Five year (2004-2009) observations of upper tropospheric water vapor and cloud ice from MLS and comparisons with GEOS-5 analyses

This paper gives an overview of August 2004 through February 2010 upper tropospheric (UT) water vapor (H2O) and ice water content (IWC) from the Aura Microwave Limb Sounder (MLS) and comparisons with outputs from the NASA Goddard Earth Observing System Version 5 (GEOS-5) data assimilation system. Both MLS and GEOS-5 show that high values of H2O and IWC at 215 to 147 hPa are associated with areas of deep convection. They exhibit good (within similar to 15%) agreement in IWC at these altitudes, but GEOS-5 H2O is similar to 50% (215 hPa) to similar to 30% (147 hPa) larger than MLS values, possibly due to higher temperatures in the data assimilation system at these altitudes. A seasonally migrating band of tropical deep convection is clearly evident in both the MLS and GEOS-5 UT H2O and IWC, but GEOS-5 produces a weaker intertropical convergence zone than MLS. MLS and GEOS-5 both show spatial anticorrelation between IWC and H2O at 100 hPa, where low H2O is associated with low temperatures in regions of tropical convection. At 100 hPa, GEOS-5 produces 50% less IWC and 15% less H2O in the tropics, and similar to 20% more H2O in the extratropics, than does MLS. Behavior of the 100 hPa H2O is consistent with it being controlled by temperature. The seasonal cycle in the vertical transport of tropical mean H2O from similar to 147 hPa to similar to 10 hPa appears much stronger in MLS than in GEOS-5. The UT IWC and H2O interannual variations, from both MLS and GEOS-5, show clear imprints of the El Nino-Southern Oscillation.