHM (from 0.5° to 0.05°) shows no significant differences in discharge for both basins, because the hydrological processes depend highly on other parameter values that are not readily available at high resolution. Therefore, increasing the resolution of the GCM provides the most straightforward route to better results. This route works best for basins driven by large-scale precipitation, such as the Rhine basin. For basins driven by convective processes, such as the Mississippi basin, improvements are expected with even higher resolution convection permitting models.

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An evaluation of the importance of spatial resolution in global climate and hydrological models based on the Rhine and Mississippi basins

10.5194/hess-2018-437 ◽

2018 ◽

Cited By ~ 1

Author(s):

Imme Benedict ◽

Chiel C. van Heerwaarden ◽

Albrecht H. Weerts ◽

Wilco Hazeleger

Keyword(s):

High Resolution ◽

Spatial Resolution ◽

Large Scale ◽

Climate Models ◽

Hydrological Cycle ◽

Global Climate ◽

Global Climate Models ◽

Hydrological Models ◽

Basin Scale ◽

Parameter Values

Abstract. To study the global hydrological cycle and its response to a changing climate, we rely on global climate models (GCMs) and global hydrological models (GHMs). The spatial resolution of these models is restricted by computational resources and therefore limits the processes and level of detail that can be resolved. We assess and compare the benefits of an increased resolution for a GCM and a GHM for two basins with long observational records; the Rhine and Mississippi basins. Increasing the resolution of a GCM (1.125° to 0.25°) results in an improved precipitation budget over the Rhine basin, attributed to a more realistic large-scale circulation. These improvements with increased resolution are not found for the Mississippi basin, possibly because precipitation is strongly depending on the representation of still unresolved convective processes. Increasing the resolution of vegetation and orography in the high resolution GHM (from 0.5° to 0.05°) shows no significant differences in discharge for both basins, likely because the hydrological processes depend highly on model parameter values that are not readily available at high resolution. Increasing the resolution of the GCM improved the simulations of the monthly averaged discharge for the Rhine, but did not improve the representation of extreme streamflow events. For the Mississippi basin, no substantial differences in precipitation and discharge were found between the two resolutions input GCM and the two resolutions GHM. These findings underline that there is no trivial route from increasing spatial resolution to a more accurately simulated hydrological cycle at basin scale.

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Large-scale features and evaluation of the PMIP4-CMIP6 <i>midHolocene</i> simulations

Climate of the Past ◽

10.5194/cp-16-1847-2020 ◽

2020 ◽

Vol 16 (5) ◽

pp. 1847-1872 ◽

Cited By ~ 7

Author(s):

Chris M. Brierley ◽

Anni Zhao ◽

Sandy P. Harrison ◽

Pascale Braconnot ◽

Charles J. R. Williams ◽

...

Keyword(s):

Large Scale ◽

Climate Models ◽

Hydrological Cycle ◽

Global Climate ◽

Coupled Model ◽

Global Climate Models ◽

Current Phase ◽

Model Intercomparison ◽

Global Mean Temperature ◽

Intercomparison Project

Abstract. The mid-Holocene (6000 years ago) is a standard time period for the evaluation of the simulated response of global climate models using palaeoclimate reconstructions. The latest mid-Holocene simulations are a palaeoclimate entry card for the Palaeoclimate Model Intercomparison Project (PMIP4) component of the current phase of the Coupled Model Intercomparison Project (CMIP6) – hereafter referred to as PMIP4-CMIP6. Here we provide an initial analysis and evaluation of the results of the experiment for the mid-Holocene. We show that state-of-the-art models produce climate changes that are broadly consistent with theory and observations, including increased summer warming of the Northern Hemisphere and associated shifts in tropical rainfall. Many features of the PMIP4-CMIP6 simulations were present in the previous generation (PMIP3-CMIP5) of simulations. The PMIP4-CMIP6 ensemble for the mid-Holocene has a global mean temperature change of −0.3 K, which is −0.2 K cooler than the PMIP3-CMIP5 simulations predominantly as a result of the prescription of realistic greenhouse gas concentrations in PMIP4-CMIP6. Biases in the magnitude and the sign of regional responses identified in PMIP3-CMIP5, such as the amplification of the northern African monsoon, precipitation changes over Europe, and simulated aridity in mid-Eurasia, are still present in the PMIP4-CMIP6 simulations. Despite these issues, PMIP4-CMIP6 and the mid-Holocene provide an opportunity both for quantitative evaluation and derivation of emergent constraints on the hydrological cycle, feedback strength, and potentially climate sensitivity.

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An Assessment of Land–Atmosphere Interactions over South America Using Satellites, Reanalysis, and Two Global Climate Models

Journal of Hydrometeorology ◽

10.1175/jhm-d-20-0132.1 ◽

2021 ◽

Vol 22 (4) ◽

pp. 905-922

Author(s):

Jessica C. A. Baker ◽

Dayana Castilho de Souza ◽

Paulo Y. Kubota ◽

Wolfgang Buermann ◽

Caio A. S. Coelho ◽

...

Keyword(s):

South America ◽

Large Scale ◽

Climate Models ◽

Hydrological Cycle ◽

Global Climate ◽

Atlantic Coast ◽

Global Climate Models ◽

Climate Projections ◽

Median Response ◽

Model Version

AbstractIn South America, land–atmosphere interactions have an important impact on climate, particularly the regional hydrological cycle, but detailed evaluation of these processes in global climate models has been limited. Focusing on the satellite-era period of 2003–14, we assess land–atmosphere interactions on annual to seasonal time scales over South America in satellite products, a novel reanalysis (ERA5-Land), and two global climate models: the Brazilian Global Atmospheric Model version 1.2 (BAM-1.2) and the U.K. Hadley Centre Global Environment Model version 3 (HadGEM3). We identify key features of South American land–atmosphere interactions represented in satellite and model datasets, including seasonal variation in coupling strength, large-scale spatial variation in the sensitivity of evapotranspiration to surface moisture, and a dipole in evaporative regime across the continent. Differences between products are also identified, with ERA5-Land, HadGEM3, and BAM-1.2 showing opposite interactions to satellites over parts of the Amazon and the Cerrado and stronger land–atmosphere coupling along the North Atlantic coast. Where models and satellites disagree on the strength and direction of land–atmosphere interactions, precipitation biases and misrepresentation of processes controlling surface soil moisture are implicated as likely drivers. These results show where improvement of model processes could reduce uncertainty in the modeled climate response to land-use change, and highlight where model biases could unrealistically amplify drying or wetting trends in future climate projections. Finally, HadGEM3 and BAM-1.2 are consistent with the median response of an ensemble of nine CMIP6 models, showing they are broadly representative of the latest generation of climate models.

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Global climatology and trends in convective environments from ERA5 and rawinsonde data

npj Climate and Atmospheric Science ◽

10.1038/s41612-021-00190-x ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Mateusz Taszarek ◽

John T. Allen ◽

Mattia Marchio ◽

Harold E. Brooks

Keyword(s):

Large Scale ◽

Climate Models ◽

Global Climate ◽

Convective Available Potential Energy ◽

Global Climate Models ◽

Convective Precipitation ◽

The Past ◽

The Tropics ◽

Rawinsonde Data

AbstractGlobally, thunderstorms are responsible for a significant fraction of rainfall, and in the mid-latitudes often produce extreme weather, including large hail, tornadoes and damaging winds. Despite this importance, how the global frequency of thunderstorms and their accompanying hazards has changed over the past 4 decades remains unclear. Large-scale diagnostics applied to global climate models have suggested that the frequency of thunderstorms and their intensity is likely to increase in the future. Here, we show that according to ERA5 convective available potential energy (CAPE) and convective precipitation (CP) have decreased over the tropics and subtropics with simultaneous increases in 0–6 km wind shear (BS06). Conversely, rawinsonde observations paint a different picture across the mid-latitudes with increasing CAPE and significant decreases to BS06. Differing trends and disagreement between ERA5 and rawinsondes observed over some regions suggest that results should be interpreted with caution, especially for CAPE and CP across tropics where uncertainty is the highest and reliable long-term rawinsonde observations are missing.

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Regions of intensification of extreme snowfall under future warming

Scientific Reports ◽

10.1038/s41598-021-95979-4 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Lennart Quante ◽

Sven N. Willner ◽

Robin Middelanis ◽

Anders Levermann

Keyword(s):

Climate Change ◽

Global Warming ◽

Observational Data ◽

Climate Models ◽

Hydrological Cycle ◽

Global Climate ◽

Global Climate Models ◽

Average Intensity ◽

High Latitudes ◽

Future Warming

AbstractDue to climate change the frequency and character of precipitation are changing as the hydrological cycle intensifies. With regards to snowfall, global warming has two opposing influences; increasing humidity enables intense snowfall, whereas higher temperatures decrease the likelihood of snowfall. Here we show an intensification of extreme snowfall across large areas of the Northern Hemisphere under future warming. This is robust across an ensemble of global climate models when they are bias-corrected with observational data. While mean daily snowfall decreases, both the 99th and the 99.9th percentiles of daily snowfall increase in many regions in the next decades, especially for Northern America and Asia. Additionally, the average intensity of snowfall events exceeding these percentiles as experienced historically increases in many regions. This is likely to pose a challenge to municipalities in mid to high latitudes. Overall, extreme snowfall events are likely to become an increasingly important impact of climate change in the next decades, even if they will become rarer, but not necessarily less intense, in the second half of the century.

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A new world natural vegetation map for global change studies

Anais da Academia Brasileira de Ciências ◽

10.1590/s0001-37652008000200017 ◽

2008 ◽

Vol 80 (2) ◽

pp. 397-408 ◽

Cited By ~ 31

Author(s):

David M. Lapola ◽

Marcos D. Oyama ◽

Carlos A. Nobre ◽

Gilvan Sampaio

Keyword(s):

Large Scale ◽

New World ◽

Climate Models ◽

Global Climate ◽

Horizontal Resolution ◽

Vegetation Classification ◽

Natural Vegetation ◽

Global Climate Models ◽

Vegetation Map ◽

Vegetation Maps

We developed a new world natural vegetation map at 1 degree horizontal resolution for use in global climate models. We used the Dorman and Sellers vegetation classification with inclusion of a new biome: tropical seasonal forest, which refers to both deciduous and semi-deciduous tropical forests. SSiB biogeophysical parameters values for this new biome type are presented. Under this new vegetation classification we obtained a consensus map between two global natural vegetation maps widely used in climate studies. We found that these two maps assign different biomes in ca. 1/3 of the continental grid points. To obtain a new global natural vegetation map, non-consensus areas were filled according to regional consensus based on more than 100 regional maps available on the internet. To minimize the risk of using poor quality information, the regional maps were obtained from reliable internet sources, and the filling procedure was based on the consensus among several regional maps obtained from independent sources. The new map was designed to reproduce accurately both the large-scale distribution of the main vegetation types (as it builds on two reliable global natural vegetation maps) and the regional details (as it is based on the consensus of regional maps).

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Mediterranean Precipitation Response to Greenhouse Gases and Aerosols

10.5194/acp-2018-56 ◽

2018 ◽

Author(s):

Tao Tang ◽

Drew Shindell ◽

Bjørn H. Samset ◽

Oliviér Boucher ◽

Piers M. Forster ◽

...

Keyword(s):

Greenhouse Gases ◽

Climate Models ◽

Hydrological Cycle ◽

Global Climate ◽

Local Heating ◽

Global Climate Models ◽

Historical Period ◽

Radiative Balance ◽

Precipitation Decrease ◽

The Mediterranean

Abstract. Atmospheric aerosols and greenhouse gases affect cloud properties, radiative balance and thus, the hydrological cycle. Observations show that precipitation has decreased in the Mediterranean since the 20th century, and many studies have investigated possible mechanisms. So far, however, the effects of aerosol forcing on Mediterranean precipitation remain largely unknown. Here we compare Mediterranean precipitation responses to individual forcing agents in a set of state-of-the-art global climate models (GCMs). Our analyses show that both greenhouse gases and aerosols can cause drying in the Mediterranean, and that precipitation is more sensitive to black carbon (BC) forcing than to well-mixed greenhouse gases (WMGHGs) or sulfate aerosol. In addition to local heating, BC appears to reduce precipitation by causing an enhanced positive North Atlantic Oscillation (NAO)/Arctic Oscillation (AO)-like sea level pressure (SLP) pattern, characterized by higher SLP at mid-latitudes and lower SLP at high-latitudes. WMGHGs cause a similar SLP change, and both are associated with a northward diversion of the jet stream and storm tracks, reducing precipitation in the Mediterranean while increasing precipitation in Northern Europe. Though the applied forcings were much larger, if forcings are scaled to those of the historical period of 1901–2010, roughly one-third (31 ± 17 %) of the precipitation decrease would be attributable to global BC forcing with the remainder largely attributable to WMGHGs whereas global scattering sulfate aerosols have negligible impacts. The results from this study suggest that future BC emissions may significantly affect regional water resources, agricultural practices, ecosystems, and the economy in the Mediterranean region.

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Understanding Intermodel Variability in Future Projections of a Sahelian Storm Proxy and Southern Saharan Warming

Journal of Climate ◽

10.1175/jcli-d-20-0382.1 ◽

2021 ◽

Vol 34 (2) ◽

pp. 509-525

Author(s):

David P. Rowell ◽

Rory G. J. Fitzpatrick ◽

Lawrence S. Jackson ◽

Grace Redmond

Keyword(s):

Large Scale ◽

Climate Models ◽

Global Climate ◽

Vertical Wind Shear ◽

Global Climate Models ◽

Tropospheric Temperature ◽

Storm Activity ◽

Convective Systems ◽

The North ◽

Projected Changes

AbstractProjected changes in the intensity of severe rain events over the North African Sahel—falling from large mesoscale convective systems—cannot be directly assessed from global climate models due to their inadequate resolution and parameterization of convection. Instead, the large-scale atmospheric drivers of these storms must be analyzed. Here we study changes in meridional lower-tropospheric temperature gradient across the Sahel (ΔTGrad), which affect storm development via zonal vertical wind shear and Saharan air layer characteristics. Projected changes in ΔTGrad vary substantially among models, adversely affecting planning decisions that need to be resilient to adverse risks, such as increased flooding. This study seeks to understand the causes of these projection uncertainties and finds three key drivers. The first is intermodel variability in remote warming, which has strongest impact on the eastern Sahel, decaying toward the west. Second, and most important, a warming–advection–circulation feedback in a narrow band along the southern Sahara varies in strength between models. Third, variations in southern Saharan evaporative anomalies weakly affect ΔTGrad, although for an outlier model these are sufficiently substantive to reduce warming here to below that of the global mean. Together these uncertain mechanisms lead to uncertain southern Saharan/northern Sahelian warming, causing the bulk of large intermodel variations in ΔTGrad. In the southern Sahel, a local negative feedback limits the contribution to uncertainties in ΔTGrad. This new knowledge of ΔTGrad projection uncertainties provides understanding that can be used, in combination with further research, to constrain projections of severe Sahelian storm activity.

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Forecast and Uncertainty Analysis of Extreme Precipitation in China from Ensemble of Multiple Climate Models

10.21203/rs.3.rs-209537/v1 ◽

2021 ◽

Author(s):

Peng Deng ◽

Jianting Zhu

Keyword(s):

Extreme Precipitation ◽

Flood Control ◽

Climate Models ◽

Bayesian Model Averaging ◽

Hydrological Cycle ◽

Global Climate ◽

Model Averaging ◽

Statistical Distribution ◽

Global Climate Models ◽

Effective Measure

Abstract Global climate change is expected to have major impact on the hydrological cycle. Understanding potential changes in future extreme precipitation is important to the planning of industrial and agricultural water use, flood control and ecological environment protection. In this paper, we study the statistical distribution of extreme precipitation based on historical observation and various Global Climate Models (GCMs), and predict the expected change and the associated uncertainty. The empirical frequency, Generalized Extreme Value (GEV) distribution and L-moment estimator algorithms are used to establish the statistical distribution relationships and the multi-model ensemble predictions are established by the Bayesian Model Averaging (BMA) method. This ensemble forecast takes advantage of multi-model synthesis, which is an effective measure to reduce the uncertainty of model selection in extreme precipitation forecasting. We have analyzed the relationships among extreme precipitation, return period and precipitation durations for 6 representative cities in China. More significantly, the approach allows for establishing the uncertainty of extreme precipitation predictions. The empirical frequency from the historical data is all within the 90% confidence interval of the BMA ensemble. For the future predictions, the extreme precipitation intensities of various durations tend to become larger compared to the historic results. The extreme precipitation under the RCP8.5 scenario is greater than that under the RCP2.6 scenario. The developed approach not only effectively gives the extreme precipitation predictions, but also can be used to any other extreme hydrological events in future climate.

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