Quantitative assessment of emergent biomass and species composition in tidal wetlands using remote sensing
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Barlett, D. S.↗
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Assessment of tidal wetland habitat and productivity
There are no author-identified significant results in this report.
Barlett, D. S.↗
Investigation of tidal displacements of the Earth's surface by laser ranging to GEOS-3
An analysis of laser ranging data from three stations was carried out in an attempt to measure the geometric Earth tide. Two different approaches to the problem were investigated. The dynamic method computes pass to pass apparent movements in stations height relative to short arcs fitted to several passes of data from the same station by the program GEODYNE. The quasi-geometric method reduces the dependence on unmodelled satellite dynamics to a knowledge of only the radial position of the satellite by considering two station simultaneous ranging at the precise time that the satellite passes through the plane defined by two stations and the center of mass of the Earth.
Bower, D. R.↗
Atmospheric tides and the rotation of Venus. I - Tidal theory and the balance of torques
Insolation absorbed by the surface of Venus is quickly redeposited at the bottom of the atmosphere. This periodic heating causes mass to flow away from the warm afternoon side of the planet and into the cooler morning region. The Sun's gravitational field exerts a torque on this atmospheric tide tending to accelerate the retrograde zonal circulation. When this torque is transmitted to the crust, it can balance the despinning effect of tides in the body of Venus. The slow retrograde rotation of Venus may be a steady state among tides in the atmosphere, tides in the solid body, and possibly the influence of the Earth.
Dobrovolskis, A. R.↗
Tidal torques on infrequently colliding particle disks in binary systems and the truncation of the asteroid belt
Conditions leading to the truncation, at the 2:1 resonance, of a disk of infrequently colliding particles surrounding the primary of a binary system are studied numerically and analytically. Attention is given to the case in which the mass ratio, q, is sufficiently small (less than about 0.1) and the radius of the disk centered on the primary allowably larger, so that first-order orbit-orbit resonances between ring material and the secondary can lie within it. Collisions are found to be less frequent than q to the -2/3 power orbital periods (the period of the forced eccentricity at the 2:1 resonance), and truncation occurs and Kirkwood gaps are produced only if the particle eccentricity is less than some critical value, estimated to be of order q to the 5/9 power, or approximately 0.02 for the sun-Jupiter case having q equal to 10 to the -3rd power.
Franklin, F. A.↗
Tidal dissipation in the moon
Euler's equations of motion, modified to include elasticity and solid friction, were used to study the rotation of the moon. Two heuristic models for the anelasticity were considered: Q independent of frequency and Q inversely proportional to the frequency and Q inversely proportional to the frequency of the strain oscillation. Parameters in each model were estimated by weighted least squares from 9 years of lunar laser range observations. The root mean square of the postfit range residuals was 19 cm in each case. For a strain period of 1 month, the estimates of Q obtained with the two models were similar and surprisingly low: 23 + or - 6. The range of uncertaintly, + or - 6, represents our estimate of the true standard deviation of the estimate of Q, as affected by systematic errors; it is 3 times larger than the formal, statistical, standard error.
Cappallo, R. J.↗
Turbulence and stress owing to gravity wave and tidal breakdown
For some years it has been accepted that tides and gravity waves propagating into the upper mesosphere from below are the major source of turbulence in the upper mesosphere. The considered investigation has the objective to examine the implications of such a situation in some detail. The main propagating diurnal mode seems to be the primary contributor at tropical latitudes. Because of the high phase speed of this mode, it is only slightly affected by the mean zonal flow of the atmosphere. Wavebreaking appears to occur around 85 km, leading to a layer of enhanced eddy diffusion and wave induced acceleration extending between 85 km and about 108 km. Above 108 km molecular transport dominates. Gravity waves appear to be dominant at middle and high latitudes. The flow distribution will effectively determine which gravity waves (depending on phase speed) can reach the mesosphere.
Lindzen, R. S.↗
In situ spectral reflectance studies of tidal wetland grasses
Field measurements of wetland spectral canopy reflectance in the Landsat-MSS wavebands were correlated with biotic factors. The highest single band correlations were observed between visible (MSS Band 4: 0.5 to 0.6 micron and Band 5: 0.6 to 0.7 micron) canopy reflectance and the percentage, by weight, of live (green) vegetation in the canopies of Spartina alterniflora (salt marsh cordgrass), Spartina patens (salt meadow grass), and Distichlis spicata (spike grass). Infrared canopy reflectance displayed significant but weaker dependence on canopy parameters such as live and total biomass and canopy height. The Band 7 (0.8 to 1.1 microns)/Band 5 (0.6 to 0.7 micron) reflectance ratio was found to be highly correlated with green biomass for S. alterniflora. Highest spectral separability between the 'low marsh' S. alterniflora and the 'high marsh' Salt Hay (S. patens and D. spicata) communities in Delaware occurs during December.
Bartlett, D. S.↗
Latitudinal (seasonal) variations in the thermospheric midnight temperature maximum - A tidal analysis
The temperature variations of the neutral gas in the thermosphere are considered as a function of local time and season, taking into account the latitude range from -17.5 deg to +17.5 deg and the altitude range from about 250 km to about 400 km. The temperature measurements were conducted in situ with the Neutral Atmospheric Temperature Experiment (NATE) on the Atmospheric Explorer E (AE-E) spacecraft during the time between December 1976 and January 1979. The altitude of the circular orbit of the spacecraft was gradually increased during this period from 250 to 400 km. A significant result of the reported analysis is the latitudinal (seasonal) variation observed in the semidiurnal and terdiurnal tides during solstice. It is found that this variation is responsible for the seasonal behavior of the midnight temperature maximum.
Herrero, F. A.↗
Aboveground Biomass Estimation in a Tidal Brackish Marsh Using Simulated Thematic Mapper Spectral Data
Spectral radiance data were collected from the ground and from a low altitude aircraft in an attempt to gain some insight into the potential utility of actual Thematic Mapper data for biomass estimation in wetland plant communities. No attempt was made to distinguish individual plant species within brackish marsh plant associations. Rather, it was decided to lump plant species with similar canopy morphologies and then estimate from spectral radiance data the biomass of the group. The rationale for such an approach is that plants with a similar morphology will produce a similar reflecting or absorping surface (i.e., canopy) for incoming electromagnetic radiation. Variations in observed reflectance from different plant communities with a similar canopy morphology are more likely to be a result of biomass differences than a result of differences in canopy architecture. If the hypothesis that plants with a similar morphology exhibit similar reflectance characteristics is true, then biomass can be estimated based on a model for the dominant plant morphology within a plant association and the need for species discrimination has effectively been eliminated.
Hardisky, M.↗
Patterns of Fracture and Tidal Stresses Due to Nonsynchronous Rotation: Implications for Fracturing on Europa
Global lineaments on Europa were interpreted as fractures in an icy crust. A variety of lineament types were identified, which appear to form a systematic pattern on the surface. For a synchronously rotating body, the patterns of fractures observed could be produced by a combination of stresses due to orbital recession, orbital eccentricity, and internal contraction. However, it was recently suggested that the forced eccentricity of Europa's orbit may result in nonsynchronous rotation. The hypothesis that fractures in a thin icy crust may have formed in response to stresses resulting from nonsynchronous rotation is studied.
Parmentier, E. M.↗
Tidal interactions between spherical galaxies
The impulse approximation and full N-body experiments are used to investigate the changes in mass and binding energy which result from gravitational encounters between spherical galaxies. Models with King (1966) and de Vaucouleurs (1948) surface density profiles, and radial, tangential, and isotropic velocity distributions. Results based on the impulse approximation depend on two collision parameters (the impact parameter and the ratio of the perturbing mass to the relative velocity at infinity); they agree well with N-body results. The asymptotic limit, valid for distant encounters, is found to approximate the correct results only for impact parameters larger than 10 effective radii. It is therefore of little use in most situations of interest. No simple 'linear' or 'quadratic' dependence of energy and mass loss on collision strength is found, but rather, a smooth intermediate behavior. Cross sections depend very little on the internal velocity structure of the galaxy, but quite strongly on the surface density profile in its outer parts. The reasons why these results disagree with the conclusions of previous workers are discussed.
Aguilar, L. A.↗
Inertio-gravity wave induced accelerations of mean flow having an imposed periodic component: Implications for tidal observations in the meteor region
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Walterscheid, R. L.↗
Tidally forced viscous heating in a partially molten Io
Models of Io that generate most of their heat by viscous dissipation in a partially molten (perhaps nearly liquid) asthenosphere are developed: a partially molten asthenosphere model and a partially molten interior model. An approximate thermal analysis is carried out, suggesting the possibility of a stable steady state. The models are consistent with observations of widely dispersed hot spots on the Io surface that radiate most of Io's heat loss. The hot spots imply that magmas carry most of the dissipative heating that is naturally accounted for in the models.
Ross, M. N.↗
Could Ariel have been heated by tidal friction?
For significant dissipation in Ariel, the past existence of an orbital resonance to force and maintain a substantial eccentricity in the orbit is hypothesized. The absolute maximum dissipation rate would be reduced both by the time necessary to establish the resonance in the first place and by a consequently larger minimum Q. The actual heating rate was much less than this maximum so even the existence of a 2/1 resonance may not be sufficient to account for Ariel's smooth sufrace.
Peale, S. J.↗
Compact X-ray binaries in hierarchical triples. I - Tidal angular momentum loss and GX 17 + 2
A general formalism is developed for the enhanced mass transfer rate expected in a close binary with a (distant) third companion star. Such a hierarchical triple model is applied to the X-ray burster and QPO source GX 17 + 2, consisting of an inner mass-transferring binary comprising a main-sequence secondary and an accreting neutron star, and a more distant companion. The model is shown to account for the anomalously high mass transfer rate for this burster and other systems with short orbital periods. A G star, which does not appear to be the binary companion of the neutron star but is consistent with the sub-arc second radio error box for GX 17 + 2, may be the triple companion. A predicted velocity curve for the triple companion is presented.
Bailyn, Charles D.↗
Tidal influences on vertical diffusion and diurnal variability of ozone in the mesosphere
Possible dynamical influences on the diurnal behavior of ozone are investigated. A time dependent one-dimensional photochemical model is developed for this purpose; all model calculations are made at 70 deg N during summer. It is shown that the vertical diffusion can vary as much as 1 order of magnitude within a day as a result of large changes in the zonal wind induced by atmospheric thermal tides. It is found that by introducing a dissipation time scale for turbulence produced by breaking gravity waves, the agreement with Poker Flat echo data is improved. Comparisons of results from photochemical model calculations, where the vertical diffusion is a function of height only, with those in which the vertical diffusion coefficient is changing in time show large differences in the diurnal behavior of ozone between 70 and 90 km. By including the dynamical effect, much better agreement with the Solar Mesosphere Explorers data is obtained. The results are, however, sensitive to the background zonally averaged wind. The influence of including time-varying vertical diffusion coefficient on the OH densities is also large, especially between 80 and 90 km. This suggests that dynamical effects are important in determining the diurnal behavior of the airglow emission from the Meinel bands.
Bjarnason, Gudmundur G.↗
Variations of the semi-diurnal tidal wind in the meteor region with periods of about 27 and 13.5 days
Daily values of sunspot number and solar radio emission at 10.7 cm wavelength show a well known strong modulation with a period of 27 days, the Sun's rotation period. Recent satellite measurements revealed the same modulation of the ultraviolet irradiance at wavelength below 300 nm. These UV variations can influence the thermal heating of the ozone layer by altering the chemical composition. Therefore, one can also expect a corresponding variation in the middle atmosphere of the semi-diurnal tide, which is thermally excited essentially by absorption of UV between 200 and 370 nm in the upper ozone layer. Results of radar meteor wind measurements were used to detect a presumable very weak 27 day modulation within the natural and artificial noise of the daily values of the semi-diurnal wind amplitude. The summer period was chosen because of its relatively steady conditions and the maximum amplitudes during the year. The results of this investigation are given and discussed.
Greisiger, K. M.↗