资源环境科技发展态势分析平台

Convectively injected water vapor (H2O) in the North American (NA) summer lowermost stratosphere results in significant outliers in the 100‐hPa H₂O measurements from the Aura Microwave Limb Sounder (MLS). MLS statistics from 15 years confirm that the NA region contains over 60% of global 100‐hPa H₂O> 12 ppmv, despite having only ~ 1.8% of all MLS observations. A profile sampled in August 2019 stands out, with H₂O = 26.3 ppmv, far exceeding the prior record and the median ~ 4.5 ppmv abundance in NA. This particular outlier is associated with a large overshooting convective event (OCE) that spanned multiple US states and persisted for several hours. Colocation of the MLS data over NA with cloud observations from Aqua's Moderate Resolution Imaging Spectroradiometer reveals the unique character of this case, as only 2.3% of MLS profiles are as close to an OCE and only 0.024% of OCEs cover as large an area within a 500 km perimeter of a profile.