187 research outputs found
熱帯対流圏界面付近に存在する赤道ケルビン波の時空間構造の解明
No full text平成16-17年度科学研究費補助金(基盤研究(C))研究成果報告書 課題番号：16540398 研究代表者：塩谷雅人 (京都大学生存圏研究所教授
Observational evidence and dynamical interpretation of the total ozone variations in the equatorial region
No full textThe total ozone amount is sensitive to the general circulation changes in the lower stratosphere due to the photochemically inactive nature of ozone there. In the equatorial region, such circulation changes arise from the quasi-biennial oscillation (QBO) of the stratospheric zonal wind and the El Nino/Southern Oscillation (ENSO). In the first half of this study we present observational results of the long-term variations in the equatorial ozone field using the 11 year Total Ozone Mapping Spectrometer (TOMS) data, by paying special attention to the longitudinal structure. In the latter half we try to understand quantitatively these variations by using a simple mechanistic relationship. We hypothesis that the ozone modulating processes are attributable to two dynamical effects, the advection effect and tropopause effect, owing to the strong vertical stratification of ozone existing just above the tropopause. The advection effect comes from the vertical motion which maintains the temperature structure, compensating for the radiative damping. The tropopause effect is associated with the altitude change of the tropopause. The total ozone variations in the tropics is discussed in terms of these two dynamical processes with the aid of mechanistic equations combined with the wind and sea surface temperature (SST) observations. The interactions between tropical and extratropical latitudes are beyond the scope of this study. Photochemical effects are also neglected. Details of this study are given by Shiotani (1992) and Hasebe (1992)
Recent research results and activities for the protection of ozone layer based on "Scientific Assessment of Ozone Depletion: 2018"
No full text最近、「オゾン層破壊の科学アセスメント」の最新刊(Scientific Assessment of Ozone Depletion: 2018)が公開された。ここでは、そのアセスメントレポートで取り上げられている主要な話題を簡単に紹介して、オゾン層研究の動向とその保護に向けた取り組みの現状について紹介する
The 26th SPARC Scientific Steering Group meeting
No full textThe 26th SPARC Scientific Steering Group (SSG) meeting took place at International Community House in
Kyoto, Japan, from 6 to 8 October 2018, organised
by the Japanese SSG member, Kaoru Sato (Tokyo university) with significant assistance by Shigeo Yoden
and Masato Shiotani (both from Kyoto university). It
immediately followed the 6th SPARC General Assembly (see separate report on page 8). Neil Harris
guided through the agenda and Judith Perlwitz joined
via a live weblink from Boulder
Condition Assessment of Highly-loaded Low-speed Bearings Using Acoustic Emission Monitoring: A Feasibility Study
No full textIn the present study, feasibility of implementing an acoustic emission (AE) system for condition monitoring of highly-loaded and low-speed roller bearings has been quantitatively investigated. To evaluate the transmission of damage-induced AE signals inside the bearing and their detectability on the accessible surfaces, stress wave propagation through the complex geometry and interfaces of a representative offshore bearing has been studied experimentally. The results suggest that in the investigated frequency ranges, the AE signals that pass through the bearing rollers and their interface with the inner and outer raceways can potentially remain of sufficient strength to be detected for condition assessment of these bearings.Accepted Author ManuscriptShip and Offshore StructuresShip Hydromechanics and Structure
南半球対流圏における帯状平均場の長周期変動について
No full textThis paper presents an observational study of the low-frequency variation in the Southern Hemisphere troposphere, using the global analyses for 1980-85 provided by the European Center for Medium Range Weather Forecasts. An empirical orthogonal function (EOF) analysis is made for the zonal mean geopotential height at 1000 mb to capture the variation. Based on time series of the second EOF coefficients, which represent the dominant non-seasonal low-frequency variation in the Southern Hemisphere, we define four typical events: negative extreme (D-), positive extreme (D+), negative to positive transition (T+), and positive to negative transition (T-) events. The variations on a hemispheric scale show a barotropic seesaw pattern with an almost axisymmetric node around 60°S and wavenumber 3 anomalies superimposed on it. Maximum westerlies at 500 mb are located at higher latitudes in D- event (50-60°S) than in D+ event (30-40°S). In association with the location of maximum westerlies, storm activity (defined as temporal variances of the high-pass (≤6 day) height field data) shows that large variation around 50°S occupies the entire latitude circle for a D- event but it is weaker in the western hemisphere for a D+ event. Composite analyses on a daily basis are made of several physical quantities at 500 mb for the four events. It is found that the latitudinal movement of maximum westerlies is quicker in T+ events than in T- events, in addition to the higher-latitude maximum westerlies in D- events than in D+ events. The zonal mean temperature is colder at high latitudes and warmer at middle latitudes in D- events than in D+ events, corresponding to the stronger polar vortex resulting from the steeper temperature gradient and more vigorous storm activity in D- events than in D+ events. The eddy momentum flux plays an important role especially during transition events; there is large equatorward transport of momentum at high latitudes around the key day of a T+ event and larger poleward transport at middle latitudes around the key day of a T- event. The heat flux seems to play a less important role. The acceleration of mean zonal winds is mainly determined as a residual between the momentum flux convergence and the Coriolis force.ヨーロッパ中期気候予報センターが提供する1980年から1985年までの全球解析データを用いて、南半球対流圏における長周期変動に関する観測的研究をおこなった。まず、1000mbの帯状平均高度場のデータに対して経験的直交関数(EOF)解析をおこないこの変動をとらえた。 EOF解析の第2成分(この成分が南半球において卓越する、季節変動成分とは異なる長周期変動を代表する)の時系列にもとついて以下の4つの典型的なイベントを定義した:負極のイベント(D-)、正極のイベント(D+)•負から正への遷移イベント(T+)、正から負への遷移イベント(T-). 半球規模のこの変動は、60°S付近にほぼ軸対称的な節を持ち波数3の偏差がその上に重なった順圧的なシーソーパターンを示す。500mbにおける西風の最大はD+イベント(30-40°S)よりD-イベント(50-60°S)のほうが高緯度に位置する。西風最大の位置と関連して傾圧波動の活動性(バイパス(≤6日)フィルターをかけた高度場の時間変動として定義する)は、D-イベントでは50°S付近の緯度円をぐるりととり囲むようにしてその活発域が存在するのに対し、D+イベントでは東半球に限られる。 次に、4つのイベントについて500mbにおけるいくつかの物理量に関しコンポジット解析をおこなった。西風の最大がD+イベントによりD-イベントのほうが高緯度に位置するのに加えて、その時間的な緯度方向の動きはT-イベントよりT+イベントの方が速い。帯状平均した温度については、D+イベントよりD-イベントの方が高緯度で冷たく中緯度で暖かい。これはD+イベントよりD-イベントにおいて温度勾配が急で傾圧波動の活動性が活発なために極夜ジェットが強いことと対応している。渦運動量輸送は特に遷移イベントにおいて重要な役割を果たす。T+イベントの基準日付近では、高緯度において赤道向きの大きな運動量輸送が見られる。いっぽうT-イベントの基準日付近では、中緯度において極向きの大きな運動量輸送が見られる。これに対し、熱輸送は重要な役割を果していない。また平均帯状風の加速はおもに運動量輸送の収束とコリオリの力との残差として決まっていることがわかった
Middle atmospheric chemistry and dynamics: results from the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)
No full textOzone and water vapor observations in the equatorial Pacific(RECENT RESEARCH ACTIVITIES)
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