Browsing by Author "Huang, Jing"

Large-scale coherent structures are systematically investigated in terms of their geometric attributes, importance toward describing turbulent exchange of energy, momentum and mass as well as their relationship to landscape features in the context of land-atmosphere interaction. In the first chapter, we present the motivation of this work as well as a background review of large-scale coherent structures in land-atmosphere interaction. In the second chapter, the methodology of large-eddy simulation (LES) and the proper orthogonal decomposition (POD) is introduced. LES was used to serve as a virtual laboratory to simulate typical scenarios in land-atmosphere interaction and the POD was used as the major technique to educe the coherent structures from turbulent flows in land-atmosphere interaction. In the third chapter, we justify the use of the LES to simulate the realistic coherent structures in the atmospheric boundary layer (ABL) by comparing results obtained from LES of the ABL and direct numerical simulation (DNS) of channel flow. In the fourth chapter, we investigate the effects of a wide range of vegetation density on the coherent structures within the air space within and just above the canopy (the so-called canopy sublayer, CSL). The fifth chapter presents an analysis of the coherent structures across a periodic forest-clearing-forest transition in the steamwise direction. The sixth chapter focuses on the role of coherent structures in explaining scalar dissimilarity in the CSL. The seventh chapter summarizes this dissertation and provides suggestions for future study.

Bank stress test has become a centerpiece of post crisis bank supervision. Current studies have thus far examined the optimal policies on stand-alone single banks, but financial systems are interconnected in practice, and disclosure about banks influences the counterparty risks of other banks. This dissertation studies the optimal stress test design in a financial network, where banks' endogenous default outcomes are determined by a fixed point payment problem that accounts for both project qualities and interbank contagion.

The first part examines the joint stress test design on all banks in the financial network. In addition to the cross-state risk sharing in models of single banks, this model highlights the novel cross-bank risk sharing that arises from the spillover effects of disclosures via interbank payments. When expected bank profitability is high or counterparty exposures are large, disclosure is non-discriminatory, and either all banks pass or all banks fail the stress tests; otherwise only less impaired banks may pass. For network structures, I find: (i) in a ring network, banks at least a specific distance away from the nearest bank with asset impairment may pass; (ii) a more connected network is not necessarily more stable under the optimal disclosure; (iii) typically more connected banks receive preferred treatment.

The second part studies a selective stress test in a financial network, where the regulator selects an optimal subset of banks for stress tests and accordingly design the optimal disclosures only on these banks. Compared with the first part, systemic risk becomes more important as the regulator is less able to fine tune beliefs about contagion and needs to contain the risks from unselected banks. For network structures, I find: (i) in a ring network, stress test is either "balanced'' on banks positioned evenly and disclosure is non-discriminatory, or on "connected'' banks and disclosure is truth-telling on potential shocks; (ii) in a star network, stress test is conducted on the center bank when counterparty exposure is either sufficiently small or sufficiently large.