Depth dependence of westward-propagating North Atlantic features diagnosed from altimetry and a numerical 1/6° model

International audienceA 1/6° numerical simulation is used to investigate the vertical structure of westward propagation between 1993 and 2000 in the North Atlantic ocean. The realism of the simulated westward propagating signals, interpreted principally as the signature of first-mode baroclinic Rossby waves (RW), is first assessed by comparing the simulated amplitude and zonal phase speeds of Sea Level Anomalies (SLA) against TOPEX/Poseidon-ERS satellite altimeter data. Then, the (unobserved) subsurface signature of RW phase speeds is investigated from model outputs by means of the Radon Transform which was specifically adapted to focus on first-mode baroclinic RW. The analysis is performed on observed and simulated SLA and along 9 simulated isopycnal displacements spanning the 0-3250 m depth range. Simulated RW phase speeds agree well with their observed counterparts at the surface, although with a slight slow bias. Below the surface, the simulated phase speeds exhibit a systematic deceleration with increasing depth, by a factor that appears to vary geographically. Thus, while the reduction factor is about 15-18% on average at 3250 m over the region considered, it appears to be much weaker (about 5-8%) in the eddy-active Azores Current, where westward propagating structures might be more coherent in the vertical. In the context of linear theories, these results question the often-made normal mode assumption of many WKB-based theories that the phase speed is independent of depth. Alternatively, these results could also suggest that the vertical structure of westward propagating signals may significantly depend on their degree of nonlinearity, with the degree of vertical coherence possibly increasing with the degree of nonlinearity

Testing For Financial Contagion Between Developed And Emerging Markets During The 1997 East Asian Crisis

In this paper we examine whether during the 1997 East Asian crisis there was any contagion from the four largest economies in the region (Thailand, Indonesia, Korea and Malaysia) to a number of developed countries (Japan, UK, Germany and France). Following Forbes and Rigobon (2002), we test for contagion as a significant positive shift in the correlation between asset returns, taking into account heteroscedasticity and endogeneity bias. Furthermore, we improve on earlier empirical studies by carrying out a full sample test of the stability of the system that relies on more plausible (over)identifying restrictions. The estimation results provide some evidence of contagion, in particular from Japan (the major international lender in the region), which drastically cut its credit lines to the other Asian countries in 1997

Comparing Allelopathic Effects of Root and Leaf Extracts of Invasive Alliaria petiolata, Lonicera maackii and Ranunculus ficaria on Germination of Three Native Woodland Plants

Author Institution: Department of Biology, Wilmington College, Wilmington, OhioInvasive plant species can exhibit allelopathic effects on native plant species. The strength of this allelopathic effect can vary with invasive species, with target species and with type of plant tissue extract. The purpose of this study was to determine the direct effects of extracts from roots or leaves of three Midwestern US invasive plants (Alliaria petiolata, Lonicera maackii and Ranunculus ficaria) on the germination success of three native target species (Anemone virginiana, Blephilia hirsuta and Elymus hystrix) in a fully factorial experiment. Leaf extract treatments overall showed more germination inhibition compared to root extract treatments. As concentration increased, effects of extracts increased. Extracts of leaves of A. petiolata had the greatest inhibition of germination across all other treatments. Effects of root and leaf extracts of each invasive species varied with each target species. While E. hystrix showed little response to extracts of roots or leaves of L. maackii and R. ficaria, B. hirsuta and A. virginiana germination were reduced by leaf extracts of these two invasive species. This study confirms the strong direct allelopathic effects of A. petiolata, though the strength of the effect varies with target species and with type of tissue used to make extracts. This study is the first to directly compare the effects of these invasive species on a suite of native, ecologically-relevant target species

Testing for public debt sustainability using a time-scale decomposition analysis

In this paper we estimate the response of primary surplus to lagged debt to test for debt sustainability within the 17 EMU countries by using a factor model. The analysis is split into two stages. In the first stage we retrieve the cyclical and long-run components of primary surplus and debt ratios of each EMU country using a wavelet decomposition for each fiscal covariate, based on the Maximal Overlapping Discrete Wavelet Transform. In the second stage, we use Full Information Maximum Likelihood for a factor decomposition of thecross covariance matrix of the wavelet coefficients of primary deficit and debt to GDP ratios in order to measure the short run and the long run reaction of the primary surplus to (lagged) debt. The empirical evidence shows a positive response of primary surplus to debt within EMU as a whole. Country specific factor decomposition confirms Germany as the one of the most virtuous countries, and, Italy, as the only PIIGS member on a long-run sustainable path for deb

Variation in Resistance of Experienced and Naïve Seedlings of Jewelweed (Impatiens capensis) to Invasive Garlic Mustard (Alliaria petiolata)

Author Institution: Wilmington CollegeThe invasive species garlic mustard, Alliaria petiolata, has negative impacts on understory forest species in the Midwest. Plants that coexist with A. petiolata in the field may show resistance to its negative effects as a result of natural selection. In a growth room experiment, we investigated if naïve and experienced seedlings of impatiens capensis vary in their response to the presence of A. petiolata. Impatiens capensis individuals from areas without A. petiolata (i.e., naïve plants) and from nearby areas with A. petiolata (i.e., experienced plants) were collected from the field and were then grown with A. petiolata in pots for 16 weeks. We measured height, stem diameter, reproduction and biomass of I. capensis and biomass of A. petiolata. There was a significant (P < 0.05) negative correlation between biomass and height of naïve I. capensis and biomass of A. petiolata, while there was no significant correlation between these variables for experienced I. capensis. Our results indicate the potential for the evolution of resistance to the presence of A. petiolata in I. capensis and point toward the need for further studies

Volatility co-movements: a time scale decomposition analysis

In this paper we investigate short-run co-movements before and after the Lehman Brothers\u2019 collapse among the volatility series of US and a number of European countries. The series under investigation (implied and realized volatility) exhibit long-memory and, in order to avoid miss-specification errors related to the parameterization of a long memory multivariate model, we rely on wavelet analysis. More specifically, we retrieve the time series of wavelet coefficients for each volatility series for high frequency scales, using the Maximal Overlapping Discrete Wavelet transform and we apply Maximum Likelihood for a factor decomposition of the short-run covariance matrix. The empirical evidence shows an increased interdependence in the post-break period and points at an increasing (decreasing) role of the common shock underlying the dynamics of the implied (realized) volatility series, once we move from the 2-4 days investment time horizon to the 8-16 days. Moreover, there is evidence of contagion from the US to Europe immediately after the Lehman Brothers\u2019 collapse, only for realized volatilities over an investment time horizon between 8 and 16 days

ALTICORE: an initiative for coastal altimetry

ALTICORE (value-added ALTImetry for COastal REgions) is an international initiative whose main objective is to encourage the operational use of altimetry over coastal areas, by improving the quality and availability of coastal altimetry data. The ALTICORE proposal has recently been submitted for funding to the INTAS scheme (www.intas.be) by a consortium of partners from Italy, France, UK, Russia and Azerbaijan. ALTICORE is also meant as a contribution to the ongoing International Altimeter Service effort. In this work we will describe the anticipated project stages, namely: 1) improvement of the most widely distributed, 1 Hz, data by analyzing the corrective terms and providing the best solutions, including those derived from appropriate local modelling; 2) development of a set of algorithms to automate quality control and gap-filling functions for the coastal regions; 3) development of testing strategies to ensure a thorough validation of the data. The improved products will be delivered to ALTICORE users via Grid-compliant technology; this makes it easier to integrate the local data holdings, allows access from a range of services, e.g. directly into model assimilation or GIS systems and should therefore facilitate a widespread and complete assessment of the 1Hz data performance and limitations. We will also outline the design and implementation of the Grid-compliant system for efficient access to distributed archives of data; this consists of regional data centres, each having primary responsibility for regional archives, local corrections and quality control, and operating a set of web-services allowing access to the full functionality of data extraction. We will conclude by discussing a follow-on phase of the project; this will investigate further improvements on the processing strategy, including the use of higher frequency (10 or 20 Hz) data. Phenomena happen at smaller spatial scales near the coast, so this approach is necessary to match the required resolution. The whole project will hopefully promote the 15-year sea surface height from altimetry to the rank of operational record for the coastal areas

Housing Market Shocks in Italy: a GVAR Approach

In this paper, we use a Global Vector Autoregression (GVAR) model to assess the spatio-temporal mechanism of house price spillovers, also known as “ripple effect”, among 93 Italian provincial housing markets, over the period 2004 − 2016. In order to better capture the local housing market dynamics, we use data not only on house prices but also on transaction volumes. In particular, we focus on estimating, to what extent, exogenous shocks, interpreted as negative housing demand shocks, arising from 10 Italian regional capitals, impact on their house prices and sales and how these shocks spill over to neighbours housing markets. The negative housing market demand shock hitting the GVAR model is identified by using theory-driven sign restrictions. The spatio-temporal analysis carried through impulse response functions shows that there is evidence of a “ripple effect” mainly occurring through transaction volumes

Climate risk and investment in equities in Europe: a Panel SVAR approach

In this study, we use data on European stocks to construct a green-minus-brown portfolio hedging climate risk and to evaluate its performance in terms of cumulative expected and unexpected returns. More specifically, we estimate a Structural Panel VAR fitted to one month return and realized volatility computed for 40 constituents of a green portfolio (i.e., the low carbon emission portfolio monitored by Refinitiv) and for 41 constituents of a brown portfolio (underlying the Oil&amp;Gas and Utilities industry sectors of the STOXX Europe 600). The common shocks underlying the cross-sectional averages, interpreted as portfolio shocks, are retrieved in a first stage of the analysis and they are used to control for cross-sectional dependence. We compute the historical decomposition (for cumulative returns) in a second stage of the analysis and we find, in line with P´astor, L., Stambaugh, R. F., &amp; Taylor, L. A. (2022). Dissecting green returns. Journal of Financial Economics, 146 (2), 403–424, an out-performance of the expected component of the brown portfolio relative to the one for the green portfolio, and an out-performance of the green portfolio when we turn our focus on the unexpected component. We also extend the analysis of P´astor et al. (2022), assessing, for the top 5 constituents of the green portfolio (e.g., those which are found to have the worst performance in terms of expected return), the role played by idiosyncratic shocks in shaping their out-performance in terms of unexpected component. Finally, after exploiting the non-gaussian time series properties of the financial time series considered for the purpose of statistical identification, we are able to interpret ex post the idiosyncratic shocks in terms of financial leverage and risk aversion

Leading indicator properties of US high-yield credit spread

In this paper we examine the out-of-sample forecast performance of high-yield credit spreads regarding employment and industrial production in the US, using both a point forecast and a probability forecast exercise. Our main findings suggest the use of few factors obtained by pooling information from a number of sector-specific high-yield credit spreads. This can be justified by observing that there is a gain from using a principal components model fitted to high-yield credit spreads compared to the prediction produced by benchmarks, such as an AR, and ARDL models that use either the term spread or the aggregate high-yield spread as exogenous regressor