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 2003.

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 O3 “Events” at Tololo

D 08 D 10

D 12

D 09

D 11 D13

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

Lat

itud

e

Longitude

Lat

itud

e Lat

itud

e

Longitude

Rapanui Backward Rapanui Forward

Tololo ForwardTololo Backward

Rapanui, trajectories for November 9 and 12

Longitude

Lat

itude

Backward

Forward

Tololo, trajectories for November 9 and 12

Backward

Forward

LongitudeL

atitu

de

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.

RAPANUIThe air collected at this site typically originates in the MBL west of Rapanui.