Effects of modifications to the Zhang-McFarlane convection parameterization on the simulation of the tropical precipitation in the National Center for Atmospheric Research Community Climate Model, version 3
Effects of modifications to the Zhang-McFarlane convection parameterization on the simulation of the tropical precipitation in the National Center for Atmospheric Research Community Climate Model, version 3
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DOI：
10.1029/2004jd005617
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发表时间：
2005-05
影响因子：
--
通讯作者：
G. Zhang;M. Mu
中科院分区：
文献类型：
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作者：
G. Zhang;M. Mu
[1] 本研究比较了国家大气研究中心社区气候模型第 3 版 (CCM3) 中热带对流的模拟，使用了张-麦克法兰方案中的原始和修订后的对流参数化闭合。修改后的闭合将对流与自由对流层中的大规模强迫耦合，而不是像原始闭合中所使用的那样与大气中的对流可用势能耦合。此外，相对湿度阈值用于对流触发。结果表明，使用新的关闭措施后，热带地区夏季和冬季的平均降水分布总体上得到了改善。 6、7、8月西太平洋季风区降水显着增强，缓解了模型中降水负偏差。阿拉伯半岛沙漠虚假降水彻底消除。十二月、一月和二月期间，南太平洋辐合区显着增强。所有这些变化对于解决重要的模型缺陷都是可取的。将模型模拟的降水强度概率分布与热带降雨测量任务（TRMM）数据的降水强度概率分布进行比较。结果表明，超过 90% 的 CCM3 降水来自降雨率小于 1 mm h−1 的小雨，而新闭合的模拟和 TRMM 观测显示，降雨率大于 2 mm h−1 的贡献显着（30-40%）。对北太平洋西部夏季风区和阿拉伯半岛的降水模拟进行了详细研究，以了解 CCM3 在这些地区降水偏差的原因。结果表明，基于对流可用势能（CAPE）的闭合限制了季风季节开始时CAPE的积累，导致对西北太平洋季风降水的模拟不足。在阿拉伯半岛，对流和地表蒸发之间的正反馈导致了那里的虚假强降水中心。除了新的闭合之外，还发现相对湿度阈值的使用对于模拟的改进也很重要。
[1] This study compares the simulation of tropical convection in the National Center for Atmospheric Research Community Climate Model, version 3 (CCM3), using the original and a revised convective parameterization closure in the Zhang-McFarlane scheme. The revised closure couples convection to the large-scale forcing in the free troposphere instead of to the convective available potential energy in the atmosphere as employed in the original closure. In addition, a relative humidity threshold is used for convection trigger. It is shown that the mean precipitation distribution in the tropical regions for both summer and winter is, in general, improved when the new closure is used. During June, July, and August the precipitation in the western Pacific monsoon region is significantly enhanced, alleviating the negative precipitation bias there in the model. The spurious precipitation in the Arabian Peninsula desert is completely eliminated. During December, January, and February the South Pacific Convergence Zone is enhanced considerably. All these changes are desirable in addressing important model deficiencies. The probability distributions of the precipitation intensity from the model simulations are compared with that from the Tropical Rainfall Measurement Mission (TRMM) data. It is shown that over 90% of the CCM3 precipitation is from light rain with rainfall rate less than 1 mm h−1, whereas the simulation with the new closure and the TRMM observations show significant contribution (30–40%) from rainfall rates greater than 2 mm h−1. Precipitation simulation over the western North Pacific summer monsoon region and the Arabian Peninsula was examined in detail to understand the causes of the precipitation biases in CCM3 over these regions. It is demonstrated that the convective available potential energy (CAPE)-based closure limits the CAPE buildup at the beginning of the monsoon season, resulting in the under simulation of the western North Pacific monsoon precipitation. In the Arabian Peninsula the positive feedback between convection and surface evaporation leads to the spurious heavy precipitation center there. In addition to the new closure the use of relative humidity threshold is also found to be important to the improvement of the simulation.