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This paper compared future runoff projections using a Budyko type equation with respect to projections by a global hydrological model (GHM). The comparison was made for the annual mean runoff projections for a future period (2060-2100) after the Budyko parameter was set based on hydrologic model outputs at a present period (1960-2000). The objective of this study was to investigate the performance of the Budyko equation with respect to the hydrologic model at different climate regions. To address the question this study used the spatial average of runoff for the 35 largest basins in the world. According to the comparison, the projections by the two approaches agreed well (R2 = 0.983), in particular in humid tropic region (R2 = 0.986), but with consistent underestimation of future runoff (Median Error, ME = -0.042) by the Budyko equation. In subarctic region the performance of the Budyko equation was low (R2 = 0.599) due to the overestimation of future runoff (ME = 0.110). The results in the dry and temperate regions also showed some discrepancy (R2 = 0.931 and 0.724) without apparent patterns in the errors. The paper discussed possible reasons for the errors with respect to water and energy seasonality and changes in storage component contributions. [ABSTRACT FROM AUTHOR]

Summary: This paper presents an assessment of the impacts of climate change on a series of indicators of hydrological regimes across the global domain, using a global hydrological model run with climate scenarios constructed using pattern-scaling from 21 CMIP3 (Coupled Model Intercomparison Project Phase 3) climate models. Changes are compared with natural variability, with a significant change being defined as greater than the standard deviation of the hydrological indicator in the absence of climate change. Under an SRES (Special Report on Emissions Scenarios) A1b emissions scenario, substantial proportions of the land surface (excluding Greenland and Antarctica) would experience significant changes in hydrological behaviour by 2050; under one climate model scenario (Hadley Centre HadCM3), average annual runoff increases significantly over 47% of the land surface and decreases over 36%; only 17% therefore sees no significant change. There is considerable variability between regions, depending largely on projected changes in precipitation. Uncertainty in projected river flow regimes is dominated by variation in the spatial patterns of climate change between climate models (hydrological model uncertainty is not included). There is, however, a strong degree of consistency in the overall magnitude and direction of change. More than two-thirds of climate models project a significant increase in average annual runoff across almost a quarter of the land surface, and a significant decrease over 14%, with considerably higher degrees of consistency in some regions. Most climate models project increases in runoff in Canada and high-latitude eastern Europe and Siberia, and decreases in runoff in central Europe, around the Mediterranean, the Mashriq, central America and Brasil. There is some evidence that project change in runoff at the regional scale is not linear with change in global average temperature change. The effects of uncertainty in the rate of future emissions is relatively small. [Copyright &y& Elsevier]

It has been shown that the changes in global terrestrial water storage (TWS) are strongly linked to the teleconnections (TCs) that induce large-scale climate variations. However, the contributions of the different TCs to global changes of TWS and its components (water storage components, WSCs) remain undetermined. To fill this gap, we systematically assess the relationships between six major ocean-related TCs and different WSCs derived from the Gravity Recovery and Climate Experiment (GRACE) mission and hydrological models under different timescales. Additionally, the interrelationships of the TCs are also analyzed via the independent component analysis for further investigation. The results allow an improved understanding of the hydrometeorological process controlling WSC changes. Specifically, the annual timescale analysis can constrain high-frequency noises and retain the informative fluctuations of WSC residuals. ENSO and AMO are found to be the two most dominant TCs controlling the variations of WSCs globally. TWS and groundwater storage (GWS) are the two WSCs most correlated with the dominant TCs. The WSCs at shallow depths, which are largely affected by strongly hysteretic controls of TCs, are more closely linked to the TCs with many high-frequency components that tend to have weak hysteresis on WSCs. As for the interrelationships of TCs, the independent component, which is highly correlated with all six TCs, has a predominant influence on WSCs. [ABSTRACT FROM AUTHOR]

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