Improvement of Quantitative Precipitation Forecasts Using a New Microphysical Parameterization

对与破坏性、高影响天气事件相关的降水进行准确预报可以拯救生命和金钱。目前数值天气预报(NWP)模式对微物理过程的描述能力较差，影响了预报精度。这项研究的目的是通过更好地描述微物理过程来改进区域尺度模式中的定量降水预报(QPF)。这个项目的中心假设是，通过对暖、冷和混合相云的一致表示，可以显著改善复杂地形中的QPF。对所有生长过程的显式处理将产生更准确的质量分布和下降轨迹，导致更准确的雨雪空间分布。为了验证中心假设，研究人员将在两个先进的数值模式中实施改进的微物理方案，在理想化模拟中执行严格的敏感性研究，使用分析的数据集验证暴雨和降雪事件的预报，使用具有统计学意义的方法评估QPF和雨雪线预报的改进，测试模型性能，调查实时冬季风暴模拟中云系动力学和微物理的相互作用，并确定计算时间增加与预报改进的比率。模型验证将使用来自两个已完成的现场项目的雨和降雪总量、多普勒和廓线雷达数据，以及现场动态和微物理飞机的测量。新版本的微物理参数化将提供给科学界和设在雷诺的当地核安全局办公室，在那里将在业务环境中测试其性能。

Accurate forecasts of precipitation associated with disruptive, high-impact weather events can save lives and money. Current forecast accuracy suffers from poor representation of microphysical processes in numerical weather prediction (NWP) models. The goal of this research is to improve quantitative precipitation forecasts (QPF) in regional scale models through better formulation of microphysical processes. The central hypothesis of this project is that significant improvement in QPF in complex terrain can be reached through a consistent representation of warm, cold, and mixed-phase clouds. Explicit treatment of all growth processes will generate more accurate mass distributions and fall trajectories, leading to more accurate spatial distribution of rain and snowfall. To test the central hypothesis, the investigators will implement an improved microphysical scheme in two advanced, research numerical models, perform rigorous sensitivity studies in idealized simulations, validate forecasts of heavy rain and snowfall events using analyzed data sets, evaluate improvement in QPF and rain-snow line forecasts using statistically meaningful methods, test model performance and investigate the interaction of the dynamics and microphysics of cloud systems in real-time winter storm simulations, and determine the ratio of increase in computational time to forecast improvement.Rain and snowfall totals, Doppler and profiler radar data, as well as in situ dynamic and microphysical aircraft measurements from two already completed field projects will be used in model validation. The new version of the microphysics parameterization will be made available to the scientific community and the local NWS office in Reno, where its performance will be tested in an operational environment.