Moist Absolutely Unstable Layer

潮湿的绝对不稳定层

• 批准号: 9806309
• 负责人: J. Michael Fritsch
• 金额: $ 42.25万
• 依托单位: Pennsylvania State Univ University Park
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1999
• 资助国家: 美国
• 起止时间: 1999-04-01 至 2003-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9806309&HistoricalAwards=false
• 关键词: Moist; Absolutely; Unstable; Layer

The theoretical characteristics of atmospheric convection have been studied for many years and the basic characteristics of different forms of convection are considered to be well-known. The Principal Investigator presents observational evidence that a phenomenon that he terms "moist absolutely unstable layers" (MAULs) occur in the atmosphere. It would be expected that such layers would dissipate quickly through turbulence, but the Principal Investigator hypothesizes that under certain conditions, these layers may be created faster than they can be dissipated. If MAULs indeed do persist over long time periods and spatial scales, this may have important implications for certain types of atmospheric convection. The main objectives of this proposal are to: (1) determine how MAULs are created and maintained; (2) determine the properties of MAULs and demonstrate that the lateral extent, depth and intensity of these layers play a fundamental role in establishing the organizational mode of moist convective overturning. The research methodology consists of three parts: (1) numerical simulations of existing observational cases that appear to exhibit MAULs; (2) numerical sensitivity experiments to determine the effects of varying model resolution and artificially changing the depth and strength of MAULs; (3) sensitivity experiments on idealized conditions generated from three-dimensional analytical initializations. It is expected that knowledge gained from this research will enhance fundamental understanding of the organizational and lifecycle processes of mesoscale convective systems. The results potentially will provide practical benefits, such as improvements in short-term (3 to 18 hour) weather forecasts and in the parameterization of convective processes in global climate models. The results also should provide a basis for theoretical studies of moist absolutely unstable layers.

大气对流的理论特性已经研究了很多年，不同形式对流的基本特性被认为是众所周知的。 首席研究员提出了观测证据，他称之为“潮湿的绝对不稳定层”（MAULs）的现象发生在大气中。 预计这些层将通过湍流迅速消散，但主要研究者假设在某些条件下，这些层的产生速度可能比消散速度更快。 如果MAULs确实在长时间和空间尺度上持续存在，这可能对某些类型的大气对流具有重要意义。 该方案的主要目标是：（1）确定MAUL是如何产生和维持的;（2）确定MAUL的性质，并证明这些层的横向范围、深度和强度在建立湿对流翻转的组织模式中起着基本作用。 研究方法包括三个部分：（1）现有观测案例的数值模拟，似乎表现出MAULs;（2）数值敏感性实验，以确定不同的模式分辨率和人为改变的深度和强度的MAULs的影响;（3）敏感性实验的理想化条件下产生的三维分析初始化。 预计从这项研究中获得的知识将加强对中尺度对流系统的组织和生命周期过程的基本理解。 这些结果可能会带来实际好处，例如改进短期（3至18小时）天气预报和全球气候模型中对流过程的参数化。 研究结果也为湿绝对不稳定层的理论研究提供了依据。