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Cirrus in the tropical tropopause transition layer: association with planetary-scale waves and the Madden-Julian Oscillation

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Thursday, 27 January 2011
Cirrus in the tropical tropopause transition layer: association with planetary-scale waves and the Madden-Julian Oscillation
Washington State Convention Center
Katrina S. Virts, University of Washington, Seattle, WA; and J. M. Wallace

Cloud boundaries identified during the first three years of data from the CALIPSO satellite-based lidar are used to investigate the relationship between cirrus within the tropical tropopause transition layer (TTL) and both their planetary-scale environment and the Madden-Julian Oscillation (MJO). TTL cirrus are significantly related to the large-scale ascent associated with planetary wave activity within the TTL -- specifically, they are well correlated with temperature and wind perturbations within the TTL that resemble convectively-induced, mixed Kelvin-Rossby wave solutions -- but are not significantly related to nearby convective activity. During the evolution of the MJO, a TTL cirrus signature which resembles a Kelvin-Rossby wave solution is observed over the western Pacific warm pool region; this signature is centered ~20-30 degrees of longitude to the east of the associated convection. A cirrus maximum is also observed over equatorial South America and Africa during the latter stages of a normal MJO cycle. Tropical mean TTL cirrus fraction is modulated by the MJO, with ~120% more TTL cirrus equatorward of 10 degrees latitude when the convective maximum enters the Pacific than when the MJO is in its beginning stages.