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。这些地区经常发生极端暴雨，夏季洪水往往与对流和天气系统产生的强降水有关。然而，降雨量的日周期，特别是在平原上观测到的夜间降雨量最大值却知之甚少。对流系统的东向传播在目前的数值天气预报模式中也很大程度上没有得到充分的体现。与美国大平原相比，加拿大大草原的夏季日降水量相对较少。 我的目标是解决以下问题：1）是什么占主导地位的物理机制，控制对流的启动，日降水的峰值时间，以及它的系统性东向传播的平原东部落基山脉在夏季的时间？我们如何将这些物理机制结合起来，以改善短期的、基于模型的暖季降雨预测？2)我们如何在模式中适当地再现热带西太平洋对流与加拿大大草原夏季降水之间的远程联系，以改善亚季节气候预测？ 为了实现这些目标，将招募两名博士和一名硕士学生，利用实地观察和遥感分析，物理理论以及尖端数值建模进行全面研究。 两位博士生将致力于了解暖季平原上的对流机制和降水的东向传播。具体来说，我们将专注于测试我们的新的位涡假设和探索的表面过程，如蒸散日对流和对流启动的影响。另一部分是预测模型的校正。 硕士学生将调查热带太平洋对流对大草原暖季降水的远程影响。通过对热带海洋-大气耦合动力学的适当表述，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大草原暖季降水的天气和气候预报。改进后的预测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。所有这些都有重大的经济后果。

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.