Japan In Summer Research Articles

Evidence of formation of submicrometer water‐soluble organic aerosols at a deciduous forest site in northern Japan in summer

Semicontinuous measurements of submicrometer water‐soluble organic aerosols and particle size distributions were conducted at a deciduous forest site in northern Japan in August 2010. Increases in particle number concentration were frequently observed in daytime, accompanied by an increase in the concentrations of water‐soluble organic carbon (WSOC). We found that daily averaged WSOC concentrations positively correlated with gross primary production of CO2 by the forest ecosystem (r2 = 0.63) and ambient temperature during daytime. These relations suggest that the formation of WSOC is closely linked to photosynthetic activity by the forest ecosystem, which depends on both temperature and solar radiation. Off‐line chemical analysis of samples of particles with aerodynamic diameter smaller than 1 μm collected during a 2 day event of elevated WSOC levels suggests that photochemical aging of both α‐ andβ‐pinene and isoprene oxidation products contributes to the particle growth and the WSOC mass. Organic tracers of primary biological aerosol particles (PBAPs) showed distinct diurnal variations with a maximum around noontime, also indicating that higher temperature and light intensity induce emissions of PBAPs. However, their contribution to the submicrometer WSOC mass was likely insignificant. During the day, the concentrations of 3‐methyl‐1,2,3‐butanetricarboxylic acid (3‐MBTCA) showed a strong dependence on temperature, and the ratios of WSOC to particle volume concentration increased with an increase in the concentration ratios of 3‐MBTCA to pinonic acid (PA). This result supports a previous proposal that the 3‐MBTCA/PA ratios in submicrometer particles can be a useful tracer for chemical aging of biogenic secondary organic aerosol from forest vegetation.

Development of large format Si(Li) detectors for the GAPS dark matter experiment

The General AntiParticle Spectrometer (GAPS) is a novel approach for indirect dark matter searches that exploits cosmic antideuterons. The GAPS detection method involves capturing antiparticles into a target material with the subsequent formation of an excited exotic atom. The exotic atom decays with the emission of atomic X-rays and charged particles from nuclear annihilation, which uniquely identifies the captured antiparticle. We are currently developing the lithium-drifted silicon (Si(Li)) detector for the GAPS flight experiment. In this paper, we describe the diagnostic tests conducted on three prototype Si(Li) detectors and the noise model to characterize each detector. The GAPS prototype flight, preparatory for a long duration balloon flight from Antarctica in 2016–2017, is scheduled for launch from Japan in summer 2012.

Influences of the variation in inflow to East Asia on surface ozone over Japan during 1996–2005

Abstract. Air quality simulations in which the global chemical transport model CHASER and the regional chemical transport model WRF/chem are coupled have been developed to consider the dynamic transport of chemical species across the boundaries of the domain of the regional chemical transport model. The simulation captures the overall seasonal variations of surface ozone, but overestimates its concentration over Japanese populated areas by approximately 20 ppb from summer to early winter. It is deduced that ozone formation around Northeast China and Japan in summer is overestimated in the simulation. On the other hand, the simulation well reproduces the interannual variability and the long-term trend of observed surface ozone over Japan. Sensitivity experiments have been performed to investigate the influence of the variation in inflow to East Asia on the interannual variability and the long-term trend of surface ozone over Japan during 1996–2005. The inflow defined in this paper includes the recirculation of species with sources within the East Asian region as well as the transport of species with sources out of the East Asian region. Results of sensitivity experiments suggest that inflow to East Asia accounts for approximately 30 % of the increasing trend of surface ozone, whereas it has much less influence on the interannual variability of observed surface ozone compared to meteorological processes within East Asia.

Radiocarbon (14C) Diurnal Variations in Fine Particles at Sites Downwind from Tokyo, Japan in Summer

The radiocarbon ((14)C) of total carbon (TC) in atmospheric fine particles was measured at 6 h or 12 h intervals at two sites, 50 and 100 km downwind from Tokyo, Japan (Kisai and Maebashi) in summer 2007. The percent modern carbon (pMC) showed clear diurnal variations with minimums in the daytime. The mean pMC values at Maebashi were 28 ± 7 in the daytime and 45 ± 16 at night (37 ± 15 for the overall period). Those at Kisai were 26 ± 9 in the daytime and 44 ± 8 at night (37 ± 12 for the overall period). This data indicates that fossil sources were major contributors to the daytime TC, while fossil and modern sources had comparable contributions to nighttime TC in the suburban areas. At both sites, the concentration of fossil carbon as well as O(3) and the estimated secondary organic carbon increased in the daytime. These results suggest that fossil sources around Tokyo contributed significantly to the high daytime concentration of secondary organic aerosols (SOA) at the two suburban sites. A comparison of pMC and the ratio of elemental carbon/TC from our particulate samples with those from three end-member sources corroborates the dominant role of fossil SOA in the daytime.

Evaluation of non-methane hydrocarbon (NMHC) emissions based on an ambient air measurement in Tokyo area, Japan

Non-methane hydrocarbons (NMHCs) are known to have an important role on air quality due to their high reactivity. NMHC analysis has been performed on 148 ambient air samples collected at five different sites in the Kanto area (Tokyo metropolitan area and surrounding six prefectures) of Japan in summer and winter of 2008, and fifty NMHCs have been determined and quantified. A field measurement campaign has been conducted at one of the busiest intersections in Tokyo metropolitan area in winter of 2008. NMHC emissions are evaluated through comparison of distributions of individual NMHCs emitted from motor vehicles, which are estimated from the measurements, with those determined from the current emissions inventory. The comparison revealed that the measured distributions of acetylene, ethylene and toluene showed a good agreement with those estimated from the emissions inventory (the values estimated from the measurements are a factor of 1.5, 0.56 and 2.3 larger than the emissions inventory in median, respectively), however, propane and isobutane are found to be significantly underestimated in the emissions inventory (the measured values were a factor of 18 and 5.1 larger than the emissions inventory, respectively). The significant underestimate of propane can be explained by that the current emissions inventory does not consider emissions from liquefied propane gas (LPG) fueled vehicles. However, for isobutane, reasons for the underestimate are still unclear. Another field measurement has been conducted in summer of 2008, where the air samples have been collected at three different sites on the ground and by a helicopter as well. Remarkable high concentrations of 1-butene and cis- and trans-2-butenes have been sporadically observed in the samples collected at Urayasu in the coastal area of Tokyo bay. Calculated propylene equivalent (PE) concentrations of butenes revealed that those have a significantly important role in ozone formation when the air plume is affected by emissions from their emission sources. The PE concentrations of butenes varied from 0.1 to 39 ppbC, and accounted for 1.5–75% of total PE concentrations at Urayasu. Most of the continuous air quality monitoring stations does not record concentrations of individual hydrocarbons, therefore, the importance of reactive and low concentration hydrocarbon such as butenes might be overlooked in the current emissions inventory and/or air quality model. In this paper, the reliability of NMHC emissions is evaluated based on the field measurements. Their possible impacts on air quality in the Kanto area are discussed as well, based on the calculated propylene equivalent concentrations.

Measures against transmission of pandemic H1N1 influenza in Japan in 2009: simulation model

The first outbreak of pandemic H1N1 influenza in Japan was contained in the Kansai region in May 2009 by social distancing measures. Modelling methods are needed to estimate the validity of these measures before their implementation on a large scale. We estimated the transmission coefficient from outbreaks of pandemic H1N1 influenza among school children in Japan in summer 2009; using this transmission coefficient, we simulated the spread of pandemic H1N1 influenza in a virtual community called the virtual Chuo Line which models an area to the west of metropolitan Tokyo. Measures evaluated in our simulation included: isolation at home, school closure, post-exposure prophylaxis and mass vaccinations of school children. We showed that post-exposure prophylaxis combined with isolation at home and school closure significantly decreases the total number of cases in the community and can mitigate the spread of pandemic H1N1 influenza, even when there is a delay in the availability of vaccine.

Anomalous geographical gap in carbon monoxide mixing ratios over Hokkaido (Japan) in summer 2004

An anomalously low carbon monoxide (CO) episode was observed at Cape Ochi-ishi located in northern Japan in summer 2004. The low CO episode persisted for as long as twelve days from July 27 to August 7, 2004, and the CO levels at Cape Ochi-ishi during this episode were comparable to at Hateruma Island, a southernmost island of Japan. We explored regional distributions of CO and roles of synoptic-scale meteorology in this episode by using a regional chemistry-transport model. The model reproduced the observed levels and day-to-day variations of CO very well, and indicated that the low CO episode widely occurred around Japan. The model simulations revealed the presence of steep gradient in central Hokkaido, explaining the observed differences in CO mixing ratios between Cape Ochi-ishi and Rishiri Island. The eleven-year model results and backward trajectories suggested that the low CO event observed in 2004 was due to rapid transport of pristine air masses from the Pacific Ocean, driven by anomalously stronger easterly flows in the summer of 2004. This mechanism well explained the anomalous patterns observed for methane, carbon dioxide, and molecular hydrogen associated with low CO.

The Kuroshio large meander formation in 2004 analyzed by an eddy‐resolving ocean forecast system

The recent formation of the Kuroshio large meander southeast of the Kii Peninsula during the period from May to July 2004 has been simulated successfully in an eddy‐resolving ocean forecast system (Japanese Coastal Ocean Predictability Experiment). The formation process was examined from the viewpoint of eddy‐Kuroshio interactions using sensitivity experiments that had various initial conditions for eddies in March and May 2004. We confirmed that the large meander does not occur when the trigger meander southeast of the Kyushu Island has small amplitude and that the cyclonic eddy on the offshore side of the Kuroshio contributes to the large meander formation. Our results show that the large amplitude of the trigger meander southeast of Kyushu Island in April 2004 was caused by downstream advection of anticyclonic eddies along the Kuroshio in the East China Sea from east of Taiwan. The results suggest that the successive westward propagation of strong anticyclonic eddies in the subtropical frontal region from 2003 to 2004 was the origin of the formation of the Kuroshio large meander south of Japan in summer 2004.

Environmental gradients determining the distribution of benthic macroinvertebrates in Lake Takkobu, Kushiro wetland, northern Japan

AbstractEffects of environmental variables on the distribution of benthic macroinvertebrates inhabiting sediments were studied at 25 sites along the shoreline of Lake Takkobu in the Kushiro wetland of northern Japan in summer 2003. During the last decade, the lake's status has undergone a drastic shift from clear water dominated by submerged macrophytes to turbid water dominated by phytoplankton. The canonical correspondence analysis showed that four environmental variables explained the significant variation in the macroinvertebrate species composition: submerged plant biomass, bottom sediment organic matter content (OMC), distance from the mouth of the Takkobu River, and bottom‐layer pH. Five species of Chironomidae [Chironomus sp. (except plumosus group), Psectrocladius sp., Corynoneura sp., Parachironomus sp. arcuatus group, and Zavreliella sp.] occurred in sites with relatively lower pH and a high submerged plant biomass, whereas three species of Tubificidae (Tubifex tubifex, Aulodriluslimnobius and Aulodrilus sp.) and two of Chironomidae (Nanocladius sp. and Monodiamesa sp.) occurred in sites with high pH and little vegetation. The three Tubificidae species also preferred organic‐rich sediments. Irrespective of aquatic vegetation, Sphaerium sp. (Bivalvia) and Monodiamesa sp. (Chironomidae) occurred in low‐OMC sites, whereas Tanypus sp. (Chironomidae) preferred high‐OMC sites. The number of macroinvertebrate taxa showed the highest correlation with the number of submerged plants, suggesting that macroinvertebrate species richness was related mostly to submerged plant species diversity in this lake. The quantity and species richness of submerged plants and OMC are thus important determinants of the community structure of macroinvertebrates inhabiting sediments in Lake Takkobu.

Seasonal changes of fatty acid composition and thermotropic behavior of polar lipids from marine macrophytes

Major glyco- and phospholipids as well as betaine lipid 1,2-diacylglycero- O-4′-( N,N,N-tri-methyl)-homoserine (DGTS) were isolated from five species of marine macrophytes harvested in the Sea of Japan in summer and winter at seawater temperatures of 20–23 and 3 °C, respectively. GC and DSC analysis of lipids revealed a common increase of ratio between n−3 and n−6 polyunsaturated fatty acids (PUFAs) of polar lipids from summer to winter despite their chemotaxonomically different fatty acid (FA) composition. Especially, high level of different n−3 PUFAs was observed in galactolipids in winter. However, the rise in FA unsaturation did not result in the lowering of peak maximum temperature of phase transition of photosynthetic lipids (glycolipids and phosphatidylglycerol (PG)) in contrast to non-photosynthetic ones [phosphatidylcholine (PC) and phosphatidylethanolamine (PE)]. Different thermotropic behavior of these lipid groups was accompanied by higher content of n−6 PUFAs from the sum of n−6 and n−3 PUFAs in PC and PE compared with glycolipids and PG in both seasons. Seasonal changes of DSC transitions and FA composition of DGTS studied for the first time were similar to PC and PE. Thermograms of all polar lipids were characterized by complex profiles and located in a wide temperature range between −130 and 80 °C, while the most evident phase separation occurred in PGs in both seasons. Polarizing microscopy combined with DSC has shown that the liquid crystal – isotropic melt transitions of polar lipids from marine macrophytes began from 10 to 30 °C mostly, which can cause the thermal sensitivity of plants to superoptimal temperatures in their environment.

Small-scale temporal variation in propagule supply of an intertidal red alga

A. Bellgrove and M.N. Aoki. 2006. Small-scale temporal variation in propagule supply of an intertidal red alga.Phycologia 45: 458–464. DOI: 10.2216/05-53.1Information on the variability in supply of algal propagules is scarce, hindered by the difficulty in identifying propagules, but this variability may affect the distribution and abundance of algal assemblages. This study examined the small-scale (½ hourly to hourly) temporal variation in propagule supply of Chondrus verrucosus (Gigartinaceae, Rhodophyta) over a dense, isolated bed in south-eastern Japan in summer and winter of 1999. Either 0.5 litre scoop samples or 5 litre pump samples were collected ½ hourly to hourly over 13, 22.5, and 30 h on three occasions in summer (June & July) and 32 h on one occasion in winter (December). Sampling was conducted around either the new moon (two occasions in summer) or full moon (one occasion in both summer and winter) and incorporated full tidal sequences including daytime (summer) and nighttime (winter) low-low (LL) tides. Chondrus verrucosus was the only red alga with spores within the size range of 15–20 μm that was fertile in the study area and surrounds at the time of sampling facilitating identification of spores. Spores in scoop samples were settled onto Petri dishes and identified on the basis of cell shape, colour and size. Pump samples were filtered onto transparent membrane filters and identified using epifluorescence microscopy: C. verrucosus spores fluoresced bright yellow and were easily distinguished from other micro-organisms of similar size, which fluoresced red or green. Results showed that while propagules could be found in the water column at most times, propagule supply of C. verrucosus was greatest during the 1–2 h period following LL tides. Variability in propagule supply was less than in previous studies examining surface or offshore waters. Spore release is thought to be stimulated by either desiccation or salinity changes associated with periods of emersion at low tide followed by re-immersion on incoming tides.

Lightning occurrence data observed with lightning location systems in Japan: 1992-1995

Cloud-to-ground lightning occurrence for years 1992-1995 has been analyzed using the data obtained with nine different lightning location systems in Japan. A total of more than 2 million lightning strokes are observed for the four years and the number of annual lightning strokes is closely related to the weather conditions in summer. Lightning occurs all over Japan in summer but occurrence of lightning is concentrated in the coastal area of the Sea of Japan in winter. Data of thunderdays are compared with the data observed by the Japan Meteorological Agency. The relationship between number of lightning strokes and thunderdays is also obtained. It changes season by season and it is very difficult to express the relations with a single formula.

Ontogenetic diel vertical migration of the planktonic copepodCalanus sinicus in the Inland Sea of Japan

The ontogenetic diel vertical migration of the planktonic copepodCalanus sinicus was investigated in the Inland Sea of Japan in summer 1988, when the water was thermally stratified with a thermocline of ca 5 °C between 35 and 45 m. Stage-specific differences in the diel vertical migration behavior ofC. sinicus were found. Eggs were spawned primarily within the surface-waters between midnight and dawn by ascending females, and sank gradually to deeper waters until they hatched into nauplii. Non-feeding nauplius stages (NI and II) were distributed throughout the water column, but the first feeding stage (NIII) performed an ontogenetic upward migration. NIV to VI and copepodite (C) stages I to III continuously aggregated in the phytoplankton-rich euphotic layer. However, the depth of the median CI to III populations descended as stage progressed. The onset of prominent diel vertical migration took place in CIV, and the amplitude of vertical migration increased with age, being maximal in adult females (CVI♀). Adult males (CVI♂), however, remained in the layer below 20 m, and did not migrate dielly. The ecological significance of ontogenetic diel vertical migration is discussed.

南北向き住戸と東西向き住戸の外壁面が受ける照り返し日射量

Outside walls of a building receive not only direct and diffuse solar radiations coming from the sky but also solar radiation reflected from the ground and the opposite buildings. In an area exposed with high air temperature and strong solar radiation, such as Japan in summer, the reflected solar radiation may have quite significant effect on the thermal environment in houses. To measure the reflected solar radiation with a pyranometer, an upper half cover was used. The measured data showed that the amount of the reflected solar radiation incident on the outside wall was a half of that of the diffuse solar radiation. The variation of the reflected solar radiation depended on that of the direct solar radiation. The reflected solar radiation can be calculated, using the data of direct and horizontal diffuse solar radiation, photoes taken by a fish eye lens, and albedoes of the ground and building surfaces. The north wall opposite the northern building accepts the amount of solar radiation as much as the horizontal diffuse solar radiation, except the lower part of the wall, disregarding winter and summer. The higher story wall, the more reflected solar radiation is increased in both of winter and summer. The reflected solar radiation coming from the opposite buildings is quite large in winter.

Further study of synoptic variability in Wakasa Bay, Japan

Observations of synoptic variability from CTD and current meter measurements in Wakasa Bay, Japan in summer of 1980 and 1981 are compared with the results of 1979 reported by Yamagata, Umatani, Masunaga and Matsuura (1984). It is suggested that the speed and direction of propagation can basically be explained in terms of shelf wave dynamics. In the 1980 event, a dense (colder and more saline) water advanced eastward along the north coast at about 10 km day −1. The lateral scale of the phenomenon was about 30 to 40 km, in agreement with the Rossby internal radius of deformation. The T-S and current data suggest that the 1980 cold event was dominated by phase propagation. In the 1981 event, a light (warmer and less saline) water area advanced eastward at the speed similar to the 1980 cold event, but the T-S and current data suggest that Lagrangian drift of water particles associated with strong eddy motions was not negligible.

標識放流結果から推定された本邦太平洋沿岸ブリ資源の回遊モデルと動態-I

A migration system model was constructed on the basis of information obtained from the tagging experiments. Two migration routes start from Sagami Bay and Kumano-nada area, central Japan. One is southward migration in spring in the direction of Kyushu, and the other is northward migration in summer to northern Japan. Recapture data within the year of release were applied to this system model and the fishing rate, transfer rate, and the rate of disappearance were estimated. In 1926-1938 period, about 80% of southward migrants disappeared from both Kumano-nada and Tosa Bay and discontinuity of the distribution of the population at these points was suggested. In 1963-1965 period the boundary at Kumano-nada disappeared and 85% of fish moved south from there toward Tosa Bay. More than a half of the fish which once disappeared from Sagami Bay and Kumano-nada in the spring season reappeared in northern Japan in summer. The fishing rate for southward migrants in the spring season was about 20% in 1926-1938 period, but in 1963-1965 the rate increased to more than 30% in Sagami Bay and Kumano-nada. The fishing rate was low in northern Japan being not more than 10% in both periods.