Trajectories analyses for the campaign of November 2003 O. Cuevas*, M. Rojas** and R. Alcafuz*** *Universidad de Valparaíso, Centro de Modelamiento Matematico Universidad de Chile ** Departamento de Geofísica, Universidad de Chile *** Dirección Meteorológica de Chile Stratosphere – Troposphere Exchange:

We want to assess the origin/destiny of the air masses affecting Rapanui (27º S, 109ºW, 51 m.a.s.l.) and Tololo (30ºS, 70ºW, 2220 m.a.s.l.) to interpret the soundings performed at theses sites during the campaign of November For that purpose, we use 3-D meteorological fields to calculate forward an backward trajectories for Rapanui and Tololo.

MM5 Set up The Penn State-NCAR fifth generation Mesoescale Model (MM5), fed with reanalisys field as IC and BC has been used. In this simulations the upper boundary was lifted up to 30 hPa in order to include the tropopause region. Trajectories over Rapanui Trajectories over Tololo

250 Hpa 500 Hpa Synoptic Conditions and O 3 “Events” at Tololo

D 08D 10 D 12 D 09 D 11D13 Synoptic conditions, STJ (m/s), 250 hPa

Method RIP (Read/Interpolate/Plot) RIP is a Fortran program that invokes NCAR Graphics routines for the purpose of visualizing output from gridded meteorological field (MM5). Backward (Forward) trajectories were calculated for 48 hours periods starting on November 15 (November 7) 2003.The calculation of trajectories was made with RIP.

Results Trajectories for Rapanui Trajectories for Tololo Latitud e Longitude Latitud e Longitude

Rapanui Backward Rapanui Forward Tololo Forward Tololo Backward

Rapanui, trajectories for November 9 and 12 Longitude Latitude Backward Forward

Tololo, trajectories for November 9 and 12 Backward Forward Longitude Latitude

Conclusions TOLOLO ● At this site, the deflection of the upper westerlies by the Andes and the subsidence induced by the subtropical high are and the predominant features. Thus, the air collected at Tololo typically arrives from the NW, originating at 4-5 km height. ● In connection with the deep trough that approched the area by November 12, air masses originating in the marine boundary layer (MBL) to the SW of the site could be distinguished. RAPANUI The air collected at this site typically originates in the MBL west of Rapanui.