North‐westerly airflow and associated atmospheric rivers (ARs) have been found to profoundly influence New Zealand’s west coasts, by causing flooding, landslides and extreme ablation and accumulation on glaciers in the Southern Alps. However, the response of local glacier mass balance to synoptic‐scale circulation, including events with ARs, has typically not been investigated by considering mesoscale processes explicitly. In this study, high‐resolution atmospheric simulations from the Weather Research and Forecasting model are used to investigate the mesoscale drivers of an extreme ablation event on Brewster Glacier (Southern Alps), which occurred on February 6, 2011 during the landfall of an AR on the South Island. The following processes were found to be crucial for transferring the high temperature and water vapor contained in the AR into energy available for melt on Brewster Glacier: First, the moist‐neutral character of the air mass enabled the flow to pass over the ridge, leading to the development of orographic clouds and precipitation on the windward side of the orography, and foehn winds on the leeside. These processes fueled melt through longwave radiation and strong turbulent and rain heat fluxes within the high‐condensation environment of the orographic cloud. Second, orographic enhancement occurred due to both cellular convection within the cloud and the combined effect of multiple precipitating systems by the seeder‐feeder‐mechanism. These results indicate the potential importance of AR dynamics for New Zealand’s glaciers. They also illustrate the benefit of mesoscale atmospheric modeling for advancing process understanding of the glacier‐climate relationship in New Zealand.

中文翻译：

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对新西兰南部阿尔卑斯山的大气河流事件及其对极端冰川融化的影响进行详细的多尺度评估

已发现西北气流和相关的大气河（AR）通过在南阿尔卑斯山的冰川上造成洪灾，山体滑坡以及极端消融和积聚，对新西兰的西海岸产生了深远的影响。然而，通常没有通过明确考虑中尺度过程来研究局部冰川质量平衡对天气尺度环流（包括AR事件）的响应。在这项研究中，使用了“天气研究和预测”模型中的高分辨率大气模拟来研究发生在2011年2月6日一次AR降落在布鲁斯特冰川（南阿尔卑斯山）上的一次极端烧蚀事件的中尺度驱动因素。南岛。已发现以下过程对于将AR中包含的高温和水蒸气转化为可用于Brewster Glacier融化的能量至关重要：首先，空气团的湿中性使气流能够通过山脊，导致地形上风向侧的地形云和降水的发展，背风侧有风。在地形云的高凝结环境中，这些过程通过长波辐射以及强烈的湍流和雨热通量促进了融化。其次，地形的增强是由于云内的细胞对流以及播种机-喂料机机制共同作用的多种降水系统的共同作用。这些结果表明AR动力学对于新西兰冰川的潜在重要性。