Assessment of the SAGE II version 6.2 water vapor data set through intercomparison with ATMOS/ATLAS-3 measurements

Abstract

Based on the intercomparisons with ATMOS/ATLAS-3 measurements, the SAGE II (Stratospheric Aerosol and Gas Experiment II) version 6.2 water vapor profiles exhibit significant improvements over earlier versions of data products. A previously reported SAGE II dry bias in the lower stratosphere relative to ATMOS version 3 data set has been effectively eliminated. In the new version, the agreement between SAGE II and ATMOS is generally within 15% with no systematic biases throughout the entire altitude range of 12 km to 40 km. The only exception is the situation for which 1020-nm aerosol extinctions exceed the recommended upper limit of 3 × 10-4 km-1. Based on the comparisons, the reported uncertainties for SAGE II water vapor mixing ratios appear to be over-estimated by a factor of 2 to 3 for the lower stratosphere. Copyright 2004 by the American Geophysical Union.