Effects of Thermodynamics, Dynamics and Aerosols on Cirrus Clouds Based on In Situ Observations and NCAR CAM6 Model
Effects of Thermodynamics, Dynamics and Aerosols on Cirrus Clouds Based on In Situ Observations and NCAR CAM6 Model
复制标题
DOI：
10.5194/acp-2020-497
复制
发表时间：
2020-07
期刊：
影响因子：
--
通讯作者：
Ryan Patnaude;M. Diao;Xiaohong Liu;Suqian Chu
中科院分区：
文献类型：
--
作者：
Ryan Patnaude;M. Diao;Xiaohong Liu;Suqian Chu
抽象的。卷云的辐射效应主要受冰的微物理性质的影响，包括冰的含水量（IWC），冰晶数浓度（Ni）和平均直径（Di）。这些特性由于热力学、动力学和气溶胶条件而显著变化。在这项工作中，全球尺度的观测数据集被用来检查卷云微物理特性的区域变化，以及几个关键的控制因素，即，温度、相对于冰的相对湿度（RHi）、垂直速度（w）和气溶胶数浓度（Na）。结果进行了比较，从美国国家大气研究中心（NCAR）社区大气模型版本6（CAM 6）的模拟。模拟和观测之间的差异被发现随纬度和温度而变化。具体而言，模拟被发现低估了IWC的5-30倍，在所有地区。除北方半球、中纬度和极地外，模拟的Ni值在大多数地区都被高估了。模拟的Di被低估了，特别是在较温暖的条件下（−50 °C至−40 °C）和较高的Na，可能分别是由于冰颗粒生长/沉降的有效性较低和气溶胶间接效应较弱。对于RHi效应，在晴空条件下的模拟中，冰过饱和的频率和幅度被低估，并且模拟的IWC和Ni在80%RHi而不是观察到的110%处显示最大值。对于w的影响，观测和模拟结果都表明w（σw）的方差从热带到极地逐渐减小，但模拟结果表明，云内条件下的σw远高于晴空条件下的σw。这些研究结果提供了一个基于观测的指导方针，以改善模拟冰微物理特性及其与关键控制因素在不同的地理位置的关系。
Abstract. Cirrus cloud radiative effects are largely affected by ice microphysical properties, including ice water content (IWC), ice crystal number concentration (Ni) and mean diameter (Di). These characteristics vary significantly due to thermodynamic, dynamical and aerosol conditions. In this work, a global-scale observation dataset is used to examine regional variations of cirrus cloud microphysical properties, as well as several key controlling factors, i.e., temperature, relative humidity with respect to ice (RHi), vertical velocity (w), and aerosol number concentrations (Na). Results are compared with simulations from the National Center for Atmospheric Research (NCAR) Community Atmosphere Model version 6 (CAM6). The differences between simulations and observations are found to vary with latitude and temperature. Specifically, simulations are found to underestimate IWC by a factor of 5–30 in all regions. Simulated Ni is overestimated in most regions except Northern Hemisphere midlatitude and polar regions. Simulated Di is underestimated, especially for warmer conditions (−50 °C to −40 °C) and higher Na, possibly due to less effective ice particle growth/sedimentation and weaker aerosol indirect effects, respectively. For RHi effects, the frequency and magnitude of ice supersaturation is underestimated in simulations for clear-sky conditions, and the simulated IWC and Ni show maximum values at 80 % RHi instead of 110 % as observed. For w effects, both observations and simulations show variances of w (σw) decreasing from tropics to polar regions, but simulations show much higher σw for in-cloud condition than clear-sky condition. These findings provide an observation-based guideline for improving simulated ice microphysical properties and their relationships with key controlling factors at various geographical locations.