The field experiment was designed to describe the diurnal cycle of the winds about Arequipa and also the diurnal variation of the lower tropospheric temperature. The latter is needed to estimate the potential for air pollution episodes. The former (the windfield) is needed to describe the effectiveness of horizontal transport of pollutants out of (or into) the city’s vicinity.

Pilot balloons were chose to measure the wind field because of their low cost of operation and because the generally cloud-free conditions around Arequipa, which allow for tracking of the balloons to high levels. Three sites were established because we anticipated that measurements at a site in the city would not be the same as sites away from the higher mountains just north of Arequipa.

Observations were made every 2 hours and every 3.5 hrs at night, mostly limited by the available balloons, gas, and lights for tracking balloons at night. The three sites chosen formed a triangle of approximately 70km between stations (Fig. 1). The sites were generally flat, except for La Pampilla, which was on the gentle lower slope of Volcan Misti.
The temperature profiles (and moisture profiles) were obtained through 3 radiosonde launches and numerous 900m-deep soundings carried out with a tethersonde.