On time at 0700 UTC (9 o’clock local time in Germany) in a cloudy but dry Bavarian morning, HALO took to the skies and headed south-west for its first interim destination Sal on Cape Verde. The flight today, estimated to take 6.5 hours, marks the beginning of the scientific experiments where all instruments are operational.

The transfer flights to Rio Grande with stops in Sal and Buenos Aires are also used for intense measurements. Besides the central themes of the SouthTRAC campaign, we are interested in stratosphere-troposphere exchange (STE) at the subtropical jets, convective outflow, traces of stratospheric plumes of recent volcanic eruptions, interhemispheric differences, and gravity waves excited by strong wind shear and in the lee of the Andes.