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首页> 外文期刊>Journal of the Atmospheric Sciences >Homogeneous ice nucleation in subtropical and tropical convection and its influence on cirrus anvil microphysics
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Homogeneous ice nucleation in subtropical and tropical convection and its influence on cirrus anvil microphysics

机译：亚热带和热带对流的均匀冰成核及其对卷云砧微观物理学的影响

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This study uses a unique set of microphysical measurements obtained in a vigorous, convective updraft core at temperatures between -33degrees and -36degreesC, together with a microphysical model, to investigate the role of homogeneous ice nucleation in deep tropical convection and how it influences the microphysical properties of the associated cirrus anvils. The core and anvil formed along a sea-breeze front during the Cirrus Regional Study of Tropical Anvils and Cirrus Layers-Florida Area Cirrus Experiment (CRYSTAL-FACE).The updraft core contained two distinct regions as traversed horizontally: the upwind portion of the core contained droplets of diameter 10-20 mum in concentrations of around 100 cm(-3) with updraft speeds of 5-10 m s(-1); the downwind portion of the core was glaciated with high concentrations of small ice particles and stronger updrafts of 10-20 m s(-1). Throughout the core, rimed particles up to 0.6-cm diameter were observed. The anvil contained high concentrations of both small particles and large aggregates.Thermodynamic analysis suggests that the air sampled in the updraft core was mixed with air from higher altitudes that descended along the upwind edge of the cloud in an evaporatively driven downdraft, introducing free-tropospheric cloud condensation nuclei into the updraft below the aircraft sampling height. Farther downwind in the glaciated portion of the core, the entrained air contained high concentrations of ice particles that inhibit droplet formation and homogeneous nucleation.Calculations of droplet and ice particle growth and homogeneous ice nucleation are used to investigate the influence of large ice particles lofted in updrafts from lower levels in this and previously studied tropical ice clouds on the homogeneous nucleation process. The preexisting large ice particles act to suppress homogeneous nucleation through competition via diffusional and accretional growth, mainly when the updrafts are < 5 m s(-1). In deep convective updrafts > 5-10 m s(-1), the anvil is the depository for the small, radiatively important ice particles (homogeneously nucleated) and the large ice particles from below (heterogeneously or secondarily produced, or recycled).
机译：这项研究使用了一组独特的微物理测量值，这些测量是在-33度至-36摄氏度之间的剧烈对流上升气流核心中获得的，并结合了一个微物理模型，以研究均质冰核在深热带对流中的作用及其对微物理的影响卷云砧的相关属性。在对热带砧和卷云的卷云区域研究-佛罗里达地区卷云实验（CRYSTAL-FACE）期间，沿海风锋形成的芯和砧沿上升气流的芯包含两个不同的水平横穿区域：芯的上风部分包含直径为10-20微米的液滴，浓度约为100 cm（-3），上升速度为5-10 ms（-1）;岩心的顺风部分被高浓度的小冰粒和10-20 m s（-1）的上升气流冰川化。在整个核中，观察到直径最大为0.6厘米的边缘颗粒。铁砧中含有高浓度的小颗粒和大聚集体。热力学分析表明，在上升气流核心中采样的空气与来自更高高度的空气混合，这些空气沿着云层的上风沿蒸发驱动的下降气流下降，从而引入了对流层云凝结核进入飞机采样高度以下的上升气流。在岩心冰川部分的下风处，夹带的空气中含有高浓度的冰粒，这些冰粒会抑制液滴的形成和均质成核。使用液滴和冰粒的生长以及均质的冰核化的计算方法来研究高空冰粒在高空飞散的影响。在本次和先前研究的热带冰云中，在均匀成核过程中从较低水平上升。预先存在的大冰粒主要通过上升气流<5 m s（-1）来通过扩散和增生增长的竞争来抑制均相成核。在深度大于5-10 m s（-1）的深对流上升气流中，砧座是小的，具有辐射重要性的冰粒（均相成核）和来自下方的大冰粒（异相或二次产生或循环利用）的沉积物。

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