This study documents the presence of ice in stratocumulus clouds with cloud top temperatures (CTT) > −5 °C in the cold sector of extratropical cyclones over the Southern Ocean (SO) during ten SO Clouds, Radiation, Aerosol Transport Experimental Study (SOCRATES) research flights. Case studies are presented showing ice signatures within clouds when CTT were between −2 and −5°C, evidenced in Doppler radar radial velocity changes observed during high-altitude flight legs as ice particles melted across the 0°C isotherm. Ice on these legs was found to contribute to precipitation 3.8% of the time from clouds with −5°C < CTT <0°C. Clouds observed with a distinct melting level on high-altitude flight legs overall had greater cloud depths, tops with higher reflectivities, and higher linear depolarization ratios, compared to clouds without a melting level. In situ flight legs were also analyzed when Himawari-8 CTT were between 0 and −5°C and the aircraft was sampling in cloud within that temperature range. It was found that 3% of clouds sampled in situ with −5°C < CTT <0°C were mixed phase with a mean number concentration of 2.35 L⁻¹ for nonspherical particles with maximum diameters >100 μm and 1.13 L⁻¹ for nonspherical particles with maximum diameters >200 μm.

中文翻译：

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云顶温度超过−5°C 的南大洋云中的冰

本研究记录了在十次 SO 云、辐射、气溶胶传输实验研究 (SOCRATES) 期间，在南大洋 (SO) 上空温带气旋的冷区，云顶温度 (CTT) > -5 °C 的层积云中存在冰研究飞行。案例研究显示了当 CTT 在 -2 到 -5°C 之间时云中的冰特征，这在高空飞行航段期间观察到的多普勒雷达径向速度变化中得到证实，因为冰粒子在 0°C 等温线上融化。发现这些腿上的冰在 -5°C < CTT <0°C 的情况下导致 3.8% 的时间来自云的降水。在高空飞行腿上观察到的具有明显融化水平的云整体具有更大的云深、更高的反射率和更高的线性去极化率，与没有融化水平的云相比。当 Himawari-8 CTT 在 0 到 -5°C 之间并且飞机在该温度范围内的云中采样时，还分析了原位飞行航段。发现在-5°C < CTT <0°C的原位采样云中有3%是混合相，平均数浓度为2.35 L^-1对于最大直径 >100 μm的非球形颗粒和 1.13 L ^-1对于最大直径 >200 μm 的非球形颗粒。