Trade Costs, Quality, and The Skill Premium

We develop a monopolistic competition model with nonhomothetic factor input bundles where increasing quality requires increasing use of skilled workers. As a result more skill abundant countries export higher quality, higher priced goods. Using a multicountry dataset we test and confirm the findings in Schott (2004) of a positive effect of skill abundance on unit values identified with US data. We extend the core model with per unit trade costs leading to the Washington-apples effect that goods shipped over larger distance are of higher quality. The combination of high-quality goods being relatively skill intensive with the Washington-apples effect implies that countries at a larger distance from their trading partners display a higher skill premium. Simulating our model we find that a doubling of distance of a country relative to all its trading partners raises the skill premium in a country by about 2.3 percent.

Calibrating a CGE model with NTBs that Incorporates Standard Models of Modern Trade Theory

We propose a way to incorporate NTBs for the four workhorse models of the modern trade literature in computable general equilibrium models (CGEs). CGE models feature intermediate linkages and thus allow us to study global value chains (GVCs). We show that the Ethier-Krugman monopolistic competition model, the Melitz firm heterogeneity model and the Eaton and Kortum model can be defined as an Armington model with generalized marginal costs, generalized trade costs and a demand externality. As already known in the literature in both the Ethier-Krugman model and the Melitz model generalized marginal costs are a function of the amount of factor input bundles. In the Melitz model generalized marginal costs are also a function of the price of the factor input bundles. Lower factor prices raise the number of firms that can enter the market profitably (extensive margin), reducing generalized marginal costs of a representative firm. For the same reason the Melitz model features a demand externality: in a larger market more firms can enter. We implement the different models in a CGE setting with multiple sectors, intermediate linkages, non-homothetic preferences and detailed data on trade costs. We find the largest welfare effects from trade cost reductions in the Melitz model. We also employ the Melitz model to mimic changes in Non tariff Barriers (NTBs) with a fixed cost-character by analysing the effect of changes in fixed trade costs. While we work here with a model calibrated to the GTAP database, the methods developed can also be applied to CGE models based on the WIOD database.

Turbulent flux and meteorological measurements during ARCTEX-2006 campaign

This dataset present result from the DFG- funded Arctic-Turbulence-Experiment (ARCTEX-2006) performed by the University of Bayreuth on the island of Svalbard, Norway, during the winter/spring transition 2006. From May 5 to May 19, 2006 turbulent flux and meteorological measurements were performed on the monitoring field near Ny-Ålesund, at 78°55'24'' N, 11°55'15'' E Kongsfjord, Svalbard (Spitsbergen), Norway. The ARCTEX-2006 campaign site was located about 200 m southeast of the settlement on flat snow covered tundra, 11 m to 14 m above sea level. The permanent sites used for this study consisted of the 10 m meteorological tower of the Alfred Wegener Institute for Polar- and Marine Research (AWI), the international standardized radiation measurement site of the Baseline Surface Radiation Network (BSRN), the radiosonde launch site and the AWI tethered balloon launch sites. The temporary sites - set up by the University of Bayreuth - were a 6 m meteorological gradient tower, an eddy-flux measurement complex (EF), and a laser-scintillometer section (SLS). A quality assessment and data correction was applied to detect and eliminate specific measurement errors common at a high arctic landscape. In addition, the quality checked sensible heat flux measurements are compared with bulk aerodynamic formulas that are widely used in atmosphere-ocean/land-ice models for polar regions as described in Ebert and Curry (1993, doi:10.1029/93JC00656) and Launiainen and Cheng (1995). These parameterization approaches easily allow estimation of the turbulent surface fluxes from routine meteorological measurements. The data show: - the role of the intermittency of the turbulent atmospheric fluctuation of momentum and scalars, - the existence of a disturbed vertical temperature profile (sharp inversion layer) close to the surface, - the relevance of possible free convection events for the snow or ice melt in the Arctic spring at Svalbard, and - the relevance of meso-scale atmospheric circulation pattern and air-mass advection for the near-surface turbulent heat exchange in the Arctic spring at Svalbard. Recommendations and improvements regarding the interpretation of eddy-flux and laser-scintillometer data as well as the arrangement of the instrumentation under polar distinct exchange conditions and (extreme) weather situations could be derived.

Isotopic composition of water in fog, rain, throughfall and stemflow in the Monte Verde, Costa Rica

Fog deposition, precipitation, throughfall and stemflow were measured in a windward tropical montane cloud forest near Monteverde, Costa Rica, for a 65-day period during the dry season of 2003. Net fog deposition was measured directly using the eddy covariance (EC) method and it amounted to 1.2 ± 0.1 mm/day (mean ± standard error). Fog water deposition was 5-9% of incident rainfall for the entire period, which is at the low end of previously reported values. Stable isotope concentrations (d18O and d2H) were determined in a large number of samples of each water component. Mass balance-based estimates of fog deposition were 1.0 ± 0.3 and 5.0 ± 2.7 mm/day (mean ± SE) when d18O and d2H were used as tracer, respectively. Comparisons between direct fog deposition measurements and the results of the mass balance model using d18O as a tracer indicated that the latter might be a good tool to estimate fog deposition in the absence of direct measurement under many (but not all) conditions. At 506 mm, measured water inputs over the 65 days (fog plus rain) fell short by 46 mm compared to the canopy output of 552 mm (throughfall, stemflow and interception evaporation). This discrepancy is attributed to the underestimation of rainfall during conditions of high wind.

Parameters of the near-bottom nepheloid layer off the northwestern Africa coast

Vertical profiles of light scattering at a right angle and turbidity profiles in seawater indicating suspended matter concentration in the near-bottom nepheloid layer (NNL) were measured simultaneously with temperature, salinity, and density profiles at the continental slope off the northwestern Africa. About 100 stations 5' apart in latitude and longitude were carried out over an ocean area of 6100 sq. km. Special features of the NNL variability in the area were analyzed. It was found that some structural parameters of the NNL (maximum transparency depth, that is the upper boundary of NNL; NNL thickness; maximum and total turbidity) correlate with ocean depth. On the average, thickness of the NNL in the area is 20-40% of the ocean depth. At most stations the NNL is fairly strong. In the shelf region NNL turbidity was influenced by the intensive near-shore upwelling. Formation of ''high-energy near-bottom layers'' in the shelf region resulted from passing of a mesoscale cyclonic eddy that caused redistribution of measured quantities within the entire water column.

ERA-interim reanalysis debiased at FLUXNET sites

(preliminary) Exchanges of carbon, water and energy between the land surface and the atmosphere are monitored by eddy covariance technique at the ecosystem level. Currently, the FLUXNET database contains more than 500 sites registered and up to 250 of them sharing data (Free Fair Use dataset). Many modelling groups use the FLUXNET dataset for evaluating ecosystem model's performances but it requires uninterrupted time series for the meteorological variables used as input. Because original in-situ data often contain gaps, from very short (few hours) up to relatively long (some months), we develop a new and robust method for filling the gaps in meteorological data measured at site level. Our approach has the benefit of making use of continuous data available globally (ERA-interim) and high temporal resolution spanning from 1989 to today. These data are however not measured at site level and for this reason a method to downscale and correct the ERA-interim data is needed. We apply this method on the level 4 data (L4) from the LaThuile collection, freely available after registration under a Fair-Use policy. The performances of the developed method vary across sites and are also function of the meteorological variable. On average overall sites, the bias correction leads to cancel from 10% to 36% of the initial mismatch between in-situ and ERA-interim data, depending of the meteorological variable considered. In comparison to the internal variability of the in-situ data, the root mean square error (RMSE) between the in-situ data and the un-biased ERA-I data remains relatively large (on average overall sites, from 27% to 76% of the standard deviation of in-situ data, depending of the meteorological variable considered). The performance of the method remains low for the Wind Speed field, in particular regarding its capacity to conserve a standard deviation similar to the one measured at FLUXNET stations.

Barium in seawater and sediments from the Artic Ocean

As part of ongoing circulation studies in the Arctic, seawater samples for dissolved Ba concentrations were obtained during Sep.-Oct., 1992 at several locations in the Bering Strait, Eastern Chukchi and Southern Beaufort Seas. The results reveal a dynamic rang (10 to 150 nmol/kg) for this element in the Arctic equal to or greater than that in combined Atlantic, Indian and Pacific oceans. Lowest levels are observed in surface waters, with values tending to decrease northwards in the direction of currents generally flowing frorn the Bering Strait along the Alaskan coast. Low surfacc concentrations tend to be accompanied by relatively enriched near bottom levels. On the basis of these spatial distributions, hydrographic observations and a knowledge of its behavior in other marine settings, it appears that Ba can be significantly depleted from surface waters as a result of the highly seasonal biological aclivities over Arctic marginal shelves. Removal at the surface is counteracted to some extent by regeneration at depth or in the sediments and by riverine inputs. The biologically related drawdown is likely to enhance the contrast between 'background' surface Ba levels in the Arctic and waters imprinted by regeneration and/or rivers, These preliminary findings suggest that Ba holds particular promise for tracing river waters and the ventilation of halodine waters hy laterally sinking brines produced during ice formation over the shelves.

Particle flux studies of sediment traps from the northern and equatorial Indian Ocean

The Asian monsoon system governs seasonality and fundamental environmental characteristics in the study area from which two distinct peculiarities are most notable: upwelling and convective mixing in the Arabian Sea and low surface salinity and stratification in the Bay of Bengal due to high riverine input and monsoonal precipitation. The respective oceanography sets the framework for nutrient availability and productivity. Upwelling ensures high nitrate concentration with temporal/spatial Si limitation; freshwater-induced stratification leads to reduced nitrogen input from the subsurface but Si enrichment in surface waters. Ultimately, both environments support high abundance of diatoms, which play a central role in the export of organic matter. It is speculated that, additional to eddy pumping, nitrogen fixation is a source of N in stratified waters and contributes to the low-d15N signal in sinking particles formed under riverine impact. Organic carbon fluxes are best correlated to opal but not to carbonate, which is explained by low foraminiferal carbonate fluxes within the river-impacted systems. This observation points to the necessity of differentiating between carbonate sources for carbon flux modeling. As evident from a compilation of previously published and new data on labile organic matter composition (amino acids and carbohydrates), organic matter fluxes are mainly driven by direct input from marine production, except the site off Pakistan where sedimentary input of (marine) organic matter is dominant during the NE monsoon. The explanation of apparently different organic carbon export efficiency calls for further investigations of, for example, food web structure and water column processes.

Concentrations of organic carbon, nitrogen and phosphorus on vertical profiles in waters of the tropical North Atlantic in March 2002

In the literature, an inconsistency exists between estimates of biotically-effected carbon export inferred from large-scale geochemical studies (Jenkins 1982; 47 gC m-2 a-1) and local measurements of turbulent nutrient supply (Lewis et al. 1986; 4 gC m-2 a-1) in the eastern subtropical North Atlantic. Nutrient supply to the upper ocean by turbulent mixing is reexamined using local standard oceanographic measurements and high-resolution vertical profiles of nutrients averaged over a large region directly comparable to that investigated by Jenkins (1982). Turbulent fluxes induced by internal waves and salt fingering, respectively, are separated according to Gregg (1989) and Zhang et al. (1998). Nutrient transport into the nutrient-consuming surface layer by salt fingering is more than fivefold higher than transport due to internal-wave induced turbulence. Still, this cannot resolve the above- mentioned apparent inconsistency, even if additional physical transport mechanisms such as eddy pumping, advection and horizontal diffusion are accounted for. Estimated nitrate fluxes due to vertical turbulent diffusion are 0.05-0.15 mol m-2 a-1, corresponding to 4-11 gC m-2 a-1. Observed NO3/PO4 turbulent flux ratios of up to 23 are interpreted as the imprint of N2 fixation.

Tracer release experiments in the tropical North Atlantic

Lateral diffusivity is computed from a tracer release experiment in the northeastern tropical Atlantic thermocline. The uncertainties of the estimates are inferred from a synthetic particle release using a high-resolution ocean circulation model. The main method employed to compute zonal and meridional components of lateral diffusivity is the growth of the second moment of a cloud of tracer. The application of an areal comparison method for estimating tracer-based diffusivity in the field experiments is also discussed. The best estimate of meridional eddy diffusivity in the Guinea Upwelling region at about 300 m depth is estimated to be inline image m2 s-1. The zonal component of lateral diffusivity is estimated to be inline image m2 s-1, while areal comparison method yields areal equivalent zonal diffusivity component of inline image m2 s?1. In comparison to Ky, Kx is about twice larger, resulting from the tracer patch stretching by zonal jets. Employed conceptual jet model indicates that zonal jet velocities of about inline image m s?1 are required to explain the enhancement of the zonal eddy diffusivity component. Finally, different sampling strategies are tested on synthetic tracer release experiments. They indicate that the best sampling strategy is a sparse regular sampling grid covering most of the tracer patch.