The Impact of Topography on the Environment and Life Cycle of Weakly and Strongly Forced MCSs during RELAMPAGO
The Impact of Topography on the Environment and Life Cycle of Weakly and Strongly Forced MCSs during RELAMPAGO
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DOI：
10.1175/mwr-d-22-0049.1
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发表时间：
2022-09
影响因子：
3.2
通讯作者：
Marquette N. Rocque;K. Rasmussen
中科院分区：
文献类型：
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作者：
Marquette N. Rocque;K. Rasmussen
强烈的深对流和大的中尺度对流系统（MCS）发生在南美洲亚热带地区的安第斯山脉下游。深层对流通常在下午沿着科尔多瓦山脉（SDC）沿着聚集，然后迅速发展壮大，并在夜间向东移动。然而，如何安第斯山脉和SDC的影响，在不同的天气条件下MCS的生命周期还没有得到很好的理解。利用WRF进行了两组地形改造试验，研究了不同天气体制下地形的影响。第一组是在2018年12月13日至14日来自RELAMPAGO的MCS案例中运行的，其中包括深天气槽，SDC附近的强背风气旋，增强的低空急流以及MCS的快速高增长。当安第斯山脉减小50%时，发展的背风气旋和低空急流比完全安第斯山脉时弱，由此产生的MCS也较弱，且向东移动较快。当SDC被移除时，可以看到环境和所产生的MCS相对于对照运行之间的差异很小。第二组实验是在2019年1月25日至26日的情况下进行的，其中一个大型MCS在SDC上发展，并在弱天气强迫下长时间保持联系。产生与对照最相似的MCS的实验是当安第斯山脉减少50%时，同时保持SDC的高度，这表明SDC可能在静止天气条件下的MCS生命周期中发挥更重要的作用。
Intense deep convection and large mesoscale convective systems (MCSs) are known to occur downstream of the Andes in subtropical South America. Deep convection is often focused along the Sierras de Córdoba (SDC) in the afternoon and then rapidly grows upscale and moves to the east overnight. However, how the Andes and SDC impact the life cycle of MCSs under varying synoptic conditions is not well understood. Two sets of terrain-modification experiments using WRF are used to investigate the impact of topography in different synoptic regimes. The first set is run on the 13–14 December 2018 MCS case from RELAMPAGO, which featured a deep synoptic trough, strong lee cyclogenesis near the SDC, an enhanced low-level jet, and rapid upscale growth of an MCS. When the Andes are reduced by 50%, the lee cyclone and low-level jet that develop are weaker than with the full Andes, and the resulting MCS is weak and moves faster to the east. When the SDC are removed, few differences between the environment and resulting MCS relative to the control run are seen. A second set of experiments are run on the 25–26 January 2019 case in which a large MCS developed over the SDC and remained tied there for an extended period under weak synoptic forcing. The experiment that produces the most similar MCS to the control is when the Andes are reduced by 50% while maintaining the height of the SDC, suggesting the SDC may play a more important role in the MCS life cycle under quiescent synoptic conditions.