Interactions of gravity waves and moist convection in the troposphere and stratosphere

by (Paul Samuel), 1981- Suffern

SUFFERN, PAUL SAMUEL. Interactions of gravity waves and moist convection in the troposphere and stratosphere (Under the direction of Drs. Yuh-Lang Lin and Michael L. Kaplan). 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.