| 湿饱和流中的Richardson数和不稳定的研究 |
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| 引用本文： | 杨帅,高守亭,王东海.湿饱和流中的Richardson数和不稳定的研究[J].地球物理学报,2007,50(2):377-386. |
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| 作者姓名： | 杨帅 高守亭 王东海 |
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| 作者单位： | 1.中国科学院大气物理研究所，北京100029 2 中国科学院研究生院，北京100049 3 中国气象科学研究院，北京100081 |
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| 基金项目： | 国家自然科学基金重点项目(40433007,40633016)，国家自然科学基金项目(40405007)，中国科学院海外杰出学者基金(2004-2-7)资助 |
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| 摘 要： | 本文推导了干、湿饱和流中的Ri数方程.选取华北的一次降水过程，利用模式输出资料计算并对比分析干空气、湿饱和流中Ri方程中的各项，发现干过程中水平风速的垂直切变对干Ri数的变化和不稳定的影响占主导地位，而在湿过程中，湿饱和Ri的分子(Brunt_Vaisala frequency, 简称BVF)对Ri数的变化及不稳定的影响可达到与分母相当的量级. 既然BVF在湿过程中对不稳定有非常重要的影响，我们寻找了更符合湿过程中实际情况的BVF表达式，以对Ri进行修正，从而更好地判断湿过程的不稳定.研究发现，由于考虑了气块的虚温效应和总的水物质混合比的变化，即考虑降水过程中部分液态水脱离气块，有效地减小了雨区的稳定性，使得修正后的湿Ri公式可能更适合于诊断雨区的不稳定.
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| 关 键 词： | Richardson数 降水 不稳定 修正 Ri数方程 |
| 文章编号： | 0001-5733（2007）02-0377-10 |
| 收稿时间： | 2006-8-29 |
| 修稿时间： | 2006-08-29 |
A study of Richardson number and instability in moist saturated flow |
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| YANG Shuai,GAO Shou-Ting,WANG Dong-Hai.A study of Richardson number and instability in moist saturated flow[J].Chinese Journal of Geophysics,2007,50(2):377-386. |
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| Authors: | YANG Shuai GAO Shou-Ting WANG Dong-Hai |
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| Institution: | 1.Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China 2 Graduate University of Chinese Academy of Sciences, Beijing 100049, China 3 Chinese Academy of Meteorological Sciences, Beijing 100081, China |
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| Abstract: | We have derived the Ri equations in dry and moist saturated flow in the atmosphere. A rainfall case which occurred in Northern China is numerically simulated, and the model output data is used to calculate and analyze comparatively the terms of Ri equations in dry air and moist saturated flow. The analysis shows that the vertical shear of horizontal velocity dominates the influence on Ri change and instability in dry process, whereas in the moist case, the influence of numerator of Ri (i.e., Brunt-Vaisala frequency, named BVF) on Ri change and instability can reach up to the same magnitude order as the denominator of Ri. Since BVF has very important influence on instability in the moist case, we have looked for the expression of BVF which is more appropriate for the real moist case. Thus Ri is modified, so that we can estimate instability in the moist process. It is found that, due to considering the virtual temperature effect and the change of total water mixing ratio (i.e., part liquid water is dropped out the parcel), the stability in the rainy region is effectively decreased. Therefore, the modified moist Ri formula may be more appropriate to diagnose the instability in rainy regions. |
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| Keywords: | Richardson number Precipitation Instability Modification Ri equation |
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