Interactions of Gravity Waves and Moist Convection in the Troposphere and Stratosphere

gravity wave;turbulence;mesoscale gravity wave

Suffern, Paul Samuel ; Matthew D. Parker, Committee Member,Yuh-Lang Lin, Committee Chair,Michael L. Kaplan, Committee Member,Suffern, Paul Samuel ; Matthew D. Parker ; Committee Member ; Yuh-Lang Lin ; Committee Chair ; Michael L. Kaplan ; Committee Member

University:North Carolina State University

关键词: gravity wave;    turbulence;    mesoscale gravity wave;   

Others  :  https://repository.lib.ncsu.edu/bitstream/handle/1840.16/90/etd.pdf?sequence=1&isAllowed=y

美国|英语

来源: null

【 摘 要 】

On December 12th and 13th, 2002 a deep large-amplitude tropospheric mesoscale gravity wave formed over Texas and propagated northeastward across several states. This study examines the role of the coupling of geostrophic adjustment, moist convection, and an area of shear instability from the meso- to the meso- scale as the mesoscale gravity wave is formed⁄maintained. Three main chapters comprise this thesis. Chapter 4 employs observations to describe the mesoscale gravity wave event. Numerical modeling of the mesoscale gravity event is explained in Chapter 5 to further understand the coupling of geostrophic adjustment, moist convection, and the area of shear instability. Chapter 6 analyzes the vertically propagating gravity waves in the lower stratosphere employing observations and numerical modeling.Observations of the mesoscale gravity wave system allow a detailed representation of the event. As an upper-level jet streak moved into central Texas, moist convection and a corresponding surface low-pressure system began to develop. The development of widespread convection lead to the downstream growth of a secondary jet streak, which in turn continued the imbalance of mass and momentum at the upper-levels across central Texas. Geostrophic adjustment and moist convection are closely correlated with the mesoscale gravity wave as the mesoscale gravity wave forms and moves northeastward all the way to Mississippi. Other observations also show dry air and large amounts of shear located directly behind the moist convection. The development of an area of possible shear instability behind the moist convection represents mixing and descending momentum in the troposphere and formation/maintenance of the mesoscale gravity wave.Chapter 5 confirms and enhances the observations of the coupling between geostrophic adjustment, moist convection, and the area of shear instability through numerical simulations. Mass and momentum perturbations from the moist convection are directed upward, upstream, and cross-stream into the jet streak momentum. Momentum in the moist convective process descends toward the stable layer, resulting in mass accumulation near the surface, as simultaneously, the updraft within the strengthening moist convection penetrates into the lower stratosphere. The mesoscale gravity wave(s) is(are) initiated/maintained as the negative buoyancy perturbation and descent of momentum interacts with the stable layer near the surface behind the moist convection. The impact of latent heating and its importance to the development of the coupling of mesoscale gravity wave system are discussed in this chapter employing model sensitivity studies.Chapter 6 analyzes the development of vertically propagating gravity waves in the lower stratosphere. Observations from the Advanced Microwave Sounding Unit-A (AMSU) polar orbiting satellite show a signal of possible vertically propagating gravity waves above the moist convection across Texas and the Gulf of Mexico. Numerical simulations were performed to diagnose the environment in which these gravity waves formed in the lower stratosphere as well as their realism to the observations.