Atmospheric lifetime experiment. 4. Results for CF/sub 2/Cl/sub 2/ based on three years data

Observations of dichlorodifluoromethane obtained several times daily over the period July 1978 to June 1981 at Adrigole, Ireland (52/sup 0/N, 10/sup 0/W), Ragged Point, Barbados (13/sup 0/N, 59/sup 0/W), Point Matatula, American Samoa (14 /sup 0/W, 171/sup 0/W) and Cape Grim, Tasmania (41/sup 0/S, 145/sup 0/E), are reported. Observations at Cape Meares, Oregon (45/sup 0/N, 124/sup 0/W), are also given for the preiod November 1980 to June 1981. On January 1, 1980, the average mixing ratio of dichlorodifluoromethane in the lower troposphere is estimated to have been 285 ppty and to have been increasing at 6.0%/year. The atmospheric lifetime of this compound is estimated from this data by adjusting its destruction rate in a two-dimensional model of the atmosphere so as to provide the best fit to the observations. Assuming destruction of CF/sub 2/Cl/sub 2/ in the stratosphere only, the lifetime estimate for Jaunary 1, 1980, by the inventory technique is 69/sup +36//sub 18/ years. The trend technique principally provides a lower limit to the lifetime of 81 years. The results suggest a need for further assessment of dichlorodifluoromethane release estimates, particularly those from the USSR and eastern Europe.