A state-dependent parameterization of saturated-unsaturated zone interaction

The relevance of groundwater as an important source of root zone moisture by means of capillary rise is increasingly being recognized. This is partly reflected in many current land surface schemes, which increasingly replace a one-way (i.e., downward) drainage of water by a two-way interaction flux between the root zone and a groundwater system. A fully physically correct implementation of this two-way saturated-unsaturated interaction flux requires transient simulations using the highly nonlinear Richards' equation, which is a computationally demanding approach. We test a classic simple approximation that computes the root zone¿groundwater interaction flux as the net effect of a downward drainage flux and an upward capillary rise flux against the Darcy equation for quasi steady state conditions. We find that for a wet root zone and/or shallow groundwater, the errors within this approximation are significant and of the same magnitude as the interaction flux itself. We present a new closed-form parameterization of the Darcy equation¿based fluxes that accounts both for root zone soil moisture and depth to the water table. Parameter values for this parameterization are listed for 11 different, widely applied soil texture descriptions. The high numerical efficiency of the proposed method makes it suitable for inclusion into demanding applications, e.g., a Monte Carlo framework, or high spatial resolution

Education, growth and income inequality

Estimates of the e¤ect of education on GDP (the social return to education)have been hard to reconcile with micro evidence on the private return. We present a simple explanation that combines two ideas: imperfect substitution between worker types and endogenous skill biased technological progress. When types of workers are imperfect substitutes, the supply of human capital is negatively related to its return, and a higher education level compresses wage di¤erentials. We use cross-country panel data on income inequality to estimate the private return and GDP data to estimate the social return. The results show that the private return falls by 2 percentage points when the average education level increases by a year, which is consistent with Katz and Murphy's [1992] estimate of the elasticity of substitution between worker types. We find no evidence for dynamics in the private return, and certainly not for a reversal of the negative e¤ect as described in Acemoglu [2002]. The short run social return equals the private return.Growth, inequality, education, private and social return to schooling, compression effect

Bivariate colour maps for visualizing climate data

The increasing availability of gridded, high-resolution, multivariate climatological data sets calls for innovative approaches to visualize inter-variable relations. In this study, we present a methodology, based on properties of common colour schemes, to plot two variables in a single colour map by using a two-dimensional colour legend for both sequential and diverging data. This is especially suited for climate data as the spatial distribution of the relation between different variables is often as important as the distribution of variables individually. Two example applications are given to illustrate the use of the method: one that shows the global distribution of climate based on observed temperature and relative humidity, and the other showing the distribution of recent changes in observed temperature and precipitation over Europe. A flexible and easy-to-implement method is provided to construct different colour legends for sequential and diverging data

"The Common Agricultural Policy and the Environmental Challenge – New Tasks for Public Administrations? Summary of Conference Proceedings"

[From the Introduction]. The seminar brought together senior officials from the European Commission, academics, researchers and senior experts from national administrations, who shared their views with 40 participants from all the Member States and the Candidate Countries

Unicellular protein: isolation, techno-functionality and digestibility

Unicellular, photosynthetic microalgae and cyanobacteria are potential new protein sources for both food and feed. Variations between these sources are reflected in chemical variations (e.g. in the chemical composition) and in structural variation (e.g. in cell wall robustness). The aim of this thesis was to understand how chemical and structural variations between unicellular photosynthetic sources affect the application of unicellular protein as techno-functional ingredients and as a fish feed ingredient. To study the applicability of unicellular protein as techno-functional ingredient in food, proteins were extracted and isolated from the cyanobacterium Arthrospira (spirulina) maxima and the microalgae Nannochloropsis gaditana, Tetraselmis impellucida and Scenedesmus dimorphus. Chemical variations observed between photosynthetic unicellular sources were reflected in variations in protein extractability. The isolates (62–77% w/w protein) varied in protein solubility as a function of pH and ionic strength, especially at pH N. gaditana, T. impellucida and A. maxima were able to form emulsions (d3,2 0.2–0.3 µm) at pH 8.0. The amount of each isolate needed to form emulsions varied between the isolates (9–74 mg protein / mL oil), but was within the range of proteins from both similar (photosynthetic) sources (algae and sugar beet leaves) and other protein sources (dairy, legume and egg). Minor differences were observed in the pH dependence of flocculation amongst the isolate stabilized emulsions. To study the applicability of microalgae and cyanobacteria as dietary protein sources for fish, Chlorella vulgaris, S. dimorphus, N gaditana, and A. maxima biomass was incorporated in fish feed (30% inclusion) and fed to Nile tilapia and African catfish. The cell walls of these unicellular sources used were quantified to vary in their robustness to mechanical degradation (structural variations). Although protein digestibility varied between the unicellular sources (ranging from 67–83%), the protein digestibility did not relate to the variations in unicellular cell wall robustness. There was no difference between both fish species regarding the nutrient digestibilities of the unicellular sources. Subjecting N. gaditana biomass to treatments that decrease its cell wall integrity increased in vitro accessibility of microalgae nutrients up to 4 times. The increased in vitro accessibility correlated with an increased in vivo digestibility of protein in Nile tilapia, confirming that nutrient accessibility plays an important role in the nutrient digestibility of microalgae in fish. In conclusion, chemical variations observed between photosynthetic unicellular sources were reflected in variations in protein extractability. Structural variations between the sources were reflected in variations in in vivo protein accessibility and subsequent protein digestibility.</p

Parameter Sensitivity in LSMs: An Analysis Using Stochastic Soil Moisture Models and ELDAS Soil Parameters

Integration of simulated and observed states through data assimilation as well as model evaluation requires a realistic representation of soil moisture in land surface models (LSMs). However, soil moisture in LSMs is sensitive to a range of uncertain input parameters, and intermodel differences in parameter values are often large. Here, the effect of soil parameters on soil moisture and evapotranspiration are investigated by using parameters from three different LSMs participating in the European Land Data Assimilation System (ELDAS) project. To prevent compensating effects from other than soil parameters, the effects are evaluated within a common framework of parsimonious stochastic soil moisture models. First, soil parameters are shown to affect soil moisture more strongly than the average evapotranspiration. In arid climates, the effect of soil parameters is on the variance rather than the mean, and the intermodel flux differences are smallest. Soil parameters from the ELDAS LSMs differ strongly, most notably in the available moisture content between the wilting point and the critical moisture content, which differ by a factor of 3. The ELDAS parameters can lead to differences in mean volumetric soil moisture as high as 0.10 and an average evapotranspiration of 10%–20% for the investigated parameter range. The parsimonious framework presented here can be used to investigate first-order parameter sensitivities under a range of climate conditions without using full LSM simulations. The results are consistent with many other studies using different LSMs under a more limited range of possible forcing condition

Identification of changes in hydrological drought characteristics from a multi-GCM driven ensemble constrained by observed discharge

Peer reviewedPublisher PD