Improvements of the Double-Moment Bulk Cloud Microphysics Scheme in the Nonhydrostatic Icosahedral Atmospheric Model (NICAM)
Improvements of the Double-Moment Bulk Cloud Microphysics Scheme in the Nonhydrostatic Icosahedral Atmospheric Model (NICAM)
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DOI：
10.1175/jas-d-22-0049.1
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发表时间：
2023-01-01
影响因子：
3.1
通讯作者：
Ohno，Tomoki
中科院分区：
文献类型：
--
作者：
Seiki，Tatsuya;Ohno，Tomoki
本研究修正了非静水二十面体大气模型 (NICAM) 中实施的双矩块云微物理方案中的碰撞生长、异质冰成核和均质冰成核过程。修改后的云微物理过程通过10天的水平分辨率为14公里的全球模拟进行了测试。研究发现，目前的方案高估了较小直径云冰的聚集和雾化产生的霰石。一种对采集核进行数值积分的新方法解决了这个问题，从而参考卫星观测合理延长了云冰的寿命。此外，结果表明霰的减少调节了对流强度，特别是在强降雨系统中。异质和均质冰核的修正显着提高了云冰数浓度的产生率。通过这些修订，新版本的云微物理方案根据卫星观测成功改善了出射长波辐射，特别是在热带辐合带上。因此，这些修订既有利于长期气候模拟，也有利于代表强风暴的结构。意义声明已经开发了非常高分辨率的全球大气模型，以同时应对全球气候和区域天气。一般来说，此类全球模型中使用的云微物理方案是从区域天气预报模型中引入的，以真实地表示中尺度云系统。然而，最初为了天气预报而开发的云微物理方案可能会在全球气候模拟中造成意想不到的错误，因为这种云微物理方案并不是为跨时空尺度的跨学科使用而设计的。本研究重点关注评估冰云颗粒终端速度的系统模型偏差，并提出了一种准确计算冰云颗粒生长速率的方法。冰云模型的改进成功减少了全球能源预算中的模型偏差。此外，利用新的云模型对强降雨系统的内部结构进行了修改。因此，冰云模型的改进可以进一步提高天气预报、季节预测和气候预测的可靠性。
This study revises the collisional growth, heterogeneous ice nucleation, and homogeneous ice nucleation processes in a double-moment bulk cloud microphysics scheme implemented in the Nonhydrostatic Icosahedral Atmospheric Model (NICAM). The revised cloud microphysical processes are tested by 10-day global simulations with a horizontal resolution of 14 km. It is found that both the aggregation of cloud ice with smaller diameters and the graupel production by riming are overestimated in the current schemes. A new method that numerically integrates the collection kernel solves this issue, and consequently, the lifetime of cloud ice is reasonably extended in reference to satellite observations. In addition, the results indicate that a reduction in graupel modulates the convective intensity, particularly in intense rainfall systems. The revision of both heterogeneous and homogeneous ice nucleation significantly increases the production rate of cloud ice number concentration. With these revisions, the new version of the cloud microphysics scheme successfully improves outgoing longwave radiation, particularly over the intertropical convergence zone, in reference to satellite observations. Therefore, the revisions are beneficial for both long-term climate simulations and representing the structure of severe storms.Significance StatementVery high-resolution global atmospheric models have been developed to simultaneously address global climate and regional weather. In general, cloud microphysics schemes used in such global models are introduced from regional weather forecasting models to realistically represent mesoscale cloud systems. However, a cloud microphysics scheme that was originally developed with the aim of weather forecasting can cause unexpected errors in global climate simulations because such a cloud microphysics scheme is not designed for interdisciplinary usage across spatiotemporal scales. This study focuses on systematic model biases in evaluating the terminal velocity of ice cloud particles and proposes a method to accurately calculate the growth rate of ice cloud particles. Improvements in ice cloud modeling successfully reduce model biases in the global energy budget. In addition, the internal structure of intense rainfall systems is modified using the new cloud model. Therefore, improvements in ice cloud modeling could further increase the reliability of weather forecasting, seasonal prediction, and climate projection.