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Peculiarities of the radar information about clouds are examined in comparison with visual data. An objective radar classification is presented and the relation of it to the meteorological classification is shown. The advisability of storage and summarization of the primary radar data for regime purposes is substantiated.
Twenty-one radar images of the surface of Venus obtained between 1972 and 1982 have been compared to follow the motion of 28 distinct features. The delays and Doppler shifts of these features with respect to the subradar points on the various days were used in a nonlinear least-squares parameter estimation algorithm to refine the period and pole orientation of Venus. The period is found to be -243.022 + or - 0.003 days; the right ascension and declination of the pole are: alpha = 272.816 + or - 0.14 deg; beta = 67.218 + or - 0.05 deg (B1950). These standard error estimates attempt to include effects of systematic errors.
Understanding of the natural variability of rainfall is essential in order to assess radar's ability to estimate rainfall characteristics such as rainfall rate, rainfall water content and drop size distribution parameters. The two most useful measurements of rainfall for this purpose derive from ground-based disdrometers and aircraft-borne drop size spectrometers. Accordingly, this paper examines a time series of disdrometer measurements obtained during a unique rainfall event which occurred in central Illinois on October 6, 1982. The measurements are used to predict the behavior of radar observables (reflectivity factor and differential reflectivity) for application to the estimation of rainfall parameters. The results support previous theoretical predictions (Seliga and Bringi, 1976) and experimental results (Seliga et al., 1979, 1981; Bringi et al., 1982; Hall et al., 1980; Goddard et al., 1982) based upon the differential reflectivity (ZDR) radar technique.
The production of high-resolution topographic maps derived from interferometric synthetic aperture radar observations of the Earth is reported. Topographic maps are typically determined from stereo-pair optical photographs. Vertical relief causes the same terrain to appear in a slightly different projection for differing look angles, and this shift in appearance is interpreted in terms of the height of the terrain. The radar interferometric approach is related to the stereo technique in that the terrain is viewed at two different angles; however, in this case, the angular separation of the antennas is extremely small, on the order of a milliradian or less, as compared to tens of degrees for the optical case. Thus, the geometrical distortion and subsequent rectification correction algorithms are much less severe in the reduction of interferometric data.
The production of high-resolution topographic maps derived from interferometric synthetic aperture radar observations of the earth is reported. Topographic maps are typically determined from stereo-pair optical photographs. Vertical relief causes the same terrain to appear in a slightly different projection for differing look angles, and this shift in appearance is interpreted in terms of the height of the terrain. The radar interferometric approach is related to the stereo technique in that the terrain is viewed at two different angles; however, in this case, the angular separation of the antennas is extremely small, on the order of a milliradian or less, as compared to tens of degrees for the optical case. Thus, the geometrical distortion and subsequent rectification correction algorithms are much less severe in the reduction of interferometric data.
The Arecibo 12.6 cm radar system was used to observe Titan in 1999, 2000 and 2001. The mean value of the radar albedo is 0.16 and the polarization ratio is 0.35. For some longitudes the echo has a specular component although most of the echo power is contained in a diffuse component. Additional information is contained in the original extended abstract.
This paper will present results of terrestrial delay-Doppler radar observations of the landing sites, predictions for the surface properties that will be encountered, and, after successful landings, correlation between the predicted and observed surface properties. The in-situ observations made by both missions serve as ground truth for the validation of the high resolution radar mapping results.
Doppler radar observations of the growth and evolution of precipitation (reflectivity factor) and associated mesoscale motions within the anvil region of an evolving mesoscale convective system (MCS) are presented. This MCS was observed during the Cooperative Huntsville Meteorological Experiment conducted over northern Alabama and central Tennessee during June and July, 1986. During the latter stages of the approximate eight-hour lifetime of this MCS, an extensive region of stratiform precipitation was observed. Attention is given to the initial appearance and subsequent evolution of precipitation within the stratiform region of the MCS, and the relation to the mesoscale flows that are seen within the system.
The oceanographic rationale is described for continuing to advance the state of the art in satellite radar altimetry, and the expected capabilities of a multibeam Earth Observing Radar are noted. At the end of this decade, there is the possibility that altimeters may be in orbit aboard the American TOPEX, the ESA ERS-1, and the French SPOT satellites at the same time. The TOPEX version will be the most precise altimeter yet built. Global ocean circulation will be measured by using TOPEX to monitor the elevation changes across the ocean basins due to oceanic currents. It will then be possible to monitor the 'mean' circulation patterns in the oceans. The multiple beams of EOR might be used to measure the curvature of the topographic surface. The use of curvature is especially beneficial because it is directly related to ocean circulation, which is a function only of the Laplacian of the topographic height field in a given area. With the EOR, that height field will be known and ocean circulation can be immediately computed.
Sondrestrom incoherent-scatter radar measurements of plasma drift in the auroral oval and the polar cap are used to examine the effect of the IMF B(y) component in the dusk, midnight, and dawn sectors. The individual radar observations are briefly reviewed, and the average convection patterns obtained by binning the drift data for the two orientations of the IMF B(y) component are shown. These patterns are compared to the various models of convection that have been proposed. None of the models seem to reproduce the observed convections well, although some features of the models are seen in the radar data.
Characterization of the rotation state and structure of near-Earth asteroids through radar observations using the Arecibo and Goldstone planetary radar systems shows the remarkable variety of these objects, and suggests variety of formation and modification mechanisms. Additional information is contained in the original extended abstract.
We report 8510-MHz (3,5-cm) radar observations of the Earth crossing asteroid (ECA) 6489 Golevka (1991 JX) obtained between June 3 and June 15, 1995, at Goldstone, the Very Large Array and the Evpatoria (Ukraine) and Kashima (Japan) radio antennas.
A 'blind' test involving interpretation of computer-enhanced like- and cross-polarized radar images is used to evaluate the surface roughness of Askja Caldera, a large volcanic complex in central Iceland. The 'blind' test differs from earlier analyses of radar observations in that computer-processes images and both qualitative and quantitative analyses are used. Attention is given to photogeologic examination and subsequent survey-type field observations, along with aerial photography during the field trip. The results indicate that the 'blind' test of radar interpretation of the Askja volcanic area can be considered suitable within the framework of limitations of radar data considered explicitly from the onset. The limitations of the radar techniques can be eliminated by using oblique-viewing conditions to remove geometric distortions and slope effects.
Terrestrial solid powdered rocks HF electrical properties measurements at 450 MHz and 35 GHz for lunar radar observation
The atmospheric parameters from the toposphere to the middle atmosphere during Typhoon Susan and tropical storms in May and June 1988 were observed by VHF radar in Taiwan. Time-dependent wind velocities with three-dimensional profiles are plotted by processing the backscattered echo power data and the Doppler spectral width of the signal returns from the VHF radar. The propagation characteristics of the gravity waves excited by the enhanced convection motions of the storms and the density perturbations caused by this gravity wave progagation are determined.
The results of airborne Doppler-lidar and ground-based Doppler radar observations of multicellular storms, marked by heavy rainfall, strong surface outflow, and a gust-front tornado, on June 30, 1981 are analyzed. The airborne lidar comprised a CO2-laser operating in the IR region, which was discharged once each second at 20 deg fore and aft, alternatively, of the normal to the aircraft's heading, and a quarter-wave plate for registering the returning frequency-shifted beams. Wind fields are plotted taking into account the advection effects. The lidar data set is noted for its self-consistency, though limited to a range of 5 km by the high moisture levels. Fair agreement was found between the lidar-derived and radar-derived average ground-based radial wind fields, with discrepancies on the order of 1.5 m/s.
Breaking gravitational waves in visually clear atmosphere from radar observations of horizontally braid-like atmospheric structures
We report 13-cm wavelength radar observations of the main-belt asteroids 7 Iris, 9 Metis, 12 Victoria, 216 Kleopatra, and 654 Zelinda obtained at Arecibo between 1980 and 1989. The echoes are highly polarized yet broadly distributed in Doppler frequency, indicating that our targets are smooth on decimeter scales but very rough on some scale(s) larger than about I m. The echo spectra are generally consistent with existing size, shape, and spin information based on radiometric, lightcurve, and occultation data. All of our targets possess distinctive radar signatures that reveal large- scale topography. Reflectivity spikes within narrow ranges of rotation phase suggest large flat regions on Iris, Metis, and Zelinda, while bimodal spectra imply nonconvex, possibly bifurcated shapes for Kleopatra and Victoria. Kleopatra has the highest radar albedo yet measured for a main-belt asteroid, indicating a high metal concentration and making Kleopatra the best main-belt candidate for a core remnant of a differentiated and subsequently disrupted parent body. Upon completion of the Arecibo telescope upgrade, there will be several opportunities per year to resolve main-belt asteroids with hundreds of delay-Doppler cells, which can be inverted to provide estimates of both three-dimensional shape and radar scattering properties.