EFFECT OF SOLAR-RADIATION ON SURFACE OZONE IN CAIRO

Measurements of surface ozone content over an urban area in Cairo were made during a year (May 1989-April 1990), while solar radiation at the same area was measured. Half-hourly surface ozone concentrations were recorded using Dasibi ozone monitor. Solar radiation measurements used were data from Solar Energy Research Department. Surface ozone concentrations recorded in the area had reached 140 ppb smog level during summer, especially around noon, at which time solar radiation intensity was maximum. During winter, even at around noon of cloudy or rainy days, surface ozone concentrations reached 20 or 10 ppb, respectively. High and low concentrations of ozone are discussed and compared with that recommended by WHO expert committee regarding the daily cycle of ozone concentration; also the solar radiation measurements and the photochemical reactions are expected in that area.