Atmospheric stagnation, recirculation and ventilation potential of severalsites in Argentina

Conditions for sta;:nation, recirculation and ventilation potential of the atmosphere were studied in five argentine cities: Resistencia, Cordoba, Bue nos Aires, Mar del Plata and Comodoro Rivadavia, located in different regio ns 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 s peed and direction. The largest stagnation frequency (45% of the time) was observed in Resistencia, located in the northeastern part of the country, i n an area where winds are weak. The least frequency of stagnations (2%) was observed in Comodoro Rivadavia, in the southern region of the country, a r egion dominated by strong westerly winds. Comodoro Rivadavia and Cordoba re gistered the largest frequency of recirculations. Comodoro Rivadavia expose d to sea-land breezes and Cordoba, located on a complex terrain area and ex posed to local circulations, experienced recirculation events during 10% of the time. Good atmospheric ventilation occurs when a high value of wind ru n and a low value of the recirculation factor are observed and it can be as sociated 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 Resistenc ia. In general, stagnation was more frequently observed during autumn and w inter, recirculation during spring and summer and good ventilation conditio ns occurred during spring. (C) 1999 Elsevier Science B.V. All rights reserv ed.