Engineering topics

Iwata, A.

Publications and source records attributed to Iwata, A..

4 records

NASA NTRS1990

Balloon-Borne Measurements of Total Reactive Nitrogen, Nitric Acid, and Aerosol in the Cold Arctic Stratosphere

Total reactive nitrogen (NO(Y)) between 15 and 29 km was measured for the first time on board a balloon within the Arctic cold vortex. Observations of HNO3, aerosol, and ozone were made by instruments on the same balloon gondola which was launched from Esrange, Sweden (68 deg N, 20 deg E) on January 23, 1989. The NO(y) mixing ratio was observed to increase very rapidly from 6 ppbv at 18 km altitude to a maximum of 21 ppbv at 21 km, forming a sharp layer with a thickness of about 2 km. A minimum in the NO(y) mixing ratio of 5 ppbv was found at 27 km. The measured HNO3 profile shows broad similarities to that of NO(y). This observation, together with the observed very low column amount of NO2, shows that NO(x) had been almost totally converted to HNO3, and that NO(y) was composed mainly of HNO3. The enhanced aerosol concentration between 19 and 22 km suggests that the maximum abundance of HNO3 trapped in the form of nitric acid trihydrate (NAT) was about 6 ppbv at 21 km. The sampled air parcels were highly supersaturated with respect to NAT. Although extensive denitrification throughout the stratosphere did not prevail, an indication of denitrification was found at altitudes of 27 and 22 km, and between 18 and 15 km.

Kondo, Y.↗

NASA NTRS1989

Profiles of nitric oxide in the upper stratosphere

Results are presented from NO measurements obtained with a chemiluminescent NO detector and an in situ ozone instrument aboard high altitude balloons launched at Air sur L'Adour and Gap, France. NO profiles were obtained between 35 and 40 km in the late morning of September 17, 1987 and the early afternoon of June 18, 1988. The average NO concentration was 9 ppbv at 35 km, increasing with altitude to 11.5 ppbv at 40 km. The difference in the temperature profile significantly contributes to the observed change in the NO concentration.

Kondo, Y.↗

NASA NTRS1985

Behavior of decaying El Chichon cloud over Toyokawa, Japan (35 deg N) observed by 532-NM lidar

The stratospheric aerosol state in 1982 and 1983 was in a violet excitation due to the eruption of Mt. El Chichon. A number of direct and indirect soundings of the stratosphere confirmed that the aftereffect of it covered almost the entire Northern Hemisphere by the end of 1982 (e.g., POLLACK et al., 1983). The lidar system constructed at Toyokawa (34.8 deg N, 137.4 deg E) have entered routine base observations since December 1982 (IWATA et al., 1983). The state of observations was 8 months after the eruption, and researchers missed monitoring the drastic variations in the stratosphere just following the event. However, the El Chichon cloud over Japan was reported to have reached the second maximum concentration in November or December 1982 according to the lidar observations at Tsukuba, Nagoya and Fukuoka, so the researchers' observations corresponded to the decaying phase of it. Presented are some characteristics of the aerosol profile over Toyokawa during a period of 20 months from December 1982 to July 1984.

Takagi, M.↗

NASA NTRS1985

Nitric oxide profile from 7 to 32 km

An analysis is given of some results of the LIMS experiment, launched on the Nimbus 7 satellite on October 24, 1978 for the purpose of sounding the middle atmosphere composition and structure. One of the LIMS channels was centered spectrally in the 6 micron region to measure vertical profiles and the global distribution of NO2 mixing ratio. The data reveal that NO2 is highly variable with altitude, latitude, longitude and time. Steep latitudinal gradients are observed in high latitude winter ('the NO2 cliff') when a wave number one pattern exists in the geopotential height field. The daytime gradient under these conditions is less than that for the night. The summer hemisphere column amount is considerably greater (by a factor of about 2) than in the winter hemisphere. The largest mixing ratios occur at 4 mb at night (about 20 ppbv) and 9 mb in the day (about 7 ppbv) and the latitude region of the peak mixing ratio is skewed toward the Southern Hemisphere. The mixing ratio variability is greater at night (by a factor of about 2 to 3) than in the day and there are significant long-term changes revealed by mixing ratio time series analyses on a pressure vs time grid.

Matthews, W. A.↗