提高模式分辨率后热带气旋生成迟缓的原因分析
投稿时间: 2017-06-15  最后修改时间: 2017-09-27  点此下载全文
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作者单位E-mail
赵静娴 南京信息工程大学 1003635781@qq.com 
基金项目:国家自然科学基金资助项目(41675051)
中文摘要:用目前国际上最先进的中尺度WRF模式模拟热带气旋生成,网格分辨率从9km增加到3km,3km网格中积云参数化方案不起作用,依靠微物理方案来模拟对流尺度系统特征,模式中热带气旋的生成过程变得迟缓。当低压扰动发展到一定程度后再加入3km网格,生成过程有加快趋势。本研究对这一现象进行了分析。研究发现,只用微物理方案使低层(950-700hPa)风速的垂直切变减小,不利于对流发展。切变减小主要是由于动量垂直输送项的差异导致的。在加入细网格的6h内,低层对流尺度(减去区域平均)的动量垂直输送量平均增加了一倍,某些时刻可以达到5倍以上。动量混合增加是由于微物理方案模拟的垂直速度增加。另外,只用微物理方案导致对流有效位能迅速被消耗。低层垂直切变和CAPE的减小都不利于对流发展,从而导致热带气旋生成发展过程迟缓。本研究表明,目前WRF中的微物理方案在模拟热带气旋生成过程中的对流发展时仍然存在问题。
中文关键词:模式分辨率  热带气旋  生成迟缓  对流有效位能  低层切变  动量垂直输送
 
Analysis of the Delay of Tropical Cyclone Formation in a Higher Resolution Numerical Simulation
Abstract:The WRF model, the most advanced mesoscale model in the world, is used to simulate the genesis process of a tropical cyclone. When the grid spacing is increased from 9km to 3km, the microphysics scheme rather than the cumulus parameterization scheme is used to simulate the convective-scale systems in the 3km domain. As a result, a slower formation process of the tropical cyclone is found. If the 3km domain is added after the perturbation has developed to a certain extent, the formation process accelerates. This study is focused on the analysis on this phenomenon. The result shows that a decrease of low-level (950-700hPa) vertical shear of horizontal wind happens when using the microphysics scheme only, which is negative for the development of convections. The reason for the decrease of low-level vertical shear is the difference of vertical momentum advection between the two experiments. During the 6h after adding the inner nest, convective-scale(removing the area average component) vertical momentum advection at low-level is double on average and 5 times in maximum compared to control run. It is owing to the increase of vertical velocity due to the microphysics scheme, that the momentum mixing is strengthened in the low-level. In addition, using the microphysics scheme only makes the CAPE consumed rapidly. The absence of CAPE and low-level vertical shear both poses negative contribution on the development of convections near the perturbation center and finally results in the delay of tropical cyclone’s genesis. This study demonstrates that there are still some problems in simulating the real development process of convections during the formation of tropical cyclones with the present microphysics scheme in WRF.
keywords:High resolution  Tropical cyclone  Delay of genesis process  CAPE  Low-level vertical shear  vertical momentum advection
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