Exploring hydroclimatic change disparity via the Budyko framework

The Budyko framework characterizes landscape water cycles as a function of climate. We used this framework to identify regions with contrasting hydroclimatic change during the past 50 years in Sweden. This analysis revealed three distinct regions: the mountains, the forests, and the areas with agriculture. Each region responded markedly different to recent climate and anthropogenic changes, and within each region, we identified the most sensitive subregions. These results highlight the need for regional differentiation in climate change adaptation strategies to protect vulnerable ecosystems and freshwater resources. Further, the Budyko curve moved systematically towards its water and energy limits, indicating augmentation of the water cycle driven by changing vegetation, climate and human interactions. This finding challenges the steady state assumption of the Budyko curve and therefore its ability to predict future water cycles. Copyright © 2013 John Wiley & Sons, Ltd.     

Subgrid-Scale Dynamics of Water Vapour, Heat, and Momentum over a Lake

We examine the dynamics of turbulence subgrid (or sub-filter) scales over a lake surface and the implications for large-eddy simulations (LES) of the atmospheric boundary layer. The analysis is based on measurements obtained during the Lake-Atmosphere Turbulent EXchange (LATEX) field campaign (August–October, 2006) over Lake Geneva, Switzerland. Wind velocity, temperature and humidity profiles were measured at 20 Hz using a vertical array of four sonic anemometers and open-path gas analyzers. The results indicate that the observed subgrid-scale statistics are very similar to those observed over land surfaces, suggesting that the effect of the lake waves on surface-layer turbulence during LATEX is small. The measurements allowed, for the first time, the study of subgrid-scale turbulent transport of water vapour, which is found to be well correlated with the transport of heat, suggesting that the subgrid-scale modelling of the two scalars may be coupled to save computational resources during LES.     

THE PROVENANCE OF THE DHARAMSALA FORMATION

THE PROVENANCE OF THE DHARAMSALA FORMATION1　NajmanY ,GarzantiE .ReconstructingearlyHimalayantectonicevolutionandpaleogeographyfromTertiaryforelandbasinsediments,NorthernIndia[J].GSABulletin ,2 0 0 0 .inpress 2　OliverGJH ,JohnsonMRW ,FallickAE .AgeofmetamorphismintheLesserHimalayaandthemainCentralThrustzone ,GarhwalIndia :resultsofillitecrystallinity ,4 0 Ar 3 9ArfusionandK Arstudies[J].GeolMag 1995 ,132 (2 ) :139～149. 3　PognanteU ,CastelliD ,BennaP ,eta…     

Evaporation from boreal reservoirs: A comparison between eddy covariance observations and estimates relying on limited data

Hydrological models used for reservoir management typically lack an accurate representation of open-water evaporation and must be run in a scarce data context. This study aims to identify an accurate means to estimate reservoir evaporation with simple meteorological inputs during the open-water season, using long-term eddy covariance observations from two boreal hydropower reservoirs with contrasting morphometry as reference. Unlike the temperate water bodies on which the majority of other studies have focused, northern reservoirs are governed by three distinct periods: ice cover in the cold season, warming in the summer and energy release in the fall. The reservoirs of interest are Eastmain-1 (52°N, mean depth of 11 m) and Romaine-2 (51°N, mean depth of 42 m), both located in eastern Canada. Four approaches are analysed herein: a combination approach, a radiation-based approach, a mass-transfer approach, and empirical methods. Of all the approaches, the bulk transfer equation with a constant Dalton number of 1.2 x 10⁻³ gave the most accurate estimation of evaporation at hourly time steps, compared with the eddy covariance observations (RMSE of 0.06 mm h⁻¹ at Eastmain-1 and RMSE of 0.04 mm h⁻¹ at Romaine-2). The daily series also showed good accuracy (RMSE of 1.38 mm day⁻¹ at Eastmain-1 and RMSE of 0.62 mm day⁻¹ at Romaine-2) both in the warming and energy release phases of the open-water season. The bulk transfer equation, on the other hand, was incapable of reproducing condensation episodes that occurred soon after ice breakup. Basic and variance-based sensitivity analyses were conducted, in particular to measure the variation in performance when the bulk transfer equation was applied with meteorological observations collected at a certain distance (~10–30 km) from the reservoir. This exercise illustrated that accurate estimates of open water evaporation require representative measurements of wind speed and water surface temperature.     

Testing the Validity of Ar/Ar Single-Crystal White Mica Ages for Erosion, Exhumation and Provenance Stud ies: Recent Sediments From the Ganga River, North India

TESTING THE VALIDITY OF Ar/Ar SINGLE-CRYSTAL WHITE MICA AGES FOR EROSION, EXHUMATION AND PROVENANCE STUDIES:RECENT SEDIMENTS FROM THE GANGA RIVER, NORTH INDIA1　CopelandP ,HarrisonTM .EpisodicrapidupliftintheHimalaya[J].Geology ,1990 ,18:35 4～ 35 7. 2　FrankW ,MillerCh ,GrassemannB .Ar/AragesofdetritalmicasandpalaeogeographicprovenanceofProterozoicclasticsedimentsintheHimalayas[J].10thHimalayan Karakorum TibetWorkshop[C],As…     

The Effect of Scale on the Applicability of Taylor’s Frozen Turbulence Hypothesis in the Atmospheric Boundary Layer

Taylor’s frozen turbulence hypothesis is the central assumption invoked in most experiments designed to investigate turbulence physics with time resolving sensors. It is also frequently used in theoretical discussions when linking Lagrangian to Eulerian flow formalisms. In this work we seek to quantify the effectiveness of Taylor’s hypothesis on the field scale using water vapour as a passive tracer. A horizontally orientated Raman lidar is used to capture the humidity field in space and time above an agricultural region in Switzerland. High resolution wind speed and direction measurements are conducted simultaneously allowing for a direct test of Taylor’s hypothesis at the field scale. Through a wavelet decomposition of the lidar humidity measurements we show that the scale of turbulent motions has a strong influence on the applicability of Taylor’s hypothesis. This dependency on scale is explained through the use of dimensional analysis. We identify a ‘persistency scale’ that can be used to quantify the effectiveness of Taylor’s hypothesis, and present the accuracy of the hypothesis as a function of this non-dimensional length scale. These results are further investigated and verified through the use of large-eddy simulations.     

A conceptual framework for multi-regional climate change assessments for international market systems with long-term investments

A conceptual framework for climate change assessments of international market systems that involve long-term investments is proposed. The framework is a hybrid of dynamic and static modeling. Dynamic modeling is used for those system components for which temporally continuous modeling is possible, while fixed time slices are used for other system components where it can be assumed that underlying assumptions are held constant within the time slices but allowed to vary between slices. An important component of the framework is the assessment of the “metauncertainty” arising from the structural uncertainties of a linked sequence of climate, production, trade and decision-making models. The impetus for proposing the framework is the paucity of industry-wide assessments for market systems with multiple production regions and long-term capital investments that are vulnerable to climate variations and change, especially climate extremes. The proposed framework is pragmatic, eschewing the ideal for the tractable. Even so, numerous implementation challenges are expected, which are illustrated using an example industry. The conceptual framework is offered as a starting point for further discussions of strategies and approaches for climate change impact, vulnerability and adaptation assessments for international market systems.     

Signatures of Air–Wave Interactions Over a Large Lake

The air–water exchange of momentum and scalars (temperature and water vapour) is investigated using the Lake-Atmosphere Turbulent EXchange (LATEX) dataset. The wind waves and swell are found to affect the coupling between the water surface and the air differently. The surface-stress vector aligns with the wind velocity in the presence of wind waves, but a wide range of stress–wind misalignment angles is observed during swell. The momentum transport efficiency decreases when significant stress–wind misalignment is present, suggesting a strong influence of surface wave properties on surface drag. Based on this improved understanding of the role of wave–wind misalignment, a new relative wind speed for surface-layer similarity formulations is proposed and tested using the data. The new expression yields a value of the von Kármán constant (\(\kappa \)) of 0.38, compared to 0.36 when using the absolute wind speed, as well as reduced data fitting errors. Finally, the ratios of aerodynamic to scalar roughness lengths are computed and various existing models in the literature are tested using least-square fitting to the observed ratios. The tests are able to discriminate between the performance of various models; however, they also indicate that more investigations are required to understand the physics of scalar exchanges over waves.     

The effect of bulk composition on the solidus of carbonated eclogite from partial melting experiments at 3 GPa

To explore the effect of bulk composition on the solidus of carbonated eclogite, we determined near-solidus phase relations at 3 GPa for four different nominally anhydrous, carbonated eclogites. Starting materials (SLEC1, SLEC2, SLEC3, and SLEC4) were prepared by adding variable proportions and compositions of carbonate to a natural eclogite xenolith (66039B) from Salt Lake crater, Hawaii. Near-solidus partial melts for all bulk compositions are Fe–Na calcio-dolomitic and coexist with garnet + clinopyroxene + ilmenite ± calcio-dolomitic solid solution. The solidus for SLEC1 (Ca#=100 × molar Ca/(Ca + Mg + Fe_T)=32, 1.63 wt% Na₂O, and 5 wt% CO₂) is bracketed between 1,050°C and 1,075°C (Dasgupta et al. in Earth Planet Sci Lett 227:73–85, 2004), whereas initial melting for SLEC3 (Ca# 41, 1.4 wt% Na₂O, and 4.4 wt% CO₂) is between 1,175°C and 1,200°C. The solidus for SLEC2 (Ca# 33, 1.75 wt% Na₂O, and 15 wt% CO₂) is estimated to be near 1,100°C and the solidus for SLEC3 (Ca# 37, 1.47 wt% Na₂O, and 2.2 wt% CO₂) is between 1,100°C and 1,125°C. Solidus temperatures increase with increasing Ca# of the bulk, owing to the strong influence of the calcite–magnesite binary solidus-minimum on the solidus of carbonate bearing eclogite. Bulk compositions that produce near-solidus crystalline carbonate closer in composition to the minimum along the CaCO₃-MgCO₃ join have lower solidus temperatures. Variations in total CO₂ have significant effect on the solidus if CO₂ is added as CaCO₃, but not if CO₂ is added as a complex mixture that maintains the cationic ratios of the bulk-rock. Thus, as partial melting experiments necessarily have more CO₂ than that likely to be found in natural carbonated eclogites, care must be taken to assure that the compositional shifts associated with excess CO₂ do not unduly influence melting behavior. Near-solidus dolomite and calcite solid solutions have higher Ca/(Ca + Mg) than bulk eclogite compositions, owing to Ca–Mg exchange equilibrium between carbonates and silicates. Carbonates in natural mantle eclogite, which have low bulk CO₂ concentration, will have Ca/Mg buffered by reactions with silicates. Consequently, experiments with high bulk CO₂ may not mimic natural carbonated eclogite phase equilibria unless care is taken to ensure that CO₂ enrichment does not result in inappropriate equilibrium carbonate compositions. Compositions of eclogite-derived carbonate melt span the range of natural carbonatites from oceanic and continental settings. Ca#s of carbonatitic partial melts of eclogite vary significantly and overlap those of partial melts of carbonated lherzolite, however, for a constant Ca-content, Mg# of carbonatites derived from eclogitic sources are likely to be lower than the Mg# of those generated from peridotite.