GRAPES中地形重力波拖曳物理过程的引进和应用试验

Introducing and application testing of the orographic gravity wave drag parameterization physics in the GRAPES

中文关键词:  地形重力波拖曳，GRAPES，数值试验

英文关键词:Orographic gravity wave drag, GRAPES, Numerical experiment

中文摘要:

      在中国新一代全球中期/区域中尺度同化与预报系统（GRAPES）模式中引进了ECMWF地形重力波拖曳物理过程，填补了GRAPES全球中期数值预报系统中物理过程的空白。重新计算了地形重力波过程需要的地形静态资料数据，并与原ECMWF模式的地形静态参数进行了对比分析，验证了模式地形参数的正确性。利用GRAPES模式，进行了地形重力波拖曳物理过程影响的敏感性数值试验；结果表明：引进地形重力波拖曳过程以后，在存在大地形的区域，风场会发生变化，当纬向风遇到青藏高原时，一部分气流会产生爬坡效应而越过高原，使高原上空的西风气流减弱；另一部分气流会绕过高原，在高原的南侧产生绕流；随着模式积分时间的延长，风场变化会越来越明显，地形越复杂，风场的变化也越复杂；连续的模式积分试验结果显示，引进地形重力波过程，可以延长GRAPES模式的可用预报时效，提高了全球形势预报的准确率。通过对一次降水过程的模拟，对地形重力波过程影响降水预报的原因进行了简单分析。结果显示：引进地形重力波拖曳过程后，改变了大气流场的分布，使预报的流场更接近于大气真实状态，从而提高了降水预报的准确率。

英文摘要:

      The orographic gravity wave drag parameterization physics in the ECMWF model is introduced into the Global/Regional Assimilation and Prediction System (GRAPES) that filled up the blank of physics in the GRAPES for global middle range forecast. Orographic static data needed in the gravity wave drag physics are recomputed and validated through comparing with the original static data from the ECMWF model. Numerical experiments have been performed to test the sensitivity of the GRAPES to gravity wave drag parameterization. The results show that as the orographic wave drag is implemented in the GRAPES, the wind field will be changed over the large scale topography region, the part of zonal wind encountered the Qinghai Tibet plateau will pass over the highland with the speed slowing down and the other part of the zonal wind will deflect southward and bypass the highland with a circuitous route. The wind field change is more observable with the model run time extended. The more diversiform is terrain structure, the more various are forecasting wind changes. The successive numerical experiments using GRAPES indicate that the usable forecast period of time is prolonged and then forecasting precision of the global geopotential height pattern is enhanced as the orographic gravity wave drag physics is implemented in the GRAPES. At the end, the pilot study of gravity wave drag physics effect on precipitation is done through a weather case simulation analysis. Evidences suggest that introducing of orographic gravity wave drag physics in GRAPES can improve precipitation forecast of the system since the forecasting wind pattern is changed so as to be closer to the real atmosphere state.