垂直-倾斜对流一体化参数化方案的实现及数值试验

Development of an integrated vertical slantwise convective parameterization scheme and its numerical experiments

中文关键词:  暴雪，台风，条件性对称不稳定，垂直-倾斜对流一体化参数化方案，数值模拟

英文关键词:Snowstorm, Typhoon, Conditional symmetric instability (CSI), The integrated-vertical-slantwise convective parameterization scheme, Numerical simulation

中文摘要:

      在Kuo-Anthes垂直对流参数化方案和Nordeng倾斜对流参数化方案基础上，提出了垂直 倾斜对流一体化参数化方案，并引入MM5模式中。利用该方案对2008年1月28—29日发生在中国南方的一次暴雪过程和2005年“海棠”台风过程进行了数值模拟，模拟结果表明，此次暴雪过程在垂直方向主要表现对流稳定状态，但在对流层低层始终存在条件性对称不稳定层，并且当条件性对称不稳定区向高层发展时，伴随着强上升运动作为触发机制，引发条件性对称不稳定能量的释放，产生更多的对流降水，使模拟的总降水量与实况更加一致。条件性对称不稳定的发展加强与降雪强度、辐合辐散和上升运动变化一致，条件性对称不稳定是造成暴雪发展加强的主要机制之一。通过对“海棠”台风72 h的模拟表明，条件性对称不稳定主要发生在台风的低层，且其水平分布呈螺旋状结构。条件性对称不稳定效应对台风路径影响较小，但对台风强度影响较大，在模式中考虑垂直 倾斜对流一体化参数化方案后，与仅考虑垂直积云对流参数化方案相比，72 h模拟的平均台风中心最低气压降低了3 hPa，最大达8 hPa。在模式中考虑条件性对称不稳定的影响，可使模式台风中上层的暖心结构更加明显，上升运动和对流性降水增强，对流释放的更多凝结潜热使台风得到进一步加强。

英文摘要:

      An integrated vertical-slantwise convective parameterization scheme, based on the vertical Kuo-Anthes and slantwise Nordeng convection parameterization schemes, is presented and introduced into the MM5 model. By employing MM5 model with the proposed scheme, some numerical simulations are conducted with the snowstorm event occurred over the southern China on 28-29 January 2008 as well as Typhoon Haitang (2005) process as the examples. The results indicate that the atmosphere was mainly convective stable in the vertical direction in the simulation on the snowstorm event, but with a conditional symmetric instablity occurred in the lower troposphere; and that when the area of conditional symmetric instability (CSI) developed toward the upper levels, the strong rising motion as the trigger mechanism released large amount of energy of CSI, producing more convective precipitation with the total precipitation much more closer to that of the observed. In the simulation, the developing and strengthening of CSI were corresponding to changes in the intensity of snowfall, the convergence, and the strong ascending motion of air, revealing CSI to be one of the important mechanisms responsible for the initiation and growth of the snowstorm. The results from a 72 h explicit simulation on Typhoon Haitang indicate that the CSI occurred mainly at the lower levels in the typhoon, with well defined spiral structure; and that CSI tended to have a larger impact on the intensity of typhoon than on the track. The minimum pressures at the typhoon center for 72 hour runs with the integrated vertical slantwise convective parameterization scheme used were 3 hPa on average with the maximum of 8 hPa, lower than those of the runs with only vertical cumulus parameterization scheme involved. The simulation results are encouraging as introducing the influence of CSI into the model can better improve the warm core structure at the middle and upper levels of the model typhoon, with the strong and persistent upward motion of air to cause much more convective precipitation and the latent heat released through convection in turn to make the typhoon develop further.