A Three-Dimensional Backward Lagrangian Footprint Model For A Wide Range Of Boundary-Layer Stratifications

We present a three-dimensional Lagrangian footprint model with the ability to predict the area of influence (footprint) of a measurement within a wide range of boundary-layer stratifications and receptor heights. The model approach uses stochastic backward trajectories of particles and satisfies the well-mixed condition in inhomogeneous turbulence for continuous transitions from stable to convective stratification. We introduce a spin-up procedure of the model and a statistical treatment of particle touchdowns which leads to a significant reduction of CPU time compared to conventional footprint modelling approaches. A comparison with other footprint models (of the analytical and Lagrangian type) suggests that the present backward Lagrangian model provides valid footprint predictions under any stratification and, moreover, for applications that reach across different similarity scaling domains (e.g., surface layer to mixed layer, for use in connection with aircraft measurements or with observations on high towers

Interpreting CO2 Fluxes Over a Suburban Lawn: The Influence of Traffic Emissions

Turf-grass lawns are ubiquitous in the United States. However direct measurements of land-atmosphere fluxes using the eddy-covariance method above lawn ecosystems are challenging due to the typically small dimensions of lawns and the heterogeneity of land use in an urbanised landscape. Given their typically small patch sizes, there is the potential that CO2 fluxes measured above turf-grass lawns may be influenced by nearby CO2 sources such as passing traffic. In this study, we report on twoyears of eddy-covariance flux measurements above a 1.5ha turf-grass lawn in which we assess the contribution of nearby traffic emissions to the measured CO2 flux. We use winter data when the vegetation was dormant to develop an empirical estimate of the traffic effect on the measured CO2 fluxes, based on a parametrised version of a three-dimensional Lagrangian footprint model and continuous traffic count data. The CO2 budget of the ecosystem was adjusted by 135gCm−2 in 2007 and by 134gCm−2 in 2008 to determine the natural flux, even though the road crossed the footprint only at its far edge. We show that bottom-up flux estimates based on CO2 emission factors of the passing vehicles, combined with the crosswind-integrated footprint at the distance of the road, agreed very well with the empirical estimate of the traffic contribution that we derived from the eddy-covariance measurements. The approach we developed may be useful for other sites where investigators plan to make eddy-covariance measurements on small patches within heterogeneous landscapes where there are significant contrasts in flux rates. However, we caution that the modelling approach is empirical and will need to be adapted individually to each sit

Playing with the artworks:engaging with art through an augmented reality game

In the majority of cases our experiences of artworks in galleries and museums is as passive observers. While this is widely accepted practice in terms of preserving the artworks it limits the engagement potential with younger visitors. In this paper we present a way of using augmented reality (AR) technology to create engaging and personal art experience for such an audience. To achieve this, we built a prototype for a treasure hunt style game where players colour a contour drawing not knowing what exactly they are colouring. However, they are told that if this coloured drawing is placed correctly, it should wrap around a 3D object (statue) or overlay a 2D canvas (picture) somewhere in the gallery. In the paper we present an evaluation of the augmented colouring aspect of the proposed game with nine K-6 children