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[1] The Earth Observing System (EOS) Microwave Limb Sounder (MLS) aboard the Aura satellite has provided essentially daily global measurements of ozone (O 3 ) profiles from the upper troposphere to the upper mesosphere since August of 2004. This paper focuses on validation of the MLS stratospheric standard ozone product and its uncertainties, as obtained from the 240 GHz radiometer measurements, with a few results concerning mesospheric ozone. We compare average differences and scatter from matched MLS version 2.2 profiles and coincident ozone profiles from other satellite instruments, as well as from aircraft lidar measurements taken during Aura Validation Experiment (AVE) campaigns. Ozone comparisons are also made between MLS and balloon-borne remote and in situ sensors. We provide a detailed characterization of random and systematic uncertainties for MLS ozone. We typically find better agreement in the comparisons using MLS version 2.2 ozone than the version 1.5 data. The agreement and the MLS uncertainty estimates in the stratosphere are often of the order of 5%, with values closer to 10% (and occasionally 20%) at the lowest stratospheric altitudes, where small positive MLS biases can be found. There is very good agreement in the latitudinal distributions obtained from MLS and from coincident profiles from other satellite instruments, as well as from aircraft lidar data along the MLS track.

During boreal summer, much of the water vapor and CO entering the global tropical stratosphere is transported over the Asian monsoon͞Tibetan Plateau (TP) region. Studies have suggested that most of this transport is carried out either by tropical convection over the South Asian monsoon region or by extratropical convection over southern China. By using measurements from the newly available National Aeronautics and Space Administration Aura Microwave Limb Sounder, along with observations from the Aqua and Tropical Rainfall-Measuring Mission satellites, we establish that the TP provides the main pathway for cross-tropopause transport in this region. Tropospheric moist convection driven by elevated surface heating over the TP is deeper and detrains more water vapor, CO, and ice at the tropopause than over the monsoon area. Warmer tropopause temperatures and slower-falling, smaller cirrus cloud particles in less saturated ambient air at the tropopause also allow more water vapor to travel into the lower stratosphere over the TP, effectively short-circuiting the slower ascent of water vapor across the cold tropical tropopause over the monsoon area. Air that is high in water vapor and CO over the Asian monsoon͞TP region enters the lower stratosphere primarily over the TP, and it is then transported toward the Asian monsoon area and disperses into the large-scale upward motion of the global stratospheric circulation. Thus, hydration of the global stratosphere could be especially sensitive to changes of convection over the TP.climate ͉ CO ͉ stratosphere water vapor W ater vapor concentrations in the tropical lower stratosphere (LS) are 60% greater in boreal summer than in winter. This seasonal variation not only influences the radiation budget near the local tropopause but also propagates upward and toward the pole with the global stratospheric circulation (1, 2). Numerical simulations suggest that Ϸ75% of the total summer water vapor transport into the global tropical stratosphere may occur over the South Asian monsoon and Tibetan Plateau (TP) regions (3), contributing to Ͼ25% of the water vapor in the middle stratosphere (4).Studies have hypothesized that an increase in crosstropopause transport in the Asian monsoon͞TP region may have contributed to an increasing trend in stratospheric water vapor (5) during the 1980s and 1990s (6, 7). This trend probably increased the global greenhouse forcing (8) and enhanced ozone depletion in the Arctic (9). Any explanation of this trend or future trends would likely need to address how source regions for stratospheric water have changed. Recent studies have revealed high CO in the upper troposphere (UT) over the South Asian monsoon region (10). This CO is produced by biomass or fossil fuel burning, suggesting a human influence on transport of combustion pollutants and, perhaps, water vapor into the LS (11). Thus, a clarification of the mechanisms of water vapor and CO transport into the LS in this region is an important step toward understanding tropospheric influences on hydrati...

[1] Global satellite observations of ozone and carbon monoxide from the Microwave Limb Sounder (MLS) on the EOS Aura spacecraft are discussed with emphasis on those observations in the 215-100 hPa region (the upper troposphere and lower stratosphere). The precision, resolution and accuracy of the data produced by the MLS ''version 2.2'' processing algorithms are discussed and quantified. O 3 accuracy is estimated at $40 ppbv +5% ($20 ppbv +20% at 215 hPa) while the CO accuracy is estimated at $30 ppbv +30% for pressures of 147 hPa and less. Comparisons with expectations and other observations show good agreements for the O 3 product, generally consistent with the systematic errors quoted above. In the case of CO, a persistent factor of $2 high bias is seen at 215 hPa. However, the morphology is shown to be realistic, consistent with raw MLS radiance data, and useful for scientific study. The MLS CO data at higher altitudes are shown to be consistent with other observations.

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