Open AccessStratospheric aerosols observed by lidar over northern Greenland in the aftermath of the Pinatubo eruption
Author(s) -
di Sarra A.,
Bernardini L.,
Cacciani M.,
Fiocco G.,
Fuà D.
Publication year - 1998
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/98jd00901
Subject(s) - stratosphere , aerosol , troposphere , atmospheric sciences , quasi biennial oscillation , tropopause , environmental science , volcano , climatology , vulcanian eruption , geology , meteorology , physics , seismology
Lidar observations were carried out from Thule (76.5°N, 68.8°W), Greenland, during the period September 1991 to February 1996. The measurements were carried out with relative continuity throughout the solar year, with the exception of the summer 1992. A total of over 300 profiles of the stratospheric aerosol backscattering and depolarization were obtained. The buildup and decay of the volcanic aerosols, originated from the eruption of Mount Pinatubo (June 1991, Philippines), were followed in detail. Maxima of the backscatter ratio, around 6, were recorded in March 1992. The aerosol decay, mainly controlled by gravitational sedimentation and stratosphere‐troposphere exchange, shows a strong modulation induced by dynamical phenomena: an annual oscillation of the aerosol integrated backscattering, with a winter maximum at altitudes below 20 km, distinctly appears. Subsidence during winter and, possibly, upward motion during summer lead to a consistently different winter‐to‐summer aerosol vertical distribution. Discontinuities in the evolution of the aerosol backscattering may be related to the influence of the quasi‐biennial oscillation (QBO) on the poleward transport and on the mean diabatic circulation. The QBO appears also to affect the stratosphere‐troposphere exchange during winter. By fitting the decreasing phase of the volcanic aerosol integrated backscattering with an analytical expression given by an exponential decrease and an annual oscillation, an e ‐folding time of approximately 9.4 months is derived. The e ‐folding time varies however with time and depends on altitude. A distinct transition occurs in early summer 1994, with a fast decrease of the aerosol load below 20 km. The observation of backscattering values larger than in the pre‐Pinatubo period still in early 1996 above 20 km seems to be consistent with modifications of the particle size distribution at these altitudes. Upper limit estimates for the diabatic descent in and outside the polar vortex could also be derived from the lidar observations in the winter months.