Interannual variability of Greenland winter precipitation sources: Lagrangian moisture diagnostic and North Atlantic Oscillation influence
Interannual variability of Greenland winter precipitation sources: Lagrangian moisture diagnostic and North Atlantic Oscillation influence
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DOI：
10.1029/2007jd008503
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发表时间：
2008-02-12
影响因子：
4.4
通讯作者：
Wernli, H.
中科院分区：
文献类型：
--
作者：
Sodemann, H.;Schwierz, C.;Wernli, H.
我们提出了一个新的拉格朗日诊断识别降水的水汽来源。与以往的研究不同，该方法允许蒸发水分来源的定量划分。这是通过考虑到在输送过程中进入空气团的蒸发和从空气团中降水的时间顺序以及关于其接近边界层的信息来实现的。使用欧洲中期天气预报中心的ERA-40再分析数据，采用水分源区诊断方法，追踪格陵兰冰盖冬季降水的水蒸气来源，选择30个月，采用明显的正、负和中性北大西洋涛动（NAO）指数。北大西洋和北欧海被证明是格陵兰岛最主要的水汽来源。在北大西洋海盆确定的水分来源的位置强烈变化与NAO阶段。更具体地说，该方法诊断的转变，从冰岛北部的来源在NAO积极的几个月在北大西洋东南部的NAO负的几个月，定性一致的变化，在并发的大规模平均流量。在北大西洋涛动的负相期间，发现了更长距离的水汽输送，导致水汽从更偏南的位置平流输送。格陵兰冰盖的不同地区经历了不同的变化，在平均水分来源的位置;变化最大的是在格陵兰岛的北部和西部。格陵兰冬季降水与NAO的强水分源的变化在这里发现可以有很大的影响格陵兰降水的稳定同位素组成，因此可以是重要的稳定同位素数据从冰芯的解释。在一个配套文件中，本研究结果的影响，进一步探讨在这方面。
We present a new Lagrangian diagnostic for identifying the sources of water vapor for precipitation. Unlike previous studies, the method allows for a quantitative demarcation of evaporative moisture sources. This is achieved by taking into account the temporal sequence of evaporation into and precipitation from an air parcel during transport, as well as information on its proximity to the boundary layer. The moisture source region diagnostic was applied to trace the origin of water vapor for winter precipitation over the Greenland ice sheet for 30 selected months with pronounced positive, negative, and neutral North Atlantic Oscillation (NAO) index, using the European Centre for Medium-Range Weather Forecasts' ERA-40 reanalysis data. The North Atlantic and the Nordic seas proved to be the by far dominant moisture sources for Greenland. The location of the identified moisture sources in the North Atlantic basin strongly varied with the NAO phase. More specifically, the method diagnosed a shift from sources north of Iceland during NAO positive months to a maximum in the southeastern North Atlantic for NAO negative months, qualitatively consistent with changes in the concurrent large-scale mean flow. More long-range moisture transport was identified during the NAO negative phase, leading to the advection of moisture from more southerly locations. Different regions of the Greenland ice sheet experience differing changes in the average moisture source locations; variability was largest in the north and west of Greenland. The strong moisture source variability for Greenland winter precipitation with the NAO found here can have a large impact on the stable isotope composition of Greenland precipitation and hence can be important for the interpretation of stable isotope data from ice cores. In a companion paper, the implications of the present results are further explored in that respect.