Evaporation Products Research Articles

Critical Importance of Tree and Non‐Tree Vegetation for African Precipitation

AbstractVegetation is a major contributor of terrestrial evaporation and influences subsequent precipitation over land. Studies suggest that forests are crucial for moisture recycling, although the specific contribution of different vegetation to precipitation remains unclear. Using a moisture recycling approach, we investigate the contribution of transpiration from trees and non‐tree vegetation to precipitation over Africa. We use precipitation source regions from simulated atmospheric moisture trajectories, constrained by observation‐based evaporation and precipitation products, and fractional vegetation cover data. Our findings show that trees provide a higher flux to precipitation (∼777 mm year−1) than non‐tree vegetation (∼342 mm year−1). However, considering the smaller spatial extent of trees compared to non‐tree vegetation, precipitation in most watersheds effectively depends more on the latter. Overall, non‐tree vegetation appears equally important as trees in terms of volumetric contributions to precipitation, and deserves attention in further research, considering ongoing land use changes that affect the continental water cycle.

Al₂O₃ Melt interaction with nitrogen at high temperatures and pressure 1 bar

The main chemical reactions of interaction in the Al₂O₃−N₂ system have been determined for a temperature of 2400 K and a pressure of 1 Bar. It was found that in the absence of direct interaction of nitrogen (molecular and atomic) with the melt, chemical reactions between nitrogen and products of dissociative evaporation of Al₂O₃ melt are possible. Nitrogen oxidation reactions and interaction reactions of nitrogen oxides with the melt, both directly and with the participation of elemental oxygen or gaseous aluminium oxides, have been determined. It is demonstrated that elemental forms of nitrogen can interact with the melt together with nitrogen oxides and (or) with all Al-containing components of the system. Concentrations of gaseous substances in equilibrium with Al₂O₃ melt were calculated by the Monte Carlo method.

Nanosecond laser-induced crystallization of SiOx/Au bilayers in air and vacuum

High-quality polycrystalline silicon films on low-cost and low-temperature substrates have attracted much attention as promising materials for high-speed thin-film transistors and thin-film solar cells fabrication. To obtain poly-Si films on low temperature substrates, several concepts have been proposed. Usually the amorphous material undergoes crystallization which can be achieved by various methods including solid-phase crystallization, metal-induced crystallization or liquid-phase crystallization. In this work, we tried to combine the advantages of metal-induced crystallization and liquid-phase crystallization. To achieve this we explored the nanosecond laser crystallization of a bilayer structure consisting of Au and SiO0.1 layers with thicknesses of 30 nm and 130 nm, respectively. The study reveals that when exposed to 532 nm wavelength radiation leads to its destruction due to rupture. On the other hand, when subjected to 1064 nm wavelength radiation, no similar material behavior is observed, and the measured modification threshold is 0.15 J/cm2, representing a 40 % reduction compared to SiO0.1 film without gold. It is demonstrated that at laser fluences of 0.35 J/cm2 and higher, the treatedsurfaceinair becomes enriched with silicon dioxidenanoporous coating, attributed to the return of evaporation products to the target surface. Theoretical modeling, assuming thermal evaporation of the coating, suggests that the undesirable nanoporous layer formation can be avoided.

Probing ultralight primordial black hole dark matter with XMM telescopes

Primordial black holes (PBHs), originating from the gravitational collapse of large overdensities in the early Universe, emerge as a compelling dark matter (DM) candidate across a broad mass range. Of particular interest are ultra-light PBHs with masses around 1014 to 1017 g, which are typically probed by searching their evaporation products. Using the soft X-ray signal measured by the XMM telescopes, we derive constraints on the fraction of PBHs dark matter with masses in the range 1015-1016 g. We find that observations exclude fraction f>10−6 at 95% C.L. for mass MPBH=1015 g.

Hydrothermal synthesis of Ti3+-self-doped TiO2 photocatalysts using wool fibers as a biotemplate

A biotemplate method was used for the synthesis of self-doped TiO2 photocatalysts via the impregnation of sheep wool fibers with a solution containing titanium hydroxocomplexes under mild hydrothermal conditions (115 °C, 170 kPa), followed by the removal of the wool template during calcination in air at 600 °C. An intermediate wool-TiO2 composite, formed as a product of hydrothermal impregnation of a wool biotemplate, was comprehensively studied using IR spectroscopy, XRD, SEM, TG analysis, and DSC with mass spectrometric analysis of evaporation products to evaluate the mechanism of TiO2 crystallization. The phase composition, morphology, texture, and optical properties of the synthesized TiO2 photocatalysts were studied using XRD, SEM, nitrogen adsorption/desorption, and UV–Vis diffuse reflectance spectroscopy. High-temperature treatment after hydrothermal impregnation led to the formation of anatase and rutile TiO2 nanocrystallites with a characteristic size of 15–20 nm. The as-prepared TiO2 photocatalysts had an optical band gap of ∼3.0 eV due to the high content of the rutile phase but also absorbed visible light due to impurity atoms and defects. The samples exhibited very high photocatalytic activity in the degradation of Rhodamine B dye, which was used as a probe molecule, under both UV and visible light. Based on the XPS and EPR results, the enhanced photocatalytic activity of the prepared photocatalysts was attributed to the self-doping effect due to the many defects (Ti3+ sites and oxygen vacancies) formed during TiO2 crystallization, probably via the reduction of Ti4+ to Ti3+ in disproportionation reactions of disulfide bonds involving titanium hydroxocomplexes.

Study on the evaporation performance of concentrated desulfurization wastewater and its products analysis

Concentrated desulfurization wastewater evaporation technology exhibited significant superiority in desulfurization wastewater zero discharge. Nevertheless, changes of physical and chemical properties of the concentrated wastewater shifts evaporation mode during wastewater evaporation, which may cause difficulty in disposing of evaporation products. In this work, the rotary spray drying pilot test experimental platform was utilized to investigate the evaporation performance of concentrated desulfurization wastewater. The results indicate that, while the evaporation rate of concentrated wastewater is lower than that of non-concentrated wastewater, its lower free water volume resulting in the improved evaporation performance. Increasing the inlet flue gas temperature, gas-liquid ratio, and prolonging the residence time of flue gas can promote droplet evaporation. Besides, the evaporation products were analyzed by various characterization techniques. The elemental composition and particle size of concentrated wastewater evaporation products change. At a moisture content of 2 %, the Flowability Function is 3.57 (2 < FF < 4), indicating a cohesive nature and poorer flowability compared to the non-concentrated wastewater.

Characteristics and sources of oxygenated VOCs in Hong Kong: Implications for ozone formation

To investigate the characteristics of oxygenated volatile organic compounds (OVOCs) and their potential contribution to ozone (O3) generation, we conducted 3-h high-resolution observations during the summertime of 2022 and the wintertime of 2021. This study focused on a total of 28 OVOCs in five different chemical classes, which were encompassed at two representative sites in Hong Kong, including a roadside and an urban area. During the summertime, the total concentrations of quantified OVOCs (∑OVOCs) were 45 ± 12 and 63 ± 20 μg m−3 at the roadside and urban sites, respectively, whereas the ∑OVOCs decreased by 31 ± 11 % and 38 ± 13 %, respectively, during the wintertime. Among the classes of OVOCs, carbonyls and alcohols were the two predominant at both sites, with relatively higher concentration levels of acetone, methanol, butanaldehyde, and acrolein. The sources of OVOCs have significant spatial and temporal characteristics. Spatially, OVOCs were predominately attributed to primary emission and background at the roadside site, whereas they were a combination of primary emission, secondary formation, and background at the urban site. Temporally, background sources dominated the summertime OVOCs, while the contribution of primary emissions increased for the wintertime OVOCs. The O3 formation potential (OFP) for the OVOCs was calculated. The OFPs were 67 ± 16 and 119 ± 31 μg m−3 at the roadside and urban sites during the summertime, whereas the winter OFPs declined 30 % at the roadside and 38 % at the urban site. The background sources of carbonyls and alcohols at the roadside and of carbonyls and acrylates in the urban area were the major contributors to the summer OFP. Controlling the OVOC sources from local non-combustion sources such as gasoline-fuel evaporation and volatile chemical-containing products could lead to a reduction of OVOCs in the background and subsequently mitigate the OFP. This is beneficial for local O3 reduction in Hong Kong and surrounding regions.

Interannual land cover and vegetation variability based on remote sensing data in the HTESSEL land surface model: implementation and effects on simulated water dynamics

Abstract. Vegetation largely controls land surface–atmosphere interactions. Although vegetation is highly dynamic across spatial and temporal scales, most land surface models currently used for reanalyses and near-term climate predictions do not adequately represent these dynamics. This causes deficiencies in the variability of modeled water and energy states and fluxes from the land surface. In this study we evaluated the effects of integrating spatially and temporally varying land cover and vegetation characteristics derived from satellite observations on modeled evaporation and soil moisture in the Hydrology Tiled ECMWF Scheme for Surface Exchanges over Land (HTESSEL) land surface model. Specifically, we integrated interannually varying land cover from the European Space Agency Climate Change Initiative and interannually varying leaf area index (LAI) from the Copernicus Global Land Services (CGLS). Additionally, satellite data on the fraction of green vegetation cover (FCover) from CGLS were used to formulate and integrate a spatially and temporally varying effective vegetation cover parameterization. The effects of these three implementations on model evaporation fluxes and soil moisture were analyzed using historical offline (land-only) model experiments at the global scale, and model performances were quantified with global observational products of evaporation (E) and near-surface soil moisture (SMs). The interannually varying land cover consistently altered the evaporation and soil moisture in regions with major land cover changes. The interannually varying LAI considerably improved the correlation of SMs and E with respect to the reference data, with the largest improvements in semiarid regions with predominantly low vegetation during the dry season. These improvements are related to the activation of soil moisture–evaporation feedbacks during vegetation-water-stressed periods with interannually varying LAI in combination with interannually varying effective vegetation cover, defined as an exponential function of LAI. The further improved effective vegetation cover parameterization consistently reduced the errors of model effective vegetation cover, and it regionally improved SMs and E. Overall, our study demonstrated that the enhanced vegetation variability consistently improved the near-surface soil moisture and evaporation variability, but the availability of reliable global observational data remains a limitation for complete understanding of the model response. To further explain the improvements found, we developed an interpretation framework for how the model development activates feedbacks between soil moisture, vegetation, and evaporation during vegetation water stress periods.

ET-WB: water-balance-based estimations of terrestrial evaporation over global land and major global basins

Abstract. Evaporation (ET) is one of the crucial components of the water cycle, which serves as the nexus between global water, energy, and carbon cycles. Accurate quantification of ET is, therefore, pivotal in understanding various earth system processes and subsequent societal applications. The prevailing approaches for ET retrievals are either limited in spatiotemporal coverage or largely influenced by the choice of input data or simplified model physics, or a combination thereof. Here, using an independent mass conservation approach, we develop water-balance-based ET datasets (ET-WB) for the global land and the selected 168 major river basins. We generate 4669 probabilistic unique combinations of the ET-WB leveraging multi-source datasets (23 precipitation, 29 runoff, and 7 storage change datasets) from satellite products, in situ measurements, reanalysis, and hydrological simulations. We compare our results with the four auxiliary global ET datasets and previous regional studies, followed by a rigorous discussion of the uncertainties, their possible sources, and potential ways to constrain them. The seasonal cycle of global ET-WB possesses a unimodal distribution with the highest (median value: 65.61 mm per month) and lowest (median value: 36.11 mm per month) values in July and January, respectively, with the spread range of roughly ±10 mm per month from different subsets of the ensemble. Auxiliary ET products illustrate similar intra-annual characteristics with some over- or underestimation, which are completely within the range of the ET-WB ensemble. We found a gradual increase in global ET-WB from 2003 to 2010 and a subsequent decrease during 2010–2015, followed by a sharper reduction in the remaining years primarily attributed to the varying precipitation. Multiple statistical metrics show reasonably good accuracy of monthly ET-WB (e.g., a relative bias of ±20 %) in most river basins, which ameliorates at annual scales. The long-term mean annual ET-WB varies within 500–600 mm yr−1 and is consistent with the four auxiliary ET products (543–569 mm yr−1). Observed trend estimates, though regionally divergent, are evidence of the increasing ET in a warming climate. The current dataset will likely be useful for several scientific assessments centering around water resources management to benefit society at large. The dataset is publicly available in various formats (NetCDF, Mat, and Shapefile) at https://doi.org/10.5281/zenodo.8339655 (Xiong et al., 2023).

Comprehensive evaluation of terrestrial evapotranspiration from different models under extreme condition over conterminous United States

Terrestrial evapotranspiration (ET) is a key process in the water, energy, and carbon cycles. ET products are becoming more widely accessible with the development of remotely sensed inversions and availability of land surface assimilation information. However, the response of these products to extreme weather is not yet clear and challenging to evaluate. This study evaluated and compared the consistency and uncertainty of nine evaporation products (including GLEAM3.6b, reliability ensemble averaging (REA), CLSM, ERA5-Land (ERA5), MOD16A2, PML-V2 (PML), NOAH, FLDAS, and Synthesized (Syn)) for the period 2003–2015. Eddy covariance (EC) flux observations and the three-cornered hat (TCH) method were used to validate and assess the uncertainty of these products at both the point-scale and grid-scale under normal climatic conditions. More importantly, we conducted uncertainty assessments of ET products at daily and monthly scales under extreme climatic conditions (including high temperature (Temp), high vapor pressure deficit (VPD), and drought), referencing 50 EC measurements over the conterminous United States (COUNS). The results showed that the accuracy of different ET products varied with cover type. Compared to other products, GLEAM3.6b, REA, and Syn showed superior results for most land cover types. Specifically, GLEAM3.6b showed higher performance for the grasslands; REA showed improved performance in mixed forests, open shrubs, and wetlands, and Syn fared better in forests and croplands. The point-scale indicated that the lowest root mean square deviations (RMSD) come from Syn grid products (mean 16.13 mm/month), followed by GLEAM3.6b (mean 18.53 mm/month) and REA (mean 19.42 mm/month). The highest RMSD (mean 49.49 mm/month) originated from ERA5, while the lowest R was found in MOD16A2. The uncertainty ranking calculated using the TCH method is similar to the findings of the point-scale evaluation based on EC measurements, with Syn recording the lowest uncertainty of 5.13 mm/month, after GLEAM3.6b (5.72 mm/month), followed by REA (6.24 mm/month), and ERA5 (12.26 mm/month) with the largest uncertainty. When extreme weather conditions were encountered, the uncertainty of the nine ET products showed an increasing trend, and their consistency varied. Under high-temperature and high-VPD conditions, the consistency decreased, while during drought, the consistency showed a slight increase. Among the ET products, GLEAM3.6b performed best under high-temperature and high-VPD conditions, closely followed by REA. However, ERA5 exhibited the largest error in its estimations. On the other hand, when drought conditions occurred, GLEAM3.6b, REA, and Syn showed better performance, while CLSM, NOAH, and FLDAS ranked second, ERA5 had the largest uncertainty, and MOD16A2 and PML exhibited the worst consistency. The findings of this study offer a foundation for selecting appropriate ET products for hydrologic analysis and agricultural water resource management in the CONUS and give developers suggestions for lowering the uncertainty of ET products in the face of extreme climatic conditions.

Thermal vacuum evaporation peculiarities of perovskite-type barium-strontium hafnate

Experimental results are presented on the thermal vacuum evaporation of barium hafnate BaHfO3 and double barium-strontium hafnate Ba0.5Sr0.5HfO3, which are included together with finely dispersed tungsten as components in sintered composites. It is found that at T = 1900 K only barium and barium oxide are the products of BaHfO3 evaporation, i.e., congruent evaporation of BaHfO3 does not occur. Investigations of Ba0.5Sr0.5HfO3 evaporation at T = 1600 K showed that it also does not evaporate congruently. At the same time, the nucleation of a new phase of BaO·SrO in the form of structures with D6 symmetry was detected. Using a high-current vacuum arc discharge, congruent evaporation of Ba0.5Sr0.5HfO3 takes place, forming various crystalline formations of double barium-strontium hafnate on the substrate.

Vacuum drying of cherry varieties Lyazat, Merey and Aigerim growing in the southern regions of RK

This article presents the results of vacuum drying of cherry varieties: Lyazat, Merey and Aigerim. The dynamics of moisture evaporation shows that the largest amount of moisture evaporates in the time interval from the beginning to 4.0 hours of drying time. For example, in the Aigerim sweet cherry variety, in the considered period of time, for each hour of drying time, depending on the sweet cherry variety, an average of 3.21 g of moisture, and over the next drying time, the intensity of moisture evaporation monotonously decreases of 3,21 g to 1.5 g.Upon reaching the critical humidity in the product of evaporation, moisture drops sharply of 1.5 g to 0.75 g and below. Similar results with slight differences in moisture evaporation are observed for other varieties of cherries. Slight differences in the nature of moisture evaporation in the considered varieties of cherries are explained by the chemical composition, the form of moisture bonding in the product. Studies have established that when drying cherries, two periods of drying are observed. The duration of the first drying period for all studied varieties of cherries averages 6.10...6.25 hours, and the second period 4.50...4.35 hours. The critical humidity for all considered sweet cherry varieties aver-ages 30.5 ... 30.7%.The obtained experimental data on the kinetics of moisture evaporation and the curve of the drying rate of cherries at the next stage of the study make it possible to choose the optimal modes of their drying.

Formation of mullite in fused cast AZS refractories

Fused cast refractories, based on the system Al2O3-ZrO2-SiO2 (AZS), are used in industrial glass tanks and are in direct contact with the glass melt and/or the furnace atmosphere (combustion gases, evaporation products, and dusts) at temperatures up to 1600 °C. Three samples of AZS materials were studied, (i) the original AZS refractory as delivered from the refractory industry, (ii) AZS refractory thermally treated similar to furnace heat up over days and ending for 10 h at 1580 °C and (iii) AZS refractory thermally cycled 600 times between 1530 and 1580 °C after furnace heat up simulation.The samples were studied by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM) including Energy Dispersive X-ray analysis (EDX) and Electron Backscatter Diffraction (EBSD). In the untreated AZS, monoclinic ZrO2 (m-ZrO2) and Al2O3 were detected, while in AZS thermally treated at 1580 °C, mullite also occurred. Thermal cycling led to further increase in the mullite concentration and to a small concentration of tetragonal ZrO2 (t-ZrO2). The Al2O3 crystals as well as some of the ZrO2 had a blocky morphology. Surprisingly also formed mullite crystals were block and not needle-like. In the mullite as well as in the Al2O3 crystals tiny m-ZrO2 crystals were embedded which were formed during cooling in the production process from t-ZrO2 and were heavily twinned.

Enhanced Solubility and Stability of Aripiprazole in Binary and Ternary Inclusion Complexes Using Hydroxy Propyl Beta Cyclodextrin (HPβCD) and L-Arginine.

The low water solubility of an active pharmaceutical ingredient (aripiprazole) is one of the most critical challenges in pharmaceutical research and development. This antipsychotic drug has an inadequate therapeutic impact because of its minimal and idiosyncratic oral bioavailability to treat schizophrenia. The main objective of this study was to improve the solubility and stability of the antipsychotic drug aripiprazole (ARP) via forming binary as well as ternary inclusion complexes with hydroxypropyl-β-cyclodextrin (HPβCD) and L-Arginine (LA) as solubility enhancers. Physical mixing and lyophilization were used in different molar ratios. The developed formulations were analyzed by saturation solubility analysis, and dissolution studies were performed using the pedal method. The formulations were characterized by FTIR, XRD, DSC, SEM, and TGA. The results showcased that the addition of HPβCD and LA inclusion complexes enhanced the stability, in contrast to the binary formulations and ternary formulations prepared by physical mixing and solvent evaporation. Ternary formulation HLY47 improved dissolution rates by six times in simulated gastric fluid (SGF). However, the effect of LA on the solubility enhancement was concentration-dependent and showed optimal enhancement at the ratio of 1:1:0.27. FTIR spectra showed the bond shifting, which confirmed the formation of new complexes. The surface morphology of complexes in SEM studies showed the rough surface of lyophilization and solvent evaporation products, while physical mixing revealed a comparatively crystalline surface. The exothermic peaks in DSC diffractograms showed diminished peaks previously observed in the diffractogram of pure drug and LA. Lyophilized ternary complexes displayed significantly enhanced thermal stability, as observed from the thermograms of TGA. In conclusion, it was observed that the preparation method and a specific drug-to-polymer and amino acid ratio are critical for achieving high drug solubility and stability. These complexes seem to be promising candidates for novel drug delivery systems development.

Trade‐Offs Between Spatial and Temporal Accuracy of Complementary Relationship Models for Evaporation in an Ungauged Basin

AbstractThe complementary relationship (CR) between actual and potential evaporation has undergone rapid development over the past decades. Commonly, the evaluation of CR models does not comprehensively cover spatial and temporal aspects of model performance; thus, the spatial and temporal accuracy and parameter sensitivity of different CR models remain relatively unknown, especially in ungauged basins. We examine the spatial and temporal performance and parameter sensitivity of four CR models with fixed parameters at the monthly scale over the source region of the Yellow River in China. Additionally, two CR models with distributed parameters were selected as comparisons. Because of the lack of evaporation spatiotemporal “true” values, the corrected water‐balance‐derived evaporation was used as the temporal reference, and the ensemble mean of multiple evaporation products was used as the spatial reference. We find that trade‐offs between the spatial and temporal accuracy of CR models with fixed parameters for basin evaporation should be considered in the application. Although four CR models with fixed parameters exhibited different spatial and temporal performances, their overall performance was generally similar. The parameters of CR models had consistent spatial and temporal sensitivities, and the sensitivity of parameter αe was stronger than that of other parameters. This study demonstrates that CR models with distributed parameters have a promising future in estimating basin or regional evaporation. An integrated spatial and temporal evaluation framework can better distinguish the performance of CR models. The methodologies can be used as a guideline for evaluating and calibrating CR models that match an application's needs.

Development of a 60-year high-resolution water body evaporation dataset in China

Evaporation from water bodies (Ew) is a critical component of the global water cycle. However, existing evaporation products that include Ew often suffer from drawbacks such as coarse resolution, short time span, and high uncertainty. This study developed a 60-year (1960–2019) high-resolution (0.05º×0.05º) evaporation dataset for small shallow water bodies in China based on the Penman model. Two key factors affecting the accuracy of the Penman model were considered: the uncertainty of the empirical wind function and changes in heat storage in the water body. Specifically, we used large-size (20 or 100 m2) pan evaporation (Epan) observations from 21 sites as a benchmark to correct the wind function of the Penman model. A data-driven model was then developed to map the spatial distribution of the wind function coefficients across China. The corrected wind function significantly improved the accuracy of Epan estimates compared to the original wind function, with the Kling-Gupta efficiency (KGE) increased by 0.05∼0.10. To model the effect of heat storage changes on evaporation, an equilibrium temperature method was used. We also introduced an area-dependent scaling factor into the wind function to account for the effect of water body's size on Ew estimation. The reliability of the Ew algorithm was tested on two lakes using eddy-covariance flux observations, and simulations showed good agreement with observations. The Epan (20 m2 pan) dataset and its two components calculated from the radiative and aerodynamic terms of the Penman model can be accessed at https://osf.io/qd28m/. Users can utilize the two Epan components and the area-dependent scaling factor to estimate evaporation for water bodies of varying sizes. However, caution is needed when applying this dataset to deep water bodies, as it is designed for shallow water bodies.

Release and migration of Hg during desulfurization wastewater evaporation process: Whole process evaluation by experimental and theoretical study.

Hot flue gas evaporation technology is an effective strategy for zero liquid discharge of desulfurization wastewater. However, there is a potential risk that heavy metals such as Hg may be released from the wastewater during evaporation, disrupting the original balance of the power plant or even exceeding the Hg emission standard. Wastewater evaporation and Hg release behavior were obtained using a single droplet drying system. At an evaporation temperature of 300°C, approximately 18.5% of Hg was released in the constant wet-bulb temperature period, and the remaining was released in the following evaporation periods. Furthermore, a fixed-bed experiment, in combination with density functional theory calculations, was used to investigate the possible migration mechanisms of released Hg. The results revealed that high HCl concentration, introduced fly ash, and precipitated evaporation products play a crucial role in the fate of Hg, and 85.3% of Hg finally turned into less harmful particulate-bound Hg. This study provides a new and effective strategy for evaluating the migration process of pollutants in wastewater treatment. Moreover, it will serve as an essential reference for advanced wastewater treatment and heavy metals control technologies in the future.

Hydrologic Model Calibration With Remote Sensing Data Products in Global Large Basins

AbstractParameters of hydrologic models are typically calibrated using in situ runoff observations. This calibration strategy cannot be implemented when runoff observations are not available. Additionally, the high accuracy of runoff simulation does not guarantee high simulation accuracy of other hydrologic variables, such as evaporation (ET) and terrestrial water storage change (TWSC), leading to uncertainties in hydrologic predictions. To overcome the shortcomings of the runoff‐based calibration strategy, ET and TWSC products from remote sensing were used to design parameter calibration schemes in 59 large basins worldwide. Runoff observations were used to evaluate the effects of different calibration schemes. Results show that single‐objective calibration schemes using the ET or TWSC products for parameter calibrations cannot obtain acceptable runoff simulations. Multi‐objective calibration schemes using the combination of ET and TWSC products for parameter calibrations had better runoff simulation accuracy. The multi‐objective calibration scheme using the combination of ET product adjusted by the Budyko formula and TWSC product as the calibration objective had the best runoff simulation accuracy. It is necessary to adjust ET products before using them for parameter calibrations of hydrologic models. The Budyko formula can be used to reduce the bias in remote sensing ET products, thereby providing better constraints on hydrologic simulations. We also find that different precipitation products used as inputs to hydrologic models can significantly affect the accuracy of runoff simulations. The results are expected to promote the application of remote sensing products in hydrologic simulations and predictions.

Assessing the synergistic modulation of evapotranspiration by global impervious surface and vegetation changes

The different characteristics of impervious urban surfaces and natural underlying surfaces affect water and heat balances, with consequent impacts on evapotranspiration (ET). The global impervious surface area in 1982 was only 34% of that in 2015, motivating an assessment of the net effect of impervious surface changes on ET under rapid impervious surface expansion. In this study, we incorporated the van Dijk model's interception evaporation (Ei) algorithm into the PT-JPL (Priestley-Taylor Jet Propulsion Laboratory) model, and added an impervious surface evaporation (Eu) module, to enable urban ecosystem simulations. This improved model (named the PT-JPLim model) was validated against annual mean ET calculated by P-Q in 8,205 catchments, and against ET measured at 203 flux towers in natural ecosystems and 11 flux towers in urban ecosystems. Calibration showed that the PT-JPLim model performed well (catchments: R = 0.36; natural ecosystems: R = 0.78, RMSE = 13.17 mm; urban ecosystems: R = 0.79, RMSE = 11.74 mm). Additionally, we examined the reliability of modelled ET and its partitioning, by comparison with observed soil evaporation (Eb), Ei, and satellite-based products. By controlling for the impervious surface fraction in the model, it was concluded that the net increase in Eu due to increased impervious surface changes was 0.23 mm/yr, with larger increases in eastern China, India, Europe and southeastern North America than in other regions. The effects of impervious surface and vegetation changes on ET were then analyzed for global impervious surface, with a ratio of 1/4.1 for the effects of impervious surfaces to vegetated surfaces on ET. The contributions of transpiration (Et), Eu, and Eb changes to ET changes on impervious surfaces were 65%, 27% and 8% respectively. These results indicate that synergistic modulation of ET by impervious surface changes and vegetation changes should not be ignored when studying urban eco-hydrological processes.

Clay-cation composition of river sediments as evidence of wet versus dry paleoclimate

Cation compositions (XNa, XCa, XMg) of clays in a fluvial, Late Pleistocene, clay-rich siliciclastic sedimentary unit are shown to reflect the composition of surface water at the time of deposition, with clays deposited from surface water in a semi-arid climate (evaporation > precipitation) having an XNa >8%, compared with XNa < 8% for clays deposited under wetter conditions (evaporation < precipitation). This is a product of evaporation in the dry climate that results in an increase in Na relative to Ca and Mg in the surface water during deposition. This trend is shown in fluvial sediments from the Texas Gulf Coast where both the present-day climate, and the climate during Late Pleistocene deposition, have a gradient from wet humid subtropical (mild temperate) in the north, to dry semi-arid subtropical in the south where evaporation exceeds precipitation for much of the year. The possibility that the clay-cation compositions could have been altered by meteoric water recharge after deposition was considered by comparing the ratios of the conservative ion Cl against Na, which undergoes cation exchange. It was found that the Na-rich clays currently present in the dry environment are releasing Na into the groundwater where they are enriched in Na relative to Cl, which strongly supports the original deposition of Na-rich clays rather than Na-poor clays in the south. This trend was not present in the northern sediments with the wetter climate, which supports the original deposition of Na-poor clays. These results support that the Na content relative to Ca and Mg in clays deposited with siliciclastic sediments from surface water in a fluvial environment could possibly be used as paleoclimate proxies to predict wet versus dry climates.