Collaborative Research: Measurement and Analysis of the Preconvective Boundary Layer and Convection Initiation during International H2O Project (IHOP)

俄克拉荷马大学和宾夕法尼亚州立大学之间的这个合作项目是国际H2O项目（IHOP）的一部分。IHOP是一个大型的多机构、多研究者项目，专注于测量水蒸气和水蒸气变异性。该项目的目标是提高对对流起始的认识，提高短期降水预报技能，并测试各种仪器测量水汽四维特征的能力。IHOP的实地阶段将于2002年春季和夏季进行，将提供广泛的中尺度气象观测，以便更好地了解水蒸汽变率的尺度和影响过程。这一假设驱动的研究的目标是提高对导致深层潮湿积云对流开始的过程的理解。虽然有几项研究考察了边界层结构的某些方面，但人们对引起对流起始的原因知之甚少。IHOP将提供开始评估和修正有关对流起始过程和边界层水蒸气作用的假设所需的综合数据集。主要研究人员将获取和分析三维雷达导出的边界层气流，以及来自移动设备的风和热力学参数的现场测量。边界层气流与绝对湿度和虚温度的现场测量相结合，提供了记录边界层中调节可降水量和推动二次环流发展的动力和输送过程的唯一手段。因此，这些观测对于评估有关水汽供应和气流演变对边界形成和对流起始的影响的假设是必不可少的。详细的观察结果将以几种不同的方式进行分析。将结合有关尺度上所有可用的对流起始数据进行主观分析和可视化。利用基于多多普勒风合成的拉格朗日轨迹分布近保守变量的先进时空转换方案，将提高观测密度。最后，这些增强的观测将被吸收到中尺度模式中，以确定控制局域边界层环流发展的动力强迫过程，这些过程促进或阻止对流的形成。这一努力将导致以前所未有的规模收集和分析前所未有的数据集。通过这项工作，将对发生在低水平边界附近的过程以及这些过程如何调节雷暴的形成有一个全新的认识。通过提高预测对流是否、何时、何地发展的能力，这些知识将有助于在定量降水预报方面取得新的进展，无论是在数值上还是主观上。

This collaborative project between the University of Oklahoma and the Pennsylvania State University is part of the International H2O Project (IHOP). The IHOP is a large multi-agency, multi-investigator project that focuses on the measurement of water vapor and water vapor variability. The goal of this project is to improve understanding of convective initiation, increase short-term precipitation forecast skills and test the capabilities of various instruments to measure the four dimensional characteristics of water vapor. The field phase of the IHOP will be conducted during the Spring and Summer of 2002 and will provide a wide range of mesoscale meteorological observations for studies to gain a better understanding of the scales of, and processes influencing, water vapor variability.The goal of this hypothesis-driven research is to improve understanding of the processes leading to the initiation of deep, moist cumulus convection. Though several studies have examined certain aspects of boundary layer structure little is known about what causes convective initiation. IHOP will provide the comprehensive data sets needed to begin evaluating and revising hypotheses concerning convection initiation processes and the role of boundary layer water vapor. The Principal Investigators will acquire and analyze three dimensional radar-derived boundary layer airflow and in-situ measurements of winds and thermodynamic parameters from mobile facilities. The combination of boundary layer airflow with in-situ measurements of absolute humidity and virtual temperature provides the only means of documenting the dynamical and transport processes acting in the boundary layer to regulate precipitable water and force the development of secondary circulations. Thus these observations are essential for evaluating hypotheses concerning the impact of water vapor supply and airflow evolution on boundary formation and convection initiation.Detailed observations will be analyzed in several different ways. Subjective analyses and visualizations will be produced incorporating all available data on relevant scales for convection initiation. Observation density will be enhanced utilizing an advanced time-to-space conversion scheme by distributing nearly conservative variables along Lagrangian trajectories based on multi-Doppler wind syntheses. Finally, these enhanced observations will be assimilated into mesoscale models to determine the dynamical forcing processes controlling the development of localized boundary layer circulations that either promote or prevent convection initiation.This effort will result in the collection and analysis of an unprecedented data set at scales previously not observed. Through this work, a completely new understanding will emerge regarding the processes occurring near low-level boundaries and how these processes regulate the formation of thunderstorms. The knowledge will be useful for developing new advances, both numerical and subjective, in quantitative precipitation forecasting by improving the ability to forecast if, when, and where convection will develop.