scholarly journals Unravelling the impacts of precipitation, temperature and land-cover change for extreme drought over the North American High Plains

2018 ◽  
Author(s):  
Annette Hein ◽  
Laura Condon ◽  
Reed Maxwell
Keyword(s):  
Land Cover ◽  
Large Scale ◽  
Hydrologic Model ◽  
Drought Severity ◽  
High Plains ◽  
The North ◽  
Disturbed Land ◽  
Physically Based ◽  
Integrated Hydrologic Model ◽  
The Individual

Abstract. Drought is a natural disaster that may become more common in the future under climate change. It involves changes to temperature, precipitation, and/or land cover, but the relative contributions of each of these factors to overall drought severity is not clear. Here we apply a high-resolution integrated hydrologic model of the High Plains to explore the individual importance of each of these factors and the feedbacks between them. The model was constructed using ParFlow-CLM, which represents surface and subsurface processes in detail with physically based equations. Numerical experiments were run to perturb vegetation, precipitation and temperature separately and in combination. Results show that decreased precipitation caused larger anomalies in evapotranspiration, soil moisture, stream flow and water table levels than did increased temperature or disturbed land cover. However, these factors are not linearly additive when applied in combination; some effects of multi-factor runs came from interactions between temperature, precipitation and land cover. Spatial scale was important in characterizing impacts, as unpredictable and nonlinear impacts at small scales aggregate to predictable, linear large scale behaviour.

scholarly journals Evaluating the relative importance of precipitation, temperature and land-cover change in the hydrologic response to extreme meteorological drought conditions over the North American High Plains

2019 ◽  
Vol 23 (4) ◽  
pp. 1931-1950 ◽  
Author(s):  
Annette Hein ◽  
Laura Condon ◽  
Reed Maxwell
Keyword(s):  
Land Cover ◽  
Large Scale ◽  
Meteorological Drought ◽  
Hydrologic Model ◽  
Drought Severity ◽  
High Plains ◽  
The North ◽  
Physically Based ◽  
Integrated Hydrologic Model ◽  
The Individual

Abstract. Drought is a natural disaster that may become more common in the future under climate change. It involves changes to temperature, precipitation and/or land cover, but the relative contributions of each of these factors to overall drought severity is not clear. Here we apply a high-resolution integrated hydrologic model of the High Plains to explore the individual importance of each of these factors and the feedbacks between them. The model was constructed using ParFlow-CLM, which represents surface and subsurface processes in detail with physically based equations. Numerical experiments were run to perturb vegetation, precipitation and temperature separately and in combination. Results show that decreased precipitation caused larger anomalies in evapotranspiration, soil moisture, stream flow and water table levels than increased temperature or disturbed land cover did. However, these factors are not linearly additive when applied in combination; some effects of multifactor runs came from interactions between temperature, precipitation and land cover. Spatial scale was important in characterizing impacts, as unpredictable and nonlinear impacts at small scales aggregate to predictable, linear large-scale behavior.

Climate Variability in the North Central Region: Characterizing Drought Severity Patterns

2003 ◽  
Author(s):  
Stuart H. Gage
Keyword(s):  
Central Region ◽  
Large Scale ◽  
Stress Index ◽  
Drought Severity ◽  
Spatial And Temporal Variability ◽  
North Central Region ◽  
North Central ◽  
The North ◽  
Groundwater Aquifers ◽  
One Year

This chapter examines the spatial and temporal variability and patterns of climate for the period 1972–1991 in the North Central Region of North America (NCR). Since the mid-1970s, climate has become more variable in the region, compared to the more benign period 1950–1970. The regional perspective presented in this chapter characterizes the general climatology of the NCR from 1972 to 1991 and compares the climate to a severe drought that occurred in 1988. This one-year drought was one of the most substantial in the region’s recent history, and it had a significant impact on the region’s agricultural economy and ecosystems. Petersen et al. (1995) characterize the 1988 drought with respect to solar radiation, and Zangvil et al. (2001) consider this drought from the perspective of a large-scale atmosphere moisture budget. A major reason for the seriousness of the drought in 1988 was the fact that May and June were unusually dry and hot (Kunkel and Angel 1989). Drought is defined as a condition of moisture deficit sufficient to adversely affect vegetation, animals, and humans over a sizeable area (Warwick 1975). The condition of drought may be considered from a meteorological, agricultural, and hydrologic perspective. Meteorological drought is a period of abnormally dry weather sufficiently prolonged to a point where the lack of water causes a serious hydrologic imbalance in the affected area (Huschke 1959). Agricultural drought is a climatic digression involving a shortage of precipitation sufficient to adversely affect crop production or the range of production (Rosenberg 1980). Hydrologic drought is a period of below-average water content in streams, reservoirs, groundwater aquifers, lakes, and soils (Yevjevich et al. 1977). All of these drought conditions are mutually linked. The objectives of this chapter are to (1) address the issues of climatic spatial scale to quantify variability of climate in the NCR, (2) examine the characteristics of the 1988 drought as it relates to characteristics of an ecoregion, (3) illustrate a means to quantify drought through a potential plant stress index, and (4) examine the link of regional drought to ecosystem processes. This analysis will provide background and methodology for ecologists, agriculturalists, and others interested in spatial and temporal characterization of climate patterns within large geographic regions.

Do Statistical Pattern Corrections Improve Seasonal Climate Predictions in the North American Multimodel Ensemble Models?

2017 ◽  
Vol 30 (20) ◽  
pp. 8335-8355 ◽  
Author(s):  
Anthony G. Barnston ◽  
Michael K. Tippett
Keyword(s):  
North American ◽  
Large Scale ◽  
Climate Model ◽  
Principal Component ◽  
Eastern Africa ◽  
Multimodel Ensemble ◽  
Anomaly Correlation ◽  
The North ◽  
The Individual ◽  
North American Multimodel Ensemble

Abstract Canonical correlation analysis (CCA)-based statistical corrections are applied to seasonal mean precipitation and temperature hindcasts of the individual models from the North American Multimodel Ensemble project to correct biases in the positions and amplitudes of the predicted large-scale anomaly patterns. Corrections are applied in 15 individual regions and then merged into globally corrected forecasts. The CCA correction dramatically improves the RMS error skill score, demonstrating that model predictions contain correctable systematic biases in mean and amplitude. However, the corrections do not materially improve the anomaly correlation skills of the individual models for most regions, seasons, and lead times, with the exception of October–December precipitation in Indonesia and eastern Africa. Models with lower uncorrected correlation skill tend to benefit more from the correction, suggesting that their lower skills may be due to correctable systematic errors. Unexpectedly, corrections for the globe as a single region tend to improve the anomaly correlation at least as much as the merged corrections to the individual regions for temperature, and more so for precipitation, perhaps due to better noise filtering. The lack of overall improvement in correlation may imply relatively mild errors in large-scale anomaly patterns. Alternatively, there may be such errors, but the period of record is too short to identify them effectively but long enough to find local biases in mean and amplitude. Therefore, statistical correction methods treating individual locations (e.g., multiple regression or principal component regression) may be recommended for today’s coupled climate model forecasts. The findings highlight that the performance of statistical postprocessing can be grossly overestimated without thorough cross validation or evaluation on independent data.

Beyond Rain

High and Dry ◽  
2017 ◽  
Author(s):  
William M. Alley ◽  
Rosemarie Alley
Keyword(s):  
World War Ii ◽  
Large Scale ◽  
Groundwater Depletion ◽  
High Plains ◽  
The North ◽  
Center Pivot ◽  
The World ◽  
Widespread Availability ◽  
Water And Food Security ◽  
Gravity Recovery

The chapter begins with looking at ways humans have dealt with drought—praying for rain, hiring a rainmaker, or hoping for the best. After World War II, the widespread availability of rural electrification, the deep turbine pump, and center pivot irrigation gave people the option of large-scale use of groundwater. This chapter provides an overview of how groundwater development has radically improved water and food security. The discussion then moves to the growing problems that have resulted from groundwater overuse in places such as the High Plains (Ogallala) Aquifer and the North China Plain. Recently, the GRACE (Gravity Recovery and Climate Experiment) satellites, which can provide precise estimates of changes in groundwater storage over very large areas, have helped draw attention to groundwater depletion around the world.

scholarly journals The ‘Voordelta’, the contiguous ebb-tidal deltas in the SW Netherlands: large-scale morphological changes and sediment budget 1965–2013; impacts of large-scale engineering

2016 ◽  
Vol 96 (3) ◽  
pp. 233-259 ◽  
Author(s):  
Edwin P.L. Elias ◽  
Ad J.F. van der Spek ◽  
Marian Lazar
Keyword(s):  
Large Scale ◽  
Morphological Changes ◽  
Tidal Flow ◽  
Sediment Budget ◽  
Delta Front ◽  
Knowledge Based ◽  
The North ◽  
Sediment Volume ◽  
Ebb Tidal Delta ◽  
The Individual

AbstractThe estuaries in the SW Netherlands, a series of distributaries of the rivers Rhine, Meuse and Scheldt known as the Dutch Delta, have been engineered to a large extent as part of the Delta Project. The Voordelta, a coalescing system of the ebb-tidal deltas of these estuaries, extendsc.10 km offshore and coversc.90 km of the coast. The complete or partial damming of the estuaries had an enormous impact on the ebb-tidal deltas. The strong reduction of the cross-shore directed tidal flow triggered a series of morphological changes that continue until today. This paper aims to give a concise overview of half a century of morphological changes and a sediment budget, both for the individual ebb-tidal deltas and the Voordelta as a whole, based on the analysis of a unique series of frequent bathymetric surveys. The well-monitored changes in the Voordelta, showing the differences in responses of the ebb-tidal deltas, provide clear insight into the underlying processes. Despite anthropogenic dominance, knowledge based on natural inlets can still explain the observed developments. Complete damming of the three northern estuaries Brielse Maas, Haringvliet and Grevelingen resulted in a regime shift, from mixed-energy to wave-dominated, and sediments are transported in landward and downdrift direction. This results in large morphodynamic changes – sediments are redistributed from the delta front landward – but small net volume changes – a 0.1–0.2 × 106m3a−1increase in volume over the period 1965–2010 – since the dams block sediment transport into the estuaries. Sediment volume losses of 106m3a−1are observed on the ebb-tidal delta of the partially closed Eastern Scheldt and still open Western Scheldt estuary. As a result of a reduction of the estuarine tide in the mouth of the Eastern Scheldt, the north–south-running North Sea tidal wave has gained impact on its ebb-tidal delta, which causes morphological adjustments and erosion of the Banjaard shoal area. Moreover, the Eastern Scheldt ebb-tidal delta delivers sediment to its neighbours. The stable ebb-tidal delta configuration in the Western Scheldt, despite major dredging activities, illustrates that these large inlet systems are robust and resilient to significant anthropogenic change, as long as the balance between the dominant hydrodynamic processes (tides and waves) does not alter significantly.

scholarly journals Simulation of low clouds in the Southeast Pacific by the NCEP GFS: sensitivity to vertical mixing

2010 ◽  
Vol 10 (24) ◽  
pp. 12261-12272 ◽  
Author(s):  
R. Sun ◽  
S. Moorthi ◽  
H. Xiao ◽  
C. R. Mechoso
Keyword(s):  
Large Scale ◽  
Vertical Mixing ◽  
Cloud Amount ◽  
Radiative Cooling ◽  
Vertical Diffusion ◽  
Southeast Pacific ◽  
Stratocumulus Clouds ◽  
Physically Based ◽  
Gfs Model ◽  
The Individual

Abstract. The NCEP Global Forecast System (GFS) model has an important systematic error shared by many other models: stratocumuli are missed over the subtropical eastern oceans. It is shown that this error can be alleviated in the GFS by introducing a consideration of the low-level inversion and making two modifications in the model's representation of vertical mixing. The modifications consist of (a) the elimination of background vertical diffusion above the inversion and (b) the incorporation of a stability parameter based on the cloud-top entrainment instability (CTEI) criterion, which limits the strength of shallow convective mixing across the inversion. A control simulation and three experiments are performed in order to examine both the individual and combined effects of modifications on the generation of the stratocumulus clouds. Individually, both modifications result in enhanced cloudiness in the Southeast Pacific (SEP) region, although the cloudiness is still low compared to the ISCCP climatology. If the modifications are applied together, however, the total cloudiness produced in the southeast Pacific has realistic values. This nonlinearity arises as the effects of both modifications reinforce each other in reducing the leakage of moisture across the inversion. Increased moisture trapped below the inversion than in the control run without modifications leads to an increase in cloud amount and cloud-top radiative cooling. Then a positive feedback due to enhanced turbulent mixing in the planetary boundary layer by cloud-top radiative cooling leads to and maintains the stratocumulus cover. Although the amount of total cloudiness obtained with both modifications has realistic values, the relative contributions of low, middle, and high layers tend to differ from the observations. These results demonstrate that it is possible to simulate realistic marine boundary clouds in large-scale models by implementing direct and physically based improvements in the model parameterizations.

scholarly journals Simulation of low clouds in the Southeast Pacific by the NCEP GFS: sensitivity to vertical mixing

2010 ◽  
Vol 10 (8) ◽  
pp. 18467-18505 ◽  
Author(s):  
R. Sun ◽  
S. Moorthi ◽  
H. Xiao ◽  
C.-R. Mechoso
Keyword(s):  
Large Scale ◽  
Vertical Mixing ◽  
Cloud Amount ◽  
Radiative Cooling ◽  
Vertical Diffusion ◽  
Southeast Pacific ◽  
Stratocumulus Clouds ◽  
Physically Based ◽  
Gfs Model ◽  
The Individual

Abstract. The NCEP Global Forecast System (GFS) model has an important systematic error shared by many other models: stratocumuli are missed over the subtropical eastern oceans. It is shown that this error can be alleviated in the GFS by introducing a consideration of the low-level inversion and making two modifications in the model's representation of vertical mixing. The modifications consist of (a) the elimination of background vertical diffusion above the inversion and (b) the incorporation of a stability parameter based on the cloud-top entrainment instability (CTEI) criterion, which limits the strength of shallow convective mixing across the inversion. A control simulation and three experiments are performed in order to examine both the individual and combined effects of modifications on the generation of the stratocumulus clouds. Individually, both modifications result in enhanced cloudiness in the Southeast Pacific (SEP) region, although the cloudiness is still low compared to the ISCCP climatology. If the modifications are applied together, however, the total cloudiness produced in the southeast Pacific has realistic values. This nonlinearity arises as the effects of both modifications reinforce each other in reducing the leakage of moisture across the inversion. Increased moisture trapped below the inversion than in the control run without modifications leads to an increase in cloud amount and cloud-top radiative cooling. Then a positive feedback due to enhanced turbulent mixing in the planetary boundary layer by cloud-top radiative cooling leads to and maintains the stratocumulus cover. Although the amount of total cloudiness obtained with both modifications has realistic values, the relative contributions of low, middle, and high layers tend to differ from the observations. These results demonstrate that it is possible to simulate realistic marine boundary clouds in large-scale models by implementing direct and physically based improvements in the model parameterizations.

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