Snow microphysical observations in shallow mixed‐phase and deep frontal Arctic cloud systems
Snow microphysical observations in shallow mixed‐phase and deep frontal Arctic cloud systems
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北极浅层混合相和深额锋云系统中的雪微物理观测
DOI：
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发表时间：
2011
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通讯作者：
A. Heymsfield
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作者：
Hugh Morrison;P. Zuidema;G. McFarquhar;Aaron R. Bansemer;A. Heymsfield
分析了在北极表面热收支/第一次ISCCP区域实验-北极云实验和混合相北极云实验期间使用现场飞机仪器测量的北极西部雪颗粒尺寸分布（颗粒尺寸>400 µm）。对三种浅的、沉淀的混合相边界层云和两种深的、沉淀的锋面云进行了研究。总的来说，浅的情况下，颗粒浓度和冰水含量的值比深的情况下，表明这些制度之间的冰的起始和生长的大的差异。在给定的情况下，无论是浅锋系统还是深锋系统，以及整个数据集，晶体浓度与温度（高度）几乎没有相关性，尽管在五种情况中的四种情况下观察到的大聚集体（>5 mm）表明了活跃的聚集过程。指数尺寸分布拟合的观测，允许直接比较与雪粒子的尺寸分布，表示在许多散装微物理方案中使用的天气和气候模式的指数函数。拟合截距参数N 0的值一般是2-10倍小的浅相比，深锋的情况下，由于这些制度之间的晶体浓度的差异。在许多体微物理方案中，雪的N 0 = 107 m−4的数值与深层情况下的拟合N 0大致一致，但大于浅层情况下的数值。深锋的情况下，也表现出N 0和温度之间的关系与以前的观测中纬度锋面系统。然而，当按冰水含量划分时，浅层和深层情况之间的N 0没有一致的差异。浅层和深层情况下斜率参数λ的拟合值与以前低纬度云系的研究基本一致。皇家气象学会
Snow particle size distributions (particle size >400 µm) in the western Arctic measured with in situ aircraft instrumentation during the Surface Heat Budget of the Arctic/First ISCCP Regional Experiment ‐ Arctic Clouds Experiment and Mixed‐Phase Arctic Cloud Experiment are analysed. Three cases of shallow, precipitating mixed‐phase boundary‐layer clouds and two cases of deep, precipitating frontal clouds are examined. Overall, the shallow cases had much lower values of particle concentration and ice water content than the deep cases, indicating large differences in ice initiation and growth between these regimes. Within a given case for both the shallow and deep frontal systems, and for the dataset as a whole, crystal concentration had little correlation with temperature (height), despite an active aggregation process that was indicated by large aggregates (>5 mm) observed in four out of the five cases. Exponential size distributions are fitted to the observations, allowing a direct comparison with the snow particle size distributions that are represented with exponential functions in many bulk microphysics schemes used in weather and climate models. Values of the fitted intercept parameter N0 are generally 2–10 times smaller for the shallow compared to the deep frontal cases as a result of differences in crystal concentration between these regimes. Values of N0 ∼ 107 m−4 specified for snow in many bulk microphysics schemes are broadly consistent with fitted N0 for the deep cases but larger than values for the shallow cases. The deep frontal cases also exhibit a relationship between N0 and temperature consistent with previous observations of midlatitude frontal systems. However, there are no consistent differences in N0 between the shallow and deep cases when partitioned by ice water content. Fitted values of slope parameter λ for the shallow and deep cases are generally consistent with previous studies of lower‐latitude cloud systems. Copyright © 2011 Royal Meteorological Society