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“5.10”岷县暴雨灾害天气过程的数值模拟和诊断分析 总被引：2，自引：0，他引：2
利用NCEP再分析资料和中尺度模式WRF,对2012年5月10日甘肃岷县出现的罕见雷电、短时强降水、冰雹和阵性大风等强对流天气过程进行了模拟,同时使用H YSPLIT后向轨迹模式对此次天气过程的水汽来源进行了模拟,并对模式输出的多种物理量进行了诊断分析.结果表明,WRF模式能较好地模拟此次天气过程;在此次降水发生过程中,暴雨区出现了很强的辐合上升运动,为降水的形成和发展提供了动力条件,中低层负螺旋度的短暂出现可作为降水即将发生的一个指标;来自西亚地区和孟加拉湾的水汽在甘南中层辐合,为此次暴雨提供了足够的水汽;不稳定能量的积累和释放,且能量的释放过程比积累过程快,导致暴雨的产生. 相似文献
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利用Micaps高空、地面实况资料以及雷达基数据产品资料,分析2004—2009年湖北宜昌境内出现的10例强对流天气过程中的超级单体风暴生成的环境条件和回波结构。结果表明:产生冰雹的湿层相对浅薄,产生强降水的湿层较深厚。使用雷暴发生前地面温度和露点进行订正后的CAPE值可判断午后是否有冰雹发生:若订正后CAPE值有较大幅度增长,其值超过1000J.kg-1以上,则出现冰雹的可能性较大;反之则小。0—6km中等到强的垂直风切变有利超级单体风暴生成和发展,垂直风切变越大,越有利出现极端大风。若超级单体风暴高度的特征值和特征底有迅速下降迹象,则未来0.5h内很可能出现8级以上大风。超级单体风暴中正负速度对的切变值越大,风力越大,风灾越明显。超级单体风暴反射率因子的低层或表现为钩状、或向着入流方向突起、或密实块状等回波特征,中高层有强度达55dBz的强回波。超级单体风暴中,中气旋大多从逆风区或切变区中发展而来,且其在垂直气流结构上表现为低层气旋式辐合,中层辐合逐渐增强,为气旋式旋转,有时出现气旋式旋转与反气旋式旋转共存的双涡结构,至高层,则转为反气旋,表现为辐散。VIL密度(DVIL)对大冰雹有一定的指示意义,当DVIL≥3.5g.m-3时,出现直径超过2cm的大冰雹的可能性非常大。 相似文献
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Surface turbulent flux measurements over the Loess Plateau for a semi-arid climate change study 总被引：2，自引：0，他引：2
In order to provide high quality data for climate change studies, the data quality of turbulent flux measurements at the station
of SACOL (Semi-Arid Climate & Environment Observatory of Lanzhou University), which is located on a semi-arid grassland over
the Loess Plateau in China, has been analyzed in detail. The effects of different procedures of the flux corrections on CO2, momentum, and latent and sensible heat fluxes were assessed. The result showed that coordinate rotation has a great influence
on the momentum flux but little on scalar fluxes. For coordinate rotation using the planar fit method, different regression
planes should be determined for different wind direction sectors due to the heterogeneous nature of the ground surface. Sonic
temperature correction decreased the sensible heat flux by about 9%, while WPL correction (correction for density fluctuations)
increased the latent heat flux by about 10%. WPL correction is also particularly important for CO2 fluxes. Other procedures of flux corrections, such as the time delay correction and frequency response correction, do not
significantly influence the turbulent fluxes. Furthermore, quality tests on stationarity and turbulence development conditions
were discussed. Parameterizations of integral turbulent characteristics (ITC) were tested and a specific parameterization
scheme was provided for SACOL. The ITC test on turbulence development conditions was suggested to be applied only for the
vertical velocity. The combined results of the quality tests showed that about 62%–65% of the total data were of high quality
for the latent heat flux and CO2 flux, and as much as about 76% for the sensible heat flux. For the momentum flux, however, only about 35% of the data were
of high quality. 相似文献
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