Atmospheric stagnation, recirculation and ventilation potential of several sites in Argentina

Conditions for stagnation, recirculation and ventilation potential of the atmosphere were studied in five argentine cities: Resistencia, Cordoba, Buenos Aires, Mar del Plata and Comodoro ́ Rivadavia, located in different regions of the country. Wind run and recirculation factors were calculated for a 24-h transport time using 2 years of hourly surface measurements of wind speed Ž . and direction. The largest stagnation frequency 45% of the time was observed in Resistencia, located in the northeastern part of the country, in an area where winds are weak. The least Ž . frequency of stagnations 2% was observed in Comodoro Rivadavia, in the southern region of the country, a region dominated by strong westerly winds. Comodoro Rivadavia and Cordoba ́ registered the largest frequency of recirculations. Comodoro Rivadavia exposed to sea–land breezes and Cordoba, located on a complex terrain area and exposed to local circulations, ́ experienced recirculation events during 10% of the time. Good atmospheric ventilation occurs when a high value of wind run and a low value of the recirculation factor are observed and it can be associated with the atmosphere’s capacity to replace polluted air with clean air. Ventilation events occurred 58% of the time at Comodoro Rivadavia, 52% at Mar del Plata, 40% at Buenos Aires, 35% at Cordoba and 18% at Resistencia. In general, stagnation was more frequently ́ observed during autumn and winter, recirculation during spring and summer and good ventilation conditions occurred during spring. q 1999 Elsevier Science B.V. All rights reserved.