AEROSOL OPTICAL-PROPERTIES AT MAUNA-LOA OBSERVATORY - LONG-RANGE TRANSPORT FROM KUWAIT

Aerosol light absorption has been measured continuously at Mauna Loa Observatory, Hawaii (MLO), since April 1990. During the spring of 1991, after oil wells were fired in Kuwait, there was speculation among scientists concerning long-range transport of smoke particles and its possible effect on global climate. The MLO light absorption record from April 1990 to June 1991 shows low values in the 0.1-1 x 10(-7) m-1 range in the summer of 1990, and an increased baseline level of about 2-4 x 10(-7) m-1 with numerous superimposed events in the 5-10 x 10(-7) m-1 range in the spring of 1991. These levels correspond to black carbon (BC) concentrations of 1-10, 20-40, and 50-100 ng m-3, respectively, under the assumption that BC is the dominant light absorbing species and has a specific absorption of 10 m2 g-1. Large-scale 500-hPa trajectories calculated backwards from MLO sometimes show direct transport paths from China and Kuwait to Hawaii that coincide with the black carbon events. These measurements set an upper limit on the possible contribution of Kuwaiti black carbon to the background troposphere near MLO during periods of rapid transport. The aerosol observed at MLO is expected to cause a net cooling of the atmosphere.