Indian Forum for Water Adroit

Testing the Hydrological Coherence of High-Resolution Gridded Precipitation and Temperature Data Set

Pankaj Dey

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  • Institute : Indian Institute of Science
  • Programming language : MATLAB, R
Assessing the accuracy of gridded climate datasets is highly relevant to climate-change impact studies, since evaluation, bias-correction and statistical downscaling of climate models commonly use these products as reference. Among all impact studies those addressing hydrological fluxes are the most affected by errors and biases plaguing these data. This paper introduces a framework, coined Hydrological Coherence Test (HyCoT), for assessing the hydrological coherence of gridded datasets with hydrological observations. HyCoT provides a framework for excluding meteorological forcing datasets not complying with observations, as function of the particular goal at hand. The proposed methodology allows falsifying the hypothesis that a given dataset is coherent with hydrological observations on the basis of the performance of hydrological modeling measured by a metric selected by the modeler. HyCoT is demonstrated in the Adige catchment (southeastern Alps, Italy) for streamflow analysis, using a distributed hydrological model. The comparison covers the period 1989-2008 and includes five gridded daily meteorological datasets: E-OBS, MSWEP, MESAN, APGD and ADIGE. The analysis highlights that APGD and ADIGE, the datasets with highest effective resolution, display similar spatio-temporal precipitation patterns and produce the largest hydrological efficiency indexes. Lower performances are observed for E-OBS, MESAN and MSWEP, especially in small catchments. HyCoT reveals deficiencies in the representation of spatio-temporal patterns of gridded climate datasets, which cannot be corrected by simply rescaling the meteorological forcing fields, as often done in bias-correction of climate model outputs. We recommend this framework to assess the hydrological coherence of gridded datasets to be used in large-scale hydro-climatic studies.