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Some data from the Geos 3 satellite altimeter are examined in detail to demonstrate the techniques used for extracting wave height and skewness of the sea surface. The approach used in determining the dominant wavelength of the ocean waves is discussed. Improvements incorporated into the Seasat 1 altimeter as the result of experience with Geos 3 are described.
Methods for computing the atmospheric scale height to determine radio wave refraction were investigated for different atmospheres, and different angles of elevation. Tables of refractivity versus altitude are included. The equations used to compute the refraction corrections are given. It is concluded that very accurate corrections are determined with the assumption of an exponential atmosphere.
Rim height (Re) data have been gathered through shadow measurements for 30 fresh mercurian craters with diameters (D) between 2.6 and 39 km. Small mercurian craters (i.e., those less than about 16 km in diameter) have higher rims than do lunar craters of the same diameter; on the basis of Re/D measurements alone, however, mercurian craters larger than about 16 km appear to be indistinguishable from their lunar counterparts (those greater than about 21 km in diameter). Apparent crater depths (Ra, the crater depth measured from the initial target surface) derived from empirical data allude to a decrease in Ra/D with calculated modal impact velocity. This is consistent with the hypothesis that higher impact velocities place the effective depth of burst of the event closer to the surface, thus causing a shallower crater.
The height structure of hard X-ray bremsstrahlung emission in solar flares is computed for two different models of bremsstrahlung production: emission from a descending beam of nonthermal electrons, and thermal emission from a coronally confined hot plasma. It is shown how these models give rise to hard X-ray spatial distributions which are distinguishable by current instrumentation, and that, therefore, the models may be distinguished by such spatially resolved hard X-ray measurements.
Height and temperature analyses were constructed on a subset of the LFM grid using only Nimbus-6 satellite temperature profiles from approximately 1800 GMT 22 Feb. 1976. Several experiments were performed to evaluate various features of these satellite derived analyses. Fields derived from the bracketing LFM analyses provide the verification data. The results indicate that Nimbus-6 soundings were able to correctly position the major troughs and ridges, but underestimate gradients in the analyses due primarily to the soundings being too warm in the troughs. No advantage could be found in using a set of satellite soundings with a greater horizontal resolution than the DST soundings.
The annual and semiannual cycles of sea level pressure and surface temperature over the Northern Hemisphere are documented. The annual cycles in the geopotential height fields for several levels are also examined. It was found that the continental winter maxima in the sea level pressure field extended upward to near the 700 mb level. At 500 mb and above, however, they found that the annual cycle exhibits summertime maxima over both sea and land.
Mean monthly 700 mb height data are analyzed in relation to Pacific Ocean sea-surface temperatures (SST). Instead of treating the winter season as a unit, the data are analyzed separately for December, January and February; some results for November are also included. The associated pattern of the atmospheric circulation is most pronounced in January and February, especially over the Pacific. This indicates that time intervals of one month, and even shorter ones, are long enough to reveal the atmospheric relation to the sea-surface temperature. Moreover, an average of 700 mb data over the Pacific for January and February, would probably show a greater correlation with SST than the 'winter' average which commonly includes December. The differences between December and February observations are discussed with the aid of the theoretical model of Hoskins and Karoly (1981).
Twenty-eight Seasat altimeter profiles crossing the Mendocino Fracture Zone are used together with seafloor ages determined from magnetic lineations to estimate the change in oceanic geoid height with age, between ages of 15 and 135 m.y. An unbiased estimate of the overall geoid offset along each profile is determined from a least-squares fit of the along-track derivative of the geoid to the geoid slope predicted from a simple two-layer gravitational edge effect model. Uncertainties based upon the statistical properties of each profile are also determined. A geoid slope-age relation is constructed by normalizing the geoid offsets and uncertainties by the age offsets. The results are in agreement with geoid slope-age relations determined from symmetrically spreading ridges (Sandwell and Schubert, 1980). However, the fracture zone estimates have smaller uncertainties and show less scatter. A comparison of these results with the geoid slope-age prediction of the boundary layer cooling model shows that the thermal structure begins to deviate from this model at an early age (20-40 m.y.). A plate cooling model with a thickness of 125 km is most compatible with the geoid slope-age estimates, although significant deviations occur; these may indicate that the lithospheric thermal structure is not entirely age dependent.
Gridded National Meteorological Center data for 500 mb geopotential height and 300-500 mb and 500-700 mb thickness for the period 1951-1978 are subjected to linear trend analyses. The analyses are carried out for each calendar month. Significant geographical and seasonal distributions of cooling and warming patterns are found. An atmospheric cooling trend over the North Pacific during the winter months is seen in a region where oceanic cooling has also been observed, but planetary-wave adjustments rather than ocean-atmosphere feedback mechanisms appear to be dominant in the atmospheric cooling on climatic time scales. Consistently large temperature trends are also seen over the continent of Asia. Comparisons between thickness trends in the layer 300-500 mb and those in the layer 500-700 mb reveal pronounced patterns of stabilization and destabilization.
Measurement of ocean wave heights with the synthetic aperture radar can be accomplished with high spatial resolution by determining the variation of speckle intensity with the frequency and angle of illumination. A comparison of data obtained by the SEASAT SAR with surface truth measurements obtained during the GOASEX and the JASIN experiments demonstrates this concept.
Data are presented which show that the Schottky barrier height for gold on the ternary compound GaAs(1-x)P(x) follows the commonly assumed two-thirds of the band gap relationship. An explanation is given for the reason that previously published data did not exhibit this behavior.
The present investigation is concerned with the measurement of differences in the polarization of bright and dark areas on Venus. The differential polarization is matched by simple models in which the cloud height, amount of submicron haze above the clouds, and absorber amount in the clouds are varied. Physical and chemical models consistent with the findings are proposed. The differences in polarization between bright and dark ultraviolet features on Venus are found to have a straightforward interpretation in terms of known constituents of the atmosphere near the cloud tops. The observations of the polarization in four colors over 2 1/2 Venus years imply that the submicron haze and UV absorbers are anticorrelated, and that the clouds lie slightly (approximately 1 km) lower in the dark regions. These findings pose strong constraints on any model for the brightness variations in the UV.
A method of extracting sea height information from Synthetic Aperture Radar (SAR) complex data was studied. A fundamental SAR ocean imaging model for gravity waves showed that information about the long wave is present in the SAR complex data, especially its phase. Phase demodulation algorithm followed by linear regression and filtering was employed. Only the latter two steps incorporated a priori information that might be available. A relatively simplified simulation indicated that the finite bandwidth of the SAR system imposed the apparently most serious limitation. A preliminary application to SEASAT-SAR complex imagery was encouraging. Information about the long wave, if incorporated into a more sophisticated phase demodulation structure, i.e., at an earlier point in the algorithm, could conceivably mitigate this bandwidth limitation.
A total of 1575 radiosondes and the corresponding simulated brightness temperatures were used in an effort to derive a temperature retrieval based on the clusters of brightness temperatures. The 8 simulated channels, namely, 3 MSU and 5 IR of the TIROS-N satellite are used by the GLAS temperature retrieval method. The 3 MSU and 5 IR brightness temperatures were clustered into 17 cluster groups and a regression for the prediction of the tropopause height in mb was generated. The overall r.m.s. for the tropopause prediction is excellent, namely, around 16 mb for the summer and 23 mb for the winter. The correct cluster of brightness temperatures can be identified 98% of the time by the method of discriminatory classification if it is approximately a normal distribution or, in general, by the method of the nearest neighbor.
It has recently been recognized that spatially inhomogeneous clouds and rain can substantially affect the height precision obtainable from a spaceborne radar altimeter system. Through computer simulation, it has been found that typical levels of cloud and rain intensities and associated spatial variabilities may degrade altimeter precision at 13.5 GHz and, in particular, cause severe degradation at 35 GHz. This degradation in precision is a result of radar signature distortion caused by variable attenuation over the beam limited altimeter footprint. Because attenuation effects increase with frequency, imprecision caused by them will significantly impact on the frequency selection of future altimeters. In this paper the degradation of altimeter precision introduced by idealized cloud and rain configurations as well as for a realistic rain configuration as measured with a ground based radar is examined.
The thick target, hard solar X-ray source height structure is predicted for the case of a beam that is injected vertically downward, having a power law spectrum, being dominated by Coulomb collisional energy losses, and being structurally characterized by the ratio of hard X-ray flux from an upper part of the source to that from the entire source. These predictions are compared with the flux ratios at 150 and 350 keV which were observed by two spacecraft for five events in which the solar limb occults part of the source for one spacecraft. The energy dependence of the occultation ratio is found to be inconsistent with that predicted by the model, and it is concluded that noncollisional losses must be significant in beam dynamics.
Lorenz (1969) has considered the possibility that an atmospheric circulation pattern might recur, taking into account the definition of a pair of analogous flows or 'analogs'. The present investigation is concerned with a search of time series of Northern Hemisphere wintertime geopotential heights for possible analogs. Attention is given to data and analysis procedure, analog quality, and error growth rates. The obtained results imply that the found analogs are not a useful tool for forecasting the evolution of the midlatitude flow on time scales of several days. It is pointed out, however, that the negative results should not be extended to other applications of analog forecasting.
The theoretical description of the dynamics of a stellar convection zone is considered, taking into account one of the most basic issues by studying compressible convection extending over multiple scale heights. A revised version of a code reported by Graham (1975) is employed. Two-dimensional simulations show that nonlinear compressible convection possesses cellular structures with strong localized downward-directed plumes and broader upflows. The horizontal flows which close the circulation within the cell satisfy an approximate Bernoulli integral along a considerable portion of the horizontal trajectory. Attention is given to details regarding the numerical methods, the properties of the numerical solutions, the overall effects of compressibility on nonlinear convection, and a comparison with anelastic modal solutions.