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

摘要

This paper gives an overview of August 2004 through February 2010 upper tropospheric (UT) water vapor (H_2O) 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 H_2O and IWC at 215 to 147 hPa are associated with areas of deep convection. They exhibit good (within -15%) agreement in IWC at these altitudes, but GEOS-5 H_2O is -50% (215 hPa) 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 H_2O and IWC, but GEOS-5 produces a weaker intertropical convergence zone than MLS. MLS and GEO5-5 both show spatial anticorrelation between IWC and H_2Oat 100 hPa, where low H_2O is associated with low temperatures in regions of tropical convection. At 100 hPa, GEOS-5 produces 50% less IWC and 15% less H_2O in the tropics, and -20% more H_2O in the extratropics, than does M LS. Behavior of the 100 hPa H_2O is consistent with it being controlled by temperature. The seasonal cycle in the vertical transport of tropical mean H_2O from -147 hPa to -10 hPa appears much stronger in MLS than in GEOS-5. The UT IWC and H_2O interannual variations, from both MLS and GEOS-5, show clear imprints of the EI Nino-Southem Oscillation.