Low-grade Progressive Metamorphism of Pelitic Schists of the Sazare area, Sanbagawa Metamorphic Terrain in central Sikoku, Japan

The Sanbagawa metamorphic terrain in the Sazare area, centralSikoku, is divided into three zones of progressive metamorphism,A, B, and C, on the basis of mineral assemblages of peliticschists. The characteristic mineral assemblage of zone A isphengite+chlorite and that of zone C is phengite+chlorite+garnetwith biotite possibly at a higher-grade part. Zone B is transitionalbetween A and C. Variation of the chemistry of garnet rim andchlorite with increasing grade is conspicuous: the MnO and FeOcontents of chlorite decrease and the FeO content of garnetrims increase with grade. The Fe-Mg partition coefficient forthe chlorite—garnet rim pair also changes systematicallywith the grade defined by the assemblage suggesting that theprogressive metamorphism is primarily due to temperature increase.The difference in assemblages between the Barrovian biotitezone and zone C of the present area is due either to the commonoccurrence of clinozoisite in the latter or to the differentparagenetic relations induced by higher-pressure of equilibriumin the Sanbagawa belt as compared with the Scottish one. The thermal structure of the present area revealed by zonalmapping requires the presence of a large-scale overturned structure,which postdated the major mineral formation.     

Aircraft observation of carbon dioxide at 8–13 km altitude over the western Pacific from 1993 to 1999

Abstract The spatial and temporal variations of atmospheric CO₂ at 8–13 km from April 1993 to April 1999 were observed by measuring CO₂ mixing ratios in samples collected biweekly from a commercial airliner between Australia and Japan. The CO₂ growth rate showed a considerable interannual variation, with a maximum of about 3 ppm yr⁻¹ during late 1997. This variation is related to the El Niño/Southern Oscillation (ENSO) events. A year-to-year change related to the ENSO events was also found in the latitudinal distribution pattern of the CO₂ annual mean between 30°N and 30°S. The averaged CO₂ seasonal cycle in the Northern Hemisphere gradually decayed toward the equator, and a relatively complicated variation with a double seasonal maximum appeared in the Southern Hemisphere. A significant yearly change of the seasonal cycle pattern was observed in the Southern Hemisphere. The impact of a tropical biomass-burning injection on the upper tropospheric CO₂ was estimated on the basis of the CO data from the same airliner observation.     

Long-range transport of carbon monoxide from tropical ground to upper troposphere: a case study for South East Asia in October 1997

High concentrations of carbon monoxide (CO) were observed in October 1997 at the upper troposphere of the western tropical Pacific. Transport from the potential sources of CO due to biomass burnings in the tropics was investigated by using a global chemical transport model (CTM) driven by assimilated meteorological data provided from European Centre for Medium-Range Weather Forecasts (ECMWF). A CTM evaluation simulation using water vapor showed that the amount of vertical transport of moisture by large-scale flow was consistent with the precipitation predicted at the convective zone. A series of CTM simulations using 10-day emission periods of an artificial material with lifetime of 60 days indicated that vertical lifting of surface air at the Indonesian archipelago occurred in the concentrated convections west of Sumatra Island. No evidence was found that CO from the Amazon region or Africa significantly contributed to high concentrations in the western tropical Pacific. Transport formed a large-scale anvil below the tropopause by rapid vertical transport and by divergence flow. The average time required for the transport from Kalimantan and Sumatra Island to the point of high CO concentration was about 15 days. High concentrations at an altitude of 10 km in the Southern Hemisphere were transported by large-scale subsidence from the upper tropospheric maximum, which was presumably produced from the sources at Kalimantan and Sumatra Island. Estimated emissions of CO in September and October from Kalimantan and Sumatra were substantially larger than the previous estimates. Omission of chemical reaction was a possible problem for the overestimate, but not significant. The possible problems in the transport were incorrect CTM transport due to insufficient horizontal (2.5×2.5°) and vertical resolution of the CTM, and to inaccuracy in the wind fields at the upper part of the troposphere and a divergent flow pattern in the upper part of the troposphere.