Studies on hurricanes: Intensity change and early genesis

飓风研究：强度变化和早期起源

• 批准号: RGPIN-2015-04023
• 负责人: Yau, ManKong(Peter)
• 金额: $ 1.6万
• 依托单位: McGill University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=669267
• 关键词: Studies; hurricanes; Intensity; change; early

Hurricanes are violent vortices in the atmosphere. For hurricane prediction, two major problems remain. One is to forecast the rapid intensification (RI) of the storm and the other is to forecast when a storm will form.***Convection in the eyewall can affect RI in two ways. First, latent heating released in cloud processes is a main source of energy. Its spatial distribution affects RI especially when bursts of convection occur inside the radius of maximum wind. Second, latent heating in the eyewall produces a hollow tower of potential vorticity (PV) that supports propagating vortex Rossby waves (VRW) which may become unstable to mix eyewall PV into the eye to effect intensity change. Additionally, VRWs in a hurricane vortex can radiate gravity waves leading to another instability known as radiative pumping. However, this instability can be damped at a critical radius outside the vortex core where the angular velocity of the waves matches the fluid rotation rate. The understanding of these instabilities is important to improve hurricane forecasting. ***Atlantic hurricanes are often initiated from easterly wave disturbances out of Africa, but only a small fraction ever develop into a tropical storm. A recent theory stipulates that tropical cyclogenesis is favored in a pouch which is similar to the cat's eye recirculation region within the critical layer of the parent wave. However, there are no comprehensive studies on how a pouch forms. ***The objective of the proposed research program is to advance our understanding of hurricane intensity change and early tropical cyclogenesis through theoretical analysis, high resolution modeling, and diagnostic studies. The relevant scientific questions to answer are:***a) How microphysical processes regulate the distributions of latent heating and water loading which may bear strongly on hurricane intensity? ***b) How do instabilities and the critical radius affect hurricane intensity change?***c) How does a pouch form during the early genesis stage of a hurricane?***Theoretical analysis, high resolution computer modeling, and diagnostic studies will be brought to bear to yield answers to the above questions. ***The research program will improve our understanding of hurricane intensity change and the mechanism for genesis. It will help in the forecasting of these violent systems. *****

飓风是大气中猛烈的涡流。飓风预测还存在两个主要问题。一个是预测风暴的快速增强（RI），另一个是预测风暴何时形成。***眼壁对流可以通过两种方式影响RI。首先，云过程中释放的潜热是能量的主要来源。当最大风半径内发生对流爆发时，其空间分布对RI有较大影响。其次，眼壁的潜热会产生一个空的位涡塔（PV），支持传播的涡罗斯比波（VRW），而涡罗斯比波可能会变得不稳定，从而将眼壁PV混合到眼内，从而影响强度变化。此外，飓风涡旋中的vrw可以辐射重力波，导致另一种称为辐射泵的不稳定性。然而，这种不稳定性可以在涡核外的临界半径处得到抑制，在那里波的角速度与流体的旋转速率相匹配。了解这些不稳定性对改善飓风预报很重要。大西洋飓风通常是由非洲的东风波扰动引起的，但只有一小部分发展成热带风暴。最近的一项理论认为，热带气旋的形成是在一个类似于母波临界层内的猫眼再循环区域的小袋中发生的。然而，关于眼袋是如何形成的还没有全面的研究。***拟议研究计划的目的是通过理论分析、高分辨率模拟和诊断研究，提高我们对飓风强度变化和早期热带气旋形成的认识。需要回答的相关科学问题是：***a)微物理过程如何调节可能对飓风强度产生强烈影响的潜热和水负荷的分布？***b)不稳定性和临界半径如何影响飓风强度变化？***c)在飓风的早期形成阶段，袋状物是如何形成的？***将运用理论分析、高分辨率计算机建模和诊断研究来回答上述问题。这个研究项目将提高我们对飓风强度变化和形成机制的认识。它将有助于这些暴力系统的预测。＊＊＊＊＊