鷹野 敏明

都市部での豪雨災害がクローズアップされ，都市型洪水に対する対策や短時間豪雨予測ナウキャストへの取り組みがなされている．通常の集中豪雨は組織化された積乱雲群によってもたらされ，激しい雨が数時間にわたって降り続くことにより，ごく狭い地域で数百ミリの雨量がもたらされ，防災上の観点から豪雨をもたらす積乱雲を出来る限り早く検知することは極めて大事である．気象学の観点からも対流雲の初期段階の挙動を様々な観測手段で捉えることは重要であることから，防衛大小林文明教授を中心とした研究チームによる総合観測がこれまでなされてきた（房総対流雲観測研究）．本発表では，房総対流雲観測研究チームによるこれまでの観測成果を俯瞰し，今後の展望について述べる．

Aerosols and clouds play important roles in the Arctic climate. Conversely, aerosol emissions and cloud formation are affected by changes in the Arctic climate. This paper reviews studies of aerosols and clouds performed during the Arctic Challenge for Sustainability (ArCS) project carried out by the National Institute of Polar Research (NIPR) in Japan and collaborating institutions. The ArCS project included intensive studies of black carbon aerosols (BC). We installed Continuous Soot Monitoring System (COSMOS) instruments to measure atmospheric BC at four locations in the Arctic, establishing the Arctic BC COSMOS Measurement Network (ABCMnet). We also measured BC concentrations in snowpack in extensive areas of the Arctic and showed that previous studies have greatly overestimated BC in snowpack. We developed and improved new aerosol models that achieved better agreements with measurements of BC in the Arctic atmosphere, snowpack, and falling snow. We made new estimates of radiative forcing of BC in the Arctic atmosphere and snow/ice surfaces that lower their albedo. In addition to these researches on BC, we made accurate measurements of ice nucleating particles (INPs) at Ny-?lesund, Svalbard, showing that their concentrations increased in summer as a result of dust particle emissions from glacial outwash sediments. This high ice nucleating ability was likely due to the presence of organic substances mixed with the dust particles. We also made continuous cloud radar measurements and the first continuous in-situ measurements of cloud microphysical properties in the Arctic at Ny-?lesund. Results from these cloud measurements and their relationship with aerosols are described.

©2018. American Geophysical Union. All Rights Reserved. Free tropospheric aerosols over the high Arctic were observed by lidar for about 4 years from March 2014 at Ny-Ålesund (78.9°N, 11.9°E). Vertical profiles of aerosol backscattering coefficients at two wavelengths, 532 and 1,064 nm, and depolarization ratio at one wavelength, 532 nm, are derived from these observations. The aerosol backscattering coefficient, the particle depolarization ratio, and the color ratio (the ratio of the backscattering coefficients at the two wavelengths) are roughly proportional to mass concentration, nonsphericity, and size of the aerosol particles, respectively. The aerosol backscattering coefficients indicate that monthly averaged concentration of aerosols was largest in the lowest free troposphere at about 1 km in altitude and was an order of magnitude less at an about 10 km in altitude and that the concentration of aerosols was highest from late spring to summer and lowest from late summer to fall. The depolarization ratio was less than a few percent in the troposphere during the four observed years. The depolarization ratio and the color ratio were greatest from winter to spring and smallest from summer to fall. The maxima in the monthly averaged nonsphericity and size precede the maxima in the monthly averaged concentration by a few months, indicating a seasonal change in the morphology or the characteristics of the aerosol particles. The small particle depolarization ratio of less than a few percent is consistent with previous findings that Arctic free tropospheric aerosol particles in spring are composed of a mixture of liquid phase sulfate and soot particles.

Using 630 nm airglow data observed by an airglow imager on the International Space Station (ISS), the occurrence of equatorial plasma bubbles (EPBs) is studied. In order to examine the physical mechanisms in the boundary region between the Earth and the outer space, an ionosphere, mesosphere, upper atmosphere, and plasmasphere mapping (IMAP) mission had been conducted onboard the ISS since October 2012. The visible light and infrared spectrum imager (VISI) is utilized in the ISS-IMAP mission for nadir-looking observation of the earth's atmospheric airglow. In this study, we automatically select EPBs according to the criterion for extracting the tilted dark lines from VISI data. Using the selected events, the dependence of the occurrence rate of EPBs is examined. There is no other report of the occurrence rate of EPBs using downward-looking visible airglow data (630 nm). In this result, the occurrence rate is high at all longitudes in the equinoctial seasons. In the solstice seasons, in contrast, the occurrence rate is very small especially in the Pacific and American sectors. This result is basically consistent with previous studies, e.g., those determined by plasma density data on DMSP satellites.During the June solstice in 2013, EPBs were observed in association with geomagnetic storms that occurred due to a southward turning of the IMF Bz. Using these events, we examined the storm-time features of the occurrence of EPBs in the Pacific-American sectors during the June solstice. In these sectors, where the occurrence rate of EPBs is very small during solstice seasons, some EPBs were observed in the peak and recovery phases of the storms. This result shows that the prompt penetration of electric fields causes the development of EPBs, in the data we analyzed, the geomagnetic storms did not inhibit the generation of EPB in the Pacific-American sectors.

© The Authors, published by EDP Sciences, 2018. In this study, we focus on the retrieval of liquid and ice-phase cloud microphysics from spaceborne and ground-based lidar-cloud radar synergy. As an application of the cloud retrieval algorithm developed for the EarthCARE satellite mission (JAXA-ESA) [1], the derived statistics of cloud microphysical properties in high latitudes and their relation to the Arctic climate are investigated.

© SGEM2018. Observation of clouds with radars in millimeter wave range is one of the most powerful remote sensing methods to derive information on interior of clouds. We have developed and are operating a cloud profiling FMCW (Frequency Modulated Continuous Wave) Doppler radar named FALCON-I (FMCW Radar for Cloud Observations) at 95GHz. It is a bistatic antenna system, which is usually used for FMCW radar, and consists of two 1m-diameter antennas with high spatial resolution of 0.18 degree FWHM. A High range resolution of 15m is realized with the FMCW type radar, which is about 10 times higher than that of normal pulse type radar. FALCON-I has enough sensitivities for faint clouds at high altitude and has high resolution in Doppler measurements. We are developing a monostatic antenna system of FMCW Doppler radar. A monostatic antenna system does not have any beam discrepancies between the transmitting and the receiving antenna. One of the most difficult points for a monostatic antenna system is contamination of transmitting power into the receiving section. In order to reduce the contamination, we introduce a cancel system of power in the frontend of the radar. The cancel system consists of a power spritter, an attenuator, and a phase shifter in W-band and produces an antiphase signal against to the contamination power. By using the cancel system, we can reduce the contamination power by-40 dB and can observe clouds and rains.

We have developed and are operating a cloud profiling FMCW (Frequency Modulated Continuous Wave) Doppler radar in millimeter wave range at 95GHz. It consists of two 1m-diameter antennas with high spatial resolution of 0.18 degree FWHM. A High range resolution of 15m is realized with the FMCW type radar, which is about 10 times higher than that of normal pulse type radar. The radar has enough sensitivities for faint clouds at high altitude and has high resolution in Doppler measurements. Using the millimeter wave radar we observe various clouds, and especially clouds with rapid changing phenomena such as heavy precipitations, violent winds, and so on. We can make rapid scanning observations of clouds with the radar. These result with scanning imaging reveal some important information of clouds and precipitations: dynamic motions of cloud interior, production of large droplets of precipitation in high altitude up to 10 km in cumulonimbus, sudden acceleration of precipitation after falling from bottom of clouds, and so on. These facts show that the facility is quite useful for environmental monitoring on clouds and precipitations.

W-band 95GHz Doppler radar named FALCON-I was developed and operated for cloud observations. High spacial and high velocity resolution are achieved with low transmitting power of millimeter wave. FALCON-I can observe not only clouds and precipitations but also flying small objects such as birds, insects, seeds of plants, and volcanic ashes in the atmosphere.

© 2017 URSI. Many studies have reported that ionospheric disturbances occur after big earthquakes. One of the causes of these coseismic ionospheric disturbances (CIDs) is the infrasound wave excited by Rayleigh wave propagated on the ground from the epicenter. The infrasound wave propagates upward and produces CIDs. In this study, using HF Doppler sounding system (HFD), CIDs at the different altitudes associated with the foreshock of Tohoku Earthquake were examined.

We developed a multiple-field-of-view multiple-scattering polarization lidar (MFMSPL) to study the microphysics of optically thick clouds. Designed to measure enhanced backscattering and depolarization ratio comparable to space-borne lidar, the system consists of four sets of parallel and perpendicular channels mounted with different zenith angles. Depolarization ratios from water clouds were large as observed by MFMSPL compared to those observed by conventional lidar. Cloud top heights and depolarization ratios tended to be larger for outer MFMSPL channels than for vertically pointing channels. Colocated 95 GHz cloud radar and MFMSPL observations showed reasonable agreement at the observed cloud top height. (C) 2016 Optical Society of America

© 2016 The Institute of Electrical Engineers of Japan. In order to examine the direction of arrival of VHF radio waves dependent on the natural phenomena, the interferometers have been installed at Katsuyama, Chiba Prefecture and Numata. Gunma Prefecture. In this study, the radio wave it the frequency of 77.1 MHz transmitted from Tokyo Tower (assigned to FM broadcasting of the Open University of Japan) is observed. The interferometers consist of four Yagi antennas and estimate the directions of arrivals of the radio wave. The observational results show that the directions of the wave are affected by the disturbances in the ionosphere and the atmosphere. In this paper, the system of the interferometers is described and the examples of the observation results are presented.

Aims. To study the abundance and temperature of ammonia in the center of a nearby galaxy M 51 and to compare them with those in other nearby galaxies, we observed its (J, K) = (1, 1), (2, 2), (3, 3), and (4, 4) inversion transitions at the wavelength of 1.3 cm.Methods. The observations were carried out with the Effelsberg 100-m radio telescope.Results. The (1, 1), (2, 2), and (3, 3) transitions are clearly detected, but the (4, 4) transition is barely detected. The rotational temperature obtained from the (1, 1) and (2, 2) transitions of para-ammonia is 25 +/- 2 K, which is similar to those of M 82 and the Large Magellanic Cloud (N 159 W), but significantly lower than those of IC 342 and NGC 1068 among the nearby galaxies. The column density of ammonia is (8.1 +/- 2.4) x 10(13) cm(-2), and the abundance relative to H-2 is similar to 4.5 x 10(-9). The abundance in M 51 is about a factor of 5 lower than those of NGC 253 and IC 342, but about one order of magnitude higher than those of M 82 and the Large Magellanic Cloud. The addition of the data of M 51 further supports the exceptionally low abundances of ammonia reported previously in these two galaxies. For understanding the abundance of ammonia in M 51 and other nearby galaxies, their temperatures were compared. As a result, we found that the galaxies with low temperature tend to have low abundance of ammonia. In addition, the photodissociation rate of ammonia was compared to those of related molecules detected in the nearby galaxies to discuss the effect of photodissociation. We found that the low abundance of ammonia in some galaxies cannot be explained only by the effect of photodissociation.

Earthquake-related anomalous electromagnetic phenomena have been reported in various frequency ranges over the past few decades. Investigation of the anomalous propagation of VHF transmitter waves is a promising approach to short-term prediction and crustal activity monitoring. Anomalous propagation is believed to be generated by disturbances of the atmosphere above the epicenter or along the propagation path prior to large earthquakes. Consequently, over-the-horizon propagation has been received. A recent study shows that the appearance of anomalies was significantly enhanced within 5 days of earthquakes with M =4.8. However, there is no information on the scattering location, that is, on the direction of wave arrival. Therefore, a simple interferometer system for VHF radio waves to identify the space-time position of earthquake-related atmospheric disturbances has been developed and installed at Chiba University. This paper describes the newly developed interferometer system and presents the results of fundamental tests to evaluate the performance of the new interferometer at Chiba. Data on over-the-horizon propagation of VHF radio waves obtained from 1-year continuous measurement at Chiba are described. These are possible radio duct propagations and possible earthquake-related anomalous propagations. (c) 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 183(1): 1624, 2013; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22303

A Cloud profiling FMCW (Frequency Modulated Continuous Wave) Doppler radar named FALCON-I at 95GHz is developed at Chiba University. It consists of two 1m-diameter antennas and has high spatial resolution of 0.18 degree FWHM. A High range resolution of 15m is realized with the FMCW type radar, which is about 10 times higher than that of normal pulse type radars. Output power of FALCON-I is as small as 0.5W, and, therefore, it is realized with solid state components without any tubes. Although its small output power, FALCON-I has good sensitivities of -32 dBZ at the distance of 5 km to observe thin clouds at high altitude and has high resolution in Doppler measurements. Using FALCON-I, we observed clouds at Chiba, Cape Hedo, Okinawa, and on cruises on MIRAI, Japanese scientific research vessel, on various oceans in the last several years. These results will be useful to investigate characteristics of clouds in various places and oceans in order to make global model of atmosphere. © 2012 IEEE.

Simultaneous observations of cumulonimbi using the 95-GHz FM-CW cloud radar, the X-band radar, and photogrammetry were carried out during the summer of 2010 in the Kanto region, Japan. An isolated cumulonimbus developed above the cloud radar site after 16: 00 Japan Standard Time (JST) on 24 July 2010. A continuous generation of turrets was observed and a total of four turrets formed. The growth rates of the turrets were quite different. The first radar echo of the X-band radar was detected at 3 km above ground level (AGL), three minutes after turret 1 reached its maximum height. Turret 2, generated above the cloud radar, reached 10 km AGL and had a growth rate of 8 m s(-1). The cloud radar detected echoes approximately two minutes after the generation of turret 2. The intermittent echo pattern observed by the cloud radar denotes fine structures in the cumulonimbus.

We developed a cloud profiling radar called FALCON-1, transmitting a frequency-modulated continuous wave (FM-CW) at 95 GHz for high sensitivity and high-spatial-resolution ground-based observations. A millimeter wave at 95 GHz is used to realize high sensitivity to small cloud particles. An FM-CW-type radar realizes similar sensitivity with much smaller output power to a pulse-type radar. Two I-m-diameter parabolic antennas separated 1.4 in from each other are used for transmitting and receiving the wave. At present the direction of the antennas is fixed at the zenith. The radar can observe clouds up to 20 km in height with a resolution of 9 m. The beam size of the antenna is only 0.2 degrees of arc, which corresponds to 15 in at a range of 5 km. Observation results showed that a sensitivity of -34 dBZ was achieved at a range of 5 km, with good spatial resolution. (C) 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(3): 42-49, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10170

Cloud-top height (CTH) variability in the tropical tropopause layer (TTL) in association with equatorial Kelvin waves is investigated using a new CTH dataset based on MTSAT-1R geostationary satellite measurements with a statistical look-up table constructed based on CloudSat measurements. We focus on a case in the tropical Indian Ocean during October-December 2006, when shipboard radiosonde, TTL water vapor, and 95-GHz cloud radar measurements were taken during the Mirai Indian Ocean cruise for the Study of the MJO-convection Onset (MISMO) field campaign. At 10-15 km, the satellite-based CTH data agree well with the radar echo top heights from shipboard radar reflectivity data. During the MISMO campaign, cloud frequency was suppressed in the warm phase of equatorial Kelvin waves propagating in the TTL. The suppressed-cloud region moves eastward to the western Pacific together with Kelvin waves. We found that changes in CTH occurrence frequency over the vessel in association with Kelvin waves are much greater than those associated with the diurnal cycle. It is expected that the phase of equatorial Kelvin waves is important for the intraseasonal variabilities of both the radiative budget of the tropical atmosphere and water vapor transport in the TTL.

It is possible to retrieve vertical profiles of cloud microphysical properties, using radar reflectivity factor observed by CPR (Cloud Profiling Radar), which leads to better understanding of cloud radiative forcing. In this study, vertical profiles of cloud microphysical properties (e.g., effective radius, liquid water content, cloud optical thickness, etc,) retrieved from the ground-based FMCW CPR FALCON-I are estimated to evaluate sensitivity and accuracy of FALCON-I at the Hedo observation in 2008.

The effect of increased aerosol concentrations on the low-level, non-precipitating, ice-free stratus clouds is examined using a suite of surface-based remote sensing systems. Cloud droplet effective radius and liquid water path are retrieved using cloud radar and microwave radiometer. Collocated measurements of aerosol scattering coefficient, size distribution and cloud condensation nuclei (CCN) concentrations were used to examine the response of cloud droplet size and optical thickness to increased CCN proxies. During the episodic events of increase in aerosol accumulation-mode volume distribution, the decrease in droplet size and increase in cloud optical thickness is observed. The indirect effect estimates are made for both droplet effective radius and cloud optical thickness for different liquid water path ranges and they range 0.02-0.18 and 0.005-0.154, respectively. Data are also categorized into thin and thick clouds based on cloud geometric thickness (Δz) and estimates show IE values are relatively higher for thicker clouds. Copyright 2009 by the American Geophysical Union.

We have developed a low-power and high-sensitivity cloud profiling radar, named FALCON-I, transmitting frequency modulated continuous wave (FM-CW) at 95 GHz for ground-based observations. Millimeter wave at 95 GHz is used to realize much higher sensitivity than lower frequencies to small cloud particles. An FM-CW type radar realizes similar sensitivity with much smaller output power to a pulse type radar. Two 1m-diameter parabolic antennas separated by 1.4m each other are used for transmitting and receiving the wave. The direction of the antennas is fixed at the zenith at this moment. The radar can observe clouds up to 20 kin in height with the range resolution of 15 m and the angular resolution of 0.2 degree. Simultaneous observations of FALCON-I and a pulse type radar, SPIDER, show good performance of FALCON-I. Sensitivity of FALCON-I is -32 dBZ in radar reflectivity factor at 5 km, which is only MB worse than that of SPIDER although its output power is 1/3000 to SPIDER. Ranging resolution of 15m is realized for FALCON-I, which is 1/10 of that of SPIDER. Using developed FALCON-I, we observed clouds in various regions and oceans in the last three years.

We have developed a low-power and high-sensitivity cloud profiling radar, named FALCON-I, transmitting frequency modulated continuous wave (FM-CW) at 95 GHz for ground-based observations. Millimeter wave at 95 GHz is used to realize much higher sensitivity than lower frequencies to small cloud particles. An FM-CW type radar realizes similar sensitivity with much smaller output power to a pulse type radar. Two 1m-diameter parabolic antennas separated by 1.4m each other are used for transmitting and receiving the wave. The direction of the antennas is fixed at the zenith at this moment. The radar can observe clouds up to 20 kin in height with the range resolution of 15 in and the angular resolution of 0.2 degree. Simultaneous observations of FALCON-I and a pulse type radar, SPIDER show good performance of FALCON-I. Sensitivity of FALCON-I is -32 dBZ in radar reflectivity factor at 5 km, which is only 3dB worse than that of SPIDER although its output power is 1/3000 to SPIDER. Ranging resolution of 15m is realized for FALCON-I, which is 1/10 of that of SPIDER. Using developed FALCON-I, we observed clouds in various regions and oceans in the last three years.

Studying the vertical structure of cloud is essential to make better atmospheric modelings for simulations of the global warming. Cloud observation requires very high sensitivity for radar. Although pulse radar is the mainstream of MMCR (Millimeter Wave Cloud Radar), FMCW radar has some advantages. FMCW signal has high spatial and time resolution, and enables high durability and cost-performance because all of the components are designed with semiconductor devices. The bistatic FMCW Millimeter Wave Cloud Radar created by Engineering of Radio Physics Laboratory at Graduate School of Chiba University is designed to have 20km detection range of reflectivity and doppler velocity. Using this radar, we observed on a research vessel "MIRAI" in large region on the Pacific Ocean and the Arctic Ocean. These long-term observations and other observatin on the ground show good sensitivity of the radar and suggests the possibility of FMCW cloud radar. Copyright 2006 IEICE.

We have observed broadband VHF radio waves to investigate the propagation of distant TV broadcast waves. From the end of January to the middle of February, 2006, in the evening various radio waves at several frequency in 47.5-76.0 MHz have been often received with high intensity at Tateyama observatory(34°59'N, 139°54'E). Many of them are considered to come from China because their frequencies are used for TV broadcasting waves in China. As the value of foEs is high in occurring this event, we examine relationship between this event and Sporadic E layer (Es) Copyright 2006 IEICE.

The latest findings in the field of electromagnetic phenomena, which is based on the electromagnetic theory and analysis are described. The research showed evidence of precursor signature of earthquakes, including electromagnetic emissions in a wide frequency range from DC/ULF to VHF and seismo-atmospheric and ionospheric perturbations as detected by pre-existing transmitter signals. ULF emissions are found to take place prior to a large earthquake and there have been proposed a few generation mechanisms including microfracturing, electro-kinetic effect. The ionosphere is found to be very sensitive to a large earthquake since the subionospheric VLF propagation has yielded convincing evidence of ionospheric perturbations.

We developed a low-power and high-sensitivity cloud profiling radar transmitting frequency modulated continuous wave (FM-CW) at 95 GHz for ground-based observations. Using the developed millimeter-wave radar, we observed clouds on cruises on "Mirai", a Japanese scientific research vessel, in the Arctic Ocean and the southwest of the Pacific Ocean in 2004, and northern half of the Pacific Ocean in 2005. The radar provided good and sensitive data in these long-term observations. Observations of Clouds in such large area are useful for investigating global characteristics of clouds: e.g., latitude dependence of cloud structures, height change of melting layer, distribution of cloud water contents, and so on. Copyright 2006 IEICE.

The propagation of VHF radio waves affected by field-aligned irregularities within equatorial plasma bubbles is examined. Continuous observation of VHF radio waves at Tateyama, Japan, shows that broadcast radio waves transmitted from Southeast Asia propagate to Japan. Using a ray-tracing calculation combined with a model of scattering by field-aligned irregularities, we determined scatter points suitable for the reception of these radio waves. The results of the calculation show that radio waves transmitted from the Philippines can propagate to Japan owing to field-aligned irregularities within equatorial plasma bubbles located west of Japan. Comparing with all-sky imager data observed at Sata, Japan, we found that the radio waves are received at Tateyama when the plasma bubbles are observed at Sala. The results of this study show that the reception of these radio waves is closely correlated with the equatorial plasma bubbles. Copyright 2005 by the American Geophysical Union.

We observed ammonia (J, K) = (1, 1), (2, 2), (3, 3), and (4, 4) transitions at a wavelength of 1.3 cm toward a prototypical ultraluminous infrared galaxy, Arp 220, with the Nobeyama 45-m radio telescope. We detected extremely wide absorption lines at the (1, 1) and (3, 3) transitions. The maximum total velocity width was ∼ 1800 kms-1. Such wide molecular absorption lines were detected for the first time in galaxies. The absorption lines are formed by ammonia only in front of the central compact continuum emission (∼ 1″ = 370 pc). The present results clearly indicate the existence of extremely high-velocity motion in the central compact region of Arp 220. A possible origin of such motion is rapidly rotating gas, suggesting the existence of an active galactic nucleus, or outflowing or inflowing gas. © 2005. Astronomical Society of Japan.

We developed a low-power and high-sensitivity cloud profiling radar transmitting frequency modulated continuous wave (FM-CW) at 95 GHz for ground-based observations. Millimeter wave at 95 GHz is used to realize much higher sensitivity than lower frequencies to small cloud particles. An FM-CW type radar realizes similar sensitivity with much smaller output power to a pulse type radar. Two 1m-diameter parabolic antennas separated by 1.4m each other are used for transmitting and receiving the wave. The direction of the antennas is fixed at the zenith. The radar is designed to observe clouds between 0.3 and 20 km in height with a resolution of 15 m. Using the developed millimeter-wave FM-CW radar at 95 GHz, we observed clouds in a campaign observation in Amami Island in March 2003, and on a sail on Mirai, a Japanese scientific research vessel, in September 2004 to January 2005 in the Arctic Ocean and the southwest of the Pacific Ocean. The radar provided good and sensitive data in these long-term observations.

In order to explain the propagation of VHF radio waves for TV broadcasting transmitted from Southeast Asia associated with equatorial plasma bubbles, we have examined ray paths of the radio waves scattered by field-aligned irregularities in equatorial plasma bubbles. In determining the ray paths of the radio waves, a ray tracing calculation combined with a model of the scattering by field-aligned irregularities is used. It is found that VHF radio waves transmitted from Philippines can propagate to Japan due to scattering by field-aligned irregularities located above the East China Sea. © 2004, The Institute of Electrical Engineers of Japan. All rights reserved.

We developed a cloud profiling radar transmitting frequency-modulated continuous wave (FM-CW) at 95 GHz for ground-based observations. Millimeter wave at 95 GHz is used to realize high sensitivity to small cloud particles. An FM-CW type radar would realize similar sensitivity with much smaller output power to a pulse type radar. Two 1m-diameter parabolic antennas separated by 1.4m each other are used for transmitting and receiving the wave. The direction of the antennas is fixed at the zenith. The radar is designed to observe clouds between 0.3 and 15 km in height with a resolution of 15 m. Using the facility, test observations and long term campaign observations have been done. Results of observations show that the system is sensitive and stable enough to observe various clouds.

Broadband spectra in VHF band are regularly observed in Chiba, Japan, to investigate anomaly of propagation of broadcasting waves from distant Asian broadcasting stations. TV broadcasting waves from China, Philippines, Thai, Malaysia, and so on can sometimes propagate and there are three types of propagations. Seasonal and daily variations of received broadcasting waves were investigated through two-year observations. We are also performing a simulation with the ray tracing method. In results, these propagations are caused by refraction in F2 layer, by scattering on plasma bubbles, and by reflection in Es layer. © 2004 IEEE.

We developed a low-power and high-sensitivity cloud profiling radar transmitting frequency- modulated continuous wave (FM-CW) at 95 GHz for ground-based observations. Millimeter wave at 95 GHz is used to realize high sensitivity to small cloud particles. An FM-CW type radar realizes similar sensitivity with much smaller output power to a pulse type radar. Two Im-diameter parabolic antennas separated by 1.4m each other are used for transmitting and receiving the wave. The direction of the antennas is fixed at the zenith. The radar is designed to observe clouds between 0,3 and 15 km in height with a resolution of 15 m. Using the facility, test observations and long term campaign observations have been done. Results of observations show that the system can observe clouds of -30dBZ at the distance around 5km, which is sensitive enough to observe various kinds of clouds. © 2004 IEEE.

Broadband spectra in the VHF band are observed to investigate any anomaly of propagation of distant TV broadcasting waves, we concluded that Malaysia and Philippines TV waves at lower frequencies are refracted by the F2 layer in the daytime ionosphere. We found that TV waves from Malaysia at 48.25 MHz were sometimes heavily attenuated for a few hours when earthquakes occur in the Okinawa area. We propose a hypothesis that the attenuation is caused by some disturbance in the ionospheric E layer above epicenters. Results of computer simulations suggest that a 10% enhancement or depletion of electron densities can explain the observed attenuation. ©2004 IEEE.

© 2003 SPIE. A cloud profiling radar transmitting frequency-modulated continuous wave (FM-CW) at 95 GHz is developed for ground-based observations. Millimeter wave at 95 GHz is used to realize high sensitivity to small cloud particles. Two 1m-diameter parabolic antennas separated by 1.4m each other are used for transmitting and receiving the wave. The direction of the antennas is fixed at the zenith. The radar is designed to observe clouds between 0.3 and 15 km in height with a resolution of 15 m. The system was integrated and sensitivities and stabilities have been measured. Results of test measurements of clouds show that the system is sensitive and stable enough to observe various clouds.

We have designed and developed polarizers (or polarization converter, λ/4 phase shifter) using solid anisotropic medium of sapphire for millimeter and submillimeter waverange. Prototype polarizers made of sapphire was fabricated for 90 GHz band. The diameter and the thickness of the polarizers are 50mm and 2.8mm, respectively. Characteristics of this prototype polarizer have been measured. A simple and preliminary estimation of the insertion loss and the quantity of the phase shift at present is 0.4dB and 70°, respectively. These results show that poplarizers using solid anisotropic medium of sapphire are applicable for millimeter and submillimeter waverange.

We have analyzed three flare events with subsecond structures in hard X-rays (CGRO/ BATSE) and 17 GHz data (Nobeyama radioheliograph). It was shown that microwave subsecond brightenings (SSB) were generated by directly precipitating electrons with energy of 100-200 keV from tiny regions close to footpoints. In two events, when high correlation between microwaves and X-rays was observed, the SSB can be interpreted in terms of gyrosynchrotron emission. Plasma emission seems to be a more credible explanation of the spontaneous pulses in the event when poor correlation with X-rays was observed.

The ammonia (J,K) = (1,1), (2,2), (3,3), and (4,4) transitions in the 23.7-24.1 GHz region were searched in a nearby galaxy, Maffei 2, to study the relation between the molecular abundances and the physical conditions in galaxies. The (1,1), (2,2), and (3,3) emission lines were clearly detected. The obtained rotational temperatures and ortho-to-para abundance ratios are about 30 K and about 2.6, respectively. The abundance of NH3 relative to H2 in Maffei 2 was found to be the largest among galaxies where NH3 has already been detected, and the abundance in Maffei 2 is more than an order of magnitude larger than the already reported upper limit in M 82. Hence, we further confirmed the systematically peculiar molecular abundance regarding the formation mechanisms of molecules already reported in M 82.

Radio images and spectra of an eruptive prominence were obtained from simultaneous multifrequency observations at 36 GHz, 89 GHz, and 110 GHz on May 28, 1991 with the 45-m radio telescope at Nobeyama Radio Observatory (NRO), the National Astronomical Observatory, Japan (NAOJ). The radio spectra indicated that the optical depth is rather thick at 36 GHz whereas it is thin at 89 and 110 GHz. The H α data, taken at Norikura Solar Observatory, NAOJ, suggest that the eruption of an active region filament was triggered by an H α flare. The shape and position of the radio prominence generally coincided with those of H α images. The radio emission is explained with an isothermal cool thread model. A lower limit for the electron temperature of the cool threads is estimated to be 6100 K. The range of the surface filling factors of the cool threads is 0.3-1.0 after the Hα flare, and 0.2-0.5 in the descending phase of the eruptive prominence. The column emission measure and the electron number density are estimated to be of the order of 1028 cm-5 and 1010 cm-3, respectively. The physical parameters of a quiescent prominence are also estimated from the observations. The filling factors of the eruptive prominence are smaller than those of the quiescent prominence, whereas the emission measures and the electron densities are similar. These facts imply that each cool thread of the prominence did not expand after the eruption, while the total volume of the prominence increased. © 1995 Kluwer Academic Publishers.

A new 17-GHz radio interferometer dedicated for solar observations was constructed in 2 years at Nobeyama, Nagano. It consists of eighty-four 80-cm-diameter antennas arranged in a Tee-shaped array extending 490 m in east-west and 220 m in north-south directions. Since late June of 1992, radio full-disk images of the Sun have been observed for 8 h every day. The spatial resolution is 10” and the temporal resolution is 1 s and also 50 ms for selected events. Every 10 s, correlator data are synthesized into images in real time and displayed on a monitor screen. The array configuration is optimized to observe the whole Sun with high spatial and temporal resolution and a high dynamic range of images. Image quality of better than 20 dB is realized by incorporation of technical advances in hardware and software, such as 1) low-loss phase-stable optical-fiber cables for local reference signal and IF signals, 2) newly developed phase-stable local oscillators, 3) custom CMOS gate-array LSI's of 1-b quadra-phase correlators for 4 × 4 combinations, and 4) new image processing techniques to suppress large sidelobe effects due to the solar disk and extended sources. © 1994 IEEE.

The early phases of three flares, observed by the Nobeyama Radio Heliograph, are studied. Nonthermal and thermal radio sources are identified by comparison with soft X-ray images taken by the Soft X-ray Telescope onboard the Yohkoh satellite. Two of the flares are mainly of nonthermal origin and their location coincides with one of the footpoints of soft X-ray loops. Another flare has both thermal and nonthermal components which start to brighten simultaneously. This suggests that particle acceleration and plasma compression develop simultaneously. © 1994 Kluwer Academic Publishers.

© IEEE 1992. At Nobeyama, a new radioheliograph has been constructed to explicate the mechanism of solar flares. The system receives 17 GHz microwave signals radiating from the sun with 84 antennas and receivers, and synthesizes the two dimensional solar images with the high speed processor. The receive system of the radio heliograph has following performances: the high phase-stability, high gain-stability, fine correction of phase errors, and high speed measuring the complex correlation; so that it can generate precision and clear solar images, at 17 GHz with spatial resolution of 10, time resolution of 50 ms.

Frequency selective surfaces (FSSs) with the Jerusalem-cross array configuration have been developed for simultaneous observations of radio astronomical sources at the 40GHz and 80GHz bands. For supporting material, PET(polyethylene terephthalate: 200×220mm large, 12μm thick, permittivity 3.0) was used, and copper was used for the conducting array. The measured characteristics were in good agreement with the calculated ones. The fabricated FSS has low insertion losses of less than 0.2dB and little distortion of polarization for each band. The characteristics of the developed FSS satisfy radio astronomical requirements. © 1991 Kluwer Academic Publishers.

Frequency selective surfaces (FSS) have been developed for applications to the 45‐m telescope of the Nobeyama Radio Observatory (NRO), the National Astronomical Observatory (NAO), Japan, for simultaneous observations of radio astronomical sources at the 40‐ and 80‐GHz bands. The Jerusalem‐cross array configuration has been used for the conducting array. The designed characteristics satisfy requirements for radio astronomy: small insertion losses and little distortion of polarization. The measured characteristics were in good agreement with the calculated ones. The fabricated FSS has low insertion loss of 0.1 and 0.6 dB at the 40‐ and 80‐GHz bands, respectively. It was found that the distortion of circular polarization is not significant for polarized radio astronomical sources of polarization degree of more than 5 percent. The characteristics of the developed FSS satisfy solar radio astronomical requirements. Copyright © 1990 Wiley Periodicals, Inc., A Wiley Company

We have made aperture synthesis observations of the Orion molecular cloud 1 (OMC-1) in NH3 (1, 1) and (2, 2) emission at 23.7 GHz, using the Nobeyama Millimeter Array (NMA), and obtained 16″ resolution maps for OMC-1 and 8″ resolution maps for the Orion-KL region. We have found filamentary structures (VLSR ∼ 7.9 km s-1) extending over 0.5 pc from the Orion-KL region to the north and northwest directions. These structures are associated with the H2 finger structures and Herbig-Haro objects which are located at the blue-shifted side of the bipolar molecular outflow. Our results suggest that these filaments are ambient molecular cloudlets with shocked surfaces caused by the strong stellar wind from the Orion-KL region. The 8″ resolution NH3 (2, 2) maps show the extended features around the hot core of Orion-KL. These extended features correspond to the rotating disk and shocked shell associated with the bipolar molecular outflow.

Rho Ophiuchi East is one of the molecular outflows discovered in the Nagoya CO survey of star formation regions (Fukui et al.) and was independently discovered by Wootten and Loren. IRAS 16293-2422 is the driving source of the outflow. We have made a detailed observational study of this outflow source in the J = 1-0 and J = 2-1 transitions of carbon monoxide and in the (J, K) = (1, 1) and (2, 2) transitions of ammonia with angular resolutions of 17″-80″. The high-velocity CO emission has been resolved into four compact separate lobes, consisting of two pairs of bipolar lobes, in addition to an extended monopolar blueshifted lobe. We present four possible interpretations for the multiple distribution of the high-velocity molecular gas: (1) three driving engines, (2) two driving engines with strong time variation, (3) two driving engines, one of which is precessing, and (4) dynamical interaction of the high-velocity gas with the dense cloud core. We show that precession does not reproduce the detailed distribution of the high-velocity gas, and we discuss the importance of the dynamical interaction of the outflow with the ambient molecular gas in formation of the CO lobes. The NH3 cloud has a size of ∼2′.5 × 2′.5, being peaked at 1′.7 east of IRAS 16293-2422. This NH3 peak is located just toward the edge of one of the compact blue CO lobes, showing a blueshift of ∼0.5 km s-1 from the rest of the NH3 cloud. The momentum involved in the NH3 peak is nearly equal to that of the CO lobe. Thus, we suggest that the CO lobe has dynamically interacted with the NH3 core, resulting in the acceleration of the NH3 core by 0.5 km s-1. This provides the first direct evidence for an outflow accelerating interstellar molecular gas, strongly suggesting the dynamical importance of outflow in cloud cores where stars are formed.