The relationship between daily European precipitation and measures of atmospheric water vapour transport

In this study we investigate the relationship between daily European precipitation totals and different measures of atmospheric water vapour transport during both the winter and summer seasons. Using gridded gauge-based precipitation estimates across Europe and the Modern-Era Retrospective Analysis for Research and Applications (MERRA) reanalysis as the source of the water vapour transport, we examine what combination of predictor variables (related to wind and humidity at different levels and total column water) explains the most precipitation variability. Results show that stronger relationships occur in the winter than in the summer, and that the best linear models for explaining the daily rainfall variability contain the zonal and meridional water vapour transport components as predictors [e.g. winter precipitation in the European Alps (western Norway) has R² values of about 0.5 (0.45)]. Precipitation regions most related to zonal and meridional moisture fluxes are also discussed. We also show that models requiring just three fields, namely the integrated water vapour, and the 850-hPa zonal and meridional winds, are able to explain the precipitation variability in Europe well. Given the computational and initial storage requirements in calculating water vapour transport integrated over the atmospheric column (in particular for climate change projections), it would be possible to use these three fields in assessments of future water vapour fluxes over Europe, in turn allowing inferences to be made on future rainfall and flood events.