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Kashiwa, Japan

Wada A.,Meteorological Research Institute | Midorikawa T.,Geochemical Research Institute | Ishii M.,Geochemical Research Institute | Motoi T.,Meteorological college
Journal of Geophysical Research: Oceans

A simple chemical scheme was introduced into the Meteorological Research Institute Community Ocean Model (MRI.COM) for investigating the rapid CO 2 flux increase at a moored buoy in the East China Sea caused by the passages of Typhoons Tina and Winnie in 1997. MRI.COM well reproduced variations in the observed water temperature and pCO2 sea at 1 m depth and in the air-sea CO2 flux at the buoy. Even though the analyzed magnitudes of the air-sea CO2 fluxes were of the same order, the sudden CO2 flux change occurred nearly 2 days after Tina and nearly 3 days after Winnie. The increase in pCO2 sea normalized to a temperature of 29C induced by Winnie appeared longer than that induced by Tina. The numerical simulation results showed clear differences in the oceanic response between the two typhoons. In the case of Tina, upwelling along the continental shelf played a crucial role in rapidly decreasing the water temperature and transporting seawater with low pCO2 sea and high dissolved inorganic carbon (DIC) to the upper ocean. In contrast, water with relatively high pCO2 sea and low DIC transported by strong horizontal advection of the Kuroshio Current was vertically mixed by the passage of Winnie, resulting in a cool, deep mixed layer at the buoy. The surface seawater hydrogen ion concentration (pH) temporarily decreased during the passages of Tina and Winnie. In the case of Tina, pH decreased by at most 0.03 and for only 1 day. Copyright 2011 by the American Geophysical Union. Source

Oda M.,Meteorological Research Institute | Kanehisa H.,Meteorological college
Journal of the Meteorological Society of Japan

The interaction between Rossby and gravity waves is examined in a vertical-zonal two-dimensional model, in which the basic state has an upward gradient of buoyancy at a lower level and a downward gradient of horizontal vorticity at a higher level. Because of the gradients, there exist westward-propagating upper Rossby and westward- and eastward-propagating lower gravity waves, where the propagation is relative to the fluid. The initial value problem for the disturbance is analytically solved. The temporal evolution of the analytical solution from an initial value shows the following characteristics. Resonant interaction between the westward-propagating upper Rossby wave and the eastward-propagating lower gravity wave is possible, in the same way as between two counter-propagating Rossby waves in barotropic and baroclinic problems. On the boundary in the parameter space between the unstable region, where resonant exponential growth occurs, and the stable region, where the solution oscillates, the marginal solution grows as a linear function of time. As in other instability problems, the marginal linear growth in the present model is not trivial. For small horizontal wave numbers, the westward-propagating gravity wave makes a non-negligible contribution to the resonant interaction between the westward-propagating Rossby wave and the eastward-propagating gravity waves. © 2015, Meteorological Society of Japan. Source

Zhu C.,Hokkaido University | Yoshikawa-Inoue H.,Hokkaido University | Matsueda H.,Meteorological Research Institute | Sawa Y.,Meteorological Research Institute | And 3 more authors.
Atmospheric Environment

Atmospheric 222Rn was monitored from December 2008 to November 2010 on Rishiri Island (45°07'N, 141°12'E), northernmost Japan. Seasonal 222Rn variation was characterized by high concentrations from November to February and low concentrations from May to July, caused by the alternation of continental and maritime fetch regions. 222Rn tracer and back trajectory cluster analyses indicated that the predominant continental fetch region was southeastern Siberia and northeastern China. 222Rn emitted from China and South Korea, whose economies are growing rapidly, did not significantly affect the Rishiri site. The major maritime fetch region was the Sea of Okhotsk and the Bering Sea. A global three-dimensional model (NICAM-TM) accurately simulated 222Rn concentrations on Rishiri Island and in the seasonal fetch regions. The time series of 222Rn data will make it possible to evaluate the sources and sinks of atmospheric greenhouse gases being monitored at Rishiri Island, which complements other sites in the Asia-Pacific rim region, and to validate model simulations used to examine trans-boundary air pollution. © 2011 Elsevier Ltd. Source

Hira S.,Japan Meteorological Agency | Kanehisa H.,Meteorological college
Journal of the Meteorological Society of Japan

In this study, an analytical solution of nocturnal low level jets (LLJs) is presented. The present model is an extension of Blackadar, who described the nocturnal LLJ as a result of an inertial oscillation. In the present model, the momentum equation in the daytime atmospheric boundary layer includes a term representing convective mixing in addition to mixing with a constant diffusion coefficient. With the convective mixing, the daytime equilibrium wind velocity becomes vertically more uniform than the Ekman solution. In the nighttime atmospheric boundary layer, the convective mixing is assumed to be absent and the diffusion coefficient, which is assumed to be a constant, is smaller than that in the daytime. Without the convective mixing, the nighttime equilibrium wind velocity is the same as that of the Ekman solution. The analytical solution describes the temporal evolution of nighttime wind velocity as a damped inertial oscillation around the nighttime equilibrium wind velocity, starting from daytime equilibrium wind velocity. By appropriately selecting the values of parameters in the analytical solution, some previously published results are reproduced. For example, the height of maximum wind speed decreases as time goes on. There exist backward inertial oscillations in addition to the well-known forward inertial oscillations. In the lower levels, the oscillations are rapidly damped. © 2015, Meteorological Society of Japan. Source

Wada A.,Meteorological college | Matsueda H.,Meteorological Research Institute | Sawa Y.,Meteorological Research Institute | Tsuboi K.,Meteorological Research Institute | Okubo S.,Japan Meteorological Agency
Atmospheric Environment

We analyzed seasonal and geographical variations of the enhancement ratios of trace gases of the Asian continental pollution (ACP) events observed over the western North Pacific region. The ACP events were identified by using continuous carbon monoxide (CO) measurements taken at three monitoring stations of Minamitorishima (MNM), Yonagunijima (YON), and Ryori (RYO) in Japan for more than 10 years. The frequency of ACP events at MNM and YON increased in the winter and early spring seasons, but not at RYO. The enhanced concentrations of CO (ΔCO) associated with the ACP events showed a clear seasonal variation at MNM and YON, but not at RYO. Other trace gases of methane (CH4), carbon dioxide (CO2), and ozone (O3) were simultaneously enhanced for many of the ACP events, and were highly correlated with ΔCO. The frequency distributions of the enhancement ratios of ΔCH4/ΔCO, ΔCO/ΔCO2, and ΔO3/ΔCO depended largely on the geographical locations of the stations. Distinct seasonal variations in the enhancement ratios showed a decrease in ΔCH4/ΔCO but an increase in ΔCO/ΔCO2 in the winter and early spring at all three stations, although their seasonal amplitudes were different each station. These results indicate that the chemical compositions associated with the ACP events were considerably influenced by the seasonal variations in the trace gas emission ratios of the Asian continental source regions, with increased fluxes of CH4 in summer and CO in winter. Contributions to the ΔCH4/ΔCO and ΔCO/ΔCO2 ratios from the photochemical evolution during atmospheric transport were estimated to be not significant, while the seasonal changes in the ΔO3/ΔCO ratio were controlled significantly by the photochemistry. © 2011 Elsevier Ltd. Source

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