Dry layers in the tropical troposphere observed during CONTRAST and global behavior from GFS analyses

Aircraft measurements included over 80 vertical profiles from the boundary layer to the upper troposphere (~15 km). A large fraction of these profiles revealed layered structures with very low water vapor (relative humidity <20%) and enhanced ozone, primarily in the lower-middle troposphere (~3–9 km).

Comparing CONTRAST water vapor measurements with co-located profiles from National Centers for Environmental Prediction Global Forecast System (GFS) analyses, we find good agreement for dry layers, including profile-by-profile comparisons and statistical behavior. We then utilize GFS data to evaluate the frequency of occurrence and 3-D structure of dry layers for the CONTRAST period to provide perspective to the campaign measurements and evaluate the global climatological behavior based on a longer record.