Tuesday, 11 February 2003
Calibration of GOES water vapor spatial gradients with tropopause folding events
This work examines tropopause folding events and their detection in GOES water vapor channel imagery. An extensive dataset of in-flight ozone lidar from the Tropospheric Ozone Production about the Spring Equinox (TOPSE) provides a number of tropopause fold observations from the period of February to May, 2000. Previous observations showed that these tropopause folds coincided with strong gradients in satellite-derived water vapor, because of the sensitivity of the GOES water vapor channel to the tropopause level. The TOPSE dataset demonstrates that all spatial gradients in GOES-derived water vapor above a given threshold gradient coincide with lidar-observed folding signatures. Using this relationship, the spatial gradients in the GOES-derived water vapor imagery are calibrated to indicate the distribution of tropopause folding within the GOES viewing domain north of the subtropics. These results show that the volume of stratospheric air folded into tropospheric levels is significantly greater, and spread over more area, than indicated by chemical transport models. The global-scale, observation-based nature of these results presents both a unique and a compelling contribution to the current base of knowledge of stratosphere-troposphere exchange.