Dynamics and Predictability of Mesoscale Rainband in Lee Cyclones

9700626 Koch与对气旋天气尺度的理解和预报能力的进步相比，预报与中纬度气旋有关的降水和恶劣天气的进展缓慢。造成这种情况的一个主要原因是缺乏具有足够空间和时间分辨率的数据来解析与降水带相关的中尺度过程。中尺度重力波被认为在降水带的形成和调制中起重要作用。引力波对天气预报员来说是一个真正的挑战，因为它们几乎不可能用标准的天气观测来探测，也不能通过操作模型进行常规预测。国家气象局现代化带来的主要观测和模式改进现在为研究和业务气象界共同努力提高对这些中尺度现象的理解提供了机会。对于重力波的产生机制和垂直结构、它们与对流的相互作用以及它们在气旋形成过程中的作用，还需要进一步的研究，以区分它们与其他中尺度现象，特别是高空冷锋的存在。造成这种混淆的一个原因是，证据往往表明可能有不止一种机制在起作用。首席研究员最近的研究主要集中在理解产生天气的中尺度重力波的强迫、动力学和垂直结构，主要使用在STORM-FEST项目中获得的地面、风廓线仪和中尺度模式数据。首席研究员发现，在背风气旋形成过程中，当射流条纹遇到落基山脉时，在动力不平衡的区域会产生强烈的波浪。然而，至少在其中一个案例中，证据还表明，高空冷锋发生在靠近海浪的地方。根据该奖项进行的研究既代表了首席研究员过去努力的延续，也代表了向新的相关方向的扩展。最终目标是将观测到的降水带结构和动力学纳入美国中部背风气旋的新概念模型。第一个目标是解决高空冷锋与重力波的作用，或者它们之间的相互作用，在雨带的产生中。其次，该研究将有助于消除关于不平衡动力学在重力波形成中的作用的模糊性。第三个目标是解决中尺度可预测性问题，即中尺度模式需要哪些数据和数据同化技术才能可靠地产生观测到的重力波。最后，首席研究员将完成正在进行的对冷锋产生的孤立波和孔的调查。这项研究的结果可能会对中尺度重力波的预测能力产生直接和直接的影响。* * *

9700626 Koch Progress in forecasting of precipitation and severe weather associated with mid-latitude cyclones has been slow, compared to advances in understanding and ability to forecast the synoptic-scale aspects of cyclones. A major reason for this has been the lack of data with sufficient spatial and temporal resolution to resolve mesoscale processes associated with precipitation bands. One of the mesoscale phenomena that has been suggested to play an important role in the formation and modulation of precipitation bands is mesoscale gravity waves. Gravity waves present a real challenge to weather forecasters, because they have been nearly impossible to detect with standard synoptic observations and are not routinely predicted by operational models. The major observational and modeling improvements being brought about by the National Weather Service Modernization now affords the opportunity for the research and operational meteorological communities to work together to develop improved understanding of these mesoscale phenomena. Additional research is needed on wave dynamics and generation mechanisms, and to differentiate them from the presence of other mesoscale phenomena, notably cold fronts aloft A definitive identification of gravity wave generation mechanisms and vertical structure, their interactions with convection, and their role in the cyclogenesis process remains elusive. One cause for this confusion is that the evidence often suggests more than one mechanism may be operative. Recent research by the Principal Investigator has focused on understanding the forcing, dynamics, and vertical structure of weather-producing mesoscale gravity waves using primarily surface, wind profiler, and mesoscale model data obtained during the STORM-FEST project. The Principal Investigator has found there to be a predilection for strong waves to be generated in regions of dynamic imbalance during lee cyclogenesis as a jet streak encounters the Rocky Mountai ns. However, in at least one of these cases, the evidence also suggests that a cold front aloft occurred in close proximity to the waves. The research to be performed under this award represents both a continuation of the Principal Investigator s past efforts and an extension into new but related directions. The ultimate goal is to incorporate observed precipitation band structure and dynamics into a new conceptual model for lee cyclones in the central U. S. The first objective is to resolve the role of cold fronts aloft versus gravity waves, or perhaps their interactions, in the generation of rainbands. Secondly, the research will help to remove ambiguities concerning the role of unbalanced dynamics in gravity wave formation. The third objective, will be to address the issue of mesoscale predictability, in terms of what data and data assimilation techniques are required for mesoscale models to reliably produce observed gravity waves. Lastly, the Principal Investigator will complete an ongoing investigation of solitary waves and bores generated by cold fronts. Results from this research potentially will have direct and immediate impact on the ability to predict mesoscale gravity waves. ***