A comparison of downscaled and raw GCM output: implications for climate change scenarios in the San Juan River basin, Colorado

Wilby, Rob; Hay, Lauren; Leavesley, George H.

doi:10.1016/s0022-1694(99)00136-5

Cited by 345 publications

(235 citation statements)

References 33 publications

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“…In Period 2 the lowest peak seasonal flows and fall/early winter flows are generally lower than in the other periods, partly due to low precipitation (Figure 5d). These results are qualitatively similar to those of previous studies based both on GCM-derived and prescribed change scenarios Gleick, 1991, 1993;Wilby et al, 1999;Wolock and McCabe, 1999).…”

Section: Runoff and Streamflow Changessupporting

confidence: 91%

“…April 1 snow covered area, on the other hand, remains mostly unchanged in the high elevation Rockies but is reduced in the high plains of western Colorado where snow cover is generally thin. These results are consistent with Brown et al (2000), Wilby et al (1999), McCabe and Wolock (1999) and Nash and Gleick (1993). Figure 6 shows annual average changes in runoff for the control climate and for Periods 1-3 (Period 1, 2010(Period 1, -2039Period 2, 2040-2069, Period 3, 2070-2098 relative to simulated historical runoff.…”

Section: Snowpack Changessupporting

confidence: 90%

“…General Circulation Models (GCMs) of the atmosphere predict increases in global mean annual air temperature between 1.4 and 5.8 • C over the next century (IPCC, 2001). Previous studies Hamlet and Lettenmaier, 1999;Lettenmaier et al, 1992;Nash and Gleick, 1993;Gleick, 1987Gleick, , 1985Wilby et al, 1999;Wolock and McCabe, 1999) of hydrologic and water resources impacts of climate change, both in the Colorado basin and elsewhere, have been based on climate change scenarios that, while predicting increases in temperature, disagreed on the tendency and seasonality of precipitation changes, and on the size of the temperature increase for the next century. The temperature-related effects on streamflows shown in previous studies include an increased rain to snow ratio, an increase in winter runoff and a decrease in summer runoff, and earlier and faster snowmelt.…”

Section: Introductionmentioning

confidence: 99%

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The Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin

et al. 2004

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Abstract. The potential effects of climate change on the hydrology and water resources of the Colorado River basin are assessed by comparing simulated hydrologic and water resources scenarios derived from downscaled climate simulations of the U.S. Department of Energy/National Center for Atmospheric Research Parallel Climate Model (PCM) to scenarios driven by observed historical climate. PCM climate scenarios include an ensemble of three 105-year future climate simulations based on projected 'business-as-usual' (BAU) greenhouse gas emissions and a control climate simulation based on static 1995 greenhouse gas concentrations. Downscaled transient temperature and precipitation sequences were extracted from PCM simulations, and were used to drive the Variable Infiltration Capacity (VIC) macroscale hydrology model to produce corresponding streamflow sequences. Results for the BAU scenarios were summarized into Periods 1, 2, and 3 (2010-2039, 2040-2069, 2070-2098). Average annual temperature changes for the Colorado River basin were 0.5 • C warmer for control climate, and 1.0, 1.7, and 2.4 • C warmer for Periods 1-3, respectively, relative to the historical climate. Basin-average annual precipitation for the control climate was slightly (1%) less than for observed historical climate, and 3, 6, and 3% less for future Periods 1-3, respectively. Annual runoff in the control run was about 10% lower than for simulated historical conditions, and 14, 18, and 17% less for Periods 1-3, respectively. Analysis of water management operations using a water management model driven by simulated streamflows showed that streamflows associated with control and future BAU climates would significantly degrade the performance of the water resources system relative to historical conditions, with average total basin storage reduced by 7% for the control climate and 36, 32 and 40% for Periods 1-3, respectively. Releases from Glen Canyon Dam to the Lower Basin (mandated by the Colorado River Compact) were met in 80% of years for the control climate simulation (versus 92% in the historical climate simulation), and only in 59-75% of years for the future climate runs. Annual hydropower output was also significantly reduced for the control and future climate simulations. The high sensitivity of reservoir system performance for future climate is a reflection of the fragile equilibrium that now exists in operation of the system, with system demands only slightly less than long-term mean annual inflow.

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Section: Runoff and Streamflow Changessupporting

confidence: 91%

Section: Snowpack Changessupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

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The Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin

et al. 2004

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“…those available from climate re-analysis data sets (e.g. Charles et al, 2004;Frost et al, 2006;Wilby et al, 1999, Wilby et al, 2003. Overall, the structures in the GLMs do have some physical motivation.…”

mentioning

confidence: 92%

Stochastic simulation of rainfall in the semi‐arid Limpopo basin, Botswana

Kenabatho

McIntyre

Chandler

et al. 2011

Intl Journal of Climatology

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ABSTRACT:The application of spatial-temporal stochastic rainfall models to semi-arid or arid areas is expected to be particularly challenging because of the high variability of rainfall, sparse rain gauge networks with significant periods of missing rainfall and potential data quality issues. In this article, a generalized linear model (GLM) has been fitted to daily rainfall data from the period 1975-1999 for 13 gauges in a 7660 km 2 sub-basin of the Limpopo basin in Botswana, with the objective of exploring applicability of the GLM for infilling historic records and for climate change analysis. Several relevant statistics of rainfall space-time variability were used to analyse model performance, including use of an independent validation period and sites that were not used in the fitting. The GLM was considered to simulate rainfall adequately for the purpose of sub-basin-scale water resource studies, although the model uncertainty is high. The main factors affecting rainfall space-time variability were found to be seasonality, autocorrelation of daily rainfall, altitude, latitude and longitude. Addition of large-scale drivers of rainfall (pressure, humidity and temperature) further improved representation of inter-annual variability, and this link to large-scale climate potentially facilitates downscaling of global climate model outputs. Although the model was locally sensitive to data quality issues, there was no evidence that these issues affected sub-basin scale analysis.

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“…Within empirical downscaling we distinguish methods which directly link the predictors to the surface variables in a basin of interest (e.g. Wilby et al, 1999), resampling methods (Wójcik and Buishand, 2003) or methods based on weather types. "Expanded Downscaling" (EDS) proposed by Bürger (2002) is a good example of a direct method.…”

Section: Introductionmentioning

confidence: 99%

Modelling of monsoon rainfall for a mesoscale catchment in North-West India I: assessment of objective circulation patterns

Zehe

Singh

Bàrdossy

2006

Hydrol. Earth Syst. Sci.

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Abstract.Within the present study we shed light on the question whether objective circulation patterns (CP) classified from either the 500 HPa or the 700 HPa level may serve as predictors to explain the spatio-temporal variability of monsoon rainfall in the Anas catchment in North West India. To this end we employ a fuzzy ruled based classification approach in combination with a novel objective function as originally proposed by (Stehlik and Brdossy, 2002). After the optimisation we compare the obtained circulation classification schemes for the two pressure levels with respect to their conditional rainfall probabilities and amounts. The classification scheme for the 500 HPa level turns out to be much more suitable to separate dry from wet meteorological conditions during the monsoon season. As is shown during a bootstrap test, the CP conditional rainfall probabilities for the wet and the dry CPs for both pressure levels are highly significant at levels ranging from 95 to 99%. Furthermore, the monthly CP frequencies of the wettest CPs show a significant positive correlation with the variation of the total number of rainy days at the monthly scale. Consistently, the monthly frequencies of the dry CPs exhibit a negative correlation with the number of rainy days at the monthly scale. The present results give clear evidence that the circulation patterns from the 500 HPa level are suitable predictors for explaining spatio-temporal Monsoon variability. A companion paper shows that the CP time series obtained within this study are suitable input into a stochastical rainfall model.

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A comparison of downscaled and raw GCM output: implications for climate change scenarios in the San Juan River basin, Colorado

Cited by 345 publications

References 33 publications

The Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin

The Effects of Climate Change on the Hydrology and Water Resources of the Colorado River Basin

Stochastic simulation of rainfall in the semi‐arid Limpopo basin, Botswana

Modelling of monsoon rainfall for a mesoscale catchment in North-West India I: assessment of objective circulation patterns

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