The Role of the Precipitation Mass Sink in Tropical Cyclone Dynamics

降水质量汇在热带气旋动力学中的作用

• 批准号: 0334427
• 负责人: Gary Lackmann
• 金额: $ 22.47万
• 依托单位: North Carolina State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-12-01 至 2007-11-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0334427&HistoricalAwards=false
• 关键词: Role; Precipitation; Mass; Sink; Tropical

During heavy precipitation, significant quantities of water vapor are removed from the atmosphere to the surface, resulting in a hydrostatic pressure reduction due to the decrease of mass in the overlying column. The representation of this precipitation mass sink is either non-existent or incomplete in current atmospheric models because water vapor mass continuity is not explicitly coupled to the total mass continuity or pressure tendency equations. For tropical cyclones in which precipitation rates may exceed 200 mm per day, the pressure-equivalent mass removal is not negligible, on the order of 20 hPa. The pressure decrease due to precipitation would be partially compensated by horizontal mass convergence. However, this convergent inflow may be critical to moisture transport and vorticity generation, especially in the presence of strong rotation. The initial hypothesis to be tested is that the pressure reduction due to the removal of atmospheric mass by precipitation is a first-order dynamical process in tropical cyclones. A second, related hypothesis is that including the mass sink effect explicitly in numerical weather prediction models will improve their ability to accurately predict tropical cyclone genesis, intensity, and track.The focus of the research will be on understanding the physical mechanism of the precipitation mass sink as it relates to tropical cyclone dynamics. The Principal Investigator will isolate the important mechanisms by undertaking a series of numerical model experiments that selectively include and exclude the mass sink terms in the governing equations. The specific objectives of this project are to:1. Develop and test a numerical model that includes both water loading and precipitation mass sink effects in the model continuity, pressure-tendency, and momentum equations. 2. Conduct a thorough observational data analysis for Hurricane Lili (and/or other cases) including in-situ aircraft data, remotely sensed data (radar and satellite) and dropsondes. The observational analysis will allow detailed evaluation of numerical model simulations. 3. Conduct a series of sensitivity experiments on Hurricane Lili or other cases. The analysis will include mass, moisture, and momentum budgets. Storm-relative budgets for a cylindrical volume moving with the storm will isolate the relative importance of water loading and the precipitation mass sink to tropical cyclone dynamics. A centerpiece of the analysis will be a potential vorticity (PV) diagnosis, including budget computations and piecewise inversions.4. Formulate a conceptual model for tropical cyclogenesis and intensification that accounts for the role of the mass sink mechanism.The impacts of the research include i) potentially improved numerical forecasts of tropical cyclone formation, intensification, and track. ii) Improved understanding of the role that precipitation plays in the dynamics of tropical cyclones.

在大沉淀过程中，由于上覆柱中的质量减少，大气中的大量水蒸气从大气中移到表面，从而导致静水压力降低。 在当前大气模型中，这种降水量质量水槽的表示是不存在的，要么是不完整的，因为水蒸气质量连续性未明确耦合到总质量连续性或压力趋势方程。 对于每天降水速率可能超过200 mm的热带气旋，按20 hPa的阶，压力等效的质量去除量不可忽略不计。 由于降水引起的压力降低将通过水平质量收敛来部分补偿。 但是，这种收敛的流入可能对水分传输和涡度产生至关重要，尤其是在强烈旋转的情况下。 要测试的最初假设是，由于沉淀去除大气质量而导致的压力降低是热带气旋的一阶动力学过程。 第二个相关的假设是，在数值天气预测模型中明确包括质量下水道效应将提高其准确预测热带气旋的起源，强度和轨道的能力。研究的重点将放在与热带旋风动力学相关的降水质量下沉的物理机理上。 主要研究者将通过进行一系列数值模型实验来隔离重要机制，这些模型实验有选择地包括和排除管理方程中的质量下水道项。 该项目的具体目标是：1。 开发和测试一个数值模型，其中包括模型连续性，压力趋势和动量方程中的水负荷和降水量质量下水道效应。 2。对飓风（和/或其他情况）进行彻底的观察数据分析，包括原位飞机数据，远程感应的数据（雷达和卫星）和滴虫。 观察性分析将允许对数值模型模拟的详细评估。 3.对飓风lili或其他情况进行一系列灵敏度实验。 分析将包括质量，水分和动量预算。 圆柱量与风暴移动的圆柱状预算将隔离水负荷的相对重要性和降水量质量下水道与热带气旋动力学的相对重要性。 该分析的核心将是潜在的涡度（PV）诊断，包括预算计算和分段倒置。4。 为热带循环发生和强化的概念模型制定了质量下沉机制的作用。研究的影响包括i）可能改善了热带旋风形成，强化和轨道的数值预测。 ii）提高了对降水在热带气旋动力学中所起的作用的理解。