Browsing by Author "Wei, Wei"
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Item Open Access Essays on Debt Maturity(2014) Wei, WeiI study firms' debt maturity decisions. I provide two models for optimal debt maturity choices when facing stochastic productivity and rollover risk. The first model is based on firms' need to smooth their capital when facing uncertainties in external financing. When the capital market freezes, new external financing is difficult. Firms with large debt repayments due have to forego good investment opportunities and in severe cases cut back on dividends. Long-term debt reduces immediate repayments and allows firms to keep the borrowed capital for future production. Therefore, when freezes are likely, firms respond by using more long-term financing and are better prepared. However, when the probability of freezes is low, firms turn to short-term financing. When a freeze suddenly occurs, the impact is significant and costly. The model predicts that constrained firms use more short-term debt. Based on the model, I propose investment-debt sensitivity as a new measure for financial constraints.
The second model depicts an economy in which entrepreneurs reallocate capital resources through borrowing and lending in either short-term or long-term debt. In expansions, productivity is more persistent and uncertainty in productivity is low, so entrepreneurs can better predict their future prospects. Hence, they choose to use more long-term debt to finance their productions. In recessions, future prospects are less clear to the entrepreneurs; therefore, they choose to use more short-term debt. The model explains the documented facts on pro-cyclical debt maturity in the economy. It also highlights that the shortening debt maturity structure causes capital resources to be less efficiently allocated in recessions further exacerbates the bad times. I argue that the change in the predictability of TFP drives pro-cyclical debt maturity, and that the maturity structure further amplifies the fluctuations in aggregate production.
Item Open Access Intraseasonal variation of the summer rainfall over the Southeastern United States(Climate Dynamics, 2018-07-06) Wei, Wei; Li, Wenhong; Deng, Yi; Yang, Song© 2018 Springer-Verlag GmbH Germany, part of Springer Nature This study characterizes the intraseasonal variability (ISV) in the Southeastern United States (SE US) rainfall in boreal summer and delineates the associated dynamical processes featuring three-way interactions among the SE US rainfall, the central US low-level jet (LLJ), and the North Atlantic subtropical high (NASH). The analysis reveals that the ISV of the SE summer rainfall peaks at the 10‒20-day timescales. The physical mechanisms for the three-way interactions on the 10‒20-day timescales are proposed. When the NASH attains a minimum strength, the reduced size of the NASH is accompanied with an eastward retreat of the western ridge of the NASH, leading to a decrease in the zonal pressure gradient and consequently a weakening of the LLJ 1 day after. The weakened LLJ and the eastward-shifted NASH western ridge induces anomalous cyclonic circulation over the SE US, moves preferred regions of moisture convergence from central US to the SE US, and 3 days later the SE US rainfall attains its maximum strength. The excessive latent heating associated with the enhanced SE US rainfall excites an anomalous anticyclone northeast of the rainfall region, resulting in an increase in the NASH intensity that peaks 2 days after the maximum SE US rainfall. The NASH subsequently expands with its western ridge moving westward, zonal pressure gradient restored, and LLJ strength recovered. An anomalous anticyclone then emerges over the SE US and suppresses rainfall, marking the shift from an intraseasonal wet phase to dry phase in this region. A more rigorous proof of these causalities demand carefully designed numerical experiments and further statistical analysis in future. Our results suggest that improved prediction of SE US summer rainfall across intraseasonal scales depends critically on the model representation of the three-way coupling among the NASH, the central US LLJ, and the SE US rainfall.