著者

Haruka Okui Kaoru Sato

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.16, pp.64-69, 2020 (Released:2020-04-11)

参考文献数

18

被引用文献数

1

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Using long-term high-resolution operational radiosonde observation data from nine stations in the subtropics and mid-latitudes of Japan, this study performed statistical analysis of the dynamical characteristics of gravity waves (GWs). Wave generation by shear instability in summer was a particular focus because orographic GWs cannot propagate deep into the middle atmosphere through their critical layer in the lower stratosphere. The kinetic energy of summer stratospheric GWs is markedly large south of 37°N. Hodograph analysis revealed that GWs propagating eastward relative to the ground are dominant in summer. The percentage of GWs propagating energy upward (downward) is large above (below) the height at which the mean occurrence frequency of shear instability is high. The time series of the kinetic energy of stratospheric GWs exhibited statistically significant positive correlation with the occurrence frequency of shear instability slightly below the tropopause. These findings strongly suggest the possibility of excitation of summer stratospheric GWs by shear instability above the jet. The shear instability condition is satisfied more frequently in the region 30°N-35°N. This is probably related to two characteristics of the background fields slightly below the tropopause: larger vertical shear of zonal winds at higher latitudes and lower static stability at lower latitudes.

著者

Masashi Kohma Kaoru Sato

出版者

(公社)日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.9, pp.9-14, 2013 (Released:2013-02-02)

参考文献数

27

被引用文献数

1

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It is shown that there are two types of wave solutions trapped at the boundaries which owe to the Coriolis force proportional to the meridional component of the earth's rotation vector (hereafter referred to as the fH force) under the nontraditional approximation (non-TA). One is a type of Kelvin waves (non-TA Kelvin waves) trapped on the eastern and western boundaries. Unlike traditional Kelvin waves (TA Kelvin waves), non-TA Kelvin waves trapped on the western (eastern) boundary can have northward (southward) phase and group velocities in the Northern Hemisphere (NH). The other is a type of Rossby waves trapped on the ground. The external Rossby waves can have wave structure in the vertical and amplitudes decaying with height. Moreover, the fH force modifies even the characteristics of TA Kelvin waves trapped on the southern and northern boundaries: In the NH, the Kelvin waves trapped on the southern boundary have an upper limit (kc) to the zonal wavenumber (k), and those with large k (> kc) trapped on the northern boundary have eastward phase velocity in the NH. The latter is regarded as the third type of edge waves unique to non-TA.

著者

Haruka Okui Kaoru Sato

出版者

Meteorological Society of Japan

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

pp.2020-011, (Released:2020-03-13)

被引用文献数

1

---

Using long-term high-resolution operational radiosonde observation data from nine stations in the subtropics and mid-latitudes of Japan, this study performed statistical analysis of the dynamical characteristics of gravity waves (GWs). Wave generation by shear instability in summer was a particular focus because orographic GWs cannot propagate deep into the middle atmosphere through their critical layer in the lower stratosphere. The kinetic energy of summer stratospheric GWs is markedly large south of 37°N. Hodograph analysis revealed that GWs propagating eastward relative to the ground are dominant in summer. The percentage of GWs propagating energy upward (downward) is large above (below) the height at which the mean occurrence frequency of shear instability is high. The time series of the kinetic energy of stratospheric GWs exhibited statistically significant positive correlation with the occurrence frequency of shear instability slightly below the tropopause. These findings strongly suggest the possibility of excitation of summer stratospheric GWs by shear instability above the jet. The shear instability condition is satisfied more frequently in the region 30°-35°N. This is probably related to two characteristics of the background fields slightly below the tropopause: larger vertical shear of zonal winds at higher latitudes and lower static stability at lower latitudes.

著者

Yoshihiro Tomikawa Masashi Kohma Masanori Takeda Kaoru Sato

出版者

公益社団法人 日本気象学会

雑誌

SOLA (ISSN:13496476)

巻号頁・発行日

vol.19, pp.86-93, 2023 (Released:2023-05-23)

参考文献数

31

被引用文献数

1

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An intensive balloon-borne observation was performed at Syowa Station in the Antarctic (69.0°S, 39.6°E) in July 2016 using Cryogenic Frostpoint Hygrometers (CFH) and Electrochemical Concentration Cell (ECC) ozonesondes. High water vapor concentration was observed in the upper troposphere in two out of five observations. Trajectory analysis and atmospheric reanalysis data showed that moist air was transported into the upper troposphere due to the upwelling in front of a trough. While only isentropic transport was dominant in one case, both the isentropic transport and diabatic heating contributed to the upward transport in the other case. In another case where the air parcels came over the Antarctic continent, the water vapor concentration in the upper troposphere was lower than in the other cases. These results suggest that transport of air parcels with different origins by synoptic-scale disturbances controls water vapor concentration in the Antarctic upper troposphere.