XRAINを用いたアンサンブル同化による線状降水帯の維持と発生の予測  [in Japanese] PREDICTION OF MATURE STAGE AND GENERATING STAGE OF A LINE-SHAPED RAINBAND BY ASSIMILATION OF XRAIN  [in Japanese]

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Abstract

メソ対流系の線状降水帯に対する数時間先の降水予測精度向上を目的にデータ同化実験を行った.データ同化システムはCReSS-LETKFを用いて,XRAINで観測されるドップラー風速,レーダー反射強度,および固体降水混合比をそれぞれ同化した.メソ対流系維持の予測を目的とした実験では,データ同化することで1時間先まで降水予測精度向上が見られ,固体降水を含めた全ての観測値を同化した実験が最も精度が高いことを示した.メソ対流系発生の予測を目的とした実験では,固体降水の同化による降水予測精度への効果はほとんどなかったが,気温低下を引き起こすという狙いを達成することができた.コンポジット解析により大気中下層における気温低下が本事例における発生要因であったことを確からしく示した.

 The short lead time rainfall prediction by Numerical Weather Prediction model has some difficulties in the spin-up problem. Therefore, data assimilation (DA) is expected to improve the initial condition in the model. In this study, our developed ensemble DA system, CReSS-LETKF, and the method of estimation of ice-water mixing ratios are employed. DA of rain, graupel, ice crystal, snowflake and Doppler velocity estimated by polarimetric Doppler radar are carried out after the first convective cloud in mesoscale convective systems is generated. As a result, the first convective clouds formed in initial condition have effective influence on the short lead time rainfall prediction. As the next challenging step, DA is carried out before the first convective cloud. As a result, convective clouds are not generated although the atmosphere conditions, such as potential temperature change.

Journal

  • Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering)

    Journal of Japan Society of Civil Engineers, Ser. B1 (Hydraulic Engineering) 73(4), I_211-I_216, 2017

    Japan Society of Civil Engineers

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