Synoptic Features and Vertical Structures of Shear Lines Influencing Shandong Province
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Abstract:
By means of the conventional weather charts and NCEP/NCAR 1°×1° reanalysis data， analyses are made of the climatic features, circulation patterns, rainfall distributions, and spatial structures of typical shear lines in Shandong Province. The results show that shear lines can be divided into cold and warm ones according to their thermodynamic properties. Cold shear lines can be divided into meridional and zonal ones according to the wind field structure. Shear lines appear frequently in July and August in a year. The occurrence of typical shear lines is closely related to the Subtropical High during rainy season. The occurrence of a meridional shear line is often accompanied by the stronger cell shaped Subtropical High when the eastward trough is blocked, and zonal one by the band shaped one, while westerly troughs are transformed into shear lines. Shear lines are associated with the positive vorticity column in profile, and the strongest vorticity is often found on shear lines. There are θse energy frontal zones on shear lines, with the cold shear lines tending toward the warm side and the warm lines in the middle. The ascending motion areas locate on shear lines and the warm side. For cold shear lines, the convergence of water vapor locates on a shear line and the cold air side, but the occurrence of water vapor convergence is mainly on a shear line for warm shear lines. The rainfall area lies in the northerly flow in the rear of the ground stationary front for cold shear lines, but lies in the easterly flow of the ground inverted trough for warm shear lines, both with a trough in the 500 hPa layer as the border. Relatively large precipitation occurs in the area between the ground projections of the shear line in the layer of 700 to 850 hPa. The shear line warm air mass or relatively warm air mass may also bring the dispersive short duration precipitation in appropriate triggering conditions.
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Supported by:Beijing E-Tiller Technology Development Co., Ltd.
Supported by:Beijing E-Tiller Technology Development Co., Ltd.