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以1981年12月3日至12日,北上影响青藏高原东部地区降水的孟加拉湾热带气旋为个例,收集了尽量多的有关观测资料,用有限元法对其动力学特征和能量学特征量进行了计算和分析。研究结果表明:孟加拉湾热带气旋(简称气旋)风速分布不对称,风速的垂直切变随气旋加强而减弱,东风大值区是随气旋的发展由中层逐渐向低层下传,气旋有暖心结构,这些特征亦与西北太平洋上的热带气旋相似。气旋登陆后,受东面阿拉干山和那加山的直接作用,以及北面青藏高原的屏障作用,东风和北风减弱,分布范围缩小,西风及南风则迅速加强,范围扩大,气旋性环流以上全部为西至西南风。最强流入出现在南半圆的250hPa附近,最强流出在北半圆的300hPa附近。气旋的南半部中上层为深厚的水汽辐合层,水汽辐合最大值出现在南半圆的500hPa层附近,导致青藏高原东部出现有史以来的最强降雨过程。这些特征与西太平洋上的热带气旋不相同。垂直运动和气旋的发展与受青藏高原地形的影响有密切关系。
Taking the northward tropical cyclone over the Bay of Bengal which affected the precipitation in the eastern Qinghai-Tibetan Plateau from December 3 to December 12, 1981 as an example, we collected as much as possible of the observed data, and used the finite element method to study its kinetic and energy characteristics The calculation and analysis. The results show that the distribution of the tropical cyclones in the Bay of Bengal is asymmetric, the vertical shear of the wind speed is weakened with the enhancement of the cyclone, and the large area of the east wind is gradually transferred from the middle layer to the lower layer with the development of cyclones. The cyclone has a warm heart structure, These features are also similar to tropical cyclones over the western North Pacific. After the cyclone landed, due to the direct action of the eastern Aracan and Najag mountains and the barrier function of the Qinghai-Xizang Plateau in the north, the easterly and northerly winds weakened and the distribution range narrowed down. The westerly and southerly winds rapidly strengthened and the scope expanded. Cyclonic circulation above All west to southwest wind. The strongest influx appeared in the southern semicircle near 250hPa, the strongest outflow in the northern semicircle near 300hPa. The mid-upper half of the cyclone is a deep water-vapor convergence layer. The maximum of water-vapor convergence appears in the southern semicircle near the 500hPa layer, resulting in the strongest rainfall ever recorded in the eastern part of the Qinghai-Tibet Plateau. These features are not the same as tropical cyclones in the western Pacific. Vertical movement and cyclone development are closely related to the influence of the topography of the Tibetan Plateau.