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首页> 外文期刊>Quarterly Journal of the Royal Meteorological Society >Dynamical aspects of the life cycle of the winter storm 'Lothar' (24-26 December 1999)
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Dynamical aspects of the life cycle of the winter storm 'Lothar' (24-26 December 1999)

机译：冬季风暴“ Lothar”（1999年12月24日至26日）生命周期的动力学方面

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Dynamical aspects of the life cycle of the winter storm 'Lothar' (24-26 December 1999) are investigated with the aid of the European Centre for Medium-Range Weather Forecasts analysis data and mesoscale model simulations. Neither of these datasets capture the full amplitude of the observed extreme pressure fall and surface wind speeds, but they do help identify a range of key dynamical and physical features that characterize the development of this unusual event. The analysis and interpretation isprimarily based upon the evolution of the lower- and upper-level potential vorticity (PV) field complemented by three-dimensional trajectory calculations. 'Lothar' originated in the western Atlantic and travelled as a shallow low-level cyclone of moderate intensity towards Europe. This translation took place below and slightly to the south of a very intense upper-level jet and was accompanied by continuous and intense condensational heating that sustained a pronounced positive low-level PV anomaly (notunlike the concept of a 'diabatic Rossby wave'). No significant PV anomalies were evident at the tropopause level during this early phase of the life cycle. The surface cyclone intensified rapidly when the shallow cyclone approached the jet-stream axis.The circulation induced by the diabatically produced low-tropospheric PV anomaly on steeply sloping isentropic surfaces that transect the intense upper-level jet contributed significantly to the rapid formation of a narrow and deep tropopause fold. Thisstratospheric PV anomaly virtually merged with the diabatically produced ephemeral PV feature to form a vertically aligned tower of positive PV at the time of maximum storm intensity. A sensitivity study with a dry adiabatic hindcast simulation shows noPV-tower configuration (and only a very weak surface development) and confirms the primary importance of the cloud diabatic heating for the tropopause fold formation and the rapid 'bottom-up' intensification of 'Lothar' A comparison of the anomalously high Atlantic sea surface temperatures in December 1999 with the watervapour source regions for the latent-heat release that accompanied the rapid intensification phase of 'Lothar' shows a close relationship. This is of importance when discussing the possible implications of climate variability and change on the development of North Atlantic winter storms.
机译：欧洲中距离天气预报中心分析数据和中尺度模型模拟研究了冬季风暴“洛萨”（1999年12月24日至26日）生命周期的动力学方面。这些数据集都无法捕获观测到的极端压力下降和地表风速的全部幅度，但它们确实有助于确定表征此异常事件发展的一系列关键动力和物理特征。分析和解释主要基于上下轨迹势场（PV）场的演化，并辅以三维轨迹计算。 “ Lothar”起源于西大西洋，以中等强度的浅层低层旋风向欧洲传播。这种转换发生在一个非常强烈的高空急流的下方和南部，并伴有持续不断的强烈凝结加热，维持了明显的低空PV正异常（与“绝热Rossby波”的概念不同）。在生命周期的这个早期阶段，对流层顶水平上没有明显的PV异常。当浅层旋流器接近射流轴时，表面旋流器迅速增强。绝热产生的低对流层PV异常在陡峭的等熵表面上横切强烈的高空射流引起的环流显着地促进了狭窄旋流的快速形成。和深对流层褶皱。平流层PV异常实际上与绝热产生的短暂PV特征合并，在最大风暴强度时形成垂直排列的正PV塔。通过干绝热后验模拟进行的敏感性研究表明，没有PV塔结构（只有非常薄的表面发育），并且证实了云层绝热加热对于对流层顶褶皱形成和“ Lothar”快速“自下而上”增强的重要性'1999年12月大西洋海表温度异常高与潜伏释放的水蒸气源区域以及“洛萨尔”迅速强化阶段的比较显示出密切的关系。在讨论气候变化和变化对北大西洋冬季风暴发展的可能影响时，这一点很重要。

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