Observations of deep convective influence on stratospheric water vapor and its isotopic composition

In situ observations of H 2 O and HDO in the midlatitude stratosphere are used to evaluate the role of convection in determining the stratospheric water budget. The observations show that water vapor in the overworld stratosphere (potential temperature > 380 K) is isotopically heavier than expected. Measurements in an airmass with anomalously high concentrations of water vapor show isotopic water signatures that are characteristic of evaporated ice lofted from the troposphere during convective storms. Observed H 2 O and HDO concentrations in the plume of enhanced water and in the background stratosphere suggest that extratropical convection can account for a significant fraction of the observed water vapor in the summertime overworld stratosphere above the mid‐North American continent.