HYSPLIT model results for 25 October 2011.

<p>Left: surface concentration of ¹³¹I at 0 UTC, 25 October 2011; right: 24-hour trajectories started hourly between 9–15 UTC, 24 November 2011. The locations of Prague and Budapest are marked. Simulated with the HYSPLIT model [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172312#pone.0172312.ref010" target="_blank">10</a>] using the GFS meteorological data.</p

WRF-HYSPLIT model results.

<p>Surface concentration of ¹³¹I at 0 UTC, 5 November 2011 modeled with the HYSPLIT model [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172312#pone.0172312.ref010" target="_blank">10</a>] using the WRF meteorological data. The locations of Prague and Budapest are marked. Northward transport was caused by higher level winds.</p

The contradiction between dispersion and trajectory results can be explained with the large vertical wind shear.

<p>Top: surface concentration of ¹³¹I at 0 and 6 UTC, 5 November 2011; bottom: 24-hour trajectories started from 40 m height hourly between 9–15 UTC, 4 November 2011. The locations of Prague and Budapest are marked. Modeled with the HYSPLIT model [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0172312#pone.0172312.ref010" target="_blank">10</a>] using the GFS meteorological data.</p

Reported detection in Prague on 4–5 November was correctly predicted only by the WRF-Chem model.

<p>Modeled surface concentration of ¹³¹I at 0 UTC, 5 November 2011 with a Lagrangian (RAPTOR) and an online integrated Eulerian model (WRF-Chem) using the WRF meteorological data. The cities of Prague and Budapest are outlined.</p

Visible satellite image at 12 UTC, 4 November 2011.

<p>Fog and stratus clouds covering the Czech Republic indicates the presence of a strong low-level inversion. Wind below the inversion layer (950 hPa, white arrows) differs significantly from the wind above the inversion layer (850 hPa, orange arrows). Red dots show the locations of Prague and Budapest. Data obtained from EUMETSAT and GFS.</p

Modeled surface concentration of ¹³¹I 84 hours after the beginning of emission.

<p>Top: 21 UTC, 20 October 2011; bottom: 21 UTC, 3 November 2011; left: RAPTOR model results; right: HYSPLIT model results. Blue dot: source location (Budapest). Red dots: detection sites (Dubna and Stockholm).</p

Surface wind observations at the time of the release, 12 UTC, 4 November 2011.

<p>Surface wind transporting the plume from Budapest to Prague is well observable. Data obtained from SYNOP reports of the National Weather Services of Austria, Slovakia, the Czech Republic and Hungary.</p

Reported detection in Prague on 24–25 October was correctly predicted by the models.

<p>Modeled surface concentration of ¹³¹I at 0 UTC, 25 October 2011 with a Lagrangian (RAPTOR) and an online integrated Eulerian model (WRF-Chem) using the WRF meteorological data. The cities of Prague and Budapest are outlined.</p