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Kato, S.

Publications and source records attributed to Kato, S..

At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Spectral analysis of temperature and Brunt-Vaisala frequency fluctuations observed by radiosondes

Recent studies have revealed that vertical wave number spectra of wind velocity and temperture fluctuations in the troposphere and the lower stratosphere are fairly well explained by a saturated gravity wave spectrum. But N(2) (N:Brunt-Vaisala (BV) frequency) spectra seem to be better for testing the scaling of the vertical wave number spectra in layers with different stratifications, beause its energy density is proportional only to the background value of N(2), while that for temperature depends on both the BV frequency and the potential temperature. From temperature profiles observed in June to August 1987 over the MU Observatory, Japan, by using a radiosonde with 30 m height resolution, N(2) spectra are determined in the 2 to 8.5 km (troposphere) and 18.5 to 25 km (lower stratosphere) ranges. Although individual spectra show fairly large day-by-day variability, the slope of the median of 34 spectra agrees reasonably with the theoretical value of -1 in the wave number range of 6 x 10(-4) similar to 3 x 10(-3) (c/m). The ratio of the spectral energy between these two height regions is about equal to the ratio of N(2), consistent with the prediction of saturated gravity wave theory.

Tsuda, T.↗
NASA NTRS1989

Observations of gravity waves in the mesosphere with the MU radar

Wind motions were observed at 60 to 90 km altitudes with the MU radar during daylight hours (0800 to 1600 LT) from 13 to 31 October 1986. Quasi-monochromatic gravity waves were evident on 16 of the 19 days of observations. They were characterized by typical vertical wavelength of 5 to 15 km and intrinsic periods centered at about 9 hours. The propagation direction of the gravity waves, determined by the gravity wave dispersion relation, was mostly equatorward. The vertical wave number spectra of the horizontal components of the mesoscale wind fluctuations are explained well by saturated gravity wave theory. The frequency spectrum of vertical wind component has a slope of + 1/3, while the oblique spectra have a slope of -5/3 up to 4 x 10(-3) (c/s); these agree fairly well with model gravity wave spectra. Doppler shift effects on the frequency spectra are recognized at higher frequencies. Upward flux was determined of horizontal momentum flux induced by waves with periods from 10 min to 8 hours, and westward and northward body forces of 5.1 and 4.0 m/s/day, were estimated respectively.

Tsuda, T.↗
NASA NTRS1986

Atmospheric Tides Middle Atmosphere Program (ATMAP): Report of the workshop, Kyoto, Japan, December 5-6, 1984

Experimentalists, data analysts, and theoreticians were brought together to study and interpret the results of four solstice campaigns conducted prior to the symposium. Emphasis was placed on campaigns III and V. Topics discussed included: review of the data and evaluation of the consistency with available theoretical models; interpretation of the data; recommendations on how the Atmospheric Tides Middle Atmosphere Program (ATMAP) results should reach the open literature such that the advancement of middle atmosphere science and the proprietary rights of the individual experimenters are best served; and recommendations concerning future campaigns and the future emphasis of ATMAP.

Forbes, J. M.↗
NASA NTRS1986

Measurements of precipitating atmosphere by the MU radar

Sensitive VHF Doppler radars have the capability to detect echoes from precipitation particles as well as refractive index irregularities. Researchers used the middle and upper (MU) atmosphere radar at Shigaraki, Japan for tropospheric observations of precipitating atmosphere. They detected precipitation motions simultaneously with the ambient air motion and showed the capabilities of the MU radar in investigating mesoscale structures of meteorological phenomena such as air precipitation motions within a cold frontal system. More recently, a direct method for deducing the drop size distribution of precipitation particles was developed using Doppler spectra of the MU radar. This method is free from errors inherent in conventional measurements using microwave Doppler spectra. Meteorological microwave radar data are also utilized for monitoring vertical and horizontal structures of precipitation.

Wakasugi, K.↗
NASA NTRS1986

Tropospheric turbulence parameters measured by using the MU radar

The spectral width of the Doppler radar echo has been used to estimate the atmospheric turbulence parameters because it is directly related to the kinetic energy contained in the turbulence. However, sufficient care must be taken in deriving the turbulence parameters since the measured spectral width can be easily affected by undesired factors such as beam broadening, shear broadening, and the temporal variation of the wind field. Here researchers examine these factors in the case of the MU radar observation of the upper troposphere, and present preliminary results.

Sato, T.↗
NASA NTRS1986

Monitoring of the MU radar antenna pattern by Satellite Ohzora (EXOS-C)

As the first attempt among MST (mesosphere stratosphere troposphere) type radars, the MU (middle and upper atmosphere) radar features an active phased array system. Unlike the conventional large VHF radars, in which output power of a large vacuum tube is distributed to individual antenna elements, each of 475 solid state power amplifier feeds each antenna element. This system configuration enables very fast beam steering as well as various flexible operations by dividing the antenna into independent subarrays, because phase shift and signal division/combination are performed at a low signal level using electronic devices under control of a computer network. The antenna beam can be switched within 10 microsec to any direction within the zenith angle of 30 deg. Since a precise phase alignment of each element is crucial to realize the excellent performance of this system, careful calibration of the output phase of each power amplifier and antenna element was carried out. Among various aircraft which may be used for this purpose artificial satellites have an advantage of being able to make a long term monitoring with the same system. An antenna pattern monitoring system for the MU radar was developed using the scientific satellite OHZORA (EXOS-C). A receiver named MUM (MU radar antenna Monitor) on board the satellite measures a CW signal of 100 to 400 watts transmitted from the MU radar. The principle of the measurement and results are discussed.

Sato, T.↗
NASA NTRS1985

Diurnal nonmigrating tides due to land-sea distribution

This paper is concerned with thermal excitation of diurnal nonmigrating tides by differential heating between land and sea. The nonmigrating tide is defined as a wave with a period corresponding to a subharmonic of a solar day. It is excited when heat sources of atmospheric tides have zonal asymmetries, and does not necessarily propagate westward with the Sun.

Tsuda, T.↗
NASA NTRS1985

Mesospheric winds observed by the Kyoto meteor radar

The Kyoto meteor radar has been operated almost continuously from May 1983. By using a large amount of radar data, seasonal variations of mean winds, planetary waves and atmospheric tides can be delinated. Seasonal and latitudinal variation of tidally corrected mean winds including Kyoto observations have been examined in comparison with the CIRA 1972 model. A power spectral density of the zonal wind field for 60 days of data is formed from an autocorrelation function with a maximum time lag of 30 days. A quasi-2-day oscillation was evident in the period from June to September, and seems to be repeated in 1983 and 1983. It had large amplitudes in June and July and became weak in August; then it was again amplified in September. In summer months, the period of the wave was indicated as 2.2 days, and it became shorter in September. At Kyoto (35 deg N), the diurnal tide is the main component of atmospheric tides. The monthly mean amplitude of the eastward component of diurnal tide is plotted for the period from May 1983 to September 1984. It was clearly amplified in summer months at around 92 to 96 km altitudes. This feature was repeated in two successive years except for the maximum amplitude which exceeded 40 m/sec and 30 m/sec in 1983 and 1984, respectively.

Tsuda, T.↗
NASA NTRS1985

The MU radar: Current status and first results

The MU (Middle and Upper Atmosphere) radar is a 46.5 MHz pulse modulated monostatic Doppler radar with an active phased array system. The nominal beam width is 3.6 deg, and the peak radiation power is 1 MW with maximum average power of 50 kW. A brief description of the system and the initial observational results are presented.

Kato, S.↗
NASA NTRS1985

Kyoto Meteor Radar Observation in November, 1981 and May, 1982

The Kyoto meteor radar a pulsed Doppler radar and operates at 31.57 MHz ith peak power of 10 kW. An interferometer is adopted for arrival angle measurement. Height resolution is approximately 1 to 3 km depending on both azimuth and elevation angles. Data is analyzed according to an algorithm approved by GROVES. All data in height range 84 to 104 km are separated into five layers, whose altitude width is 4 km. In each layer, least square fitting is performed for ten parameters, which are amplitudes of northward/eastward mean wind and sin/cos component of diurnal/semidiurnal tide. Reliable range for each parameter is also calculated.

Tsuda, T.↗
NASA NTRS1985

Mesospheric Winds at Jicamaraca, Peru (12 Deg S, 77 Deg SW), November 19-21, 1981

The altitude of mean zonal wind in the mesosphere during the whole daytime observations is given. Positive value refers to eastward. At around 70 km, wind corresponds to summer easterly, and changes to westerly with increasing altitude above about 77 km. These are fairly compatible with known features of zonal wind at this latitude. Contour plot shows local time variations of zonal wind with daytime mean subtracted and averaged over three days. Shaded area designated westward wind with contour level of 2 m/s. The daily variation is almost in phase with altitude in the 65 to 80 km region. Thus the semidiurnal tide with long vertical wavelength is inferred to exist. Above 80 km, phase tilt occurs which indicates the contribution of the propagating diurnal component. Here the combination of dc and 12-hr component is fitted to the data below 80 km. The altitude profiles of the amplitude and phase of this semidiurnal component are shown.

Aso, T.↗
NASA NTRS1985

Studies on organic semiconductors. 15: Effects of the substituents on the photoconductivities of substituted anthracenes

The photocurrents of the substituted anthracenes, 1,5-diacetylanthracene (2), 1-acetylanthracene (3), 9-acetylanthracene (4), 1,5-dichloroanthracene (5), 1,5-diethylanthracene (6), 1,5-dimethoxyanthracene (7), 9-cyanoanthracene (8), and anthracene (1) were measured by using their surface type cells in nitrogen. The compounds of (1), (5), (6), (7), and (8) showed the photocurrent spectra which corresponded to the absorption spectra of their evaporated films. In the cases of (2) and (3), however, the anomalous photocurrent appeared in the threshold region of their absorption spectra. The appearance of the anomalous photocurrent was characteristic of anthracenes having the acetyl group at 1- and/or 5-position. The magnitude of the photocurrents of the 1,5-disubstituted anthracenes was similar to that of (1). The photocurrents of the monosubstituted anthracenes were smaller than that of (1). Among the monosubstituted anthracenes, the compound (4) showed no photocurrent under the same conditions. Contrary to the results obtained in the cases of phenazines, the photoconductivities of the anthracene derivatives became better in air.

Sugimoto, A.↗
NASA NTRS1984

Excerpts from the paper: Research Status and Recommendation from the Alaska Workshop on Gravity Waves and Turbulence in the Middle Atmosphere, part 1.3A

Internal gravity waves are disturbances whose intrinsic frequencies k(c - u) are smaller than the Brunt-Vaisala frequency (N). Their importance arises because: they are the major components of the total flow and temperature variability fields of the mesosphere (i.e., shears and lapse rates) and hence constitute the likely sources of turbulence; and they are associated with fluxes of momentum that communicate stresses over large distances. For example, gravity waves exert a drag on the flow in the upper mesosphere. However, in order for gravity waves to exert a net drag on the atmosphere, they must be attenuated. There are two general types of processes that seek to attenuate gravity waves: dissipation and saturation. Dissipation is any process that is effective independent of the wave amplitude, while saturation occurs when certain wave amplitude conditions are met. Radiative damping is an example of dissipation, while convective overturning is an example of saturation. The two processes are not mutually exclusive.

Fritts, D. C.↗
NASA NTRS1984

The MU radar now partly in operation

The MU radar (middle- and upper-atmosphere radar) of RASC (Radio Atmospheric Science Center, Kyoto University) is now partly in operation, although the facility will be completed in 1985. The active array system of the radar makes it possible to steer the radar beam as fast as in each interpulse period. Various sophisticated experiments are expected to be performed by the system. A preliminary observation was successful to elucidate atmospheric motions during Typhoon No. 5 which approached the radar site in August, 1983.

Kato, S.↗
NASA NTRS1984

Internal inertia-gravity waves in the tropical lower stratosphere observed by the Arecibo radar

A quasi-periodic wind oscillation with an apparent 20-50 hour period was observed at between 16 and 20 km in every experiment conducted during three periods from 1979 to 1981 with the Arecibo UHF radar. The wave disappeared near 20 km, where the mean zonal flow had easterly shear with height. This phenomenon is discussed in terms of wave absorption at a critical level, and it is suggested that the wave had a westward horizontal phase speed of 10-20 m/sec. On the basis of a relationship from f-plane theory in which the Doppler-shifted wave frequency approaches the Coriolis frequency at the critical level, an intrinsic period and horizontal wavelength at the wave-generated height of 20-30 hours and about 2000 km, respectively, are inferred.

Maekawa, Y.↗
NASA NTRS1984

Research status and recommendations from the Alaska Workshop on Gravity Waves and Turbulence in the Middle Atmosphere, Fairbanks, Alaska, 18-22 July 1983

The Alaska Workshop on Gravity Waves and Turbulence in the Middle Atmosphere had as its purpose the assessment of current theoretical understanding and observational capabilities in this field, as well as to suggest what additional studies would further knowledge of these processes and their effects on the large scale circulation of the middle atmosphere. While it is judged that current understanding is primitive, theoretical and modelling studies are held to be able to contribute important quantitative data on gravity wave excitation, propagation, and dissipation mechanisms and effects. The combination of several observational systems is considered capable of expanding the present knowledge of gravity wave and turbulence morphology, parameters, and processes.

Fritts, D. C.↗
NASA NTRS1983

Outline of the Mu radar

A middle and upper atmospheric radar system is described. The antenna array consists of 25 groups each of which consists of 19 crossed-Yagis with three elements; each antenna has semiconductor transmitter and receiver, called a module, and each group of 19 antennas works as an independent small radar steering its radar beam under the control of a microcomputer. Thus, the total system consists of 25 small radars of this kind, enabling one to do various sophisticated operations with the system. The system is controlled by two other computers, one for radar controlling (HP9835A) and the other for data taking and on-line analysis (VAX11/750). The computer-controlled system is simple in operation for users and reliable in observation. Very quick beam steering (as quick as in a msec) is also possible because of electronic phase-changing of each module output under control of the microcomputer which is further controlled by the radar controller.

Kato, S.↗