Hydroclimatic Characteristics of the 2012–2015 California Drought from an Operational Perspective

He, Minxue; Russo, Mitchel; Anderson, Michael L.

doi:10.3390/cli5010005

Cited by 25 publications

(23 citation statements)

References 34 publications

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“…In addition to annual precipitation and temperature, wet season precipitation and seasonal temperature were also applied as important indices in planning studies [45]. Wet season precipitation accounts for a majority portion of the annual precipitation.…”

Section: Difference From the Baselinementioning

confidence: 99%

“…This is particularly true in a warming climate for dry regions where evapotranspiration is an important component of the water budget. For instance, the most recent 2012-2015 California drought was a typical "warm drought" characterized by record-low precipitation and snowpack as well as record-high temperature [45,[53][54][55]. As a result, SPI may not be the most appropriate index for drought analysis in California which contains many arid or semi-arid areas.…”

Section: Drought Indexmentioning

confidence: 99%

“…Therefore, the parametric methods are considered less robust than the non-parametric methods [66]. Among all non-parametric methods, the Mann-Kendall test (MKT) [67,68] has been applied extensively in the field of climatology and hydrology [14][15][16]45,69,70]. The approach first identifies the sign of each possible pair of data in the study time series, followed by the determination of the corresponding test statistic z.…”

Section: Trend Analysismentioning

confidence: 99%

See 2 more Smart Citations

Projected Changes in Precipitation, Temperature, and Drought across California’s Hydrologic Regions in the 21st Century

He¹,

Schwarz²,

Lynn³

et al. 2018

Climate

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This study investigated potential changes in future precipitation, temperature, and drought across 10 hydrologic regions in California. The latest climate model projections on these variables through 2099 representing the current state of the climate science were applied for this purpose. Changes were explored in terms of differences from a historical baseline as well as the changing trend. The results indicate that warming is expected across all regions in all temperature projections, particularly in late-century. There is no such consensus on precipitation, with projections mostly ranging from −25% to +50% different from the historical baseline. There is no statistically significant increasing or decreasing trend in historical precipitation and in the majority of the projections on precipitation. However, on average, precipitation is expected to increase slightly for most regions. The increases in late-century are expected to be more pronounced than the increases in mid-century. The study also shows that warming in summer and fall is more significant than warming in winter and spring. The study further illustrates that, compared to wet regions, dry regions are projected to become more arid. The inland eastern regions are expecting higher increases in temperature than other regions. Particularly, the coolest region, North Lahontan, tends to have the highest increases in both minimum and maximum temperature and a significant amount of increase in wet season precipitation, indicative of increasing flood risks in this region. Overall, these findings are meaningful from both scientific and practical perspectives. From a scientific perspective, these findings provide useful information that can be utilized to improve the current flood and water supply forecasting models or develop new predictive models. From a practical perspective, these findings can help decision-makers in making different adaptive strategies for different regions to address adverse impacts posed by those potential changes.

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Section: Difference From the Baselinementioning

confidence: 99%

Section: Drought Indexmentioning

confidence: 99%

Section: Trend Analysismentioning

confidence: 99%

See 1 more Smart Citation

Projected Changes in Precipitation, Temperature, and Drought across California’s Hydrologic Regions in the 21st Century

He¹,

Schwarz²,

Lynn³

et al. 2018

Climate

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“…Total accumulated PRISM precipitation during the study period demonstrates the characteristic pattern of orographic enhancement over the western United States (Dettinger et al, ; Roe, ), indicated by steep precipitation gradients across the Coast Ranges, Cascade Mountains, and Sierra Nevada Mountains (Figure a). Additionally, there is a climatological north‐south precipitation gradient (Daly et al, ) that was particularly pronounced over the study period due to below average precipitation in California during the 2014/2015 and 2015/2016 winter seasons (He et al, ). Figure b demonstrates the ability of GPM‐DPR to reproduce PRISM's salient precipitation patterns.…”

Section: Gpm‐dpr In Situ Validationmentioning

confidence: 99%

GPM Satellite Radar Measurements of Precipitation and Freezing Level in Atmospheric Rivers: Comparison With Ground‐Based Radars and Reanalyses

et al. 2017

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Atmospheric rivers (ARs) account for more than 90% of the total meridional water vapor flux in midlatitudes, and 25–50% of the annual precipitation in the coastal western United States. In this study, reflectivity profiles from the Global Precipitation Measurement Dual‐Frequency Precipitation Radar (GPM‐DPR) are used to evaluate precipitation and temperature characteristics of ARs over the western coast of North America and the eastern North Pacific Ocean. Evaluation of GPM‐DPR bright‐band height using a network of ground‐based vertically pointing radars along the West Coast demonstrated exceptional agreement, and comparison with freezing level height from reanalyses over the eastern North Pacific Ocean also consistently agreed, indicating that GPM‐DPR can be used to independently validate freezing level in models. However, precipitation comparison with gridded observations across the western United States indicated deficiencies in GPM‐DPR's ability to reproduce the spatial distribution of winter precipitation, likely related to sampling frequency. Over the geographically homogeneous oceanic portion of the domain, sampling frequency was not problematic, and significant differences in the frequency and intensity of precipitation between GPM‐DPR and reanalyses highlighted biases in both satellite‐observed and modeled AR precipitation. Reanalyses precipitation rates below the minimum sensitivity of GPM‐DPR accounted for a 20% increase in total precipitation, and 25% of radar‐derived precipitation rates were greater than the 99th percentile precipitation rate in reanalyses. Due to differences in the proportions of precipitation in convective, stratiform bright‐band, and non‐bright‐band conditions, AR conditions contributed nearly 10% more to total precipitation in GPM‐DPR than reanalyses.

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“…A year having fewer or greater than average of such events can be particularly dry or wet. The State is thus prone to hydroclimatic extremes, with the most recent examples being water year 2015 (record high temperature and record low snowpack observed across the State) [20] and water year 2017 (record high precipitation in the Northern Sierra). Any changes to precipitation, temperature and runoff events, particularly extremes, could have long-lasting adverse impacts on the society, economy, and environment of the State.…”

Section: Introductionmentioning

confidence: 99%

Changes in Extremes of Temperature, Precipitation, and Runoff in California’s Central Valley During 1949–2010

He¹,

Russo²,

Anderson³

et al. 2017

Hydrology

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This study presents a comprehensive trend analysis of precipitation, temperature, and runoff extremes in the Central Valley of California from an operational perspective. California is prone to those extremes of which any changes could have long-lasting adverse impacts on the society, economy, and environment of the State. Available long-term operational datasets of 176 forecasting basins in six forecasting groups and inflow to 12 major water supply reservoirs are employed. A suite of nine precipitation indices and nine temperature indices derived from historical (water year 1949-2010) six-hourly precipitation and temperature data for these basins are investigated, along with nine indices based on daily unimpaired inflow to those 12 reservoirs in a slightly shorter period. Those indices include daily maximum precipitation, temperature, runoff, snowmelt, and others that are critical in informing decision making in water resources management. The non-parametric Mann-Kendall trend test is applied with a trend-free pre-whitening procedure in identifying trends in these indices. Changes in empirical probability distributions of individual study indices in two equal sub-periods are also investigated. The results show decreasing number of cold nights, increasing number of warm nights, increasing maximum temperature, and increasing annual mean minimum temperature at about 60% of the study area. Changes in cold extremes are generally more pronounced than their counterparts in warm extremes, contributing to decreasing diurnal temperature ranges. In general, the driest and coldest Tulare forecasting group observes the most consistent changes among all six groups. Analysis of probability distributions of temperature indices in two sub-periods yields similar results. In contrast, changes in precipitation extremes are less consistent spatially and less significant in terms of change rate. Only four indices exhibit statistically significant changes in less than 10% of the study area. On the regional scale, only the American forecasting group shows significant decreasing trends in two indices including maximum six-hourly precipitation and simple daily intensity index. On the other hand, runoff exhibits strong resilience to the changes noticed in temperature and precipitation extremes. Only the most southern reservoir (Lake Isabella) shows significant earlier peak timing of snowmelt. Additional analysis on runoff indices using different trend analysis methods and different analysis periods also indicates limited changes in these runoff indices. Overall, these findings are meaningful in guiding reservoir operations and water resources planning and management practices. IntroductionClimatic and weather-induced hazards including excessive heat, flooding, and drought are often economically, environmentally, and societally disruptive [1][2][3]. Previous studies have suggested that such hazards are typically caused by changes in the frequency and intensity rather than the mean of hydro-climatic variables including precipita...

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Hydroclimatic Characteristics of the 2012–2015 California Drought from an Operational Perspective

Cited by 25 publications

References 34 publications

Projected Changes in Precipitation, Temperature, and Drought across California’s Hydrologic Regions in the 21st Century

Projected Changes in Precipitation, Temperature, and Drought across California’s Hydrologic Regions in the 21st Century

GPM Satellite Radar Measurements of Precipitation and Freezing Level in Atmospheric Rivers: Comparison With Ground‐Based Radars and Reanalyses

Changes in Extremes of Temperature, Precipitation, and Runoff in California’s Central Valley During 1949–2010

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