Can lightning observations be used as an indicator of upper-tropospheric water vapor variability?

Lightning activity in thunderstorms is closely related to the intensity of vertical updrafts in deep convective clouds that also transport large amounts of moisture into the upper troposphere. Small changes in the amount of upper-tropospheric water vapor (UTWV) can have major implications for the Earth's climate. New evidence is presented showing a strong connection between the daily variability of tropical lightning activity and daily upper-tropospheric water vapor concentrations from the NCEP-NCAR reanalysis. Our results over the African continent show that the NCEP upper-tropospheric water vapor peaks one day after intense lightning activity in the Tropics. Given the many caveats related to the NCEP UTWV product over Africa, these results need to be interpreted with caution. However, since global lightning activity can be monitored from a few ground stations around the world via the Schumann resonances, we suggest the possible use of continuous lightning observations for studying the daily variability of upper-tropospheric water vapor. Whether lightning is related to UTWV on other spatial and temporal scales needs further investigation.