Collaborative Research: Improvement of Microphysical Parameterization Through Observational Verification Experiment (IMPROVE)

改进定量降水预报(QPF)已被列为美国气象研究计划的首要任务之一。在北美西部多山的沿海地区，对准确的QPF的需求尤其迫切，那里的强降水和洪水是最严重的天气灾害之一。即使业务模式分辨率稳步提高，定量降水预报的改进也很缓慢。这一事实表明，除了提高网格分辨率外，中尺度模式的其他组成部分还必须改进。一个明显有问题的领域是网格分辨的云微物理和降水的整体参数化。根据这一合作项目，来自华盛顿大学的两名研究人员将执行一个实地项目，相关数据分析和数值模拟工作，以改进中尺度模式的定量降水预报。该项目将对模型参数化云和降水微物理进行全面的观测验证和改进。首席调查人员将在太平洋西北部开展两个观测活动：2000/2001年冬季在华盛顿州东北太平洋近海进行锋面降水研究，2001/2002年冬季在俄勒冈州中部的喀斯喀特山脉进行地形降水研究。目前的大块云微物理参数化基于相对较少的观测研究；很少有专门的努力来综合评估这些方案的基本假设和预测的水文气象分布，并利用这些试验来改进参数化。要以产生明确和明确结果的方式进行这种核实，唯一的方法是观察模拟降水系统的所有方面，从三维温度和风分布到混合比和颗粒尺寸分布等微物理参数。这需要同时使用一架仪器齐全的飞机进行的现场云和降水微物理观测以及三维风场的遥感(雷达)观测。近年来，数值模拟、机载微物理测量和雷达技术的进步融合在一起，使这种研究变得非常及时。此外，华盛顿大学的科学专长、实地项目经验、观测设施和计算能力的独特组合，以及经历了冬季锋面和地形降水系统频率较高的地理位置，是开展拟议研究的理想条件。

Improvements in quantitative precipitation forecasting (QPF) have been listed as one of the top priorities of the U.S. Weather Research Program. The need for accurate QPF is especially acute along the mountainous coastal zone of western North America, where heavy precipitation and flooding are among the most significant weather hazards. Even with steady improvements in operational model resolution, quantitative precipitation forecasting has been slow to improve. This fact suggests that, in addition to increased grid resolution, other components of mesoscale models must be improved. One clearly problematic area is the bulk parameterization of grid-resolved cloud microphysics and precipitation. Under this collaborative project, two researchers from the University of Washington will execute a field program, associated data analysis and numerical modeling work, to improve quantitative precipitation forecasting in mesoscale models. The project will undertake comprehensive observational verifications and improvements of model-parameterized cloud and precipitation microphysics. The Principal Investigators will carry out two observational campaigns in the Pacific Northwest: a frontal precipitation study over the northeast Pacific Ocean offshore of Washington state in the winter of 2000/2001, and an orographic precipitation study in the Cascade Mountains of central Oregon in the winter of 2001/2002.Current bulk cloud microphysical parameterizations are based on relatively few observational studies; few dedicated efforts have been made to comprehensively evaluate the underlying assumptions and predicted hydrometeor distributions of these schemes, and to use such tests to improve the parameterizations. The only way to perform such verification in a manner that yields definitive and unambiguous results is to observe all aspects of the simulated precipitation system, from three-dimensional temperature and wind distributions to microphysical parameters such as mixing ratios and particle size distributions. This requires concurrent use of in situ cloud and precipitation microphysical observations from a well-instrumented aircraft and remotely sensed (radar) observations of the three-dimensional wind field. Recently, advances in numerical modeling, airborne microphysical measurement, and radar technology have converged to make such a study highly opportune. Furthermore, with a unique combination of scientific expertise, field project experience, observational facilities, and computing power, as well as a geographic location that experiences a high frequency of frontal and orographic winter precipitation systems, the University of Washington is ideally positioned to carry out the proposed research.(i)