A Drier Future? Sherwood, Steven; Fu, Qiang
Science (American Association for the Advancement of Science),
02/2014, Letnik:
343, Številka:
6172
Journal Article
Recenzirano
Global warming is likely to lead to overall drying of land surfaces.
Global temperature increases affect the water cycle over land, but the nature of these changes remains difficult to predict. A key ...conceptual problem is to distinguish between droughts, which are transient regional extreme phenomena typically defined as departures from a local climatological norm that is presumed known, and the normal or background dryness itself. This background dryness depends on precipitation, but also on how fast water would evaporate. As the planet warms, global average rainfall increases, but so does evaporation. What is the likely net impact on average aridity?
•Our spatial calibration of predicted stream temperatures is novel for DHSVM-RBM.•This model bridges statistical models and airborne thermal infrared remote sensing.•High-resolution spatiotemporal ...temperature predictions inform resource management.
Conservation planners and resource managers seek information about how the availability and locations of cold-water habitats will change in the future and how these predictions vary among models. We used a physical process-based model to demonstrate the implications of climate change for streamflow and water temperature in two watersheds with distinctive flow regimes: the Snoqualmie watershed (WA) and Siletz watershed (OR), USA. Our model incorporated a downscaled ensemble of global climate model outputs and was calibrated with in situ and remotely sensed water temperatures. We compared predictions from our processed-based model to those from a publicly available and widely used statistical model. The process-based model projected greater changes in summer maximum water temperatures for the mixed-rain-snow Snoqualmie watershed than for the rain-dominated Siletz watershed as a result of the near-complete loss of winter snowpack and significant reduction in summer flow in the Snoqualmie watershed expected by the 2080s. Both models projected generally similar future spatial patterns of maximum water temperature in the two rivers, with cool reaches distributed farther upstream and fewer in number. However, the process-based model projected higher spatial heterogeneity in water temperature due to our spatially explicit simulation of streamflow and because we calibrated the model with spatially continuous remotely sensed water temperature data. We used stream temperature projections to assess the vulnerability of Pacific salmon and trout to changes in the spatial distribution of cold-water habitats during August by the 2080 s. Results suggest that salmonids may have fewer summertime cold-water habitats in both watersheds. Projected stream warming may further limit particular species and life stages, especially in the Snoqualmie watershed. Our comparison of models highlights the importance of considering what might be gained by using a process-based model for evaluating and prioritizing management actions that mitigate climate impacts on cold-water habitats for stream fishes.
Climate change potentially threatens the sustainable production of highly valued cold-water fish species in flow-through systems, such as salmonids. By analysing the relationship of water temperature ...to hydrological characteristics, air temperature, solar exposure, and precipitation, this study predicted temperature dynamics of five temperate cold-water aquaculture facilities under four projected climate change scenarios. Air temperature was found to be directly associated with facility site water temperature, and based on rational assumptions, two of the five facilities were predicted to face critical warming by mid-century. Extreme precipitation events induced acute short-term increases in water temperature of up to 5 °C. Significantly lower warming, roughly equal to the projected climate change–induced increase, was seen with artificial shading lowering temperature by 1 °C. Complementary niche modelling revealed that 37–77 % of current cold-water facilities will likely incur suboptimal climate conditions by the end of the century. Shading of raceways, more efficient water use, and disease management are proposed as key actions to preserve cold-water aquaculture.
Display omitted
•Temperature dynamics were predicted under four projected climate change scenarios.•Water temperature rises significantly less in shaded facilities.•Extreme rain events could induce increases in water temperature of up to 5 °C.•37–77 % of cold-water facilities face suboptimal climate conditions in the future.•Management options are proposed as key actions to preserve cold-water aquaculture.
Fiber optic seismic sensors have important application prospects in the field of earthquake science research and underground structure detection, due to their strong adaptability in harsh ...environments such as deep wells, seabeds, and glaciers. It has always been one of the key problems to achieve ultra-low noise levels over a wide measurement frequency band for fiber optic seismic sensors. This article reviews two typical low-noise broadband fiber optic seismic sensing techniques, including narrow-linewidth laser frequency scanning and frequency locking sensing technique, laser interferometric phase interrogation technique. The principles are given. The measurement frequency band and noise level are tested and discussed. Recent progresses on crustal deformation observation, earthquake monitoring, water temperature solid tide detection and deep earth structure exploration based on fiber optic seismic sensors are introduced. Finally, the possible research trends are discussed.
•Density currents were a prominent feature of tributaries in Three Gorges Reservoir.•Both density currents and unusual thermal profiles were modeled successfully.•Taguchi method was used to analyze ...what causes these density currents.
The initial filling of the Three Gorges Reservoir (TGR), China, has caused serious phytoplankton blooms in its tributary bays. A two-dimensional, laterally averaged, hydrodynamic and water quality CE-QUAL-W2 model was used to simulate the hydrodynamics and water temperature of a typical tributary (Xiangxi Bay XXB) of the TGR to study the relationship between phytoplankton and density currents. The CE-QUAL-W2 model was calibrated to data collected in XXB (depth profiles of velocity and water temperature at three locations) from January 2008 through December 2008. The model performed well in simulating (1) flow velocity profiles, (2) unusual water temperature profiles, (3) the plunge point location of the intrusion layer, (4) propagation speed, and (5) the travel distance of the density currents. The model was then used to examine potential factors that affect the density currents, such as water level fluctuations in the mainstem of the TGR, water temperature differences between the mainstem and XXB, and inflow rates to XXB. Therefore, a better understanding of the hydrodynamics of tributaries in the TGR can be used to understand the aquatic ecosystem dynamics of these tributaries.
Stream water temperature plays a significant role in aquatic ecosystems where it controls many important biological and physical processes. Reliable estimates of water temperature at the daily time ...step are critical in managing water resources. We developed a parsimonious piecewise Bayesian model for estimating daily stream water temperatures that account for temporal autocorrelation and both linear and nonlinear relationships with air temperature and discharge. The model was tested at 8 climatically different basins of the USA and at 34 sites within the mountainous Boise River Basin (Idaho, USA). The results show that the proposed model is robust with an average root mean square error of 1.25 °C and Nash–Sutcliffe coefficient of 0.92 over a 2‐year period. Our approach can be used to predict historic daily stream water temperatures in any location using observed daily stream temperature and regional air temperature data.
Riverine water temperature (WT) is a crucial factor affecting habitat quality and ecological effect of aquatic ecosystems. To accurately quantify and classify WT variation features caused by climate ...change and reservoir construction and operation, a framework was developed that integrates multivariate vine copula model for accurately reconstructing the WT process and general evaluation indicators for comprehensively characterizing of WT variation. In this framework, month‐wise R‐vine copula models were employed to depict the multivariate dependence structure between WT and related hydrometeorological factors, and the change of WT process in the fluctuation range and thermal deviation was analogized as the change of simple harmonic wave in amplitude and phase. A testing‐oriented application of this framework in Yichang section of the Yangtze River highlighted that climate change and the Three Gorges Reservoir (TGR) dominated or participated in the fluctuation range changing and phase deviation of different monthly WT processes, as the ratios of affected months were 1.08:1 and 1.25:1 during the construction phase, and 1:2 and 1:1.28 during the operation phase. WT process also exhibited diverse monthly variation trends during construction and operation phases of the TGR. Therefore, it is inappropriate to neglect the impact of the TGR construction phase and climate change on WT variation. The proposed framework achieved systematic quantification and attribution analysis of WT variation, thereby providing an enhanced understanding of the variation characteristics of river thermal regimes under the individual and combined effects of climate change and artificial reservoir. Considering the significant influence of WT variation on aquatic organism reproduction, the identification of the sources and categories of monthly WT variation can also serve as a foundation for future targeted thermal and hydrological regime regulation, aiming to protecting aquatic species and preventing biodiversity loss.
The testing‐oriented application of this framework achieved a truly quantitative evaluation for the impact of the Three Gorges Reservoir (TGR) and climate change on downstream water temperature (WT) variation features, thus demonstrating its high reliability and practicability. It is inappropriate to neglect the impact of climate change and reservoir construction on WT variation because the TGR and climate change dominate or participate in different monthly WT variation features, and WT variation appears complex and opposite characteristics during the construction and operation phases of the TGR.
•Large water temperature difference for air-source heat pump heating system was first proposed.•A high-fidelity physical model is built in Dymola to evaluate the possibility.•The simulation result ...was validated for variable water temperature difference in laboratory.•Onsite test and operation analysis were finished to demonstrate the proposed method.•The system performance improves about 7% for large water temperature difference.
Heating electrification is a trend for the current carbon neutrality setting. The air-source heat pump (ASHP) has been widely used in residential or commercial buildings to replace household coal-burning stoves due to its higher operating efficiency. Previous studies mainly focused on the heat pump equipment, ignoring the whole system performance in practical application. Among the auxiliary system of the ASHP heating system, the power consumption of water pump cannot be ignored, especially in residential district heating with a large amount of pipeline. This paper proposes the coefficient of performance (COP) improvement of the ASHP heating system through variable temperature difference and flow rate of circulation water loop, showing the feasibility and benefit of large temperature difference with small flow rate. A high-fidelity dynamical model is first built using Dymola, followed by the experiments verification at the environmental laboratory. On all testing conditions, the system COP of large temperature difference with small water flow rate shows average 6% to 8% improvement compared to small temperature difference with large water flow rate. Further, a demonstration heating project of the ASHP system was tested onsite under a realistic operating condition. The recorded hourly operation data showed an average system COP of 2.15 at the condition of large temperature difference, which is about a 7% improvement compared to the small temperature difference condition for the typical heating day.
According to the investigation materials about water bodies of Jiaozhou Bay in May, August and October 1979, this paper studied the changing process of water temperature in the surface and bottom ...waters. Based on the definition and model of Yang Dongfang temporal water temperature variation angle, the results indicated that in the water bodies of inside, around and outside of bay mouth, Viewing the waters inside of bay mouth, around the bay mouth and outside of bay mouth as one water body, the length of variation range of Yang Dongfang temporal water temperature variation angle is 2.98°when heating the surface of this water body, and 0.14°when heating the bottom. The length of variation range of this angle is 6.87°when cooling the surface and 7.28°when cooling the bottom, which displays the changing process of water temperature under the heating or cooling condition.
Water temperatures in mountain streams are likely to rise under future climate change, with negative impacts on ecosystems and water quality. However, it is difficult to predict which streams are ...most vulnerable due to sparse historical records of mountain stream temperatures as well as complex interactions between snowpack, groundwater, streamflow and water temperature. Minimum flow volumes are a potentially useful proxy for stream temperature, since daily streamflow records are much more common. We confirmed that there is a strong inverse relationship between annual low flows and peak water temperature using observed data from unimpaired streams throughout the montane regions of the United States' west coast. We then used linear models to explore the relationships between snowpack, potential evapotranspiration and other climate‐related variables with annual low flow volumes and peak water temperatures. We also incorporated previous years' flow volumes into these models to account for groundwater carryover from year to year. We found that annual peak snowpack water storage is a strong predictor of summer low flows in the more arid watersheds studied. This relationship is mediated by atmospheric water demand and carryover subsurface water storage from previous years, such that multi‐year droughts with high evapotranspiration lead to especially low flow volumes. We conclude that watershed management to help retain snow and increase baseflows may help counteract some of the streamflow temperature rises expected from a warming climate, especially in arid watersheds.
Minimum streamflows each summer are determined by a combination of factors, including the previous winter's snow water equivalent (SWE), carryover storage water from the previous year and evapotranspiration. This figure shows an example watershed in which the lowest summer streamflows occur when peak SWE and the previous year's low flow (a proxy for subsurface storage) are both low, with important climate change implications. This relationship is strongest in arid watersheds.
PDF
