Ibaraki, Japan
Ibaraki, Japan

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Mashiko W.,Meteorological Research Institute | Inoue H.Y.,Meteorological Research Institute | Hayashi S.,Meteorological Research Institute | Kusunoki K.,Meteorological Research Institute | And 11 more authors.
Scientific Online Letters on the Atmosphere | Year: 2012

Two adjacent shear lines accompanied by wind gusts exceeding 20 m s-1 passed over the Shonai region on the Japan Sea coast during a moderate cold-air outbreak on 12 December 2010. The structure of the shear lines were examined using simulation results and observational data including high-frequency upper-air soundings. Simulation results revealed that cold-airmass outflow from the Eurasian Continent had a split-flow pattern due to the blocking effect of the Changbai Mountains. One is from the south side of the mountains (SCF), and the other is from the north side (NCF). NCF also has two streams: a shallow southward-meandering flow on the south and a slightly deeper straight flow on the north. A shallow shear line was formed between SCF and the shallow southward-meandering flow of NCF. The deeper straight flow of NCF sharply formed another shear line on the north at around 1-km height with SCF. This result implies that the shear lines accompanied by wind gusts on the Japan Sea coast during a coldair outbreak have various structures and that the horizontal wind shear a little above the surface could cause surface wind gusts. © 2012, the Meteorological Society of Japan.

Uchiyama A.,Japan Meteorological Agency | Yamazaki A.,Japan Meteorological Agency | Kudo R.,Japan Meteorological Agency | Kobayashi E.,Aerological Observatory | And 2 more authors.
Journal of the Meteorological Society of Japan | Year: 2014

To investigate aerosol optical properties, the Meteorological Research Institute has been continuously measuring scattering and absorption coefficients since January 2002 by using an integrating nephelometer and one- and three-wavelength absorption photometers in dry air conditions at Tsukuba, Japan. We used these optical data to investigate trends of aerosol properties and climatology from 2002 to 2013. The results showed that most aerosol characteristics had seasonal variation and decreasing or increasing trends significant at the 95 % confidence level. From 2002 to 2013, the extinction coefficient at 550 nm and absorption coefficient at 530 nm had statistically significant decreases of -1.5 × 10-6 and -5.4 × 10-7 m-1 year-1, respectively. In the same period, the scattering coefficient showed a non-significant decrease of -8.8 × 10-7 m-1 year-1. The single scattering albedo (SSA) at 550 nm had a significant increasing trend of 7.4 × 10-3 year-1. Asymmetry factors did not show a significant trend. The increasing trend in the extinction Ångström exponent was significant, whereas the trend in the effective radius was not significant. The increasing trend of 2.1 × 10-2 year-1 in the absorption Ångström exponent from 2006 to 2013 was significant. This tendency suggests a compositional change of light-absorbing aerosol. Frequency distributions of aerosol properties were investigated during 2006-2012. In this period, absorption coefficients were measured by the three-wavelength absorption photometer. The most frequent values of the extinction coefficient at 550 nm, the absorption coefficient at 530 nm, and the SSA at 550nm were 25 × 10-6, 3.0 × 10-6 m-1, and 0.905, respectively. The analysis using the extinction Ångström exponent showed that aerosol characteristics were dependent on the extinction Ångström exponent. The aerosol characteristics estimated from optical data were consistent with those derived from radiometer data. Therefore, ground-based monitoring of aerosol optical properties is useful for monitoring aerosol characteristics and interpreting variations in the surface radiation budget. © 2014, Meteorological Society of Japan.

Kobayashi E.,Aerological Observatory | Noto Y.,Aerological Observatory | Wakino S.,Aerological Observatory | Yoshii H.,Aerological Observatory | And 3 more authors.
Journal of the Meteorological Society of Japan | Year: 2012

Observation instruments are commonly upgraded because of technological advances and the convenience of the observation agency. However, great care is necessary when changing instruments to ensure data continuity for climatic data analysis. The Tateno upper-air observation station of the Japan Meteorological Agency replaced the Meisei RS2-91 type rawinsondes with Vaisala RS92-SGP type GPSsondes in December 2009. We carried out a total of 115 simultaneous dual launches for four seasons to investigate any differences in performance. The simultaneous sensor comparison results showed that Vaisala RS92-SGP temperature was 0.1-0.4K higher than Meisei RS2-91 temperature above the 100 hPa layer in night time observations; and that Meisei RS2-91 temperature was ~0.1K higher above the 30 hPa layer in day time observations. Vaisala RS92-SGP relative humidity was ~5% lower, particularly under humid conditions and in autumn. Vaisala RS92-SGP pressure was ~0.5 hPa higher in the stratosphere. We also made pressure-level comparisons for temperature and relative humidity. Furthermore, comparison results are shown for precipitable water vapor measurements taken with a collocated GPS receiver for a sensitivity analysis on the number of dual soundings and for a reanalysis of upper-air temperature trends for 1956-2010, taking the three instrumental change events into consideration. © 2012, Meteorological Society of Japan.

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