Past and future changes of moisture transports into the convective areas of the tropical atmospheric circulation

Changing movements of moisture laden air alter precipitation patterns and thus influence regional water availability. To estimate changing moisture transports into the tropical regions of convection (ASC, referring to ascending vertical air movement) we used high time and space resolution wind and humidity data from ERA-interim and ECHAM5 for the recent past and for an assumed anthropogenic warmed future. Unlike most other studies we do not base our investigations on time and space averages, but on instantaneous variables which are physically more consistent. For the past we found a statistically significant increase of transported moisture into ASC at the lower levels, and also a statistically significant increase of transported moisture out of ASC at the mid levels. Nearly stable values of atmospheric humidity indicate an intensification of contribution of the wind circulation. Since strengthening of the in- and outflow neutralize each other, at least to some extent, the signal in the total budget only is weakly positive. For an assumed IPCC-AR4 A1B future we also find in intensification of the hydrological cycle, higher inward and outward moisture transports towards the end of a simulated 21st century climate. This intensification is found to be due to the higher amount of water in the atmosphere, while the contribution of weakening wind counteracts this response marginally. The highest increase is projected for events of the highest percentiles in terms of moisture transport amount (commonly referred to as extreme events). In addition we used the IPCC-AR4 data to estimate changes of moisture transported from oceanic to land areas.