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山东省三个不同区域降水雨滴谱特征的对比分析

Comparison study of raindrop size distribution in three regions of Shandong Province

  • 摘要: 为了解山东黄河三角洲、内陆和沿海三个区域降水的微物理特征差异,以垦利、平阴和胶南3站为代表,利用2017—2020年降水雨滴谱资料,对3站不同雨强(R)、不同降水类型的雨滴谱特征进行对比分析。结果表明:(1)在6个R级别中,3站平均雨滴谱的谱型、谱宽和各级别降水量对总降水量的贡献均存在一定区别。(2)在层云降水中,平阴站、胶南站雨滴谱参数较接近,而在对流云降水中3站均存在差异。(3)比较3站标椎化截距参数(log10Nw)和质量加权平均直径(Dm)表明,层云降水中垦利站log10Nw数值最低;与国内外其他站点相比,平阴站log10Nw-Dm散点分布与在韩国首尔的观测结果较为接近。(4) Gamma分布斜率参数(λ)和形状因子(μ)的拟合曲线具有局地性特征。根据3站μλR变化趋势,可将R=10 mm·h-1作为层云-对流云降水的分类指标,R增大至100 mm·h-1以上,3站μ值均趋向于1~2 mm-1λ值均趋向于2。(5)拟合雷达反射率因子(Z)与R关系(Z=ARb),气象业务雷达内置Z=300R1.4会高估垦利站、平阴站降水量,低估胶南站降水量,Z-R关系中系数A、指数b在对流云、层云降水中均有一定差异。

     

    Abstract: To study the microphysical characteristics of precipitation in different regions of Shandong province-the Yellow River Delta, inland region and coastal region, the raindrop spectrum data at three sites (Kenli, Pingyin, and Jiaonan) from 2017 to 2020 were used to compare the raindrop size distribution (DSD) characteristics of different rain rates (R) and rainfall types (stratiform and convective rainfall). The results are as follows. (1) In 6 rain rate levels at 3 sites, there were certain degree of differences in the DSD spectral, the spectra width of mean DSD, and the contribution of different precipitation levels to the total precipitation amount. (2) In stratiform precipitation, the average DSD characteristics of Pingyin and Jiaonan were comparable to each other, but differences were found in convective precipitation at these 3 sites. (3) The distribution of the normalized Gamma spectral intercept parameter (log10Nw) and the mass-weighted average diameter (Dm) showed that, log10Nw of Kenli station was the lowest during stratiform precipitation. While the comparison with other national and international stations demonstrated that the distribution of log10Nw versus Dm from Pingin agreed with the observations in Seoul, Korea. (4) The fitting curves of the shape parameter (μ) and slope parameter (λ) from the Gamma distribution exhibited localized characteristics. According to the trend of μ and λ with R at all 3 sites, R=10 mm·h-1 can be used as a criterion for precipitation classification. At all three sites, when R increased greater than 100 mm·h-1, the values of μ remained nearly constant towards 1~2, while the values of λ tend to 2. (5) The fitting results between the reflectivity factor (Z) and R (Z=ARb) at 3 sites indicated that, the typical Z-R fitting formula (Z=300R1.40) for weather radars overestimated the precipitation of Kenli and underestimated the precipitation of Jiaonan. The values of A and b in the Z-R fitting formula also exhibited differences between convective and stratiform precipitation.

     

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