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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,045 records · Page 58
All sourcesNASA NTRSDOE OSTI
NASA NTRS2001

Experimental Measurements of Spreading of Volatile Liquid Droplets

Based on the laser shadowgraphic system used by the first author of the present paper, a simple optical system, which combined the laser shadowgraphy and the direct magnified-photography, has been developed to measure the contact angle, the spreading speed, and the evaporation rate. Additionally, the system can also visualize thermocapillary convection inside of a sessile drop simultaneously. The experimental results show that evaporation/condensation and thermocapillary convection in the sessile drop induced by the evaporation strongly affects the wetting and spreading of the drop. Condensation always promotes the wetting and spreading of the drop. Evaporation may increase or decrease the contact angle of the evaporating sessile drops, depending on the evaporation rate. The thermocapillary convection in the drop induced by the evaporation enhances the effects of evaporation to suppress the spreading.

Zhang, Neng-Li↗
NASA NTRS2003

Final Summary of Research Report to the National Aeronautics and Space Administration Origins of Solar Systems Program

The chondrites are aggregates of components (e.g. chondrules, chondrule rims and matrix) that formed in the nebula but, at present, there is no consensus on how any of these components formed or whether their formation produced or post dated the chemical fractionations between the chondrites. Chondrites are, at present, the most primitive Solar System objects available for laboratory study and the conditions under which their principle components formed would provide the most direct constraints for models of nebula formation and evolution. The conditions under which chondrules formed is of particular importance because, if their relative abundance in chondrites approximates that in the nebula, they are the products of one of the most energetic and pervasive processes that operated in the early Solar System. The goal of this proposal was to combine theoretical modeling with a comprehensive study of the elemental and isotopic compositions of the major components in unequilibrated ordinary chondrites (UOCs), with the aim of determining the conditions in the nebula at the time of their formation. The isotopes of volatile and moderately volatile elements should be particularly revealing of conditions during chondrule formation, as evaporation under most conditions would lead to isotopic mass fractionation. Modeling of chondrule and matrix formation requires the development of a kinetic model of evaporation and condensation, and calibration of this model against experiments. Cosmic spherules present an opportunity to test our evaporation models under flash heating conditions that would be difficult to simulate experimentally. However, there is surprisingly little known about the isotopic compositions of silicate cosmic spherules, and a number of questions need to be addressed. Is the range of compositions they exhibit due to evaporation? If they are, are the relative volatilities consistent with the models/experiments and are the isotopic fractionations consistent with Rayleigh conditions? For instance, do the alkalis and S evaporate prior to significant melting so that conditions did not meet the Rayleigh criteria of rapid diffusion? If so, their isotopic fractionation might be considerably suppressed. Could this mechanism of K loss apply to chondrule formation? The Fe isotopic fractionation during evaporation of silicates has not been measured, so cosmic spherules might provide a clue to whether FeO diffusion is fast enough to maintain Rayleigh conditions during evaporation. And so on.

O'D. Alexander, Conel↗
DOE OSTI2025

Theory of the photomolecular effect

It is well-known that water in liquid and vapor phases exhibits weak visible-light absorption. Recent experiments, however, show that at the liquid-air interface, absorption drastically increases, accelerating evaporation beyond thermal limits by 2–5 times. Strikingly, evaporation peaks at green wavelengths, despite no corresponding absorptance peak. The underlying mechanism of this observation, termed the photomolecular effect, remains puzzling, particularly as water molecules do not exhibit resonance peaks in the visible spectrum. Here, we present a theoretical model explaining the effect. We show that surface-bound water clusters undergo non-resonant photon-driven evaporation, with green light being particularly effective. Crucially, we do not expect green light to couple more strongly than other wavelengths to the molecules at the surface, rather the energy of green light is more effectively used to vaporize water. Our model accounts for why the evaporation peak does not align with absorptance and provides a quantum mechanical explanation of how a single photon can vaporize an entire molecular cluster. This model challenges conventional views on water-light interactions, revealing a fundamentally non-thermal evaporation mechanism. Furthermore, our findings have implications for water purification, energy-efficient drying, and climate modeling, opening new pathways for optimizing evaporation-based technologies.

Interfacial evaporation↗
DOE OSTI2018

Deploying effectively dispatchable PV on reservoirs: Comparing floating PV to other renewable technologies

In this article, we present a detailed simulation of floating photovoltaic's (PV) energy yield and associated evaporation reduction potential for the largest 128 US hydropower reservoirs. A recent article by Cavusoglu et al., published in the journal Nature Communications, outlined a hypothetical evaporation engine that could harness the energy of lake water evaporation while simultaneously conserving the water resource. Its authors suggest that evaporation engines deployed across all US lakes and reservoirs could, collectively, yield up to 70% of the total U.S. electricity production. We show that floating PV technology could: (1) deliver considerably more electrical energy than evaporation engines, amounting to 100% of the US production with only a fraction of the lakes; (2) deliver this energy on a firm, effectively dispatchable basis; and (3) conserve as much water as the evaporation engines.

14 SOLAR ENERGY↗
DOE OSTI2021

Probing Molecular Assembly of Small Organic Molecules during Meniscus-Guided Coating Using Experimental and Molecular Dynamics Approaches

Evaporation-based thin-film coating processes are ubiquitous in fields such as organic electronics, dye coatings, and the pharmaceutical industry. Based on experimental observations of enhanced thin-film alignment during meniscus-guided coating (MGC), a molecular dynamics simulation was developed to describe the thin-film formation that occurs due to the interplay between evaporation and fluid dynamics. The process of solvent evaporation from solution is first examined, which leads to the formation of a solid thin film after evaporation is complete. Next, an MGC process was simulated by introducing a flow profile coupled with the evaporative system. In this work, we gain insights into how molecules respond and reorient in the presence of a flow profile. These results indicate that both the evaporation and the flow profile have an impact on orienting small molecules in a thin film during the MCG process. Combining experimental techniques with simulations helps enhance the understanding of the forces that are significant in directing molecular aggregation during coating processes.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Utilizing Commercial Submersible Mixer Pumps for Sludge Removal in Savannah River Site's Tank 26 - 20289

The Savannah River Site (SRS) Liquid Waste System (LWS) safely manages, stores, treats, and dispositions liquid radioactive waste. The LWS consists of 51 underground waste storage tanks (eight of which are operationally closed and filled with grout), waste evaporators, treatment facilities, and solidification facilities, known as the Defense Waste Processing Facility (DWPF) and Saltstone Production Facility (SPF). One of the waste storage tanks, Tank 26, was placed into service in 1980 as an F Tank Farm (FTF) Evaporator Feed Tank. From 1980 to 2013, Tank 26 received F Canyon receipts and dilute supernate that was then transferred to the 242-16F FTF Evaporator for volume reduction. In 2013, the steam tube bundle failed in the FTF Evaporator, and the decision was made not to repair/resume evaporator operation. During operation of Tank 26, solids built up to a level of 2.03 m in the tank with a volume of 1062.9 kL. Due to the evaporator failure and subsequent shutdown, the solids in Tank 26 were selected to feed Sludge Batch 10, which is collected and prepped prior to being sent to DWPF for final disposition. To accomplish solids removal, Commercial Submersible Mixer Pumps (CSMPs) were selected to slurry the solids in preparation to be sent to Tank 51. Four CSMPs were installed in Tank 26 with each one installed in a separate quadrant of Tank 26. This work would mark the first deployment of CSMPs in an SRS waste tank. The CSMPs were developed in response to operational issues from previous mixing pumps and budgetary constraints. The CSMPs use the concept of modifying commercially available equipment for nuclear waste applications. The CSMPs consist of a 230-horsepower submersible mixing pump (manufactured by GPM, Inc.) joined to a mast fabricated at SRS. For this application, Savannah River Remediation (SRR) design services was challenged to provide a mast design that required no steel superstructure support system on top of Tank 26. Also, SRR design services provided a simplified Tank 26 riser interface that did not require extensive machine parts to adjust height of the suction screen of the CSMP within the tank. Other design improvements include no requirements for tank top radiation monitors and no requirements for flushing of the CSMPs during startup/shutdown operations. The CSMPs were operated at an initial height of 2.29 m above the Tank 26 bottom for 10 days. After sludge sounding, the CSMPs were lowered to a height of 1.52 m with no issues due to proper work planning and the simplified riser interface. With the CSMPs lowered to a level of 1.52 meters above the tank bottom, the CSMPs were operated for 12 days and another sounding was performed. The sounding level came back matching the disturbance depth results of the first pump run. Chemistry samples were analyzed while the tank was left to settle. The analysis revealed enough weight percent solids to provide good feed to Sludge Batch 10. Also, the results revealed the supernate within the mixture would provide good salt solution feed to Salt Waste Processing Facility (SWPF) Salt Batch 3. So, the plan was modified to let the disturbed solids settle and decant the salt solution for addition to SWPF Salt Batch 3. Then water will be added back to Tank 26, and the CSMPs run in order to wash the solids to decrease settling time prior to being sent to Tank 51 for Sludge Batch 10. Utilizing CSMPs for waste removal in an SRS Tank has provided a cost-effective means for further waste removal efforts. In addition, the CSMPs are easier to operate by utilizing a robust and simplified design. The CSMPs performed quite well with no process shutdown or delays during operation. As a result, CSMPs are integral to the future of removing radioactive waste from storage tanks at SRS. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗
DOE OSTI2025

Thermal Response of a Lithium Vapor Divertor to Cyclical Operation

The lithium vapor divertor concept is being developed as a method to achieve detached divertor conditions in a tokamak while minimizing impurity radiation losses from the core plasma. SOLPS-ITER modeling has previously been used to identify some of the geometric constraints and required lithium evaporation rate of a lithium vapor divertor in a medium-sized tokamak during steady-state operation. Here an updated conceptual design based on these operating requirements is introduced and the thermal response of the system is modeled during cyclical operation, consistent with operation in a short-pulse tokamak. Controllability of the temperature of the lithium capillary porous system (CPS) is achieved by adopting a design where there is no line-of-sight for radiation from the plasma to reach the heated CPS surface. Operational strategies to minimize the amount of lithium evaporated between plasma discharges while achieving steady evaporation rates during plasma discharges are discussed and modeled here. The optimal feedforward control strategy demonstrated in this work is to ramp up the temperature of the evaporator as quickly as possible immediately before a plasma discharge and then reduce the heating to match the desired steady-state net evaporation rate just before the plasma discharge begins, allowing the thermal inertia of the system to stabilize the evaporation rate during the first second of the plasma discharge.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Falling-film thermosyphons: Application to water harvesting from humid gas streams

Water harvesting from humid gas streams is central to fresh-water production, desalination, and particulate removal from combustion gas streams. Two-phase thermosyphons are well suited for these applications due to their very low thermal resistance, but have several operating limits at the high heat flows required for such applications. This work introduces the falling-film thermosyphon for large-scale condensation applications. Working fluid is pumped to the top of the evaporator to provide the evaporating liquid film on the inner tube wall, rather than by vapor condensation. The flooding, dry-out and pool-boiling limits are eliminated, resulting in significantly higher maximum heat fluxes for the same physical evaporator size. Furthermore, the condenser no longer needs to be located vertically above the evaporator, which allows for a standard steam condenser to be used. A model for the condensation process in humid air was developed that estimates the fluid and heat transfer and is confirmed experimentally. Further benefits include the use of a high-thermal-conductivity polymer material for the evaporator section to minimize corrosion, and the ability to impose a temperature boundary condition on the evaporator, which is made possible due to the elimination of a liquid pool.

42 ENGINEERING↗
DOE OSTI2019

Drizzle and Turbulence below closed cellular marine stratocumulus clouds

Drizzle is ubiquitous in marine boundary layer stratocumulus clouds with much of it evaporating before reaching the surface. Ten days of observations made at the Atmospheric Radiation Measurement (ARM)’s Eastern North Atlantic (ENA) site during closed cellular stratocumulus cloud conditions are used to characterize drizzle below the cloud base and its impact on the boundary layer turbulence. Cloud and drizzle micro- and macro-physical properties were retrieved by combining the data from vertically pointing Doppler cloud radar, ceilometer, and microwave radiometer. On average the drizzle shafts were 28.14 km wide, with cloud base rain rate and modal diameter of 1.26 mm day-1 and 145.26 µm respectively. The rain rate at the surface was negligible yielding an average diabatic cooling of -30.60 Wm-2 in the sub-cloud layer. The LWP and turbulence within the boundary layer increased with an increase in the cloud top radiative cooling, however none of these variables exhibited any relationship with cloud base rain rate. For a similar amount of radiative cooling at the cloud top, the average variance of vertical velocity in the sub-cloud layer was about 10% lower during strongly precipitating conditions as compared to lightly precipitating conditions. The reduction in the variance of vertical velocity due to drizzle evaporation was primarily confined to the upper half of the sub-cloud layer and was due reduction in the strengths of the downdrafts. Collectively our results show substantial impact of drizzle evaporation on boundary layer turbulence, necessitating its accurate representation in the Earth System Models.

drizzle↗
DOE OSTI2021

Integrated cooling (i-Cool) textile of heat conduction and sweat transportation for personal perspiration management

Perspiration evaporation plays an indispensable role in human body heat dissipation. However, conventional textiles tend to focus on sweat removal and pay little attention to the basic thermoregulation function of sweat, showing limited evaporation ability and cooling efficiency in moderate/profuse perspiration scenarios. Here, we propose an integrated cooling (i-Cool) textile with unique functional structure design for personal perspiration management. By integrating heat conductive pathways and water transport channels decently, i-Cool exhibits enhanced evaporation ability and high sweat evaporative cooling efficiency, not merely liquid sweat wicking function. In the steady-state evaporation test, compared to cotton, up to over 100% reduction in water mass gain ratio, and 3 times higher skin power density increment for every unit of sweat evaporation are demonstrated. Besides, i-Cool shows about 3 °C cooling effect with greatly reduced sweat consumption than cotton in the artificial sweating skin test. The practical application feasibility of i-Cool design principles is well validated based on commercial fabrics. Owing to its exceptional personal perspiration management performance, we expect the i-Cool concept can provide promising design guidelines for next-generation perspiration management textiles.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2025

Nonsingular black holes as dark matter

It is commonly assumed that low-mass primordial black holes cannot constitute a significant fraction of the dark matter in our universe due to their predicted short lifetimes from the conventional Hawking radiation and evaporation process. Assuming physical black holes are nonsingular—likely due to quantum gravity or other high-energy physics—we demonstrate that a large class of nonsingular black holes have finite evaporation temperatures. This can lead to slowly evaporating low-mass black holes or to remnant mass states that circumvent traditional evaporation constraints. As a proof of concept, we explore the limiting curvature hypothesis and the evaporation process of a nonsingular black hole solution in two-dimensional dilaton gravity. We identify generic features of the radiation profile and compare them with known regular black holes, such as the Bardeen solution in four dimensions. Remnant masses are proportional to the fundamental length scale, and we argue that slowly evaporating low-mass nonsingular black holes, or remnants, are viable dark matter candidates. Published by the American Physical Society 2025

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Clumped isotope constraints on changes in latest Pleistocene hydroclimate in the northwestern Great Basin: Lake Surprise, California

Abstract During the Last Glacial Maximum (LGM) and subsequent deglaciation, the Great Basin in the southwestern United States was covered by numerous extensive closed-basin lakes, in stark contrast with the predominately arid climate observed today. This transition from lakes in the Late Pleistocene to modern aridity implies large changes in the regional water balance. Whether these changes were driven by increased precipitation rates due to changes in atmospheric dynamics, decreased evaporation rates resulting from temperature depression and summer insolation changes, or some combination of the two remains uncertain. The factors contributing to these large-scale changes in hydroclimate are critical to resolve, given that this region is poised to undergo future anthropogenic-forced climate changes with large uncertainties in model simulations for the 21st century. Furthermore, there are ambiguous constraints on the magnitude and even the sign of changes in key hydroclimate variables between the Last Glacial Maximum and the present day in both proxy reconstructions and climate model analyses of the region. Here we report thermodynamically derived estimates of changes in temperature, precipitation, and evaporation rates, as well as the isotopic composition of lake water, using clumped isotope data from an ancient lake in the northwestern Great Basin, Lake Surprise (California). Compared to modern climate, mean annual air temperature at Lake Surprise was 4.7 °C lower during the Last Glacial Maximum, with decreased evaporation rates and similar precipitation rates to modern. During the mid-deglacial period, the growth of Lake Surprise implied that the lake hydrologic budget briefly departed from steady state. Our reconstructions indicate that this growth took place rapidly, while the subsequent lake regression took place over several thousand years. Using models for precipitation and evaporation constrained from clumped isotope results, we determine that the disappearance of Lake Surprise coincided with a moderate increase in lake temperature, along with increasing evaporation rates outpacing increasing precipitation rates. Concomitant analysis of proxy data and climate model simulations for the Last Glacial Maximum are used to provide a robust means to understand past climate change, and by extension, predict how current hydroclimates may respond to expected future climate forcings. We suggest that an expansion of this analysis to more basins across a larger spatial scale could provide valuable insight into proposed climate forcings, and aid in climate model process depiction. Ultimately, our analysis highlights the importance of temperature-driven evaporation as a mechanism for lake growth and retreat in this region.

Geology↗
DOE OSTI2025

Numerical case study of the aerosol–cloud interactions in warm boundary layer clouds over the eastern North Atlantic with an interactive chemistry module

The presence of warm boundary layer stratiform clouds over the eastern North Atlantic (ENA) region is commonly influenced by the Azores High, especially during the summer season. To investigate comprehensive aerosol–cloud interactions, this study employs the Weather Research and Forecasting model coupled with a chemistry component (WRF-Chem), incorporating aerosol chemical components that are relevant to the formation of cloud condensation nuclei (CCN) and accounting for aerosol spatiotemporal variation. This study focuses on aerosol indirect effects, particularly the long-range transport of aerosols, in the ENA region under three different weather regimes: a ridge with a surface high-pressure system, a post-trough with a surface high-pressure system, and a weak trough. The WRF-Chem simulations conducted at a near-large-eddy scale offer valuable insights into the model's performance, especially in terms of its ability to use high spatial resolution to capture mesoscale cloud features across various weather regimes. Our result shows that introducing 5 times more aerosols to either non-precipitating or precipitating clouds significantly increases ambient CCN numbers, resulting in, to varying degrees, higher liquid water path (LWP) values. The substantial aerosol–cloud interaction especially occurs in the precipitating clouds and demonstrates the susceptibility of the LWP to changes in CCN under different regimes. Conversely, thin, non-rain clouds at the edges of a cloud system are prone to evaporation, exhibiting an aerosol drying effect. The aerosols released during this process transition back to the accumulation mode, facilitating future activation. This dynamic behavior is not adequately represented in prescribed-aerosol simulations.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1993

The correlation of alkalis and aluminum during high-temperature volatilization of albite and nepheline

Our previous study of high-temperature evaporation of mafic targets has shown a systematic enrichment of newly-formed condensates in silicon and alkalis and depletion in refractory elements (Al, Ca, Ti). This effect, which is consistent with the volatility of the elements, was also tested for several experiments with acidic targets. In one case it was the impact evaporation of granite targets using a light-gas gun facility. Analyses of the condensate which was collected during the impact show that it was enriched in Al and Na so that the composition of the condensate became close to nepheline. In the work of Nagahara, an incongruent evaporation of alkali feldspars under stationary conditions has been also proposed. These discoveries required a more detailed study of high-temperaure evaporation of monomineralic Al-silicate targets. In these experiments, we have used samples of oligoclase and of nepheline. Vaporization of samples was performed in a hermetic cell filled with helium at normal temperature and pressure using a powerful Nd-laser focused on the sample. Laser pulses had the following parameters: luminous energy approximately 600 J, duration approximately 10(exp -3) s, density of luminosity was approximately 5 x 10(exp 6) W/sq cm, the temperature of vaporization is about 3000-4000 K. About 4 cm from the sample, a nickel foil was placed on which the condensate was collected. Films of condensate were analyzed using X-Ray Photo-Electron spectrometer ES-2401. The measurement of internal chemical composition and of the charging state of elements through the whole depth of the condensed films was made layer by layer with argon-ion etching of 200 A of the film per step. Results of this study are given. The bottom layers of condensed film correspond to the front parts of the evaporated cloud or to condensation at the beginning of the evaporative process and surface layers to condensation at the end of the process.

Dikov, Yu. P.↗
NASA NTRS1994

Constraints on chondrule and CAI origins from vapor-liquid-solid experiments

It has been widely accepted that evaporation played an important role in the formation of chondritic constituents and elemental and isotopic fractionation in the solar nebula. Although many workers consider that evaporation is just the opposite of condensation, it is true only when the process is in equilibrium. When the process is not in equilibrium, e.g., local evaporation, where generated gas moves away from the residual solids, the fractionation path is quite different from the opposite of condensation of the gas with the solar system elemental abundances. The degree of elemental, particularly isotopic, fractionation is strongly dependent on the evaporation rate of the element when evaporation takes place from solid materials. The phase relations and the rate of evaporation of chondrite-forming minerals give constraints on partial pressure of the dust components, total pressure of the nebular gas, and heating rate of the materials.

Nagahara, H.↗
NASA NTRS1997

Solar Cells for Lunar Application

In this work a preliminary study of the vacuum evaporation of silicon extracted from the lunar regolith has been undertaken. An electron gun vacuum evaporation system has been adapted for this purpose. Following the calibration of the system using ultra high purity silicon deposited on Al coated glass substrates, thin films of lunar Si were evaporated on a variety of crystalline substrates as well as on glass and lightweight 1 mil (25 microns) Al foil. Extremely smooth and featureless films with essentially semiconducting properties were obtained. Optical absorption analysis sets the bandgap (about 1.1 eV) and the refractive index (n=3.5) of the deposited thin films close to that of crystalline silicon. Secondary ion mass spectroscopy and energy dispersive spectroscopy analysis indicated that these films are essentially comparable to high purity silicon and that the evaporation process resulted in a substantial reduction of impurity levels. All layers exhibited a p-type conductivity suggesting the presence of a p-type dopant in the fabricated layers. While the purity of the 'lunar waste material' is below that of the 'microelectronic-grade silicon', the vacuum evaporated material properties seems to be adequate for the fabrication of average performance Si-based devices such as thin film solar cells. Taking into account solar cell thickness requirements (greater than 10 microns) and the small quantities of lunar material available for this study, solar cell fabrication was not possible. However, the high quality of the optical and electronic properties of evaporated thin films was found to be similar to those obtained using ultra-high purity silicon suggest that thin film solar cell production on the lunar surface with in situ resource utilization may be a viable approach for electric power generation on the moon.

Freundlich, Alex↗
NASA NTRS1999

The Question of Future Droughts in a CO2-Warmed World

Increased droughts are to be expected in a warmer world, and so are increased floods. A warmer atmosphere can hold more moisture, and evaporate more water from the surface. Thus, when it is not raining, available soil water should be reduced. When it is raining, it could very well rain harder. Most researchers agree then that a warmer world will have greater hydrologic extremes. In addition, there is a basic imbalance that develops as climate warms, between the loss of moisture from the soil by evaporation and replenishment via precipitation. The land has a smaller heat capacity than the ocean, so it should warm faster. Evaporation from the land proceeds at the rate of its warming, while precipitation derives primarily from evaporation at the ocean surface. As the latter is increasing more slowly, in a warmer world, precipitation will not increase as rapidly as evaporation due to the fact that the oceans warm more slowly than the land surface (evaporation over the ocean is slower than over the land). Hence, more droughts are anticipated in a warmer world, but the specific location of such droughts is somewhat uncertain. To address the question of where droughts are likely to occur, one first needs to have a reasonable sense of what the future magnitude of warming will be, and what the latitudinal distribution of warming will be. For example, the greater the warming at high latitudes relative to low latitudes, the more likely there will be increased drought over the U.S. in summer. In contrast, substantial tropical warming could give us El Nino-like precipitation, with intensified flooding along the southern tier of the U.S. All of these conditions are likely to intensify as the global temperature rises.

Rind, David↗
NASA NTRS1998

Carbon-Water-Energy Relations for Selected River Basins

A biophysical process-based model was run using satellite, assimilated and ancillary data for four years (1987-1990) to calculate components of total evaporation (transpiration, interception, soil and snow evaporation), net radiation, absorbed photosynthetically active radiation and net primary productivity over the global land surface. Satellite observations provided fractional vegetation cover, solar and photosynthetically active radiation incident of the surface, surface albedo, fractional cloud cover, air temperature and vapor pressure. The friction velocity and surface air pressure are obtained from a four dimensional data assimilation results, while precipitation is either only surface observations or a blended product of surface and satellite observations. All surface and satellite data are monthly mean values; precipitation has been disaggregated into daily values. All biophysical parameters of the model are prescribed according to published records. From these global land surface calculations results for river basins are derived using digital templates of basin boundaries. Comparisons with field observations (micrometeorologic, catchment water balance, biomass production) and atmospheric water budget analysis for monthly evaporation from six river basins have been done to assess errors in the calculations. Comparisons are also made with previous estimates of zonal variations of evaporation and net primary productivity. Efficiencies of transpiration, total evaporation and radiation use, and evaporative fraction for selected river basins will be presented.

Choudhury, B. J.↗