Title: 

"Dynamical stability of stratified anabatic flows in idealized valleys” 

ABSTRACT: 

Weather prediction models struggle to accurately represent nighttime, stably-stratified conditions in the atmospheric boundary layer. These struggles are compounded in areas of complex terrain, due to the difficulty of parameterizing enigmatic flow-physical processes. One example of this is the diurnal cycle in mountain valleys. During the nighttime, the radiative cooling from the surface leads to down-slope flows and the formation of a stably-stratified cold pool at the valley base. As the sun rises, the walls of the valley are heated, causing up-slope flow and destruction of the stably stratified medium. Understanding stratified flows in complex terrain has many important implications, such as predicting transport of pollutants and emissions, forecasting fog and frost formation, and even estimating ice loss from polar ice sheets, due to the prevalence of stratified conditions over large ice sheets. Many studies have investigated stratified flows for atmospheric and oceanic flows, and a number of studies have investigated turbulent stratified flows in idealized valleys. However, dynamical stability of stably stratified flows in idealized valleys has not received any attention despite its significance to elucidate the underlying flow physics. Thus, the chief goal of this research is to investigate and characterize the dynamical stability of stratified flows in idealized valleys. Specifically, this research will focus on stratified anabatic, or up-slope, flows in an idealized V-shaped valley, providing a parallel to the morning transition period, as well as to previous experimental studies. This goal will be achieved through the use of linear stability analysis to uncover primary and secondary instabilities, and direct numerical simulations to track the nonlinear evolution of these instabilities. The proposed research will adopt a new set of dimensionless parameters to characterize the flow states and to determine the dependence on each parameter. Finally, the key findings of the proposed research will be extended to existing field data to establish practical uses in meteorology. A comprehensive understanding of stratified flows in valleys, specifically during morning transitions, is expected at the completion of the proposed research. 

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Link: https://pitt.zoom.us/j/97263901250 ;

Passcode: 157567 

Meeting ID: 972 6390 1250