The evolution of microphysical and optical properties of an A380 contrail in the vortex phase
The evolution of microphysical and optical properties of an A380 contrail in the vortex phase
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DOI：
10.5194/acp-12-6629-2012
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发表时间：
2011-09
影响因子：
6.3
通讯作者：
J. Gayet;V. Shcherbakov;C. Voigt;U. Schumann;D. Schäuble;P. Jeßberger;A. Petzold;A. Minikin;H. Schlager;O. Dubovik;T. Lapyonok
中科院分区：
文献类型：
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作者：
J. Gayet;V. Shcherbakov;C. Voigt;U. Schumann;D. Schäuble;P. Jeßberger;A. Petzold;A. Minikin;H. Schlager;O. Dubovik;T. Lapyonok
用德国航空航天研究飞机Fal-con上的现场仪器探测了一架A380大机身飞机在对流层上部湿区巡航时的尾迹，在700 s的测量时间内采集了尾迹样本，其尾迹年龄约为1- 10 m。尾迹处于涡流状态，在此期间，主尾涡下沉到A380飞行高度以下270 m处，而次尾涡下沉到A380飞行高度以下270 m处。Wake仍然在上面。在90 s和115 s尾迹龄的主尾迹中分别取样，在70 s至220 s尾迹龄的次尾迹中几乎连续取样。用极性散射比浊计测量了尾迹粒子的散射相函数。从这些数据导出的不对称参数用于区分准球形和球形冰粒。在初级尾流中，发现准球形冰粒，浓度高达160 cm 3，平均有效直径Deff为3.7 µm，最大消光为7.0 km 1，在轻微冰欠饱和条件下的冰水含量（IWC）为3 mg m 3。二次和一次玛丽被一个几乎无颗粒的尾涡间隙隔开。在明显高于冰饱和度的条件下，次级尾流含有明显的非球形尾迹冰粒，平均Deff为4.8 µm，平均（最大）浓度、消光和IWC分别为80（350）cm 3、1.6（5.0）km 1和2.5（10）mg m 3。二次尾迹的非对称性参数随尾迹年龄的增加而减小，平均值从0.87减小到0.80，表明二次尾迹中的非球形冰晶优先生长。用反演程序反演冰粒的习性和大小表明，非球形冰晶的数量分数从最初的2%增加到4 min轨迹年龄时的56%。观测到的晶体大小和习性的差异，在初级和次级尾流的长达4分钟的老轨迹是感兴趣的了解冰晶生长的轨迹和它们的气候影响。非球形轨道冰粒比球形轨道冰粒引起的辐射强迫小.
A contrail from a large-body A380 aircraft at cruise in the humid upper troposphere has been probed with in-situ instruments onboard the DLR research aircraft Fal- con. The contrail was sampled during 700 s measurement time at contrail ages of about 1-4 min. The contrail was in the vortex regime during which the primary wake vortices were sinking 270 m below the A380 flight level while the secondary wake remained above. Contrail properties were sampled separately in the primary wake at 90 and 115 s con- trail age and nearly continously in the secondary wake at contrail ages from 70 s to 220 s. The scattering phase func- tions of the contrail particles were measured with a polar nephelometer. The asymmetry parameter derived from these data is used to distinguish between quasi-spherical and as- pherical ice particles. In the primary wake, quasi-spherical ice particles were found with concentrations up to 160 cm 3 , mean effective diameter Deff of 3.7 µm, maximum extinction of 7.0 km 1 , and ice water content (IWC) of 3 mg m 3 at slightly ice-subsaturated conditions. The secondary and pri- mary wakes were separated by an almost particle-free wake vortex gap. The secondary wake contained clearly aspherical contrail ice particles with mean Deff of 4.8 µm, mean (maxi- mum) concentration, extinction, and IWC of 80 (350) cm 3 , 1.6 (5.0) km 1 , and 2.5 (10) mg m 3 , respectively, at condi- tions apparently above ice-saturation. The asymmetry pa- rameter in the secondary wake decreased with contrail age from 0.87 to 0.80 on average indicating a preferential aspher- ical ice crystal growth. A retrieval of ice particle habit and size with an inversion code shows that the number fraction of aspherical ice crystals increased from 2 % initially to 56 % at 4 min contrail age. The observed crystal size and habit dif- ferences in the primary and secondary wakes of an up to 4 min old contrail are of interest for understanding ice crystal growth in contrails and their climate impact. Aspherical con- trail ice particles cause less radiative forcing than spherical ones.