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NASA NTRS2005

Proposal to Simultaneously Profile Wind and CO2 on Earth and Mars With 2-micron Pulsed Lidar Technologies

2-micron lidar technology has been in use and under continued improvement for many years toward wind measurements. But the 2-micron wavelength region is also rich in absorption lines of CO2 (and H2O to a lesser extent) that can be exploited with the differential absorption lidar (DIAL) technique to make species concentration measurements. A coherent detection receiver offers the possibility of making combined wind and DIAL measurements with wind derived from frequency shift of the backscatter spectrum and species concentration derived from power of the backscatter spectrum. A combined wind and CO2 measurement capability is of interest for applications on both Earth and Mars. CO2 measurements in the Earth atmosphere are of importance to studies of the global carbon cycle. Data on vertically-resolved CO2 profiles over large geographical observations areas are of particular interest that could potentially be made by deploying a lidar on an aircraft or satellite. By combining CO2 concentration with wind measurements an even more useful data product could be obtained in the calculation of CO2 flux. A challenge to lidar in this application is that CO2 concentration measurements must be made with a high level of precision and accuracy to better than 1%. The Martian atmosphere also presents wind and CO2 measurement problems that could be met with a combined DIAL/Doppler lidar. CO2 concentration in this scenario would be used to calculate atmospheric density since the Martian atmosphere is composed of 95% CO2. The lack of measurements of Mars atmospheric density in the 30-60 km range, dust storm formation and movements, and horizontal wind patterns in the 0-20 km range pose significant risks to aerocapture, and entry, descent, and landing of future robotic and human Mars missions. Systematic measurement of the Mars atmospheric density and winds will be required over several Mars years, supplemented with day-of-entry operational measurements. To date, there have been 5 successful robotic landings on Mars. Atmospheric density and wind reconstruction has been performed for 3 of these entries (the two Viking landers and Mars Pathfinder). At present, all Mars atmospheric density and wind models have these 3 entries (at widely scattered positions and seasons) as their basis, supplemented by coarse orbital measurements of atmospheric opacity and temperature. This lack of data leads to a large uncertainty in prediction of the Mars atmospheric density and winds in the altitude regime where deceleration of landers will occur. This uncertainty will have a dramatically large impact on mass, cost and risk. The precision and accuracy for application to Mars is not as stringent as Earth, but Mars does pose a challenge in needing a high level of wavelength stability and control in order to reference wavelength to the narrow linewidths found in the low atmospheric pressure of Mars, as illustrated in Figure 1.

Singh, Upendra N.↗

NASA NTRS2002

Double Layers in Expanding Plasmas and Their Relevance to the Auroral Plasma Processes

When a dense plasma consisting of a cold and a sufficiently warm electron population expands, a rarefaction shock forms. In the expansion of the polar wind in the magnetosphere, it has been previously shown that when a sufficiently warm electron population also exists, in addition to the usual cold ionospheric one, a discontinuity forms in the electrostatic potential distribution along the magnetic field lines. Despite the lack of spatial resolution and the assumption of quasi-neutrality in the polar wind models, such discontinuities have been called double layers (DLs). Recently similar discontinuities have been invoked to partly explain the auroral acceleration of electrons and ions in the upward current region. By means of one-dimensional Vlasov simulations of expanding plasmas, for the first time we make here the connection between (i) the rarefaction shocks, (ii) the discontinuities in the potential distributions, and (iii) DLs. We show that when plasmas expand from opposite directions into a deep density cavity with a potential drop across it and when the plasma on the high-potential side contains two electron populations, the temporal evolution of the potential and the plasma. distribution generates evolving multiple double layers with an extended density cavity between them. One of the DLs is the rarefaction-shock (RFS) and it forms by the reflections of the cold electrons coming from the high-potential side; it supports a part of the potential drop approximately determined by the hot electron temperature.

Singh, Nagendra↗

NASA NTRS2011

Use of Dual-Polarization Radar Variables to Assess Low-Level Wind Shear in Severe Thunderstorm Near-storm Environments in the Tennessee Valley

The upgrade of the National Weather Service (NWS) network of S ]band dual-polarization radars is currently underway, and the incorporation of polarimetric information into the real ]time forecasting process will enhance the forecaster fs ability to assess thunderstorms and their near ]storm environments. Recent research has suggested that the combination of polarimetric variables differential reflectivity (ZDR) and specific differential phase (KDP) can be useful in the assessment of low level wind shear within a thunderstorm. In an environment with strong low ]level veering of the wind, ZDR values will be largest along the right inflow edge of the thunderstorm near a large gradient in horizontal reflectivity (indicative of large raindrops falling with a relative lack of smaller drops), and take the shape of an arc. Meanwhile, KDP values, which are proportional to liquid water content and indicative of a large number of smaller drops, are maximized deeper into the forward flank precipitation shield than the ZDR arc as the smaller drops are being advected further from the updraft core by the low level winds than the larger raindrops. Using findings from previous work, three severe weather events that occurred in North Alabama were examined in order to assess the utility of these signatures in determining the potential for tornadic activity. The first case is from October 26, 2010, where a large number of storms indicated tornadic potential from a standard reflectivity and velocity analysis but very few storms actually produced tornadoes. The second event is from February 28, 2011, where tornadic storms were present early on in the event, but as the day progressed, the tornado threat transitioned to a high wind threat. The third case is from April 27, 2011, where multiple rounds of tornadic storms ransacked the Tennessee Valley. This event provides a dataset including multiple modes of tornadic development, including QLCS and supercell structures. The overarching goal of examining these three events is to compare dual ]polarization features from this larger dataset to previous work and to determine if these signatures can be a useful indication of the potential for tornadic activity associated with the amount of low ]level wind shear in the near ]storm environment.

Crowe, Christina C.↗

NASA NTRS2015

Simulated Tiltrotor Aircraft Operation in Close Proximity to a Building in Wind and Ground-Effect Conditions

A mid-fidelity computational fluid dynamics tool called RotCFD specifically developed to aid in rotorcraft studies has been applied to the study of wake interactions of civiltiltrotor aircraft in the immediate vicinity of buildings, in- and out-of-ground-effect, with and without winds, consistent with notional tiltrotor operations from urban vertiports. Such civil tiltrotor operations from urban vertiports could potentially enable city-center-to-city center commercial transport. However, in order to one day realize such civil tiltrotor operations, though, it is necessary to better understand the wake interaction and interactional aerodynamic operating environment of urban vertiports. In the early 2000s, a series of 7-by-10 Ft. wind tunnel tests were conducted at NASA Ames Research Center that began to explore some of these civil tiltrotor and vertiport wake interactioninteractional aerodynamics issues. This study seeks to validate computation fluid dynamic predictions against these early wind tunnel experimental results and, thereby, continue exploration of this important research area.

Rotorcraft↗

NASA NTRS2009

Integration of the Radiation Belt Environment Model Into the Space Weather Modeling Framework

We have integrated the Fok radiation belt environment (RBE) model into the space weather modeling framework (SWMF). RBE is coupled to the global magnetohydrodynamics component (represented by the Block-Adaptive-Tree Solar-wind Roe-type Upwind Scheme, BATS-R-US, code) and the Ionosphere Electrodynamics component of the SWMF, following initial results using the Weimer empirical model for the ionospheric potential. The radiation belt (RB) model solves the convection-diffusion equation of the plasma in the energy range of 10 keV to a few MeV. In stand-alone mode RBE uses Tsyganenko's empirical models for the magnetic field, and Weimer's empirical model for the ionospheric potential. In the SWMF the BATS-R-US model provides the time dependent magnetic field by efficiently tracing the closed magnetic field-lines and passing the geometrical and field strength information to RBE at a regular cadence. The ionosphere electrodynamics component uses a two-dimensional vertical potential solver to provide new potential maps to the RBE model at regular intervals. We discuss the coupling algorithm and show some preliminary results with the coupled code. We run our newly coupled model for periods of steady solar wind conditions and compare our results to the RB model using an empirical magnetic field and potential model. We also simulate the RB for an active time period and find that there are substantial differences in the RB model results when changing either the magnetic field or the electric field, including the creation of an outer belt enhancement via rapid inward transport on the time scale of tens of minutes.

Glocer, A.↗

NASA NTRS2018

ALMA Spectral Line and Imaging Survey of a Low and a High Mass-Loss Rate AGB Star Between 335 and 362 GHz

Context. Low and intermediate mass stars are known to power strong stellar winds when evolving through the asymptotic giant branch (AGB) phase. Initial mass, luminosity, temperature, and composition determine the pulsation characteristics of the star and the dust species formed in the pulsating photospheric layers. Radiation pressure on these grains triggers the onset of a stellar wind. However, as of today, we still cannot predict the wind mass-loss rates and wind velocities from first principles neither do we know which species are the first to condense in the upper atmospheric regions. Aims. We aim to characterise the dominant physical, dynamical, and chemical processes in the inner wind region of two archetypical oxygen-rich (C/O < 1) AGB stars, that is, the low mass-loss rate AGB star R Dor (M’ ∼ 1 × 10(exp −7) M/yr) and the high mass-loss rate AGB star IK Tau (M’ ∼ 5 × 10(exp −6) M/yr). The purpose of this study is to observe the key molecular species contributing to the formation of dust grains and to cross-link the observed line brightnesses of several species to the global and local properties of the star and its wind. Methods. A spectral line and imaging survey of IK Tau and R Dor was made with ALMA between 335 and 362 GHz (band 7) at a spatial resolution of ∼150 mas, which corresponds to the locus of the main dust formation region of both targets. Results. Some two hundred spectral features from 15 molecules (and their isotopologues) were observed, including rotational lines in both the ground and vibrationally excited states (up to v = 5 for SiO). Detected species include the gaseous precursors of dust grains such as SiO, AlO, AlOH, TiO, and TiO2. We present a spectral atlas for both stars and the parameters of all detected spectral features. A clear dichotomy for the sulphur chemistry is seen: while CS, SiS, SO, and SO2 are abundantly present in IK Tau, only SO and SO2 are detected in R Dor. Also other species such as NaCl, NS, AlO, and AlOH display a completely different behaviour. From some selected species, the minor isotopologues can be used to assess the isotopic ratios. The channel maps of many species prove that both large and small-scale inhomogeneities persist in the inner wind of both stars in the form of blobs, arcs, and/or a disk. The high sensitivity of ALMA allows us to spot the impact of these correlated density structures in the spectral line profiles. The spectral lines often display a half width at zero intensity much larger than expected from the terminal velocity, v∞, previously derived for both objects (36 km/s versus v(∞) ∼ 17.7 km/s for IK Tau and 23 km/s versus v(∞) ∼ 5.5 km/s for R Dor). Both a more complex 3D morphology and a more forceful wind acceleration of the (underlying) isotropic wind can explain this trend. The formation of fractal grains in the region beyond ∼400 mas can potentially account for the latter scenario. From the continuum map, we deduce a dust mass of ∼3.7 × 10(exp −7) Mand ∼2 × 10(exp −8) M for IK Tau and R Dor, respectively. Conclusions. The observations presented here provide important constraints on the properties of these two oxygen-dominated AGB stellar winds. In particular, the ALMA data prove that both the dynamical and chemical properties are vastly different for this high mass-loss rate (IK Tau) and low mass-loss rate (R Dor) star.

L. Decin↗

NASA NTRS1995

Three-dimensional aerodynamic analysis of a subsonic transport high-lift configuration and comparisons with wind-tunnel test results

The sizing and efficiency of an aircraft is largely determined by the performance of its high-lift system. Subsonic civil transports most often use deployable multi-element airfoils to achieve the maximum-lift requirements for landing, as well as the high lift-to-drag ratios for take-off. However, these systems produce very complex flow fields which are not fully understood by the scientific community. In order to compete in today's market place, aircraft manufacturers will have to design better high-lift systems. Therefore, a more thorough understanding of the flows associated with these systems is desired. Flight and wind-tunnel experiments have been conducted on NASA Langley's B737-100 research aircraft to obtain detailed full-scale flow measurements on a multi-element high-lift system at various flight conditions. As part of this effort, computational aerodynamic tools are being used to provide preliminary flow-field information for instrumentation development, and to provide additional insight during the data analysis and interpretation process. The purpose of this paper is to demonstrate the ability and usefulness of a three-dimensional low-order potential flow solver, PMARC, by comparing computational results with data obtained from 1/8 scale wind-tunnel tests. Overall, correlation of experimental and computational data reveals that the panel method is able to predict reasonably well the pressures of the aircraft's multi-element wing at several spanwise stations. PMARC's versatility and usefulness is also demonstrated by accurately predicting inviscid three-dimensional flow features for several intricate geometrical regions.

Edge, D. Christian↗

NASA NTRS2004

Global Geospace Science (GGS)/POLAR Thermal Ion Dynamics Experiments (TIDE) Co-Investigator Program: Mission Operations and Data Analysis (MO/DA)

We have pursued several investigations using the Polar/TIDE data set. The first was a comparison of TIDE high-altitude observations with similar ion flux signatures in the Los Alamos National Laboratory (LANL) magnetospheric plasma analyzer (MPA) data. There are several geosynchronously orbiting satellites with LANL MPA instruments onboard. When the satellite is immersed in fresh plasma sheet electrons, the spacecraft voltage drops to several hundred volts negative, and cold ions are accelerated in to the detector. In the LANL MPA spectrograms, the accelerated cold ions appear as a bright, narrow line, following the voltage of the spacecraft. This "ion line" is seen regularly on the nightside, but has not received much attention. The Polar TIDE observations indicated a ubiquitous "lobal wind" in the near-- magnetotail, a field-aligned stream of approx. 100 eV ions flowing out of both polar ionospheres. The interesting result of this research is that the MPA ion line is also peaked in the field-aligned direction, even though the potential well should be uniform in all directions. It is believed that this is evidence that the lobal winds not only populate the high-latitude lobes, but fill the lobes all the way in to the near-Earth plasma sheet (the location of geosynchronous orbit). This activity developed into a full-scale survey of the lobal wind observations in the TIDE database. The universality of these observations with respect to local time and solar wind conditions implies that the ionospheric outflow is supplying the near-Earth plasma sheet at all times, regardless of magnetic activity. We have conducted a statistical study of the characteristics of the lobal wind in these two data sets FIDE and LANL MPA), finding much similarity between them. Using these characteristics as input conditions to our inner magnetosphere ion transport model, we have conducted simulations of the flow of these particles inside of geosynchronous orbit to show the impact these particles will have on the near-Earth space environment. As the study has progressed, these results have been presented several times to the TIDE team during teleconferences. It is planned to present this survey at the GEM 2004 Summer Workshop, and hopefully at additional conferences in the near future. We are presently writing a paper on the lobal wind occurrence statistics, which should be submitted in April or May to the Journal of Geophysical Research for publication. An undergraduate student at the University of Alabama in Huntsville, Will Maddox, working at NASA MSFC with Dr. Paul Craven, is presently creating a database of the values TIDE moments for the lobal wind (under Dr. Liemohn's guidance), and this will be the focus of a follow-on paper.

Nagy, Andrew↗

NASA NTRS2021

Wind suppression by X-rays in Cygnus X-3

Context: The radiatively driven wind of the primary star in wind-fed X-ray binaries can be suppressed by the X-ray irradiation of the compact secondary star. This causes feedback between the wind and the X-ray luminosity of the compact star. Aims: We aim to estimate how the wind velocity on the face-on side of the donor star depends on the spectral state of the high-mass X-ray binary Cygnus X-3. Methods: We modeled the supersonic part of the wind by computing the line force (force multiplier) with the Castor, Abbott & Klein formalism and XSTAR physics and by solving the mass conservation and momentum balance equations. We computed the line force locally in the wind considering the radiation fields from both the donor and the compact star in each spectral state. We solved the wind equations at different orbital angles from the line joining the stars and took the effect of wind clumping into account. Wind-induced accretion luminosities were estimated using the Bondi-Hoyle-Lyttleton formalism and computed wind velocities at the compact star. We compared them to those obtained from observations. Results: We found that the ionization potentials of the ions contributing the most to the line force fall in the extreme-UV region(100–230 Å). If the flux in this region is high, the line force is weak, and consequently, the wind velocity is low. We found a correlation between the luminosities estimated from the observations for each spectral state of Cyg X-3 and the computed accretion luminosities assuming moderate wind clumping and a low mass of the compact star. For high wind clumping, this correlation disappears. We compared the XSTAR method used here with the comoving frame method and found that they agree reasonably well with each other. Conclusions. We show that soft X-rays in the extreme-UV region from the compact star penetrate the wind from the donor star and diminish the line force and consequently the wind velocity on the face-on side. This increases the computed accretion luminosities qualitatively in a similar manner as observed in the spectral evolution of Cyg X-3 for a moderate clumping volume filling factor and a compact star mass of a few (2–3) solar masses.

O. Vilhu↗

NASA NTRS2018

ALMA Spectral Line and Imaging Survey of a Low and a High Mass-Loss Rate AGB Star Between 335 and 362 GHz

Context. Low and intermediate mass stars are known to power strong stellar winds when evolving through the asymptotic giant branch (AGB) phase. Initial mass, luminosity, temperature, and composition determine the pulsation characteristics of the star and the dust species formed in the pulsating photospheric layers. Radiation pressure on these grains triggers the onset of a stellar wind. However, as of today, we still cannot predict the wind mass-loss rates and wind velocities from first principles neither do we know which species are the first to condense in the upper atmospheric regions. Aims. We aim to characterise the dominant physical, dynamical, and chemical processes in the inner wind region of two archetypical oxygen-rich (C/O<1) AGB stars, that is, the low mass-loss rate AGB star R Dor (M~ 1x10(exp 7) M☉/yr) and the high mass-loss rate AGB star IK Tau (M~5x10(exp 6) M☉/yr). The purpose of this study is to observe the key molecular species contributing to the formation of dust grains and to cross-link the observed line brightnesses of several species to the global and local properties of the star and its wind. Methods. A spectral line and imaging survey of IK Tau and R Dor was made with ALMA between 335 and 362 GHz (band 7) at a spatial resolution of ~150 mas, which corresponds to the locus of the main dust formation region of both targets. Results. Some two hundred spectral features from 15 molecules (and their isotopologues) were observed, including rotational lines in both the ground and vibrationally excited states (up to v=5 for SiO). Detected species include the gaseous precursors of dust grains such as SiO, AlO, AlOH, TiO, and TiO2.We present a spectral atlas for both stars and the parameters of all detected spectral features. A clear dichotomy for the sulphur chemistry is seen: while CS, SiS, SO, and SO2 are abundantly present in IK Tau, only SO and SO2 are detected in R Dor. Also other species such as NaCl, NS, AlO, and AlOH display a completely different behaviour. From some selected species, the minor isotopologues can be used to assess the isotopic ratios. The channel maps of many species prove that both large and small-scale inhomogeneities persist in the inner wind of both stars in the form of blobs, arcs, and/or a disk. The high sensitivity of ALMA allows us to spot the impact of these correlated density structures in the spectral line profiles. The spectral lines often display a half width at zero intensity much larger than expected from the terminal velocity, v1, previously derived for both objects (36 km/s versus v(∞)~17.7 km/s for IK Tau and 23 km/s versus v(∞)~5.5 km/s for R Dor). Both a more complex 3D morphology and a more forceful wind acceleration of the (underlying) isotropic wind can explain this trend. The formation of fractal grains in the region beyond _400 mas can potentially account for the latter scenario. From the continuum map, we deduce a dust mass of ~3.7 x 10(exp 7) M☉ and ~2 x 10(ex0 8) M☉ for IK Tau and R Dor, respectively. Conclusions. The observations presented here provide important constraints on the properties of these two oxygen-dominated AGB stellar winds. In particular, the ALMA data prove that both the dynamical and chemical properties are vastly different for this high mass-loss rate (IK Tau) and low mass-loss rate (R Dor) star.

Stars: AGB and post-AGB, Stars: mass loss, Stars: ↗

NASA NTRS1974

Upper-surface blowing nacelle design study for a swept wing airplane at cruise conditions

A study was made to design two types of overwing nacelles for an existing wing-body at a design condition of Mach = 0.8 and C sub L = 0.2. Internal and external surface contours were developed for nacelles having either a D-shaped nozzle or a high-aspect-ratio nozzle for upper-surface blowing in the powered-lift mode of operation. The goal of the design was the development of external nacelle lines that would minimize high-speed aerodynamic interference effects. Each nacelle type was designed for both two- and four-engine airplanes using an iterative process of aerodynamic potential flow analysis. Incremental nacelle drag estimates were made for flow-through wind tunnel models of each configuration.

Gillette, W. B.↗

NASA NTRS1975

Quasi-exospheric heat flux of solar-wind electrons

Eviatar, A.↗

NASA NTRS1976

Quasi-exospheric heat flux of solar-wind electrons

Density, bulk-velocity, and heat-flow moments are calculated for truncated Maxwellian distributions representing the cool and hot populations of solar-wind electrons, as realized at the base of a hypothetical exosphere. The electrostatic potential is calculated by requiring charge quasi-neutrality and the absence of electrical current. Plasma-kinetic coupling of the cool-electron and proton bulk velocities leads to an increase in the electrostatic potential and a decrease in the heat-flow moment. If the velocities differ by the Alfven speed along the magnetic field, for example, the potential rises to 72.6 V and the heat flux falls to 0.0272 erg/sq cm per sec. In each case, the heat flux is carried mainly by the quasi-exospheric hot electrons.

Eviatar, A.↗

NASA NTRS1976

Flight evaluation of advanced navigation techniques for general aviation using frequency scanning

Experiments on an automatic multisensor navigation concept are being conducted in a Cessna 402B. The test system consists of VOR, DME, and air data sensors controlled by a Hewlett Packard 9820A electronic calculator which processes the data and, by means of a four-state Kalman filter, outputs position and ground and wind velocities to a map display. Novel features which make such a system potentially low-cost include frequency-scanning operation of a single VOR receiver and a single DME transceiver and use of a shed-vortex true airspeed sensor. Results obtained during flight in a local area where six to eight DME NAVAIDS were receivable yielded better than 1/4-mile accuracy.

Jackson, C. T., Jr.↗

NASA NTRS1979

Leading edge vortex-flap experiments on a 74 deg delta wing

Exploratory wind tunnel tests are reported on a 74 deg. delta wing model. The potential of a vortex flap concept in reducing the subsonic lift dependent drag of highly swept, slender wings is examined. The suction effect of coiled vortices generated through controlled separation over leading edge flap surfaces to produce a thrust component is discussed. A series of vortex-flap configurations were investigated to explore the effect of some primary geometric variables.

Rao, D. M.↗

NASA NTRS1982

A unique flight test facility - Description and results

The Dryden Flight Research Facility has developed a unique research facility for conducting aerodynamic and fluid mechanics experiments in flight. A low aspect ratio fin, referred to as the flight test fixture (FTF), is mounted on the underside of the fuselage of an F-104G aircraft. The F-104/FTF facility is described, and the capabilities are discussed. The capabilities include (1) a large Mach number envelope (0.4 to 2.0), including the region through Mach 1.0; (2) the potential ability to test articles larger than those that can be tested in wind tunnels; (3) the large chord Reynolds number envelope (greater than 40 million); and (4) the ability to define small increments in friction drag between two test surfaces. Data are presented from experiments that demonstrate some of the capabilities of the FTF, including the shuttle thermal protection system airload tests, instrument development, and base drag studies. Proposed skin friction experiments and instrument evaluation studies are also discussed.

Meyer, R. R., Jr.↗

NASA NTRS1982

A unique flight test facility: Description and results

The Dryden Flight Research Facility has developed a unique research facility for conducting aerodynamic and fluid mechanics experiments in flight. A low aspect ratio fin, referred to as the flight test fixture (FTF), is mounted on the underside of the fuselage of an F-104G aircraft. The F-104G/FTF facility is described, and the capabilities are discussed. The capabilities include (1) a large Mach number envelope (0.4 to 2.0), including the region through Mach 1.0; (2) the potential ability to test articles larger than those that can be tested in wind tunnels; (3) the large chord Reynolds number envelope (greater than 40 million); and (4) the ability to define small increments in friction drag between two test surfaces. Data are presented from experiments that demonstrate some of the capabilities of the FTF, including the shuttle thermal protection system airload tests, instrument development, and base drag studies. Proposed skin friction experiments and instrument evaluation studies are also discussed.

Meyer, R. R., Jr.↗

NASA NTRS1984

Air-sea heat exchange, an element of the water cycle

The distribution and variation of water vapor, clouds and precipitation are examined. Principal driving forces for these distributions are energy exchange and evaporation at the air-sea interface, which are also important elements of air-sea interaction studies. The overall aim of air-sea interaction studies is to quantitatively determine mass, momentum and energy fluxes, with the goal of understanding the mechanisms controlling them. The results of general circulation simulations indicate that the atmosphere in mid-latitudes responds to changes in the oceanic surface conditions in the tropics. This correlation reflects the strong interaction between tropical and mid-latitude conditions caused by the transport of heat and momentum from the tropics. Studies of air-sea exchanges involve a large number of physica, chemical and dynamical processes including heat flux, radiation, sea-surface temperature, precipitation, winds and ocean currents. The fluxes of latent heat are studied and the potential use of satellite data in determining them evaluated. Alternative ways of inferring heat fluxes will be considered.

Chahine, M. T.↗