Dynamical Modulation of Wintertime Synoptic-Scale Cyclone Activity over the Japan Sea due to Changbai Mountain in the Korean Peninsula

The dynamical impact of the Changbai Mountain Range in the Korean Peninsula on the extratropical cyclone activity over the Japan Sea in early winter is examined using the Weather Research Forecasting model. We have conducted two independent long-term integrations over 15 winter months (December only) from 2000 to 2014 with and without modified topography. The results show that the Changbai Mountain Range plays a vital role in increasing cyclone track frequency, low-level poleward eddy heat flux, and the local deepening rate over the Japan Sea through enhancement of the lower-tropospheric baroclinic zone (LTBZ). This mountain range gives rise to activation of the synoptic-scale cyclone activity over that region. From our case study on three typical cyclones, it is found that mesoscale structures in the vicinity of a cyclone’s center are dynamically modulated when it passes through the LTBZ and that cyclogenesis is triggered around that zone. A vorticity budget analysis shows that the stretching term relevant to enhanced low-level convergence plays a dominant role in intensifying cyclonic vorticities. We confirmed that the composite features of the three typical cases are consistent with the statistical ones of the dynamical modulation of the Changbai Mountain on synoptic-scale cyclone activity

Reconstruction of past atmospheric CH4 concentration from the firn air data at Dome Fuji (scientific note)

Air samples were collected from different depths of the firn layer at Dome Fuji in December 1998 and analyzed for CH4 concentrations. The age distribution of CH4 in the firn was calculated by using a one-dimensional numerical model, and then the inverse method was applied to reconstruct variations of atmospheric CH4 in the past. The age distribution function was calculated by including processes of molecular diffusion, downward air advection and bubble trapping in the snow-ice transition zone. Once the age distribution function is calculated, the vertical distribution of CH4 in the firn layer can be reconstructed by a linear combination of the age distribution functions weighted by the atmospheric CH4 concentrations in the past. Therefore, the most plausible past atmospheric record of CH4 can be derived iteratively so that its observed profile in the firn layer was reproduced well. In order to check the calculation scheme, the estimated variation of atmospheric CH4 was compared with direct measurements in the Antarctic region. They were in good agreement with each other, even for rapid slowing down of the secular increase observed in the 1990\u27s

Molecular-Cloud-Scale Chemical Composition I: Mapping Spectral Line Survey toward W51 in the 3 mm Band

We have conducted a mapping spectral line survey toward the Galactic giant molecular cloud W51 in the 3 mm band with the Mopra 22 m telescope in order to study an averaged chemical composition of the gas extended over a molecular cloud scale in our Galaxy. We have observed the area of $25' \times 30'$, which corresponds to 39 pc $\times$ 47 pc. The frequency ranges of the observation are 85.1 - 101.1 GHz and 107.0 - 114.9 GHz. In the spectrum spatially averaged over the observed area, spectral lines of 12 molecular species and 4 additional isotopologues are identified. An intensity pattern of the spatially-averaged spectrum is found to be similar to that of the spiral arm in the external galaxy M51, indicating that these two sources have similar chemical compositions. The observed area has been classified into 5 sub-regions according to the integrated intensity of $^{13}$CO($J=1-0$) ($I_{\rm ^{13}CO}$), and contributions of the fluxes of 11 molecular lines from each sub-region to the averaged spectrum have been evaluated. For most of molecular species, 50 % or more of the flux come from the sub-regions with $I_{\rm ^{13}CO}$ from 25 K km s$^{-1}$ to 100 K km s$^{-1}$, which does not involve active star forming regions. Therefore, the molecular-cloud-scale spectrum observed in the 3 mm band hardly represents the chemical composition of star forming cores, but mainly represents the chemical composition of an extended quiescent molecular gas. The present result constitutes a sound base for interpreting the spectra of external galaxies at a resolution of a molecular cloud scale ($\sim10$ pc) or larger.Comment: Accepted for publication in Ap

Autonomous Navigation, Guidance and Control of Small Electric Helicopter

In this study, we design an autonomous navigation, guidance and control system for a small electric helicopter. Only small, light-weight, and inaccurate sensors can be used for the control of small helicopters because of the payload limitation. To overcome the problem of inaccurate sensors, a composite navigation system is designed. The designed navigation system enables us to precisely obtain the position and velocity of the helicopter. A guidance and control system is designed for stabilizing the helicopter at an arbitrary point in three-dimensional space. In particular, a novel and simple guidance system is designed using the combination of optimal control theory and quaternion kinematics. The designs of the study are validated experimentally, and the experimental results verify the efficiency of our navigation, guidance and control system for a small electric helicopter.ArticleINTERNATIONAL JOURNAL OF ADVANCED ROBOTIC SYSTEMS. 10:54 (2013)journal articl

Reconstruction of the atmospheric CO2 concentration history from an Antarctic deep ice core, Dome Fuji using a wet extraction technique: analysis procedures,dating of air in ice and concentration variations (scientific paper)

In order to deduce the atmospheric CO2 concentration variations over the past 320 kyr, air samples were extracted from the Dome Fuji deep ice core using a wet extraction method, and their CO2 concentration values were determined with a reproducibility of 1.0 ppmv. By measuring the CO2 concentrations of firn air samples collected at Dome Fuji, it was found that the effective bubble close-off depth can be defined by the mid-point of the close-off zone. For dating the air in the ice core, the age difference between ice and air (Δage) was estimated by using a densification model to be between 1000 and 5000 years, showing small and large values during the interglacial and glacial periods, respectively, due primarily to variations of precipitation. The CO2 concentration variations with a mean time resolution of about 1.1 kyr over the last three glacial-interglacial cycles showed a good correlation with those of δ18O, which suggests that the Southern Ocean played an important role in the variation of the atmospheric CO2 concentration during the last three glacial-interglacial cycles

日本における小運送業の発展と小運送問題への対応

学位の種別: 課程博士審査委員会委員 : (主査)東京大学教授 武田 晴人, 東京大学教授 加瀬 和俊, 東京大学教授 谷本 雅之, 東京大学教授 中村 尚史University of Tokyo(東京大学

Mixing time and simulated annealing for the stochastic cellular automata

Finding a ground state of a given Hamiltonian on a graph $G=(V,E)$ is an important but hard problem. One of the potential approaches is to use a Markov chain Monte Carlo to sample the Gibbs distribution whose highest peaks correspond to the ground states. In this paper, we investigate a particular kind of stochastic cellular automata, in which all spins are updated independently and simultaneously. We prove that (i) if the temperature is fixed sufficiently high, then the mixing time is at most of order $\log|V|$, and that (ii) if the temperature drops in time $n$ as $1/\log n$, then the limiting measure is uniformly distributed over the ground states.Comment: 16 pages, 8 figure