著者

Hisaki EITO Teruyuki KATO Masanori YOSHIZAKI Ahoro ADACHI

出版者

Meteorological Society of Japan

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.83, no.4, pp.551-576, 2005 (Released:2005-10-07)

参考文献数

32

被引用文献数

23 25

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On 16 January 2001 during the field experiment named WMO-01, a meso-β-scale snowband extending eastward from Toyama Bay was observed in the coastal area of eastern Hokuriku district, middle part of Japan. This snowband stagnated for about half a day and brought a snowfall of about 50 cm in this region.Numerical simulations of this snowband are performed using a nonhydrostatic cloud resolving model (NHM), with a horizontal grid size of 1 km. The NHM well reproduces many characteristics of the observed snowband. The snowband forms over the convergence zone between a cold southerly land breeze and a northwesterly winter monsoon, to which heat and moisture is supplied from relatively warm sea surface. Convective snow cells with the horizontal scale of a few km successively form at the northern part of the snowband and propagate east-southeastward. Meso-γ-scale convective snow systems are organized, consisting of developed snow cells in the snowband. A cold pool forms under the snowband. The diabatic cooling due to the sublimation of snow is responsible for the formation of the cold pool. After the land breeze became weak, the cold pool contributes to the maintenance of the horizontal convergence with the northwesterly winter monsoon at the northern edge of the snowband by compensating for the weakened land breeze. Therefore, the formation of the cold pool is significant for the maintenance of thesnowband.

著者

Ahoro ADACHI Takahisa KOBAYASHI Hiroshi YAMAUCHI

出版者

(公社)日本気象学会

雑誌

気象集誌. 第2輯 (ISSN:00261165)

巻号頁・発行日

vol.93, no.3, pp.359-388, 2015 (Released:2015-07-10)

参考文献数

78

被引用文献数

1 7

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A method for estimating three parameters of a gamma raindrop size distribution (DSD) model and the rainfall rate from polarimetric radar at attenuating frequency was developed. The algorithm was developed based on the self-consistency principle but was expanded to consider the attenuation effect by describing the interrelation between polarimetric measurements along the range profile. The proposed method does not require any assumptions of relation among DSD parameters or simplifications of equations that describe the relation between the axis ratio and diameter of raindrops, which have been used in previous studies. Moreover, the proposed algorithm needs no external reference data such as two-dimensional video disdrometer measurements for attenuation corrections because it retrieves the co-polar and differential specific attenuation from the interrelation among the polarimetric measurements. The performance of this algorithm was evaluated by comparison with optical disdrometers and a weighing precipitation gauge. The evaluation of the algorithm showed that the retrieved three DSD parameters of raindrops, reflectivity, and differential reflectivity from actual C-band polarimetric radar data have fairly good agreement with those obtained by surface measurements. Moreover, rainfall rates retrieved using this algorithm have comparable precision with those estimated from the specific differential phase, and outperform those estimated through the so-called Z-R relation, particularly during heavy rainfall. Furthermore, the effects of raindrop temperature and shape parameter on the retrieval of the rainfall rate were examined. The results show that for radar operating at C-band, a raindrop temperature error of 10°C may be negligible in rainfall rate estimations, whereas a shape parameter error of 2 may increase the error of the rainfall rate estimation by 10 %.

著者

Takuya KAWABATA Hans-Stefan BAUER Thomas SCHWITALLA Volker WULFMEYER Ahoro ADACHI

出版者

Meteorological Society of Japan

雑誌

Journal of the Meteorological Society of Japan. Ser. II (ISSN:00261165)

巻号頁・発行日

pp.2018-017, (Released:2017-12-27)

被引用文献数

6

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In the preparation for polarimetric radar data assimilation, it is essential to examine the accuracy of forward operators based on different formulations. For this purpose, four forward operators that focus on warm rain condition are compared with both each other and actual observations with respect to their performance for C-band dual polarimetric radars. These operators mutually consider radar beam broadening and climatological beam bending. The first operator derives polarimetric parameters assuming an exponential raindrop size distribution obtained by the models and is based on fitting functions against scattering amplitudes. The other three converters estimate the mixing ratio of rainwater from the measured polarimetric parameters. The second converter uses both the horizontal reflectivity (ZH) and the differential reflectivity (ZDR), the third uses the specific differential phase (KDP), and the fourth uses both KDP and ZDP, respectively. Comparisons with modeled measurements show that the accuracy of the third converter is superior to the other two. Another evaluation with actual observations shows that the first converter has slightly higher fractions skill scores than the other three. Considering the attenuation effect, the fitting function and the operator only with KDP are found to be the most suitable for data assimilation at C-band.