Warm season diurnal precipitation over the plains east of the Rockies

落基山脉以东的平原是全球粮食生产的中心，被称为世界粮仓。这些地区经常遭遇极端暴雨，夏季洪灾往往与对流天气和天气系统产生的强降水有关。然而，人们对平原上观测到的降雨量日循环，特别是夜间最大降雨量知之甚少。对流系统的向东传播在目前的数值天气预报模式中也有很大程度的不足。与美国大平原相比，加拿大大草原夏季的日降雨量相对较少。*我的目标是解决以下问题：1)控制对流启动的主要物理机制是什么，昼夜降水的峰值时间，以及夏季在落基山脉以东的平原上它的系统向东传播？我们如何结合这些物理机制来改进基于模式的短期暖季降水预报？2)我们如何在模式中适当地再现热带西太平洋对流和加拿大草原夏季降水之间的远程联系，以改进亚季节气候预报？*为了实现这些目标，将招募两名博士和一名硕士学生，利用现场观测和遥感分析、物理理论以及前沿的数值模拟进行综合研究。*两名博士生将致力于了解对流机制和暖季平原上降水的东传。具体地说，我们将重点检验我们新的位涡假设，并探索地面过程(如蒸散)对日对流和对流起始的影响。另一个重点是预报模式的校准。*这位理科硕士学生将研究热带太平洋对流对草原暖季降水的远程影响。有了热带耦合海洋-大气动力学的适当表示，预报模式将能够适当地再现这种远程联系。*这项工作将推进加拿大草原暖季降水的天气和气候预报。改进后的预报有可能通过将降水转化为地表水文和洪水信息，为业务实践提供信息。这将提高我们规划水资源分配、供水变化和灾害管理的能力，从而进一步有利于区域农业和粮食安全以及生态系统的可持续性。所有这些都会带来重大的经济后果。*****

The plains east of the Rockies are central to global grain production and known as the Breadbasket of the World. These regions are subjected to a high frequency of extreme rainstorms with summer flooding frequently associated with heavy precipitation generated by convective and synoptic weather systems. However the rainfall diurnal cycle especially the nighttime rainfall maximum observed over the plains is poorly understood. The eastward propagating of the convective systems is also largely under-represented in current numerical weather prediction models. Compared to the US Great Plains, the summertime diurnal precipitation over the Canadian Prairies is relatively unexplored. ******My objectives are to address the following questions: 1) What are the dominant physical mechanisms that control the convection initiation, the peak time of the diurnal precipitation, as well as its systematic eastward propagation over the plains east of the Rockies in summer time? How can we incorporate these physical mechanisms to improve short-range, model-based forecasts of warm-season rainfall? 2) How can we appropriately reproduce the remote connection between the convection over the tropical western Pacific and the summer season precipitation over the Canadian Prairies in the model to improve the sub-seasonal climate prediction?******To achieve these goals, two PhD and one MSc students will be recruited to conduct comprehensive studies using field observations and remote sensing analysis, physical theory, as well as cutting-edge numerical modeling. ******The two PhD students will work on understanding the convective mechanisms and the eastward propagation of the precipitation over the plains in warm season. Specifically, one will focus on testing our novel Potential Vorticity hypothesis and exploring the effects of surface processes such as evapotranspiration on diurnal convection and convection initiation. The other will focus on the forecasting model calibration.******The MSc student will investigate the remote influence of the convection over the tropical Pacific Ocean on the warm season precipitation over the Prairies. With the appropriate representation of the tropical coupled oceanatmosphere dynamics, the forecasting model will be able to reproduce this remote connection appropriately.******This work will advance the weather and climate forecast of warm-season precipitation over the Canadian Prairies. The improved prediction has the potential to inform operational practice through translating precipitation to surface hydrology and flooding information. This will improve our ability in planning for water resources distribution, water supply changes and disaster management, which will further benefit regional agriculture and food security as well as ecosystem sustainability. All of which have significant economic consequences. *****