EVOLUTION OF THE PINATUBO VOLCANIC CLOUD OVER HAMPTON, VIRGINIA

A ground-based lidar system at NASA Langley Research Center in Hampton ; Virginia, has monitored the stratospheric aerosol vertical distribut ion and loading since 1974. The eruption of Mt. Pinatubo in June 1991 produced the largest enhancement of stratospheric aerosol loading ever observed by lidar over this mid-latitude location. Low altitude layer s (<20 km) were the first to arrive over Hampton in early August, the result of transport associated with a tropospheric anticyclonic cell o ver North America. The maximum peak scattering ratio, 34 at 22.4 km, a nd the maximum stratospheric integrated backscatter of 0.0053 sr(-1), both at 694 nm, observed since the eruption were measured on February 20, 1992. After decreasing during the spring and summer of 1992, the a erosol burden increased significantly during the winter of 1992-3, evi dence of poleward winter transport from the equatorial reservoir. Over the period from February 1992 to February 1994, the stratospheric aer osol loading decreased with an average 1/e decay time of 10.1 months. The vertical distribution, intensity, and transport of Pinatubo aeroso ls over Hampton, Virginia, are described in detail and compared with s imilar measurements after El Chichon.