573 research outputs found
Numerical analysis of flux footprints for different landscapes
No full textA model for the canopy - planetary boundary layer flow and scalar transport based on E-is an element of closure was applied to estimate footprint for CO2 fluxes over different inhomogeneous landscapes. Hypothetical heterogeneous vegetation patterns - forest with clear-cuts as well as hypothetical heterogeneous relief - a bell-shaped valley and a ridge covered by forest were considered. The distortions of airflow caused by these heterogeneities are shown - the upwind deceleration of the flow at the ridge foot and above valley, acceleration at the crest and the flow separation with the reversed flow pattern at lee slopes of ridge and valley. The disturbances induce changes in scalar flux fields within the atmospheric surface layer comparing to fluxes for homogeneous conditions: at a fixed height the fluxes vary as a function of distance to disturbance. Correspondingly, the flux footprint estimated from model data depends oil the location of the point of interest (flux measurement point) and may significantly deviate from that for a flat terrain. It is shown that proposed method could be used for the choice of optimal sensor position for flux measurements over complex terrain as well as for the interpretation of data for existing measurement sites. To illustrate the latter the method was applied for experimental site in Selling, Germany, taking into account the complex topography and vegetation heterogeneities. Results show that in certain situations (summer, neutral stratification, south or north wind) and for a certain sensor location the assumptions of idealized air flow structure could be used for measurement interpretation at this site, though in general, extreme caution should be applied when analytical footprint models are used in the interpretation of flux measurements over complex sites
Does increased spatial replication above heterogeneous agroforestry improve the representativeness of eddy covariance measurements?
No full textDoes increased spatial replication above heterogeneous agroforestry improve the representativeness of eddy covariance measurements?
No full textSpatial heterogeneity in terrestrial ecosystems compromises the accuracy of eddy covariance measurements. An example of heterogeneous ecosystems are temperate agroforestry systems, that have been poorly studied by eddy covariance. Agroforestry systems get an increasing attention due to their potential environmental benefits, e.g. a higher carbon sequestration, enhanced microclimate and erosion reduction compared to monocropping agricultural systems. Lower-cost eddy covariance setups might offer an opportunity to reduce this bias by allowing for more spatial replicates of flux towers. The aim of this study was to quantify the spatial variability of carbon dioxide (FC), latent heat (LE) and sensible heat (H) fluxes above a heterogeneous agroforestry system in northern Germany using a distributed network of three lower-cost eddy covariance setups across the agroforestry systems. Fluxes from the three towers in the agroforestry were further compared to fluxes from an adjacent monocropping site. The campaign took place from March 2023 until September 2024. The results indicated that the spatial variability of fluxes was largest for FC, attributed to the effect of different crops (rapeseed, corn and barley) within the flux footprints contributed to the measured fluxes. Differences between fluxes across towers were enhanced after harvest events. However, the temporal variability due to the seasonality and diurnal cycles during the campaign was larger than the spatial variability across the three towers. When comparing fluxes between the agroforestry and the monocropping systems, weekly sums of carbon and evapotranspiration fluxes followed similar seasonality, with peak values during the growing season of-50 g C m−2 week−1 and 40 mm week−1, respectively. The variation of the magnitude depended on the phenology of the different crops. The effect size, which is an indicator of the representativeness of the fluxes across the distributed network of three eddy covariance towers against only one, showed in conjunction with the other results that the spatial heterogeneity across the agroforestry was better captured by the network of three stations. This supports previous findings that spatial heterogeneity should be taken into account in eddy covariance studies, and that lower-cost setups may offer the opportunity to bridge this gap and improve the accuracy of eddy covariance measurements above heterogeneous ecosystems
Rating targeting and the confidence levels implicit in bank capital
No full textThe solvency standards implicit in bank capital levels, as reported eg in Jackson et al (2002), are much higher than those required for top ratings, if standard single period economic capital models are taken se-riously. We explain this excess capital puzzle by forward looking rating targeting behaviour by banks, which aims at maintaining rating above a minimum target in future periods. We calibrate to data on actual bank capital the confidence level used by the median US AA rated bank to maintain at least a single A rating. The calibrated confidence level is in line with the historical probability of an AA rated bank to be downgraded below A.bank capital; credit rating; value-at-risk; economic capital; capital structure
The effect of lenders’ credit risk transfer activities on borrowing firms’ equity returns
No full textAlthough innovative credit risk transfer techniques help to allocate risk more optimally, policymakers worry that they may detrimentally affect the effort spent by financial intermediaries in screening and mo-nitoring credit exposures. This paper examines the equity market’s response to loan announcements. In common with the literature it reports a significantly positive average excess return – the well known ‘bank certification’ effect. However, if the lending bank is known to actively manage its credit risk ex-posure through large-scale securitization programmes, the magnitude of the effect falls by two thirds. The equity market does not appear to place any value on news of loans extended by banks that are known to transfer credit risk off their books.bank loans; credit derivatives; bank certification
Why do capital intensive companies pay higher wages?
No full textAn obvious answer to this question is the capital-skill complementarity hypothesis originally proposed by Zwi Griliches (1969). But the relatively poor performance of this hypothesis suggests that other explanations are needed. Here we consider the labour union behaviour in the wage bargaining process as such an alternative. The explanation is based on the observation that capital intensive companies are more vulnerable to strike threats and may thus more easily give in for union wage demand. Thus, the bargaining power of unions is related to the capital-labour ratio. This paper provides some tests for these hypotheses with panel data for Finnish companies. The results give support to the wage bargaining hypothesis.wages, bargaining, wage distribution, panel data
GDP at risk in a DSGE model: an application to banking sector stress testing
No full textWe suggest a complementary tool for financial stability analysis based on stochastic simulation of a dynamic stochastic general equilibrium model (DSGE) of the macro economy. The paper relates to financial stability research in which financial aggregates crucial to financial stability are modelled as functions of macroeconomic variables. In these models, stress tests for eg banking sector loan losses can be generated by considering adverse scenarios of macro variables. A DSGE model provides a systematic way of generating coherent macro scenarios which can be given a rigorous economic interpretation. The approach is illustrated using a DSGE model of the Finnish economy and a simple model of Finnish banking sector loan losses.DSGE models; financial stability; loan losses; stress testing
Technical note: Comparison of methane ebullition modelling approaches used in terrestrial wetland models
No full textEmission via bubbling, i.e. ebullition, is one of the main methane (CH4)
emission pathways from wetlands to the atmosphere. Direct measurement of gas
bubble formation, growth and release in the peat–water matrix is challenging
and in consequence these processes are relatively unknown and are coarsely
represented in current wetland CH4 emission models. In this study we
aimed to evaluate three ebullition modelling approaches and their effect on
model performance. This was achieved by implementing the three approaches in
one process-based CH4 emission model. All the approaches were based on
some kind of threshold: either on CH4 pore water concentration (ECT),
pressure (EPT) or free-phase gas volume (EBG) threshold. The model was run
using 4 years of data from a boreal sedge fen and the results were
compared with eddy covariance measurements of CH4 fluxes.Modelled annual CH4 emissions were largely unaffected by the different
ebullition modelling approaches; however, temporal variability in CH4
emissions varied an order of magnitude between the approaches. Hence the
ebullition modelling approach drives the temporal variability in modelled
CH4 emissions and therefore significantly impacts, for instance,
high-frequency (daily scale) model comparison and calibration against
measurements. The modelling approach based on the most recent knowledge of
the ebullition process (volume threshold, EBG) agreed the best with the
measured fluxes (R2 = 0.63) and hence produced the most reasonable
results, although there was a scale mismatch between the measurements
(ecosystem scale with heterogeneous ebullition locations) and model results
(single horizontally homogeneous peat column). The approach should be
favoured over the two other more widely used ebullition modelling approaches
and researchers are encouraged to implement it into their CH4 emission
models
Central bank liquidity operations during the financial market and economic crisis: observations, thoughts and questions
No full textThe paper concentrates on illustrating and assessing central banks’ liquidity operations during the crisis that started in August 2007. In addition to the ECB, the central banks of Sweden, Switzerland, the United Kingdom, Australia, Japan, Canada and the United States are analyzed. During the crisis the liquidity operations of central banks have converged. In many cases, central bank balance sheets have undergone extremely strong growth. The actions by central banks raise a number of questions concerning exit from the measures taken, the impact of the measures, central banks’ risks and their governance structure.central banks; liquidity operations; balance sheets
Asymmetric Information in Credit Markets and Entrepreneurial Risk Taking
No full textThe paper constructs a search-theoretic model of credit markets with a bilateral trading mechanism that enables the manageable introduction of asymmetric information.Borrowers success probabilities are unobservable to financiers, but the degree of risk in observable projects can be used as a sorting device.We find that the efficiency of a perfect Bayesian equilibrium depends negatively/ positively on the credit market tightness /liquidity. In general equilibrium, where the underlying market conditions are endogenously determined, steady states with greater credit market tightness are always associated with increasingly excessive investment in risky projects.Since tighter market conditions also imply less intense competition among financiers, the commonly asserted trade-off between competition and efficiency does not emerge.Tighter monetary policy is shown to worsen the adverse effect of informational frictions on efficiency
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