Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “UPWELLING”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Influence of heating mode on three-dimensional mantle convection

Numerical models of three-dimensional thermal convection in highly viscous spherical shells with different combinations of internal and basal heating consistently have upwelling concentrations in the form of cylindrical plumes and downwelling in planar sheets. As the proportion of internal heating increases, the number of upwelling plumes increases, and downwelling sheets become more vigorous and time-dependent. With any amount of basal heating, the entire convective pattern, during its evolution, is anchored to the upwelling plumes. As the proportion of internal heating increases, the heat flow carried by the upwelling plumes remains a large fraction of the basal heat flow. Downwelling sheets carry only a minor fraction (approximately 30 percent) of the basal heat flow (even when the shell is entirely heated from below), but they advect almost all of the internally generated heat. The relatively large number of plumes in the earth's mantle (inferred from hotspots), the possibility that downwelling slabs are vigorous enough to penetrate the lower mantle, and the small fraction of terrestrial surface heat flow carried by plumes all suggest that the mantle is predominantly heated from within.

Bercovici, D.↗
NASA NTRS1990

Physical retrieval of precipitation water contents from Special Sensor Microwave/Imager (SSM/I) data. Part 1: A cloud ensemble/radiative parameterization for sensor response (report version)

The physical retrieval of geophysical parameters based upon remotely sensed data requires a sensor response model which relates the upwelling radiances that the sensor observes to the parameters to be retrieved. In the retrieval of precipitation water contents from satellite passive microwave observations, the sensor response model has two basic components. First, a description of the radiative transfer of microwaves through a precipitating atmosphere must be considered, because it is necessary to establish the physical relationship between precipitation water content and upwelling microwave brightness temperature. Also the spatial response of the satellite microwave sensor (or antenna pattern) must be included in the description of sensor response, since precipitation and the associated brightness temperature field can vary over a typical microwave sensor resolution footprint. A 'population' of convective cells, as well as stratiform clouds, are simulated using a computationally-efficient multi-cylinder cloud model. Ensembles of clouds selected at random from the population, distributed over a 25 km x 25 km model domain, serve as the basis for radiative transfer calculations of upwelling brightness temperatures at the SSM/I frequencies. Sensor spatial response is treated explicitly by convolving the upwelling brightness temperature by the domain-integrated SSM/I antenna patterns. The sensor response model is utilized in precipitation water content retrievals.

Olson, William S.↗
NASA NTRS1995

Thermal and chemical convection in planetary mantles

Melting of the upper mantle and extraction of melt result in the formation of a less dense depleted mantle. This paper describes series of two-dimensional models that investigate the effects of chemical buoyancy induced by these density variations. A tracer particles method has been set up to follow as closely as possible the chemical state of the mantle and to model the chemical buoyant force at each grid point. Each series of models provides the evolution with time of magma production, crustal thickness, surface heat flux, and thermal and chemical state of the mantle. First, models that do not take into account the displacement of plates at the surface of Earth demonstrate that chemical buoyancy has an important effect on the geometry of convection. Then models include horizontal motion of plates 5000 km wide. Recycling of crust is taken into account. For a sufficiently high plate velocity which depends on the thermal Rayleigh number, the cell's size is strongly coupled with the plate's size. Plate motion forces chemically buoyant material to sink into the mantle. Then the positive chemical buoyancy yields upwelling as depleted mantle reaches the interface between the upper and the lower mantle. This process is very efficient in mixing the depleted and undepleted mantle at the scale of the grid spacing since these zones of upwelling disrupt the large convective flow. At low spreading rates, zones of upwelling develop quickly, melting occurs, and the model predicts intraplate volcanism by melting of subducted crust. At fast spreading rates, depleted mantle also favors the formation of these zones of upwelling, but they are not strong enough to yield partial melting. Their rapid displacement toward the ridge contributes to faster large-scale homogenization.

Dupeyrat, L.↗
NASA NTRS1994

Geosat-derived sea level and surface current anomalies in the equatorial Pacific during the 1986-1989 El Nino and La Nina

Equatorial wave dynamics are essential in most oceanic models for reproducing aspects of the El Nino-Southern Oscillation (ENSO) phenomenon. Observational evidence of first baroclinic equatorial Kelvin and first symmetric meridional Rossby waves is found in Geosat-derived sea level anomalies (SLA) and surface zonal current anomalies (ZCA) in the equatorial Pacific ocean during the 1986-1987 El Nino and the ensuing 1988-1989 La Nina. This was made possible after extensive quality control and specific processing of the recently improved Geosat geophysical data records pertaining to the 17-day Exact Repeat Mission. In particular, the processing was made so that the Geosat-derived ZCA best fit near-surface zonal currents from three equatorial moorings at 165 deg E, 140 deg W, and 110 deg W. The Geosat-derived SLA and ZCA are decomposed into first baroclinic equatorial Kelvin and gravest Rossby modes. The emphasis is then put on the chronology of the ZCA at the equator where the currents are the most energetic and where Kelvin and first symmetric Rossby waves explain most of the variance in ZCA, in similar proportion. The 1986-1987 El Nino is mostly characterized by a strong downwelling Kelvin wave in December 1986, a series of downwelling Kelvin waves in March-October 1987, and a strong upwelling Rossby wave in March-September 1987. These waves are consistent with wind forcing, and all give rise to notable eastward ZCA for almost an entire year. During El Nino-La Nina transition period there is the occurrence of two downwelling Rossby waves originating from the eastern Pacific at times of favorable wind forcing. These Rossby waves switch the basin-wide ZCA from eastward to westward, terminating the warm event. Then, the 1988-1989 La Nina shows the generation of a series of upwelling Kelvin waves which are clearly identified in March/April and September/October 1988. These upwelling Kelvin waves are apparently related to the enhencement of the trade wind in the western half of the basin. These waves maintain the basin-wide westward ZCA for more than a year, although the ZCA is slightly reduced ba front of upwelling Rossby waves in phase with the normal seasonal cycle. The Kelvin wave forcing and sign of kelvin wave contribution versus Rossby wave contribution to ZCA in the western Pacific are discussed, and we conclude that neither pleads in favor of the delayed action oscillator mechanism.

Delcroix, Thierry↗
NASA NTRS2009

On the Influence of Anthropogenic Forcings on Changes in the Stratospheric Mean Age

A common feature of stratospheric simulations of the past or future is an increase in tropical upwelling and a decrease in mean age. Possible causes or these changes include (1) increases in tropical sea surface temperatures (SSTs) driven by increases in well-mixed greenhouse gases (WMGHGs), (2) the direct radiative effect of increases in WMGHGs, and (3) changes in ozone. Here we examine a suite of simulations from the Goddard Earth Observing System chemistry-climate model (GEOS CCM) to isolate the relative role of these three factors. Our analysis indicates that all three factors cause changes in the mean age, but the relative impact of each factor depends on the time period analyzed. Over the past 30-40 years ozone depletion is the major factor causing the decrease in mean age, with negligible changes due to direct radiative impact of WMGHG's. However, ozone is predicted to recover back to 1970 levels during the next 50-60 years, and this causes an increase in the mean age, whereas the continued increase in SSTs from increased levels of WMGHGs and the direct radiative impact of WMGHGs will still cause a decrease in the mean age. The net impact of these factors will still result in a decreasing mean age although the rate will be smaller than that of the past. The decreases in mean age are primarily caused by increases in upwelling in the tropical lower stratosphere. The increased upwelling from both increased tropical SSTs and polar ozone loss appears to be related to changes in zonal winds and increases in wave activity propagating into the stratosphere. The different contributions of changes in SSTs, WMGHGs, and ozone to the circulation of the stratosphere may help explain the large spread in the rate of change of tropical upwelling seen in previous studies.

Oman, Luke↗
NASA NTRSDate not supplied

CERES Top-of-atmosphere and Surface fluxes in the Arctic: A comparison with ARISE and MOSAiC measurements

Uncertainty in the NASA Clouds and the Earth’s Radiant Energy System (CERES)-derived irradiances is larger over sea ice than any other surface type and comes from several sources. This presentation summarizes results from comparisons of CERES data with the year-long Multidisciplinary drifting Observatory for the Study of Arctic Climate (MOSAiC) expedition in the central Arctic and the Arctic Radiation and Icebridge Sea ice Experiment (ARISE). The CERES Synoptic 1degree (SYN1deg) product overestimates the downwelling shortwave flux by 11.40 Wm–2 and underestimates the upwelling shortwave flux by –15.70 Wm–2 and downwelling longwave fluxes by –12.58 Wm–2 at the surface during summer. In addition, large differences are found in the upwelling longwave flux when the surface approaches the melting point (approximately 0C). The large negative bias in upwelling shortwave flux can be attributed in large part to lower surface albedo (–0.15) in satellite footprint relative to surface sensors. The CERES-MOSAiC broadband albedo differences (approximately 20 Wm–2) explain a larger portion of the upwelling shortwave flux difference than the spectral albedo shape differences (approximately 3 Wm–2). The ARISE results indicate the some of these differences in the SW are due to the scene identification and representation of anisotropy in partly cloud scenes. Switching from imager-based to passive microwave-based sea ice data in the CERES inversion process reduces the differences in the grid box average fluxes and in the sea ice partly cloudy scene anisotropy in the instantaneously-matched footprints. Our analysis indicates that calibration and sampling uncertainty limit the ability to place strong constraints (<7%) on CERES TOA fluxes with aircraft measurements. The results indicate that improvements in the surface albedo and cloud data would substantially reduce the uncertainty in the Arctic surface radiation budget derived from CERES data products.

Patrick C Taylor↗
NASA NTRS2023

Connections Between Upper Tropospheric and Lower Stratospheric Circulation Responses to Increased Co 2

There are a myriad of ways atmospheric circulation responds to increased CO 2 . In the troposphere, the region of the tropical upwelling narrows, the Hadley Cells expand, and the upper level subtropical zonal winds that comprise the subtropical jet strengthen. In the stratosphere, the tropical upwelling narrows and strengthens, enhancing the Brewer-Dobson Circulation. Despite the robustness of these projections, dynamical coupling between the features remains unclear. In this study, we analyze output from the NASA Goddard Institute for Space Studies (GISS) ModelE coupled climate model to examine any connection between the upper tropospheric and lower stratospheric circulation by considering the features’ seasonality, hemispheric asymmetry, scaling, and transient response to a broad range of CO 2 forcings. We find that a narrowing and strengthening of upper tropospheric upwelling occurs with a strengthening of the subtropical jet. There is also a narrowing and strengthening of lower stratospheric upwelling that is related to an equatorward shift in critical latitude for wave breaking and the associated strengthening of the subtropical lower stratosphere’s zonal winds. However, the stratospheric responses display different seasonal, hemispheric, and transient patterns than those in the troposphere, indicating independent circulation changes between the two domains.

Molly E. Menzel↗
NASA NTRS1999

Origin of Corona-Dominated Topographic Rises on Venus

Both large-scale mantel upwellings, comparable to terrestrial hotspots on Earth, and smaller scale mantel upwellings, known as coronae, occur on Venus. Corona-dominated rises have many of the characteristics of large scale mantle upwellings, or hotspots, such as broad topographic rises greater than 1000km in diameter and large positive gravity anomalies.

Venus Corona-dominated rises hotspots mantle upwel↗
DOE OSTI2012

Simulation of annual biogeochemical cycles of nutrient balance, phytoplankton bloom(s), and DO in Puget Sound using an unstructured grid model

Nutrient pollution from rivers, nonpoint source runoff, and nearly 100 wastewater discharges is a potential threat to the ecological health of Puget Sound with evidence of hypoxia in some basins. However, the relative contributions of loads entering Puget Sound from natural and anthropogenic sources, and the effects of exchange flow from the Pacific Ocean are not well understood. Development of a quantitative model of Puget Sound is thus presented to help improve our understanding of the annual biogeochemical cycles in this system using the unstructured grid Finite-Volume Coastal Ocean Model framework and the Integrated Compartment Model (CE-QUAL-ICM) water quality kinetics. Results based on 2006 data show that phytoplankton growth and die-off, succession between two species of algae, nutrient dynamics, and dissolved oxygen in Puget Sound are strongly tied to seasonal variation of temperature, solar radiation, and the annual exchange and flushing induced by upwelled Pacific Ocean waters. Concentrations in the mixed outflow surface layer occupying approximately 5–20 m of the upper water column show strong effects of eutrophication from natural and anthropogenic sources, spring and summer algae blooms, accompanied by depleted nutrients but high dissolved oxygen levels. The bottom layer reflects dissolved oxygen and nutrient concentrations of upwelled Pacific Ocean water modulated by mixing with biologically active surface outflow in the Strait of Juan de Fuca prior to entering Puget Sound over the Admiralty Inlet. The effect of reflux mixing at the Admiralty Inlet sill resulting in lower nutrient and higher dissolved oxygen levels in bottom waters of Puget Sound than the incoming upwelled Pacific Ocean water is reproduced. Finally, by late winter, with the reduction in algal activity, water column constituents of interest, were renewed and the system appeared to reset with cooler temperature, higher nutrient, and higher dissolved oxygen waters from the Pacific Ocean.

biogeochemical model, 3-D hydrodynamic model, nutr↗
DOE OSTI2018

A hybrid origin of the Martian crustal dichotomy: Degree-1 convection antipodal to a giant impact

The Martian crustal dichotomy is the stark ~5 km difference in surface elevation and ~26 km difference in crustal thickness between the northern lowlands and southern highlands that originated within 100s of Myr of Mars’ formation. The origin of the dichotomy has broad implications for the geodynamic history of Mars, but purely exogenic or endogenic theories so far cannot explain all of the large scale geophysical observations associated with dichotomy formation. A giant impact can produce the shape and slope of the dichotomy boundary, but struggles to explain Mars’ remanent crustal magnetic signatures and the ultimate formation of Tharsis. Degree-1 mantle convection can relate the crustal dichotomy to the formation of Tharsis, but does not explain the elliptical dichotomy shape and must be initiated by a large pre-existing viscosity jump in the mantle. We propose a hybrid model of dichotomy formation in which a giant impact induces degree-1 convection with an upwelling antipodal to the impact site. In this scenario, a giant impact in the northern hemisphere excavates crust, creating an initial difference in crustal thickness and possibly composition between the two hemispheres. Over 10s to 100s of Myr, the dominant upwelling(s) would migrate to be under the thicker, insulating crust in the southern hemisphere, generating melt that further thickens the southern crust. We examine this process using 3-D mantle convection simulations, and find that a hemispherical difference in crustal thickness and composition caused by a giant impact can induce degree-1 convection with the upwelling(s) antipodal to the impact site in <100 Myr.

58 GEOSCIENCES↗
DOE OSTI2015

Back to the future: using historical climate variation to project near-term shifts in habitat suitable for coast redwood

Studies that mimic the effect of climate change on terrestrial ecosystems often use climate projections from downscaled global climate models (GCMs). These simulations are generally too coarse to capture patterns of fine-scale climate variation, such as the sharp coastal energy and moisture gradients associated with wind-driven upwelling of cold water. Coastal upwelling may limit future increases in coastal temperatures, compromising GCMs' ability to provide realistic scenarios of future climate in these coastal ecosystems. Taking advantage of naturally occurring variability in the high-resolution historic climatic record, we developed multiple fine-scale scenarios of California climate that maintain coherent relationships between regional climate and coastal upwelling. We compared these scenarios against coarse resolution GCM projections at a regional scale to evaluate their temporal equivalency. We utilized these historically based scenarios to estimate potential suitable habitat for coast redwood (Sequoia sempervirens D. Don) under 'normal' combinations of temperature and precipitation, and under anomalous combinations representative of potential future climates. We found that a scenario of warmer temperature with historically normal precipitation is equivalent to climate projected by GCMs for California by 2020-2030 and that under these conditions, climatically suitable habitat for coast redwood significantly contracts at the southern end of its current range. Our results indicate that historical climate data provide a high-resolution alternative to downscaled GCM outputs for near-term ecological forecasts. This method may be particularly useful in other regions where local climate is strongly influenced by ocean-atmosphere dynamics that are not represented by coarse-scale GCMs.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2019

Collaborative Project: Three-Dimensional Structure of the Southern Ocean Overturning Circulation

The large-scale upwelling in the Southern Ocean provides a pathway for the deep and abyssal water masses of the global ocean to return to the surface, creating a mechanism for the exchange of carbon and heat between the deep ocean water masses and the atmosphere. Despite the significance of the overturning circulation in the Southern Ocean for global climate, very little is known about the depth and longitudinal distribution of the overturning pathways and their influence on heat uptake, regional sea level change and ocean carbon transport. The focus of this grant was to assess the three-dimensional structure of the Southern Ocean overturning circulation in models and observations, with the following three objectives: 1. Quantify and contrast modeled (using GFDL and CESM models) and observed (Argo based) upwelling pathways in the Southern Ocean. 2. Evaluate the impact of model resolution on transport pathways and the associated meridional fluxes of heat and salt. 3. Determine the influence of climate-driven changes in upwelling on the regional patterns and magnitude of heat and carbon uptake and sea level change. We have successfully achieved our three objectives through (1) running Southern Ocean particle tracking simulations in global coupled models with varying resolutions, and (2) quantifying the role played by the overturning circulation and its changes to the surface heat and carbon uptake, in climate models as well as observations. The research funded under this grant led to 8 published papers and 2 submitted papers, with 2 additional papers in preparation.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2017

Chasing the Future: How Will Ocean Change Affect Marine Life?

Understanding the potential consequences of rising ocean carbon levels and related ocean changes for marine life and ecosystems is a high priority for the ocean research community and marine resource management. In the mid-1990s, two geoengineering proposals to mitigate global warming by carbon sequestration in the deep sea led to research measuring the effects of increased deep ocean carbon dioxide levels on marine animals. A few years later, ocean acidification and its effects on marine life became an international research priority. Here we provide an overview of several technical developments by scientists and engineers at the Monterey Bay Aquarium Research Institute (MBARI) that have enabled and enhanced deep-sea exploration and experiments to assess the effects of changing ocean conditions on benthic marine animals. Improvements in remotely operated vehicles (ROVs) have increased the efficiency of dive operations and enabled more complex measurements and experiments at great ocean depths. In situ respirometers and Free Ocean CO 2 Enrichment (FOCE) mesocosms have allowed measurement of physiological and behavioral responses of deep-sea animals to environmental change. A laboratory-based, gas-controlled aquarium system that regulates oxygen and pH in chilled waters was engineered to measure the physiological responses of deep-sea animals and biological communities to expected future environmental conditions. Recently, MBARI engineers and scientists developed an Upwelling Simulator, a lab-based aquarium control system that mimics ocean conditions during coastal upwelling. This system is programmable, allowing independent control of pH, oxygen, and temperature to enable experiments that examine the effects of present-day upwelling conditions, expected future conditions, or other changes in these environmental conditions. In sum, collaboration between the marine operations group, engineers, and scientists at MBARI has advanced methods to explore the ocean and understand the consequences of ocean change for marine organisms and ecosystems.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1976

Retrieval of surface temperature by remote sensing

A simple procedure and computer program were developed for retrieving the surface temperature from the measurement of upwelling infrared radiance in a single spectral region in the atmosphere. The program evaluates the total upwelling radiance at any altitude in the region of the CO fundamental band (2070-2220 1/cm) for several values of surface temperature. Actual surface temperature is inferred by interpolation of the measured upwelling radiance between the computed values of radiance for the same altitude. Sensitivity calculations were made to determine the effect of uncertainty in various surface, atmospheric and experimental parameters on the inferred value of surface temperature. It is found that the uncertainties in water vapor concentration and surface emittance are the most important factors affecting the accuracy of the inferred value of surface temperature.

Gupta, S. K.↗
NASA NTRS1982

Influence of dissolved organic materials on turbid water optical properties and remote-sensing reflectance

The effects of dissolved organic materials on turbid-water optical properties are assessed, by means of field measurements and laboratory simulations in which upwelled reflectance, attenuation, absorption, and backscatter spectral properties at wavelengths from 450 to 800 nm are examined in relation to water chemistry. The data show that dissolved organic materials decrease upwelled reflectance from turbid waters, and that the decrease in reflectance is a nonlinear function of concentration with the largest gradients at low carbon concentrations, depending on wavelength. Upwelled reflectance is found to be highly correlated with two backscatter-absorption parameters used in some optical models, which are nonlinear with dissolved organic material concentration change.

Witte, W. G.↗
NASA NTRS1983

Analysis of longwave radiation for the Earth-atmosphere system

Accurate radiative transfer models are used to determine the upwelling atmospheric radiance and net radiative flux in the entire longwave spectral range. The validity of the quasi-random band model is established by comparing the results of this model with those of line-by-line formulations and with available theoretical and experimental results. Existing radiative transfer models and computer codes are modified to include various surface and atmospheric effects (surface reflection, nonequilibrium radiation, and cloud effects). The program is used to evaluate the radiative flux in clear atmosphere, provide sensitivity analysis of upwelling radiance in the presence of clouds, and determine the effects of various climatological parameters on the upwelling radiation and anisotropic function. Homogeneous and nonhomogeneous gas emissivities can also be evaluated under different conditions.

Tiwari, S. N.↗
NASA NTRS1985

A coupled ice-ocean model of ice breakup and banding in the marginal ice zone

A coupled ice-ocean numerical model for the marginal ice zone is considered. The model consists of a nonlinear sea ice model and a two-layer (reduced gravity) ocean model. The dependence of the upwelling response on wind stress direction is discussed. The results confirm earlier analytical work. It is shown that there exist directions for which there is no upwelling, while other directions give maximum upwelling in terms of the volume of uplifted water. The ice and ocean is coupled directly through the stress at the ice-ocean interface. An interesting consequence of the coupling is found in cases when the ice edge is almost stationary. In these cases the ice tends to break up a few tenths of kilometers inside of the ice edge.

Smedstad, O. M.↗