Search Results

You are looking at 1 - 5 of 5 items for

  • Author or Editor: Kaichi Maeda x
  • Refine by Access: All Content x
Clear All Modify Search
Kaichi Maeda

Abstract

No abstract available.

Full access
Kaichi Maeda and Tomiya Watanabe

Abstract

Pulsating aurorae are proposed as a source of the infrasonic waves associated with geomagnetic activity reported by Chrzanowski et al. One of the most plausible mechanisms for generating these long period pressure waves is the periodic heating of the upper air around the 100-km level by auroral bombardment, during pulsating visual aurorae. To see the energetic relation between source input and pressure change at sea level, some theoretical calculations are performed with a simple model of auroral distribution in an isothermal atmosphere. At least 100 erg cm−2 sec−1 of energy flux variation at auroral height is necessary to produce surface pressure amplitudes of the order of 1 dyne cm−2 in this model. The intensity of the pressure waves in this model decreases rapidly outside of the region of auroral activity, indicating the importance of sound-ducts in the upper atmosphere for the propagation of these long period sonic waves.

Full access
Kaichi Maeda and Victor L. Badillo

Abstract

No abstract available.

Full access
Kaichi Maeda and Donald F. Heath

Abstract

Based on the Nimbus-7 solar backscattered UV-radiation (SBUV) data which are free from the instrumental background noise (dark-current) produced by magnetospheric particles, it is found that the southern winter hemispheric ozone densities in the upper stratosphere are nearly 20% higher than their counterparts in the Northern Hemisphere; i.e., the ozone mixing ratios at the 1.5 mb (∼45 km) level are 10.2 μg g−1 at 60°S in July 1979 versus 8.5 μg g−1 at 60°N in December 1979. This is in significant contrast to the well-known hemispheric asymmetry of the total ozone content which is higher in the northern hemispheric winter than in the southern hemispheric winter. Comparisons of those findings with the previously obtained similar results from the Nimbus-4 backscattered UV radiation (BUV) experiment have manifested that the dark-current effect on the latter was negligible. Therefore, using the stratospheric temperature which was observed by means of the selective chopper radiometer (SCR) simultaneously with the BUV experiments on the Nimbus-4 for 1970 and 1972, the cause of these asymmetries due to the temperature dependent photo-chemistry is examined. The result indicates:

  1. The hemispheric asymmetries of the ozone distribution in the summer mesosphere and upper stratosphere are fully ascribable to the hemispheric temperature differences due to the combined effects of the earth's orbital ellipticity and its tilted spin axis from the ecliptic plane.
  2. On the other hand, the wintertime hemispheric asymmetries imply the presence of additional effects such as stronger dynamic heating in the Northern Hemisphere resulting from orographic differences between the two hemispheres.
Full access
Tadashi Aruga, Kaichi Maeda, and Donald F. Heath

Abstract

A technique for determining cloud-top height by means of backscattered ultraviolet (BUV) solar radiation is presented. Cloud-top heights can be inferred using this technique if both the BUV radiance and its degree of polarization are measured by a spacecraft and compared with theoretical values. The cases of satellites with high-inclination orbits and geosynchronous satellites are discussed here. Based on calculations of radiance and polarization, the resolutions of cloud-top height determinations are roughly estimated in both cases. The estimates show that inference is possible as long as the angle between the direction of the sun and the satellite from the point of interest in the atmosphere is larger than about 10°. The estimates also indicate that the cloud-top height resolution depends on solar zenith angle θ 0 in the case of nadir observation by satellites in nonequatorial orbits: The resolution is ∼0.5 km for θ 0 = 30° and ∼0.3 km for larger θ 0. On the other hand, when observations are made by geosynchronous satellites, the resolution depends strongly on the latitude of the point of interest, α1; a resolution within 0.4 km can be achieved for α1 ≤ 65° (0.2 km resolution can be obtained for middle latitudes). Resolution becomes rapidly worse with increasing latitude, and α1 ≈ 70° seems to be the limit of observations with this technique.

Full access