Immersion mode heterogeneous ice nucleation by an illite rich powder representative of atmospheric mineral dust
Immersion mode heterogeneous ice nucleation by an illite rich powder representative of atmospheric mineral dust
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DOI：
10.5194/acp-12-287-2012
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发表时间：
2012-01-01
影响因子：
6.3
通讯作者：
Neve, L.
中科院分区：
文献类型：
--
作者：
Broadley, S. L.;Murray, B. J.;Neve, L.
富含伊利石的大气尘埃从干旱地区向全球输送，并通过冰的成核影响云的性质。我们提出了在大气相关条件下含有已知数量的富含伊利石粉末的水滴中的冰核测量。这里使用的富含伊利石的粉末，NX伊利石，与在偏远地区取样的大气矿物粉尘具有相似的矿物组成，即经受长途运输，云处理和沉积的粉尘。亚利桑那试验尘（Arizona Test Dust）是其他冰成核研究中使用的模型大气尘，其矿物组成明显不同，我们认为NX伊利石是天然大气尘的更好替代品。通过光学显微镜观察，NX伊利石在246K和均匀冻结极限之间主要发生非均相成核。一般来说，当液滴内存在较大表面积的NX伊利石时，观察到较高的冻结温度。在含有低表面积NX伊利石的液滴中观察到均匀成核。我们发现NX伊利石在冰成核能力方面表现出很强的颗粒到颗粒的变异性，当高表面积存在时，大约有1 / 10的颗粒主导冰成核。事实上，这项工作表明，大气中大部分矿物尘埃颗粒在形成冰核方面的效率可能比目前模型参数化所假设的要低。对于含有
Atmospheric dust rich in illite is transported globally from arid regions and impacts cloud properties through the nucleation of ice. We present measurements of ice nucleation in water droplets containing known quantities of an illite rich powder under atmospherically relevant conditions. The illite rich powder used here, NX illite, has a similar mineralogical composition to atmospheric mineral dust sampled in remote locations, i.e. dust which has been subject to long range transport, cloud processing and sedimentation. Arizona Test Dust, which is used in other ice nucleation studies as a model atmospheric dust, has a significantly different mineralogical composition and we suggest that NX illite is a better surrogate of natural atmospheric dust.Using optical microscopy, heterogeneous nucleation in the immersion mode by NX illite was observed to occur dominantly between 246K and the homogeneous freezing limit. In general, higher freezing temperatures were observed when larger surface areas of NX illite were present within the drops. Homogenous nucleation was observed to occur in droplets containing low surface areas of NX illite. We show that NX illite exhibits strong particle to particle variability in terms of ice nucleating ability, with similar to 1 in 10(5) particles dominating ice nucleation when high surface areas were present. In fact, this work suggests that the bulk of atmospheric mineral dust particles may be less efficient at nucleating ice than assumed in current model parameterisations.For droplets containing