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首页> 外文期刊>Atmospheric chemistry and physics >Heterogeneous formation of polar stratospheric clouds – Part 1: Nucleation of nitric acid trihydrate (NAT)
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Heterogeneous formation of polar stratospheric clouds – Part 1: Nucleation of nitric acid trihydrate (NAT)

机译：极地平流层云的非均质形成-第1部分：三水合硝酸（NAT）的成核

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Satellite-based observations during the Arctic winter of 2009/2010 providefirm evidence that, in contrast to the current understanding, the nucleationof nitric acid trihydrate (NAT) in the polar stratosphere does not only occuron preexisting ice particles. In order to explain the NAT clouds observedover the Arctic in mid-December 2009, a heterogeneous nucleation mechanism isrequired, occurring via immersion freezing on the surface of solid particles,likely of meteoritic origin. For the first time, a detailed microphysicalmodelling of this NAT formation pathway has been carried out. HeterogeneousNAT formation was calculated along more than sixty thousand trajectories,ending at Cloud Aerosol Lidar with Orthogonal Polarization (CALIOP)observation points. Comparing the optical properties of the modelled NAT withthese observations enabled a thorough validation of a newly developed NATnucleation parameterisation, which has been built into the Zurich Optical andMicrophysical box Model (ZOMM). The parameterisation is based on active sitetheory, is simple to implement in models and provides substantial advantagesover previous approaches which involved a constant rate of NAT nucleation ina given volume of air. It is shown that the new method is capable ofreproducing observed polar stratospheric clouds (PSCs) very well, despite the varied conditionsexperienced by air parcels travelling along the different trajectories. In acompanion paper, ZOMM is applied to a later period of the winter, when icePSCs are also present, and it is shown that the observed PSCs are alsorepresented extremely well under these conditions.
机译：在2009/2010年北极冬季，基于卫星的观测提供了有力的证据，与目前的理解相反，极地平流层中硝酸三水合物（NAT）的核化不仅发生在先前存在的冰粒上。为了解释2009年12月中旬在北极上空观测到的NAT云，需要一种非均相成核机制，这种机制是通过浸没冻结在固体颗粒表面（可能是陨石起源）上发生的。第一次，已经对该NAT形成途径进行了详细的微物理建模。沿六万多条轨迹计算了异质NAT的形成，并以正交极化（CALIOP）观测点结束了Cloud Aerosol Lidar。将建模的NAT的光学特性与这些观察结果进行比较，可以对新开发的NAT成核参数化进行彻底的验证，该参数已内置在苏黎世光学和微物理盒模型（ZOMM）中。该参数化基于主动站点理论，在模型中易于实现，并且与以前的方法相比具有明显优势，后者涉及在给定的空气量下恒定的NAT成核速率。结果表明，新方法能够很好地重现观测到的极地平流层云（PSC），尽管沿不同轨迹行进的空气包裹所经历的条件不同。在伴侣纸中，ZOMM适用于冬天的后期，当还存在icePSC时，表明在这些条件下观察到的PSC也表现得非常好。

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