WATCH Technical Report Number 32: Revisiting GLACE: Understanding the role of the land surface in Land-Atmosphere coupling The Global Land-Atmosphere Coupling Experiment (GLACE) established a method for quantifying and comparing the influence of soil moisture on the atmosphere in AGCMs. The models included in the GLACE intercomparison displayed a wide range in the strength of this influence, with the Met Office Hadley Centre (MOHC) model, HadAM3, being one of the weakest. Applying the GLACE method to a much developed version of the MOHC model, HadGEM3-A, demonstrated this new model has a stronger coupling signal than its predecessor. Although this increased coupling strength cannot be attributed to changes in the land surface representation, the existence of the stronger signal enables an investigation of the signal's dependence on key land surface parameters. The GLACE method is applied to four HadGEM3-A experiment cases, with soil hydraulic parameters specified using two methods of calculation from two different underlying soil texture datasets.
Ruth Comer and Martin Best, September 02, 2011
WATCH Technical Report Number 31: Propagation of Drought through the Hydrological Cycle Drought propagation is the propagation of an anomaly in the climate signal through the terrestrial part of the hydrological cycle. It reflects the processes involved in the development of hydrological drought from (several) meteorological drought(s). In this report, an overview of the results of studies on drought propagation on catchment scale (i.e. the WATCH test basins) and larger scales (i.e. Europe and Malawi) are presented. The methods used are analyses of observations and hydrological modelling results using various RBHMs and LSMs. The objective of this report is to obtain a better understanding of the processes underlying drought propagation. On catchment scale, we conclude that the main features of drought propagation, i.e. pooling, attenuation, lag, and lengthening, are reproduced by all models in all catchments. On larger scales, we conclude that some of the main features of drought propagation, i.e. pooling and lengthening of events, are reproduced in both regions studied. Another important feature of drought propagation, i.e. attenuation of the drought signal, is not captured well by the ensemble mean of LSMs, because storage is not always simulated well on larger scales.
Anne F. van Loon, Henny A.J. van Lanen, Lena M. Tallaksen, Martin Hanel, Miriam Fendeková, Andrej Machlica, Gonzalo Sapriza, Aristeidis Koutroulis, Marjolein H.J. van Huijgevoort, Jorge Jódar Bermúdez, Hege Hisdal, Ioannis Tsanis, June 28, 2011
WATCH Technical Report Number 30: Water Assessment Report for Crete Basins The objective of this report is to analyze and assess the impact of global change to the water resources status for the island of Crete for a range of 24 different scenarios of projected hydro-climatological regime, demand and supply potential. The outcome of the analysis is useful for the comprehension of the role and consequently the priority of certain water resources related infrastructure developments. The quantitative impact of the projected changes on water availability can be substantial especially in a Mediterranean island like Crete.
Ioannis K. Tsanis, Aristeidis G. Koutroulis / Technical University of Crete, June 17, 2011
WATCH Technical Report Number 29: Future Projections in Large-scale Hydrological Extremes Eight global hydrological models (GHM) were assessed for their ability to reproduce European large scale drought and high flow events when using meteorological inputs either observed (represented by the WATCH Forcing Data) or simulated by three Global Circulation Models (GCM), run under historical emission scenarios (control runs). Additionally, the same GHMs were run with future projections from the same GCMs run under the A2 emissions scenario from 2001 to 2100 and the characteristics of large scale hydrological events compared to those of historical runs. The analysis of RDI and RHFI on six contrasting regions across Europe does not suggest that any particular GHM, or family of GHMs, better reproduce the spatial coherence of flow anomalies than any other. When driven by different modelled, rather than observed, climate for the 20th century the sensitivity of different GHMs to the climate input becomes more apparent. The difference in the characteristics of future large-scale hydrological events as simulated by different GCM/GHM combinations is further increased, due to both climate projection uncertainty and GHM sensitivity. When future projections are analysed, results suggest that in temperate regions of Europe the number of large scale drought events is projected to increase by the end of the 21st century by most GCM/GHM combinations. For large scale high flow events, the signal is less clear but suggests little change in the number of events. This multi-model analysis has clearly highlighted that the uncertainty due to hydrological modelling in climate change impact studies, often assumed to be negligible compared to that of climate modelling, can be large (and sometimes larger than that of GCMs) and should not be ignored.
Jennifer Williamson, Simon Parry, George Goodsell, Jamie Hannaford, Christel Prudhomme, June 16, 2011
WATCH Technical Report Number 28: Anthropogenic extreme weather events of the 20th Century Interest in attributing the risk of damaging weather-related events to anthropogenic climate change is increasing. Yet climate models used to study the attribution problem typically do not resolve the weather systems associated with damaging events such as the UK
floods of October and November 2000. Occurring during the wettest autumn in England and Wales since records began in 1766, these floods damaged nearly 10,000 properties across that region, disrupted services severely, and caused insured losses estimated at £1.3 billion. Although the flooding was deemed a ‘wake-up call’ to the impacts of climate change at the time, such claims are typically supported only by general thermodynamic arguments that suggest increased extreme precipitation under global warming, but fail to
account fully for the complex hydrometeorology associated with flooding. Here we present a multi-step, physically based ‘probabilistic event attribution’ framework showing that it is
very likely that global anthropogenic greenhouse gas emissions substantially increased the risk of flood occurrence in England and Wales in autumn 2000.
Pardeep Pall, Tolu Aina, Dáithí A. Stone, Peter A. Stott, Toru Nozawa, Arno G. J., June 02, 2011
WATCH Technical Report Number 27: Effects of climate changes on water resources in the Glomma River basin, Norway In WATCH, a number of test basins across Europe have been used to study effects of climate change on a variety of water resource applications. Here, results from five small catchments within the Glomma River basin in Norway are presented; an area that provides hydropower services under threat of precipitation and temperature increases. The focus in this study is two-fold. First, the effects of climate change on snow and runoff is studied, including a comparison of hydrological simulation results using fine and large scale meteorological data. Second, effects of climate change on hydropower production in the northeastern part of the Glomma River basin are analyzed.
Ingjerd Haddeland, NVE, July 30, 2011
WATCH Technical Report Number 26: Simulation of low flows and drought events in WATCH test basins Impact of different climate forcing datasets Large-scale meteorological datasets are applied more-and-more in hydrological modelling applications. But are these data useful on catchment scale? And how well can models driven with large-scale forcing data capture extremes, i.e. severe drought events?
In this report, the results of hydrological modelling using both local and large-scale forcing data in the WATCH test basins, i.e. five small, contrasting catchments in Europe, are given. The objective of this study was to assess the suitability of large-scale forcing data (in this case the WATCH Forcing Data or WFD) in smaller catchments. The overall conclusions of this research are: 1) The differences between the WFD and local forcing seem to be acceptable as input for hydrological model applications. 2) In all studied catchments and for all models, the difference between simulations and observations is much larger than difference between simulations with different forcing data. 3) In all studied catchments, the difference between simulations with different models is much larger than difference between simulations with different forcing data. 4) All models seem to be able to reproduce the most severe drought events in observed discharge with both forcing datasets in all catchments.
Marjolein H.J. van Huijgevoort, Anne F. van Loon, Martin Hanel, Ingjerd Haddeland, Oliver Horvát, Aristeidis Koutroulis, Andrej Machlica, Graham Weedon, Miriam Fendeková, Ioannis Tsanis, Henny A.J. van Lanen, March 18, 2011
WATCH Technical Report Number 25: Comparison of three drought monitoring tools in the USA Drought has no universal definition, which has led to a large set of indicators. The National Drought Mitigation Center in the USA has combined several drought indicators, based on objective and subjective information, into three online drought monitoring tools: the U.S. Drought Monitor (DM), the Vegetation Drought Response Index (VegDRI) and the Drought Impact Reporter (DIR). This research compares these tools qualitatively and quantitatively and assesses their objectivity. This was done for four case studies (Texas, California, Hawaii and Wisconsin). It can be concluded that DM is the best tool when describing droughts, because it includes subjective information and impact information. The DIR is a good database, but it needs more diverse input (e.g. from all sectors and from a variety of sources). Furthermore the outcome showed that including impacts (mainly subjective) is important when classifying a drought. The drought monitoring tools that are used in the USA are trying to do this and these tools could be used as models in developing a European or global drought monitoring tool.
Esther Dieker, Henny A.J. van Lanen and Mark Svoboda, November 24, 2010
WATCH Technical Report Number 24: Indicators For Drought Characterization on a Global Scale Different drought indicators were tested for the identification of droughts on a global scale. The effect of the hydroclimate and physical catchment structure (soil moisture storage capacity, groundwater responsiveness) on the performance of an indicator (i.e. in terms of severity, frequency and duration of droughts) was investigated. Meteorological drought indicators were calculated using the WATCH Forcing data (WFD). Hydrological drought indicators (e.g. soil moisture, groundwater, streamflow) were derived from time series of hydrological variables that were simulated with a synthetic hydrological model that was driven by WFD. The Moving Average Precipitation with Variable Threshold (MAPVT) and Discharge with Variable Threshold (QVT) seem to be the most promising indicators for drought analysis on a global scale. Both indicators have a very constant performance for different hydroclimates and physical catchment structures and are rather straight forward to calculate.
Niko Wanders, Henny A.J. van Lanen, Anne F. van Loon, Wageningen University, Hydrology and Quantitative Water Management Group, October 15, 2010
WATCH Technical Report Number 23: Spatially explicit estimates of past and present manufacturing and energy water use Water demand for industrial uses and for energy production is rapidly increasing and taking a larger and larger share of global water use of freshwater resources. Water availability and water demands are already heavily outbalanced as a result of natural and socio-economic variability. In this report, a global database on manufacturing and energy water uses taking into account changes in economic growth, thermal electricity production, and water-saving technologies for the 20th century is described. It should be used to provide an indicative picture of water use on a global scale in the manufacturing and energy sectors over recent decades.
Frank Voß, Martina Flörke (CESR), April 06, 2010
WATCH Technical Report Number 22: The WATCH forcing data 1958-2001: a meteorological forcing dataset for land surface- and hydrological-models New global sub-daily meteorological forcing data are provided for use with landsurface-and hydrological-models. The data are derived from the ERA-40 reanalysis product via sequential interpolation to half-degree resolution, elevation correction and monthly-scale adjustments based on CRU (corrected-temperature, diurnal temperature range, cloud-cover) and GPCC (precipitation) monthly observations combined with new corrections for varying atmospheric aerosol-loading and separate precipitation gauge corrections for rainfall and snowfall.
Weedon, G.P., Gomes, S., Viterbo, P., Österle, H., Adam, J.C., Bellouin, N.,Boucher, O., and Best, M., February 26, 2010