Indication of water vapor transport into the lower stratosphere above midlatitude convective storms: Meteosat Second Generation satellite observations and radiative transfer model simulations

Abstract

Past studies using a variety of satellite instruments have demonstrated the possibility of detecting lower stratospheric water vapor against a cold background of deep convective storm tops. The method is based on the brightness temperature difference (BTD) between the water vapor absorption and infrared window bands, assuming a thermal inversion above the cloud top level. This paper confirms the earlier studies, documenting positive BTD values between the 6.2 μm and 10.8 μm bands in Meteosat Second Generation (MSG) Spinning Enhanced Visible and InfraRed Imager (SEVIRI) imagery above tops of deep convective storms over Europe. The observed positive BTD values for a case from 28 June 2005 are compared to calculations from a radiative transfer model, and possible reasons for their existence are discussed. A localized increase in positive BTD is observed at the later stages of storm evolution, and this increase is likely a signal of water vapor being transported by this particular storm from the troposphere into the lower stratosphere.