Urban influence on nighttime airflow estimated from tetroon flights

Abstract

Constant- volume balloon (tetroon) flights tracked by radar across Columbus, Ohio, in March 1969, illustrate the effect of a city on the nighttime airflow at heights of 100- 200 m. On the average, the urban influence on wind direction is small at a height of 100 m, but an anticyclonic turning of 10 deg is observed at 300 m. The anticyclonic turning is greater under inversion than under lapse conditions and greater after midnight than before. The decrease in wind speed across the city averages nearly 20% of the upwind speed under lapse conditions but it very small under inversion conditions.