How is stratospheric water vapour affected by climate change, and which processes are responsible? 

Gabriele Stiller (PI), Mark Weber, Patrick Jöckel, Martin Dameris, Ulrike Langematz, Hauke Schmidt, Christoph Brühl

Phase I:

SHARP-WV analyses observational data sets from the satellite instruments MIPAS and SCIAMACHY, merged with earlier satellite data records as HALOE or SAGE, and from long-term simulations with Chemistry-Climate Models in order to improve the understanding of past variations and trends in stratospheric water vapour, and to assess the future evolution of the stratospheric water vapour budget in a changing climate. The satellite observations are used to study the stratospheric water vapour distribution and its temporal and spatial anomalies as well as changes on a decadal scale. Simulations from Chemistry-Climate Models and an Earth System Model are compared to the observational data sets regarding the past evolution of stratospheric water vapour, with emphasis on specific events like the circulation change around the year 2000, or volcanic and El Niño-Southern Oscillation impacts.

 

Seasonal variation of tropical water vapour from MIPAS observations of July 2002 to March 2004. The signal with low anomalies in winter and high anomalies in summer travels upwards from the tropopause and is known as the tape recorder signal.

 

Phase II:

Observational data sets of water vapour from MIPAS and SCIAMACHY and HDO from MIPAS will be extended and further improved in data quality. An “all-satellite” data set containing data of SAGE, HALOE, SMR, MLS, MIPAS and SCIAMACHY and covering 30 years from 1984 to 2014 will be generated by appropriate data merging. The MIPAS and SCIAMACHY data record will be analyzed regarding the anomalies of the time series (tape recorder, monsoon systems), potential trends, and correlations to other atmospheric quantities like tropical tropopause temperature. Similar analysis will be performed with improved transient and sensitivity model runs available within SHARP. H₂O modelling will be included in the Lagrangian version of EMAC, and case process studies will be performed to analyze the water vapour transport into the stratosphere. The modeled H₂O fields will be compared to H₂O data sets made available from MIPAS. For ECHAM5/MESSy, a higher resolved version not producing the cold and dry bias in the tropopause will be sought for. The CMIP5 Simulations of MPI-M will be analyzed regarding water vapour, and internal variability will be compared to climate change signals. The role of methane for the stratospheric water vapour budget will be re-assessed in the light of recent changes in methane growth, both from the observational and model data side.