Mass conservation above slopes in the regional atmospheric modelling system (RAMS)

This paper examines the mass balance in calculations with the Regional Atmospheric Modelling System (RAMS). An error is pointed out that concerns the calculation of the surface fluxes on slopes. This error affects all the prognostic variables in RAMS when sloping terrain is involved. Here we explain how the error can be corrected. To study the impact of the error, we compared simulations with the uncorrected and corrected model. The model contains C

A comparison of different inverse carbon flux estimation approaches for application on a regional domain

We have implemented six different inverse carbon flux estimation methods in a regional carbon dioxide (CO<sub>2</sub>) flux modeling system for the Netherlands. The system consists of the Regional Atmospheric Mesoscale Modeling System (RAMS) coupled to a simple carbon flux scheme which is run in a coupled fashion on relatively high resolution (10 km). Using an Ensemble Kalman filter approach we try to estimate spatiotemporal carbon exchange patterns from atmospheric CO<sub>2</sub> mole fractions over the Netherlands for a two week period in spring 2008. The focus of this work is the different strategies that can be employed to turn first-guess fluxes into optimal ones, which is known as a fundamental design choice that can affect the outcome of an inversion significantly. <br><br> Different state-of-the-art approaches with respect to the estimation of net ecosystem exchange (NEE) are compared quantitatively: (1) where NEE is scaled by one linear multiplication factor per land-use type, (2) where the same is done for photosynthesis (GPP) and respiration (<i>R</i>) separately with varying assumptions for the correlation structure, (3) where we solve for those same multiplication factors but now for each grid box, and (4) where we optimize physical parameters of the underlying biosphere model for each land-use type. The pattern to be retrieved in this pseudo-data experiment is different in nearly all aspects from the first-guess fluxes, including the structure of the underlying flux model, reflecting the difference between the modeled fluxes and the fluxes in the real world. This makes our study a stringent test of the performance of these methods, which are currently widely used in carbon cycle inverse studies. <br><br> Our results show that all methods struggle to retrieve the spatiotemporal NEE distribution, and none of them succeeds in finding accurate domain averaged NEE with correct spatial and temporal behavior. The main cause is the difference between the structures of the first-guess and true CO<sub>2</sub> flux models used. Most methods display overconfidence in their estimate as a result. A commonly used daytime-only sampling scheme in the transport model leads to compensating biases in separate GPP and <i>R</i> scaling factors that are readily visible in the nighttime mixing ratio predictions of these systems. <br><br> Overall, we recommend that the estimate of NEE scaling factors should not be used in this regional setup, while estimating bias factors for GPP and <i>R</i> for every grid box works relatively well. The biosphere parameter inversion performs good compared to the other inversions at simultaneously producing space and time patterns of fluxes and CO<sub>2</sub> mixing ratios, but non-linearity may significantly reduce the information content in the inversion if true parameter values are far from the prior estimate. Our results suggest that a carefully designed biosphere model parameter inversion or a pixel inversion of the respiration and GPP multiplication factors are from the tested inversions the most promising tools to optimize spatiotemporal patterns of NEE

Global land-surface evaporation estimated from satellite-based observations

This paper outlines a new strategy to derive evaporation from satellite observations. The approach uses a variety of satellite-sensor products to estimate daily evaporation at a global scale and 0.25 degree spatial resolution. Central to this methodology is the use of the Priestley and Taylor (PT) evaporation model. The minimalistic PT equation combines a small number of inputs, the majority of which can be detected from space. This reduces the number of variables that need to be modelled. Key distinguishing features of the approach are the use of microwave-derived soil moisture, land surface temperature and vegetation density, as well as the detailed estimation of rainfall interception loss. The modelled evaporation is validated against one year of eddy covariance measurements from 43 stations. The estimated annual totals correlate well with the stations' annual cumulative evaporation (<i>R</i>=0.80, <i>N</i>=43) and present a low average bias (−5%). The validation of the daily time series at each individual station shows good model performance in all vegetation types and climate conditions with an average correlation coefficient of <i><span style="text-decoration: overline">R</span></i>=0.83, still lower than the <i><span style="text-decoration: overline">R</span></i>=0.90 found in the validation of the monthly time series. The first global map of annual evaporation developed through this methodology is also presented

Atmospheric CO2 modeling at the regional scale: an intercomparison of 5 meso-scale atmospheric models

Atmospheric CO2 modeling in interaction with the surface fluxes, at the regional scale is developed within the frame of the European project CarboEurope-IP and its Regional Experiment component. In this context, five meso-scale meteorological models participate in an intercomparison exercise. Using a common experimental protocol that imposes a large number of rules, two days of the CarboEurope Regional Experiment Strategy (CERES) campaign are simulated. A systematic evaluation of the models is done in confrontation with the observations, using statistical tools and direct comparisons. Thus, temperature and relative humidity at 2 m, wind direction, surface energy and CO2 fluxes, vertical profiles of potential temperature as well as in-situ CO2 concentrations comparisons between observations and simulations are examined. This intercomparison exercise shows also the models ability to represent the meteorology and carbon cycling at the synoptic and regional scale in the boundary layer, but also points out some of the major shortcomings of the models

An assessment of the potential for atmospheric emission verification in The Netherlands

Doel van dit project was het ontwikkelen van een systeem voor het kwantificeren van het broeikasgasbudget op landelijke en regionale schaal. Het ME2 consortium heeft een ‘protocol’ ontwikkeld om een referentieschatting te maken ten behoeve van de verificatie van nationale emissies. Daarmee is het op termijn mogelijk de nauwkeurigheid en geloofwaardigheid van aan UNFCCC en Kyoto gerapporteerde emissies, en reducties daarvan, te verifiëren. Met verschillende inversie methoden, van data tot model gedreven, zijn emissieschattingen gemaakt. De data gedreven methoden kunnen schattingen maken voor alle drie de broeikasgassen voor NL als geheel en zijn representatief voor meerdere jaren. Met de meer model gedreven inversies zijn meer ruimtelijk en temporeel gedistribueerde schattingen te maken

Solving the production- diffusion equatation for finite diffusion domains of the various shapes, part 1; implications for low temperature (U-Th) /He thermochronology

We propose an accurate, fast and easy-to-use method to derive numerical solutions for production-diffusion equations for finite diffusion domains of various shapes and arbitrary cooling histories. Previous studies provide solutions for spheres, infinite cylinders and infinite sheets. We extend this range and provide solutions for finite bodies, i.e. finite cylinders and rectangular blocks of any aspect ratio. This approach is important as recently, it has become clear that, for example, the physical grain is the diffusion domain for He diffusion in apatite and titanite [J. Geophys. Res. 105 (2000) 2903; Geochim. Cosmochim. Acta 63 (1999) 3845]. We discuss the use of the new approach for forward modelling (U-Th)/He production-diffusion in apatite. Taking results with finite cylinders as a good approximation for apatite crystals, it is found that approximating instead with spheres or infinite cylinders having the same radius yields differences in calculated ages that can easily be as large as 20-35%. The relative differences are most pronounced in thermal histories that spend significant time at or near the closure temperature. On the other hand, reasonable agreement is found with spheres having the same surface to volume ratio. © 2002 Elsevier Science B.V. All rights reserved

A non-iterative solution of the (U-Th)/He equation

We present a direct solution of the (U-Th)/He age equation for age that obviates the need for an iterative solution. The uncertainties of this solution are sufficiently small to allow its use as a quasi-analytical solution of this age equation. The direct algorithm has the obvious advantage of greater simplicity. Moreover inversion algorithms for (U-Th)/He age profiles and coupled three-dimensional thermal-age-landscape models will profit from the resulting gain in computational speed. Copyright 2005 by the American Geophysical Union

Salinization processes in paleowaters in coastal sediments of Suriname: evidence from 37Cl analysis and diffusion modelling.

In the coastal plain of Suriname a stagnant body of fresh (<250 mg/l Cl) and moderately brackish (250-1000 mg/l Cl) groundwater of meteoric origin is found in permeable Tertiary formations. This groundwater body, formed during the last Wisconsin regression, extends offshore into deposits on the continental shelf. The authors found that this paleowater is slowly being salinized by downward solute transport from overlying Holocene marine clays and upward transport from saline Cretaceous sediments. The downward transport has been studied at two sites by relating analyses of chloride contents an