BARBADOS

Period of Record

Trends

The tropical Northern Hemisphere site for the ALE/GAGE program is located at Ragged Point, on the east coast of Barbados ~15 m from the ocean and 18 m above mean sea level. The site is operated under the supervision of P.G. Simmonds of the University of Bristol. Ragged Point is under the influence of easterly winds and generally receives unpolluted oceanic air, except during certain periods of calm conditions when pollutants from the populated inland regions of Barbados reach the site. Measurements at the site began in July 1978 and continued as part of ALE through April 1986. Beginning in August 1985, measurements were also collected as part of GAGE. After the termination of ALE, measurements continued at Barbados as part of GAGE through the end of the period of record (November 1991).

The monthly mean mixing ratio of CFC-11 increased from 151.1 parts per trillion (ppt) in July 1978 to 265.1 ppt in December 1991. Meanwhile, the mixing ratio of CFC-12 increased from 279.5 to 506.6 ppt. Cunnold et al. (1994) reported that the average rate of increase of CFC-11 at Barbados was 9.4±0.1 ppt/year for the period July 1978 to June 1988 but dropped to 6.9±0.3 for the period July 1988 to June 1991. Similarly for CFC-12, Cunnold et al. (1994) found that the average rate of increase was 17.6±0.1 ppt/year for the period July 1978 to June 1988 and 15.5±0.5 for the period July 1988 to June 1991. For both CFC-11 and CFC-12, these trends are highly significant (P < 0.0001). Prinn et al. (1983) found a small amplitude cycle in CFC-12 at this site, with a peak in late summer; however, the daily CFC-12 variability was also highest during this season. The data for CFC-11 show no evidence of any significant periodicity.

The time series of the monthly mean mixing ratios of N₂O is somewhat more irregular. The values nevertheless show a highly significant (P < 0.0001) trend. The monthly mixing ratio increased from 296.6 parts per billion (ppb) in July 1978 to 310.5 ppb in December 1991. For the 10-year period July 1978 to June 1988, Prinn et al. (1990) calculated that the mixing ratio of N₂O at Barbados increased by an average of 0.94±0.06 ppb/year. In addition, the data were found to exhibit a statistically significant quasi-biennial (tau = 2.25 years) oscillation with an amplitude of 0.45 ppb.

Barbados (Ragged Point)
Atlantic Ocean Island Seashore
13° 10' N, 59° 26' W
3 m above MSL

Barbados Mixing Ratios Graph

• Monthly average CFC-11, CFC-12, and N₂O mixing ratios at Barbados