A high quality reprocessed GPS integrated water vapour dataset for atmospheric process studies, model evaluation and assimilation

Data from the 970 ground-based GPS receivers in France, Italy, Spain, Portugal and Morocco have been reprocessed in a consistent way using GIPSY-OASIS II software for the period from 1st September 2012 to 31 March 2013 which encompasses the Special Observation Periods (SOP 1 and 2) of the HYMEX project. The reprocessed GPS tropospheric delay data set is screened and validated, and used to evaluate the operational GPS data assimilated into numerical weather prediction models. The mean and standard deviation of delay differences reach 2-3 mm (mean) and 4-8 mm (standard deviation). Significant bias reduction is thus expected from a reanalysis ingesting the reprocessed delay data. Various methods and auxiliary data (surface pressure and weighted mean temperature) are investigated for the conversion of delay data have been into integrated water vapour. The final integrated water vapour dataset is used to evaluate radiosonde humidity observations and mesoscale model simulations, and to study the spatial and temporal distribution with a focus on heavy precipitation events in the north-western Mediterranean area during the HYMEX SOP1 and 2.