Papers in Meteorology and Geophysics
Online ISSN : 1880-6643
Print ISSN : 0031-126X
ISSN-L : 0031-126X
Volume 67
Showing 1-5 articles out of 5 articles from the selected issue
  • Tsuyoshi Fujieda
    2018 Volume 67 Pages 1-14
    Published: 2018
    Released: February 23, 2018

    It is important to evaluate precisely whether observational data that include screen-level air temperatures could be affected by the environment around meteorological surface observation stations. It is well known that atmospheric radiation (downward long-wave radiation) from the atmosphere and clouds affects the temperature of the ground as well as observational air temperature data, but there are few stations that observe atmospheric radiation. Therefore, various formulas have been proposed and developed to estimate the atmospheric radiation under clear sky conditions that use air temperature and water vapor pressure; these are used in earth surface models to estimate average hourly thermal energy budgets in the planetary boundary layer. It is necessary to verify whether the formulas are applicable for recent data in Japan, because these formulas were developed with data collected at local observation stations during specific periods.

     In this study, the accuracy of the familiar formulas used for estimation of diurnal atmospheric radiation under clear sky conditions was evaluated. Results from the formulas were compared with observational data from five stations, namely Sapporo, Tateno (Tsukuba), Fukuoka, Ishigaki Island, and Marcus Island, at which renovated solar and infrared radiation observations commenced on 31 March 2010. It was found that there were noticeable differences between observations and calculations as well as their seasonal variations. Therefore, the coefficients of Brutsaert (1975), which are comparatively theoretical, were adjusted to fit the regional meteorological conditions. The new Brutsaert-type formulas caused the differences and seasonal variations to disappear. Furthermore, in order to be applicable to various meteorological conditions including cloudy skies, the new formula for clear sky conditions was corrected by using sunshine duration and optical air mass. With these corrections, the average of differences between observations and calculations became close to zero.

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  • Kosuke Ito, Masahiro Sawada, Munehiko Yamaguchi
    2018 Volume 67 Pages 15-34
    Published: 2018
    Released: June 11, 2018
    This work quantified the skills of high-resolution regional nonhydrostatic models in forecasting tropical cyclones (TCs) in the Western North Pacific. The selected cases were almost all TCs during 2012–2014 with an initial time of 1200 UTC. The Japan Meteorological Agency (JMA)-nonhydrostatic model with a horizontal grid spacing of 5 km (NHM5km_atm) and its atmosphere-ocean coupled version (NHM5km_cpl) were used to conduct three-day forecasts. The JMA-global spectral model (GSM) outputs interpolated to a horizontal grid spacing of 0.5 degree were used for initial and lateral boundary conditions of the NHM5km_atm and NHM5km_cpl. The skills and GSM forecast skill were validated with respect to the Regional Specialized Meteorological Center Tokyo best track dataset. Results showed that use of the NHM5km_atm and NHM5km_cpl generally improved track forecasts at forecast times of 24–60 h. Track forecasts improved by as much as 20% for TCs with strong vertical shears of horizontal winds. However, a two-tailed test for the mean value revealed that the improvements were not statistically significant above the 90% confidence level. Use of the NHM5km_atm and NHM5km_cpl significantly improved TC intensity forecasts of 2–3 days by more than 20% with respect to the GSM, but strong TC intensities were not well predicted by short-term forecasts because of initialization deficiencies. Although the NHM5km_cpl tended to seriously underestimate TC intensities, it tended to produce the greatest increase in the correlation coefficient between observed and predicted intensity changes. This study also showed that the method used to determine the TC center position affects the track forecast error by up to a few percent and that the maximum wind speed forecast error depends on the best track dataset selected as a reference.
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  • Kazuhiro Kimura
    2018 Volume 67 Pages 35-44
    Published: 2018
    Released: July 27, 2018
    Crustal deformation data, such as volumetric strainmeter records, are often affected by rain. The correction by the precipitation data is effective about such data, and the quality of the precipitation data is important. Because many crustal deformation measurement sites do not include a local rain gauge, it is necessary to consider what kind of precipitation data should be brought to bear in such cases.
    Japan Meteorological Agency (JMA) observes precipitation data by the rain gauge in the volumetric strainmeter. In addition, JMA observes precipitation data by the rain gauge network of the Automated Meteorological Data Acquisition System (AMeDAS) consisting of station about 17km apart. And JMA makes the radar-raingauge analyzed precipitation data that combined the observation of the rain gauge with a radar. This paper reports on a comparison of corrections made by using these three precipitation data. Our results, confirm the importance of installing a rain gauge at strainmeter stations, and the effectiveness of the radar-raingauge analyzed precipitation. This result is important to the correction by the precipitation data of crustal deformation data from sites without a rain gauge.
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  • Yukitomo Tsutsumi
    2018 Volume 67 Pages 45-56
    Published: 2018
    Released: August 10, 2018
    Tropospheric ozone was continuously measured at the summit of Mt. Fuji (3776 m a.s.l.) for 6 years (1992–1998). Although mountain sites are usually influenced by mountain–valley winds, the small variance of the averaged diurnal ozone variation (0.77 ppbv) indicates that air at the summit of Mt. Fuji was hardly influenced by the boundary layer. Thus, the observations suggest some characteristic features of ozone in the middle troposphere over Japan. Annual variation at the summit was characterized by a bimodal seasonal cycle with maxima in May and October and minima in August and December. The summer minimum, which causes the seasonal cycle to be bimodal, resulted from summertime dominance of ozone-depleted maritime air at the summit. In June, however, air with a low water-vapor mixing ratio, high potential vorticity (PV), and enhanced ozone (>60 ppbv) was occasionally observed; these characteristics suggest that this air mass originated in the stratosphere or the upper troposphere. The small ozone variation during winter may be due to the suppression of its photochemical destruction and strong zonal winds, which cause the ozone distribution to be zonally homogeneous in the middle troposphere in winter. In addition, the infrequency of ozone intrusions from the stratosphere in winter may also contribute to the small wintertime variation. The annual course of daily mean ozone at the summit was synchronized with that of clear-sky solar radiation from late autumn to early spring, and both minima occurred in late December; this correspondence suggests that solar radiation controls observed ozone levels at the summit during this part of the year. In spring, daily mean ozone increased simultaneously with daily solar radiation, and the ozone concentration was not correlated with PV; this result suggests that the spring ozone maximum results mainly from photochemical ozone production. However, the possibility that indirect stratospheric ozone intrusions or aged stratospheric ozone contribute to the spring ozone maximum cannot be ruled out. The ozone concentration at the summit of Mt. Fuji increased during the 6-year observation period at the rate of 0.49 ppbv year–1, but the increasing trend was not significant at the 95% confidence level.
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  • Hidekazu Matsueda, Kazuhiro Tsuboi, Shinya Takatsuji, Teruo Kawasaki, ...
    2018 Volume 67 Pages 57-67
    Published: 2018
    Released: December 11, 2018

    A new calibration system of methane (CH4) standard gases by using a wavelength-scanned cavity ring-down spectroscopy (WS-CRDS) analyzer was developed at the Japan Meteorological Agency (JMA) in collaboration with the Meteorological Research Institute. We used two sets of CH4 primary standard gases with mole fractions assigned based on the World Meteorological Organization (WMO) CH4 mole fraction scale maintained by the National Oceanic and Atmospheric Administration to test the performance of the new WS-CRDS calibration system. Our results showed high repeatability (0.06 nmol mol−1) and reproducibility (0.07 nmol mol−1) of measurements and good linearity against the WMO CH4 mole fraction scale. The CH4 calibration results for the new system agree well with those of the previous JMA calibration system, which employed a gas chromatograph with a flame ionization detector (GC/FID). These tests indicate that the new WS-CRDS CH4 calibration system at JMA will provide results that are consistent with those of the previous GC/FID system but with precision that is one order of magnitude higher. We also evaluated the stability and consistency of the JMA calibrations over the past 10 years by examining data from the World Calibration Centre (WCC) Round Robin comparison experiments in Asia and the regions in the southwest Pacific. The results of our study clearly demonstrate that the new calibration system will provide more precise CH4 measurements and improved traceability to the WMO scale of atmospheric CH4 measurements for the JMA/WCC comparisons.

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