Jens Havskov Sørensen

Airborne spread of foot-and-mouth disease - model intercomparison.

Foot-and-mouth disease virus (FMDV) spreads by direct contact between animals, by animal products (milk, meat and semen), by mechanical transfer on people or fomites and by the airborne route, with the relative importance of each mechanism depending on the particular outbreak characteristics. Atmospheric dispersion models have been developed to assess airborne spread of FMDV in a number of countries, including the UK, Denmark, Australia, New Zealand, USA and Canada. These models were compared at a Workshop hosted by the Institute for Animal Health/Met Office in 2008. Each modeller was provided with data relating to the 1967 outbreak of FMD in Hampshire, UK, and asked to predict the spread of FMDV by the airborne route. A number of key issues emerged from the Workshop and subsequent modelling work: (1) in general all models predicted similar directions for livestock at risk, with much of the remaining differences strongly related to differences in the meteorological data used; (2) determination of an accurate sequence of events on the infected premises is highly important, especially if the meteorological conditions vary substantially during the virus emission period; (3) differences in assumptions made about virus release, environmental fate and susceptibility to airborne infection can substantially modify the size and location of the downwind risk area. All of the atmospheric dispersion models compared at the Workshop can be used to assess windborne spread of FMDV and provide scientific advice to those responsible for making control and eradication decisions in the event of an outbreak of disease.

Modelling the atmospheric dispersion of foot-and-mouth disease virus for emergency preparedness

Abstract A model system for simulating airborne spread of foot-and-mouth disease (FMD) is described. The system includes a virus production model and the local- and mesoscale atmospheric dispersion model RIMPUFF linked to the LINCOM local-scale flow model. LINCOM is used to calculate the sub-grid scale flow using as input data from the numerical weather prediction model DMI-HIRLAM. The model system is a part of a real-time decision-support system intended for use by veterinary authorities in case of outbreaks of FMD. Results are presented corresponding to historical outbreaks of the disease.

Pollutant transport schemes integrated in a numerical weather prediction model: model description and verification results

Regional air pollution models are usually off-line coupled with numerical weather prediction models. The present study, however, focuses on on-line coupled modelling, for which the air pollution model is an integral part of the meteorological model. To this purpose, simulations of the first European Tracer Experiment (ETEX), which supplies the best suited verification data for dispersion modelling of a passive tracer, have been performed using versions of the Danish Meteorological Institute High Resolution Limited-Area Model (DMI-HIRLAM). Simulation results have been compared with observed values as well as with results from other models. The operational version of DMI-HIRLAM using well-known basic advection schemes has been tested, showing the need for improvements for air pollution purposes. The fourth-order Bott algorithm for advection has thus been implemented in the semi-Lagrangian version of DMI-HIRLAM. Due to its practically perfect mass conservation properties and its low computational cost, this method turns out to be efficient for simulations of transport of pollutants in the atmosphere. This represents a first effort towards a fully integrated air pollution model, e.g. for forecasting purposes. Copyright

Intrusion of stratospheric ozone to the free troposphere through tropopause folds - a case study

Abstract Simultaneous ozone radiosoundings at Jaegersborg north of Copenhagen, Denmark, and at Gardermoen north of Oslo, Norway, at 12 UTC on 21 March, 1994, both show a pronounced peak of ozone in the free troposphere. A study involving routine radiosoundings as well as analysed numerical weather prediction (NWP) model data shows that a tropopause folding occurred over the Davis Strait and the southern part of Greenland about two days before the radiosoundings. Trajectory calculations performed using the same NWP model data indicate that air parcels corresponding to the observed ozone peaks at Jaegersborg and at Gardermoen have passed trough the tropopause fold thus bringing down ozone rich air from the stratospheric ozone layer to the free troposphere. A quantitative simulation of this transport phenomenon is performed using an atmospheric three-dimensional long-range dispersion model. By fitting the simulated vertical profiles of ozone concentration to the observed profiles, an estimate is obtained of the rate of ozone intrusion through the tropopause fold.

Use of DMI-Hirlam for Operational Dispersion Calculations

During the latest decades there has been a. rapid progress in the ability to forecast weather. This progress has been possible because of the development of advanced numerical weather-prediction (NWP) models running on the most powerful computers available. Especially, there has been progress in the capability to make numerical forecasts in the range from one day to about a week ahead in the Northern Hemisphere which is dominated by the travelling weather systems. On longer time scales, there has been some progress, but severe difficulties are met due to the intrinsic chaotic nature of the atmosphere.

An Operational Real-Time Model Chain for Now- and Forecasting of Radioactive Atmospheric Releases on the Local Scale

A comprehensive atmospheric dispersion modelling system, designed for real-time assessment of nuclear accidental releases from local to European scale, has been established by integrating a number of existing preprocessors, wind, turbulence, and dispersion models together with on-line available meteorology. The resulting dispersion system serves the realtime on-line decision support system for nuclear emergencies RODOS (Ehrhardt 1996; Kelly et al., 1996; Ehrhardt et al., 1997) with a system-integrated atmospheric dispersion module. This module is called met-rodos, Mikkelsen et al. (1997).

Microclimatic temperatures increase the potential for vector-borne disease transmission in the Scandinavian climate

We quantified the difference between the meteorological temperature recorded by the Danish Meteorological Institute (DMI) weather stations and the actual microclimatic temperatures at two or three different heights at six potential insect habitats. We then compared the impact of the hourly temperature on the extrinsic incubation period (EIP) of six pathogens. Finally, we developed a regression model, enabling us to predict the microclimatic temperatures of different habitats based on five standard meteorological parameters readily available from any meteorological institution. Microclimatic habitats were on average 3.5–5 °C warmer than the DMI recorded temperatures during midday and 1–3 °C cooler at midnight. The estimated EIP for five of the six microclimatic habitats was shorter than the estimates based on DMI temperatures for all pathogens studied. The microclimatic temperatures also predicted a longer season for virus development compared to DMI temperatures. Based on DMI data of hourly temperature, solar radiation, wind speed, rain and humidity, we were able to predict the microclimatic temperature of different habitats with an R2 of 0.87–0.96. Using only meteorological temperatures for vector-borne disease transmission models may substantially underestimate both the daily potential for virus development and the duration of the potential transmission season.

Spatiotemporal variation of stable isotopic composition in precipitation: post-condensational effects in a humid area

In the present study, a two year dataset on δ18O and δ2H in precipitation is used to investigate hydrometeorologic controls on the isotopic compositions in a temperate maritime climate. Data was collected in Denmark along a transect of six sampling stations across a landscape with a small topographic gradient and predominant westerly winds. Data showed the local meteoric water line for this region is expressed by the equation δ2H = 7.4δ18O + 5.36‰. A significant trend correlating enriched isotopic values to humidities around 70% during dry season and more depleted isotopic ratios to humidities around 90% during wet season was derived from the dataset. Temperature was found to only influence the isotopic composition in a secondary way, while no significant relationship is obtained for precipitation amount and evapotranspiration. It is suggested that sub-cloud post-condensation exchange strongly influence the isotopic composition at the study site. A simple model of evaporation on falling rain was applied with the aim to reproduce observational data and show the potential influence of changing humidity conditions on precipitation compositions. The rather simple model approach did not fully explain the observational data, but it highlights the drastic isotopic changes from a falling raindrop, that potentially can occur due to its release into a dryer atmosphere. This study shows that regional conditions and especially humidity can alter the isotopic composition in precipitation substantially even in regions without major topographic and hydrometeorologic gradients.

A sensitivity study of the operational surface ozone forecast system “DACFOS”

Abstract The Danish Atmospheric Chemistry FOrecasting System (DACFOS) is a receptor point model based on DMIs transport model using data from the numerical weather prediction model DMI-HIRLAM and employing EMEPs chemistry scheme from the MSC-W oxidant model. Surface ozone forecasts for the summers 1997-98 are verified for two English and two Danish stations, using the statistical parameters suggested by the Technical Working Group on Ozone Forecasting and Data Exchange (TWG-DFO). The forecast skill varies for the two countries, and a relative high positive bias is seen for the English forecasts in comparison with the Danish forecasts. This high positive bias is investigated by a sensitivity study considering cases with different air masses classified by the German Weather Service (DWD). The study shows that the positive bias for England originated from polar and midlatitudinal continental airmasses. These air masses do travel over different emission areas when they arrive to Denmark and England, so the difference in bias could be explained by inaccurate emissions.

Documenting the ‘terroir’ aspects of award-winning Danish conserves: a model for the development of authentic food products

Abstract: An example of the qualities embedded in the foods produced by small companies based on small Danish islands and reflections on the association between the qualities of the products and their geographical origin is presented. This case study discusses how it can be ensured that qualities in the products that can be tasted and documented truly reflect geographical origin, and ways in which authenticity can be guarded and exploited in marketing while at the same time increasing production volume.